This whitepaper is dedicated to quadrature hybrid, which is a four-port device that splits input signal. An ideal quadrature coupler divides power incident on any port between two other ports with a 90° phase difference and equal amplitude. It also isolates the fourth port. In its typical form, a quadrature hybrid is made of two parallel waveguides and a series of apertures between them.
Within this paper, we consider a waveguide quadrature hybrid that employs branch waveguides, which has been proposed in ALMA Memo 343 from 2001 (S. Srikanth, A. R. Kerr, Waveguide Quadrature Hybrids for ALMA Receivers, ALMA Memo 343). It was designed for ALMA receiver as a power combiner in the first local oscillation (LO) system and as an element of balanced sideband-separating superconductor–insulator–superconductor (SIS) mixer. The considered waveguide quadrature hybrid has been designed and analysed with QuickWave FDTD software.
Scheme of waveguide quadrature hybrid proposed in ALMA Memo 343 from 2001.
Simulation model of WR-10 waveguide quadrature hybrid with six branch lines, prepared in QW-Modeller.