Time Domain Measurements

In certain situations the spectrum analyzer may be used to take time domain rather than frequency domain measurements. Typical time domain measurements are oscilloscope traces, but when a spectrum analyzer is taking a time domain measurement, the amplitude of only one frequency is measured. To set the spectrum analyzer to a time domain mode, the start and stop frequency have to be set to the same frequency; the frequency of interest. Sweeping with the start and stop set to the same frequency causes the analyzer to take many independent measurements of that frequency over time (in the time domain). This is very useful in determining such things as the change in output power of a transmitter as it warms up. Another use is to capture a peak of a pulsed signal at a particular frequency.