Patent ID: 7688059

Claim:
A filter characteristic frequency adjusting apparatus comprising: a filter: a test signal generation unit for receiving a reference signal, and generating a test signal to be supplied to said filter when adjusting a frequency characteristic of said filter, such that the filter outputs a predetermined filter output signal when the test signal is supplied to the filter; a phase shift unit for phase-shifting the test signal generated by the test signal generation unit so that a predetermined phase difference is generated between the phase of the test signal and the phase of said predetermined filter output signal, based on a phase characteristic of the filter and a frequency of the test signal; and a control signal generation unit for receiving the predetermined filter output signal and the phase-shifted test signal and for generating a control signal which controls a frequency characteristic of the filter, wherein said control signal generation unit comprises: a first comparator for comparing the predetermined filter output signal with a reference signal; a second comparator for comparing an output signal from the phase shift unit with the reference signal; a phase comparator for comparing the phases of binary signals that are respectively outputted from the first and second comparators; and a logic unit for generating the control signal by using the output from the phase comparator and the output from the second comparator, wherein said logic unit comprises: a binary search unit for receiving an output from the phase comparator and an output from the second comparator, and performing a binary search for a result of comparison from the phase comparator at a timing of a rising edge or a falling edge of the output from the second comparator; and a control signal determination unit for generating the control signal based on a value that is obtained by the binary search unit.