How do I use the spectrum analyzer function on the MDO3000?
Hello and welcome to Tektronix! Today I’m going to demonstrate the spectrum analyzer capability on the MDO3000 mixed domain oscilloscope.
The MDO3000 contains a full-fledged spectrum analyzer with many useful features, including automatic markers, a spectrogram, automatic measurements, and up to 3 GHz realtime capture bandwidth. The MDO3000’s RF port is on the right side of the analog channels and has an N-type connector. I’m using an N-to-BNC adapter with a BNC cable to connect my signal source to the MDO.
To access the spectrum analyze, simply press the orange RF button. I know my signal is centered at around 2.4 GHz with a 20 MHz span, so I’ll use the Frequency/Span menu to adjust those. Press the Freq/Span button and use either the multipurpose knobs or the keypad to configure the center frequency and span or the start and stop frequency. Notice that the peaks are automatically marked by the MDO with frequency and amplitude information. The markers can be configured in the Marker menu. To turn the markers on or off, select the Peak Markers softkey to select it, then press it again to toggle the markers on and off. You can also use the multipurpose knob A or the keypad to change the number of markers. If you weren’t quite right on the center frequency, you can move the center frequency of the spectrum analyzer to the frequency of the reference marker by pressing the R to Center button.
The marker threshold and excursion can be changed with the multipurpose knobs or the keypad as well. Threshold sets the level above which markers will be applied to peaks, and the excursion determines how far the signal amplitude needs to fall between peaks for a marker to be applied. As I increase either parameter, the markers on the lower peaks disappear because they no longer meet the criteria because their amplitude is lower than the threshold or the excursion between peaks is lower than the excursion limit. You can also turn on Manual markers that can be controlled by the multipurpose knobs. When manual markers are activated, marker A becomes the reference marker. The marker readout can be changed from absolute to delta. When delta is activated, the frequency and amplitude information on each marker is referenced to the reference marker, and if manual markers are active, noise density is applied to marker A and phase noise information is applied to marker B.
In addition to the automatic markers, the MDO spectrum analyzer also has a spectrogram function. To access the spectrogram, press the orange RF button, press the spectrogram softkey, and press the Display softkey until it toggles on. A spectrogram is a display that captures RF over time and is ideal for analyzing RF signals that change slowly in time. Frequency is measured on the horizontal axis, time is measured on the vertical axis, and amplitude is measured by assigning different colors to pixels with cool colors showing low amplitude and warm colors showing high amplitude signals. When the spectrum analyzer is stopped, you can scroll through each slice of the spectrogram using Multipurpose knob A. Each slice shows the spectrum as it was captured at that time. Each slice is both numbered and time-correlated. Notice as the spectrum changes, the automatic markers update as well.
In addition to being a powerful oscilloscope, the MDO3000 adds the functionality of a full-fledged spectrum analyzer to its repertoire, making it an irreplaceable addition to the testbench.
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