Nokia Corporation

Juha Kajava

Tommi Auranen

The invention relates to a method for correcting an IQ-imbalance (In-phase and Quadrature) of an IQ-based direct conversion receiver (). In the method a group of radio frequency pilot signals are received in the direct conversion receiver (). They are conveyed to an in-phase branch and a quadrature-phase branch of the receiver () and mixed, in the analogue domain, to form a baseband in-phase (I) and quadrature-phase (Q) signal components. The signal componets are conveyed to a digital demodulator () which detects the IQ-phase imbalance of the direct conversion receiver () by analysing at least one of the baseband in-phase (I) and the quadrature-phase (Q) signal components. In the method, the detected IQ-imbalance is corrected, in the analogue domain of the direct conversion receiver (), to achieve a 90 degrees phase difference between a future baseband in-phase (I) signal component and a future baseband quadrature-phase (Q) signal component.

IQ-imbalance

A method is presented for biasing an attenuator circuit used in high frequency applications. The method can improve the stability of the AGC system, and in some cases also the control accuracy. An attenuator circuit is disclosed which comprises at least two attenuator members ( ) connected in series. In connection with the attenuator members ( ) in an attenuator circuit according to the invention there are connected a suitable number of biasing members ( ) with which the biasing currents of the attenuator members ( ) can be controlled to have different magnitudes, so that in an attenuation situation the attenuator members ( ) begin to conduct separately, controlled by the AGC circuit.

Growing community of inventors

Naantali, Finland

Juha Kajava