Several Points of RF Circuit Board Design (1)

Although there are many theoretical uncertainties in radio frequency (RF) circuit board design, there are many rules for RF circuit board design. However, when it comes to actual design, the real trick is how to compromise these laws when they cannot be implemented due to various constraints. This article will focus on various issues related to RF board partition design.

1. Types of Micro Vias

Circuits of different natures on a circuit board must be separated, but connected in the best possible way without EMI, which requires the use of microvias. Usually the diameter of micro vias is 0.05mm~0.20mm. These vias are generally divided into three categories, namely blind vias, buried vias and through vias. Blind holes are located on the top and bottom surfaces of the printed circuit board and have a certain depth for the connection of the surface layer and the underlying inner layer. The depth of the hole usually does not exceed a certain ratio (diameter). Buried vias refer to connection holes located in the inner layer of the printed circuit board, which do not extend to the surface of the circuit board. The above two types of holes are located in the inner layer of the circuit board, and are completed by the through hole forming process before lamination. During the formation of the via hole, several inner layers may be overlapped. The third type is called through-hole, which penetrates the entire circuit board and can be used for internal interconnection or as an adhesive positioning hole for components.

2. Use Partitioning Techniques

When designing an RF circuit board, the high-power RF amplifier (HPA) and the low-noise amplifier (LNA) should be isolated as much as possible. Simply put, the high-power RF transmitter circuit should be kept away from the low-noise receiver circuit. This can be done easily if there is a lot of space on the PCB board. But usually when there are many components, the PCB manufacturing space becomes very small, so this is difficult to achieve. You can place them on both sides of the PCB board, or have them work alternately instead of simultaneously. High-power circuits may also sometimes include RF buffers and voltage-controlled oscillators (VCOs).

Design partitions can be divided into physical partitioning and electrical partitioning. Physical partitions mainly involve issues such as component layout, orientation and shielding. Electrical partitions can be further divided into partitions such as power distribution, RF routing, sensitive circuits and signals, and grounding.