Dual-band modified cross-coupler with large power division ratios

This paper presents the design and optimization of microstrip cross coupler, starting from the concept of 90° hybrid, that can operate in two frequency bands. Large power division ratio is achieved in the dual band by enhancing the length of the conventional 0 dB coupler (cross-coupler). The proposed circuit also features compact size and planar structure. Microstrip cross-coupler operating in the two frequency bands (1.28 to 1.695 GHz and 2.71 to 3.305 GHz) with corresssponding minimum return loss frequencies of 1.6 GHz and 2.9 GHz is designed through circuit theory approach and optimized using Ansoft HFSS software. The power division ratios obtained at 1.6 GHz and 2.9 GHz are 16.38 dB and 15.79 db respectively. In integrated circuit, considering h ≤ 0.01λ (h=substrate height) so that step discontinuity reactance becomes negligible, no compensation technique is required. The same quadrature phase relationship is obtained between the input and coupled signals at the two operating frequencies.