Thin‐film barium strontium titanate varactor tunable dual‐band quadrature hybrid coupler

Abstract

AbstractA thin‐film barium‐strontium‐titanate (BST) and a conventional silicon varactor tunable dual‐band quadrature hybrid couplers are characterized and compared in this article. Both structures are composed of four quarter‐wavelength sections at a frequency located between the two operating frequencies, and with two pairs of open‐ended stubs. Frequencies tuning make used of BST interdigital and silicon varactor diode capacitors connected at the open‐ended stubs. The characterized BST interdigital capacitor presents a capacitive‐tunability of 52% through an applied voltage of 0 to 25 V, while 82.5% is for the selected commercial silicon varactor diode. The silicon varactor‐tuned dual‐band coupler exhibits 45.9 and 5.2% center operation tuning frequency for the first and the second band, respectively, while 29.2 and 4.3% are achieved by the BST tunable coupler. With two‐tone nonlinear characterization test, the BST tunable coupler biased at 0 and 25 V presents a better IP3 of +25.45 and +35 dBm, respectively, while +11.5 and +34 dBm are obtained for the silicon varactor tunable coupler. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:858–867, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26719