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What is a Vector Network Analyzer?

August 28, 2023

What is a Vector Network Analyzer

For engineers that are outside of the RF and Microwave industry and work in industries like the healthcare and medical fields, food and beverage, agriculture, and beyond, a vector network analyzer might not be a familiar tool. The vector network analyzer working principle is that it produces an RF stimulus signal. The frequency can range from 9 kHz to 330 GHz which proceeds to and perhaps passes through a Device Under Test (DUT). The signal can be read by the ports available on a USB vector network analyzer, either as reflections from the DUT or transmission, signals that pass through. This is what makes a VNA different from other electronic test equipment.
 

Using VNAs in Unique Applications

As previously mentioned, the advent of USB vector network analyzers has spurred new technological advancements in a number of industries that didn’t previously utilize VNAs. The small, portable form factor of the USB version of VNAs allows them to be embedded in test systems used in many environments. A VNA well-suited for this is the R140B, 1-Port VNA. NASA has used a 1-port VNA to measure weightless liquid oxygen in a space vehicle tank which was previously impossible with benchtop VNAs. This article expands further upon the custom solutions provided by embeddable vector network analyzers.
 
 

Using a VNA as Alternative Test Equipment

For small labs or groups with a need to be economical about their test equipment, they may need to consider instruments with multiple uses. We have been asked, ‘Can I use a VNA as a spectrum analyzer’ or ‘Can I use a VNA as a signal generator’. The answer to both questions is technically yes, but there is a caveat to both.

The purpose of a spectrum analyzer is to illustrate the spectral components of an applied signal. It is built to provide clear signal readings without side-lobes or false signals. Since a VNA is meant to measure the stimulus signal it creates and provide fast measurements, it isn’t optimized for this task. The IF filter of the VNA is optimized for speed where the final IF filter of the spectrum analyzer is optimized for spectral purity and therefore measures each frequency point more slowly.

As for using a USB vector network analyzer as a signal generator, the answer is a little more optimistic. It can provide an additional source for a test setup when one is not available. One example scenario is when an engineer might need a source for the LO to a mixer. Or another time might be if a power meter or spectrum analyzer functionality needs to be verified. If interested in learning more about when a VNA needs to be used as a signal generator, read the article here from Copper Mountain Technologies.
 

How Does a Vector Network Analyzer Work?

To expand upon the general working principle of a USB vector network analyzer, the VNA is a complex instrument. It takes the reflection and transmission signals received by the ports and can measure the impedance, amplitude, magnitude, and phase. There are a number of display formats available for viewing the results. For a more in-depth explanation of how a VNA works, you can watch this video or a webinar recording available for review on-demand.

 

 

Vector Network Analyzer Calibration: The Basics

The specifications given by vector network analyzer manufacturers are based upon specific calibration kit. For example, Copper Mountain Technologies’ VNA specifications are created by using an Automatic Calibration Module, or ACM. The VNA is only as good as the calibration kit used to calibrate it. If an ACM is not used, there are a number of calibration methods available, like SOLT or SOLR which may be applied using a mechanical calibration kit. CMT has created a number of assets to assist with different kinds of calibration for vector network analysis which can be accessed here.

 

At Copper Mountain Technologies, our expert engineering team is here to support solutions facilitated using CMT vector network analyzers. The ‘Extend Your Reach’ tagline is not just empty words. Contact our team to engage on a specific solution or questions about using a vector network analyzer and allow them to be an extension to your team.