Millimeter-wave Phased-arrays for Communication and their System-Level Impairments and Advantages
- Author(s): Rupakula, Bhaskara Rao
- Advisor(s): Rebeiz, Gabriel M
- et al.
This dissertation presents millimeter-wave transmit/receive phased-arrays at 60 GHz, which are used to demonstrate long-range and high data-rate communication links. A 32-element one-dimensional (1-D) phased-array is built with 2$\times$2 beamformer chips flipped on a low-cost printed circuit board. Series-fed microstrip antennas are used, which limits the bandwidth to around 2 GHz at 64 GHz center frequency. The phased-array scans only in the azimuth plane with a 3$^o$ beamwidth and has a wide beam of 12$^o$ in elevation. The phased-array's high effective isotropic radiated power (EIRP) of around 42 dBm and low noise figure of 6.5 dB enable long-range communication at 500 Mbps over 800 m.
A two-dimensional (2-D) scanning phased-array is also built using the same beamformer chips on a more complex multilayer board. The 2-D phased-array has an EIRP of 45 dBm in saturation and scans up to +/- 15$^o$ in the elevation plane and +/-50$^o$ in the azimuth. Stacked microstrip antennas are used, enabling a wide bandwidth of $\sim$8 GHz for the phased-array. Data-rates of up to 30 Gbps are achieved with 64-QAM modulation using the full bandwidth of the phased-array.
An analysis of intermodulation effects in receive-mode phased-arrays is presented and verified through experimental results from a Ka-band 5G phased-array. The intermodulation products are shown to peak at scan angles which do not correspond to the interferer directions.
Experimental evidence is presented to show that the adjacent channel power ratio (ACPR) of transmit phased-arrays improves with larger number of elements at a given backoff from the compression point. This implies better transmit efficiency in larger phased-arrays.
Finally, techniques are presented for reducing the number of phase-shifters in a 2-D phased-array while maintaining a limited scan range in the vertical and horizontal planes. It is shown that the number of phase-shifters can be reduced by 75\%, while maintaining a scan range of +/-15$^o$ in the elevation and +/-40$^o$ in the azimuth.