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Warm hints: The word in this article is about 3000 words and reading time is about 15 minutesSummaryThis article is mainly about space monitoring and location technology of AR&VR equipment. All AR&VR products must have accurate spatial monitoring and positioning capabilities in order to achieve a full range of head， hand interactions in order to provide users with a more realistic virtual experience. CoreResearch on space monitoring and location technology of AR&VR equipmentPurposeIntroduce space monitoring and location technology of AR&VR equipmentProductAR&VR EquipmentCategoryElectronic productsApplicationsAR&VR technologyTechnologyInside-out space monitoring and positioning and outside-in space monitoring and positioning     Catalogs CatalogsI、Current Status of AR&VR ProductsV、 PC VRII、Cardboard productsVI、Space positioning technology categoryIII、Head motion controlled all-in-one            machine1. Inside-out space monitoring and positioning technologyIV、 AIO machine with space monitoring and positioning2. Outside-in space monitoring and positioning technology  Introduction I、Current Status of AR&VR ProductsThere are many AR&VR products already on the market. The price varies from Cardboards to Hololens, and the user experience varies greatly. First of all, VR products can be divided into the following categories: cardboard products, one-touch control integrated machine, AIO machine with space monitoring and positioning, PC VR.  DetailII、Cardboard productsCardboard productsThis kind of product is the simplest VR product. It comes from Google's carton VR box. Simply, it uses two convex lenses to project the contents of the mobile phone into screens. It uses the IMU inside the phone to judge the user's head movement to adjust the movement direction of the VR display content. This kind of product began to ship a large number of domestic white cards in 2015, but the overall effect of VR depends on the configuration of the mobile phone and the quality of the optical lens. It is only an entry-level VR experience product.The first generation VR products of game companies and some domestic video content are basically in this form. The most representative is the Storm Box, with a BT control handle for menu selection. The emergence of this type of product has indeed played a big role in the promotion of the entire VR industry, but its drawbacks are also very obvious. The Cardboard-style VR device ushered in a particularly big opportunity in 2016, that is, Google proposed Daydream VR. Google wants to enhance the VR Cardboard users’ experience, and hopes to be able to dominate the entire VR ecosystem in 2016. The Daydream mobile phone Pixel, Pixel XL and Daydream Viewer wearing the Cardboard were released in the year, and also equipped with a built-in IMU remote control handle. According to Google's requirements for VR device user experience, it must reach a mobile phone with a certain hardware configuration, and with Daydream Viewer running related VR applications, so that users will not be dizzy. Since 2016, with the launch of products such as Huawei P9 and Lenovo MotoZ, there are more and more mobile phones supporting Daydream. It is expected that, in 2017, these products will completely break the stalemate of the poor Cardboard user experience.III、Head motion controlled all-in-one machineAll-in-one machineAIO machine, as its name, is a VR device that does not need to be inserted into a mobile phone or connected to a PC. Currently, there are representative DaPeng, Xiaoniao, KanKan, etc. Most of the products are listed in 2016. The features of these products are basically the same use of 1080p or 2K resolution display screens (some of which also use 2Kx2 dual screens) with specially designed FIN products designed for VR products aspherical optical lens. The overall picture quality and distortion have improved a lot. However, these products have a common feature, that is, only a simple head control, can only sit or stand in place by shaking his head to achieve VR control, can not do the first hand interaction. In order to remedy this defect, there are currently some external accessories with spatial position detection (the built-in IMU handle, somatosensory backpack, spatial positioning light ball, etc.) to enhance the overall VR user experience.IV、 AIO machine with space monitoring and positioningAIO machine with space monitoring and positioningSpace monitoring and positioning are generally two ways, Inside-out and Outside-in. Inside-out senses the spatial information outside the device through the built-in sensor and performs related positioning. The Outside-in is just the opposite. It uses an external sensor to sense the position of the VR device and provides positioning information to the VR application. For the all-in-one machine, the current view has selected the Inside-out solution without exception, thus avoiding the need to install an external sensor in advance. The user can pick up the VR device at any time and anywhere. It is expected that some of the major products coming on the market in 2017, such as the second generation of the DaPeng AIO Machine and the Storm AIO Machine, will have space positioning capabilities, which will greatly enhance the VR user experience, especially VR games.V、 PC VRPC VRThe most representative products are the HTC Vive, Sony PSVR and HTC Oculus. After the three swordsmen went public in 2016, the HTC Vive has become a standard configuration for the VR experience room. Many other industry customizations are based on Vive. Sony PSVR has sold about 1 million units in less than half a year, which has greatly improved the overall level of user experience in the entire VR industry. The feature of these three products is the use of external space positioning technology. For example, Vive uses an external infrared laser transmitter, head and handle senses transmitter location to determine its position and trajectory. PSVR and Oculus use external sensors to sense the visible light or infrared light emitted by the headlights and the handle to determine the positions of the heads and the handles, so that the heads and the handles can accurately know their respective relative positions and trajectories in space at any time. This can make the application of VR more realistic.Next, let’s talk about AR products. At present, there is a big gap between AR products. Some AR glasses products only project virtual information, images, etc., and are not actually related to the actual environment where the user is located. Such products can only achieve 6DOF motion tracking by the projected virtual information following the head movement. But it is impossible to fuse the virtual object with the actual environment where the user is. For example, the famous ODG, the latest product only supports 6DOF motion tracking, there is no spatial positioning function.AR product ODGShanghai Zhishi's smart glasses also have similar functions to those of ODG, but their positioning is a live broadcast from the first point of view. Therefore, only relevant information and videos for shooting can be displayed in the glasses without spatial positioning. However, it is understood that they are also developing a built-in TOF depth camera glasses, which can achieve 6DOF + spatial positioning function.Shanghai Zhishi's smart glassesThe currently available AR products have the best space monitoring and positioning capabilities. The best match for virtual objects is the Lenovo Phab2 Pro based on Google's Tango space positioning technology and the Microsoft Hololens. Although these two products are very different in shape, they are essentially the full integration of 6DOF+SLAM, achieving spatial positioning and motion tracking. Their AR effects can basically be virtual objects and the actual environment. Convergence, no matter how the user moves or views from what angle, the feeling is just like the real object is in front of me. However, Hololens' accuracy and stability of 6DOF+SLAM are still higher than those of Tango in terms of the effect of actual use. This is closely related to the choice of hardware design platform, type and number of sensors, and core algorithms.Hololens ARIn addition, there are actually many companies in the country that are developing related AR products. Among them, the distinctive feature of Micro Eye's SMAKKEST is not only similar to Hololens, but also similar to Hololens in terms of function. The effect of 6DOF+SLAM is said to be recognized by Hololens.  AnalysisVI、Space positioning technology categorySpace monitoring and positioning technology, in fact, can be divided into two major categories initially, one is the Inside-out space monitoring and positioning, and the other is the Outside-in space monitoring and positioning.1. Inside-out space monitoring and positioning technologyInside-out space monitoring and positioning technology, technology is essentially similar to the process of human-to-environmentally-aware environment of the human eyewear. It senses the external space from the inside of the device and is therefore called the Inside-out positioning method. Inside-out space monitoring and positioning technology is also divided into two categories. One is the spatial monitoring and positioning based on SLAM technology. This is also a basic function required by the fiery robotics industry. SLAM is the English abbreviation for simultaneous localizatiion and mapping. It means that the device itself starts to move from an unknown location in an unknown environment, locates itself according to location estimates and maps during the movement, and builds incremental maps based on its own positioning to achieve autonomous detection and positioning navigation of the device itself. . At present, most AR products use Inside-out spatial location technology.The representative products of the space monitoring and positioning technology based on SLAM are Lenovo Phab2 Pro Tango mobile phone and Hololens. Both use depth monitoring + Fisheye and IMU fusion for sports monitoring. The difference is that the depth monitoring technology is different (Tango uses TOF, and Hololens uses structured light) and the number of Fisheye motion and feature point monitoring is different. Hololens' spatial positioning effect is more accurate and stable than Tango's, and Hololens' effect is in low light and glass light transmission. The current Tango victory, but Tango technology is not static, the next generation of Tango technology also supports multiple Fisheye camera.The Lenovo Phab2 Pro Tango phone uses a TOF depth camera, a 155-degree FOV Fisheye motion monitoring camera and an RGB camera, Fisheye motion monitoring camera with IMU data fusion, feature point matching, providing the device with a complete trajectory The monitoring, together with the cloud image information of the TOF depth camera, can plot the position of the device itself in space and the trajectory of the movement in real time. At the same time, through Tango's own zone learning function, when returning to the space that has already passed, once the Fisheye camera By detecting the stored feature points and matching them, it is possible to quickly perform spatial positioning. This is very important for AR equipment and it ensures that users can quickly use it anytime, anywhere. The working principle of Tango is not explained here. You can refer to Lin Shigong's another article for detailed understanding.The working principle of TangoThe Hololens design of Microsoft is very unique and very affluent. It has newly developed an HPU (Holographic Processing Unit) based on Intel's CPU and GPU technology. The device adopts the configuration of CPU+GPU+HPU. Like Tango, it does not need to External PCs look to achieve complete space monitoring and positioning. On the sensor side, depth monitoring uses two structured light cameras with four structured light-grating emitters for depth monitoring. In addition, there are two Fisheye cameras on the left and right of Hololens, so that more feature points in the space environment can be monitored. Hololens' space positioning accuracy and stability are therefore much higher than those of Tango.HPU（Holographic Processing Unit）The other type is based on the marker (pointer) space monitoring and positioning technology, simply put some like two-dimensional code, special color graphics patterns or light spots as markers in the actual space, equipment to monitor these markers The location of the point to determine their position and movement trends. The HTC Vive is a representative of this type. The following figure shows the working principle of spatial location of the HTC Vive.The working principle of spatial location of the HTC ViveVive emits laser light through two fixed laser emitters. Each base station has an infrared LED array. Two infrared laser emitters with rotating shafts perpendicular to each other are distributed. One is X-axis scanning, and the other is Y-axis scanning. The lasers have a fixed phase difference of 180 degrees. When one of the lasers emits an X-axis scan, the other laser emits a Y-axis scan.The HTC Vive has a shell that is densely covered with 32 light sensors, each oriented in different directions. These sensors are used to receive the infrared laser emitted by a fixed laser emitter. The computer connected to Vive controls all the devices to operate synchronously. The light sensor on the head reveals the time when the laser light reaches each sensor in the X-axis and Y-axis directions and the phase relationship between the two different laser emitters, and the phase difference of each light sensor can be calculated. Accurately locate the head position and trajectory.There are 24 light sensor on the Vive handle. The working principle and head of the handle are the same. It will not be repeated here.The HTC Vive ShellIn addition, it is necessary to mention that domestic Ximmerse, they also introduced a VR device for the Outside-in space positioning package design, through this space positioning package, can provide space-free VR devices with similar accuracy with the HTC Vive Space monitoring and positioning capabilities. The positioning package includes a dual camera module, two control handles with a light ball. When used, the dual camera module is externally mounted on the head display. The dual camera captures the light ball of the control handle to determine the position of the handle in the space, and the handle Through BT to transmit its 6DOF information to the module, the module fuses the 6DOF and the position information of the ball to achieve omni-directional positioning, thereby improving the interaction of the first hand. The advantage of this solution is that under any ambient lighting conditions, the positioning accuracy is not affected by the ambient light, and the positioning accuracy is high. However, this solution cannot monitor and locate the overall space environment in which the user is located. It can only monitor the spatial position information of the photo ball handle, but its advantage is that the original VR device without space positioning can have at least similar HTC Vive. Spatial positioning capabilities.Ximmerse2. Outside-in space monitoring and positioning technologyOutside-in space monitoring and positioning technology is currently the VR device is a relatively mature space positioning technology, Sony PSVR and Oculus are based on a similar program, but Oculus is in an external infrared camera plus point initiative marks the way to get Higher accuracy and faster response time. The PS VR directly uses the PS 3's MOVE system. The principle is similar to that of the Kinect. An external binocular depth camera is used for motion recognition and tracking. There is a light indication on the head, and a different color light ball is at the top of the handle. The external dual camera checks the trajectory of the headlight and the ball on the handle at any time. At the same time, the PS StaTIon receives the IMU information of the head display and handle returned by the BT. , Through the calculation you can get a complete headshot and handle movement trajectory and positioning in space.PS StaTIonFrom the principle and the effect of actual use, the space monitoring and positioning precision of HTC Vive is not high, although Sony's gaming and PSVR wearing wearing their own moderate than Vive better, but the spatial positioning accuracy is not high, it affects the VR The overall experience of the game. So we see from Sony's official website a new spatial orientation of Sony patent, this patent is to be ready for the next generation of PVSR, from the description of the patent point of view should be similar to HTC's fixed laser emitters way, with this program The current practice of PSVR is the opposite. Instead of using an external camera to take pictures (outside-in positioning), the external VR signal is used to locate the direction of the VR helmet in space. This can provide similar HTC Vive usage accuracy (probably higher), and can capture the user's various poses and trajectories 360 degrees without dead ends.Outside-In positioningOculus space monitoring and positioning technology with Sony PSVR similar difference is PSVR camera uses a dual monitor visible external program, and is an active Oculus uses infrared light to the head and the handle are placed significant infrared emitting LED , Through an external infrared camera for shooting and capturing the headlights and infrared light spot information on the handle, so as to obtain head trajectory and handle movement trajectory and spatial position information.Whether it is Sony PSRV or Oculus's Outside-in program, there is a problem, that is, the external camera is fixed, and when the user is back to the camera, the camera can not detect the head and the handle on the light, may There is a possibility of missed supervision, thus affecting the user experience, which does not exist on the HTC Vive.Another Marker point-based Outside-in space monitoring and positioning technology is Ximmerse's photosphere with dual-camera solution. This is contrary to their previously mentioned Inside-out solution, where dual camera monitors have been placed. Indoor fixed position, and then put the ball in the VR head and handle, head and handle during the movement of a dual camera monitor recorded head and handle in the space of the three-dimensional position and their movement data, through BT or WiFi is passed to VR heads to perform related operations and processing, and feedback is implemented on the screen to allow them to freely move around in the virtual environment and interact with things in the virtual world.Lightball + Dual Camera SolutionAnalog of Lightball + Dual Camera SolutionHere is a video about Augmented Reality vs Virtual Reality:Augmented Reality vs Virtual Reality - AR vs VR | The Future ! | Tamil Tech  Book RecommendationVirtual, Augmented, and Mixed Realities in EducationThis book describes the current state of the art of various types of immersive learning: in research, in practice, and in the marketplace. It discusses advanced approaches in the design and development for various forms of immersive learning environments, and also the emerging innovations in assessment and research in the field.--by Dejian Liu, Chris Dede, Ronghuai Huang, John Richards Experience on Demand: What Virtual Reality Is, How It Works, and What It Can DoVirtual reality is able to effectively blur the line between reality and illusion, pushing the limits of our imagination and granting us access to any experience imaginable. With well-crafted simulations, these experiences, which are so immersive that the brain believes they’re real, are already widely available with a VR headset and will only become more accessible and commonplace. But how does this new medium affect its users, and does it have a future beyond fantasy and escapism?--by Jeremy Bailenson  Relevant information about "Research on Space Monitoring and Location Technology of AR&VR Equipment"About the article " Research on Space Monitoring and Location Technology of AR&VR Equipment", If you have better ideas, don't hesitate to  write your thoughts in the following comment area. You also can find more articles about electronic semiconductor through Google search engine, or refer to the following related articles. 

Warm hints: The word in this article is about 3000 words and  reading time is about 15 minutes.   This paper is mainly about how to learn analog circuit design. An analog circuit is a circuit used to transmit, transform, process, amplify, measure, and display analog signals. Analog signals refer to continuously changing electrical signals. Analog circuit is the basis of the electronic circuit, which mainly includes amplifier circuit, signal processing, and processing circuit, oscillation circuit, modulation and demodulation circuit, and power supply.    Analog circuit   Catalogs   I. What’s the Engineering Thinking in Analog Circuit II. Commonly Used Semiconductor Devices III. Negative Feedback Basic Concepts IV. Operational Amplifier Development V. Conclusion FAQ I. What’s the Engineering Thinking in Analog Circuit   Analog circuit is a very important profession, and difficult for people to learn. Now, let me talk about my understanding of the analog circuit. When it comes to the understanding and application of analog circuits, I’ve done some projects and participated in competitions. The analog circuit is an engineering course, and the earning focus is to master the engineering ideas. It’s better to put it into practice, instead of only doing the exams. What is the engineering idea? Encyclopedia +explains as this: "Engineering is the application of science and mathematics. Through this, natural material and energy characteristics can be made into efficient, reliable, and human-friendly products flow through a variety of structures, machines, products, systems, and processes, with the shortest Time, and less refined manpower, so the concept of engineering comes out and it has evolved into an independent discipline and skill. "For example, in analog circuits, there is a very Important engineering thinking - approximation.   In high school physics class, we learn a lot of circuits are ideal circuits. The wire resistance is always 0, the transformer efficiency is 100%, the ideal voltmeter resistance is infinite, the ideal ammeter resistance is 0, and so on. You can see that many times the calculation in an analog circuit will often omit one or two smaller items and use the equal sign instead of the equal sign directly.   Why use an approximation? To put it plainly, people’s understanding of nature in human science is not comprehensive enough to describe the natural phenomenon with absolute precision. Or human’s understanding is limited. By the means of approximation, people have not only achieved an obvious effect on solving the problem but also greatly simplifies the procedure and saves time and effort. With this thought, many achievements have been made in human science, which has also proved its reliability.    Summary Mold itself is a very complex subject, and the molding course is just one of the most basic things. Analog Circuit Meaning is the electronic circuit that processes analog signals. Most of the signals in nature are analog signals, and they have continuous amplitude values, such as the sound signal when speaking. Analog circuits can be such signal processing (of course, need to be converted into electrical signals), such as amplifier to amplify the sound signal, the radio can send analog sound signals, image signals. It can even be assumed that all circuits are based on analog circuits (even for digital circuits, the underlying principle is based on analog circuits). Its importance is self-evident.    Due to the rapid development of digital circuits and programmable devices, many superior features are demonstrated. Many electronic devices are slowly digital but still can not do without analog circuits. The most important analog circuit devices, non-semiconductor devices are none other than. The most basic and commonly used semiconductor devices are diodes, transistors, FETs, and operational amplifiers. II. Commonly Used Semiconductor Devices   The diodes have many roles. Ordinary diodes can be used for rectification, light-emitting diodes can be used for indicator and lighting, regulators can be regulated, varactor diodes can be used for signal modulation. The mold course related to the part of the diode is relatively simple. And many characteristics of the FET are similar to the transistor, so we often explain transistor or amplifier instead.    The basic function of the transistor is to enlarge. The transistor constitutes a variety of circuits because of its features, reflecting a lot of engineering ideas. The transistor-based circuit is the amplifier whose input sound is small, the output sound is great. Amplifier output and the input voltage (or current) ratio is called magnification, also known as gain. For a voltage, if the time for the horizontal axis, voltage vertical axis for mapping, the graph is the voltage waveform. If an amplifier with a gain of 5 inputs a constant voltage of 1V (the waveform on the left is shown below), the output should always be 5V (the waveform is shown in the middle figure below), neither changing with time nor changing with temperature And the input voltage exactly the same shape. However, if the magnification is unstable and constantly changing, the original input signal will be distorted (as shown on the right), and the signal may change from a horizontal straight line to a curved line. This waveform change is called distortion. Voltage waveform   III. Negative Feedback Basic Concepts   The basic concept of negative feedback makes some very powerful people find a good way: negative feedback. What is negative feedback? "Feedback refers to the output of the system is returned to the input and affect the input, thus affecting the overall system output Feedback can be divided into positive feedback and negative feedback is to make the output and input the opposite effect, the system Output tends to be stable. "The above explanation is hard to make sense. I have two examples. When playing the inverted pendulum, we propped up an inverted wooden stick by hand. When the wooden stick was tilted in one direction, we offset the change by moving the hand to the direction of the stick so that the stick could be in our hand's balance.    When I was in high school, I often had a monthly test. I found that some of my classmates had a habit of starting a good study when a test score was poor and going up next time. When the test was better, the next month will be relaxed, so results will come down again, so again and again. Both of these examples illustrate that negative feedback can make the system more stable. We ignore the specific circuit, only draw a simple diagram to illustrate how the transistor amplifier uses the negative feedback. The triangle below shows a transistor consisting of an amplifier, the magnification is A, the input is I, the output O = I * A, because the magnification A instability, so the output waveform will be distorted.  Negative feedback   Some devices have been added to the circuit as follows. The purple circle is the adder, combined with the purple "+", "-" symbol that its output Y = (+ I) + (- X) = I-X, in the actual circuit with the resistance can be achieved; Block F is the feedback device, which means that the signal is taken out from the output O and multiplied by F to get X, so X = O * F, where F <1 (this part can be realized by resistance in the actual circuit). Triangle refers to the amplifier A, mainly composed of transistors, meeting O = A * Y, and A magnification is unstable, easy to be disturbed. Add a feedback device   You can list the equations: Y = I-XO = Y * AX = O * F to calculate the gain of the entire circuit: Formula   If the magnification A is very large, while F is not small, A * F 》》1 symbol "》》" suggests far greater than the approximate idea. The entire circuit magnification: Formula   IV. Operational Amplifier Development   1.Working principle of operational amplifier Because the feedback device can be realized by the resistance, the resistance value of the ordinary resistance is not easily disturbed by the outside world, so the value of F is very steady, so the magnification of the whole circuit is very steady. We succeeded in solving the stability problem of the transistor by negative feedback. We can see here that the feedback part and the amplification part form a ring, so the amplification of the whole circuit is called the loop gain or the closed-loop gain. Before adding the feedback, the amplification of circuit A is called the open-loop gain. Due to the negative feedback, the stability of the circuit is improved, but there is also a cost: Because the AF 》》1, then "A》》1 / F" open-loop gain is much larger than the closed-loop gain, which means the amplifier gain is greatly reduced. But in general, this is worth it for stability. Operational amplifier In the above circuit, in order to actually create a large open-loop amplifier gain A, often with multi-stage transistor amplifier in series design.   Because the high demand for such high-gain amplifiers is very common, so some people in history put them into a finished circuit board module. This is used directly as a component on the line when needed because it’s very convenient. This is the original op-amp, which is referred to as op-amp. The development of integrated circuits makes a large number of transistor components integrated into a small chip possible, so the common integrated operational amplifier turns up today.    The "op-amp" is named for its mathematical operation originally used to simulate computers. Although now widely used digital computer is no longer used to calculate the operational amplifier, but the name still retained. Today, op-amps play an important role in analog circuits and have also become one of the focuses of the analog circuit. The op-amp has virtual short and virtual interrupt characteristics. Usually, op-amp has two inputs U + and U-, an output Uo, between them to meet Uo = A * (U + -U-) op-amp open-loop gain A often up to dozens Million ~ millions, but the op-amp output voltage limited by the supply voltage can not exceed the supply voltage. So the op-amp input-output relationship similar to the shape below. In the figure, the horizontal axis is (U + -U-) and the vertical axis is Uo. Op amp input - output In the middle of a straight line, the op-amp is in the normal state of amplification, called the linear region, meeting Uo = A * (U + -U-). When the absolute value of the input becomes slightly larger, the output will be power limited, no longer satisfying the above relationship. The value of Uo is usually slightly smaller than the supply voltage range (note that the op-amp can be dual supply, that is the supply voltage range can be afloat between a negative value and a positive value), which is called the non-linear region. Rail-to-rail op-amp output can reach the power supply voltage.   When the operational amplifier in the linear region, the Uo value is very limited, but A large. So U + -U- = UoA ≈ 0 or U + ≈ U-. At this time, the positive and negative op-amp input voltage is almost equal, like a short circuit similarly, which is called a short circuit. So only when the operational amplifier in the enlarged area will have "virtual short" characteristics, rather than the inherent properties of the op-amp. On the other hand, due to the internal structure of the op-amp, its input impedance is large.    The input impedance can be simply understood as: the input impedance = input voltage/input current input impedance, which means that the op-amp input with only a small current can work properly. Because of this, an op-amp can be used for some weak current detection, such as the human brain, myoelectric wave, whose maximum voltage is only a few mV, the current value is very small. This feature of the op-amp is called a virtual interrupt, meaning that there is almost no current flowing into the input like the open circuit. Different from the short circuit, a virtual interrupt is the inherent properties of the op-amp, which will not change with the circuit.   2.Op amp non-ideal characteristics   The op amp's non-ideal characteristics of the op-amp by the transistor composition. Obviously, like the transistor, there will be many undesirable characteristics. The actual operational amplifier will not fully meet the short virtual fault characteristics. Its normal work needs input current input, which is called the input bias current.    The same op-amp input offset voltage, input offset voltage, input offset current, and other non-ideal parameters. These non-ideal characteristics, such as the input bias current is small, sometimes will have a great impact on the circuit, resulting in the circuit does not work. Therefore, there are some ways to reduce the impact of these factors. In practical applications, the non-ideal characteristics of the op-amp are a very important issue. There are many ways to eliminate the non-ideal characteristics of the op-amp, but not introduced here.    Other cores of the molding course are the transistor and op-amp. Around these devices, the molding course will explain a variety of circuits, including the calculation of the amplifier circuit analysis, multi-stage amplifier circuit, the amplifier frequency characteristics, the idea of feedback, power amplifier circuit, comparator, oscillator, integrator, differentiator, waveform generation, Signal processing, filter, integrated power supply circuit and so on. When comparing op-amp and transistor In the actual design of the circuit, the op-amp will be more than the transistor. Because many of the features of op-amps are better than triodes, the circuit design is simple, and the cost of op-amps is often not too high.   Many times you can achieve the same effect with the transistor and op-amp and lower cost of each op-amp. Because op-amps integrate a large number of transistors, the average cost per transistor is very low. For example, a conventional audio pre-amplifier can be handled with a universal op-amp. and if you use the transistor, you may need more transistors, and the human cost during design is far higher than the op-amp program. Of course, the transistor has its advantages.    In some very simple circuits, the stability of the magnification is not strictly required, one or two transistors can accomplish. And triodes are often used to save costs. In addition, in some extreme conditions, such as working in high-frequency and high-power environments (such as RF signal transmitting circuits), a well-designed triode circuit will perform much better than an op-amp, or at a much lower cost. Even in some conditions, only the transistors can be completed, then you need to choose the transistor to build the circuit.   This video give a detailed explanation about analog circuit: Analog Circuits Lecture V. Conclusion   Analog circuits are a very complex discipline that involves more than knowledge written in books. Books are generally introduced in accordance with the principle of work, simplifying a lot of difficulties to understand, but in reality, more factors must be considered. So the gap between the actual circuit and the book is very large. Such as triangular wave generator built with an op-amp introduced in analog circuit books usually can not work in all likelihood. However, the main principle of the actual circuit is the same as the book description. Therefore, the design of analog circuits often requires a lot of experience, for there are many things that can not be explained and even difficult to calculate. I hope this article can help you learn more about analog circuits. FAQ   1. What is meant by analog circuit? The Analog electronic circuit includes an analog signal with any continuously changeable signal. While working on an analog signal, an analog circuit alters the signal in some manner. Analog circuit can be used to convert the original signal into some other format such as a digital signal.   2. What is the difference between digital and analog circuits? Analog Circuits and Digital Circuits is a classic way of differentiating between two types of electronic circuits based on the signals they process. To put it in simple words, Analog Circuits deals with continuous analog signals whereas Digital Circuits deals with discrete digital signals.   3. Where are analog circuits used? Analog circuits represent key components of communications and other systems in widespread, growing commercial use. High-speed transistors are essential to the operation of such circuits.   4. Is digital cheaper than analog? If you are looking at the straight-up module cost an analog vs. a digital version, then yes, the analog module will likely be a cheaper solution. However, if you look at the total cost, or the “value” of the digital module versus an analog solution, then digital will in fact be “cheaper”.   5. What is analog design? Analog design is part of integrated circuit design and focuses on signal fidelity, amplification and filtering. Those who perform the function of analog design are qualified electrical engineers.   6. Why is analog design difficult? Ask most engineers and they would tell you why: analog design is harder than digital, and requires more knowledge and more factors to consider such as a deep understanding of efficient power, precision measurement, wireless connectivity, and reliable circuit protection.   7. Which is better analog or digital design? Analog circuits can be precise, elegant design with various components with very simple. For example, two resistors joining to make a voltage divider. Generally, Analog circuits are much more complex to design compared to which complete the same task as digitally.   8. What is the tool used for analog circuit design? A suite of web tools to help you design signal conditioning circuits faster: Analog Filter Wizard, Precision ADC Driver Tool, Photodiode Wizard, In Amp Diamond Plot, Direct Digital Synthesis Simulator, and Virtual Eval.   9. How hard is circuit design? Circuit design is a lot like any other learned skill, you start with the basics. These basic circuits can be learned in a few days. ... So yes, it can be very difficult to reach a high level of design expertise and you never really master it because the art continues to evolve.   10. How does circuit design work? Digital electronic circuit design takes the electrical signals in the form of discrete values. The data are represented in the form of zeros and ones. Digital circuits extensively use transistors, interconnected to give create logic gates that provide the function of Boolean logic.   You May Also Like:   Look Forward to the Future of Semiconductor GaN High-Electron Mobility Transistor Power Amplifier Trojans are everywhere even the hardware Remote Electronic Transport Promote Organic Photovaltaic Power Generation Make Next-Gen of Computer Be Faster,Better, More efficient Some suggestions about protecting transformers  

Warm hints: The word in this article is about 1000 and the  reading time is about 6 minutes.SummaryResearchers from Purdue University showed a range of concepts and technologies about semiconductor industry at international IEDM 2016 Conference in Dec. 2016. Looking forward to the future of semiconductor,which concepts included innovations to extend the performance of today's silicon-based transistors,along with entirely new types of nanoelectronic devices to complement and potentially replace conventional technology in future computers. This is a device is made from the semiconductor germaniumIssueIn the conference,researchers said,"For the past 50 years, ever more electronic devices envelop us in our day-to-day life, and electronic-device innovation has been a major economic factor in the U.S. and world economy," said Gerhard Klimeck, a professor of electrical and computer engineering and director of Purdue's Network for Computational Nanotechnology in the university's Discovery Park. "These advancements were enabled by making the basic transistors in computer chips ever smaller. Today the critical dimensions in these devices are just some 60 atoms thick, and further device size reductions will certainly stop at small atomic dimensions." New technologies will be needed for industry to keep pace with Moore's law, an observation that the number of transistors on a computer chip doubles about every two years, resulting in rapid progress in computers and telecommunications. It is becoming increasingly difficult to continue shrinking electronic devices made of conventional silicon-based semiconductors, called complementary metal-oxide-semiconductor (CMOS) technology, said Muhammad Ashraful Alam, Purdue University's Jai N. Gupta Professor of Electrical and Computer Engineering. "As transistors are becoming smaller they are facing a number of challenges in terms of increasing their performance and ensuring their reliability," he said. Purdue researchers presented five papers proposing innovative designs to extend CMOS technology and new devices to potentially replace or augment conventional transistors during the annual International Electron Devices Meeting (IEDM 2016) Dec. 5-7 in San Francisco. The conference showcases the latest developments in electronic device technology. Purdue researchers are in the  laboratoryIntegrated circuits, or chips, now contain around 2 billion transistors. The more devices that are packed onto a chip, the greater the heating, with today's chips generating around 100 watts per square centimeter, comparable to that of a nuclear reactor. "As a result, self-heating has become a fundamental concern that hinders performance and can damage transistors, and we are making advances to address it," Alam said. Two of the IEDM conference papers detail research to suppress self-heating and enhance the performance of conventional CMOS chips. The remaining papers deal with new devices for future computer technologies that require lower power to operate, meaning they would not self-heat as significantly. "We are not only working to extend the state-of-art of traditional technology, but also to develop next-generation transistor technologies," Alam said. Transistors are electronic switches that turn on and off to allow computations using the binary code of ones and zeros. A critical component in transistors, called the gate, controls this switching. As progressively smaller transistors are designed, however, this control becomes increasingly difficult because electrons leak around the ultra-small gate. One of the conference papers focuses on a potential solution to this leakage: creating transistors that are surrounded by the gate, instead of the customary flat design. Unfortunately, enveloping the transistor with a gate causes increased heating, which hinders reliability and can damage the device. The researchers used a technique called submicron thermo-reflectance imaging to pinpoint locations of excessive heating. Another paper details a potential approach to suppress this self-heating, modeling how to more effectively dissipate heat by changing how the transistor connects to the complex circuitry in the chip.The three remaining papers propose next-generation devices: networks of nanomagnets, extremely thin layers of a material called black phosphorous and "tunnel" field effect transistors, or FETs. Such technologies would operate at far lower voltages than existing electronics, generating less heat. "You want to use as low a voltage as possible because that reduces power dissipation and if you can reduce power dissipation the battery of your cell phone will last longer, you can do more computing with a smaller amount of power and you will be able to cram more functional elements into a given area," Klimeck said. The tunnel FETS could potentially reduce power consumption by more than 40 times. "Reducing power consumption by a factor of 40 would be a huge development," Klimeck said. Another conference paper details research to develop devices made of black phosphorous, which might one day replace silicon as a semiconductor in transistors. Findings showed the devices can pass large amounts of current with ultra-low resistance while demonstrating good switching performance, said Peide Ye, the Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering. "We have demonstrated the highest performance of this kind of 2-D device," Ye said.Peide Ye,the Richard J. and Mary Jo Schwartz Professor of Electrical and Computer EngineeringDevices made from the material also could bring new types of optical and chemical sensors. The devices were created using a technique called chemical vapor deposition in research performed at Purdue's Birck Nanotechnology Center. Future research will include efforts to create smaller black phosphorous devices, Ye said. A fifth paper details how networks of nanomagnets could serve as the building blocks of future computers. Findings show the networks mimic Ising networks - named after German physicist Ernst Ising - which harness mathematics to solve complex probabilistic problems. The nanomagnet networks might be used to draw from huge databases to perform demanding jobs in areas ranging from business and finance, to health care and scientific research. The conventional approach to performing big data computations is through new software running on CMOS devices. However, nanomagnet networks represent a different approach: developing an entirely new type of hardware for the feat, said Zhihong Chen, an associate professor of electrical and computer engineering.The nanomagnet arrays are potential building blocks for probabilistic computer hardware has been proved. Researchers are still in unremitting efforts to creat new semiconductor technologies.  Article Provided by Purdue UniversityArticle edited by kynix

Warm hints: The word in this article is about 1000 and the  reading time is about 6 minutes.SummaryFujitsu,a company that provide innovative IT services and digital technologies like mobile,AI,cloud or etc,announced the development of a gallium-nitride(GaN) high-electron mobility transistor(HEMT) power amplifier for use in W-band(75-110 GHz)transmissions in July 2017 at the 12th international Conference. To realize long-distance,high-capacity wireless communications,a promising approach is to utilize the W-band and other high frequency bands that encompass a broad range of usable frequencies, and increase output with a transmission power amplifier. At the same time, demand exists for improved efficiency in power amplifiers in order to mitigate the increased power consumption of communication systems. Fujitsu has now succeeded in developing a power amplifier for use in W-band transmissions that offers both high output power and high efficiency, improving transistor performance through the reduction of electrical current leakage and internal GaN-HEMT resistance. Fujitsu has achieved 4.5 watts per millimeter of gate width, the world's highest output density in the W-band, and has confirmed a 26% reduction in energy consumption compared to conventional technology. Fujitsu anticipates that setting this power amplifier between wireless communication systems in two locations will achieve high-bandwidth communications at 10 gigabits per second (Gbit/s) over a distance of 10km. Part of this research was carried out with support from Innovative Science and Technology Initiative for Security, established by the Acquisition, Technology & Logistics Agency (ATLA), Japan Ministry of Defense. Development Background Wireless data traffic from mobile communications has increased dramatically over the last few years, and with the spread of 5G and IoT devices it is predicted to increase at an annual growth rate of 1.5 times until the year 2020. In order to build this sort of high capacity next-generation wireless communications network, attention has been focused on wireless communication technology using the high frequency W-band. The range of frequencies that can be used in the W-band is very broad, and because communication speed can be rapidly increased in this band, it is well-suited for this kind of high bandwidth wireless communication. Conventional wireless communications technology, has allowed for performance of several Gbit/s over distances of several kilometers, but achieving an even greater increase in wireless communication distance and capacity utilizing the W-band demands further increases to the output of power amplifiers to boost signals during transmission. Issues To increase distance and capacity, it will be necessary to expand the frequency bandwidth that can be amplified while simultaneously supporting modulation methods that can transmit more information within the same frequency bandwidth, and a strong requirement is to have less distortion when the signal is amplified. Another pursuit is keeping in check the energy consumption of communication systems that accompanies greater distances and capacities, and the improved energy efficiency in power amplifiers.In order to both increase the distance and capacity of wireless communications and decrease energy consumption with indium-aluminum-gallium-nitride (InAlGaN) HEMTs, Fujitsu has developed two technologies that effectively reduce internal resistance and current leakage. Features of the newly developed technologies are as follows: Technology to reduce internal resistance Fujitsu has developed device technology that can reliably reduce resistance to one tenth that of previous technology when current flows between the source or drain electrodes and the GaN-HEMT device. The technology utilizes a manufacturing process that embeds GaN plugs directly below the source and drain electrodes, which generate electrons at high densities (fig. 1). It is necessary to transport the electrons that come from the source electrode to the two dimensional electron gas field as smoothly as possible. The structure of the previous technology causes the electron supply layer to become a barrier, however, and internal resistance increases between the source electrode and the two dimensional electron gas. By applying this new technology, Fujitsu succeeded in running high currents through the transistor with significantly less resistance (fig. 2). Technology to control current leakageA current leakage occurs when the two dimensional electron gas, which moves at high speed on the boundary at the top of the channel layer, takes a detour below the gate when the transistor is in its off-state. This leakage causes deterioration in the operational performance of the power amplifier. Normally, it is possible to reduce current leakage by placing a barrier layer beneath the channel layer, but in that case the amount of two dimensional electron gas also decreases, and leads to a reduction of the drain current. This new technology maintains high drain currents by effectively distributing indium-gallium-nitride (InGaN) to create a barrier layer below the channel layer. This reduces electron detours during operation, successfully providing significant reductions in current leakage(just see the fist and second picture).Effects The previous world record for power amplifier output density in the W-band for transmitters was 3.6 watts per millimeter of gate width with technology developed by Fujitsu Laboratories. This has improved significantly with the newly developed technology, which delivers power output of 4.5 watts per millimeter of gate width for a power amplifier designed to operate at 94GHz. In addition, this new technology achieved a reduction in energy consumption of 26% compared to the previous technology through a reduction in current leakage. It is anticipated that the use of this power amplifier will allow the achievement of high capacity, long distance wireless communications between two connected systems at different locations at over 10Gbit/s and at distances greater than 10km.Fujitsu aims to apply this technology broadly to the development of power amplifiers for purposes that call for wireless communications that offer long range and higher capacity, while offering easier installation than fiber optics. The goal is to commercialize this technology in high speed wireless communication systems by 2020, with an aim to employ it in such situations as a method of restoring communications when fiber optic cables have been severed by natural disasters or as a way of setting up temporary communications infrastructure when holding events.  Article provide by FujitsuArticle edited by kynix

SummarryWhen I see this paper,The things occurred in my mind is that I need to let others to know it and prevent it.From morning until now,I always solve my computer's Trojans.This is terrible. Trojans may break our computer although it look like there doesn't matter.Trojans aren everywhere even the hardware in some instances, hardware Trojans could even open backdoors in custom silicon. BodyOutsourcing has reshaped the way electronics products are made – and helped to cut manufacturing costs massively. But, as production margins have fallen, so too has trust in the organisations that make up the supply chain. Companies which rely on outsourced manufacturing are having to come up with ways of ensuring that the products shipped to them have not had secure keys leaked or stuffed with viruses and compromised software. Even custom silicon is not safe.Almost a decade ago, researchers from Case Western Reserve University described to delegates at the IEEE High-Level Design Validation and Test Workshop the ways in which they could see hardware malware – or Trojans – being introduced to an IC-design project. The widespread use of foundry services, third-party intellectual property and standard-cell libraries – as well as designers bribed to make circuit-level changes – all provide ways in which Trojans could be sneaked into circuitry.Once it receives a trigger signal, the Trojan could open a backdoor to the group that wanted it introduced. In some use-cases, the Trojan may be introduced simply to compromise the product; no matter how it is used. However, the nature of IC design makes hardware Trojans difficult to deploy as they require skills and levels of access that are probably out of reach of most cybercriminals. But other, lower hanging, fruit remains available to them. State actors have the skills, access and motive that may make the surrepticious deployment of some kinds of silicon highly attractive to them. In practice, such organisations may not bother trying to introduce backdoors without the knowledge of the manufacturer or find other ways to make gain access to secrets. In 2015, the BBC identified declassified documents that confirmed the government convinced Crypto AG in the mid-1950s to compromise the security of its C-52 electromechanical encryption machines. Rather than making physical changes to the hardware itself, the company told the US National Security Agency (NSA) and the UK’s GCHQ which models target governments had bought – a practice that would allow the agencies to target decryption resources more effectively. In 2013, the NSA came under suspicion of encouraging the use of algorithms supplied by specialist RSA that had been subtly weakened to make decryption easier. While some ICs behave as if they have Trojans installed, in reality the backdoors were placed intentionally into the silicon by authorised designers. Usually, they are debug aids that were meant to stay secret, but often did not. Five years ago, Sergei Skorobogatov of the University of Cambridge and Christopher Woods of Quo Vadis Labs used side-channel emissions from the devices to uncover the key that would open the backdoor in the JTAG circuitry of an FPGA and to provide access to the encryption keys stored inside. Although side-channel emissions provide one way to determine whether an IC has been compromised with a backdoor, designers have other options available through the deployment of EDA techniques with Trojan detection in mind. As with anything in cybersecurity, a cat-and-mouse game has produced ever more subtle ways of introducing Trojans and more powerful ways of detecting them. The hardware Trojan is the subject of regular hacking competitions between research teams. For example, the Cyber Security Awareness Week (CSAW) organised by New York University has run several challenges around Trojans. In these challenges, red teams try to circumvent the detection mechanisms used by blue teams. 2013’s CSAW challenge focused on methods to beat FANCI, a largely effective detector developed at Columbia University and NYU. FANCI works on the basis that a Trojan would only have a loose connection to the design such that its logic would seem to be practically unreachable. Code-coverage analysis of the RTL can identify such unconnected lumps of circuitry and flag them up as possible Trojans. A couple of years later, the DeTrust technique created by Jie Zhang and colleagues at the Chinese University of Hong Kong showed one method for fooling FANCI: spreading the suspicious logic across many otherwise independent gates. Months later, Syed Haider and coworkers from the University of Connecticut developed the hardware Trojan catcher (HaTCH), designed to track down stealthier functions inserted at the logic level. Rather than isolate the Trojans before manufacture so they can be removed, HaTCH focuses on remediation. It adds tagging circuitry to legitimate cores that work to prevent any on chip Trojans from activating or succeeding in displaying malicious behaviour, such as opening a backdoor. A more wide-ranging technique that could serve as a defence against Trojans is to insist that all IP be supplied with formal proofs that describe the operations it would be allowed to perform. Any changes would be flagged by formal-verification tools during design and prototyping. Such approaches could still be vulnerable to attacks that tweak designs below the abstraction of RTL. As with the cases where the NSA is understood to have sought the help of manufacturers, weakened encryption is one of the most likely ways in which a practical hardware Trojan might work and evade detection by all but side-channel analysis. And it is possible using a tiny change at manufacture according. At the 2013 International Workshop on Cryptographic Hardware and Embedded Systems, Georg Becker and colleagues from the University of Massachusetts at Amherst showed a proof of concept that simply switched dopants used for one of the transistors in an inverter within a larger AOI standard cell (see figure 1). The result would be an inverter that generated a constant output.A transistor that no longer switched might be caught by a scan test looking for stuck-at faults. But embedded in a pseudorandom number generator, the inverter’s problem could be very hard to track down. Once there, the Amherst team estimated the fault could massively reduce the entropy of the random numbers it produced, resulting in very weak cryptographic keys. In 2014, Takeshi Sugawara of Mitsubishi Electric and a team from the company and Ritsumeikan University showed such a tiny change in manufacturing could be detected after the fact. A combination of focused ion beams and scanning electron microscopy can reveal the dopants diffused into the substrate. It is an expensive proposition, involving delayering of the design and extensive analysis against a layout that contains a map of the expected dopants. However, for the kinds of high-value cryptographic IC that might be the targets of well-financed attackers, it is arguably one more in a list of checks that are readily justified. As with other areas of embedded cybersecurity, the most feasible approach to dealing with the risk of hardware Trojans is one of focusing effort. Architectures such as Trustzone pull functions that need high levels of protection into a small portion of the overall SoC. In principle, this subset is much easier to verify than a design that calls for the either chip to analysed for vulnerabilities. If the secure core is guaranteed to not leak information or provide trapdoors, the value to an attacker of putting a Trojan in the more weakly protected part of the SoC diminishes greatly. For the user of SoCs and the buyer of IP to go into them, the question then becomes one of the level of expected risk and the degree of trust they can put in staff, suppliers and contractors.

SummaryFor years,people had treated the poor conductivity of organics as an unavoidable fact,and this shows that that is no always the case. Said Stephen Forrest,the Peter A. Franken Distinguished University Professor of Engineering and Paul G. Goebel Professor of Engineering at U-M, who led the research,which is  a way to coax electrons to travel much further than was previously thought possible in the materials often used for organic solar cells and other organic semiconductors under the condition of pushing cheap,ubiquitous solar power closer to reality. The fatal weakness of organic material may adjust its conductivityUnlike the inorganic solar cells widely used today, organics can be made of inexpensive, flexible carbon-based materials like plastic. Manufacturers could churn out rolls of them in a variety of colors and configurations, to be laminated unobtrusively into almost any surface. Organics’ notoriously poor conductivity, however, has slowed research. Forrest believes this discovery could change the game.  The team showed that a thin layer of fullerene molecules—the curious round carbon molecules also called Buckyballs—can enable electrons to travel up to several centimeters from the point where theyre knocked loose by a photon. That’s a dramatic increase; in today's organic cells, electrons can travel only a few hundred nanometers or less. But organic materials have much looser bonds between individual molecules, which can trap electrons. This has long been an Achilles’ heel of organics, but the new discovery shows that it may be possible to tweak their conductive properties for specific applications. The ability to make electrons move more freely in organic semiconductors The ability to make electrons move more freely in organic semiconductors could have far-reaching implications. For example, the surface of today's organic solar cells must be covered with a conductive electrode that collects electrons at the point where they’re initially generated. But freely moving electrons can be collected far away from their point of origination. This could enable manufacturers to shrink the conductive electrode into an invisible grid, paving the way for transparent cells that could be used on windows and other surfaces. “This discovery essentially gives us a new knob to turn as we design organic solar cells and other organic semiconductor devices,” said Quinn Burlingame, a U-M electrical engineering and computer science graduate researcher and author on the study. “The possibility of long-range electron transport opens up a lot of new possibilities in device architecture.” Burlingame says that the initial discovery of the phenomenon came as something of an accident as the team was experimenting with organic solar cell architecture in hopes of boosting efficiency. Using a common technique called vacuum thermal evaporation, they layered in a thin film of C60 fullerenes—each made of 60 carbon atoms—on top of an organic cell's power-producing layer, where the photons from sunlight knock electrons loose from their associated molecules. On top of the fullerenes, they put another layer to prevent the electrons from escaping. They discovered something they’d never seen before in an organic—electrons were skittering unfettered through the material, even outside the power-generating area of the cell. Through months of experimentation, they determined that the fullerene layer formed what's known as an energy well—a low-energy area that prevents the negatively charged electrons from recombining with the positive charges left behind in the power-producing layer.“You can imagine an energy well as sort of a canyon—electrons fall into it and can’t get back out,” said Caleb Cobourn, a graduate researcher in the U-M Department of Physics and an author on the study. “So they continue to move freely in the fullerene layer instead of recombining in the power-producing layer, as they normally would. It's like a massive antenna that can collect an electron charge from anywhere in the device.”Forrest cautions that widespread use of the discovery in applications like solar cells is theoretical at this point. But, he is excited by the discovery’s larger implications for understanding and exploiting the properties of organic semiconductors. “I believe that ubiquitous solar power is the key to powering our constantly warming and increasingly crowded planet, and that means putting solar cells on everyday objects like building facades and windows,” Forrest said. “Technology like this could help us produce power in a way that’s inexpensive and nearly invisible.” The study is titled “Centimeter-Scale Electron Diffusion in Photoactive Organic Heterostructures.” The research was supported by the U.S. Department of Energy SunShot Program and by the Air Force Office of Scientific Research.    Article from University of MichiganArticle edited by kynix