Design of Dual-Band Power Dividers and Baluns

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details


The main goal of the project is to develop circuit structures and synthesis methods of dual-band power divider and dual-band balun with design flexibility. In modern communication systems, Wilkinson power dividers are useful because of they can provide in-phase output signals with equal or unequal power ratios and with high isolation. They can be used in the beam-forming network, combiner of power amplifier, combiner of transceiver, interference measurement of receiver, and calibration of power meter. Since Wilkinson power dividers require structures with uniform impedances and specific wavelengths involved, they only can be used for single band applications. For this reason, how to enable a single Wilkinson power divider operated in dual bands is a popular research topic recently. In this research, we propose the stepped-impedance-stub line to replace the traditional /4 line for Wilkinson power divider design. By taking the advantage of non-uniform impedance distribution, the stepped-impedance-stub line can have an equivalent 90 electrical length in dual bands. According to the aforementioned, this project is engaged in three designs of power divider: (1) Synthesis of dual-band Wilkinson power divider with equal power division, (2) Dual-band Wilkinson power divider with unequal power division, and (3) Design of tri-section dual-wideband Wilkinson power divider. The proposed stepped-impedance-stub line can have dual-band performance and is smaller than the conventional T-shaped line because of its increased non-uniform impedances. The synthesis method is developed and found that it has two degrees of freedom which can be exploited to increase the range of frequency ratio, miniaturize circuit size, and replace impractical impedances with more realizable ones. Besides, this project will also develop the dual-band baluns. As it is well known, the differential circuits have an ability to reduce the noise from power sources, coupling of approximate circuits, and interference of external electromagnetic signals. Many wireless transceivers have changed their circuit structures from single-ended type to differential type. Baluns are required to provide the differential mode signals with equal power and opposite phase for differential circuits. Recently, dual-band baluns become a popular research topic. The circuits presented in published literature usually accompany with disadvantages like a narrow range of frequency ratio, impractical of high or low impedances, and a large size, which can be improved by using the stepped-impedance-stub line. Based on the proposed dual-band power divider and integrated with two novel phase reversal structures, it is possible to obtain 180 phase difference at dual frequencies for design of dual-band power dividers. The phase reversal swap is achieved by interchanging the two coupled lines so that the signal is reversed to obtain opposite phase. It is well suited for compact, low-cost, and easily fabricated applications in RF and microwave circuit design. This research will develop three dual-band power dividers and two dual-band baluns with stepped-impedance-stub lines. In addition to the formulation and simulation, we will also fabricate and measure several prototypes to demonstrate the capability of the proposed circuit structures.

Project IDs

Project ID:PB10007-2096
External Project ID:NSC100-2221-E182-060
Effective start/end date01/08/1131/07/12


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