The Best Portable Spectrum Analyzers on the Market
To describe a spectrum analyzer in four words or less, one could say “Portal into another dimension”. If this sounds like science fiction, perhaps it’s no coincidence.The wide range of form factors and features available in modern spectrum analyzers parallels the future world envisioned by fiction writers decades ago.
Today’s wireless, microwave, audio and optical technologies and their countless practical applications are something we often take for granted, and if it’s difficult to imagine our world without this technology, it’s impossible to imagine this technology even existing without the use of spectrum analyzers.
The History of Spectrum Analyzers
In the mid-19th century, the concept of a spectrum analyzer would indeed have seemed like science fiction, since the very nature of electrical and magnetic waves had not yet been discovered. Then, in 1865, James Clerk Maxwell published his revolutionary Dynamical Theory of the Electromagnetic Field, which for the first time accurately characterized the behavior of natural electrical and magnetic waves moving through the airwaves at the speed of light - radio waves. Prior to that time, scientists and practitioners had noticed anomalies such as inadvertent audible transmissions or coincident “sparks” between telegraph stations, but had attributed them to the “ether” or otherwise dismissed them.
In 1885, Heinrich Hertz proved that you could send and receive electrical waves wirelessly, and was bestowed the appropriate honor of having the frequency unit of measure named after him.
What Maxwell had described was like a giant superhighway in the sky, but with no vehicles on the road, no maps and, as yet, no on-ramps. Harnessing this new discovery would take decades.In 1885, Heinrich Hertz proved that you could send and receive electrical waves wirelessly, and was bestowed the appropriate honor of having the frequency unit of measure named after him.
By the 1940’s, Maxwell’s superhighway was becoming super crowded, as the innovation and utilization of radio progressed year after year.Like any other “hidden dimension”, our ability to see and analyze the radio waves was still very limited.The oscilloscope had been developed as a tool to track signal voltage in the time domain by visually plotting the waves on a small CRT display. This instrument had many useful applications in science and engineering, but more innovation was needed to continue the technological evolution.The development of the spectrum analyzer in the early 1960’s was a quantum leap forward.
In a basic sense, anyone who has ever attempted to tune a simple transistor radio has used their ears and fingers to simulate the function of a spectrum analyzer.
In a basic sense, anyone who has ever attempted to tune a simple transistor radio has used their ears and fingers to simulate the function of a spectrum analyzer.As you move the dial through the span of frequencies, you can hear the signal strength and bandwidth of the utilized frequencies (channels), the inherent noise accompanying the signal, as well as the underlying noise floor beneath all channels. If this information were to be transferred to a graphical format, the result would look a lot like the display of a spectrum analyzer.
While the oscilloscope plots the voltage in the y-axis against the time value in the x-axis, the spectrum analyzer graphically tracks the amplitude (signal strength in dB) in the y-axis against the frequency (in Hz or MHz) in the x-axis. Early analyzer features also included adjustability of the span and center-point for the observed frequencies and markers for the frequencies of interest.
The Many Applications of Spectrum Analyzers
Since their humble origins of 50+ years ago, the application and functionality of spectrum analyzers has continued to progress.
The increased use of Wi-Fi and the cell phone revolution have underscored the need for state of the art spectrum analyzer technology in the radio frequency field.
The increased use of Wi-Fi and the cell phone revolution have underscored the need for state of the art spectrum analyzer technology in the radio frequency (RF) field.As telecommunication networks expand, spectrum analyzers are used to determine frequency utilization and interference in a given area.They can also be used to determine the accuracy of a wireless transmitter by comparing the frequencies and bandwidths of an output signal to a received input signal.As we will discuss later, the balance between portability and functionality is extremely important with this type of field application.
RF shielding is required for electronic equipment that will reside in the vicinity of MRI imaging systems, as the electronics can emit unintended signal that potentially distort the imaging results.Similarly, electromagnetic compatibility (EMC) is concerned with the unwanted emissions that many types of electrical or electronic devices produce, and their influence on existing wireless communication transmissions.A spectrum analyzer is an ideal testing tool for either of these scenarios.
The applications of spectrum analyzers in the RF arena alone are as diverse as the signals that travel through the airwaves and beyond.There are many other applications of spectrum analyzers outside the RF arena as well, and the list of applications will no doubt continue to grow.
Types of Spectrum Analyzers
The tuning of a radio receiver is probably a very good analogy for the function of a spectrum analyzer because it actually is a lot like a spectrum analyzer in concept and architecture.In their earliest forms, the two circuits were very similar.Only the quality and design of the mixer and oscillator, along with the use of a display rather than a speaker, made the spectrum analyzer more than just a radio receiver.
Spectrum Analyzer Functionality
The basic functionality of a spectrum analyzer has changed very little since the earliest models.Once the equipment is powered on and an input has been selected, basic settings consist of selecting the center frequency, span width and reference levels for the amplitude (y-axis).The resolution band width (RBW), video band width (VBW) and sweep time settings are used to control the precision of the measurements and resulting image on the screen.Since the RBW sets that width of the filter that sweeps across the signal, a lower RBW means higher resolution and a more detailed and accurate picture of the signal.
Beyond these basic settings and controls, additional features can typically be placed into one of two categories - practical and nice-to-have. The first commercial spectrum analyzers already incorporated such practical features as span adjustability, frequency markers and sweep time adjustability.Additional features that are highly desirable for almost any type of application include noise markers, peak search, tracking generators and additional input ports for multi-channel analysis.
For RF spectrum analyzers, inclusion of a demodulator allows the user to “listen” to the signal being analyzed. Spectral masks take the utility of markers to another level by creating an outline for your “acceptable” signal and noise profile, then telling you whether or not you are within specification.
With the current level of computer integration into spectrum analyzer design, most of the nice-to-have features that lend ease of use, programmability and connectivity are more closely tied to software development rather than hardware.The feature sets now available through software are virtually limitless. Some of the more useful and interesting software features include:
- Image capture to .jpg or .pdf
- Memory and recall features
- Touch screen displays
- Programmable phase noise analysis routines
Like all electronic equipment, functionality and feature sets can vary from the standard issue to the mind-boggling with unlimited combinations in between. Understanding your specific application and what is required to complete your tasks efficiently is a good prerequisite for deciphering product specifications and feature lists.
In the 150 years since James Clerk Maxwell gave us our first glimpse into the unlimited potential of the airwaves, the spectrum analyzer has become a truly indispensable tool in the electronics, RF, audio and optical fields.
Had the spectrum analyzer never been developed, it would not have been possible to analyze the elements of a signal or gauge a circuit’s performance.The laser would have remained the stuff of science fiction, and the telecommunication networks that have become synonymous with modern society could not have existed. Since spectrum analyzers are able to perform a wide variety of measurements for a number of different functions, the utility of this innovation cannot be overstated.
Much like the evolution of the radio “superhighway” as the number of applications grew exponentially in the mid-1900’s, the functionality and features available for modern spectrum analyzers have vastly expanded in the past decade, as computer technology continues to enable more features in compact form factors.
Today, the spectrum analyzer may seem more like an essential tool for a familiar dimension than a portal into a hidden one as history has taught us that the impossible often becomes possible with the right tools in hand.
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