| 摘要 |
A transmit-receive switching circuit of a wireless communication system comprises a selecting portion for switching the communication system in a waiting mode into a master; a controller for determining a transmit-receive frequency according to the operating of the selecting portion and generating a control signal; a band selecting portion for selecting an inputting signal of an upper band or a lower band of a receiving signal passed through an antenna and a duplexer according to the control signal of the controller; a first switching portion for selecting an upper band pass filter and a lower band pass filter that are operated by the band selecting portion; an amplifying portion for amplifying a receive signal passing through the switching portion; a second switching portion for switching the receive signal amplified at the amplifying portion according to the operating signal of the band selecting portion and determining to be supplied to an upper band filter or a low band pass filter of a second filtering portion; a mixer for mixing the receive signal passing through the second filter with a local oscillating frequency from a local oscillator; a filtering portion for filtering an intermediate frequency from the mixed frequency; and a transmit mode determining portion for determining/transmitting a transmit frequency according to a signal outputted from the band selecting portion. Therefore, as any one of the wireless mobile communication systems is determined as a master to try the communication, the master switches the transmit-receive frequency bands into those contrary to the slave, thereby preventing the intervention of the transmit-receive frequencies with the slave and enabling the communication between the master and the slave at the same time.
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