Vector-Based Frequency Synthesizer for Wideband Fine Tuning
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Solution Overview
Problem
Conventional frequency synthesizers face challenges in finely setting frequencies over a broad band with low noise, due to increased noise from high frequency division ratios and complex circuit constructions, and struggle with noise from simultaneous switching in digital/analog converters.
Innovation Solution
A novel frequency synthesizer architecture that includes a voltage-controlled oscillator, frequency division, analog/digital conversion, vector extraction, and feedback mechanisms to adjust frequencies finely with low noise, using orthogonal detection and integrating circuits to control the voltage-controlled oscillator, and reducing noise by optimizing switching in digital/analog converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency division ratio N is increased to set frequencies finely, then the frequency setting precision is improved, but the noise increases due to elongation of delay in the loop
Solution Approach 1:
The patent divides the frequency division into two stages: a first frequency divider with division ratio N1 and a second frequency divider with division ratio N2. This segmentation allows the system to achieve fine frequency setting (equivalent to N1×N2) while keeping each individual divider's ratio manageable, thus preventing excessive noise from loop delay elongation that would occur with a single high-ratio divider.
Solution Approach 2:
The patent introduces a novel frequency detection method using vector extraction and orthogonal detection in the frequency detection unit. Instead of relying solely on phase comparison in the traditional PLL domain, the system transforms the frequency detection problem into a different dimensional approach by detecting frequency through vector rotation speed, enabling fine frequency control without proportionally increasing the feedback loop delay.
2Measurement precision
If the frequency division ratio N is increased to set frequencies finely, then the frequency setting precision is improved, but the circuit complexity increases
Solution Approach 1:
The patent merges the frequency division function and frequency detection function into an integrated frequency synthesizer system. The first and second frequency dividers work together with the vector extraction unit and orthogonal detection unit to achieve fine frequency setting. This unified approach avoids the need for separate complex multistage synthesizer systems that would be required conventionally, thereby reducing overall circuit complexity while maintaining fine frequency control capability.
3Measurement precision
If multiple frequency synthesizers are combined to achieve fine frequency setting over broad band, then the frequency setting precision is improved, but the number of parts increases and noise increases
Solution Approach 1:
The patent creates a universal frequency synthesizer system that can achieve fine frequency setting over a broad frequency band through a single integrated design. The frequency synthesizer uses a voltage-controlled oscillator, first and second frequency dividers, vector extraction unit, orthogonal detection unit, and frequency detection unit working together. This multi-functional system eliminates the need for multiple separate frequency synthesizer modules, thereby reducing the number of parts while maintaining the capability for fine frequency adjustment across a wide range.
4Speed
If simultaneous switching of many switching elements in digital/analog converter is performed, then the frequency conversion speed is improved, but noise is generated
Solution Approach 1:
The patent employs a dithering technique that applies a small periodic signal to the digital-to-analog converter. This periodic action distributes the quantization error and switching noise over a wider frequency spectrum, reducing the impact of simultaneous switching noise while maintaining fast frequency conversion capability. The periodic dither signal effectively linearizes the converter operation and reduces distortion.
Data Source
AI summary
An object of the present invention provides a frequency synthesizer having a broad frequency entraining range which can finely set a frequency over a broad band by a novel principle.As a specific solving means, a sinusoidal signal of an output frequency of a voltage-controlled oscillator is subjected to orthogonal detection, a vector rotating at the differential frequency (speed) between the output frequency and the frequency of the frequency signal used for the detection is created, and the frequency of a vector when the output frequency of the voltage-controlled oscillator is equal to a set value is calculated in advance. The voltage signal corresponding to the difference between the frequency of the vector and the calculated frequency is fed back to the voltage-controlled oscillator when the voltage-controlled oscillator is driven, and PLL is formed so that the difference is equal to zero. Accordingly, the output frequency of the voltage-controlled oscillator is adjusted to the set frequency when PLL is locked. After the difference between both the frequencies is increased after PLL is locked, the set value is integrated by the integrating circuit portion and added to the control voltage.