Analog Circuits Cookbook, 2nd Edition

4

Measurements (rf)

Measuring detectors (Part 1)

Amplitude measurements on rf signals

Amplitude measurements on rf signals require a detector of some sort. Many types exist and the following two articles examine the performance of some of them.

A detector of some sort is required in order to measure the amplitude of an ac signal. In the case of an amplitude modulated carrier, e.g. a radio wave, measuring its amplitude on a continuous basis will extract the information which it carries. One of the earliest detectors was the coherer, a glass tube filled with iron filings which, when an rf current passed through them, tended to stick together. This reduced the resistance in the circuit containing a local battery, causing it to operate the tape-marking ...