Enclosed images show the Grill Pan, which is a multiple-target X-band tracking and guidance radar using a 10,000-element space fed
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transmission lens. Above the radar array is an IFF planara array, and below it are ** three sidelobe canceller antennas**, which are mechanically steered to cover the main array sidelobe structure on up to three selected targets.
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There are two monopulse feeds on the top of the rotating radar turret. The upper feed is covered by a white, Teflon-like shell and is used when the array is set to 30° tilt for aircraft targets. The lower feed is further forward on the roof of the turret and is in line with the center axis of the array when it is tilted to approximately 45° for TBM intercepts.
The emphasized features of the SA-12 system, including the Grill Pan array, are low RF loss and low cost.
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The phase shifters are Faraday rotators, having two sections in series, controlled by separate coils, with a total phase of 720°.
In each phase shifter, the first coil is connected in series with coils of other phase shifters in that row and driven by the row command. The second coil is connected in series with coils of the other phase shifters in that column and drlven by the corresponding column command. Thus, a 10,000-element array, 100x 100 elements, requires only 100 row drivers and 100 column drivers. There are no electronic components on the phase shifter.
The radar transmits right circular polarization and receives left circular (the predominant target echo polarization), and hence the Faraday rotator uses the same control field for reception as for transmission.
The control field is changed only when the beam position is changed. During a dwell of several
milliseconds, several hundred pulses are transmitted and received.
The phase shifter loss is less than 1 dB in each direction.
Since the transmission and reception are performed with orthogonal polarizations, isolation is obtained with an orthomode feed horn, eliminating the duplexer loss.
The low noise receiver (noise factor 3 dB) uses an electrostatic amplifier tube that can withstand leakage powers of several hundred Watts
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without damage and with near-instantaneous recovery to full gain and sensitivity when the transmitted pulse ends.
Thus, the loss attributed to solid-state protective devices commonly required in Western radars is also absent.
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The total round trip RF loss from transmitter tube to low noise receiver (excluding propagation loss in the atmosphere) is held to 3 dB, in contrast to the 7 to 12 dB found in comparable Western systems.
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The reduced cost and loss, and the ability to transmit and process (with high clutter attenuation) high-PRF waveforms over long dwells, are made possible by the assignment to the radar of a limited number of tracks and very limited search capability in,
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contrast to the Western preference for multifunction array radars.
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The cost of separate search radars must be accepted in such a system.
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Razdelenie funkzij ,esli net zestkix ogranichenij po gabaritam fundamentalno lutschee reschenie
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lt is perhaps the reduced emphasis placed by the Russian military on life-cycle costs of vehicles and personnel that permits them to use this approach.
A
nother possible explanation is the Russian military's insistence on high performance against targets of low cross section in environments containing rain, chaff and other sources of clutter, ###an almost insoluble problem when the multifunction approach is adopted.###
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