Compact 60 GHz Phased-Array Antennas With Enhanced Radiation Properties in Flip-Chip BGA Packages

Compact phased-array antennas embedded in flip-chip ball grid array (BGA) packages are proposed to operate over the unlicensed 60 GHz frequency band. Radiation properties are enhanced by designing novel corrugated soft-surface structures and implementing them using the low-temperature co-fired ceramic process with no extra cost and fabrication complexity. This is achieved by adjusting via land diameters of periodic grounded vias in top four layers of the package, which in fact create perfect magnetic boundaries between the phased-array antenna elements to modify the electric near-field distributions and consequently improve far-field characteristics including gain, cross polarization, sidelobe level, and beam steering. Low-loss transitions from flip-chip IC to antenna elements are designed with less than 0.1 dB amplitude and 2 degrees phase imbalance over 50-70 GHz. Prototypes with/without soft-surface structures are fabricated to work with flip-chip ICs with/without switches. A USB-interface adapter and a waveguide-interface module with a compact vertical power combiner are proposed for the first time to experimentally evaluate the phased-array antenna while connected to the flip-chip RF IC. Significant miniaturizations and improvements are achieved over the wide frequency range of 56-67 GHz, demonstrating up to 7 dB reduction in sidelobe level, up to 4 dB reduction in cross polarization, and up to 3 dB enhancement in gain at different directions.