Анализ сигналов от движущегося объекта автодинных локаторов с линейными видами модуляции частоты

Abstract

Представлены результаты исследования особенностей формирования сигналов автодинной системы ближней радиолокации с линейной частотной модуляцией для движущегося отражающего объекта. Получены основные соотношения и результаты вычисления автодинных сигналов для случаев, когда продолжительность их периода значительно больше времени запаздывания отраженного излучения, а также для случаев, когда данное неравенство не выполняется. Рассмотрены особенности сигналов для приближающегося и удаляющегося объекта. Экспериментальные данные получены на генераторе, выполненном на диоде Ганна 8‑мм диапазона с перестройкой частоты при помощи варикапа.

General equations for analysis of the signal formation peculiarities are obtained for the autodyne short-range radar (ASRR) systems both for the case of the fixed and moving reflecting object, using arbitrary types of frequency modulation (FM). The developed mathematical model anticipates the interaction analysis of ASRR with the reflected emission at arbitrary ratio of the delay time τ of the reflected emission and the autodyne signal period Ta. Signal features for the oncoming and outcoming object are considered. The experimental data are obtained on the oscillator made on the 8mm-Gunn diode with the varicap frequency tuning. The fulfilled calculations and experimental investigations of ASRR signals for linear types of FM show that the autodyne frequency both for the moving and fixed reflector exactly corresponds to the frequency of transformed signal obtained in the case of the homodyne system. However, the presence of autodyne signal distortions requires the account in the signal processing devices under conditions, when the distance to the reflecting object is small, and the feedback parameter Cfb is commensurable to 1. The obtained results of autodyne characteristic research in the case when the autodyne signal period is commensurable or even less than delay time show that the distortion of autodyne signal at hypothetical keeping of the reflected amplitude decreases with distance growth. The calculations show that if the feedback parameter exceeds some boundary value even in several times, in higher operation zones of ASRR with FM operation can be provided with formation of quasi-harmonic signals. The obtained analysis results are developed and supplemented of results of known investigations, which were published in previous papers. Revealed regulations of signal formation in ASRR with FM have enough general characteristics and physical interpretation on the base of the step method known in systems with delay. In this connection, the obtained results in this paper can be used in the calculations of autodyne system signals made on semiconductor laser modules with FM.