Few pieces of engineering equipment are as fundamental as a spectrum analyser. With their help, it’s possible to quickly determine what kinds of frequencies are present in a given signal. Their role is distinct from other kinds of signal-analysis device, like oscilloscopes – but, in certain fields, they remain just as essential.
Before we go any further, we should explain exactly what a spectrum analyser is, as well as how it works. They’re used to examine radio, RF, and audio signals. They present this information in the form of a distribution of bars, whose size on the Y axis corresponds to the amplitude of the corresponding frequency.
Spectrum analysers come in several different varieties, including ‘swept’ analysers, Fast Fourier Transform analysers, and so-called ‘real-time’ analysers. If you’re solely concerned with audio frequencies, you might be able to get by without specialised hardware. In fact, you might be able to use software on a computer.
Wherever a system relies on the transmission or reception of signals, a spectrum analyser can be instrumental in prototyping, refining and troubleshooting. They can be useful in radar design, as well as in EMI diagnostic scanners.
What makes one analyser different from the next? There are a few important metrics to look out for. You’ll want a frequency range that matches your intended application. If you’re going to be looking at radio signals, then you’ll need a spectrum analyser capable of handling them.
There’s also the resolution bandwidth, or RBW, which is the smallest difference in frequency the analyser can see. If there’s a weak signal right next to a very strong one, you’ll need to use a narrow RBW.
We should also spell out the difference between real-time and traditional analysers. The latter work by sweeping continuously across the range, which makes them prone to missing very quick pulses of interference. The former are perfect for spotting those pulses.
If you’re in a high-stakes environment where faults need to be analysed quickly, then you’ll need a spectrum analyser that you can rely on. Thus, we should also consider a few criteria that aren’t quite as easy to quantify. The build quality and reliability of the device will matter hugely when every second counts. For this reason, many engineers will pick out a given manufacturer and stick with them.