US 6,310,513 B1 · Demodulator and demodulation method for demodulating quadrature modulation signals

Abstract

A demodulator for demodulating a modulation signal (IF IN) which has been modulated by means of quadrature modulation includes a quasi-coherent detection section, a demodulation section, a signal error detector, a phase error detector, a quadrature error detector and a quadrature controller. The signal error detector detects signal errors (Ei, Eq) and polarities (Di, Dq) of signals (I-ch5, Q-ch5) demodulated by the demodulator. The phase error detector detects the phase error (Pd) of the demodulated signals (I-ch5, Q-ch5) based on the signal errors (Ei, Eq) and the polarities (Di, Dq). In the quadrature error detector, a quadrature error (Qd′) after phase rotation executed in the demodulation section is obtained by calculating Ei·Dq+Eq·Di, and thereafter a quadrature error (Qd) before the phase rotation is obtained by means of polarity switching based on the demodulated signals (I-ch5, Q-ch5) and a phase rotation angle signal (Ang) which is generated from the phase error (Pd). The quadrature controller executes complex multiplication to quadrature components (I-ch1, Q-ch1) obtained by the quasi-coherent detection section based on the quadrature error (Qd), and thereby the quadrature error in the demodulated signals (I-ch5, Q-ch5) is eliminated automatically.

Claims26

Dependent claims

A demodulator for demodulating a modulation signal which has been modulated by means of quadrature modulation, comprising:

a quasi-coherent detection means for executing quasi-coherent detection to the modulation signal and thereby outputting quadrature components;
a demodulation means for correcting amplitude errors of the quadrature components outputted by the quasi-coherent detection means, correcting frequency offset components and phase offset components of the quadrature components, and thereby outputting demodulated signals;
a signal error detection means for detecting signal errors and polarities of the demodulated signals;
a phase error detection means for generating a phase error based on the signal errors and the polarities, for use by the demodulation means;
a quadrature error detection means for generating a quadrature error using at least the signal errors;
and
a quadrature error elimination means, coupled between the quasi-coherent detection means and the demodulation means, for executing complex multiplication to the quadrature components outputted by the quasi-coherent detection means based on the quadrature error generated by the quadrature error detection means and thereby eliminating the quadrature error in the demodulated signals.

4 more elements

A demodulation method for demodulating a modulation signal which has been modulated by means of quadrature modulation, comprising the steps of:

a quasi-coherent detection step in which quasi-coherent detection is executed to the modulation signal and thereby quadrature components are obtained;
a demodulation step in which amplitude errors of the quadrature components obtained in the quasi-coherent detection step are corrected, frequency offset components and phase offset components of the quadrature components are corrected, and thereby demodulated signals are obtained;
a signal error detection step in which signal errors and polarities of the demodulated signals are detected;
a phase error detection step in which a phase error of the demodulated signals is generated based on the signal errors and the polarities for use in the demodulation step;
a quadrature error detection step in which a quadrature error is generated using at least the signal errors;
and
a quadrature error elimination step in which complex multiplication is executed to the quadrature components obtained in the quasi-coherent detection step based on the quadrature error generated in the quadrature error detection step and thereby the quadrature error in the demodulated signals is eliminated.

4 more elements

Dependencies are inferred from the claim text.

Demodulator and demodulation method for demodulating quadrature modulation signals

Life of this patent

Demodulator and demodulation method for demodulating quadrature modulation signals

Life of this patent

Abstract

Claims26