A solid RF layout begins with understanding the fundamentals of board stack-up, supply routing, and grounding. This discussion addresses these fundamentals, and offers some practical, design-proven guidelines on power supply routing, supply bypassing, and grounding techniques to maximize the performance of any RF design. A practical
example of controlling PLL spur levels is discussed, as PLL spurs are particularly sensitive to supply decoupling, grounding, and filter component placement. The MAX2827 802.11a/g transceiver reference design PCB layout is used
for illustration.
Part 1: Fundamentals of Supply Routing and Bypassing
When designing RF circuits, the implementation and layout of the power supply section are often treated as an afterthought to the high-frequency signal path. Without careful consideration, it is easy for the supply voltages around the circuit to become corrupted and noisy, thus adversely affecting the system performance of the RF circuitry. Proper
planning of the PCB layer stack-up, VCC routing with a star topology, and proper decoupling of the VCC pins will help achieve the best RF performance possible.