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

Autodyne signal features of frequency-locked microwave oscillators

The research results on the autodyne signal formation in microwave oscillators, which are exposed under the impact of the proper reflected emission and, at the same time, of the external frequency-locked signal are presented. The basic relations are obtained for signal analysis under the condition of the quasistatic target movements. The theoretical research results are confirmed by experimental data obtained on the example of an oscillator made on the basis of the 8mm-range Gunn diode

Dynamic characteristics of frequency-locked autodynes

The results of research into the dynamic characteristics of microwave oscillators under the influence of both their own reflected radiation and external synchronising effect are presented. The basic relations for the analysis of signals during fast movement of the target are obtained, when the signal period is comparable to the autodyne response time constants. The results of numerical modelling of the characteristics are confirmed by the experimental data obtained on the example of an oscillator based on the Gunn diode of the 8-mm range

The impact of resonator detuning on autodyne characteristics of stabilized microwave generators

The investigation results of formation peculiarities of the autodyne signal of stabilized UHF oscillators at the de-tuning of the oscillation frequency related to the natural frequency of the stabilizing resonator are given. The main mathematical equations are obtained, which describe the autodyne response to the impact of proper radiation reflected from the target. The calculation of the amplitude, frequency and amplitude-frequency characteristics of the autodyne system under various conditions are discussed. The experimental results obtained on an example of hybrid-integrated oscillator on Gunn diode of 8 mm-range are described. Experimental results quantitatively confirm the theoretical conclusions

Fluctuation characteristics of autodyne radars with frequency modulation

A mathematical model of the autodyne radar with frequency modulation has been developed. The model is presented in the form of a self-excited oscillator with single-loop oscillating system adjusted in terms of frequency by varying the varicap capacitance. This model takes into account the impact of intrinsic radiation reflected from the object of location and inherent noises of the generator, as well as the power source noises. Basic expressions were derived for the calculation of the signal accompanying the spurious response of generator, components of the legitimate signal and the noise during the registration of autodyne response both in the power supply circuit and in terms of the variation of oscillation amplitude. Calculations of noise characteristics were carried out at small and large values of the feedback parameter. The phenomenon of periodic nonstationarity of noise levels at the autodyne generator output was detected in conditions of strong feedback. The results of calculations and experiments were obtained for the autodyne built on an 8 mm-band Gunn diode