CONTINUOUS FREQUENCY COVERAGE AND RANGE EXPANSION IN PLL-BASED FREQUENCY SYNTHESIZERS
Keywords:
phase-locked loop (PLL), frequency synthesizer, wideband frequency synthesis, continuous frequency coverage, frequency division and multiplication, phase noise, spectral purity.Abstract
This paper analyzes methods for expanding the synthesized frequency range in phase-locked loop (PLL)-based frequency synthesizers with an emphasis on achieving continuous frequency coverage. The study examines 3 based on integer frequency relationships using frequency division and multiplication within a single PLL loop. A condition for continuous frequency coverage is formulated, ensuring overlap between adjacent synthesis configurations and preventing frequency gaps. The influence of frequency division coefficients, harmonic selection, and conversion stages on spectral purity and phase noise performance is discussed. A circuit architecture employing a low-noise high-frequency reference oscillator and commercially available PLL integrated circuits is considered. The analysis demonstrates that wideband frequency synthesis with high spectral quality can be achieved while limiting the number of frequency conversions and maintaining structural simplicity. The obtained results provide practical guidelines for the design and optimization of wideband frequency synthesizers requiring stable operation and continuous tuning.
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