Buffer-First VCO Architecture for Lower Phase Noise
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Solution Overview
Problem
Voltage controlled oscillators (VCOs) typically produce phase noise in their output signals, which is undesirable, and they can only be tuned over a narrow frequency range, leading to increased phase noise performance outside this range, limiting their application in broadband millimeter wave systems.
Innovation Solution
The VCOs are configured in a 'buffer-first' or 'multiplexer-less' configuration, where multiple VCO core circuits are synchronously coupled and buffered to reduce phase noise, and the outputs are summed to increase signal strength, eliminating the need for multiplexer networks that introduce additional noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple VCOs are combined to reduce phase noise, then phase noise is reduced, but buffer circuits or multiplexers re-introduce additional phase noise
Solution Approach 1:
Multiple VCO core circuits are synchronously tuned and their outputs are directly summed together to reduce phase noise through coherent addition, eliminating the need for separate buffer circuits for each VCO and avoiding the phase noise re-introduction problem
Solution Approach 2:
A single buffer circuit is designed to accept multiple VCO inputs simultaneously and provide a unified buffered output, serving multiple functions (buffering multiple sources, summing signals, driving transmission line) without requiring individual buffers for each VCO
2Adaptability or versatility
If multiple VCOs are used to cover broader frequency range, then frequency coverage is improved, but multiplexer networks introduce additional phase noise
Solution Approach 1:
Multiple VCO core circuits with different frequency ranges are synchronously tuned to the same target frequency, and their outputs are summed together, eliminating the need for multiplexer networks and the associated phase noise while achieving extended frequency coverage
Solution Approach 2:
The system dynamically adjusts the tuning voltage to synchronously tune multiple VCO cores to different target frequencies, enabling continuous frequency coverage across a broad range without requiring multiplexer switching
Data Source
AI summary
A voltage controlled oscillator (VCO) is disclosed to provide reduced phase noise at higher operating frequencies. A buffer-first VCO configured according to an embodiment includes multiple VCO core circuits configured to provide synchronously tuned oscillator signals. Each VCO core circuit is coupled to a summing node through a buffer circuit that generates uncorrelated phase noise such that the summing node provides a summation output of the oscillator signals with reduced phase noise. A multiplexer-less VCO configured according to an embodiment includes multiple buffer-first VCO circuits configured to provide oscillator signals covering a range of frequencies. Each buffer-first VCO circuit is controlled or selected by an enable signal. Buffer circuits are configured to select one of the buffer-first VCO circuits for coupling to a transmission line during a given time period based on the enable signal. The transmission line is terminated in a matched impedance at each end of the line.