6 things to consider when buying spectrum analyzers

There are various spectrum analyzers in the market, making it hard to choose. You can find radio-frequency, audio, and semi-audio analyzers.

Other analyzers are meant for measuring optical and microwave signals. For example, spectrum analyzers can also be digital, hybrid, or analog.

You can trace the differences in various spectrum analyzer models on sweep rates, bandwidth range, and resolution. This article outlines six things to consider when buying spectrum analyzers.

Dynamic range

Dynamic range is an important specification, regardless of whether you’re buying a new or used spectrum analyzer. It enables you to determine your capability to differentiate signals from the noise floors.

A critical contemplation will be ascertaining your test situation’s lowest level demands. Therefore, the main objective for most measurements could be accurately characterizing the primary signal.

The dynamic range parameters of spectrum analyzers can be confusing.

Mainly, instruments indicate a low DANL (Displayed Average Noise Level) number.

Sometimes, these numbers can be misunderstood because they depend on several factors, including attenuation, preamps, frequency, detectors, and more.

Furthermore, you can compare spectrum analyzers by looking at the optimum dynamic range indicated as two-thirds of the third intercept point minus DANL at one GHz.

Phase noise measurements

Most systems and devices require precise phase noise measurements using spectrum analyzers. However, the analyzers should have low phase noise to avoid affecting device or system measurements.

For most real-world signals, such as complex modulated communications, pulsed tactical, and interference event signals, the energy can be non-recurring, random, or sporadic.

In a traditional spectrum analysis, it may be nearly impossible to get these signals in analysis windows to trigger them.

The modern one increases the challenge further with spread spectrum, frequency hopping, and other techniques.

Resolution bandwidth

The resolution bandwidth is an IF’s bandwidth for determining a spectrum analyzer’s selectivity. Wide resolution bandwidths are needed for broad sweeps, while narrow filters are required for narrow sweeps.

With a narrow resolution bandwidth, the instrument will reveal sidebands. A slow sweep speed is a penalty for applying high resolution.

For example, you can use broad filters when display needs require rapid updating or when you want to display wide modulation bandwidths.

A spectrum analyzer’s minimum resolution bandwidth is a vital measure of its capability for measuring low-level signals alongside higher-level signals and offering the least displayed noise floors.

Level accuracy

Many modern spectrum analyzers use internal calibration signals to correct a change in the IF amplifiers’ gain to maintain sustained level accuracy.

Over a spectrum analyzer’s factory calibration, manufacturers usually connect a power meter system and signal source to characterize their frequency response features and input level while assuming that the features won’t subsequently be changed.

Sweep speed

Spectrum analyzers should be swept slowly enough to let the narrow resolution filter’s signal level settle.

Moreover, in specific conditions requiring high resolution, your sweep speed might have to be as low as 100, necessitating digital storage.

Modern devices usually incorporate microprocessor control to ensure the correct speed. Such as, a manual sweep control is added to a modern instrument to override automation selection.

Frequency stability

A spectrum analyzer’s ability to keep the frequency within specified accuracy levels is called frequency stability, and it depends on the spectrum analyzer’s local oscillator.

It’s a key parameter for narrow-band measurements. Therefore, buy an external frequency reference provision analyzer if you need high measurement accuracy.

Endnote

Selecting a spectrum analyzer can be challenging, but you can consider these factors when buying one to make the decision easier.

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