Product Details

Vector Network Analyzers


RF and Microwave Vector Network Analyzer:- About, Types, Operation theory & Selection:

A network analyzer is a test and measurement instrument used to measure s–parameters ( reflection and transmission ) of electrical high frequencies signals. Network analyzers are also used to measure the other parameters such as y-parameters, z-parameters, and h-parameters.

  • Network analyzers used to characterize two-port devices such as amplifiers and filters

The two basic types of RF and Microwave network analyzers are

  • SNA -Scalar Network Analyzer used to measure only the amplitude properties.
  • VNA - Vector Network Analyzer is used to measure both amplitude and phase of the signal.

Another major category of network analyzer is the large-signal network analyzer (LSNA), which has the measurement capability of both amplitude and phase of both fundamental and harmonics of the signal.

To learn more about RF and Microwave systems, we recommend you to check the following Books.

To understand the Vector Network Analyzer in a better way, we recommend understanding the following components, which are prime components used along with the Vector Network Analyzer for testing applications.

In this RF and Microwave Vector Network Analyzer article, we will cover,

  • What is a Vector Network Analyzer?
  • Basic measurements using vector network Analyzer?
  • The architecture of vector network Analyzer?
  • S-parameter measurement with vector network analyzer:
  • Calibration and error correction in vector network analyzer?
  • Main specifications of a Vector Network Analyzer:
  • RF and Microwave Vector Network Analyzer Manufactures.

Basic Measurements using vector network Analyzer:

Vector Network analyzers are basically used to measure the amplitude and phase of the RF and microwave signals. Basic measurements can be classified into two categories as transmission and reflection.

Transmission measurements:

For the transmission measurements, Vector Network Analyzer passes the stimulus signal through the DUT (device under test), which is then measured at the receiver port of the Vector Network Analyzer on the other side.

  • The most common transmission S-parameter are S21 and S12 (Sxy for more than 2-port devices).
  • Some other examples of transmission measurements include swept power, gain, insertion loss, phase variation, signal delay, and group delay, etc.

Reflection measurements:

For the reflection measurements, the part of the VNA stimulus signal will pass to the DUT, allowed to reflect back to the source port as a reflection for the measurements.

  • The most common reflection measurements are S11 and S22.

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Design and Application

The architecture of vector network Analyzer:

The basic architecture of a vector network analyzer includes a signal generator, a test set, receiver, processor, and display. In 2 port VNAs have two test ports, for the measurement of four S-parameters and there are instruments available with more than two ports.

Signal generator:

The built-in signal generator inside the vector network analyzer will provide a test signal to the DUT. High-performance vector network analyzers will have two sources, for the applications such as mixer test, where one source provides the LO signal, another the RF signal, or for the amplifier intermodulation testing, where two signal tones are required for the test.

Test set:

The test set is used to route the signal generator output to the DUT (device under test) and then to the receivers. In a VNA, the Signal often splits off a reference channel using a directional coupler and goes to the receivers for the phase reference measurement along with the amplitude measurement using a detector in the receiver.


The receivers in the network analyzer make the measurements connected to test ports. The reference port is usually labeled R, and other primary test ports are labeled as A, B, C, etc. Analyzers may have a dedicated receiver to each test port, or one or two receivers may share among the ports.

The receiver in the VNA will measure the magnitude and the phase of the received signal using the reference channel (R). In general RF signal will down converts using a down converter and make the measurements at a lower frequency. The phase of the signal will be measured using a quadrature detector. Some VNA permits simultaneous measurement of different RF parameters using in-built three or four receivers.


The reflection and transmission data is measured and formatted using an inbuilt processor to make the information available in an easily understandable way as possible. Most RF network analyzers have linear and logarithmic sweeps, trace markers, limit lines, and pass/fail criteria, which all are controlled and processed by the in-built processors.


In the display, processed RF signal from the receiver section is displayed in a format that can be interpreted to the uses in different formats like log formats, polar plots, Smith charts, etc.

S-parameter measurement with vector network analyzer:

The prime function of the VNA is to test scattering parameters or S parameters of radio-frequency and microwave devices for its characterization.


The test port of the VNA is calibrated and connected to P1 and P2 using precision cables PC1 and PC2 respectively and use suitable RF adaptors A1 and A2 respectively for establishing the connection. The test frequency in a VNA is generated by a variable continuous-wave frequency source with a variable attenuator to set the power level and a switch SW1 to sets the direction of the test signal to DUT.


Initially, the test signal generated by the CW source is fed by SW1 to the common port of splitter 1, one port is connected to the reference channel for P1 (RX REF1) and the other connecting to P1 through the directional coupler DC1. The third port of DC1 is used to a couple of the reflected power from P1 via A1 and PC1, and the coupled signal is feed to test receiver 1 (RX TEST1). Similarly, signals from P2 pass via A2, PC2, and DC2 to RX TEST2.

  • RX REF1, TEST1, REF2, and TEST2 are called coherent as they share the same reference oscillator, to measure signal amplitude and phase.

Similarly for measuring the S22 parameters SW1 is set to position 2 to set the signals P2, reference by RX REF2. The reflections from P2 are coupled off through DC2 and measured by RX TEST2. The signals leaving P1 are coupled off through DC1 for the measurement by RX TEST1.

Process and Display:

Then the receiver output signals are fed to a processor for mathematical processing and display the measured phase and amplitude parameters in the format selected on the display.

Calibration and error correction:

A vector network analyzer requires periodic calibration either by the manufacturer or by any certified calibration laboratory that can provide the calibration certificate with traceability of standards.

  • Calibration helps to identify and correct the systematic errors in the instrument. The error correction is performed by an engineer several times in the lab itself before the use of the VNA is called user calibration.

As VNA uses external cables from the port to the DUC and needs to use many RF components like a coupler, Adapter for the testing, all will add up to the system error.

The calibration process usually involves measuring against the know standards for systematic errors compensation. Using user calibration only the systematic errors can be identified and corrected. Random errors, like connector repeatability, can be corrected by the periodic calibration in the calibration laboratories.

For vector network analyzers, designed for field testing using batteries with lower accuracy measurement need correction for temperature variation, it is done by measuring the internal temperature of the VNA.

User calibration Steps:

The calibration process involves visual inspection, cleaning, measurement, correction.

Visually inspection: First the connectors are visually inspected to identify the problems such as bent pins or off-center etc.

Cleaning: All the RF connectors clean with compressed air, if necessary using isopropyl alcohol and keep it dry.

Measurement / Gage: All the connectors will gage to identify any mechanical problems with accuracy resolutions of 0.001" to 0.0001".

Correction: Tighten all the connectors using a torque wrench to the specified torque.

Methods of calibration.

Mainly there are 2 types of calibration is followed SOLT (Short, Open, Load, Through) and TRL (through-reflect-line calibration).

SOLT (Short, Open, Load, Through):

SOLT is the easiest calibration method using the known standards of Short, Open circuit, load (usually a precision 50 ohms), and a through connection. Calibration is done by connecting each standard in sequence and measuring the variations and tuning the instrument to correct the variations.

  • SOLT calibration is suitable for coaxial measurements, as it is easy to obtain the calibration SOLT standard. The SOLT calibration is less suitable for the calibration of waveguides, due to the difficulty to obtain suitable standards.

TRL (through-reflect-line calibration):

TRL calibration is suitable for noncoaxial microwave environments such as fixture, waveguide, or wafer probing. TRL uses a transmission line of known length and impedance as one standard and a high-reflection standard (usually, a short or open) whose impedance must be electrically the same for both test ports.

The simplest calibration on a network analyzer that provides a piece of phase information is a 1-port calibration of S11 or S22 which provides three systematic errors measurements:

Directivity:  Error indicates that the source signal does not reach the DUT.

Source match: Error indicates multiple internal reflections between the DUT and source.

Reflection tracking: Error indicates frequency dependence of connections, test leads, etc.

  • In 1-port reflection calibration, the user measures with standards, like open, short, and load to identify the above three errors.
  • In full 2-port reflectivity and transmission, calibration involves measuring a short, load, and open standard on transmission between the two ports as well as each of the two ports.

Electrical Calibration ( E-Cal):

An electrical calibrater or E-Cal is an electronic calibration unit that can generate the required open, load short, and through values. Automated software in VNA associated with the E-Cal will execute the calibration procedure once it is connected and the start calibration.

  • E-Cal calibration is used for the quick calibration of the VNA measurement setup. However, it is ideal to go with SOLT or TRL calibration for more accurate calibration of the VNA than calibrating using an E-Cal.

Type of Vector Network Analyzer:

Vector network analyzers are classified into four form factors mainly based on the package it offers, Benchtop, portable, handheld, and USB.

Bench-top Vector Network analyzer:

Benchtop Vector network analyzers are generally AC power operated instruments, designed for use in a lab environment of R&D and production where more accurate measurement specifications are required. Benchtop Vector network analyzers will have more measurement capabilities and accuracy compared to other models. 

  • The benchtop model includes the PXI based Vector network analyzers (FPGA card-based), which have the future expansion capability for the frequency range of operations Extention and number of ports up-gradation.

Portable Vector Network analyzer:

Vector network analyzers with battery backup are called Portable VNA, these batteries allow them to be used in the field with any other real-time systems for the random check in the field. These models allow the test engineers to move freely with the units around the field for the testing.

Handheld Vector Network Analyzer:

Handheld Vector network analyzers are very small in size and light-weighted with battery operation capability. Handheld Vector network analyzers usually have very limited accuracy and measurement capability compared to benchtop analyzers.

USB Vector Network Analyzer:

USB VNAs use computers for the measurements, processing, control, and display by connecting them to the computer over the USB port. These types of vector network analyzers are very cost-effective and have now started to hit the market. As computers are easily available in RF labs along with other test instruments, choosing a USB vector network analyzer with the associated software will help in making a cost-effective test solution.

Basics & Selection Feature

Main specifications need to consider in the selection of a Vector Network Analyzer: 

Below are some of the key parameters for Vector Network Analyzer that need to be considered when selecting a suitable RF and microwave network analyzer for any test and measurement applications.

Frequency range:  

The frequency range of the vector network analyzer defines the minimum and maximum frequencies over which it can measure. When selecting a VNA for the RF test application it is necessary to consider the harmonics frequency range in addition to the fundamental frequency as it is important to know the response at harmonic frequencies

Measurements at the multiple harmonics are important for the RF components like amplifiers, mixers, converters, etc. Considering the harmonic and spurious factors vector network analyzer's top frequency should be at least two to three times covering the maximum operational frequency.

The number of test ports:  

A vector network analyzer is available with two, four, or more test ports options. The number of required test ports is dependent upon the number of ports in the DUT. As the number of ports increases the complexity and the cost of the test system will increase. Many RF devices require two ports, for tests but the components like mixers and RF switches need more than 2 ports for the perfect measurements.

Dynamic range:  

The vector network analyzer dynamic range defines the range of power levels over which the RF network analyzer will perform the measurements. This is the range between the maximum and minimum power levels that can be fed to the VNA for the measurements. Ideally, VNA specification should least better by 5 to 10 dB than the maximum DUT attenuation anticipated.

Trace noise:  

The vector network analyzes trace noise to indicate the amount of noise present on a VNA measurement. Trace noise is an important parameter for measuring filter ripple performance and is measured in milli-dB (0.001 dB). These are the noise generated within the analyzer and a key factor in the measurement accuracy. Lower the trace noise better the instrument for the test and measurement applications.

Measurement speed:  

Measurement speed indicates the time required to perform a sweep over a range of frequencies, taking measurements over the range of frequencies.

For one-off bench tests, measurement speed may not be an issue, but measurement time is significant where a lot of measurements need to execute to characterize a device over various test scenarios especially in the production environment.

  • The user calibration time required before each new measurement also needs to consider for the measurement speed as it will affect overall measurement time.

Interference isolation:  

If a vector network analyzer is used as an isolated instrument, interference will not be a critical factor, but if it is used in an automated test setup where many instruments are associated along with the VNA, interference will be a critical factor. Interference from the other instruments may affect the reading of a VNA, hence the proper isolation will be an added advantage in the measurement capability.

External Interface and display:

Nowadays especially in the production environments, vector network analyzers are used along with the other instruments, and the entire test is automated through the computer. To make the system automated an external interface like ethernet, RS232, GPIB is needed as per the test set automation requirements for the easy interface.

The display of the VNA is another critical factor in the consideration. Now most of the VNA comes with a remote interface for the control and monitoring from the remote desk.


Vector network analyzers analyzer is one of the prime test and measurement instruments in the RF and microwave industry. vector network analyzers are available with different additional test features like spectrum analyzer, frequency counter, power measurement capabilities, etc.

Below are the top Vector network analyzers manufacturers, who can offer a suitable test instrument for the test requirements.

If you would like to add any further details of Vector network analyzers to this article, please feel free to contact us over the contact or article submission page.

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RFMWC:RF & Microwave Community

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