140-GHz Wideband Array Antenna-in-Package Using Multimode Resonance

A 140-GHz wideband array antenna-in-package (AiP) that uses multimode resonance is proposed based on a low-profile multilayer printed circuit board (PCB), which can be incorporated with flip-chip technology and an integrated transceiver. Using the multiple resonances of a patch and
$\lambda $
/4 monopole-type feeder, a simulated impedance bandwidth of 53% and stable radiation performance over the operating band were achieved. A
$4\times $
4 antenna array achieves a gain of up to 18.1 dBi, a radiation efficiency of 80%, and a cross-polarization discrimination (XPD) of over 20 dB. By combining the elements with a feed network composed of striplines, single and
$4\times $
4 antenna arrays were designed and fabricated. The capacitance caused by the limitations of the fabrication process was analyzed and overcome using a novel capped-cavity structure. From the experiment, a −10 dB impedance bandwidth of 31% was measured.