NOTE

Making Basic Measurements

Demodulating AM Signals (Using the Analyzer As a Fixed Tuned Receiver)

Demodulating AM Signals (Using the Analyzer As a Fixed Tuned Receiver)

The zero span mode can be used to recover amplitude modulation on a carrier signal. The analyzer operates as a fixed-tuned receiver in zero span to provide time domain measurements.

Center frequency in the swept-tuned mode becomes the tuned frequency in zero span. The horizontal axis of the screen becomes calibrated in time only, rather than both frequency and time. Markers display amplitude and time values.

The following functions establish a clear display of the waveform:

•Trigger stabilizes the waveform trace on the display by triggering on the modulation envelope. If the modulation of the signal is stable, video trigger synchronizes the sweep with the demodulated waveform.

•Linear mode should be used in amplitude modulation (AM) measurements to avoid distortion caused by the logarithmic amplifier when demodulating signals.

•Sweep time adjusts the full sweep time from 5 ms to 2000 s. (20 µs to 2000 s if Option AYX is installed). The sweep time readout refers to the full 10-division graticule. Divide this value by 10 to determine sweep time per division.

•Resolution and video bandwidth are selected according to the signal bandwidth.

Each of the coupled function values remains at its current value when zero span is activated. Video bandwidth is coupled to resolution bandwidth. Sweep time is not coupled to any other function.

Refer to “Demodulating and Listening to an AM Signal” on page 88 for more information on signal demodulation.

To obtain an AM signal, you can either connect a source to the analyzer input and set the source for amplitude modulation, or connect an antenna to the analyzer input and tune to a commercial AM broadcast station.

Demodulating an AM Signal Example 1:

View the modulation waveform of an AM signal in the time domain.

1.Connect an RF signal source to the analyzer INPUT. For this example, an Agilent E4433B Signal Generator was used with the following settings:

a. RF Frequency 300 MHz

Chapter 1

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Agilent Technologies E7401A, E7405A, E7402A, E7404A, E7403A manual Demodulating an AM Signal Example
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E7402A, E7405A, E7404A, E7401A, E7403A specifications

Agilent Technologies, a leader in test and measurement solutions, offers a range of spectrum analyzers designed to meet the evolving demands of the electronics industry. The E7403A, E7401A, E7404A, E7405A, and E7402A are prominent models that embody advanced features and technologies, enhancing performance, accuracy, and user experience.

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