N.А. Kushnerev1, E.S. Nazarova2, М.V. Rodin3

1 JSC «Concern «VEGA» (Moscow, Russia)

2,3 Bauman Moscow State Technical University (Moscow, Russia)

Radars are widely used as information sensors in solving problems related to all-weather remote monitoring of objects and events in the surrounding space. Modern radars mainly work with signals, which are rectangular envelope radio pulses that makes it possible to implement highly efficient operation modes of semiconductor transmitter. Signals with inpulse linear (LFM) and nonlinear frequency modulation (NLFM) are often used.

However, as noted in the article, the radar signal envelope shaping in the semiconductor transmitter is inevitably accompanied by amplitude distortions, caused, firstly, by a decrease in the power supply voltage of the amplifier towards the end of the signal, secondly, by the unevenness of the amplitude-frequency response of the amplifier, and thirdly, by heating the crystal of the transistor and, as a result, a decrease in the gain during operation. As a rule, the envelope distortion of the radar LFM and NLFM signals reduces the radar informativity.

The article presents basic information about the radar signal envelope shaping in modern pulse radars and indicates the causes of its distortion. The results of the analysis of the distortion’s influence of LFM and NLFM radar signals envelope on the response shape of the matched-filter are described. Recommendations are formulated for the choice of the permissible voltage droop. It is shown that the permissible voltage drop should be chosen taking into account the compromise between the distortion matched-filter response on the receiving side of the radar and a decrease in the energy of the radar signal.

A brief review of the methods known from the scientific and technical literature aimed at reducing the envelope signal distortions is given. Currently, to effectively compensate for the distortion of the radar signals envelope, mainly methods are used aimed at predetecting the amplified signal and operational control of the power amplifier’s supply voltage. The current state of digital electronics makes it possible to create devices to compensate for changes in the power amplifier’s characteristics both during the duration of the amplified signal and during prolonged operation, taking into account all destabilizing factors, and thus form the radar signal envelope with high accuracy.

The article is of an overview nature and is intended, first of all, for engineers developing semiconductor radar transmitters.

Kushnerev N.А., Nazarova E.S., Rodin М.V. Distortions of the radar signals envelope. Achievements of modern radioelectronics. 2022. V. 76. № 6. P. 33–48. DOI: https://doi.org/10.18127/j20700784-202206-04 [in Russian]

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