Designing a WiFi Transceiver
To create a good RF layout, you must have a good understanding of supply routing, board stack up and grounding. There are a number of proven design guidelines for power supply routing, grounding and supply bypassing techniques, to improve the performance of an RF design.
Unfortunately, when embedded engineers are designing RF layouts, the implementation aspect is usually an afterthought. If you don’t take care, the circuit supply voltage can easily become noisy and corrupted, affecting the performance of the RF circuit.
WLAN routing usually employs a four layer board. Typically, the top layer is used for RF routing and for placing components, the second layer to place the ground plane, the third layer for the power routing and whatever remains is placed in the last layer. The ground plane in the second layer provides controlled impedance to the signal paths. Custom power supplies are usually employed for high load WiFi transceivers.
The combination of a good supply decoupling technique, a sound PCB stack and careful routing provides a strong foundation to the RF design. Embedded engineers have to be careful here because there are several other factors that might reduce performance. Routing and grounding are critical in WLAN board fabrication and layout. Custom power supply is one of the determinants.