Abstract
Microwave signals with low phase and timing noise are critical for multiple fields of wide scientific, technological, and societal impact. This includes the areas of precision timekeeping, navigation, communications and radar-based sensing. Conventional high-performance electrical oscillators rely on a resonator to achieve low-phase noise performance; however, the quality factor of the resonator limits the purity of the signal generated by these oscillators.
On the other hand, photonic-based microwave generation approaches such as Optical Frequency Division (OFD) have drawn significant attention due to their unique ability to overcome some of the conventional oscillator’s limitations and outperform their traditional counterparts, state-of-the-art electronic oscillators by several orders of magnitude. However, this superior performance comes with restricted tunability that is often in the range of a few percent. As a result, frequency synthesis faces a trade-off between achieving low noise, broad, and fast tunability.
To leverage the benefits of low-phase noise photonic techniques while maintaining the low additive noise characteristics of the generated microwave signal, a low phase noise electronic frequency synthesizer driven by a photonic oscillator is essential, which ensures the extension of the frequency range of the generated microwave signal to several frequency bands.
A conventional electronic frequency synthesizer is based on the Phase Lock Loop (PLLs) technique, which face limitations on bandwidth and frequency tuning resolution. On the other hand, Direct Digital Synthesizers (DDSs) are widely used for their tuning range and phase noise performance, yet they suffer from the drawback of limited bandwidth.
Therefore, this dissertation aims to explore the challenges associated with low-phase-noise microwave signal generation and introduce multiple effective techniques to achieve ultra-low phase noise performance across a wide frequency range.
High-performance radar and communication systems rely highly on the phase noise performance of the microwave signal, and the additive noise of the amplifier limits the purity of the signal generated by electronic oscillators. Moreover, power amplifiers are essential components in the transmitter chain of a broad range of systems with applications covering wireless and mobile communication, and their phase noise can affect the error vector magnitude (EVM) of the signal and the bit error rate (BER) of a communication system. To achieve low additive phase noise and high efficiency across a wide frequency range, ultra-low-phase-noise and efficient amplifiers are essential. Consequently, this dissertation explores trade offs associated with low-phase-noise amplification and provides a detailed discussion of effective approaches to minimizing the phase noise in electrical amplifiers.
