Voltage-Controlled Tunable Filtering Attenuator Using PIN Diodes

In this brief, a voltage-controlled tunable filtering attenuator using PIN diodes is proposed. A coupled-line structure loaded by PIN diodes is utilized to realize the integration of filtering and attenuation. The ideal circuit of the proposed tunable filtering attenuator is derived and analyzed by odd- and even-mode method. For demonstration, a filtering attenuator prototype with inductors and capacitors for the DC bias circuit is fabricated, where the measured results agree well with the corresponding simulations. The measured results show that the filtering attenuator can realize the attenuation of $2.76 \sim 16.99$ dB within a bandwidth from 1.34 GHz to 2.65 GHz when the DC bias voltage is changed from 0 V to 0.62 V.