Abstract: The invention relates to a filter device, and is intended to prevent drastic changes of output modulation signal and assures the performance as modulator if output modulation signal is transmitted and stopped frequency by using TDMA in communication control. To achieve the object, the invention comprises a shift register 1, a plurality of memories 2 connected to this shift register 1 and increased in the bit width of input address by one bit each, and a selector 3 for selecting outputs from these plurality of memories 2, in which the output of the shift register 1 is used as a higher side address of each one of the memories 2, a lower side address of each one of the memory addresses is common, the bit width of the higher side address increases by one bit each starting from one bit, and addresses are assigned sequentially from the lower side of the higher side address of the memories 2 depending on the shift from the lowest side bit of the shift register 1.

Abstract: A filter comprises an inductor, a first variable capacitance diode, a second variable capacitance diode having nearly identical characteristic as the first variable capacitance diode, a control terminal for applying voltage to the first and the second variable capacitance diodes, an input terminal, an output terminal and a signal line between the input terminal and the output terminal. A cutoff frequency is controllable with the voltage applied to the control terminal. The variable frequency filter which can receive a large signal has reduced size due to a structure in which the first and the second variable capacitance diodes having nearly identical characteristics are connected either in series or in parallel with their polarities reversed against each other.