Multi-Functional Single/Multi-Band Bandpass Filters With Co-Integrated RF Isolator, Variable Phase Shifter or Variable Attenuator Functionalities

This manuscript introduces a novel RF co-designmethodology that allows to co-integrate the functionality of asingle-/multi-band bandpass filter (BPF), an RF switch, a variablephase shifter (VP), a variable attenuator (VA), and an RFisolator within a single multi-functional RF component. It isbased on a power reconfigurable rat-race coupler (RFRC),spatiotemporally modulated (STM) resonators and a switchablephase coupling element that controls three modes of operation.These include: 1) a co-designed single/multi-band reflectionless BPF, an RF isolator (enabled/disabled by turning ON/OFF STM)and a 360 degrees-variable phase shifter (BPF/BPFI-VP), 2) an RF switching mode and 3) a single/multi-band BPF, an RF isolator(enabled/disabled by turning ON/OFF STM) and a variableattenuator (BPF/BPFI-VA). A detailed theoretical frameworkis provided alongside a variety of single-band and multi-banddesign examples. The methodology is validated through the implementation of a single-band prototype (Prototype 1) anda dual-band prototype (Prototype 2) at 700 MHz. Specifically,Prototype 1 features a single-band BPF/BPFI-VP mode with continuously tunable phase shift of 360 degrees while having constant transfer function (TF), a wide reflectionless bandwidth (RBW)from 375 to 1093 MHz as well as uni-directional transmission with over 20 dB directivity (D). When reconfigured in its BPF/BPFI-VA mode, a wide attenuation tuning range of 15.8 dBcan be obtained with a well-preserved TF, low phase imbalance(<5 degrees)and D>20 dB. Furthermore, it can be intrinsically switched-off with an isolation>30 dB. Prototype 2 supports athird order dual-band TF with 360 degrees tunable phase shift capability for both of its bands. Furthermore, it exhibits a RBW between 370-1200 MHz, switching-off capability with>30 dB of IS and with D>10 dB