Sudipta Saha

Date of Award

4-28-2022

Document Type

Dissertation - SCU Access Only

Publisher

Santa Clara : Santa Clara University, 2022.

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

First Advisor

Shoba Krishnan

Second Advisor

Allen A. Sweet

Abstract

5G is now pushing the state-of-the-art in virtually every aspect of high-speed mobile networks, multimedia, Internet of Things (IoT) and satellite internet connections. There is a critical need for the design of faster and more spectrum efficient 5G communication systems. To meet the most ambitious 5G goals, including peak data rates of 10 Gbps, cell edge data rates of 100 Mbps and 1ms end-to-end latency, device performances from C-band (4 – 8 GHz) to mm-Wave frequency bands (> 20 GHz) are needed.

In 5G wireless communication, new challenges have arisen in terms of managing radio link system capacity including noise, interference, attenuation, mm-Wave penetration, antenna array architecture, security, coverage and scalability. Our work has focused on two main issues related to improved understanding of noise and extending system coverage while reducing unnecessary RF interference.

The first issue is related to radio link noise which in general has two broad sources: internal and external. Our work is focused on the internal noise source generated inside the local oscillator (LO), (i.e.; phase noise). The latest 5G telecommunications technologies demand that significant reductions be made in LO phase noise. To be successful, today’s designers need to achieve detailed physical insight into the root causes of LO phase noise in order to meet such stringent requirements. The second issue is related to system coverage and interference for multiple-input and multiple-output (MIMO) systems using phased array antenna. In a phased array antenna system, the phase shifter operating at mm-Wave frequency will be the key component for steering the beam. The main challenges for designing mm-Wave phase shifters are overcoming the problems related to die area, insertion loss and power consumption.

To tackle these two issues, this dissertation proposes a new approach to utilize the beneficial nature of injection locking for accurately predicting the phase noise of a free running LC oscillator and implementing a wide locking range injection locked LC oscillator-based phase shifter (ILPS).

First, a new theoretical framework for calculating the phase noise of CMOS LC voltage-controlled oscillators (VCO), which relies on easy to implement closed form solutions is provided. This circuit-based theory is built upon an understanding that phase noise is the direct result of an oscillator’s latent non-ideal nature and its own inevitable self-injected noise sources which accompany each component’s non-ideal nature. Second, the injection locking technique is used to design a new Complementary metal-oxide-semiconductor (CMOS) ILPS circuit. This new ILPS circuit version has a locking range wide enough to cover the entire Sub-6 GHz 5G bands without any discontinuities. Excellent tradeoff between locking range and phase noise performance has been achieved with low power and area efficient design. The ILPS circuit has been implemented in a 90nm RF CMOS process consuming 25mW of DC power with a 1.8V supply.

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