Performance Analysis of Reference Oscillators and Frequency Synthesizers for use in High-Fidelity Satellite Navigation Receivers

The purpose of this study is to characterize and minimize the noise processes present in reference oscillators (RO) and frequency synthesizers for their use in high-fidelity satellite navigation and timing (satnav) receivers. Instrumentation grade satnav receivers for purposes including signal monitoring and ChipShape analysis [1] require long pre-detection integration times and narrow tracking loop bandwidths. Excessive phase noise contributed from the RO and frequency synthesizer come in through the satnav signals and degrade the Signal-to-Noise-Ratio (SNR) and impacts the code and carrier tracking loops of the receiver. Spurious spectral outputs, also known as spurs, generated by the frequency synthesizer can mix-in unwanted out-of-band signals into the intermediate frequency (IF) pass band of a receiver. Interfering signals that are either in the passband or stopband are phase-modulated by the frequency synthesizer’s phase noise through reciprocal mixing, further degrading the SNR. Thus, the design engineer must take these factors into consideration when selecting a frequency synthesizer for their RF front-end. Several commercial single-chip charge pump phase locked loops (PLLs) with integrated voltage-controlled oscillators (VCOs) where evaluated for their suitability for instrumentation-grade satnav receivers. This paper reports the findings of this study. The results contained in this paper can aid designers in selecting and configuring frequency synthesizers for use in high-fidelity satellite navigation and timing (satnav) receivers.