1. Interference between digital circuit modules and analog circuit modules If the analog circuit (RF) and the digital circuit work separately, they may work well separately. However, once the two are placed on the same circuit board and work together using the same power supply, the entire system is likely to be unstable. This is mainly because digital signals frequently swing between the ground and the positive power supply (>3 V), and the cycle is particularly short, often in the nanosecond level. Due to the large amplitude and short switching time. These digital signals contain a large number of high-frequency components that are independent of the switching frequency. In the analog part, the signal transmitted from the wireless tuning loop to the receiving part of the wireless device is generally less than lμV. Therefore, the difference between the digital signal and the RF signal can reach 120 dB. Obviously, if the digital signal cannot be well separated from the RF signal. Weak RF signals may be damaged, which will deteriorate the performance of wireless devices or even prevent them from working at all. 2. Noise interference from the power supply RF circuits are quite sensitive to power supply noise, especially glitch voltages and other high-frequency harmonics. Microcontrollers suddenly absorb most of the current for a short period of time in each internal clock cycle, because modern microcontrollers are manufactured using CMOS technology. Therefore, assuming a microcontroller runs at an internal clock frequency of 1MHz, it will extract current from the power supply at this frequency. If proper power supply decoupling is not taken, voltage glitches on the power supply line will inevitably occur. If these voltage glitches reach the power pins of the RF part of the circuit, it may cause work failure in severe cases. 3. Radiated interference of antenna to other analog circuit parts In PCB circuit design, there are usually other analog circuits on the board. For example, many circuits have analog-to-digital conversion (ADC) or digital-to-analog converter (DAC). The high-frequency signal emitted by the antenna of the RF transmitter may reach the analog input of the ADC. Because any circuit line may emit or receive RF signals like an antenna. If the processing of the ADC input is not reasonable, the RF signal may self-excite in the ESD diode of the ADC input. This causes ADC deviation. RF circuit design principles and solutions 1. RF Layout Concept When designing the RF layout, the following general principles must be met as priority: Isolate the high-power RF amplifier (HPA) and the low-noise amplifier (LNA) as much as possible. Simply put, keep the high-power RF transmitting circuit away from the low-power RF receiving circuit: Make sure that there is at least one whole ground in the high-power area of the PCB board, preferably without vias on it. Of course, the larger the copper foil area, the better; Circuit and power supply decoupling is also extremely important; RF output usually needs to be kept away from RF input; Sensitive analog signals should be kept as far away from high-speed digital signals and RF signals as possible. 2.Design principles for physical and electrical partitions Design partitions can be broken down into physical partitions and electrical partitions. Physical partitions mainly involve component layout, orientation, and shielding, etc.; electrical partitions can be further broken down into power distribution, RF routing, sensitive circuits and signals, and grounding. 3. Physical partitioning principles Principles of component location layout. Component layout is the key to achieving an excellent RF design. The most effective technique is to first fix the components on the RF path and adjust their direction to minimize the length of the RF path and keep the input away from the output. And separate the high-power circuit and the low-power circuit as far as possible. PCB stacking design principles. The most effective circuit board stacking method is to arrange the main ground plane (main ground) on the second layer under the surface layer, and arrange the RF line on the surface layer as much as possible. Minimize the size of the vias on the RF path, which can not only reduce the path inductance, but also reduce the virtual solder joints on the main ground, and reduce the chance of RF energy leaking to other areas in the stacked board. RF devices and their RF wiring layout principles. In physical space, linear circuits such as multi-stage amplifiers are usually sufficient to isolate multiple RF areas from each other, but duplexers, mixers, and intermediate frequency amplifiers/mixers always have multiple RF/IF signals interfering with each other. Therefore, care must be taken to minimize this effect. RF and IF traces should be crisscrossed as much as possible, and a ground plane should be placed between them as much as possible. Correct RF paths are very important to the performance of the entire PCB, which is why component layout usually takes up most of the time in cell phone PCB design. Design principles to reduce interference coupling between high/low power devices. On a cell phone PCB, it is usually possible to place the low noise amplifier circuit on one side of the PCB and the high power amplifier on the other side, and finally connect them to the antenna on the RF and baseband processor sides on the same side through a duplexer. Skills are needed to ensure that through holes do not transfer RF energy from one side of the board to the other. A common technique is to use blind vias on both sides. The adverse effects of through holes can be minimized by arranging through holes in areas on both sides of the PCB that are not subject to RF interference. The design of RF circuits requires designers to have certain practical experience and engineering design capabilities. Some of the experiences summarized in this article can help RF integrated circuit developers shorten the development cycle. Avoid unnecessary detours and save manpower and material resources. As an important support for electronic components and electronic devices, PCB circuit boards play a very important role in the field of electronics industry. Industry insiders call it the "electronic aircraft carrier". With the development of science and technology, the application scope of PCB circuit boards will become more and more extensive. To a certain extent, the production technology level of circuit boards has become an important indicator to measure the level of science and technology of a country. In order to better capture the world's leading PCB manufacturing technology and fully display the manufacturing level of the domestic circuit board industry, from August 30 to September 1, the 2016 Shenzhen International Circuit Board Procurement Exhibition (CS Show 2016) will officially kick off at the Shenzhen Convention and Exhibition Center, sounding the annual clarion call for the PCB industry to take off. Physical partition principle Component location layout principle. Component layout is the key to achieve an excellent RF design. The most effective technology is to first fix the components located on the RF path and adjust its direction to minimize the length of the RF path and keep the input away from the output. And separate the high-power circuit and the low-power circuit as far as possible. PCB stacking design principle. The most effective circuit board stacking method is to arrange the main ground plane (main ground) on the second layer under the surface, and arrange the RF line on the surface as much as possible. Minimize the size of vias on the RF path, which not only reduces the path inductance, but also reduces the number of cold solder joints on the main ground and reduces the chance of RF energy leaking into other areas of the stacked board. Principles of RF device and RF wiring layout. In physical space, linear circuits such as multi-stage amplifiers are usually sufficient to isolate multiple RF areas from each other, but duplexers, mixers, and intermediate frequency amplifiers/mixers always have multiple RF/IF signals interfering with each other. Therefore, this effect must be carefully minimized. RF and IF traces should be crisscrossed as much as possible, and a ground plane should be placed between them as much as possible. The correct RF path is very important to the performance of the entire PCB, which is why component layout usually takes up most of the time in cellular phone PCB design. Design principles to reduce interference coupling between high/low power devices. On a cellular phone PCB, the low noise amplifier circuit can usually be placed on one side of the PCB, and the high power amplifier on the other side, and finally connected to the antenna on the RF end and the baseband processor end on the same side through a duplexer. Skills are required to ensure that the through hole does not transfer RF energy from one side of the board to the other side. A common technique is to use blind vias on both sides. The adverse effects of through holes can be minimized by arranging the through holes in areas where both sides of the PCB are not subject to RF interference. The design of RF circuits requires designers to have certain practical experience and engineering design capabilities. Some of the experiences summarized in this article can help RF integrated circuit developers shorten the development cycle. Avoid unnecessary detours and save manpower and material resources. As an important support for electronic components and electronic components, PCB circuit boards play a very important role in the electronics industry. Industry insiders call it the "electronic aircraft carrier." With the development of science and technology, the application scope of PCB circuit boards will become more and more extensive. To a certain extent, the production technology level of circuit boards has become an important indicator to measure the level of science and technology of a country. In order to better capture the world's leading PCB manufacturing technology and fully demonstrate the manufacturing level of the domestic circuit board industry, the 2016 Shenzhen International Circuit Board Procurement Exhibition (CS Show 2016) will officially kick off at the Shenzhen Convention and Exhibition Center from August 30 to September 1, sounding the annual clarion call for the PCB industry to take off. Physical partition principle Component location layout principle. Component layout is the key to achieve an excellent RF design. The most effective technology is to first fix the components located on the RF path and adjust its direction to minimize the length of the RF path and keep the input away from the output. And separate the high-power circuit and the low-power circuit as far as possible. PCB stacking design principle. The most effective circuit board stacking method is to arrange the main ground plane (main ground) on the second layer under the surface, and arrange the RF line on the surface as much as possible. Minimize the size of vias on the RF path, which not only reduces the path inductance, but also reduces the number of cold solder joints on the main ground and reduces the chance of RF energy leaking into other areas of the stacked board. Principles of RF device and RF wiring layout. In physical space, linear circuits such as multi-stage amplifiers are usually sufficient to isolate multiple RF areas from each other, but duplexers, mixers, and intermediate frequency amplifiers/mixers always have multiple RF/IF signals interfering with each other. Therefore, this effect must be carefully minimized. RF and IF traces should be crisscrossed as much as possible, and a ground plane should be placed between them as much as possible. The correct RF path is very important to the performance of the entire PCB, which is why component layout usually takes up most of the time in cellular phone PCB design. Design principles to reduce interference coupling between high/low power devices. On a cellular phone PCB, the low noise amplifier circuit can usually be placed on one side of the PCB, and the high power amplifier on the other side, and finally connected to the antenna on the RF end and the baseband processor end on the same side through a duplexer. Skills are required to ensure that the through hole does not transfer RF energy from one side of the board to the other side. A common technique is to use blind vias on both sides. The adverse effects of through holes can be minimized by arranging the through holes in areas where both sides of the PCB are not subject to RF interference. The design of RF circuits requires designers to have certain practical experience and engineering design capabilities. Some of the experiences summarized in this article can help RF integrated circuit developers shorten the development cycle. Avoid unnecessary detours and save manpower and material resources. As an important support for electronic components and electronic components, PCB circuit boards play a very important role in the electronics industry. Industry insiders call it the "electronic aircraft carrier." With the development of science and technology, the application scope of PCB circuit boards will become more and more extensive. To a certain extent, the production technology level of circuit boards has become an important indicator to measure the level of science and technology of a country. In order to better capture the world's leading PCB manufacturing technology and fully demonstrate the manufacturing level of the domestic circuit board industry, the 2016 Shenzhen International Circuit Board Procurement Exhibition (CS Show 2016) will officially kick off at the Shenzhen Convention and Exhibition Center from August 30 to September 1, sounding the annual clarion call for the PCB industry to take off.
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