Digital demodulator

A digital demodulator comprising local oscillation means, mixing means, A/D conversion means, hilbert transform means, delay means, multiplication means, filter means, frequency error detect means, a loop filter and numerically controlled oscillation means:

• wherein the hilbert transform means comprises:
• a first shift register for sequentially shifting a received signal to multiple shift registers;
• a second shift register for sequentially shifting a last delay output of the first shift register to multiple shift registers;
• a first adding unit having a number of adders for selectively adding signals output by the first and second shift registers;
• a multiplication unit having a number of multipliers for respectively multiplying the signals output from the adders in the first adding unit by predetermined tap coefficients;
• and
• a second adding unit having a number of adders for performing selective adding of each signal output from the number of multipliers in the multiplication unit, and
• wherein the frequency error detect means comprises:
• a first delay circuit for delaying the signal I from the filter means;
• a second delay circuit for delaying the signal Q from the filter means;
• a first exclusive OR circuit for performing an exclusive OR operation with respect to the output of the delay circuit and the signal Q;
• a second exclusive OR circuit for performing the exclusive OR operation with respect to the output of the delay circuit and the signal I;
• and
• an adder for summing up the outputs of the two exclusive OR circuits.