| 摘要 |
An IF circuit suitable for use in a cellular telephone transceiver includes a first mixer circuit receiving an rf signal and a first local oscillator signal and producing a first signal. The first signal is amplified by a first amplifier to produce an amplified second signal. A first impedance matching circuit receives the second signal and matches it to a first impedance. A double-mode resonator SAW bandpass filter with a bandwidth of approximately 30 kilohertz and a noise figure less than 5 dbm produces a filtered third signal in response to the second signal. A second impedance matching circuit is connected to receive the third signal after it is filtered by the double-mode resonator SAW bandpass filter, and impedance matches it to a second impedance. A second amplifier receives and amplifies the third signal. A second mixer circuit receives the fourth signal and a second local oscillator signal, and produces an IF signal.
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