Zero Span

Zero Span mode is not supported for Time Domain input mode.

Zero span is a mode of a spectrum analyzer in which the local oscillator (LO) does not sweep. The spectrum analyzer’s LO remains fixed at a given frequency so the analyzer becomes a fixed-tuned receiver. The bandwidth of the receiver is that of the resolution (IF) bandwidth. In case of zero span, signal amplitude (or power) variations are displayed as a function of time.

To avoid any loss of signal information, the resolution bandwidth must be as wide as the signal bandwidth. To avoid any smoothing, the video bandwidth must be set wider than the resolution bandwidth.

Uses of Zero Span

The following are the uses of zero span:

Zero span is sometimes used for noise and noise-like measurements where the noise bandwidth is much greater than the RBW Resolution Band Width (RBW or ResBW): specifies the minimum frequency bandwith that two separate frequency spectra can be resolved and viewed seperately. For FFT (digital) based VSA's the process is equivalent to passing a time-domain signal through a bank of bandpass filters, whose center frequencies correspond to the frequencies of the FFT bins. For a traditional swept-tuned (non-digital) spectrum analyzer, the resolution bandwidth is the bandwidth of the IF filter which determines the selectivity., such as in the measurement of power spectral density.
Zero span can be used to determine appropriate trigger levels on a gated spectrum measurement.
The carrier power of a transmitter is measured with the spectrum analyzer in zero span.
A trigger and gated analysis may be used if the carrier power is to be measured over a specified portion of a burst-RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz). signal.