A Hybrid Integration Strategy for Compact, Broadband, and Highly Efficient Millimeter-Wave On-Chip Antennas

A novel hybrid integration strategy for compact, broadband, and highly efficient millimeter-wave (mmWave) on-chip antennas is demonstrated by realizing a hybrid on-chip antenna, operating in the [27.5–29.5] GHz band. A cavity-backed stacked patch antenna is implemented on a 600
$\mu$
m thick silicon substrate by using air-filled substrate-integrated-waveguide technology. A hybrid on-chip approach is adopted in which the antenna feed and an air-filled cavity are integrated on-chip, and the stacked patch configuration is implemented on a high-frequency printed circuit board (PCB) laminate that supports the chip. A prototype of the hybrid on-chip antenna is validated, demonstrating an impedance bandwidth of 3.7 GHz. In free-space conditions, a boresight gain of 7.3 dBi and a front-to-back ratio of 20.3 dB at 28.5 GHz are achieved. Moreover, the antenna is fabricated using standard silicon fabrication techniques and features a total antenna efficiency above 90% in the targeted frequency band of operation. The high performance, in combination with the compact antenna footprint of
$\text{0.49}\,\lambda _{\rm min} \times \text{0.49}\,\lambda _{\rm min}$
, makes it an ideal building block to construct broadband antenna arrays with a broad steering range.