| 摘要 |
PURPOSE: A device for eliminating self-quieting of a mobile communication terminal is provided to insert a filter between a local oscillator and an up-mixer to eliminate 76-channel self-quieting occurring in a mobile communication terminal that uses 85.38MHz as a receiving intermediate frequency and 130.38MHz as a transmission intermediate frequency at an AMPS(Advanced Mobile Phone Service) mode. CONSTITUTION: In a mobile communication terminal, signals received through a duplexer are amplified by an LNA(Low Noise Amplifier) and restored to baseband voice signals by a baseband processor. And the baseband voice transmission signals are converted to RF(Radio Frequency) signals by an up-mixer(8) and amplified in a PAM(Power Amplifier Module) then radiated through the duplexer. A filter or a serial resonator is inserted in serial or parallel between the up mixer(8) and a local oscillator(11) applying local oscillating signals to the up mixer(8), in order to eliminate 2-multiplying signals of local oscillating frequencies upon transmitting voice signals. For a 800MHz band of single band/dual mode type terminal, the filter inserted between the up mixer(8) and the local oscillator(11) is constructed by serially inserting a notch filter or a low-pass filter configured by connecting an inductor(H1) having a predetermined value and a capacitor(C1) in parallel.
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