A 90 Degrees Waveguide Hybrid With Low Amplitude Imbalance In Full W-Band

This paper reports a high-performance 90 degrees waveguide hybrid coupler working in the full W-band. We demonstrate an 8-branch hybrid which features the low amplitude imbalance over a wide band by first increasing the waveguide height inwards and second introducing waveguide height discontinuity sections on the other inner side. Such a compact and robust waveguide hybrid coupler can be implemented in a split-block easily by current computer numerical control milling technology. The measured results show that the reflection and isolation are better than 16dB, the amplitude imbalance is less than 0.8dB, and the phase difference is within 90-4.25 degrees/+2.38 degrees, which are close to the simulations in most of the W-band.