Agilent Technologies E7405A, E7402A Demodulating FM Signals, Demodulating a FM Signal Example

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Making Basic Measurements

Demodulating FM Signals

Demodulating FM Signals

As with amplitude modulation (see page 59) you can utilize zero span to demodulate an FM signal. However, unlike the AM case, you cannot simply tune to the carrier frequency and widen the resolution bandwidth. The reason is that the envelope detector in the analyzer responds only to amplitude variations, and there is no change in amplitude if the frequency changes of the FM signal are limited to the flat part of the resolution bandwidth.

On the other hand, if you tune the analyzer slightly away from the carrier, you can utilize slope detection to demodulate the signal by performing the following steps.

1.Determine the correct resolution bandwidth.

2.Find the center of the linear portion of the filter skirt (either side).

3.Tune the analyzer to put the center point at mid screen of the display.

4.Select zero span.

The demodulated signal is now displayed; the frequency changes have been translated into amplitude changes., see Figure 1-58. To listen to the signal, turn on AM demodulation and the speaker.

In this example you will demodulate a broadcast FM signal that has a specified 75 kHz peak deviation.

Demodulating a FM Signal Example:

Determine the correct resolution bandwidth. With a peak deviation of

75kHz, your signal has a peak-to-peak excursion of 150 kHz. So we must find a resolution bandwidth filter with a skirt that is reasonably linear over that frequency range.

1.Perform a factory preset by pressing Preset, Factory Preset (if present).

2.Turn on the internal 50 MHz reference signal of the analyzer as follows:

•For the E7401A, use the internal 50 MHz amplitude reference signal of the analyzer as the signal being measured. Press

Input/Output, Amptd Ref (On).

•For all other models connect a cable between the front-panel AMPTD REF OUT to the analyzer INPUT, then press

Input/Output, Amptd Ref Out (On).

3.Set the center frequency to 50 MHz by pressing FREQUENCY,

Center Freq, 50, MHz.

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Contents Signal Analysis Measurement Guide Safety Information Warranty Limitation of Warranty Contents Demodulating and Listening to an AM Signal Making Basic Measurements What is in This Chapter Test Equipment Test Equipment Specifications Recommended ModelSignal Comparison Example Comparing SignalsPlacing a Marker on the 10 MHz Signal Using the Marker Delta Function Frequency and Amplitude Difference Between Signals Resolving Signals of Equal Amplitude Press SPAN, 2, MHz to bring the signal to center screen Resolving Signals ExampleUnresolved Signals of Equal Amplitude Or linked to the center frequency Resolving Small Signals Hidden by Large Set one source to 300 MHz at − 10 dBm 10 Signal Resolution with a 10 kHz Resolution Bandwidth 12 Signal Resolution with a 30 kHz Resolution Bandwidth Better Frequency Measurement Example Making Better Frequency Measurements13 Using Marker Counter Decreasing the Frequency Span Example Decreasing the Frequency Span Around the Signal14 Detected Signal 16 After Zooming In on the Signal Tracking Signal Drift Example Tracking Drifting Signals17 Signal With Default Span 19 Signal With 500 kHz Span 21 Using Signal Tracking to Track a Drifting Signal 22 Signal With Default Span 24 Signal With 500 KHz Span 25 Viewing a Drifting Signal With Max Hold and Clear Write Measuring Low Level Signals Example Measuring Low Level Signals26 Low-Level Signal 28 Using 0 dB Attenuation 29 Decreasing Resolution Bandwidth 30 30 kHz Video Bandwidth 31 Decreasing Video Bandwidth 32 Without Video Averaging 33 Using the Video Averaging Function Identifying Analyzer Generated Distortion Example Identifying Distortion ProductsDistortion from the Analyzer 34 Harmonic Distortion 36 RF Attenuation of 10 dB Identifying TOI Distortion Example Third-Order Intermodulation Distortion38 Third-Order Intermodulation Equipment Setup 39 Measuring the Distortion Product 40 Measuring the Distortion Product Signal-to-Noise Measurement Example Measuring Signal-to-Noise= 70 dB/Hz + 10 × log 30 kHz = -25.23 dB ⁄ 30 kHz Noise Measurement Example Making Noise Measurements42 Setting the Attenuation 43 Activating the Noise Marker 45 Increased Resolution Bandwidth 46 Noise Marker in Signal Skirt MHz 48 Viewing Power Between Markers 49 Measuring the Power in the Span Demodulating an AM Signal Example 50 Viewing an AM Signal 51 Measuring Modulation In Zero Span 52 Measuring Modulation In Zero Span 54 Measuring Time Parameters 55 Continuous Demodulation of an AM Signal Demodulating a FM Signal Example Demodulating FM Signals56 Establishing the Offset Point 57 Determining the Offset Demodulate the FM Signal 58 Demodulating a Broadcast Signal Making Complex Measurements Required Test Equipment What’s in This ChapterMaking Stimulus Response Measurements Using An Analyzer With a Tracking GeneratorWhat Are Stimulus Response Measurements? Stepping Through a Transmission MeasurementTransmission Measurement Test Setup Tracking Generator Output Power Activated Decrease the Resolution Bandwidth to Improve Sensitivity Measure the Rejection Range Measuring Device Bandwidth Tracking Generator Unleveled ConditionExample DB Bandwidth Measurement at -3 dB N dB Bandwidth Measurement at -60 dB Measuring Stop Band Attenuation Using Log SweepScale Type Log Tracking Generator Output Power Activated in Log Sweep 10 Normalized Trace After Reconnecting DUT 12 Minimum Stop Band Attenuation Example Making a Reflection Calibration MeasurementReflection Calibration 14 Short Circuit Normalized Measuring the Return LossVswr Demodulating and Listening to an AM Signal Example Demodulating and Listening to an AM SignalNext Pk Right, or Next Pk Left Sweep Time, 5, s 17 Continuous Demodulation of an AM Signal Demodulating and Listening to an AM Signal

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.

The E7403A is recognized for its high-quality performance and wide frequency range. This model offers frequency coverage from 9 kHz to 3 GHz, making it suitable for both commercial and academic research applications. With a phase noise of -100 dBc/Hz at 10 kHz offset, it delivers exceptional sensitivity. The E7403A also features a built-in tracking generator, facilitating effective signal generation for testing.

Next in line, the E7401A provides similar frequency coverage but is optimized for portable functionality. Weighing significantly less than its counterparts, it is easy to transport, making it ideal for field applications. Users benefit from its fast sweep speed of up to 3 GHz, which is crucial in quickly identifying and analyzing signals.

The E7404A excels in its comprehensive analysis capabilities. With a frequency range extending up to 6 GHz, it supports more demanding applications, including wireless communications and satellite technology. Its advanced digital signal processing capabilities enable the analysis of complex modulated signals, providing engineers with the data needed to troubleshoot and optimize system performance.

The E7405A is a highly versatile model that offers frequency coverage from 9 kHz to 20 GHz. This wide frequency range, combined with high dynamic range, supports the testing of various electronic devices and systems. It features advanced measurement options including occupied bandwidth, adjacent channel power, and sensitivity measurements, which are critical for compliance testing in communication systems.

Lastly, the E7402A is designed for users who require a spectrum analyzer with enhanced functionality at a competitive price. It reaches frequencies of up to 1.5 GHz, making it suitable for various applications including RF design, development, and manufacturing. Its user-friendly interface ensures that both novice and experienced users can navigate its features with ease.

In conclusion, Agilent Technologies' E7403A, E7401A, E7404A, E7405A, and E7402A spectrum analyzers provide a robust set of features tailored to meet diverse industry needs. Utilizing sophisticated technologies, these models ensure precise and efficient signal analysis, making them indispensable tools for engineers and researchers in the fast-paced world of electronics.
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