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

Radio Frequency and Millimeter Wave Circuit Component Design with SiGe BiCMOS Technology

The objective of this research is to study and leverage the unique properties and advantages of silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) integrated circuit technologies to better design radio frequency (RF) and millimeter wave (mm-wave) circuit components. With recent developments, the high yield and modest cost silicon-based semiconductor technologies have proven to be attractive and cost-effective alternatives to high-performance III-V technology platforms. Between SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology and advanced RF complementary metal-oxide-semiconductor (CMOS) technology, the fundamental device-level differences between SiGe HBTs and field-effect transistors (FETs) grant SiGe HBTs clear advantages as well as unique design concerns. The work presented in this dissertation identifies several advantages and challenges on design using SiGe HBTs and provides design examples that exploit and address these unique benefits and problems with circuit component designs using SiGe HBTs.Ph.D

KEY FRONT-END CIRCUITS IN MILLIMETER-WAVE SILICON-BASED WIRELESS TRANSMITTERS FOR PHASED-ARRAY APPLICATIONS

Millimeter-wave (mm-Wave) phased arrays have been widely used in numerous wireless systems to perform beam forming and spatial filtering that can enhance the equivalent isotropically radiated power (EIRP) for the transmitter (TX). Regarding the existing phased-array architectures, an mm-Wave transmitter includes several building blocks to perform the desired delivered power and phases for wireless communication. Power amplifier (PA) is the most important building block. It needs to offer several advantages, e.g., high efficiency, broadband operation and high linearity. With the recent escalation of interest in 5G wireless communication technologies, mm-Wave transceivers at the 5G frequency bands (e.g., 28 GHz, 37 GHz, 39 GHz, and 60 GHz) have become an important topic in both academia and industry. Thus, PA design is a critical obstacle due to the challenges associated with implementing wideband, highly efficient and highly linear PAs at mm-Wave frequencies. In this dissertation, we present several PA design innovations to address the aforementioned challenges. Additionally, phase shifter (PS) also plays a key role in a phased-array system, since it governs the beam forming quality and steering capabilities. A high-performance phase shifter should achieve a low insertion loss, a wide phase shifting range, dense phase shift angles, and good input/output matching.Ph.D