Miniaturized Dual-Band Hybrid Couplers With Arbitrary Power Division Ratios

• Published in: IEEE transactions on microwave theory and techniques Vol. 57; no. 1; pp. 149 - 156
• Main Authors: HSU, Ching-Luh, KUO, Jen-Tsai, CHANG, Chin-Wei
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bands; Branch-line coupler; Circuit design; Circuit properties; Circuits; Couplers; Division; Dual band; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Impedance; Insertion loss; Microstrip; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwaves; Miniaturization; Power transmission lines; Radio frequency; rat-race coupler; Simulation; stepped impedance; Transmission line theory; Wireless LAN; Circuit parameter; Microwave coupler; Branch-line coupler; dual band; Stepped impedance device; Characteristic impedance; Stub line; rat-race coupler; Hybrid coupler; Ring structure; Frequency characteristic; Upper bound; Simulation; Two-port networks; Miniaturization; Transmission line theory; stepped impedance
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2008.2009036

Branch-line and rat-race couplers are designed to have dual-band operation with arbitrary power division ratios. An elementary two-port is proposed to imitate the 90 deg section at the two designated frequencies with different characteristic impedances. The two-port consists of a stepped-impedance section with open stubs attached to its two ends, and its circuit parameters are determined by the transmission line theory. The use of the stepped-impedance sections also leads to circuit miniaturization. By the standard microstrip technology, investigated also includes the realizable power division ratios and circuit bandwidths in the two bands, the upper limit of the ratio of the two designated frequencies and the miniaturization factor of the proposed circuit. Hybrid couplers operating at 2.45/5.2 GHz with various power division ratios are designed, fabricated and tested. Experiment results are compared with the theory and simulation.