Digitally Controlled Oscillator Capacitance Grouping for Fine Tuning
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Solution Overview
Problem
Digitally controlled oscillators face challenges in achieving fine resolution and wide tuning ranges due to capacitor mismatches and increased design complexity, which degrade phase error and RF spectrum performance, and reduce the oscillating frequency's tuning range.
Innovation Solution
The implementation of a digitally controlled oscillator with a pair of cross-coupled transistors, a switched capacitor array, and a plurality of frequency tracking units that can selectively provide different capacitances to achieve precise frequency tuning, using passive metal capacitors to minimize noise and parasitic capacitance, thereby enhancing tuning resolution and reducing design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of frequency tracking units are used to provide finer tuning resolutions and wider tuning ranges, then the tuning resolution and tuning range are improved, but the design complexity increases and capacitor mismatches degrade performance
Solution Approach 1:
The frequency tracking units are divided into multiple groups, where each group contains frequency tracking units with the same capacitance values. Within each group, units are further segmented into sub-groups based on control signal patterns. This segmentation allows the system to achieve fine tuning resolution without requiring every unit to have unique capacitance values, thereby reducing design complexity while maintaining precision.
2Measurement precision
If a large number of frequency tracking units are used to achieve finer tuning resolutions, then the tuning resolution is improved, but capacitor mismatches among the units degrade phase error and RF spectrum performance
Solution Approach 1:
Frequency tracking units within the same group are assigned identical capacitance values, creating local uniformity. This local quality approach ensures that units experiencing similar process variations and mismatches are treated equivalently, allowing error correlation to be managed systematically. The consistent capacitance values within groups reduce the impact of random mismatches while maintaining the ability to achieve fine tuning resolution through group-level control.
3Adaptability or versatility
If more frequency tracking units are added to widen the tuning range, then the tuning range is improved, but the parasitic capacitor increases and narrows the total tuning range
Solution Approach 1:
Multiple frequency tracking units with identical capacitance values are merged into groups that share common control signals and capacitance structures. This merging reduces the total number of independent capacitance elements required, thereby minimizing the cumulative parasitic capacitance. The grouped architecture achieves wide tuning range through coordinated control of groups rather than requiring each individual unit to operate independently, thus reducing parasitic effects while maintaining adaptability.
4Ease of operation
If frequency tracking units with finite tuning resolutions are used, then the DCO can operate, but extra quantization noise is introduced that degrades phase noise performance
Solution Approach 1:
The system employs a feedback mechanism where the actual output frequency is monitored and compared with the target frequency. Based on this feedback, the control signals to the frequency tracking units are dynamically adjusted to minimize frequency error. This closed-loop feedback compensates for quantization noise by continuously correcting the output frequency, allowing the DCO to operate with finite resolution units while maintaining low phase noise performance.
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
This configuration improves the tuning resolution and reduces the impact of capacitor mismatches, leading to better phase error and RF spectrum performance while maintaining a wider tuning range for the oscillating frequency.
Implementation Method 1
an amplifier with a negative resistance, having a first input terminal, a second input terminal and an output terminal for providing an output signal
Implementation Method 2
a switched capacitor array coupled to the pair of transistors, for tuning a frequency of the output signal
Implementation Method 3
a plurality of frequency tracking units coupled to the pair of transistors, for tuning the frequency of the output signal to a target frequency
Data Source
AI summary
A digitally controlled oscillator is provided. The digitally controlled oscillator includes a pair of transistors cross-coupled to each other, a switched capacitor array coupled to the pair of transistors and a plurality of frequency tracking units coupled to the pair of transistors. The pair of transistors provides an output signal. The switched capacitor array tunes a frequency of the output signal. The frequency tracking units tune the frequency of the output signal to a target frequency. At least one of the frequency tracking units is capable of selectively providing a first capacitance and a second capacitance. A tuning resolution of the frequency tracking unit is determined by a difference between the first and second capacitances.