Design of a Planar Transmission Line Balun Based on Novel Phase Inverter

Abstract

In this paper, a planar ultrawideband (UWB) transmission line balun based on a novel phase inverter is proposed, which consists of three coaxial connector to double-sided parallel-strip line (DSPSL) transitions, a two-section Wilkinson divider, and a phase inverter. In the phase inverter, a 90-degree rotating transition is applied to realize field inversion. It maintains good structural uniformity of the two outputs of the balun and ensures the characteristics of equal energy division and a stable 180-degree phase difference in wide frequency band. Compared with other designs, the proposed balun has the advantages of easy to design, UWB operation, low reflection, equal power division and a stable phase difference. The presented balun works in the 0.52 GHz to 2.32 GHz band, covering 4.46 octaves. The measurements can achieve the reflection, amplitude imbalance and phase imbalance characteristics below −15 dB, ±0.46 dB and ±4 deg, respectively. The designs including the phase inverter and balun are fabricated and measured to verify the performance, and the measurements are found to be in good agreement with the simulations. In addition, the UWB potential of the porposed balun is studied. From an example based on a 1:2 balun, we can conclude that the proposed balun has the potential to work in a wider frequency band within the range of 0.1 GHz to 3GHz.INDEX TERMS Double-sided parallel-strip line (DSPSL), phase inverter, transmission line balun, ultrawideband (UWB).

Wideband Broadside-Coupled Line Baluns Enabled by Multimaterial Additive Manufacturing

“…Multilayer printed circuit board (PCB), low-temperature co-fired ceramics (LTCC), monolithic integrated circuits (MMICs), and CMOS, are among the most common integration technologies for the realization of compact planar baluns and many unique design approaches have been demonstrated to date. These include 180 • power-dividing baluns using cascaded unit cells [7], [8], [9], power division configurations followed by phase inversion [10], [11], [12], [13], [14], [15], and slot line resonator approaches [16], [17], [18], [19], [20], [21]. Although wide FBWs above 150% have been reported with these techniques, most of the resulting baluns have large physical sizes with footprints ∼0.25 λ 2 g or larger.…”