Digitally tunable coaxial resonator reflective band reject (notch) filter

摘要

A coaxial tunable band stop filter utilizes tuning elements, such as PIN diodes and varactor diodes, for electrically tuning a coaxial resonator to change the resonance frequency of the coaxial resonators. A voltage is applied to the tuning elements to change their capacitance, such that they electrically lengthen and shorten the coaxial resonator. The variable voltages work to change the center frequency across a bandwidth. When the resonators are electrically extended or shortened in length, the center frequency in the bandwidth is changed accordingly. The bandwidth for the coaxial tunable band stop filter is tunable to increase and decrease based on the position of the center frequency. A ninety degree transmission line is used for coupling the components of the filter. A digital control is used for manipulating the tuning elements.