Spectrum Analyzer - Types

Types

Spectrum analyzer types are dictated by the methods used to obtain the spectrum of a signal. There are swept-tuned and FFT based spectrum analyzers:

• A swept-tuned spectrum analyzer uses a superheterodyne receiver to down-convert a portion of the input signal spectrum (using a voltage-controlled oscillator and a mixer) to the center frequency of a band-pass filter. With a superheterodyne architecture, the voltage-controlled oscillator is swept through a range of frequencies, enabling the consideration of the full frequency range of the instrument.
• A FFT spectrum analyzer computes the discrete Fourier transform (DFT), a mathematical process that transforms a waveform into the components of its frequency spectrum, of the input signal.

Some spectrum analyzers, such as real-time spectrum analyzers, use a hybrid technique where the incoming signal is first down-converted to a lower frequency using superheterodyne techniques and then analyzed using fast fourier transformation (FFT) techniques.