Patent ID: 6785346
Filing Date: 2004-08-31
Classification: H03D,H04L

Abstract:
A complex demodulator for demodulating an RF signal converted to digital I and Q IF signals, the complex demodulator comprising:a numerically controlled oscillator (NCO) for generating first and second output signals in quadrature centred at the IF frequency; a first digital multiplier having a first input for receiving the digital I IF signal, a second input for receiving the first NCO output signal and an output; a second digital multiplier having a first input for receiving the digital Q IF signal, a second input for receiving the second NCO output signal and an output; a difference combiner coupled to the outputs of the first and second digital multipliers for providing a phase signal at its output, the phase signal being coupled to the NCO through a feedback loop to control the NCO frequency, a third digital multiplier having a first input for receiving the digital I IF signal, a second input for receiving the second NCO output signal and an output; a fourth digital multiplier having a first input for receiving the digital Q IF signal, a second input for receiving the first NCO output signal and an output; and a sum combiner coupled to the outputs of the third and fourth digital multipliers for providing an amplitude signal at its output.