초록 ▼

A high Q bandpass filter (102) is tuned by applying a transient (204) to the filter to cause it to ring. The ringing of the filter produces an output damped oscillatory waveform (206) whose zero crossings (208) are converted to a pulse train (210) and counted in a digital counter (112) to a predeter

A high Q bandpass filter (102) is tuned by applying a transient (204) to the filter to cause it to ring. The ringing of the filter produces an output damped oscillatory waveform (206) whose zero crossings (208) are converted to a pulse train (210) and counted in a digital counter (112) to a predetermined number n. The output (214) of the counter is compared to an accurate timing signal (216) which has a time duration equal to the time of n pulses when the filter is accurately tuned. The output of the comparator (118) is applied to an integrator (122) to generate a control signal V.sub.c to tune the filter. The high frequency tuning problem is thus converted to a low frequency, time domain problem which is readily implemented.

대표청구항 ▼

[ What is claimed is:] [4.] Apparatus for detecting the filter pole frequency of a filter, comprising:a pulse generator for exciting said filter with a pulse for causing said filter to ring to generate an oscillating waveform;a counter coupled to said filter, for counting a predetermined number of o

[ What is claimed is:] [4.] Apparatus for detecting the filter pole frequency of a filter, comprising:a pulse generator for exciting said filter with a pulse for causing said filter to ring to generate an oscillating waveform;a counter coupled to said filter, for counting a predetermined number of oscillations in said oscillating waveform generated by said ringing of said filter; anda comparator, coupled to said counter, for comparing the elapsed time of said predetermined number of oscillations with a known reference time.