T.P. Potapova - Head of Sector, JSC «Kaluga Scientific Research Radio Engineering Institute». E-mail: ptp7@yandex.ru N.V. Toporkov - Ph. D. (Eng.), Head of Department, JSC «Kaluga Scientific Research Radio Engineering Institute». E-mail: ntoporkov@yandex.ru

High precision of radiation source direction measurement in a compact direction finding equipment can be achieved by processing of data of phase-difference measurements jointly with time-difference and amplitude-difference measurements. The objective of the paper is to review technical feasibility of efficient phase-difference and time-difference measuring instruments and to suggest methods of construction optimization for compact on-board direction finders and ground direction finding equipment. Potential precision referring to difference measurements of parameters of a radio signal received by two spaced receiving channels is defined by a measured parameter evaluation dispersion; the lower level of such dispersion is limited by Rao-Cramer inequality. To evaluate feasibility of theoretical evaluation of measurement precision in actual direction finders, given theoretical correspondences are compared to the data obtained from in-situ measurements with the use of real ELINT equipment components. The obtained data show a high concurrence between measurement precisions of difference parameters of two actual signals obtained from digital processing of experiment data with theoretically achievable measurement precisions. On the basis of expressions for evaluation dispersions of signals parameters difference, the correspondences were obtained for eval-uation dispersions of bearing defined by pulse reception time difference, phase difference and amplitude difference (proportion) of two received signals. Comparison of correspondences of maximum achievable values of RMS direction finding errors for direction finders of the three tradi-tional types enables to draw following conclusions: - with the given initial data a difference-time direction finder shows a worse direction finding precision than other direction finders at low signal-to-noise ratios, but it shows a better precision at higher levels of signal-to-noise ratios due to efficiency of measurements; - for difference-amplitude and difference-phase direction finders limitation of their direction finding precision is defined not by tem-perature noise of receiving channels, but structural design that limits identity of amplitude-frequency-space and phase-frequency-space characteristics of the used receiving channels. Along with this, difference-phase direction finders show a higher measurement precision even with a small antenna base. Variants for optimization of air based and ground based direction finders architecture based on the attainable DF accuracy are offered in the article. Combination of phase-difference and time difference DF is used in air based direction finding equipment, that allows to reduce number of receiving antennas to 3, providing high precision DF in azimuth plane in decimeter-centimeter frequency band. Achievable DF RMS for 3 channel air direction finder with overlapping through combining phase difference with time difference measurements and the 14 m. maximum antenna base will be equal to value from 0,7° (at 0,1 GHz) to 0,06° (at 5 GHz). The possibility of combining different amplitude-difference methods with phase-difference methods trough implementation of additional receiving channel directed similar to summary channel amplitude direction finder is reviewed. Achievable DF RMS of ground directional finder using combination of amplitude-difference and phase-difference measurements will be 5 times less comparing with RMS of directional finder using only amplitude-difference measurements.

 

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