Renesas Electronics Corporation

Renesas Technology Corp.

Tetsuya Wakuda

Hiroaki Matsui

Kazuaki Hori

Satoru Tomisawa

Sungwoo Cha

Yasunobu Yoshizaki

There is a need to reduce secondary intermodulation distortion that may occur in a reception circuit of a high-frequency signal processor and a wireless communication system having the same. In test mode, for example, a test signal generating circuit TSGEN generates a test signal RFtst at f_tx&#xb1;0.5 MHz. The test signal RFtst is input to a mixer circuit MIXrx_I (MIXrx_Q). A correction circuit block CALBK detects an IM2 component resulting from the MIXrx_I (MIXrx_Q). The CALBK varies a differential balance for the MIXrx_I (MIXrx_Q) and concurrently monitors a phase for the IM2 component resulting from MIXrx_I (MIXrx_Q). The CALBK searches for the differential balance corresponding to a transition point that allows the phase to transition by approximately 180&#xb0;. The MIXrx_I (MIXrx_Q) operates in normal mode using the differential balance as a search result.

High-frequency signal processor and wireless communication system

There is a need to reduce secondary intermodulation distortion that may occur in a reception circuit of a high-frequency signal processor and a wireless communication system having the same. In test mode, for example, a test signal generating circuit TSGEN generates a test signal RFtst at f_tx &#xb1;0.5 MHz. The test signal RFtst is input to a mixer circuit MIXrx_I (MIXrx_Q). A correction circuit block CALBK detects an IM2 component resulting from the MIXrx_I (MIXrx_Q). The CALBK varies a differential balance for the MIXrx_I (MIXrx_Q) and concurrently monitors a phase for the IM2 component resulting from MIXrx_I (MIXrx_Q). The CALBK searches for the differential balance corresponding to a transition point that allows the phase to transition by approximately 180&#xb0;. The MIXrx_I (MIXrx_Q) operates in normal mode using the differential balance as a search result.

In a communication semiconductor integrated circuit, a capacitance included in a filter on the output side of a mixer circuit is reduced without requiring the cutoff frequency of the filter to be changed. A Gilbert cell circuit is used as a mixer circuit which combines, for downconversion, a reception signal and a local oscillator signal. A low-pass filter for removing unwanted waves from output is composed of load resistors of upper stage differential transistors and a capacitive element provided between differential output terminals. The resistances of the load resistors are increased, and a current circuit for applying a current to emitters or collectors of the upper stage differential transistors is provided, so that a current to make up for a decrease in current amount attributable to the increase in load resistance can be applied from the current circuit to lower stage differential transistors.

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Takasaki, Japan

Tetsuya Wakuda