What is a Network Analyzer?

In this article, we will be talking about what is a NA and the different types.

Understanding Network Analyzers

Please notice: The term Network Analyzer is not to be confused with telecom network protocol analyzer, packet analyzer or Network analyzer.

The RF/microwave industry is known for its adoption of network analyzers as indispensable test instruments. Instruments in this industry are capable of characterizing a broad range of components, device as well as systems. In the events of manufacturing production testing, network analyzers are heavily relied upon, and a significant number of components are measured with the use of network analyzer, some of which include amplifiers and attenuators, among others. A network analyzer provides a substantial amount of information that appears on a component’s datasheet. Furthermore, research and development utilize network analyzers extensively, used in the measurement of engineering prototypes, providing engineers with the optimization of performance attributes such as return loss. 

Types of NA

Two main types of network analyzers are generally accepted, one of which is the Scalar Network Analyzer (SNA), which is responsible for the measurement of amplitude properties alone and the other which is known as Vector Network Analyzer (VNA) known for the analysis of amplitude as well as phase properties.

• Scalar Network Analyzer (SNA): as stated above, a scalar network analyzer measures only amplitude properties such as the amplitude response of an RF network to a stimulus previously applied. When trying to obtain a good insight into numerous aspects of network operations, a scalar network analyzer comes in handy. To effectively exploit the efficiency of a scalar network analyzer, SNA, they are used as a spectrum analyzer together with a tracking generator. The frequent use of a tracking generator and spectrum analyzer provides an operation that is electrically closed. 

A swept signal is generated by the tracking generator on the same frequency being received by the spectrum analyzer. Therefore, a product from the tracking generator with a direct connection to the spectrum analyzer input will result in a continuous line that would be seen across the screen of the analyzer, which indicates the amplitude of the tracking generator output. The placement of a device between two items allows the spectrum analyzer to note any variations in amplitude. The response for this, for example, can be plotted. There will be room for the ever-present output of the tracking generator in the filter, where there will be an alteration to the filter response per the frequency and the filter response at that particular frequency, giving the spectrum analyzer the ability to display the filter’s response vividly. The activities of a scalar network analyzer, through the above illustration, projects its usefulness in measuring the amplitude response of numerous components and broad variation.

Scalar NA

Some examples of the scalar network analyzer include:

• SARK 110: features of this portable analyzer with graphical display includes; pocket size and lightweight, 
• solid aluminum case,
• intuitive and easy to use, 
• resolves sign of the impedance, 
• manual and automatic positioning tracking markers,
• transmission line add and subtract,
• Operating modes: scalar chart, smith chart, single frequency, field mode, multi-band, single generator, and computer control.
• Internal 2MB USB disk for the storage of measurements, screenshots, and configuration.
• Open-source Software Development Kit (SDK), including a device simulator for the development of user application. 
• MFJ 225 antennae: this scalar network analyzer measures;
• Complex impedance
• Impedance magnitude
• Capacitance
• Inductance
• Cable length, and
• Cable loss.

Other scalar network analyzers include Scalar network analyzer 8757D from Agilent Technologies. 

• Vector Network Analyzer (VNA): the verification of design simulations and the testing of components specification utilize vector network analyzers to ensure the smooth functioning of systems and their components. Ranging from mobile networks to Wi-Fi networks and then the computer as well as cloud services, every known technology network of today relied on the vector network analyzer that was first invented over 60 years ago. In the course of product development, R&D engineers, as well as manufacturing test engineers, popularly utilize VNAs. It is crucial for component designers to verify how efficient their components perform; some of these components include amplifiers, cables, and antennas. Components specifications also need to be verified by system-designer to ensure that the relied upon system performance meets system and sub-system specs. Furthermore, Vector Network Analyzers are used by manufacturing lines to ensure that specifications and products align before the final shipment for customer use. The operation of a Vector Network Analyzer is characterized by a source, responsible for known stimuli signal generation, and a specific set of receivers used in the determination of stimulus alteration caused by the device under test (DUT). Before the measurement of signals reflected from the input and that which passes out through the output exit of the DUT by the Vector Network Analyzer, the DUT takes in the stimulus signal via injection. Resulting signs are measured and compare to the known stimulus signal by the Vector Network Analyzer. Through the use of either an internal or external PC, the measured results are processed and therefore sent to display. 

The utilization of Vector Network Analyzer’s point to two types of measurement, which are that of transmission and reflection. The measurement of transmission sends the vector network analyzer stimulus through the DOT, followed by measurement using VNA receivers. S-parameter’s are used during transmission measurement, and some of the common S-parameter measurements, in this case, include S21 and S12 (Sxy is used where there are more than two ports). Some good examples of transmission measurements include electrical length, gain, insertion loss, and group-of-delay. Reflection measurement, on the other hand, measures a part of the VNA stimulus, which upon the DUT is incident, it, however, doesn’t pass through it. 

The reflection measurement rather measures the signal which travels towards the source in a backward manner as a result of reflection. Some good examples of the vector network analyzer include the TTR503A and TTR506A vector network analyzer. 

Overall, the selection of the most suitable network analyzer is significantly dependant on what is required of the network analyzer and the purpose for which it will be put to use. When there is requirement for a fast sweep which will measure magnitude parts alone, the Scalar Network Analyzer is favored, and when there is a requirement to measure amplitude and phase of incident and reflected waves at ports of DUT, the Vector Network Analyzer is preferred.