Device and method for controlling frequency characteristic of a filter

DETAILED DESCRIPTION It is therefore an object of the present invention to provide a receiver capable of insuring a stable frequency characteristic and desirable receipt frequency despite any frequency offset ascribable to temperature variation, using the fact that the frequency characteristic of a filter can be shifted by a control current.
It is another object of the present invention to provide a receiver capable of reducing the influence of a frequency offset ascribable to temperature variation without resorting to a reference signal generator or reference signal.
It is another object of the present invention to provide a receiver capable of reducing, with a narrow band design, the influence of a frequency offset ascribable to temperature variation by shifting the pass band of a filter in matching relation to the frequency offset.
In accordance with the present invention, a receiver includes a radio section for amplifying a received signal to thereby output an amplified signal.
A filter inputs the amplified signal and has a preselected frequency characteristic.
A feeding section feeds a first control signal to the filter.
A first outputting section outputs a second control signal corresponding to the frequency of said signal.
A second outputting section outputs a third control signal corresponding to a difference between the second control signal and a preselected reference value.
A control section controls the preselected frequency characteristic of the filter in accordance with the first control signal and third control signal.
It is desirable that the amplified signal is a frequency converted signal.
It is desirable that the filter is a gyrator filter and the receiver is a radio pager.
Further, it is desirable that the first control signal, the second control signal and the third control signal are a control current, a DC voltage, and an error current, respectively.
Moreover, it is desirable that the second outputting section converts a difference between a center voltage of the DC voltage and the preselected reference voltage to the error current