Fractional-N Synthesizer Setting to Avoid Periodic Abnormal Noise
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Solution Overview
Problem
Fractional N frequency synthesizers experience periodic abnormal noise due to the relationship between accumulated values causing carryovers and fractional set values, leading to fluctuations in frequency division cycles and VCO control voltages, which affect the quality of sound or communication signals.
Innovation Solution
A fractional N frequency synthesizer with a calculator determining the remainder of division and repeatedly calculating quotients and remainders until zero, an abnormal noise determiner assessing noise thresholds, and a fractional setter adjusting the fractional set value to prevent periodic noise by incrementing or decrementing the value until acceptable noise levels are achieved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fractional set value is used in the ΔΣ modulator to enable decimal fraction frequency division setting, then frequency resolution is improved, but periodic abnormal noise occurs due to the relationship between accumulated values and fractional set values
Solution Approach 1:
The patent applies preliminary action by calculating the remainder of division between the accumulator maximum value and the fractional set value before operation, and determining in advance whether the fractional set value causes periodic abnormal noise. This allows the system to pre-select appropriate fractional set values that avoid noise problems while maintaining high frequency resolution.
Solution Approach 2:
The patent converts the potentially harmful relationship between accumulated values and fractional set values into a beneficial selection criterion. By analyzing the remainder of division and identifying patterns that cause periodic abnormal noise, the system transforms this mathematical relationship into a useful tool for selecting optimal fractional set values that eliminate noise while preserving frequency resolution.
2Adaptability or versatility
If the fractional set value is changed to achieve desired output frequency, then frequency setting flexibility is improved, but frequency fluctuations occur leading to signal quality degradation
Solution Approach 1:
The patent implements feedback by using the calculated remainder and quotient information to determine whether a selected fractional set value will cause periodic abnormal noise. This feedback mechanism allows the system to adjust the fractional set value selection to maintain both frequency setting flexibility and frequency stability, preventing signal quality degradation.
3Adaptability or versatility
If the operation cycle of the ΔΣ modulator is made equal to the division cycle of the multi-modulus frequency divider, then the fractional N frequency synthesizer can generate decimal fraction multiples, but periodic abnormal noise is generated due to carryover timing
Solution Approach 1:
The patent applies preliminary action by performing division calculations and remainder analysis before the ΔΣ modulator operation to identify fractional set values that would cause periodic abnormal noise. This allows the system to pre-determine safe operating parameters that maintain frequency generation versatility while avoiding noise-generating conditions.
Solution Approach 2:
The patent converts the timing relationship between carryover generation and frequency division into a beneficial selection criterion. By analyzing the mathematical relationship between the accumulator maximum value and fractional set value through division operations, the system identifies patterns that prevent periodic abnormal noise while maintaining the ability to generate decimal fraction multiples.
Data Source
AI summary
The calculator calculates the remainder of the division of which the dividend is the minimum accumulated value at which a carryover occurs in the ΔΣ modulator and the devisor is a fractional set value, and calculates the quotient and remainder of the division of which the dividend is the devisor of the previous division and the devisor is the remainder of the previous division until the remainder becomes zero. The abnormal noise determiner determines that the fractional set value causes periodic abnormal noise based on the quotients calculated by the calculator using the fractional set value. The fractional setter sets in the ΔΣ modulator the fractional set value changed to the extent that the output frequency of the VCO does not exceed a given value when the abnormal noise determiner determines that the changed fractional set value does not cause periodic abnormal noise.