A microstrip filtering power divider (FPD) with good isolation performance and harmonic suppression is presented. By replacing a simple resistor with a novel distributed stepped-impedance resonator network, better isolation and wider stopband are simultaneously attained. A transmissionmatrix-based analysis method is then extensively described to determine the circuit geometrical parameters at the synthesis level by facilitating the incorporation of design indexes and structure dimension. A prototype FPD is designed, fabricated and measured. The proposed FPD exhibits a center frequency of 2.2 GHz (f 0 ) with the isolation better than 17dB within the entire passband and a stopband extended to 12 GHz (5.45f 0 ). IndexTerms-Filtering power divider (FPD), stepped-impedance resonator (SIR), synthesis design.

A new design method for a compact dual-mode dual-band filtering power divider is proposed. To achieve two transmission poles in both of the two passbands, the odd-and even-mode resonant properties of the dual-mode resonator are employed in the design. By symmetrically locating four dual-mode resonators at both sides of the main transmission line and choosing the proper output topology, the introduced circuit can successfully realise the dual-band power division and filtering selectivity property. Two resistors are utilised to achieve good in-band isolation performance of the filtering power divider. For demonstration, a dual-band filtering power divider with two passbands centred at 2.2 and 2.7 GHz was designed and measured. Simulated and measured results are provided which show a good agreement.

A wideband filtering power divider (FPD) with good isolation and widen upper stopband is presented. A distributed stepped-impedance resonator (SIR) network composed of three short-circuited SIRs and one isolation resistor is introduced to obtain both port-to-port isolation and harmonic suppression. For demonstration, an FPD operating at 2.3 GHz with 3 dB fractional bandwidth of 31% is designed, fabricated and measured. In the operating band, the measured isolation is better than 17 dB, while out of band, the upper stopband is extended to 9.8 GHz (4.2f 0) with a rejection level of 20 dB.

Optically controlled RF switches with a novel non-contact device architecture that achieves high performance in the millimeterwave-to-terahertz (mmW-THz) region are proposed and investigated through simulation. The significant change in conductivity in semiconductors caused by photogenerated carriers is used to develop RF switches having very high performance. By including a thin layer of insulator between the active semiconductor material and the metal contacts, the carrier concentration can be enhanced over that of conventional devices. For a prototype demonstration, G-band coplanar waveguide-based optical switches (using Si and Ge as active materials) with different contact geometries have been modeled and simulated. The proposed switches outperform both conventional solid-state switches and phase-change material-based switches in the switch figure-of-merit, and are promising for developing a novel class of tunable and reconfigurable mmW-THz circuits for advanced sensing, imaging, and communication.