Jitter Calibration in ATE-to-DUT Communication Channels
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Solution Overview
Problem
The discrepancy in jitter between the test signal introduced by automatic test equipment (ATE) and the jitter experienced by the device under test (DUT) due to jitter introduced in the communication path affects the accuracy of testing, as the actual jitter at the DUT connection differs from the expected jitter.
Innovation Solution
A method and system for calibrating jitter in a communication channel by sampling test data at a point of connection between the ATE and DUT, determining the first amount of jitter, and processing it to remove effects of jitter introduced during sampling, using a latched comparator or D flip-flop, to determine the second amount of jitter experienced at the DUT connection, represented by equations J2=√(J12−J42−J52) or J2=√(J12−J42), which includes jitter from the sampling device and clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If jitter is added to the test signal by ATE, then the DUT's tolerance to jitter can be tested, but the jitter in the test signal at the DUT connection differs from the expected jitter due to jitter introduced in the communication path
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing the jitter introduced by the communication path before actual testing. The system performs a calibration process where test patterns are transmitted through the communication path and the introduced jitter is measured and stored. This pre-characterization allows the system to compensate for the communication path jitter during subsequent tests, ensuring accurate jitter tolerance assessment of the DUT.
Solution Approach 2:
The patent implements feedback by using the measured communication path jitter information to adjust and correct the expected jitter values. The system continuously monitors the actual jitter introduced by the communication path and uses this feedback to compensate for it in the test results. This feedback mechanism ensures that the DUT is tested with the intended jitter levels despite variations in the communication path.
2Measurement precision
If sampling is performed to measure jitter at the DUT connection, then jitter can be measured, but additional jitter is introduced by the sampling device and clock signal
Solution Approach 1:
The patent applies the taking out principle by separating and independently measuring the jitter introduced by the sampling device and clock signal. The system extracts these sampling-induced jitter components from the total measured jitter and removes them from the calculation. By isolating and eliminating these harmful factors, the system accurately determines the jitter that would be present at the DUT connection without the contaminating effect of sampling artifacts.
Solution Approach 2:
The patent converts the harmful sampling-induced jitter into a beneficial calibration reference. Instead of treating the sampling device and clock signal as sources of error to be minimized, the system deliberately measures their jitter contribution and uses this information to calibrate the measurement system. This calibration process transforms the previously harmful sampling jitter into a useful reference that enables accurate compensation and achieves precise jitter measurement at the DUT connection.
Data Source
AI summary
Calibrating jitter in a communication channel between test equipment and a connection for a device under test (DUT) includes sampling test data in the communication channel at about a point of the connection to produce sampled data, where the test data travels through the communication channel at a first rate, and where the test data is sampled at a second rate that is less than the first rate, determining a first amount of jitter in the sampled data relative to the test data, and determining a second amount of jitter at about the point of connection based on the first amount of jitter.