Method for suppressing narrowband electromagnetic interference in radio wave detection tools with broadband sounding

Abstract

Background. Buried radio-wave detectors (RWDs) of the meter wavelength range use broadband probing signals to realize their positive qualities. For broadband receivers (RXs) of RWDs, an urgent task is to protect them against the effects of extraneous electromagnetic interference, including within the RWDs operating frequency band. This paper considers a method for suppressing narrow-band interference; this method consists in cutting them out of the spectrum of a broadband useful RWD signal. With this method, separate narrow-band receive channels are formed in RWDs; each of them can be turned off when interference appears in it. The problem to be solved is to provide the minimum cutout frequency band of each frequency channel, at the same time, wide enough to provide the required signal level and a sufficient signal-to-noise ratio in each frequency channel. Materials and methods. The article uses the previously obtained models of surface propagation of electromagnetic waves to estimate the parameters of RWD signals and the wellknown model of space interference, which is the main source of receiver noise. Results. The conditions have been determined under which TX of RWDs meets the requirements of the standards limiting the level of its radiation. At the same time, in the worst conditions of propagation of electromagnetic waves (in case of wet ground), the minimum levels of a signal received by RX are determined; the maximum levels of the RX interference and the signal-to-noise ratio for various conditions are determined. The limitation of the TX radiation level, the presence of RX interference and the intent to increase the length of the protected boundary between the TX and RX results in the need to expand the bandwidth of frequency channels in order to provide them with the required signal-to-noise ratio. Conclusions. The results obtained in this work make it possible to explicitly determine the minimum bands of frequency channels that are turned off when narrow-band electromagnetic interference appears in them, providing the required signal / noise ratios at given distances between the TX and RX in the RWD operating frequency range.

Keywords

• splitting a broadband signal band into frequency bands; cutting out the frequency bands affected by interference; signal / noise ratio in frequency channels; minimum frequency channel bandwidth