Programmable Varactor VCO Gain for Noise-Stable Frequency Control
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Solution Overview
Problem
Conventional voltage-controlled oscillators (VCOs) with high programmable gain are sensitive to circuit noise, leading to larger errors in oscillation frequency due to their increased responsiveness.
Innovation Solution
A programmable variable capacitor is implemented, comprising a fixed varactor controlled by a control voltage and contingent varactors conditionally controlled by logical signals, using multiplexers to select between DC voltages, allowing for variable capacitance and reduced noise immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the VCO gain is increased to improve responsiveness, then the phase lock loop response speed is improved, but the sensitivity to circuit noise increases leading to larger frequency errors
Solution Approach 1:
The variable capacitor is segmented into multiple sub-capacitors (first variable capacitor, second variable capacitor, third variable capacitor) that can be independently controlled. Each sub-capacitor is connected to separate control voltage inputs, allowing the total capacitance to be adjusted in discrete steps. This segmentation enables programmable gain control where the VCO can operate at different gain levels, reducing noise sensitivity at high gain settings while maintaining fast response when needed.
Solution Approach 2:
The invention changes the capacitance parameter of the resonant tank by introducing multiple controllable variable capacitors. By varying the capacitance values of these sub-capacitors based on control signals, the overall VCO gain can be programmed to different levels. This parameter change allows the system to switch between high responsiveness and low noise sensitivity modes, resolving the contradiction between speed and precision.
2Loss of time
If a high VCO gain is used to achieve faster phase lock loop response, then the response time is reduced, but the sensitivity to circuit noise increases
Solution Approach 1:
The invention makes the VCO gain dynamic by introducing programmable control over the capacitance elements. The variable capacitors can be adjusted in real-time based on operating conditions, allowing the system to dynamically switch between high-gain mode (for fast acquisition) and low-gain mode (for steady-state noise rejection). This dynamic adaptability resolves the contradiction between response time and noise sensitivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a VCO with a programmable gain that reduces sensitivity to circuit noise by balancing capacitance changes, maintaining stability and accuracy in oscillation frequency across varying control voltages.
Implementation Method 1
a variable capacitor comprising two varactors 113 and 114 controlled by VC
Data Source
AI summary
A programmable variable capacitor includes a fixed varactor controlled by a control voltage connected in a first polarity and a plurality of contingent varactors conditionally controlled by the control voltage in accordance with a plurality of logical signals, respectively, each of said plurality of contingent varactors having: a first varactor controlled by a first voltage connected in the first polarity, a second varactor controlled by a second voltage connected in a second polarity, a first multiplexer configured to output the first voltage by selecting between a first DC (direct-current) voltage and the control voltage in accordance with a respective logical signal among said plurality of logical signals, and a second multiplexer configured to output the second voltage by selecting between a second DC voltage and a medium DC voltage in accordance with the respective logical signal.