Filtering a periodic envelope of a radio signal

Abstract

In a number of radionavigation and engineering-diagnostics problems, it is necessary to estimate the shape of a periodic radio-signal envelope during the handling of vibroacoustic and hydroacoustic signals, etc. The well- known methods for filtering an envelope (see [1, 2]) are effective only for specific a priori information on the phase of the signal. Thus, for example, synchronous storage of a detected signal is invariant with respect to the phase of the radio signal, but it is not effective in the case of a known or constant initial phase, since nonlinear transformation of the additive mixture of useful signal + noise is performed before storage (see [1]). Coherent storage, which is optimal in the sense of the maximum signal/noise ratio (see [1]), also allows an asymptotically optimal estimate of a periodic envelope to be obtained in the sense of maximum likelihood, but it imposes rigorous requirements on the constancy of the value of the initial phase of the signal.

In the present work a filter is synthesized which allows a quasi-optimal (in the sense of the maximum-likelihood criterion) estimate to be obtained of a periodic envelope while having the capacity of easily readjusting when the behavior of the initial phase of the signal changes.