Thanks to a small wavelength (large bandwidth) combined with a low loss transmission window around 94 GHz and 120 GHz, the 75-120 GHz frequency band in millimeter wave (mm-wave) provides a promising opportunity for high data rate long range wireless communications and high-resolution imaging systems. Large-scale phased arrays have been exploited in such application for their beam forming and null steering capabilities, resulting in high directivity and improved SNR. But growing DC power consumption (Pdiss) in such large scale arrays has become an on-going concern along with noise, linearity and phase resolution trade-offs in current phased array architectures. To address these issues, we propose a power efficient phase shifter (PS) architecture based on quadrature hybrid coupler, which leverages the benefits of conventional active and passive PSs at mm-wave. The phase shifter has low loss, resulting in low power dissipation and the power domain phase interpolation by the quadrature hybrid gives low phase error and high linearity. We design W-band (90-100 GHz) phased array transmit and receive (T/R) modules in 130 nm SiGe BiCMOS technology based on the proposed PS and our measurements show high power efficiency with the lowest power consumption at W-band to our knowledge (18mW and 26mW power dissipations at receiver (Rx) and transmitter (Tx) front-ends respectively). Rx shows 23 to 25 dB peak gain, 6 to 9.3 dB NF and Tx can deliver upto 7 dBm output power with 18% power efficiency. Moreover, our PS can achieve 5-bit phase resolution with <2 degrees RMS phase error and provides 0 dBm saturated output power at 94 GHz. The phase shifter (PS) is also scalable beyond W-band without significant loss. We demonstrate this with a 120 GHz two channel phased array receiver (Rx), where a single channel shows 15.6 dB peak gain with Pdiss=53 mW which shows one of the highest gain efficiency (gain/Pdiss) among D-band phased arrays. We can further reduce the power consumption by leveraging the bidirectional signal processing at the phased array front-end. To achieve this, we designed a W-band bidirectional variable gain amplifier with gain variation ranging from 6 to -1 dB at 94 GHz which can be used along with bidirectional PS. The amplifier will replace the lossy SPDT switch in the conventional bidirectional approach, reducing the overall power consumption. / Ph. D. / The wireless technology is pushing towards the high operating frequencies to achieve high data rate and 75-120 GHz frequency band in millimeter wave (mm-wave) are of great current interest for the backhaul communications, radar and imaging systems. However, high frequency yields high propagation loss which has been overcome with large scale phased arrays in such applications for their high directivity, narrow beam forming capabilities and implementation with silicon technologies. The high dissipation due to large number of elements is a major concern which often requires heat sinks around the sensors leading to increase in cost, size and weight. For the large silicon array to be of practical use in commercial systems, it is paramount to maintain a high power efficiency and low power dissipation in the array element. In this research, a power efficient phased array architecture has been proposed which is implemented to design transmit/receive (T/R) modules in advanced silicon technologies. Experimental results show that the proposed architecture achieves the lowest power consumption and improved power efficiency per T/R element among state-of-the-art mm-wave phased arrays. The research also proposes an alternative way to improve power efficiency of phased arrays by reusing the amplifiers in both transmit and receive path where the amplifier replaces lossy switch as well, resulting in a low loss bidirectional system which can reduce the power consumption further. Finally, we believe that this research contribution has an significant impact in the effort of building low power large-scale phased arrays at mm-wave frequencies.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/86859 |
| Date | 01 August 2017 |
| Creators | Afroz, Sadia |
| Contributors | Electrical and Computer Engineering, Koh, Kwang-Jin, Ha, Dong S., Nguyen, Vinh, Raman, Sanjay, Reed, Jeffrey H. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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