Apparatus for correcting quadrature error in a modulator and/or

Details Apparatus for correcting quadrature error in a modulator and/or Apparatus for correcting quadrature error in a modulator and/or

1996-09-26

1998-01-06

Mis, David

Modulators

Phase shift keying modulator or quadrature amplitude modulator

329304, 375308, 375329, H03C 300, H03D 300, H04L 2718

Patent

active

057059586

ABSTRACT:
Apparatus for correcting quadrature error in a quadrature modulator and/or in a demodulator for a signal having a plurality of phase states, or of amplitude and phase states. The correction apparatus comprises a processor (51) which, when the apparatus is used to correct quadrature error in a demodulator, transforms the levels P and Q of the digital signals output by the demodulation stage into corrected levels P' and Q' that satisfy any one of the following eight relationships: ##STR1## These corrected levels are then applied to decision element (72), optionally after their maximum levels have equalized. The apparatus combines correction accuracy with cheapness, and it enables any quadrature error to be corrected.

REFERENCES:
patent: 5077757 (1991-12-01), Cahill
patent: 5105445 (1992-04-01), Karem et al.
patent: 5111155 (1992-05-01), Keate et al.
patent: 5371481 (1994-12-01), Tiittanen et al.
H. Suzuki et al, "Affine transformations for compensating linear distortion: an application to linear signaling in mobile radio", Electronics and Communications vol. 75, No. 11, Nov. 1992, pp. 47-58.
Faulkner et al, "Automatic adjustment of quadrature modulators", Electronics Letters, vol. 27, No. 3, Jan. 31, 1991, Stevenage GB, pp. 214-216.

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