MATCHED DIGITAL FILTER OF DIGITAL FREQUENCY-SHIFT KEYED SIGNALS Russian patent published in 1994 - IPC

FIELD: radio engineering. SUBSTANCE: matched digital filter of digital frequency-shift keyed signals has frequency recirculator, first, second, third switches, first, second storage units, first, second key units, threshold unit, decoder unit, N accumulators, maximum number selecting unit, first, second, third threshold shaping units, synchronizing unit. First threshold shaping unit has first, second, third switches, N/2 minimum number selecting unit, first, second adders, first, second dividers, first, second multipliers, first, second, third registers, minimum-number selecting unit, variable-ratio divider, storage unit, adder. N/2 minimum-number selecting unit has N comparators, first, second counters, first, second, third keys, first, second pulse shapers, NOR gate, OR gate, decoder, flip-flop. Minimum-number selecting unit has N comparators, first, second, third keys, strobe shaper, adder, first, second delay elements, first, second counters, decoder, fourth and fifth keys. Third threshold shaping unit has key unit, N/2 minimum-number separating unit, adder, divider, multiplier, first, second registers. Series-connected threshold unit, decoder unit, and second key unit have OR gate, AND gate, first, second, and third comparators, first and second keys. Synchronizing unit has master oscillator, first, second, third frequency dividers, strobe shaper, first, second through seventh keys, delay element, reference-frequency shaper, pulse shaper. EFFECT: provision for shaping rejection thresholds within filter passband independent of input-noise, narrow-band noise and pulse noise level due to signal analysis in time-frequency plane, improved noise immunity of filter. 3 cl, 7 dwg