Programmable RC Oscillator Using Switched Delay Networks
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Solution Overview
Problem
Conventional RC oscillators face challenges in programmability due to difficulties in fabricating variable resistors and capacitors, especially with floating nodes that swing in voltage, making it hard to achieve precise frequency control and practical programmability.
Innovation Solution
The design incorporates a first delay section with a variable RC network and a second delay section with a fixed RC network, using switched capacitors and a feedback loop to generate a programmable output frequency, allowing for on-the-fly frequency adjustment through control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable resistors or capacitors are used to change frequency, then frequency adjustability is improved, but manufacturing difficulty and noise increase
Solution Approach 1:
The oscillator frequency is divided into multiple discrete selectable values using separate RC networks (first, second, third, and fourth RC networks), each providing a specific frequency range. This segmentation allows precise frequency control through digital selection without requiring continuously variable components, resolving the manufacturing difficulty while maintaining frequency adjustability.
Solution Approach 2:
The patent implements dynamic frequency adjustment by using digital control signals to selectively enable different RC networks based on the desired frequency range. This dynamic switching mechanism allows the oscillator to adapt its frequency output in real-time without physical component changes, achieving both manufacturability and frequency versatility.
2Adaptability or versatility
If variable resistors or capacitors are used to change frequency, then frequency adjustability is improved, but noise performance deteriorates
Solution Approach 1:
By segmenting the frequency control into discrete RC networks rather than using a single variable capacitor, the patent eliminates the switching noise and contact noise associated with traditional variable capacitors. Each RC network uses fixed components with stable noise characteristics, maintaining low noise performance across all frequency ranges while achieving frequency adjustability.
3Reliability
If floating nodes with voltage swings are used, then oscillator operation is achieved, but programmability becomes difficult
Solution Approach 1:
The patent separates the floating oscillating nodes from the frequency selection mechanism by using multiple independent RC networks. Each network can be independently controlled by digital signals without being affected by the voltage swings at floating nodes, enabling reliable programmable frequency control while maintaining proper oscillator operation.
Solution Approach 2:
The patent introduces digital control signals as intermediaries between the frequency selection logic and the RC networks. These control signals mediate the selection of appropriate RC networks without requiring direct interaction with the floating voltage nodes, thus enabling programmability while preserving oscillator reliability.
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 approach enables precise control over the oscillator frequency, improving the utility of RC oscillators by allowing for programmable output frequencies while maintaining low noise performance and simplicity, overcoming the challenges of variable resistor and capacitor implementation.
Implementation Method 1
The delay stage 126 may comprise an RC network 204. The RC network 204 may include a resistor R and a capacitor C. The delay stage 126 may provide a delay t1 that is determined based on an RC time constant defined by the resistor R and the capacitor C.
Data Source
Figure 1A~1B
Figure 2
Figure 2A
AI summary
An oscillator circuit having a programmable output frequency may include a first delay section having a negative gain and a variable delay that is set by a control signal provided to the first delay section. A second delay section having a negative gain and a fixed delay may be connected in series with the first delay section. The oscillator circuit may include an output comprising the output of the second delay section having a frequency that is dependent on the delay of the first delay section and the delay of second delay section.