Automatic Impedance Matching in RF Design (.PDF Download)
Impedance (Z) matching is an essential part of most RF circuit design. Regardless of what you’re designing, getting as much power to a load is a top target. Impedances must be matched to transfer the maximum amount of signal power between stages. And in power amplifiers (PAs), impedance matching is critical to getting the maximum power to the final load and maintaining PA linearity. Impedance matching to an antenna in a receiver or transmitter is an essential process.
Some loads are constant; thus, a single fixed Z-matching circuit can be used. But in other applications, that final load may change, or the frequency of operation will change, meaning that a fixed Z-match circuit will not produce the desired results. For these applications, a variable matching network that you can adjust is needed. Better still is a variable and automatic Z-match circuit that adjusts itself to the immediate load or frequency conditions.