Frequency Synthesizer Mixer Feedback for Low Phase Noise
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Solution Overview
Problem
Frequency synthesizers in signal generation equipment suffer from high phase noise and limited step size accuracy due to the use of dividers in the feedback path, which restricts the sensitivity and precision of testing systems.
Innovation Solution
The implementation of frequency converters, such as mixers, in the feedback path, along with a feedforward path and phase-locked loops, eliminates dividers and reduces phase noise, allowing for fine frequency tuning and small step sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If dividers are used in the feedback path of a frequency synthesizer, then the circuit structure is simpler, but the phase noise increases and step size accuracy deteriorates
Solution Approach 1:
The patent removes dividers from the feedback path and replaces them with frequency converters (mixers). This extraction of the divider component eliminates the source of phase noise while maintaining the frequency synthesis function through alternative means (mixers with locally generated frequencies).
Solution Approach 2:
The patent substitutes the mechanical/divider-based frequency division approach with an electronic frequency conversion approach using mixers. This replacement transitions from a discrete component-based system to a continuous electronic signal processing system, improving phase noise performance and step size accuracy.
2Ease of manufacture
If dividers are used in the feedback path, then the device is easier to manufacture, but phase noise is high
Solution Approach 1:
The divider component is extracted and removed from the feedback path. This eliminates the primary source of phase noise generation while the overall device remains manufacturable through the use of standard mixer components and frequency synthesis techniques.
3Measurement precision
If the step size is reduced for greater testing accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent replaces the traditional discrete step-tuning mechanism with a continuous electronic frequency control system using mixers and locally generated frequencies. This allows for arbitrarily small step sizes through electronic programming without increasing physical device complexity.
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 configuration provides frequency synthesizers with reduced phase noise and improved step size accuracy, enhancing the sensitivity and precision of testing systems.
Implementation Method 1
In each element, a mixer can multiply an input signal by a frequency-divided version of the input signal
Data Source
AI summary
Frequency synthesizers having reduced phase noise and a small step size. One example can provide frequency synthesizers having low phase noise by eliminating dividers in a feedback path and instead employing frequency converters, such as mixers. Step size can be further reduced by providing frequency converters in a reference signal feedforward path. Acquisition time can be decreased by employing a fast-acquisition phase-locked loop that is switched out after acquisition in favor of a low phase-noise phase-locked loop. Another example can reduce phase noise by employing a YIG oscillator. To improve acquisition time, a first, faster phase-locked loop can be used to lock to a signal before switching to a second, slower phase-locked loop that includes the YIG oscillator. Another example can provide low noise by including phase-locked loops that operate in a frequency range having low thermal noise while a frequency of an output signal varies over a wide range.