There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The laser diode self-mixing (or feedback) interferometric technique is reviewed as a general tool for remote sensing applications. The operating principle is outlined, and the attainable performance is compared to conventional coherent detection. Applications to metrology and to new sensing schemes are described, experimental results are reported and the overall performance of the sensors are assessed.

Laser diode self-mixing technique for sensing applications : Optical distance measurement

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.

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

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.

A double-diode autodyne transceiver

Research results of signal formation features of the autodyne sensor (AS) with sinusoidal frequency modulation (FM) are presented. Expressions for low frequency information signals are given and their numerical analysis is performed for cases when signal period is substantially longer than reflected radiation delay time as well as for the case when this inequality is not fulfilled. It is proved that at a small distance to the reflected object when feedback parameter value is commensurable with 1, the distortions of FM AS signals are typically caused by reflected radiation phase incursion irregularities. When distance grows the distortion level becomes significantly smaller due to delay phenomenon of reflected radiation. Experimental research results are obtained on the example of the autodyne oscillator based on the 8-mm wavelength range Gunn diode with varicap-based FM.

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Signals of Autodyne Sensors with Sinusoidal Frequency Modulation

A radar sensor as part of the automatic shunting system has been developed for the remote control of track occupancy in the hump yard and railroad switch territories, enhanced by the speed control of rolling stock when it passes by the retarder. The sensors are equipped with systems of remote control. They are provided with systems of internal parameter diagnostics and transmission of the radar and service information to the control point and can work in information networks.

Radar sensors for hump yard and rail crossing applications

Autodyne gunn-diode transceiver with internal signal detection for short-range linear fm radar sensor

The results of investigations of 8-mm band FMCW autodyne radar are given in this work. The radar intended for speed and range measurement of objects. Self-detection autodyne transmitter is made on base of Gann diode with varactor tuning. Digital methods of radiating signal forming and spectral signal processing and digital filtering of difference frequency signal are realized in the radar. Autodyne radar potential is not less 85 dB having output power of about 25 mW. Resolution on distance at the tuning band of 500 MHz is 0.6 m and range measurement accuracy 0.3 m. Dimensions of the radar are 92times92times166 mm. Mass is 0.35 Kg.

Autodyne millimeter-wave FMCW radar

The principals of the autodyne short range surveillance radar for object detection on distances from several to hundred meters are considered in this paper. The description of the flow chart, main parameters and results of testbed model examination are given.

http://ieeexplore.ieee.org/iel5/5287480/5292809/05292871.pdf

Millimeter band surveillance autodyne radar

Results of signal peculiarities' investigation of an autodyne short-range radar system with linear frequency modulation for the moving reflecting object are considered. The autodyne signal plots are obtained for the cases when its period duration is much longer than delay time of the reflected emission as well as for the cases when this inequality is not satisfied. Experimental data are obtained on the 8mm-range Gunn-diode oscillator with frequency tuning by the varicap.

A. S. Vasiliev

Papers

Radar sensors for hump yard and rail crossing applications

Autodyne gunn-diode transceiver with internal signal detection for short-range linear fm radar sensor

Autodyne millimeter-wave FMCW radar

Millimeter band surveillance autodyne radar

Signals from a moving object of autodyne radars with linear frequency modulation