FSK demodulator system and method

An FSK demodulator system with tunable spectral shaping comprising:

• a limiter responsive to a first and second quadrature signals at a predetermined IF frequency varied by a positive and negative frequency deviations for generating digital first and second quadrature signals;
• a pair of quadri-correlators responsive to said digital first and second quadrature signals, one of said pair deriving first and second signals representative of the frequency deviation of said quadrature signals at even integer multiples of said frequency deviation and for resolving the modulated FSK data represented by said quadrature signals and the other of said pair deriving first and second signals representative of the frequency deviation of said quadrature signals at odd integer multiples of said deviation frequency and for resolving the modulated FSK data represented by said quadrature signals;
• and
• a delay control circuit for setting a delay to each of said pair of quadri-correlators to control said first and second signals representative of the frequency deviation of said quadrature signals derived by each of said pair of quadri-correlators and generate a tuned spectral response at both even and odd integer multiples of said frequency deviation.

An FSK demodulator system with tunable spectral shaping comprising:

• an analog-to-digital converter responsive to first and second quadrature signals at a predetermined IF frequency varied by positive and negative frequency deviations for generating digital first and second quadrature signals;
• a sine and cosine pair of quadri-correlators responsive to said digital first and second quadrature signals each of said pair deriving first and second signals representative of the frequency deviation of said quadrature signals at even or odd integer multiples or sub-multiples of said frequency deviation about said IF frequency and for resolving the modulated FSK data represented by said quadrature signals;
• a delay control circuit for setting a delay to each of said sine and cosine pair of quadri-correlators for controlling said first and second signals representative of the frequency deviation of said quadrature signals;
• and
• a plurality of scaling circuits responsive to said sine and cosine pair of quadri-correlators for introducing programmable scaling coefficients to the output of each of said pair correlators to weight said first and second signals representative of the frequency deviation generated by each of said pair of correlators to generate a composite tuned spectral response that combines said even and odd integer multiples of said frequency deviation.

An FSK demodulator system with tunable spectral shaping comprising:

• a analog-to-digital converter responsive to a first and second quadrature signals at a predetermined IF frequency varied by a positive and negative frequency deviations for generating digital first and second quadrature signals;
• a sine and cosine pair of quadri-correlators responsive to said digital first and second quadrature signals each of said pair deriving first and second signals representative of the frequency deviation of said quadrature signals at even or odd integer multiples or sub-multiples of said frequency deviation about said IF frequency and for resolving the modulated FSK data represented by said quadrature signals;
• a delay control circuit for setting a delay to each of said sine and cosine pair of quadri-correlators for controlling said first and second signals representative of the frequency deviation of said quadrature signals;
• a plurality of scaling circuits responsive to said sine and cosine pair of quadri-correlators for introducing programmable scaling coefficients to the output of each of said pair correlators to weight said first and second signals representative of the frequency deviation generated by each of said pair of correlators;
• and
• an adder circuit responsive to said plurality of scaling circuits for lineally combining the outputs of said sine and cosine pair of quadri-correlators to generate a composite spectral response that combines said even and odd integer multiples of said frequency deviation.

An FSK demodulator system with tunable spectral shaping comprising:

• a plurality of correlators, each said correlator including a sine and cosine correlator responsive to first and second quadrature signals at a predetermined IF frequency varied by positive and negative frequency deviations, each of said sine and cosine correlators deriving first and second signals representative of the frequency deviation of said quadrature signals at even or odd integer multiples or sub-multiples of said frequency deviation about said IF frequency and for resolving the modulated FSK data represented by said quadrature signals;
• a delay control circuit for setting a programmable delay to each of said sine and cosine correlators for controlling and maximizing said first and second signals representative of the frequency deviation of said quadrature signals;
• and
• a plurality of scaling circuits responsive to each of said sine and cosine correlators for introducing programmable scaling coefficients to the output of each of said sine and cosine correlators to weight said first and second signals representative of the frequency deviation generated by each of said sine and cosine correlators and generate a lineally combined composite spectral response that combines the outputs of each of said plurality of correlators and approximates a matched filter response.

An FSK demodulator system with tunable spectral shaping comprising:

• a analog-to-digital converter responsive to a first and second quadrature signals at a predetermined IF frequency varied by a positive and negative frequency deviations for generating digital first and second quadrature signals;
• a plurality of correlators, each said correlator including a sine and cosine correlator responsive to said digital first and second quadrature signals at a predetermined IF frequency, each of said sine and cosine correlators deriving first and second signals representative of the frequency deviation of said quadrature signals at even or odd integer multiples or sub-multiples of said frequency deviation about said IF frequency and for resolving the modulated FSK data represented by said quadrature signals;
• a delay control circuit for setting a programmable delay to each of said sine and cosine correlators for controlling and maximizing said first and second signals representative of the frequency deviation of said quadrature signals;
• and
• a plurality of scaling circuits responsive to each of said sine and cosine correlators for introducing programmable scaling coefficients to the output of each of said sine and cosine correlators to weight said first and second signals representative of the frequency deviation generated by each of said sine and cosine correlators and generate a lineally combined composite spectral response that combines the outputs of each of said plurality of correlators and approximates a matched filter response.

An FSK demodulator method comprising the steps of:

• deriving first and second signals representative of the frequency deviation of first and second quadrature signals at even integer multiples of the frequency deviation and resolving the modulated FSK data represented by the quadrature signals;
• deriving first and second signals representative of the frequency deviation of first and second quadrature signs at odd integer multiples of the frequency deviation and resolving the modulated FSK data represented by the quadrature signals;
• and
• setting a delay to control the first and second signals representative of the frequency deviation at the even and odd multiples of the frequency deviation to generate a tuned spectral response at both even and odd integer multiples of the frequency deviation.