What Is a Network Analyzer? How It Measures RF Devices

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What is a network analyzer? A network analyzer is a test instrument that characterizes how a device responds to a signal. Engineers use it on radio-frequency (RF) and microwave parts such as filters, antennas, amplifiers, cables, and connectors. Keysight’s learning hub describes network analyzers as instruments that characterize radio frequency devices by sending known signals into a device and taking ratio measurements of the input and output signals. The result is a picture of how the device changes the signal across a range of frequencies, not just a single voltage or current reading.

Quick answer

Short answer to what is a network analyzer: A network analyzer sends a known RF signal into a device and measures the ratio of the returned and transmitted waves across a frequency sweep, producing S-parameters, return loss, gain, and phase where the instrument is a vector analyzer.

The core measurement: ratios of incident and returned signals

If you have used a digital multimeter, the idea is different in one important way. A multimeter reads a value at one point in a circuit, usually at DC or a low AC line frequency. A network analyzer sends a signal through or into the device and compares what comes back, at many frequencies in a sweep. That comparison is what lets it describe filtering, reflection, gain, and loss. This guide explains what the instrument measures, the terms you will see on its screen, and where it stops being the right tool.

Network analysis works with ratios. The instrument launches a known incident wave into one port of the device under test (DUT). Part of that wave is reflected back toward the source, and part is transmitted through to another port. The analyzer’s receivers measure those waves, and the software divides them to get the device’s response. Keysight’s hub says the receivers measure incident, reflected, and transmitted signals to calculate the forward S-parameters.

Because the measurement is a ratio, the result does not depend only on how strong the source is. It describes how the device behaves relative to the signal that went in. That is why network analysis is useful for components. A filter, for example, is defined by how much it passes at one frequency and how much it blocks at another, and a ratio shows that directly.

What S-parameters mean

The main output of a network analyzer is a set of S-parameters. For a two-port device, the set is usually written S11, S12, S21, and S22. The number pairs tell you which wave is going where. S11 is the reflection at port 1, S21 is the transmission from port 1 to port 2, and so on. Keysight’s product overview lists the same four terms as the core output of a vector network analyzer, and says they describe how signals reflect and transmit through a device.

From these terms, the instrument can show several familiar quantities. Transmission measurements give gain and insertion loss. Reflection measurements give return loss and voltage standing wave ratio (VSWR). Keysight’s product page notes that impedance can also be derived from these measurements. You do not need to memorize every formula to read the output, but it helps to know which quantity comes from which port pair. A large S11 reflection usually means the device is not matched to the line it is connected to.

Scalar and vector analyzers

Network analyzers come in two broad types. Keysight’s hub explains the difference this way. A scalar analyzer measures magnitude only. Scalar analyzers measure magnitude-based values such as return loss, gain, and standing wave ratio. A vector analyzer measures both magnitude and phase. Early analyzers were scalar, and most instruments in use today are vector analyzers.

The difference matters because phase carries timing information. Keysight’s Used Equipment glossary says that a VNA gives magnitude and phase components, which support complex impedance measurements, and that group delay, the time a signal takes to pass through a device, is one of the quantities it reports. If a task needs phase, such as checking impedance matching or group delay in a high-speed link, a scalar instrument will not give the full answer. For a simple gain or return loss check, a scalar measurement may be enough.

Where network analyzers are used

Keysight’s product overview lists typical uses that include characterizing filters, antennas, amplifiers, mixers, cables, and connectors. It also lists active component tests such as gain compression, group delay, isolation, conversion loss, harmonic distortion, and stability. Application areas named on that page include wireless communications, radar, aerospace, automotive, and 5G.

For a non-specialist, the most common use is checking a passive part against its expected response. A coaxial cable or connector, for example, should pass signal with little loss at the frequencies it is rated for, and should not reflect much energy back toward the source. A network analyzer shows that response across a frequency range in one sweep. A multimeter can check continuity or resistance on the same cable, but it cannot tell you how the cable behaves at 2 GHz.

How a network analyzer differs from a multimeter

The two instruments answer different questions. A multimeter measures voltage, current, and resistance at a point, and it is the right tool for DC checks, continuity, and most electrical troubleshooting in power circuits. A network analyzer measures how a device responds to an RF signal over frequency. It is not a substitute for a meter when you need to know whether a fuse is blown or whether a battery is at the right voltage.

Keysight’s Used Equipment guide lists the maximum frequency as a key specification, and instruments differ in the frequency they can reach. This is a practical point. An analyzer rated to a lower frequency cannot characterize a part that operates above that range, no matter how carefully the measurement is set up. When you read a datasheet, check the frequency span first, then the port count, then the dynamic range.

Calibration and why it matters

Network analysis depends on calibration. Cables, adapters, and connectors between the analyzer and the DUT add their own loss and reflections. A calibration routine measures known standards so that the instrument can remove those errors from the result. The same logic applies to any ratio-based measurement, and a poorly calibrated setup can produce a clean-looking trace that is still wrong. This general point is standard practice; the calibration procedure itself is described in the instrument’s own manual.

Calibration is one reason network analysis is not a quick, one-probe task. The setup includes choosing the frequency span, the number of points in the sweep, the output power, and the calibration kit that matches the connector type. Each of these settings changes the result. Beginners often focus on the trace and forget the setup that produced it.

Time-domain views

A network analyzer can also show a time-domain view of the same data. Keysight’s Used Equipment glossary notes that impedance can be derived from reflection measurements taken at multiple frequencies. Keysight’s time-domain help describes how the software converts the frequency sweep into a time-domain view, where reflections can be read against time, which maps to distance along a line. This is the basis for locating a fault in a cable or connector, and it is closely related to the time domain reflectometer, which is covered in a separate guide.

What a network analyzer does not tell you

A network analyzer does not show a device’s internal construction. It shows the response at the ports, and any model of what is inside has to be inferred from that response. It also does not replace a safety test. If your question is whether a mains outlet is energized, or whether a motor is drawing too much current, you need a voltage tester, a clamp meter, or a multimeter rated for that work. The instrument is designed for RF and signal integrity, and its inputs are not meant for line voltage.

Practical checklist before you buy or use one

If you are considering a network analyzer, start with three questions. First, what frequency range do your parts operate in? The analyzer must cover that span with margin. Second, do you need phase? If so, you need a vector analyzer. Third, what connectors and cables will you use? The calibration kit and adapters have to match the connector type on the DUT.

Then consider the operating environment. Analyzers also come in different physical forms, from benchtop instruments to compact USB units with fewer ports. The right choice depends on the frequency range, port count, and calibration needs of the work, not on the number of features on the front panel.

Frequently asked questions

Is a network analyzer the same as a spectrum analyzer? No. A spectrum analyzer shows the amplitude of signals across frequency. A network analyzer sends a signal into a device and measures the response.

Can a network analyzer measure a battery? It is not designed for that. Battery testing uses DC load and charge equipment, covered in a separate guide on battery testers.

Do I need a network analyzer to check a cable? For a basic continuity or short check, a multimeter is enough. For how a cable behaves at RF frequencies, a network analyzer or a dedicated cable analyzer is the right tool.

How we chose these sources

We opened each source listed below and used only facts it stated. We used manufacturer learning pages, product datasheets, and the Used Equipment knowledge guides, and we did not use retailer listings, forums, or encyclopedias. Where a source was a patent or a search summary, we did not treat it as a citation.

What we could not verify

We could not verify specific frequency limits, port counts, or price ranges for any particular analyzer model from the sources used here. Keysight’s product pages describe families of instruments, but the exact specifications depend on the model and option, and they should be checked on the manufacturer’s current datasheet before purchase. We also did not verify calibration kit part numbers or accuracy figures for any single unit. The general principles above come from manufacturer learning material and the Used Equipment glossary, and they are not a substitute for the instrument’s own manual.

Related reading

For a broader view of how a multimeter measures values at a point, see how a multimeter works. For how battery testers differ from general test instruments, see how a battery tester works.

Sources

• Keysight, Network Analysis hub (opened 2026-10-28)
• Keysight, Vector Network Analyzers overview (opened 2026-10-28)
• Keysight Used Equipment, VNA glossary (opened 2026-10-28)