Sub-Terahertz-Band On-Chip 2×2 Beam-Forming Array Antenna Using a Compact 2-D BFN On 45nm SOI CMOS

A 150GHz-Band on-chip 2×2 beam steering array antenna based on a compact on-chip 2-D beamforming network (BFN) designed in the 45nm SOI CMOS process of Global Foundry, is proposed in this paper. The proposed 2-D BFN is four inputs and four outputs network consisting of four interconnected 3dB/90
^o
broadside couplers designed using striplines M1, M4, and M5. The 2-D BFN provides the phase responses of (±90
^o
) in x- and y-directions. Its rectangular geometry allows an easy integration with a 2×2 patch array by vias to produces four orthogonal beams in both elevation and azimuth directions. The implementation of the 2-DFN using 3dB/90
^o
broadside couplers improves the compactness and reduces the insertion loss of the circuit. The inter-element distance in x- and y- direction are 0.5λ
0
. The chip areas of the proposed 2-D BFN and 2×2 array module are respectively 0.73×0.73mm
²
and 1.8×1.8mm
²
including the feeding lines and pads. To validate the concept, an ADS momentum simulation of the 2-D array operating in the frequency range of 130-170GHz is performed. The realized peak gain is 10.3dBi with sidelobe level of -14dB. The antenna array provides a total of ±32°/±34° scanning in E and H planes.