Wideband Calibration Network for Multichannel Antenna Array Feeding Network

In this letter, a wideband calibration network using multilayer coupler is proposed for
X
-band antenna array feeding network. A high performance coupler is designed to ensure consistency for the coupling of the series-fed structure. By using a serpentine feedline and making all channels the same length, phase imbalance is decreased. To reduce lateral leakage, cross-talk and mutual coupling, the vias-shielded structure and metal spacer are used. To validate the proposed calibration network design, a wideband calibration network is fabricated and measured. Measured results show that the coupling amplitude fluctuates mainly in the range of 29–37 dB with phase imbalance less than 5°, the isolation of all ports is better than 38 dB and voltage standing wave ratio is less than 1.7.