High‐power combiners with terminating resistors for DTV applications in the frequency range of 470–860 MHz

Abstract

In this study, a broadband high‐power combiner for digital video broadcasting‐terrestrial (DVB‐T) applications is presented. The proposed broadband combiner is a combination of a bisection Wilkinson power combiner, some coaxial baluns and 50‐Ω terminating resistors. For increased power capability and wideband performance, the floating resistors are replaced by, two 50‐Ω terminating resistors using coaxial baluns. The wideband combiner is analysed by even and odd mode method. As the inherent capacitance of the terminating resistors is lower compared to the capacitance of a floating resistor, the isolation and return loss are less affected in wideband applications. The proposed power combiner covers the frequency range of 470–860 MHz, which is intended for DVB‐T applications. A second planar wideband high‐power combiner is also introduced in this study as another extension to the proposed power combiner, in which the coaxial baluns have been replaced with overlay quadrature hybrids. This combiner features a planar structure and utilises some standard 50‐Ω terminating resistors as the isolation resistor. The electrical performance of these power combiners is compared to each other. The first and the second power combiners are designed to handle up to 600 and 400 W output power, respectively.

Single section, octave bandwidth,high‐powercombiner in theUHFband

“…The characteristic impedances will be determined by even‐odd mode analysis 18 . In contrast to the combiner presented in Reference 17, the branches are uniform. Two extra branches behind the input ports have been added for matching over a wider bandwidth.…”

“…Two Wilkinson power combiners were presented in Reference 17; a bisection and a single section with multisection branches.…”

“…Two extra branches behind the input ports have been added for matching over a wider bandwidth. Compared to Reference 17, the coupling coefficient of the coupler introduces a degree of freedom for enhanced isolation over a wider bandwidth. The analysis in the following section, leads to the optimized version of the two‐section power combiners with planar transformers.…”

“…Following, 16 a single section Wilkinson combiner was presented in Reference 17, where the 100 Ω resistor was replaced by two quadrature hybrids and two 50 Ω terminations. In that structure, the quarter wavelength branches were divided in three sections with different characteristic impedances for bandwidth enhancement.…”

“…The rest of unknown parameters are Z 2 , Z 3 , Z 0e , and Z 0o . The unknowns have been calculated by Equations (6), 7, (16), and (17). The results have been listed in Table 1.…”