Offset Frequency Synthesizer for Ultra-Low Phase Noise
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Solution Overview
Problem
Existing frequency synthesizers face limitations due to high phase noise and spurious outputs, particularly when using high values of N, which affects the performance of electronic systems requiring low phase noise and high frequency signals.
Innovation Solution
The system employs an offset signal generator to produce multiple frequency products, a selector to choose a specific frequency band, and a mixer to combine signals, along with a difference detector to adjust the oscillator, thereby reducing phase noise and spurious outputs by limiting the value of N to 3 or less, and using components like dielectric resonator oscillators and band-pass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high values of N are used in frequency synthesizers, then frequency multiplication is achieved, but phase noise and spurious outputs increase
Solution Approach 1:
The frequency multiplication process is segmented into multiple stages with intermediate filtering. Instead of using a single high-N multiplier, the system uses multiple lower-N multiplication stages (e.g., N=2, N=3) separated by band-pass filters that remove spurious outputs at each stage, preventing their accumulation and reducing overall phase noise.
Solution Approach 2:
Band-pass filters are introduced as intermediary components between frequency multiplication stages. These filters act as mediators that selectively pass the desired frequency while blocking spurious outputs, thereby decoupling the frequency multiplication function from the harmful spurious generation and allowing clean signal progression through the synthesizer.
2Measurement precision
If complex alignment and tuning mechanisms are added to achieve fine frequency adjustments, then frequency precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical alignment and tuning mechanisms with electronic frequency control methods. By using programmable frequency synthesizers and digital control of the N value and offset frequencies, fine frequency adjustments are achieved through electronic programming rather than mechanical alignment, dramatically reducing device complexity while maintaining or improving frequency precision.
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 approach results in a frequency synthesizer with significantly reduced phase noise and spurious outputs, enhancing the performance of systems like radar and communication systems by maintaining high frequency accuracy without excessive noise, and allowing for fine frequency adjustments without complex alignment or tuning.
Implementation Method 1
an offset signal generator for frequency multiplying the reference signal to generate an offset signal, the offset signal having a plurality of frequency products in a plurality of frequency bands
Implementation Method 2
a mixer for mixing the offset signal with the output signal to produce a combined signal
Implementation Method 3
a difference detector for detecting a difference between the reference signal and the combined signal and for providing a control signal to the oscillator based on the detected difference
Data Source
AI summary
An apparatus and method for providing an output signal. The apparatus comprises an input for receiving a reference signal, an oscillator for providing an output signal, and an offset signal generator for frequency multiplying the reference signal to generate an offset signal that has a plurality of frequency products in a plurality of frequency bands. The apparatus further includes a mixer for mixing the offset signal with the output signal to produce a combined signal, an offset frequency selector for controllably selecting a frequency band of the offset signal, and a difference detector for detecting a difference between the reference signal and the combined signal and for providing a control signal to the oscillator based on the detected difference.