N9063C Analog Demodulation, X-Series Measurement Application

Keysight Technologies

Analog Demodulation

X-Series Measurement Application

N9063C

Technical Overview

• Perform one-button measurements for AM, FM, PM and FM stereo signals with multitouch user interface for the UXA signal analyzer
• Quad view, simultaneously displays RF spectrum, demodulated waveform, AF spectrum, demodulation metrics, and transient events such as attack/release time
• Analyze FM stereo signals for MPX, mono, stereo, channel characterization, and RDS/ RBDS decoding
• Use hardkey/softkey manual user interface or SCPI remote user interface
• Extend test assets with transportable licenses
• Smooth migration from 8901A/B modulation analyzers

Analog Demodulation Measurement Application

The analog demodulation measurement application transforms the N9040B UXA signal analyzer into an easy-to use transmitter tester for analog modulated signals, including AM, FM, PM, and FM stereo. By adding fast, one-button measurements, the analog demodulation measurement application helps you design, evaluate, and manufacture your analog devices quickly and accurately. Even in the modern digital world, the analog demodulation measurement application helps you to troubleshoot distortions due to unintentional, analog modulation from digitally-modulated transmitters -- allowing you to stay on the leading edge of your design and manufacturing challenges.

X-Series measurement applications

X-Series measurement applications increase the capability and functionality of Keysight signal analyzers to speed time to insight. They provide essential measurements for specific tasks in general-purpose, cellular communications, wireless connectivity and digital video applications, covering more than 40 standards or modulation types. Applications are supported on both benchtop and modular, with the only difference being the level of performance achieved by the hardware you select.

Top Features

Monitor RF spectrum

This is the most traditional spectrum analyzer measurement viewing the modulated carrier signal power in frequency domain. Prior to being modulated, the signal power of a sinusoidal carrier concentrates at the carrier frequency. By contrast, modulation causes sidebands indicating the power redistribution over frequencies. The pattern of the sidebands depends upon the modulation format. (Refer to Figure 2.)

Demod waveform and AF spectrum

This measurement retrieves the baseband signal from the modulated signal via the demodulation process, and displays the baseband signal in a pattern of modulation depth/deviation versus time. Because the modulation depth/deviation is directly proportional to the instantaneous amplitude of the baseband signal, the measurement result helps to intuitively evaluate the quality of the baseband signal. (Refer to Figure 3.)

AF spectrum view

By applying the fast Fourier transform (FFT) to the baseband waveform, AF spectrum demonstrates the baseband signal behaviors in frequency domain graphically. This measurement reveals the distortion of the baseband signal clearly just as the RF spectrum does for the RF signal. (Refer to Figure 4.)

Modulation metrics

Besides the frequency domain and time domain view of analog modulation signals, one of the most important features of this application is numeric result that demonstrates the modulation parameters and error information. For AM signal, the AM depth, modulation rate and distortions like SINAD will be displayed in metrics view; for FM/PM signal, the FM deviation/ PM deviation, carrier frequency error and distortions will be displayed. (Refer to Figure 4.)

Post-demod filters

The post-demod filters help you to optimize the measurement results by filtering out undesired signals such as harmonics, noise, and spurs from the demodulated signal. You may choose a high-pass filter (20, 50, 300, or 400 Hz), and/or a lowpass filter (300 Hz or 3, 15, 30, 80, 100, 300 kHz, or any other user defined) from the available post-demod filter bank to achieve the best demodulation results. (Refer to Figure 5.) For example, applying an appropriate low-pass filter helps minimize overshoot from square-wave modulation, such as frequency shift keying (FSK).

Additionally, a CCITT filter, which simulates the frequency response behavior of the human auditory system, is also available to help you evaluate the consequences of distortion of the demodulated signal from the human hearing perspectives. The filter bank also allows you to select from various other filters to optimize your measurements and comply with certain regulatory standards. These filters include:

• A-weighte
• C-weighted
• C-message
• CCIR-1k weighted
• CCIR-2k weighted
• CCIR unweighted
• SIAND notch
• Signaling notch filters

To accommodate your pre-emphasized FM signals, the N9063C is also equipped with four separate de-emphasis filters (25, 50, 75, and 750 μs) for you to select from.