Active Filters for Measuring Time-Domain Frequency Stability

The instrumentation for measuring the filter variance is simple and low cost. An assembly of the test set known as PCC-1 for evaluaig the time-domain frequency stability of signal generators was developed in the Chengdu Institute of Radio Engineering. It also includes specially designed active filters for measuring the filter variance. Experimental results are presented which show that the high-pass filter variance is a good estimation of the Allan variance.