Instead of an excitation pulse sequence producing circuit which is used according to prior art in calculating pulse instants or locations of excitation pulses and pulse amplitudes thereof, an excitation pulse sequence parameter producing circuit is used in a low bit-rate pattern coding device in recursively giving delays of the respective pulse instants to a discrete impulse response sequence to provide a system of delayed impulse responses and in orthogonalizing the delayed impulse response system into an orthogonal system of system elements, Meanwhile, the pulse instants are determined with element amplitudes or factors calculated for the respective system elements by the use of the system elements and each segment of a discrete pattern signal sequence. The pulse instants and the element amplitudes are used as parameters descriptive of the excitation pulses. Alternatively, the pulse instants are determined one at a time after quantization of each of the recursively determined element amplitudes. Preferably, the discrete impulse response sequence and the segment are weighted in consideration of auditory or like sensual effects. In a counterpart decoder, the pulse amplitudes are calculated by the use of the pulse instants and the system elements which are calculated by using the pulse instants and another parameter sequence which, in turn, is derived in the coding device from the segment in the manner in the art of multi-pulse excitation.
LOW BIT-RATE PATTERN CODING WITH RECURSIVE ORTHOGONAL DECISION OF PARAMETERS