	US 7,548,591 B2
	Quadrature modulator and calibration method
Ali Parsa, Los Angeles, Calif. (US); Ali Fotowat-Ahmady, Richmond Hill (Canada); Ali Faghfuri, Stanford, Calif. (US); Mahta Jenabi, Richmond Hill (Canada); Emmanuel Riou, Santa Clara, Calif. (US); and Wilhelm Steffen Hahn, Los Altos, Calif. (US)
Assigned to NXP B.V., Eindhoven (Netherlands)
Appl. No. 10/554,020 PCT Filed Apr. 20, 2004, PCT No. PCT/IB2004/001191 § 371(c)(1), (2), (4) Date Oct. 21, 2005, PCT Pub. No. WO2004/095686, PCT Pub. Date Nov. 04, 2004.
Claims priority of provisional application 60/465127, filed on Apr. 24, 2003.
Prior Publication US 2006/0208820 A1, Sep. 21, 2006
Int. Cl. H04L 27/36 (2006.01); H04B 1/04 (2006.01)

U.S. Cl. 375—298 [455/126]

15 Claims

1. A quadrature modulator, comprising:

a) an in-phase modulation branch receiving as an input an analog in-phase base band signal, the in-phase modulation branch including a first dc offset adjustment circuit, a first base band gain adjustment circuit, and a first mixer;

b) a quadrature modulation branch receiving as an input an analog quadrature based band signal, the quadrature modulation branch including a second dc offset adjustment circuit, a second base band gain adjustment circuit, and a second mixer;

c) a local oscillator means for providing a local oscillator signal to the first mixer and a phase shifted version of the local oscillator signal to the second mixer;

d) a summer for summing the outputs of the first and second mixers;

e) an envelope detector for detecting an output signal of the modulator and providing a signal representative of the amplitude of the output signal of the quadrature modulator;

f) a band pass filter for filtering the amplitude signal; and

g) a signal strength indicator circuit for measuring the strength of the filtered amplitude signal, the indicator circuit providing a compensation signal for adjusting the phase shift of the local oscillator and the dc offsets and base band gains of the in-phase and quadrature base band signals.