Tandem Lange 3-dB 90° hybrid implemented on FR4 substrate

This paper presents a tandem Lange 3-dB 90° hybrid. The hybrid consists of two 8.34-dB Lange couplers connected in tandem and is implemented on a 4-layer flame resistant laminate, composed of woven fiberglass cloth with an epoxy resin binder (FR4) substrate, by using inner-layer crossovers, instead of conventional bonded crossovers. Owing to its optimized tandem structure and inner-layer crossovers, for operating characteristics within the frequency range 440-760 MHz, the hybrid exhibits a power coupling of 3.5 ± 0.6 dB and return losses greater than 23 dB. Furthermore, isolation and phase difference between the output ports is greater than 29 dB and 90° ± 1°, respectively.