HIGH-FREQUENCY RADIO CIRCUIT

摘要

The invention relates to the improvement of the reception sensitivity and interference rejection of a high-frequency radio circuit used for a mobile communications device such as a cellular telephone and an information communication terminal. High-frequency radio circuit includes a phase shifter (10) connected between a duplexer (13) and a low-noise amplifier (16) so that the impedance of the receiving terminal of the duplexer (13) at the transmission frequency may not be the complex conjugate of the input impedance of the low-noise amplifier (16). As result, the transmission signal passing through the receiving terminal of the duplexer (13) is prevented from cross modulation in the low noise amplifier due to interference signals input from an antenna (11), thereby improving the reception sensitivity and interference rejection of the high-frequency radio circuit.