| 摘要 |
PURPOSE: A loop filter compensation circuit of a frequency mixer is provided to realize optimum phase noise and spurious noise over a wide range of frequency by controlling a time constant of a loop filter. CONSTITUTION: According to the loop filter compensation circuit of a frequency mixer, a loop filter comprises a number of resistors connected on a connection line between a charge pump and a voltage controlled oscillator, and a condenser(C1,C2) connected serially between the resistor and a ground. A varactor diode(VD1,VD2) has a cathode and an anode connected between each condenser and the ground in sequence. And a coil(L1,L2) is connected in parallel between each condenser and the varactor diode, and controls capacitance of the varactor diode by adjusting a bias voltage inputted from the external.
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