Vector Network Analyzer LO Circuit for Phase Noise Cancellation

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Solution Overview

Problem

Current vector network analyzers (VNAs) and other electronic components in RF applications suffer from significant phase noise, which is not adequately minimized by existing technologies, affecting performance in communication, radar, and imaging applications.

Innovation Solution

The implementation of an electronic arrangement using a single RF signal source with an IQ modulator and frequency mixer to generate a modulated signal that cancels phase noise by subtracting the noise component through frequency offset, combined with low-pass filtering to remove high-frequency components, and optionally utilizing a second RF signal source for further noise cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a signal generator is used in a VNA, then signal generation capability is provided, but phase noise is introduced

Engineering Contradiction:

Improvephase noiseVSAvoidphase noise

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies phase noise cancellation by mixing the stimulus signal with a modulated version of itself. The modulation process intentionally introduces a known frequency offset, and the subsequent mixing operation exploits this offset to cancel the phase noise through coherent subtraction. This converts the harmful phase noise into a cancelable artifact by using the signal's own structure against it.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces a modulator as an intermediary component that creates a frequency-offset version of the stimulus signal. This modulated signal serves as a mediator in the mixing process, enabling the phase noise cancellation by providing a reference that is identical in all respects except for the intentional frequency offset, which facilitates the noise cancellation mathematically.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If phase noise cancellation is implemented using signal modulation and mixing, then phase noise is reduced, but device complexity increases

Engineering Contradiction:

Improvephase noise reductionVSAvoidelectronic circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The modulator in the patent serves multiple functions: it frequency-shifts the stimulus signal to create the modulated version, it embeds the phase noise information in a cancelable form, and it provides the frequency offset necessary for the subsequent mixing operation. By making the modulator multi-functional, the patent reduces the need for separate dedicated components for each function, thereby managing complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The phase noise cancellation system uses the stimulus signal itself as the reference for cancellation. The stimulus signal is modulated to create a version that contains the same phase noise, and this self-referenced approach eliminates the need for an external ultra-low-noise reference signal source. The system serves its own phase noise cancellation needs using its own generated signals.

Inventive Principle:

Principle #25Self-service

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 effectively reduces phase noise in signals, enhancing the accuracy and reliability of measurements in VNAs and other RF applications by isolating the local oscillator frequency from phase noise, thereby improving signal quality.

Implementation Method 1

a first mixer defining first and second inputs and an output, the output of the first signal source being coupled to the first input of the first mixer, the output of the modulator coupled to the second input of the first mixer, the first mixer arranged to generate a mixed signal that includes a difference of the stimulus signal and the modulated signal

Methodology Applied

Scientific EffectFrequency mixing: Heterodyne

Implementation Method 2

combined with low-pass filtering to remove high-frequency components

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS10571500B2Electronic arrangement and vector network analyzer characterized by reduced phase noise

Publication Date: 2020.02.25 MINUS174

AI summary

An electronic arrangement and method for providing a signal characterized by reduced phase noise having a signal source for providing a stimulus signal, a modulator coupled to the signal source for generating a modulated signal as function of the stimulus signal and a local oscillator signal, and a mixer combining the stimulus and modulated signals to generate a mixed signal that includes a component characterized by a mathematical difference of the stimulus signal and the modulated signal. The modulated signal is substantially identical to the stimulus signal and offset by a frequency of the local oscillator signal, so that the difference component of the mixed signal results in a local oscillator signal wherein the stimulus signal phase noise generated by the signal source has been mathematically cancelled.