An Novel Compact Quadrature Hybrid Using Broadside-Coupled Meander Lines

Abstract

In this paper, we present a novel compact 3-dB quadrature directional coupler by introducing Hilbert curve to the conventional meander line structure. The proposed coupler uses a modified broadside coupled meander lines featuring Hilbert curves to achieve a smaller size. The structure of the coupler is suitable for multilayer printed circuit board (PCB) implementation. The proposed coupler with an operation range of 470 MHz–860 MHz is verified by the accordance of simulation and measurement with a measured return loss and isolation better than 19 dB and exhibiting a coupling of 3.4±0.5 dB in the working frequency range. The dimension of the manufactured coupler is 11.50 mm × 8.90 mm × 1.70 mm. It is the smallest coupler to the authors' knowledge in the frequency range of 470–860 MHz.