Patent Number: 6,310,513

Title: 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.multidot.Dq+Eq.multidot.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.

Inventors: Iemura; Takaya (Tokyo, JP)

Assignee: NEC Corporation

International Classification: H03D 7/16 (20060101); H03D 7/00 (20060101); H04L 27/233 (20060101); H03D 3/00 (20060101); H04L 27/38 (20060101); H03D 001/00 ()

Expiration Date: 10/30/2018