Chapter 9 223
Multitone Waveform Generator
Creating, Viewing, and Optimizing Multitone Waveforms
The waveform has nine tones spaced 1 MHz apart with random initial phase values. The center tone
is placed at the carrier frequency, while the other eight tones are spaced in 1 MHz increments from
the center tone. If you create an even number of tones, the carrier frequency will be centered
between the two middle tones.
Figure 9-2
To View a Multitone Waveform
This procedure describes how to configure the spectrum analyzer to view a multitone waveform and
its IMD products. Actual key presses will vary, depending on the model of spectrum analyzer you are
using.
1. Preset the spectrum analyzer.
2. Set the carrier frequency to 20 GHz.
3. Set the frequency span to 20 MHz.
4. Set the amplitude for a 10 dB scale with a 4 dBm reference.
5. Adjust the resolution bandwidth to sufficiently reduce the noise floor to expose the IMD products.
A 9.1 kHz setting was used in our example.
6. Turn on the peak detector.
7. Set the attenuation to 14 dB, so you’re not overdriving the input mixer on the spectrum analyzer.
You should now see a waveform with nine tones and a 20 GHz center carrier frequency that is
similar to the one shown in Figure 9- 3. You will also see IMD products at 1 MHz intervals above and
below the highest and lowest tones.
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