Multi-functional Bandpass Filter with Co-designed Tunable Attenuator and Reflectionless Phase Shifter Functionalities

A multi-functional bandpass filter (BPF) with two switchable modes of operation, namely: i) a co-designed reflectionless bandpass filter and variable phase shifter (BPFVP) with 360° shift and ii) a co-designed bandpass filter andvariable attenuator (BPF-VA) is reported. The multi-functional BPF can also be intrinsically switched-off when operating in the BPF-VP mode. As key advantage to be highlighted, the proposed component combines four different functions, namely BPF, phase-shifter, attenuator and RF switch into a single RF compact reducing the size of the RF front-end. As a proof-of concept, a multi-layer prototype was manufactured and tested. It exhibited i) a third-order BPF-VP centred at 700 MHz with a 360º continuously tunable phase and a reflectionless bandwidth between 375 MHz to 1.093 GHz, ii) a switching off state with > 25 dB of isolation, and iii) a third-order BPF-VA mode centred at 700 MHz with tunable attenuation between 4-25 dB.