Coaxial resonator filter with variable reactance circuitry for adjusting bandwidth

Claim 1

A filter with an adjustable bandwidth, comprising: a filter having a predetermined passband and stopband, including an input, an output and at least two resonator structures; a variable reactance element for adjusting the bandwidth of the passband comprising a variable voltage capacitor, coupled between the resonator structures defining a first and a second node; the variable voltage capacitor includes a control signal input whereby the frequency response is adjustable; and the control signal input includes a plurality of possible control voltages to provide a substantially continuous adjustment of the capacitance of the variable voltage capacitor over it's tuning range, including at least a low voltage signal in proximity to a logic zero, a high voltage signal in proximity to a logic one and an intermediate signal therebetween; the low voltage signal provides adjustment to lower the capacitance between the first and second nodes to provide a fine-tune adjustment defining a wider bandwidth; the high voltage signal provides adjustment to raise the capacitance between the first and second nodes to provide a fine-tune adjustment defining a narrower bandwidth; and the intermediate voltage signal provides adjustment to define an intermediate bandwidth between the wider and narrower bandwidth.