What should be paid attention to in the amplifier design of RF circuit PCB

明天你好123

What should be paid attention to in the amplifier design of RF circuit PCB [Copy link]

 

In the microwave frequency band, how to ensure that the output signal of the amplifier will not be fed back to the input end? What should be paid attention to when connecting multi-stage amplifiers? Is there any expert who can explain it?

qwqwqw2088

The topic is RF circuit PCB design. The content is RF circuit principle design. One paper may not be enough to solve it. A specific problem should be raised for analysis.

chunyang

The output of the amplifier will not be fed back to the input as long as there is no feedback loop. However, when the frequency is high, attention should be paid to the feedback caused by spatial induction. This requires strict control of the size of the input signal connection line and shielding when necessary. The cascade of amplifiers requires attention to impedance matching and suppression of signal reflection, etc., and requires strict control of distributed parameters and interconnection of transmission lines.

明天你好123

qwqwqw2088 posted on 2019-1-10 15:00 The topic is RF circuit PCB design. The content is RF circuit principle design. One paper may not be able to handle it. A specific problem should be raised for analysis

It does not refer to the design of the amplifier. It is to use ready-made modules to build a circuit. When drawing the PCB, do you need to consider whether the amplifier output signal is coupled to the input end?

btty038

To achieve isolation and shielding between each stage of amplifier, there is nothing else, especially the last two stages. You need to see how to apply the structure.  

btty038

chunyang posted on 2019-1-10 16:49 As long as there is no feedback loop, the output of the amplifier will not be fed back to the input end, but when the frequency is high, attention should be paid to the feedback caused by spatial induction, which requires strict...

Really a big guy

明天你好123

btty038 posted on 2019-1-10 18:00 He is really a big shot

Is there any good way to isolate the amplifier? Is it cavity isolation?

明天你好123

chunyang posted on 2019-1-10 16:49 As long as there is no feedback loop, the output of the amplifier will not be fed back to the input, but when the frequency is high, attention should be paid to the feedback caused by spatial induction, which requires strict...

Thank you! Very thorough explanation

明天你好123

btty038 Published on 2019-1-10 17:59 To achieve isolation and shielding between each stage of amplifiers, there is nothing else, especially the last two stages, you need to see how to apply the structure

Can I ask you for help. In the actual process of RF circuit boards, can digital circuits pass through the analog ground? Someone told me not to pass through the analog ground, and I also saw some comments on the Internet saying that it is best to put the digital circuit transmission layer between the inner electrical layers.

chunyang

Hello tomorrow 123 Posted on 2019-1-10 20:47 Can I ask you something? In the actual process of RF circuit board, can the digital circuit pass through the analog ground? Someone told me not to pass through the analog ground, but also see...

It is not absolutely impossible, but it must be handled very carefully. The split ground plane may cause problems, but it is acceptable if it is handled well. Generally speaking, the more complete the ground plane, the better.

chunyang

Hello tomorrow 123 Published on 2019-1-10 20:06 What is a good way to isolate the amplifier? Is it cavity isolation?

The cavity is an integrated shielding structure, which is commonly used in RF systems.