How to Improve Return Loss or VSWR

In this post we show a simple technique to improve the return loss of an RF component like a mixer or amplifier.

A good VSWR to aim for is at least 1.5. This is equal to a return loss of 14 dB or greater.

The easiest way to improve return loss is to add an attenuator. In the example below an attenuator is added between the input and amplifier to improve its return loss.

As an example, if the return loss of the amplifier is 4 dB, use the calculator below to see that adding a 5 dB attenuator will improve the RL to 14 dB.

The attenuator will reduce the cascaded gain by 4 dB so that will have to be accounted for.

The amplifier can be substituted with a mixer. For instance the LO port can have a VSWR as high as 4. This is too high and presents a poor match. The RL is 4.44 dB, Adding a 5 dB attenuator will increase the RL to 14.44 dB and a VSWR of 1.47.