Radio frequency (RF) board design is often described as a "black art" because of its many theoretical uncertainties, but this view is only partially correct. RF board design also has many guidelines that should be followed and should not Neglected rules. However, in practical design, the really practical technique is how to compromise these guidelines and rules when they cannot be accurately implemented due to various design constraints. Of course, there are many important RF design topics worth discussing, including impedance and impedance matching, insulation materials and laminates, and wavelength and standing waves, so these have a great impact on the EMC and EMI of mobile phones:
Separate the high-power RF amplifier (HPA) from the low-noise amplifier (LNA) as much as possible
Simply put, the high-power RF transmit circuitry is kept away from the low-power RF receive circuitry. There are many functions of mobile phones and many components, but the PCB space is small, and the design process of the wiring is considered to be the highest, and all of these requirements for design techniques are relatively high. At this point it may be necessary to design a four- to six-layer PCB so that they work alternately instead of working at the same time. High power circuits can sometimes also include RF buffers and voltage controlled oscillators (VCOs). Make sure that there is at least one whole piece of high power area on the PCB. It is better to have no vias on it. Of course, the more copper is, the better. Sensitive analog signals should be as far away as possible from high-speed digital and RF signals.