| 摘要 |
PURPOSE: An intermediate frequency synthesizer in a wireless communication system is provided to prevent deviation changes by being adaptively operated to temperature changes. CONSTITUTION: An intermediate frequency synthesizer in a wireless communication system comprises a phase locked loop(10), a loop filter(20), a voltage control oscillator(30), a filter(40), a temperature detector(60), and a switch(50). The phase locked loop compares a reference frequency with a predetermined-feedbacked frequency signal, to regularly maintain an intermediate frequency. The phase locked loop outputs an alternating current(AC) signal corresponding to a compared phase difference. The loop filter performs a low pass filtering process for the inputted AC signal, and generates a direct current(DC) signal. The loop filter transmits the generated DC signal to the voltage control oscillator. A value of the inputted DC signal is operated as a forward bias voltage of a varactor in the voltage control oscillator. The voltage control oscillator having the varactor oscillates an intermediate frequency signal. The filter has a low pass filter, a first resistor, and a second resistor. The filter performs a low pass filtering process for an audio and data which are modulated. The audio and the data are inputted through the first/the second resistors. The filter transmits the audio and the data for being modulated to the varactor. The temperature detector senses peripheral temperatures. The temperature detector generates a predetermined switch controlling signal, if a predetermined temperature is detected. The switch inputs the audio and the data for being modulated. The switch transmits the audio and the data to the first or the second resistor, according to the switch controlling signal. |
