Three-Layer Compact K/Ka Feed Chain Using Enhanced Ortho-Mode Junction

This letter presents a compact dual-band dual circular polarization feed chain consisting of only three metallic layers. The minimum number of layers are accomplished by applying an asymmetric architecture based on an enhanced ortho-mode junction (OMJ) with single quad-ridge waveguide machined in one layer. This solution achieves the compactness of the feed chain while maintaining outstanding electrical performance. The feed chain in the band of 17.7–21.2 GHz and 28.2–31.4 GHz is designed and measured. The measured results show that the reflection coefficient of the common port is less than 19.2 dB, the reflection coefficient in both operative bands is better than 25.5 dB, the left-hand circular polarization (LHCP) to right-hand circularly polarization (RHCP) isolation is higher than 20.3 dB, the transceiver isolation is higher than 40 dB, and the axial ratio is below 0.35 dB. The measured results are in great agreement with predicted ones.