Digital Controlled Oscillator Capacitor Arrays for Linear Wide-Range Tuning
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Solution Overview
Problem
Conventional digital controlled oscillators face challenges in achieving wide-range frequency modulation with minimal frequency change and reduced quantization noise, leading to increased area occupation and parasitic capacitance, which affects the linearity and variability of oscillation frequencies.
Innovation Solution
The implementation of a digital controlled oscillator with two or more capacitor arrays, where the capacitance change in one array is an integral multiple of the other, allowing for constant capacitance change steps and reduced area occupation, enabling linear frequency variation over a wide range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of varactors in the capacitor array is increased to achieve wide-range linear frequency modulation, then the frequency modulation range is improved, but the area occupied by the variable capacitance section increases
Solution Approach 1:
The capacitor array is divided into multiple groups, where each group contains a subset of varactors. By selectively activating different groups based on the modulation range requirement, the system achieves wide-range frequency modulation without requiring all varactors to be present simultaneously in the circuit, thereby reducing the occupied area.
Solution Approach 2:
Multiple capacitor arrays with different capacitance values are nested within the variable capacitance section. Each array contributes to a specific portion of the frequency range, and they are combined to achieve the overall wide-range linear frequency modulation. This nested structure allows compact integration of multiple functional units.
2Measurement precision
If the number of control lines is increased to control individual varactors, then the frequency control precision is improved, but the area occupied by control lines and parasitic capacitance increases
Solution Approach 1:
Control lines are segmented and shared among multiple varactors within the same group. Instead of providing dedicated control lines to each varactor, the system uses a smaller number of control lines that can selectively activate or deactivate entire groups of varactors. This segmentation approach maintains frequency control precision while significantly reducing the number of control lines required.
Solution Approach 2:
Each control line is designed to control multiple varactors simultaneously, making the control line multi-functional. A single control line can activate different groups of varactors at different times or in different combinations, thereby reducing the total number of control lines needed while maintaining the ability to achieve precise frequency control through digital modulation codes.
3Adaptability or versatility
If the number of varactors is increased to secure wide linear frequency change range, then the frequency modulation capability is improved, but the parasitic capacitance increases
Solution Approach 1:
The varactors are organized into multiple groups that are activated selectively based on the required frequency modulation range. By activating only the necessary groups for the current operating condition, the system achieves wide linear frequency change capability while minimizing the total number of simultaneously active varactors, thereby reducing parasitic capacitance.
Solution Approach 2:
The system dynamically adjusts which groups of varactors are activated based on the digital modulation code and the desired frequency range. This dynamic activation strategy ensures that the minimum necessary capacitance is used to achieve the target frequency, minimizing parasitic effects while maintaining wide frequency tuning capability.
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 allows for a digital controlled oscillator that achieves linear frequency change over a wide range with reduced area occupation and parasitic capacitance, enhancing the performance and efficiency of frequency synthesizers in radio communication systems.
Implementation Method 1
The variable capacitance section 202 has capacitor arrays 203 to 205 each composed of a plurality of varactors. The varactors are variable capacitors whose capacitance value changes between a low capacitive state and a high capacitive state larger in capacitance value than the low capacitive state.
Implementation Method 2
The inductor 201 and the variable capacitance section 202 constitute an LC tank circuit, which outputs a signal having a frequency corresponding to the inductance of the inductor 201 and the capacitance of the variable capacitance section 202.
Data Source
AI summary
The digital controlled oscillator includes a variable capacitance section having a first capacitor array of a plurality of first variable capacitors and a second capacitor array of a plurality of second variable capacitors, and generates a signal having an oscillation frequency corresponding to the capacitance value of the variable capacitance section. The first capacitance change amount in the individual first variable capacitors is a value obtained by multiplying the second capacitance change amount in the individual second variable capacitors by an integer equal to or more than 2, and the number of second variable capacitors is equal to or more than a value obtained by subtracting 1 from the integer equal to or more than 2.