Digitally Controlled Oscillator Frequency Ramping for Quiet Recalibration
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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 transition controller to activate and deactivate frequencies, with techniques such as linear ramps or pulse width modulation, to generate a bit stream configuring the DCO for smooth frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If discrete frequency steps are used to adjust DCO frequency, then frequency adjustment capability is improved, but signal processing disruptions and audible noise increase
Solution Approach 1:
The frequency transition is segmented into multiple discrete steps rather than a single abrupt change. The transition controller divides the frequency adjustment into a sequence of intermediate frequency values, where each step is smaller and causes less disruption. This segmentation of the transition process reduces the harmful effects while maintaining frequency adjustment capability.
Solution Approach 2:
The frequency transition is implemented as a periodic sequence of frequency changes over time. The transition controller applies frequency adjustments in repeated small increments rather than a single large step, allowing the system to gradually adapt to the new frequency. This periodic action reduces audible noise by distributing the frequency change over multiple time periods.
2Device complexity
If minimum capacitor values are switched internally in DCO, then frequency step resolution is limited, but device complexity is reduced
Solution Approach 1:
The transition controller acts as an intermediary between the user's frequency adjustment request and the DCO's internal capacitor switching mechanism. It translates a single large frequency step into multiple smaller intermediate steps, effectively mediating between the limited resolution of the internal capacitors and the desired frequency precision. This intermediary layer improves frequency step resolution without modifying the underlying capacitor switching hardware.
Solution Approach 2:
The solution adds a temporal dimension to frequency adjustment by introducing time as a factor in the transition process. Instead of changing frequency instantaneously, the system spreads the adjustment over multiple time intervals with varying duration. This temporal dimensionality allows the system to achieve finer effective resolution by controlling the timing and duration of each frequency step.
3Measurement precision
If frequency is recalibrated periodically, then frequency accuracy is maintained, but undesirable audible tones are generated
Solution Approach 1:
The recalibration process is made dynamic by continuously monitoring frequency drift and triggering transitions only when necessary, rather than following a fixed periodic schedule. The transition controller adapts the timing and characteristics of frequency adjustments based on actual system conditions, maintaining frequency accuracy while minimizing audible tones by performing transitions only when drift exceeds a threshold.
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.