Modulation impact on quasi-peak detector response

An analysis of the fundamental quasi-peak (QP) detector circuit as used in EMI receivers up to 1 GHz was performed, using computer simulation and partly experimental verification. The typical time constants have been depicted from the basic CISPR standard. This investigation focuses not on the overall receiver performance but rather only on the direct demodulated audio/modulation impact of the stage. One interesting finding is the effect of the duty cycle of the pulse rather than the repetition frequency. On the other hand we could prove the well known weighted “limits relaxation” with respect to the full peak value for slow pulses. Checking the worst case response waiting time of the detector leads to about 70% longer times than the usually assumed 1s period. The characteristic of the QP detector with idealized pulses has been testing experimentally. Good agreement (10%) has been achieved between simulation and experiment. A QP versus peak detector discussion is given