Sub-Systems and Hi-Rel

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QPSK Signal Demodulator

In receivers designed to detect data streams of varying rates, to obtain the lowest bit error rate (BER) under varying carrier-to-noise ratios, it is necessary to select the Nyquist filter for the predominant data rate. In a special sub-system developed by Merrimac, Nyquist filters are switched in the demodulated bit stream to optimize the BER.

In the example illustrated here, Nyquist filters are selected by an external TTL control input. The circuit also includes a high gain comparator on each channel with ECL-compatible outputs. The complete unit is housed in a low profile, hermetic flatpack for maximum reliability and integration with other sub-systems in a highly compact receiver.

Radar Warning System Beamformer

This beamformer shown is part of an airborne radar warning system for a fighter aircraft. Its purpose is to identify the precise position of the source of hostile radar signals such as radar guided air-to-air or surface-to-air missiles. Located in the aircraft’s nose cone, beamformer performance is critical to electronic countermeasures success.

The unit shown covers 500 MHz to 2 GHz and is one of many sub-systems developed by Merrimac

Helicopter Elint Antenna Combiner

Operating from 2 to 18 GHz, this stripline sub-system combiner/equalizer routs signals from various antennas to an ECM receiver. The sub-system developed by Merrimac includes 14 passive components integrated into a single high performance assembly meeting all performance specifications and reliability criteria. The severe mechanical stress environment (shock and vibration) imposed by a helicopter installation meant Merrimac designers needed to minimize the number of connectors to achieve reliability objectives. To reduce size, two identical halves of the required circuit were sandwiched in a single, rugged assembly measuring 5.0" x 3.9" x 0.6" (120 x 94 x 15mm), and weighing just 16 oz (440 grams).

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