A Compact Dual-Band Branch-Line Coupler Based on the Interdigital Transmission Line

A dual-band (DB) microstrip branch-line coupler with quadrature phase difference based on the interdigital transmission line (TL) is presented. Interdigital TLs are realized by cascading interdigital capacitors (cells of the structure) in series. The design procedure to reach the dual-band interdigitaltransmission lines at two arbitrary frequencies is presented. Dual-band operation for branch-line coupler is achieved by implementing the interdigital TLs with 3 cells in each branch to provide a phase of - 900 at the lower operation frequency band (2GHz) and - 2700 phase shift at the upper frequency band(3GHz). Branches length is approximately g λ 0.8 and as compared to the conventional DB composite right/left handed (CRLH) branch-line couplers, the proposed structure achievessmaller dimension. Also, simulation results show that the dualband proposed coupler exhibits an amplitude balance of ±2 dBfrom 1.9 GHz to 2.2 GHz in the lower band and from 2.8 GHz to 3.2 GHz in the upper band. Moreover, at mentioned frequency bands, the phase difference between the coupled and through ports is 900 ±100

کلیدواژه ها:

Interdigital capacitor ، branch-line coupler ، dual-band component ، composite right/left handed(CRLH