Ceyear 4041 Series, User Manual

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Chapter IV Spectrum Analyzer Mode
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4.1.8 Measurement of pulse RF signal
1) Definition of pulse RF signal
The pulse RF signal is a RF pulse string of the same repeated frequency, constant pulse width, constant shape and
amplitude. This section introduces several measurement methods of the pulse RF signal parameter. These methods
explain how to measure the center frequency, pulse width and pulse repetition frequency. In addition, topics such
as measurement of peak pulse power are to be discussed.
The resolution bandwidth has significant effects on the measurement of pulse RF signal. It is essential to
understand the relation between the resolution bandwidth and pulse repetition frequency. When the resolution
bandwidth is narrower than the pulse repetition frequency, the screen only shows specific frequency components
forming the pulse RF signal. It is called the narrow band mode. When the resolution bandwidth is wider than the
pulse repetition frequency, it is called the wide band mode. At this time, the display shows the spectral envelope
depicted by the pulse bursts halved by the pulse repetition frequency.
2) Measurement of center frequency, sidelobe ratio and pulse width of pulse RF signal
a) Set the signal generator output signal:
Set the signal generator frequency at 1 GHz and signal power at -20 dBm, and connect the signal generator output
to the input port of spectrum analyzer, as shown in Fig 4-1. Set the pulse modulation to the repetition frequency of
1 kHz, pulse width of 1 us. Switch on the pulse modulation and the RF output.
b) Set the spectrum analyzer:
The pulse RF signal is usually measured at the wide band mode. In order to ensure the video filter does not affect
the measurement results, the video bandwidth is set to 3 MHz.
Press
【
Preset
】
key.
Press
【
Freq
】
, [Center Freq] and 1 [GHz] successively.
Press
【
Span
】
, 10 [MHz],
【
Sweep
】
, [Sweep Time Auto Man], 500 [ms].
Press
【
BW
】
, [Res BW Auto Man], 100 [kHz], [Video BW Auto Man], 100 [kHz].
Press
【
BW
】
, [Detector], [Peak] to activate the positive peak detection.
Select the center frequency function, and adjust the span to display the center sidelobe and at least a pair of
sidelobes on the screen, as shown in Fig 4-20.