A Tektronix demo board provides test signals to a 306 PC-Based Spectrum Analyzer and various parameters are displayed.
Hello once more and welcome to our 76th Test and Measurement Video. We’ll continue our exploration of the many capabilities and advanced features of the Tektronix RSA306 PC-Based Spectrum Analyzer.
The relatively low cost of this instrument as compared to a traditional bench-type, real-time or swept-spectrum analyzer is due to the fact that with no moving parts, external controls or internal electrical contacts, it simply connects via USB to an owner-supplied PC. The enabling software, available as a free download at the Tektronix website, is SignalVu-PC, which can be easily installed in the computer.
Today we’re looking at analog (not to be confused with amplitude) modulation and how it is displayed in a PC connected to the the RSA306 Spectrum Analyzer. To see how this works, we’ve cabled together the Tektronix spectrum analyzer module, the proprietary demo board and a laptop PC with SignalVu-PC software installed.
By way of review, there are three principle types of analog carrier-wave modulation – amplitude, frequency and phase. Any one of these properties of the periodic carrier wave can be varied so as to carry information. A modulator, at the transmitter, performs the operation and the desired information is recovered at the receiver by the demodulator. A modem, as used in cable and satellite dish Internet service, is a device that can perform either operation.
This demonstration focuses on the very widely-used frequency modulation.
Keep the same demo board settings as in Video 75, except for signal type, which with the row and column buttons should be changed from infrequent hopping to FM.
For this analog modulation demonstration, begin by clicking the Preset button. Then, click the Display button.
In General Signal Viewing, select DPX from the Available Displays box.
Click the Add button. This will add the DPX icon to the Selected Displays box and remove it from the Available Displays box.
In Analog Modulation, select FM from the Available Displays box. Click the Add button. Then click the OK button.
Select the DPX display by clicking anywhere with the mouse, and set the Center Frequency to 2.445315 GHz, and the Span to 500 kHz.
Click the Analysis Control button.
Under the Analysis Time tab, set the Analysis Length to 10 ms.
Click the FM display and the click the Settings button.
Under the Parameters tab, set the Measurement Bandwidth to 200 kHz.
The FM Measurements readouts are:
+Pk: Positive frequency Deviation
-Pk: Negative frequency Deviation
RMS: Root Mean Square Deviation
Pk-Pk: Peak-to-peak Deviation
Pk-Pk/2: Peak-to-peak Deviation divided by two
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