HOW TO AVOID ISSUES WITH RF & MICROWAVE PCB DESIGN
RF and microwave PCB with high frequency laminates can be difficult to design because of the sensitivity of the signals, especially compared to other digital signals.
Here are a few things to consider that ensure your design is efficient and minimizes the risk of failures, signal disruptions and other intrusions.
- RF and microwave signals are very sensitive to noise — much more sensitive than very high-speed digital signals. That means you’ll need to work to minimize noise, ringing and reflections while treating the whole system with care.
- Return signals take the path of least inductance — ground planes underneath your signal will make it easier to guarantee this path.
- Impedance matching is important. As the RF and microwave frequencies move higher, tolerance becomes smaller. Often, your PCB driver will need to be fixed, such as at 50 ohms, and that means 50 ohms out from the driver, during transmission and sending to the receiver.
- Transmission lines that bend due to routing constraints should use a bend radius that’s at least three-times larger than the center conductor width. This will minimize characteristic impedance.
- Return loss must be minimized, whether it’s caused by signal reflection or ringing. A return path will always be found, but your design should guide it and prevent bleeding of the return through the PCB’s many layers.