J-Test Measurement - Keysight U8903B User Manual

4 Audio Analyzer Measurement Functions

J-test measurement

Jitter in a digital system is defined as the variation in time between the periodic samples.
Jitter may occur during sampling process of the ADC and DAC and clock recovery process.
It can also appear in the data pattern of the digital interface link.
J-test is an AES3 test signal that is developed to simulate the worst case data jitter in the
digital signal and also to test the jitter susceptibility of the DAC. The J-test signal consists
of a test tone with a frequency at 1/4 of the sampling rate (Fs) and a jitter signal with a
frequency of 1/192 Fs. The J-test digital pattern to be transmitted is as follows:
C00000 C00000 400000 400000 x24
BFFFFF BFFFFF BFFFFF BFFFFF x24
The digital pattern will cause inter-symbol interference in the digital signal and stress the
DAC clock recovery subsystem. You can measure the DAC system jitter performance by
observing the analog output of the DAC in the FFT spectrum.
J-test measurement function mode is applicable for the analog analyzer only. The J-test
measurement is displayed as shown in Figure 4-42.
Figure 4-42
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Analog Analyzer > Functions > J-Test menu page
Keysight U8903B User's Guide