
142 Analog Circuits Cookbook
even-order harmonics does not affect the measured value of the funda-
mental, but the same is not true of odd harmonics. However, whereas 10%
of third harmonic will give an error in a peak reading somewhere between
0 and 10%, for an average-responding detector, the error is between zero
and only 3.3%, i.e. one-third of the harmonic amplitude. For the fifth
harmonic, the maximum possible error is only one-fifth and so on for higher
odd harmonics. So an average-responding circuit is really quite useful.
Simple VSWR bridge
A VSWR bridge enables one to measure the reflection coefficient at an
rf interface, and hence