| 摘要 |
PURPOSE: A transmitting and receiving apparatus for a mobile communication terminal is provided to decrease the number of VCOs(Voltage Controlled Oscillators) by using two carrier frequencies necessary for a dual band transmitting/receiving apparatus as one, unifying receiving IFs(Intermediate Frequencies) as one, and using the unified one IF. CONSTITUTION: A VCO(301) generates a wireless local oscillation frequency within a certain frequency band under a certain control and outputs the generated wireless local oscillation frequency. A frequency multiplier divides the wireless local oscillation frequency by 2. The first mixer(132) mixes the wireless local oscillation frequency with the first receiving signal with the first frequency band and outputs an IF. The second mixer(131) mixes the divided wireless local oscillation frequency with the second receiving signal with the second frequency band and outputs an IF. The third mixer(233) mixes the wireless local oscillation frequency with a certain IF and outputs the first transmitting signal with the first frequency band. The fourth mixer(231) mixes the wireless local oscillation frequency with the certain IF and outputs the second transmitting signal with the second frequency band. The second switch unit(211) receives the IF and outputs the IF to the third mixer(233) or the fourth mixer(231) according to a transmission frequency band. The first switch unit(140) receives the IF outputted from the first mixer(132) and the IF outputted from the second mixer(131), selects one between two IFs according to a received frequency band, and outputs the selected IF. A filter(142) filters the IF outputted from the first switch unit(140).
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