Spectrum Analyzers

The majority of telecommunication applications and activities in radio communication use spectrum analyzers for the examination and analysis of frequency signals. Spectrum analyzers are incredibly useful and widely used frequency measuring instruments. They are used for measurements and analysis of signals in frequency domain, time domain and modulated domain. Like signal analyzers, spectrum analyzers are passive receivers that present electrical signals to the user in an easier to read form. They display raw, unprocessed signal information such as voltage, power, period, wave shape, sidebands, and frequency.

Technically, spectrum analyzers are defined as testing instruments used to inspect the constitution of frequencies of electrical, acoustic or optical waves. The spectrum analyzers measure the spectral density of a signal, which is the strength of the frequencies.

Spectrum analyzers can perform modulation, distortion, and noise tests. Measuring the quality of the modulation is important for making sure that a system is functioning correctly and that the data is transmitted properly. In communications, measuring the level of distortion is essential for both the receiver and transmitter. If there is too much harmonic distortion at the output of a transmitter it can interfere with other communication bands. Because any active circuits or devices will generate noise it’s important to measure the levels. Tests such as noise figure and signal-to-noise ratio (SNR) should be performed to find out the overall system noise.

Spectrum analyzers are available in two types and which one is used depends on the type of application.

A swept-tuned spectrum analyzer uses either a variable band pass filter whose mid-frequency is automatically tuned through the range of frequencies of which the spectrum is to be measured or it uses a superheterodyne receiver in which the local oscillator is swept through a range of frequencies.

A digital spectrum analyzer uses the Fast Fourier Transform (FFT), which is a mathematical process that transforms a waveform into the components of its frequency spectrum. Because of this, computer programs are able to compute these transforms and it makes audio processing a much easier task.

The swept-tuned receiver is the most common type of spectrum analyzer as it is the most widely accepted, general-purpose tool for frequency-domain measurements. There are some important physical specifications you need to consider while looking for a spectrum analyzer such as mounting and form factor. Analyzers can be handheld, portable, bench top, and fixed. A spectrum analyzer is generally an instrument based unit or pc-based unit.

When you are searching for a spectrum analyzer there are also some important frequency performance specifications to consider such as the frequency range, frequency accuracy, and frequency resolution. It is essential for a spectrum analyzer to cover the fundamental frequencies of the application, as well as harmonics or spurious signals on the high end, or base band and IF on the low end.

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