| 摘要 |
PURPOSE: An apparatus for controlling a wireless microphone transceiver mute is provided to transceive a non-modulation carrier and a modulation carrier to a transceiving unit at one to two second time intervals when a transceiver power is turned off, by using a 33-40Khz frequency higher than an audio frequency, so as to remove on/off noises of a microphone power. CONSTITUTION: A wireless microphone transceiving circuit comprises as follows. A band pass filter(8) changes a square wave into a sine wave. A control signal size controller(9) controls a size of the band pass filter to transmit a control signal to a modulation input terminal of a voltage control oscillator(VCO). A phase locked loop(PLL) and the VCO decide high frequency carrier frequencies by a data signal of a CPU, and oscillate the high frequency carrier frequencies. A high frequency amplifier amplifies the high frequencies. A high frequency band filter reduces an unwanted copying of the high frequencies. A power switch and a battery power switch power of the high frequency power amplifier. A wireless microphone receiver comprises as follows. A helical filter(21) receives a transmitted propagation. A high frequency amplifier(22) amplifies an output signal of the helical filter(21). A PLL(28) decides a frequency by a CPU(38). A VCO(27) oscillates a voltage of the PLL(28). A first intermediate frequency(IF) converter(23) inputs signals from the amplifier(22) and the VCO(27), and converts the signals into IF signals. A first IF amplifier(24) amplifies the converted IF signals. A second local oscillator(29) makes a second 10.7MHz IF. A second frequency converter(25) inputs signals of the second local oscillator(29) and the first IF amplifier(24), and converts the signals into second IFs. IF filters(26,31) extract the second 10.7MHz IF. A 10.7MHz IF amplifier(30) amplifies signals between the IF filters(26,31). A demodulator(32) demodulates an audio signal. A voice signal amplifier(33) amplifies a voice output signal of the demodulator(32). An audio output switch(34) is controlled by the CPU(38). A low frequency filter(35) passes low frequency signals only. An expander(39) restores a sound signal compressed in a transmitter. A control signal band pass circuit(36) controls the output signal of the demodulator(32). A radio frequency(RF) level meter output line(37) is transmitted to the CPU(38) from the demodulator(32).
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