Broadband Millimeter-Wave Beamforming Components Augmented With AMC Packaging

For future millimeter-wave beamforming applications, the improved designs of crossover and 90° hybrid coupler are prototyped. The wideband response of 30% is achieved at the center frequency of 30 GHz. The planar-single-layered structures are developed by using microstrip line technology, which is further augmented with the separate layer of artificial magnetic conductor packaging. The aim is to minimize the spurious radiation caused by the bends and discontinuities in the beamforming networks. For simulation purpose, CST Microwave Studio is used, and designs are fabricated and measured. For the first prototype, the measured crossover insertion loss is about 0.5 dB with ±0.15 dB variation within the operating region. The isolated ports show a maximum level of -15 dB. For the second prototype of hybrid coupler, -3.7 dB is measured at transmitted (S
₂₁
) and coupled ports (S
₃₁
) with the variation of ±0.25 dB as a magnitude imbalance between the output lines. The couplers' isolation (S
₄₁
) level is less than -15 dB. The through/coupled port phase difference (∠S
₃₁
- ∠ S
₂₁
) is 90° with ±3° variation in extreme cases within the frequency band of operation.