Texas Instruments Corporation

Other

Angel Ezquerra-Moreu

Pascal Audinot

Lorenzo Carpineto

Estelle Nguyen

A gain control system in a Direct Conversion Receiver or similar receiver, includes an automatic gain control circuit which determines whether a low noise amplifier, which amplifies signals from an antenna prior to mixing with signals from a local oscillator, should be set to a high gain or a low gain. The output of the mixer is analyzed by a blocker detect circuit to determine whether a blocker signal is present. Based on the presence of a blocker signal and the power level of the useful signal, the gain of the low noise amplifier may be reduced from the high gain to an intermediate gain in order to reduce self mixing between the radio frequency and local oscillator ports of the mixer, which may lead to dynamic DC offsets.

Reduction of dynamic DC offsets in a wireless receiver

A method for estimating and removing a time varying DC-offset includes the steps of dividing the received burst into blocks (), then finding the maximum and minimum values in each block (). Once the maximums and minimum values have been found, the upper and lower envelopes are determined (). The DC-offset path is then calculated by taking the average of the upper and lower envelope (). Once determined, the DC-offset path information is used in order to subtract the DC-offset from the desired signal.

Method for estimating and removing a time-varying DC-offset

A method for refining a DC-Offset estimate and removing of the DC-Offset includes the step of determining if any AM is present (). If AM is determined to be present, it is next determined if the I and Q path DC-Offset estimates are closely matched, if they are, then only a single search using the average of the I and Q path estimates is used (). If it determined however, that the two path estimates are not closely matched, than two searches are performed, one for each path (). After this, the blocking signals are searched for up to a predetermined number and the DC-Offset vector is generated (). Once the DC-Offset vector is generated, the DC-Offset is removed from the received signal (). After which it is determined if the AM level is high (), and if so, a transient correction routine is performed ().

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San Diego, CA, United States of America

Angel Ezquerra-Moreu