Beam Pattern Optimization Method for Subarray-Based Hybrid Beamforming Systems

Massive multiple-input multiple-output (MIMO) systems operating at millimeter-wave (mmWave) frequencies promise to satisfy the demand for higher data rates in mobile communication networks. A practical challenge that arises is the calibration in amplitude and phase of these massive MIMO systems, as the antenna elements are too densely packed to provide a separate calibration branch for measuring them independently. Over-the-air (OTA) calibration methods are viable solutions to this problem. In contrast to previous works, the here presented OTA calibration method is investigated and optimized for subarray-based hybrid beamforming (SBHB) systems. SBHB systems represent an efficient architectural solution to realize massive MIMO systems. Moreover, based on OTA scattering parameter measurements, the ambiguities of the phase shifters are exploited and two criteria to optimize the beam pattern are formulated. Finally, the optimization criteria are examined in measurements utilizing a novel SBHB receiver system operating at 27.8 GHz

Four-element phased-array beamformers and a self-interference canceling full-duplex transciver in 130-nm SiGe for 5G applications at 26 GHz

This thesis is on the design of radio-frequency (RF) integrated front-end circuits for next generation 5G communication systems. The demand for higher data rates and lower latency in 5G networks can only be met using several new technologies including, but not limited to, mm-waves, massive-MIMO, and full-duplex. Use of mm-waves provides more bandwidth that is necessary for high data rates at the cost of increased attenuation in air. Massive-MIMO arrays are required to compensate for this increased path loss by providing beam steering and array gain. Furthermore, full duplex operation is desirable for improved spectrum efficiency and reduced latency. The difficulty of full duplex operation is the self-interference (SI) between transmit (TX) and receive (RX) paths. Conventional methods to suppress this interference utilize either bulky circulators, isolators, couplers or two separate antennas. These methods are not suitable for fully-integrated full-duplex massive-MIMO arrays. This thesis presents circuit and system level solutions to the issues summarized above, in the form of SiGe integrated circuits for 5G applications at 26 GHz. First, a full-duplex RF front-end architecture is proposed that is scalable to massive-MIMO arrays. It is based on blind, RF self-interference cancellation that is applicable to single/shared antenna front-ends. A high resolution RF vector modulator is developed, which is the key building block that empowers the full-duplex frontend architecture by achieving better than state-of-the-art 10-b monotonic phase control. This vector modulator is combined with linear-in-dB variable gain amplifiers and attenuators to realize a precision self-interference cancellation circuitry. Further, adaptive control of this SI canceler is made possible by including an on-chip low-power IQ downconverter. It correlates copies of transmitted and received signals and provides baseband/dc outputs that can be used to adaptively control the SI canceler. The solution comes at the cost of minimal additional circuitry, yet significantly eases linearity requirements of critical receiver blocks at RF/IF such as mixers and ADCs. Second, to complement the proposed full-duplex front-end architecture and to provide a more complete solution, high-performance beamformer ICs with 5-/6- b phase and 3-/4-b amplitude control capabilities are designed. Single-channel, separate transmitter and receiver beamformers are implemented targeting massive- MIMO mode of operation, and their four-channel versions are developed for phasedarray communication systems. Better than state-of-the-art noise performance is obtained in the RX beamformer channel, with a full-channel noise figure of 3.3 d

Wideband Circuits and Antenna Designs for mm-Wave/5G Phased Arrays

The objective of this work is to present the performance and feasibility of wideband circuits and antennas for future mm-Wave phased array systems. Chapter 1 introduces the motivation of this research, first explaining the desire to operate at higher frequency regimes. Then focus is directed on the rich application spaces at mm-Wave frequencies and the corresponding need for wideband, compact, and fully integrated system-on-chip (SoC) solutions. A brief study of advanced node commercial silicon processes is also examined to demonstrate the increasing feasibility of implementing the aforementioned SoC solutions on silicon. Chapter 2 presents a design methodology of a novel ultra-compact, low-loss, and wideband mm-Wave Wilkinson Power Divider (WPD). Careful study and analysis reveal optimal and necessary design parameters and equations in terms of the coupling and mutual inductances within the structure, yielding a device that is competitive with existing literature. Chapter 3 first introduces the operation principle of spiral antennas (SA). The unique properties of SAs that make them great candidates for use in future mm-Wave phased arrays are explored. The rest of this chapter discusses the design, analysis, and results of an octagonal 4-arm Archimedean SA. Lastly, Chapter 4 provides closing remarks and discusses potential future work.M.S