Convolution filter arrangement for digital multifrequency receiver

For use in a digital signal receiver having

• input means for receiving digital signals representative of sequential samples of an analog tone signal waveform;
• the combination comprising
• means for supplying a first set of digital impulse response signal samples representative of the impulse response of a bandpass filter and a second set of digital impulse response signal samples representative of the impulse response of said filter and being delayed by a predetermined time period from said first set of impulse response samples;
• a first convolution circuit means coupled to said input means and to said supplying means for generating a first set of convolution output data signals in response to a receipt of received digital signal samples and said first set of digital impulse response signal samples;
• a second convolution circuit means coupled to said input means and said supplying means for generating a second set of convolution output data signals in response to said received digital signal samples and said second set of digital impulse response signal samples;
• means for accumulating output data signals of said first and second convolution circuit means;
• and
• means for processing the accumulated output data signals of said accumulating means to detect a presence of a signal of a frequency defined by said bandpass filter.

A digital convolution filter arrangement comprising

• means for supplying a plurality of digital impulse response signal samples representative of an impulse response of a bandpass filter, each of said signal samples being delayed from each other said signal sample by a multiple of twenty samples,
• a plurality of digital convolution circuit devices, each of said devices being responsive to a receipt of input digital signals representative of sequential samples of an analog tone waveform and one of said plurality of digital impulse response samples for generating a convolution output data signal Y(nT) where ##EQU8## where Y(nT) is a discrete output data signal
• X(nT) is a discrete input digital signal
• H(nT) is a discrete impulse response signal
• NT is a summation interval
• T is a sampling interval, and each said device comprises
• means responsive to a receipt of the received input digital signals and one of said plurality of digital impulse response signal samples for generating a combined convolution signal,
• an adder for adding said combined convolution signal and said convolution output data signal Y(nT) to produce an add output signal, and
• an accumulator for accumulating said add output signal to generate said convolution output data signal Y(nT).