| 摘要 |
<p>An RF transceiver achieves a fast switching time between transmit and receive modes by leaving the transmit oscillator (12) on all the time. The transmit chain comprises a wide pulling voltage controlled crystal oscillator (12) that operates at one third the transmit frequency followed by a frequency tripler/filter/amplifier chain that can be quickly switched on and off. By operating the transmit oscillator at one third the transmit frequency, only the third harmonic of the oscillator falls into the sensitive receive frequency band. Further isolation during the receive mode is achieved by gating off the frequency tripler, pulling the frequency of the oscillator out of the receive band, electronically detuning the harmonic filter (16) and switching off the transmitter's power amplifier (18).</p> |
