A 60 GHz single-chip 256-element wafer-scale phased array with EIRP of 45 dBm using sub-reticle stitching

This paper presents a 60 GHz wafer-scale transmit phased-array with 256-elements spaced λ/2 apart in the x and y directions, and occupying an area of 4.14×4.2 cm² (1740 mm²). The phased array is built using independent RF, transmission-line and control circuit blocks which are stitched together to form an aggregate chip which is much larger than a standard reticle (22×22 mm²). This method allows for a wafer-scale design and can be extended to any size and any shape (rectangular, hexagonal, etc.) up to the edge of the wafer. The blocks include high-efficiency on-wafer antennas, phased-array channels with 3-bits amplitude and 5-bits phase control together with an amplifier having an output power of +3 dBm at 60 GHz. Also, a highly redundant RF distribution network is synthesized from several stitched blocks for improved yield, and the control blocks have redundant SPI control and power strips, also for improved yield. The 256-element array results in a half-power beamwidth of 6° in the E- and H-planes, a directivity of 29 dB, and scans to +/− 55° in the E- and H-planes with near-ideal patterns and a cross-polarization level of <−25 dB. The measured EIRP is 45 dBm at 61 GHz and with a 3-dB bandwidth from 58 to 64 GHz. To our knowledge, this is the largest single-chip phased-array ever developed and allows the construction of large-scale (1000+ elements) phased-array systems, either on a single wafer or by assembling several of these chips together.