High-frequency circuit boards refer to special circuit boards with higher electromagnetic frequencies, and are one of the most difficult boards.

So, what aspects should we pay attention to when designing high-frequency circuit boards?

1. Consider how to avoid high-frequency interference?

Avoiding high-frequency interference means minimizing the interference of the electromagnetic field of high-frequency signals, also known as crosstalk. This can be done by increasing the distance between high-speed signals and analog signals, and also paying attention to the noise interference of digital ground on analog ground.

2. How to choose PCB board?

The selection of PCB material must strike a balance between meeting design requirements, mass production and cost. Design requirements include electrical and mechanical parts.

3. How to solve the signal integrity problem?

Signal integrity is basically an impedance matching problem, which can be solved by termination and adjusting the topology of the trace.

4. How to achieve differential wiring for a clock signal line with only one output end?

To use differential wiring, it must be that both the signal source and the receiving end are differential signals. Therefore, differential wiring cannot be used for a clock signal with only one output end.

5. How to achieve differential wiring?

One is that the lengths of the two lines should be as equal as possible, and the other is that the distance between the two lines (this distance is determined by the differential impedance) should remain constant, that is, they should remain parallel. There are two ways to be parallel, one is that the two lines run on the same routing layer, and the other is that the two lines run on the upper and lower adjacent layers.

6. Is it possible to add a matching resistor between the differential line pairs at the receiving end?

Matching resistors are usually added between the differential line pairs at the receiving end, and their values ​​should be equal to the differential impedance value, so that the signal quality will be better.

7. Why should the wiring of differential pairs be close and parallel?

The so-called appropriate proximity is because this distance affects the value of differential impedance, which is an important parameter in the design of differential pairs. Parallelism is also required because the consistency of differential impedance must be maintained.

8. How to deal with some theoretical conflicts in actual wiring

1. Basically, it is right to separate the analog/digital ground. Be careful not to cross the separation point as much as possible, and do not make the return current path of the power supply and signal too large.

2. The crystal oscillator is an analog positive feedback oscillation circuit. To have a stable oscillation signal, the distance between the crystal oscillator and the chip must be as close as possible.

3. It is true that there are many conflicts between high-speed wiring and EMI requirements. It is best to use the techniques of arranging wiring and PCB stacking to solve or reduce EMI problems, such as routing high-speed signals on the inner layer.

The above are the 8 aspects that should be paid attention to in the design of high-frequency circuit boards compiled by the editor. I believe you should now have a deeper understanding of high-frequency boards!

KKPCB conducts research on special processing technologies such as ordinary double-sided boards, thick copper circuit boards, high-frequency circuit boards, HDI circuit boards, rigid-flexible circuit boards, FPC flexible boards, buried blind hole circuit boards, and IC carrier boards. Provides PCB design, PCB layout, PCB prototyping and PCB assembly services.