Russian Airborne Early Warning Systems.

overscan (PaulMM)

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27 December 2005
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Some interesting quotes from the Fedosov book.

Regarding Tu-126's Liana radar

For the selection of the moving purposes (SDTS) was adapted the device of two-fold cross-period subtraction on the charge-storage tubes (method SDTS with the external coherence). “Blind” speeds were excluded by wobble of the repetition frequency of sounding pulses. The use of a comparatively long transmitting wave and the selection of the moving purposes made it possible to reveal small size aircraft (of type MiG-17) of against the background stormy sea at the distances not less than 100 km, strategic bombers - not are less than 300 km, surface ships to the radio horizon (for 9… 10 km of the flight altitude of aircraft Tu-126 this was 400 km).
In 1964-1966 and 1967-1971 yr. were carried out two basic scientific research works in the region of the air patrol. The number of the primary tasks of the first work included the production of tactical technical requirements for RLS, the analysis of reflection spectra from the earth and the selection of the methods of the selection of pinpoint targets against their background, obtaining experimental material with the reflecting properties of different terrestrial covers and the formulation of requirements for the basic components RLS. The specific recommendations by construction OF RLS of two forms were the sum of this scientific research work:

• RLS, working in the decimeter wave band with the sufficiently low pulse repetition frequency, which ensures uniqueness on distance in the limits of radio horizon, for the fixed points and the low-mobility carriers, which make it possible to use antennas of large sizes;

• RLS, which work in the centimeter s-band the average and high frequency of repetition, with the ambiguity on the distance - for the high-speed carriers, which rigidly limit the maximum overall sizes of antenna.

Two basic types of aviation early warning systems are outlined: on the captive balloons and on the aircraft.
The second work was directed toward a study and the experimental confirmation of the possibilities of the aviation radar complexes of long-range detection, work on any surfaces, and also the creation of a number of their components. In the process of fulfilling this work they were created and checked under the actual conditions experimental high(ly)-coherent RLS of decimeter and centimeter wave bands, was carried out the large volume of works on study and creation of the fundamental sets RLS of patrol - antennas with the small side lobes of the radiation pattern, coherent receiving-transmitting devices with the lowest possible level of amplitude-phase noise, devices of method and processing of radar signal, that possess low factor of the noise and high linearity with the large dynamic range of input signals.
The mock-up RLS of decimeter range in 1968 g. was established on Tarki- tau mountain in g. makhachkala. With the work of this RLS it was possible to completely suppress reflections from the broken ground to the north from g. makhachkala and to reveal the small size aircraft (An-2 and MiG-17) at distances 100… 130 km with the aid of experimental RLS was demonstrated the reality of the creation of the aerostatic or highland radar posts of the detection of low-altitude targets. In 1970 g. the development was assigned, while in 1977 g. was accepted for the armament complex “PERISCOPE- V” - THE USSR'S first highland RL- post, capable of detecting the small size low-altitude targets against the background of earth reflections (chief designer [Metelskij] a. T.). Work is honored the State Prize TO THE USSR for 1981 g.
Was also created and established on the helicopter Mi-10 the experimental model of quasi-continuous RLS, which works in the centimeter wave band. The large-dimension revolving antenna was placed in the fairing under the fuselage of helicopter. The amplitude-phase noise of the receiving-transmitting device made it possible to reveal the echo signals of purpose in the interferences from the earth, which exceed them on 80… 85 dB. The possibility of detection by quasi-continuous RLS of the aircraft of the against the background earth's surface at the significant distances was demonstrated with the aid of the experimental model.
The results of these two scientific research works made it possible to approach the development of the aviation complex of radar surveillance and guidance.
In the cycle of works on a study and the scientific development of the direction of radar, which solves the detection problem of the purposes above the earth, in 1989 g. to specialists [MNIIP] is awarded the State Prize TO THE USSR.
A-50 Schmel radar

Principles of operation and characteristics "Schmel”

Onboard RLS (chief designer [Pogreshaev] v. f.) works in the quasi-continuous regime with the detection of aerial targets and the the pulse during the detection of surface targets. In the quasi-continuous regime the time between two following after each other pulses corresponds only to several kilometers on the distance. Therefore, in order to remove ambiguity on the distance, are used several pulse repetition frequencies. The temporary relationships of work RLS are selected in such a way that sounding each purpose is produced at three close repetition frequencies. The sequences of sounding pulses are compared between themselves in “the coincidence circuit”, as a result of which it is obtained general frequency. Analogously with the comparison of the pulses accepted is obtained the same frequency, but only with the time delay, which depends from the range to target (Fig. 5.1.6).

Interference suppression, caused by the reflection of sounding pulses from the underlying surface, is produced by the method of frequency selection, which considers the difference of Doppler frequency shifts from the underlying surface and from the aerial target. The transmitting device multichannel, is executed on the powerful output klystrons. The assigning SHF generator oscillator is executed on the crystal generator with the subsequent frequency multiplication in the varactor chain. The amplitude-phase noise of the receiving-transmitting device makes it possible to see the signal of the purpose against the background of interference from the earth.

Processing radar signal combined: during the first stage - with the aid of discrete- analog device with the quartz filters, on the second - with the aid of the digital rejectors and the Doppler filters (rapid Fourier transform). The digital part of device is executed in the form special computer. IN TSCVM $$RTQVM - DIGITAL COMPUTER RLS are produced the grouping on the elements of the distance of the marks, which relate to one purpose, the measurement of azimuth and angle of elevation, the calculation of single-valued range to target according to the marks at two or three repetition frequencies, shaping of information for the mapping to the flight engineer OF RLS and delivery into onboard computing system, and also automated inspection of the technical state of equipment RLS.

RLS can work in the mixed regime, in which several surveys of work in the quasi-continuous regime alternate with the survey in the usual pulsed operation with the high repetition frequency. This makes it possible to conduct simultaneous work on the detection both of air and surface targets.

The antenna OF THE SURVEILLANCE RADAR with the overall dimensions of 10x1,7 m is built on the horizontal slotted waveguides. The connection of antenna with the equipment, located inside the fuselage, is achieved through the multichannel SHF rotating transition and the low-frequency contact revolving device. The antenna coupling of national recognition and radio links of control is organized according to the same principle.

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