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A novel ultra‐compact wide‐band microwave cross‐over using lumped components is presented for the first time. The proposed cross‐over is composed by inductors and capacitors, and the explicit design equations are derived based on the even–odd mode method. The size of the proposed cross‐over is 1 × 1 cm2, and the bandwidth is 20–30%. Full‐wave electromagnetic simulations are performed and an experimental prototype is fabricated to demonstrate the novel design concept. The measurement results match well with the theoretical and numerical results. [ABSTRACT FROM AUTHOR]

The design and implementation of dual‐band duplexers is presented. The proposed method works well for duplexers with narrow bandwidths and it gives the designers the flexibility to achieve desired return loss levels at different frequency bands. To verify the design concept, dual‐band duplexers based on cavity‐type resonator topologies are designed, fabricated and tested. Good agreement is achieved between the theoretical synthesis results, the simulation results and the measurement results of the duplexer prototype. [ABSTRACT FROM AUTHOR]

A novel dual‐band transmission line with flexible phase shifts is presented. To realise dual‐band operations, the proposed transmission line is constructed by series‐connected coupled lines and open‐ended stubs. Using this structure, flexible characteristic impedances and electrical lengths can be designed to operate at two frequencies. Moreover, the proposed dual‐band transmission line features a wide range of realisable frequency ratios and a flexible structure. For practical applications, a planar dual‐band 3 dB branch‐line coupler operating at 2/5.2 GHz is designed using the proposed dual‐band transmission line. The simulation and measurement results agree very well with the design theory. [ABSTRACT FROM AUTHOR]

A novel dual‐band balun is presented. The designed 3‐port balun is based on a 4‐port structure with the fourth port terminated as an open end. Being a 4‐port symmetrical network, even–odd‐mode analysis is used to analyse the balun's performance. Based on the derived explicit design equations, a balun is designed to operate at 1.1 and 2 GHz. Numerical simulations show a low reflection coefficient S11, equal magnitude of −3 dB as well as 180° phase difference at the output ports. To validate the theoretical and numerical simulations, the proposed balun is fabricated on the FR4 Isola printed circuit board and measurement results match well with the design theory. [ABSTRACT FROM AUTHOR]