VCO Nonlinearity Compensation Using Lookup-Table Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional VCO nonlinear compensation systems have complex circuit configurations and require timing adjustments for feedback, making them difficult to implement effectively.
Innovation Solution
A VCO nonlinear compensation system with a loop filter, voltage-controlled oscillator, feedback processing section, and nonlinearity-compensated section that uses a compensation table to adjust the frequency modulation signal, eliminating the need for timing adjustments and simplifying the circuit configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional direct synthesis modulator with PLL circuit is used to compensate VCO nonlinearity, then the oscillatory frequency response can be controlled, but the circuit becomes complicated and the number of components increases
Solution Approach 1:
The patent extracts the essential feedback function from the complex PLL circuit and implements it through a simplified configuration using a phase modulator and D/A converter. The core nonlinearity compensation mechanism is separated from the unnecessary complex components, achieving the same compensation effect with fewer elements.
Solution Approach 2:
The auxiliary terminal of the VCO, originally designed for frequency control, is made to serve dual purposes: both frequency control and phase adjustment for feedback. This multi-functionality eliminates the need for separate phase modulator components in some configurations, reducing overall circuit complexity.
2Manufacturing precision
If a D/A converter or down-converter is added to provide feedback for VCO nonlinearity compensation, then the nonlinearity can be compensated, but the timing adjustment becomes difficult
Solution Approach 1:
The patent introduces a phase modulator as an intermediary component that simplifies the feedback path. By using the phase modulator to condition the feedback signal before it reaches the D/A converter, the timing alignment becomes more straightforward and less sensitive to component variations.
Solution Approach 2:
The feedback signal is pre-processed by the phase modulator and filtered before being converted by the D/A converter. This preliminary action ensures that the signal is properly conditioned and timed before entering the critical conversion stage, making the overall system less sensitive to timing adjustments.
3Speed
If an auxiliary terminal is used for frequency control of VCO, then the oscillatory frequency can be adjusted, but a separate phase modulator is required
Solution Approach 1:
The auxiliary terminal of the VCO is designed to accept signals that can control both frequency and phase. By injecting the feedback signal through this existing terminal with appropriate conditioning, the system achieves phase control functionality without adding dedicated phase control hardware, reducing component count.
Solution Approach 2:
The patent merges the frequency control and phase control functions into a unified feedback mechanism. The same auxiliary terminal and signal path are used for both frequency stabilization and phase correction, eliminating redundant components and simplifying the overall architecture.
Data Source
AI summary
A nonlinearity-compensated section has a pre-set compensation table containing a measured value of a voltage vtc, outputted from a loop filter, which is changed accordingly with respect to a change in a voltage vtfc outputted from a frequency controlling section. The nonlinearity-compensated section sets, in the compensation table, the voltage vtfc of an oscillatory frequency oscillated by a VCO and the voltage vtc associated therewith as reference voltages, and creates a look-up table containing voltage differences obtained by subtracting the above-described reference voltages from the voltages vtfc and vtc, respectively. Thereafter, the nonlinearity-compensated section extracts a compensation value corresponding to the voltage vtc actually outputted from the loop filter by means of the look-up table, and adds the compensation value to an input modulated signal adjusted by a multiplier so as to be outputted.