V. Ya. Noskov

A double-diode autodyne transceiver

The principle of operation and design of an 8-mm autodyne transceiver module, based on two mutually synchronized Gunn diode oscillators, and schemes of the signal detection unit in the Gunn-diode supply circuit are described. The oscillation frequency of the autodyne is stabilized by an additional high-Q resonator, connected to the working resonator using a reflection circuit with resistive coupling. The measured data on the double-diode autodyne oscillator are presented and recommendations on its tuning are given. It is shown that the presence of quadrature signals and high stability of the oscillation frequency of the double-diode autodynes ensure some new possibilities, when they are used to solve problems of near-field radio location, checking product sizes, and measuring vibration and displacement parameters.

Main features of double-diode autodynes and its application

The results of the autodyne features for double-diode oscillator on Gunn diodes affected by the own reflected signal are presented. The main characteristics of such autodyne are considered oriented to the application in short-range radar systems. The brief description of the autodyne sensor for the determination of the loco movement parameters which is made on the basis of the double-diode autodyne.

Noise characteristics of autodynes with frequency stabilization by means of an external high-Q cavity

The expressions describing the autodyne (AD) response are obtained with allowance for the internal noise of a frequency-stabilized microwave oscillator subjected to the action of its self-radiation reflected from an object. The results of analyzing the AD and noise characteristics of the stabilized oscillator built around the band-reflecting filter with resistive coupling are presented. The conditions leading to the appearance of the periodic non-stationarity of noise characteristics are established. It is demonstrated that frequency stabilization is ensured by a gain in dynamic range. The experimental data on unstabilized and stabilized hybrid-integral AD oscillators based on the two-mesa Gunn diode of 8-mm range are presented.

About applicability of quasi-statistic method of autodyne systems analysis

There is shown applicability of quasi-static method for analysis of differential equations of single-circuit autodyne generator. We propose the methodology of quasi-static calculation of autodyne response taking into account of members of higher approximation order. The estimation of calculation inaccuracy in case of quasi-static method application is given, conditions of stability of the system of autodyne generator-reflecting object are considered, and comparative calculation of autodyne response for a cases of application of zeroth and tenth approximations.

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

Results of investigations of autodyne characteristics of microwave generators stabilized by an external high-Q resonator as a function of the oscillations frequency detuning and the natural frequency of the stabilizing resonator have been presented. Main mathematical expressions describing the autodyne response of generator to the impact of intrinsic radiation reflected from target were obtained. The design of the coupling between the main working and stabilizing resonators was implemented by using a circuit of band-reflecting filter with resistive coupling. The calculations of amplitude, frequency, and amplitude-frequency characteristics of the autodyne system were carried out under various conditions. The experimental data qualitatively corroborating the inferences of theoretical studies were obtained by investigating the case of a hybrid-integral 8-mm band Gunn oscillator.

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.

Particularities of double-diode autodyne characteristics

Calculations of main characteristics of a two-diode autodyne subject to the influence of eigen reflected radiation are performed. It is used, at that, a mathematical model in the form of two mutually synchronized partial oscillators with a delayed mutual coupling between them. Particularities of behavior of amplitude and phase characteristic variations of partial oscillators, frequency and phase difference, along with the response of active elements in the power supply circuit are considered.

Mathematical model of double-diode autodyne

A mathematical model has been developed for a double-diode autodyne oscillator affected by the proper reradiation. The model represents two mutually-synchronized partial oscillators with time delayed coupling between them. It is possible for studying peculiarities of autodyne amplitude variations of the partial oscillators, autodyne variations of frequency and phase difference and, also, in the power supply circuit responses of the active elements.

Methods of autodyne signal registration

In order to increase autodyne radar sensibility and its reach, accordingly, it is proposed to record autodyne frequency changes. At the moving of reflecting object, oscillations occur with Doppler frequency. Autodyne system becomes cheaper and less complicated if autodyne signal is recorded in the feed circuit. For this purpose resistors, chokes and transformers are used. From the analysis conducted it follows, that autodyne radar, which records the change of oscillation frequency is close to potential limit of autodyne systems.

About an energy potential of autodynes

The expressions for calculating the noise characteristics and energy potential of an autodyne system taking into account both internal fluctuations of an oscillator active element and real power supply noises of a microwave oscillator were found. Calculations made on the example of a Gunn diode oscillator showed that the autodyne potential on case of detecting signal in the power circuit of oscillator is significantly lower than in case of detecting signals by changing the frequency and amplitude of oscillations.