Versatile Multiband Power Divider and Branch-Line Coupler With Novel Design Techniques for Future Wireless Applications

Asif Iftekhar Omi

doi:10.7273/000005287

Radio frequency (RF) front-end passive circuit components can support the ever-desired demand for faster, reliable, and ubiquitous wireless systems for application in microwave and mm-wave engineering. Two of such components are power dividers (PD) and branch-line couplers (BLC) which are the prime focus for all the research works conducted in this thesis. The dissertation starts with conventional design and performance of these high frequency components and then gradually develops newer structures along with all the well-articulated design formulations to ensure a versatile performance in multiband operation for both the PDs and BLCs. The frequently used multi-section Wilkinson Power Divider (WPD) design has been an empirical/ table-based technique for 3 or more sections. And hence, it does not lend itself easily to design automation via EDA tools. In contrast, a fully analytical technique has been presented here to design a 3-section wideband WPD and a rigorous analysis is carried out to arrive at the designs equations that can easily be integrated with MATLAB/Octave to quickly find the design parameters. Further, as per the authors’ knowledge, the dual-band technique has never been employed before for designing a wideband component. The proposed technique draws from the dual-band technique, and it has been shown that the proposed scheme to always lead to additional bandwidth while guaranteeing the minimum bandwidth design requirements. Two prototype was also fabricated to validate the results. Measurement of both the prototype exhibits an excellent input return-loss > 16 dB, output return-loss > 15 dB, insertion-loss < 3.30 dB and a remarkable isolation > 20 dB within the band and with 10 dB reference provide a fractional bandwidth of more than 141%. Utilizing this technique even further, a 3-way power divider based on miniaturized Goldfarb topology has been designed which can support any arbitrary band ratio shown for the very first time in such type of structures. Other than the 2-way/3-way multiband RF power dividers, dual-band branch line couplers have also been presented using coupled lines and crossed lines with a new design concept. Making use of this new design topology, the shown BLC structures reveal extremely high band ratio and power division ratio with arbitrary port terminated real impedances. To validate the proposed design concept, a prototype using coupled line working at 0.9GHz and 1.8GHz is fabricated on a 60mil Rogers 4003C substrate exhibiting excellent match between the simulated and measured results. This procedure paves the way to develop many other new BLCs which offer multi-fold novelties.

Versatile Multiband Power Divider and Branch-Line Coupler With Novel Design Techniques for Future Wireless Applications

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