No abstract

In this study, a planar arbitrary phase‐difference coupled‐line coupler having wide bandwidth, tight coupling coefficient, and small phase variation are proposed. The proposed coupler consists of two quarter‐wavelength coupled‐line sections connected with two different transmission lines. Moreover, the interconnection transmission line can be designed as a small phase variation phase shifter with the introduction of a shorted stub. The detailed theoretical analysis is provided to illustrate the design concept. The circuit parameters of this novel arbitrary phase‐difference coupler can be easily determined by the derived closed‐form equations. For verification, two 3 dB couplers with 45°/135° and 60°/120° phase differences are fabricated and measured. The 45°/135° coupler achieves 34.2% fractional bandwidth for 45° phase difference with 2° phase variation and 36.3% fractional bandwidth for 135° phase difference with 3.4° phase variation. Moreover, the 60°/120° coupler achieves 30% fractional bandwidth for 60° phase difference with 0.9° phase variation and 32.9% fractional bandwidth for 120° phase difference with 1.5° phase variation.

No abstract

To satisfy the requirements of the emerging wireless communication system, the simultaneous implementation of large frequency ratio and tight coupling is demanded for a dual-band coupler. But most of the existing dual-band coupler structures can only achieve one of them. In this paper, a new coupled line based dual-band coupler structure is proposed. The detailed theoretical analysis is conducted for different ranges of frequency ratio. It was shown that a wide frequency ratio from 1.4 to 11.7 can be achieved even for the designs which require a tight coupling of 3 dB. For higher flexibility, the same circuit topology is further investigated to implement the arbitrary power division ratios over the two bands. More importantly, the design parameters for the large frequency ratio and arbitrary power division ratio are found to be almost independent resulting in a simple design procedure. For demonstration purposes, a dual-band 3 dB coupler with a large frequency ratio of 6 is designed, fabricated and measured. Furthermore, another dual-band coupler with coupling coefficients of 3 dB and 6 dB at 2 GHz and 4 GHz is designed, fabricated and measured. Good agreement between simulation and measurement can be observed for both prototypes. INDEX TERMS Dual-band coupler, coupled-line coupler, large frequency ratio, arbitrary power division ratio, tight coupling.

No abstract