Digitally Controlled Oscillator Capacitance Array With Finer Frequency Steps
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Solution Overview
Problem
Increasing the number of control bits and variable capacitance elements in digitally controlled oscillators to widen the oscillation frequency range results in increased occupation area and parasitic capacitance of control lines, making it difficult to maintain a small and constant frequency change with respect to a unit control signal.
Innovation Solution
The configuration of a digitally controlled oscillator with a second element group of 32x32 variable capacitance elements, where each element is an NMOS transistor with switching elements connected in series to control lines, allowing for discrete capacitance changes using control signals, reducing the number of control lines and parasitic capacitance, and enabling finer frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of control bits and variable capacitance elements is increased to widen the oscillation frequency range, then the frequency tuning range is improved, but the occupation area and parasitic capacitance of control lines increase
Solution Approach 1:
The patent merges multiple control lines into a single control line by encoding multiple control signals into different frequency components of a single clock signal. Instead of having separate control lines for each variable capacitance element, the invention combines all control signals into one line that carries multiplexed control information, thereby reducing the occupation area of control lines while maintaining the ability to control a large number of capacitance elements.
Solution Approach 2:
The single control line serves multiple functions by carrying different control signals at different time intervals or frequency components. The control line is universally used to control all variable capacitance elements in the array, rather than having dedicated control lines for each element. This multi-functional approach allows the system to widen the oscillation frequency range without proportionally increasing the control line area.
2Adaptability or versatility
If the number of control bits and variable capacitance elements is increased to widen the oscillation frequency range, then the frequency tuning range is improved, but the parasitic capacitance of control lines increases
Solution Approach 1:
The patent combines multiple control signals into a single control line, thereby reducing the total parasitic capacitance. Instead of having N separate control lines each with their own parasitic capacitance, the invention uses one control line whose total parasitic capacitance is significantly less than the sum of N separate lines. This merging approach directly addresses the harmful effect of parasitic capacitance while enabling frequency range expansion.
Solution Approach 2:
The control signal processing circuit acts as an intermediary that decodes the single control line signal into multiple control outputs for different variable capacitance elements. This intermediary approach allows the system to control numerous elements without directly connecting each to a separate control line, thereby minimizing parasitic capacitance effects while maintaining full control capability across the extended frequency range.
3Adaptability or versatility
If the number of variable capacitance elements is increased to widen the oscillation frequency range, then the frequency tuning capability is improved, but the frequency change with respect to unit control signal becomes difficult to keep small and constant
Solution Approach 1:
The patent segments the variable capacitance elements into multiple groups or banks, each controlled by specific control signals. By organizing the large number of capacitance elements into structured segments, the system can precisely control the capacitance contribution of each segment. This segmentation allows for fine-grained adjustment of the oscillation frequency, ensuring that each unit control signal produces a small and constant frequency change across the entire tuning range.
Solution Approach 2:
The control system dynamically adjusts the capacitance values of individual variable capacitance elements based on the desired frequency target. By using dynamic control signals that selectively activate or deactivate specific capacitance elements, the system maintains uniform frequency steps across the entire oscillation frequency range. This dynamic adjustment capability ensures that frequency change with respect to unit control signal remains small and constant even as the total number of controllable elements increases.
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 stable and precise oscillation frequency control with reduced occupation area and parasitic capacitance, enabling the digitally controlled oscillator to efficiently cover a wide frequency range while minimizing the impact of increased control bits and capacitance elements.
Implementation Method 1
a second element group including 32×32 variable capacitance elements C(1,1) to C(32,32), where capacitance control terminals of the variable capacitance elements C(1,1) to C(32,32) are connected to control lines Ltn(1) to Ltn(32), respectively
Data Source
AI summary
A semiconductor device according to the present embodiment includes a plurality of switching elements and a plurality of variable capacitance elements. The switching elements are switching elements connected in series between a first control terminal and a second control terminal and plural types of capacitance control signals can be supplied to the first control terminal and the second control terminal. The variable capacitance elements have capacitance control terminals connected to corresponding one ends of the switching elements, respectively.