An automatic adjustment circuit for adjusting the time constant of a filter circuit. The adjustment circuit includes a source of reference frequency signal, an oscillator for generating an oscillation signal, and a detector for detecting the difference in one of phase and frequency between the reference frequency signal and the oscillation signal and generating a control signal for automatically adjusting the time constant of the filter circuit.

Time constant automatic adjustment circuit for a filter circuit

A method and system for tuning a tunable bandpass filter includes a bandpass filter having a passband which is dependant on the value of a tuning signal. A data signal having a dominant frequency component is applied to the filter and the power of the signal passed by the filter is determined. The tuning signal is adjusted until the passed power is maximized, indicating that the filter is tuned to the dominant frequency. The tuning signal can then be applied to other tunable circuits, including an oscillator having an output used as a clock signal to extract data from the data signal applied to the filter.

Bandpass filters with automatic tuning adjustment

An apparatus and method for calibrating a yttrium-iron-garnet-tuned filter (YTF) is disclosed. Instead of using both tune+span information from the 1st LO, only the sweep ramp used to span the 1st LO is used for the YTF's s own swept spans, and the YTF has its own tune information created independently of tune of the YIG oscillator. This allows calibration at any time, both in the factory or in the field.

Frequency-tuneable filter calibration

An automatic filter adjusting apparatus including an adjustable filter having an input and an output, a reference signal generator for providing a reference signal to the filter, a generator for generating an adjusting signal used to adjust the filter, a comparator for comparing the output of the filter to a reference level and a controller for controlling the adjusting signal generator.

Automatic filter adjusting apparatus

A variable band-pass filter circuit includes a variable band-pass filter (12) which filters an input signal such as a chrominance signal. An output of the variable band-pass filter is phase-compared with a reference signal in a phase comparator (22). An output of the phase comparator is applied to the variable band-pass filter as a control signal. The output of the variable band-pass filter is level-limited by a limiter (24) and then applied to an adder (18) which further receives the reference signal. One of the input signal and an output of the adder is selected by a switch (14) to be applied to an input of the variable band-pass filter. A reference signal component is removed by a sample hold circuit to be prevented from being outputted from an output of the variable band-pass filter.

Variable band-pass filter circuit

Automatic tuning circuit for voltage controlled filters, by digital phase control, including an oscillator and a path to be filtered associated with the voltage controlled filter, wherein the voltage controlled filter must be adjusted on a frequency equal or shifted by a preset amount with respect to the oscillator frequency, including means to scan the filter response while it is fed by the signal of the oscillator, means to detect the shift (positive or negative) of the filter response with respect to the oscillator frequency, means to measure in a digital way such a shift and arranged to provide a signal to correct the filter response, and means for digital storage of that correction signal.

Automatic tuning circuits for voltage controlled filters, by digital phase control

This invention relates to an improvement in circuits for the automatic tuning of voltage controlled filters, using digital phase control.

Quagliarello Giuseppe

Papers

Automatic tuning circuits for voltage controlled filters, by digital phase control

Improvement in circuits for the automatic tuning of voltage controlled filters