| 摘要 |
<p>In a TDM/TDMA portable radio communications system (5), a portable handset (201) is compatible for operation in FDD mode and TDD mode. In the FDD mode, different frequencies are used to separate a downlink transmission to a portable (201) from a port (204) from an uplink transmission from a port (204) to a portable (201). In the TDD mode, uplink and downlink transmissions are separated in different time-slots, but at the same frequency. The handset (201) includes common transmit and receive circuitry (300) that operates at fixed IF frequencies separated by the fixed FDD frequency difference between corresponding uplink and downlink signals. In the FDD mode, a frequency synthesizer (301), which is used to tune to transmit and receive at different frequencies from different ports, is not switched in frequency between transmitting and receiving a burst to and from a single port. In the TDD mode, the synthesizer (301) is switched in frequency between transmitting uplink and receiving downlink even though uplink and downlink signals are at the same frequency.</p> |
