Digitally Controlled Oscillator Frequency Ramping to Reduce Glitches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digitally controlled oscillators (DCOs) in communication systems face disruptions and audible noise due to discrete frequency adjustments, causing glitches in signal processing, particularly in FM demodulation, leading to undesirable tones and clicks.
Innovation Solution
A method and circuit that smoothly transition between frequencies by successively increasing time intervals during a transition period, using a digitally controlled oscillator and a transition controller to generate and activate/deactivate frequencies, with techniques such as linear ramps and pulse width modulation to minimize disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If discrete frequency steps are used to adjust the DCO frequency, then the frequency adjustment capability is achieved, but glitches and audible noise are generated in the signal processing
Solution Approach 1:
The frequency transition is segmented into multiple intermediate steps rather than a single discrete jump. The transition controller divides the frequency change into a sequence of smaller frequency adjustments, allowing the DCO to progress through intermediate frequencies. This segmentation reduces the magnitude of each individual frequency step, thereby minimizing glitches and audible noise while maintaining the overall frequency adjustment capability.
2Device complexity
If minimum capacitor values are used for frequency adjustment, then the device complexity is reduced, but the minimum frequency step size is limited causing disruptions
Solution Approach 1:
The frequency adjustment process is made dynamic by implementing a time-varying transition approach. The transition controller dynamically adjusts the frequency over time using a ramp function, where the frequency changes continuously rather than in fixed discrete steps. This dynamic approach allows the system to use minimum capacitor values for simplicity while achieving fine frequency resolution through temporal modulation, thereby resolving the contradiction between device complexity and frequency precision.
3Measurement precision
If frequency is recalibrated periodically, then the frequency accuracy is maintained, but undesirable audible tones are created
Solution Approach 1:
The system uses periodic frequency calibration but implements it through a smooth ramp-based transition rather than abrupt frequency changes. The transition controller applies a periodic calibration routine where the frequency is adjusted in a controlled ramp manner, maintaining frequency accuracy while avoiding the sudden frequency jumps that cause audible tones. The periodic action is preserved for accuracy maintenance, but the manner of execution is modified to eliminate harmful audible effects.
Data Source
AI summary
In one embodiment the present invention includes a method of generating an oscillating signal at different frequencies. The method comprises configuring a digitally controlled oscillator (DCO). The DCO is configured to generate the oscillating signal at a first frequency, and the DCO is configured to generate the oscillating signal at a second frequency. Additionally, the DCO is configured to transition from the first frequency to the second frequency during a transition time period. During the transition time period, the DCO activates the second frequency and deactivates the first frequency during a plurality of time intervals. The time intervals for activating the second frequency and deactivating the first frequency successively increase from the beginning of the transition time period to the end of the transition time period.