Dynamics of autodyne response formation in microwave generators

The paper presents results of studying the dynamics of autodyne response formation when switching on a radio-pulse microwave generator which is subject to the influence of its own reflection radiation. Basic relations for a step-wise calculation of autodyne response as a function of time delay, autodyne response time constant, distortion parameter and intrinsic parameters of the self-oscillating system are obtained. Calculation and analysis of peculiarities of autodyne signal generation by radio-pulse oscillator are conducted for the cases of motionless and moving reflecting object under relatively low, medium and high inertia properties of the oscillator if compared to the propagation time of the reflected radiation. Experimental research results that confirm conclusions of theoretical analysis are obtained for a common hybrid-integrated autodyne TIGEL-08 module of the 8-mm frequency-range implemented on a planar two-meza Gunn diodes and the same module stabilized by the external high-Q resonator. © 2013 Allerton Press, Inc

Analysis of signals of stabilized autodynes

Results of the autodyne signal analysis of the self-oscillating systems stabilized in frequency by the external high-quality cavity are given. The coupling between the main and stabilizing cavities is realized on the basis of a pass-reflective filter with a resistive link. Mathematical equations are obtained describing an autodyne response onto impact of the own radiated signal reflected from a target. The analysis of phase, amplitude, frequency and amplitude-frequency characteristics of the autodyne system is fulfilled. The calculation of an autodyne signal spectrum is discussed. A new type of nonlinear distortions of an autodyne signal is examined, which is caused by a frequency dispersion of an oscillating system of the stabilized autodyne. Advantages of the stabilized autodyne compared to the usual single-tuned autodyne oscillator are shown

Modulation characteristics of microwave autodyne oscillators

General relations for the analysis of autodyne and modulation characteristics are obtained in the form of differential equations with the retarded argument. Solutions for characteristics of frequency response of autodyne variations of the oscillation amplitude and phase as well as the auto-detecting signal of UHF oscillator under influence of the proper reflected radiation are derived. The solution of the same equation system is given for frequency responses of the modulation deepness of oscillation amplitude and frequency as well as the auto-detecting signal in the case of the reflection factor modulation by the high-frequency signal. Calculations of autodyne and modulation characteristics are fulfilled at different values of inherent parameters of UHF oscillators. Non-isochronous and non-isodromous properties of autodyne oscillators are investigated. Phenomena of frequency auto-detecting are considered. A method for dynamic properties determination is substantiated according to its modulation characteristics at the oscillation amplitude registration. The results of theoretical analysis are confirmed by experimental data obtained on the example of hybrid-integrated oscillator of 8mm-range on the Gunn diode

Theory of stabilized autodyne oscillators at the large reflected signal

Research results on autodyne oscillator stabilized by an external high-Q cavity are presented for the case of the large reflected signal, when amplitude of the reflected wave is commensurable with amplitude of natural oscillations. Expressions describing an autodyne response of the oscillator on the influence of the proper radiation reflected from a target are obtained. Calculations of amplitude, frequency and spectral characteristics of the autodyne system are performed. Conditions of exact tuning of the stabilized cavity are determined. Investigations of stabilized autodyne parameters at small distance to the reflected object are provided. It is shown that to expand the dynamic range of the autodyne system it is expedient to use the large coupling between cavities. Recommendations concerning practical application of the obtained results in the short-range radar are given

Determination of autodyne oscillator parameters by the beating method

The research results of oscillator internal parameters influence the features of dynamic autodyne characteristics formation in the case of external oscillator signal influence are presented. The equivalent circuit with a single-circuit oscillating system is considered as a model of the autodyne oscillator. Abbreviated equations are obtained by an averaging method and then they are linearized for small disturbances in a vicinity of the steady-state mode. The obtained characteristics for the beating mode are compared with characteristics of autodynes for short-range radar technology. The essential differences in behavior of the oscillator with acting the external oscillator and the oscillator with acting the own reflected signal have been found. The physical sense of the frequency dispersion phenomenon for the autodyne frequency deviation in the vicinity of hypothetical “zero” beating is discovered. The research results of dynamic autodyne characteristics in the frequency conversion mode of signals modulated on amplitude or frequency are given. It is shown that to suppress the spurious harmonics of the beating frequency, it is advisable to take additional measures for generated frequency stabilization in autodyne frequency converters, for instance, using the external feedback in the oscillator or using the external high-Q resonator. The adequacy of theoretical conclusions is confirmed by results of experimental investigations of the hybrid-integrated module of 8 mm-range made on the basis of the planar two-meza Gunn diode. Oscillator characteristics obtained by the beating method are compared with results of investigation fulfilled with the help of modulation characteristics. It is shown that errors in experimental determination of dynamic characteristics of autodyne oscillators caused by frequency limitations of a pin-diode typical for the modulation characteristic method can be eliminated. Problems of practical application of obtained results in real radar systems using autodyne oscillators are discussed

Dynamic features of autodyne signals

On the example of classical single-circuit oscillator influenced by reflected signal, a solution of system of differential autodyne equations is obtained by the high-order quasi-static approximation method for the general case of arbitrary delay time of the reflected signal, fast motion of a point-sized reflecting object, and inertia of the oscillator itself. The special features of forming the autodyne response are considered with allowance for the oscillator inertia and its internal parameters, including anisochronous and non-isodromic properties, and dependences of the signal waveform, constant component, and nonlinear distortion coefficient on the distance and the direction of object motion are established. © 2013 Springer Science+Business Media New York

Moving Object Signal Analysis of Autodyne Radars with Linear Types of Frequency

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

Autodyne sensor signals with amplitude-frequency modulation of radiation

A mathematical model of an autodyne oscillator with a combined amplitude-frequency modulation, which is under the influence of its own radiation reflected from the target, is developed. The main relations are obtained for analyzing the autodyne response of a single-circuit oscillator depending on the delay time of the radiation reflected from the target with an arbitrary law of simultaneous amplitude and frequency modulation. The characteristics of the amplitude selection of signals, as well as their temporal and spectral characteristics, are calculated for harmonic amplitude-frequency modulation. The features of signal formation are established for various values of the amplitude and frequency modulation parameters and the feedback parameter of the “oscillator—target” autoparametric system. The results of experimental studies, performed on a Tigel-0.8M hybrid-integrated Ka-band oscillator module with a Gann mesa-planar diode, confirmed the findings of the theoretical analysis. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.This research was funded by the Ministry of Science and Higher Education of the Russian Federation (agreement no. 075-11-2019-052 of 13 December 2019)