ANALOG/MIXED-SIGNAL SPATIAL SIGNAL PROCESSING FOR WIDEBAND MULTI-ANTENNA RECEIVERS

Erfan Ghaderi

The demand for higher data rates has rapidly increased the bandwidth requirement of wireless communication networks. Therefore, next-generation wireless communication requires phased-array systems with large modulated bandwidths and high energy-efficiency ensuring Gb/s data communication. Conventionally, the phased-array systems are implemented by phase-shifter elements to compensate for the inter-element time delays in the received signals. These phase-shifter-based implementations result in limited fractional bandwidth of the receiver. In addition, this limited fractional bandwidth degrades the interference cancellation resulting in unwanted interference leakage. To overcome these limitations, digital true-time-delay-based phased-array systems have been proposed. Digital implementation requires one analog-to-digital converter per antenna resulting in high overall data-conversion power consumption. The needed analog-to-digital converter in the digital implementation must digitize the entire dynamic range of the received signals, including the desired and undesired signals. This dynamic range requirement further increases the analog-to-digital convertor power consumption degrading the power efficiency of a digital phased-array in an interference-dense environment. In this dissertation, baseband analog solutions that can augment the conventional phased-array systems are presented, improving the operating fractional bandwidth. These solutions are implemented in the discrete-time domain where the inter-element delays are controlled digitally. The digitally-controlled inter-element delay offers high scalability in terms of delay resolution, overall delay range, and technology node. The first design is implemented in the charge-domain and a 4-element 100 MHz true-time-delay-based array is fabricated based on this implementation. This design offers a 15 ns time delay range through time-interleaving and a 5 ps delay resolution by phase interpolation. The measurement results prove wideband operation of the receiver while consuming 52 mW power in a 0.9 mm2 area. A baseband discrete-time time-domain implementation is also developed for wideband applications, suitable for next-generation communications. This design leverages digital-friendly technology-scalable time-domain implementation to enhance the system scalability and increase the modulated bandwidth. A 4-element time-domain true-time-delay-based array is designed and fabricated. The time-domain is capable of operation at a 500 MHz modulated bandwidth and enables analog-to-digital conversion through time-domain quantization. The measurement results of the prototype show wideband operation of the array, while consuming 40 mW power and occupying a 0.82 mm2 area.

ANALOG/MIXED-SIGNAL SPATIAL SIGNAL PROCESSING FOR WIDEBAND MULTI-ANTENNA RECEIVERS

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