Spectrum analyzers parallel filter

The classical function of a spectrum analyzer is to measure the power (or amplitude) of a signal at a number of discrete points, or in discrete frequency bands, within a defined frequency range. Normally, the frequency bands are linearly or, more commonly, logarithmically spaced within the spectrum of interest. A very simple method to accomplish this goal is to apply the unknown signal to a parallel array of filters. 

There is a basic trade-off between parallel- and swept-filter spectrum analyzers. The parallel-filter analyzer is fast but has limited resolution and is expensive. The swept-filter analyzer can be cheaper and have higher resolution, but the measurement takes longer (especially at high resolution). Furthermore, since the swept-filter analyzer does not observe all frequencies simultaneously, it cannot be used to analyze transient events. 

Another kind of analyzer has been developed which offers the best features of parallel- and swept-filter spectrum analyzers. So-called dynamic signal analyzers use analog-to-digital conversion followed by frequency-to-time-domain transformation, usually using hard-wired computational machines, to mimic the function of a parallel-filter analyzer with hundreds of filters, and yet are cost-competitive with swept-filter analyzers. In addition, dynamic spectrum analyzers are capable of measuring amplitude and phase accurately these are basically time domain instruments, and their function will be discussed in Section 3.1.4. 

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