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PDF (Thesis) - Nottingham eTheses - University of Nottingham

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CHAPTER 5: EMI MEASUREMENTS<br />

will trigger the frequency measurement for every frequency step. A RF cable must be<br />

plugged from the output <strong>of</strong> Signal Generator into the Spectrum Analyser, to feed the<br />

signal into the measuring instrument.<br />

BW: Res BW→100kHz<br />

Settings on the Spectrum Analyser<br />

AMPTD Yscale: More→YAxis unit → A<br />

Trace/Detector: Max Hold<br />

Trigger: External 1<br />

FREQ Channel: Start Freq→100kHz<br />

Stop Freq→30MHz<br />

Sweep/Control: Points→29901<br />

Input/Output: RF Input→RF Coupling→DC<br />

Settings on the Signal Generator<br />

Sweep/List: • Sweep Type→Step<br />

Frequency: 100KHz<br />

Amplitude: -10dBm<br />

• Sweep Repeat→Cont<br />

• Configure Step Sweeps: – Freq Start → 100kHz<br />

– Freq Stop→30MHz<br />

– # Points→29901<br />

– Step Dwell→40 ms<br />

Once the sweep on the Signal Generator will be complete, the Spectrum Analyser will<br />

have stored the reference, that will have to be exported to provide the vector <strong>of</strong> current<br />

vs. frequency values.<br />

Once the reference is saved, the proper measurement for the probe’s impedance has<br />

to take place. For this calibration the probe must be placed in the Current Probe Cali-<br />

bration Fixtures, as in Fig. 5.4; for this configuration four connections are needed: the<br />

usual two BNC for the 10MHz and the trigger signal, then two RF cables, one to con-<br />

nect the probe to the spectrum analyser and the other to connect the signal generator<br />

to the calibration Fixture (the metallic box visible in Fig. 5.4). Note: the other plug <strong>of</strong><br />

the calibration fixture must have a 50Ω terminator to match the cable’s impedance.<br />

The settings on the instruments are the same as before, with the only exception for the<br />

Y scale on the spectrum analyser, this parameter should now be volts (V), to read the<br />

60

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