Methods and apparatus for demodulating digital signals

A method for demodulating a signal, the method comprising:

• digitizing the signal at a fixed sampling time to generate a digitized signal;
• demodulating the digitized signal into a demodulated in-phase signal and a demodulated quadrature signal, the demodulating comprising:
• multiplying in-phase coefficients with digital windowing function coefficients to generate windowed digital in-phase coefficients, the in-phase coefficients generated to produce a demodulated in-phase signal at a demodulation signal frequency, the digital windowing function coefficients comprising digital filter coefficients;
• multiplying quadrature coefficients with the digital windowing function coefficients to generate windowed digital quadrature coefficients, the quadrature coefficients generated to produce a demodulated quadrature signal at the demodulation signal frequency;
• multiplying the digitized signal with windowed digital in-phase coefficients to generate demodulated in-phase signals;
• multiplying the digitized signal with windowed digital quadrature coefficients to generate demodulated quadrature signals;
• and
• accumulating the demodulated in-phase signals and the demodulated quadrature signals to produce in-phase magnitude values and quadrature magnitude values.

A device, comprising:

• a first multiplier configured to multiply in-phase coefficients with digital windowing function coefficients to generate windowed digital in-phase coefficients, the in-phase coefficients generated to produce a demodulated in-phase signal at a demodulation signal frequency, the digital windowing function coefficients comprising digital filter coefficients;
• a second multiplier configured to multiply quadrature coefficients with the digital windowing function coefficients to generate windowed digital quadrature coefficients, the quadrature coefficients generated to produce a demodulated quadrature signal at the demodulation signal frequency;
• an analog to digital converter (ADC) configured to convert an input signal into a digital signal by sampling the input signal at a fixed sampling time;
• a third multiplier operatively coupled to the ADC and the first multiplier, the third multiplier configured to multiply the digital signal with the windowed digital in-phase coefficients;
• and
• a fourth multiplier operatively coupled to the ADC and the second multiplier, the fourth multiplier configured to multiply the digital signal with an output of the second multiplier;
• a first adder operatively coupled to the third multiplier, the first adder configured to accumulate the demodulated in-phase signal to output in-phase magnitude values;
• and
• a second adder operatively coupled to the fourth multiplier, the second adder configured to accumulate the demodulated quadrature signal to output quadrature magnitude values.