| 摘要 |
A filter is provided to stabilize a resonant frequency by adjusting an inductance value of a coil varied according to an influence of peripheral environment, as a capacitance value. A filter includes a coil(L), a varactor(VD), and a voltage unit(20). The varactor varies capacitance according to a voltage applied to the coil. The voltage unit varies the capacitance value by varying the voltage applied to the varactor. One or more varactor is connected in a normal direction or a reverse direction. The voltage unit includes a digital/analog converter(DAC) and a memory(21). The digital/analog converter converts a digital signal to an analog signal. The memory stores a data value for varying the capacitance value of the varactor through the digital/analog converter. |
