Motorola Corporation

Chow Loong Cheah

Siew Yin Lee

Vc Prakash Vk Chacko

A method and circuit are described for estimating I and Q amplitude imbalance occurring in a signal received by a direct conversion receiver (DCR). The DCR generates a mixing signal having a frequency substantially the same as the carrier signal of the signal received by an antenna. A mixing module mixes the mixing signal at different phases with the received signal to generate I and Q baseband signals. A frequency offset circuit generates an offset signal having a frequency offset from the carrier signal frequency. A coupling circuit selectively decouples the antenna from the DCR and couples the offset signal to the mixing module to generate a baseband test signal in the I and Q signal paths for determining an imbalance in the amplitudes of the baseband test signals between the I and Q signal paths.

Method and circuit for estimating in-phase/quadrature signal amplitude imbalance

A two-way radio ( ) that has a radio frequency receiver ( ) having a modulated radio frequency signal output and a variable bandwidth filter ( ) with an input coupled to the modulated radio frequency signal output. The radio ( ) also has demodulator circuitry ( ), a speaker ( ) and processing circuitry ( ). In use when the radio ( ) is operating in squelch mode, the processing circuitry ( ) controls the variable bandwidth filter ( ) to have a first bandwidth and when in unsquelch mode the processing circuitry ( ) controls the variable bandwidth filter ( ) to have a second bandwidth which has a smaller frequency range and the first bandwidth.

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Sungai Petani, Malaysia

Chow Loong Cheah