[Guide] For a newly designed circuit board, debugging often encounters some difficulties, especially when the board is large and there are many components, it is often impossible to start. But if you master a reasonable set of debugging methods, debugging will be more effective.
For the new pcb board that I just got back, we must first observe whether there are any problems on the board, such as whether there are obvious cracks, short circuit or open circuit. If necessary, check if the resistance between the power supply and the ground is large enough.
Then there is the component installed. Modules that are independent of each other, if you are not sure that they are working properly, it is best not to install them all, but to install some of them (for smaller circuits, you can install them all at once), so that it is easy to determine the fault range. When you have problems when you are not getting it, you can't start. In general, you can install the power supply first, and then power on to check if the power supply output voltage is normal. If you don't have much control when powering up (even if you have a great grasp, it is recommended to add a fuse, just in case), consider using an adjustable regulated power supply with current limiting. First, preset the overcurrent protection current, then slowly increase the voltage value of the regulated power supply, and monitor the input current, input voltage, and output voltage. If there is no overcurrent protection and other problems during the upward adjustment, and the output voltage is also normal, the power supply is OK. Otherwise, disconnect the power supply, look for the point of failure, and repeat the above steps until the power is normal.
Next, gradually install other modules. Each time a module is installed, it is powered on and tested. When powering up, follow the above steps to avoid over-current and burn out components due to design errors or/and installation errors.
There are several ways to find faults:
1 measuring voltage method. The first thing to confirm is whether the voltage of each chip's power supply pin is normal, and then check whether the various reference voltages are normal, and whether the working voltage of each point is normal. For example, when a general silicon transistor is turned on, the BE junction voltage is about 0.7V, and the CE junction voltage is about 0.3V or less. If the BE junction voltage of a triode is greater than 0.7V (except for special triodes, such as Darlington), it may be that the BE junction is open.
2 signal injection method. Add the signal source to the input, and then measure the waveform of each point backwards to see if it is normal to find the fault point. Sometimes we will use a simpler method, such as holding a dice by hand, touching the input terminals of each level to see if there is any reaction at the output, which is often used in audio, video and other amplifier circuits (but note that the hot backplane This circuit cannot be used for circuits or circuits with high voltages, otherwise it may cause electric shock. If there is no reaction at the previous level and there is a reaction at the next level, the problem is at the previous level and should be checked.
3 Of course, there are many other ways to find fault points, such as watching, listening, smelling, touching, etc. "Look" is to see if the component has obvious mechanical damage, such as cracking, blackening, deformation, etc.; "listening" means listening to whether the working sound is normal, for example, something that should not ring, the sound is not ringing or sounding. Not normal; "smell" is to check for odor, such as the smell of burning, the taste of the capacitor electrolyte, etc., for an experienced electronic maintenance personnel, these odors are very sensitive; "touch" is used Try to test if the temperature of the device is normal, such as too hot, or too cold. Some power devices generate heat when they work. If they are cold, they can basically be judged that they are not working. But if the hot place is not hot or the hot place is too hot, it will not work. General power triodes, voltage regulator chips, etc., working below 70 degrees is completely ok. What is the concept of 70 degrees? If you put your hand on it, you can stick it for more than three seconds, which means the temperature is about 70 degrees (be careful to test it first, don't burn your hand).
Ok, about the debugging problem, we will talk about it so much today. If you want to know more debugging methods and experience, you can look for some books on home appliance repair. A good designer should first A good maintenance person.
- The Description of 3G 4G LTE/5G Antenna
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2G base station: GSM: 900/1800MHz; CDMA: 800 MHZ;
3G base station: CDMA2000&WCDMA: 2100MHz; Td-scdma: 1880-1920201 0 0-2025232-2370 MHZ;
4G base station: TDD-LTE: 2320-2370,2570-2620MHz; -
This paper discusses the key technologies in 3G/4G/5G (third generation/fourth generation/fifth generation) communication systems, and then discusses the differences in the antenna technologies adopted by them. After reading and studying a large number of papers on the key technologies of 3G/4G/5G communication system, here I make some analysis and summary of my own. With the rapid development of science and technology, mobile communication technology has undergone profound changes, from 1G to 2G, to 3G, and then to 4G and 5G. On December 4, 2013, the fourth generation of mobile communication 4G technology was officially operated in the Chinese market, which means that China's mobile communication industry has entered the 4G era. At this time, research institutes in various countries and world-renowned enterprises engaged in communication technology research have entered the research and development of the new generation of mobile communications, namely 5G (fifth generation mobile communication system). No matter which generation of communication system, the research technology is to analyze the characteristics of wireless communication channel to overcome the noise interference. A lot of researchers are now looking at Massive MIMO technology. How is it different from the antenna technology used in 3G/4G communication systems? Will it become the core technology of the next generation of wireless communications? 1 Key technologies of 3G/4G/5G Communication System 1.1 Key technologies of 3G Communication System Since the early 1990s, the mobile communication industry began to actively study the standards and technologies of the third generation of mobile communication. In January 2009, China's Ministry of Industry and Information Technology issued 3G licenses to China Mobile, China Telecom and China Unicom, indicating that China entered the ERA of 3G mobile communications. The third generation mobile communication system mainly includes WCDMA, CD-MA2000 and TD-SCDMA. Its key technologies include: A. Rake receiving technology; B. Channel coding and decoding technology; C. Power control technology; D. Multi-user detection technology; E. Smart antenna; F. Software radio. 1.2 Key technologies of 4G Communication System In December 2013, China officially entered the era of 4G (fourth generation mobile communication system) communication network. In 4G mobile communication system, OFDM(Orthogonal frequency Division multiplexing) technology is adopted. OFDM technology is due to its spectrum utilization
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It is widely regarded as high rate of 2 and good anti-multipath fading performance. In the future, RESEARCH related to OFDM technology will also be carried out in 5G communication networks. The main key technologies of 4G communication system include: a. OFDM technology; B. MIMO technology; C. Multi-user detection technology; D. Software radio; E. Smart antenna technology; F. IPv6 technology. China's Ministry of Industry and Information Technology has just issued 4G licenses to the three major operators, and they are still deploying their networks on a large scale with a small number of users. At this time, China Mobile said it will start the RESEARCH and development of 5G communication system. Analysts pointed out that the three major operators are participating in THE RESEARCH and development of 5G, one is to keep up with the changes of The Times, and the other is that the demand is faster than the technology development. Li Zhengmao, vice-president of China Mobile, said at the 2014 MWC in Barcelona: "China Mobile will fully support the development of 5G projects, hoping to lead the industry in THE development of 5G technology and the setting of technical standards." With the deepening of mobile communication technology research, the key support technologies of 5G will be gradually defined and enter the substantive standardization research and formulation stage in the next few years. The jury is still out on what core technologies will be used in the future. However, I have compiled a list of nine key technologies that have been the focus of discussion in various high-end mobile forums. A. Large-scale MIMO technology; B. Filter bank based multi-carrier technology; C. Full duplex technology; D. Ultra-dense heterogeneous network technology; E. Self-organizing network technology; F. Use of high frequency band; G. Software-defined wireless networks; H. Wireless access technology: (1) BDMA (Beam Split multiple Access technology)
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3 (2) NOMA (Non-orthogonal multiple Access technology) i. D2D (device-to-device) communication. Figure 1 is the layout of Massive MIMO antennas in 5G communication networks. I am studying Massive MIMO technology in my lab. Figure 1 shows users communicating with each other centered on a large-scale antenna. The performance of wireless communication systems is mainly restricted by mobile wireless channels. Wireless channel is very complex, and its modeling has always been a difficult point in system design. Generally, statistics are made according to the measured values of communication systems in specific frequency bands. Wireless fading channel is divided into large scale fading channel model and small scale fading channel model. The so-called large-scale fading model describes the field intensity variation over a long distance (hundreds or thousands of meters) between the transmitter and receiver, and reflects the rule that the received signal power changes with the distance caused by path loss and shadow effect. A small scale fading model describes the rapid fluctuations of the received field intensity over a short distance or time. The large scale fading channel model is caused by the influence of the surface contour (such as mountains, forests, buildings, etc.) between the receiver and the source. The small-scale fading channel model is caused by the multipath effect and doppler effect. If there are a large number of reflected paths but no LOS (direct signal) signal component, the small-scale fading is called Rayleigh fading, and the envelope of the received signal is described statistically by the Rayleigh probability density function. If LOS is present, the envelope is subject to Rician distribution. Multipath effect phenomena cause flat fading and frequency selective fading.
The Picture of 3G 4G LTE/5G Antenna
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