Asynchronous Impulse Response Measurement for Clocked Systems
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Solution Overview
Problem
Existing methods face challenges in accurately measuring the frequency response of a Device Under Test (DUT) due to slight differences in sampling rates between the DUT and the measurement system, leading to phase discrepancies and noise cancellation issues when averaging multiple measurements.
Innovation Solution
A method is introduced to determine and adjust for clock rate differences by generating an interrogation signal with two events spaced a known number of samples apart, measuring the shift, and applying adjustments to the sampling rate or the measured signal to align samples, preventing noise cancellation and allowing for effective noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple measurements are averaged to reduce noise, then noise reduction is improved, but phase discrepancies and comb filtering arise due to sampling rate differences
Solution Approach 1:
The patent applies preliminary action by measuring the clock rate difference between the DUT and measurement system before performing the frequency response measurement. An interrogation signal is played and recorded to determine the sample rate offset, which is then used to adjust the measurement signal timing. This preliminary measurement and adjustment prevents phase discrepancies from developing during the actual measurement process, enabling reliable averaging without comb filtering artifacts.
2Adaptability or versatility
If the sampling rates of DUT and measurement system are kept separate, then system independence is maintained, but sample rate variations cause phase drift and measurement errors
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the measurement signal timing based on the measured clock rate difference. The interrogation signal determines the actual sample rate offset, and this parameter information is used to modify the frequency response measurement signal timing. This allows the system to maintain independence while compensating for sampling rate variations through parameter adjustment, ensuring accurate frequency response measurements.
3Ease of operation
If a single measurement iteration is used, then measurement simplicity is maintained, but no noise reduction is achieved
Solution Approach 1:
The patent applies preliminary action by first measuring the clock rate difference using an interrogation signal before performing the actual frequency response measurement. This preliminary measurement enables the system to maintain simple single-iteration measurements while still achieving noise reduction through proper timing alignment. The pre-measured timing adjustment ensures that multiple measurements can be averaged effectively without complex real-time synchronization.
Data Source
AI summary
A method for measuring acoustic impulse response of a Device Under Test (DUT) addresses sample rate variations by determining clock rate differences between the DUT and test system, and making adjustments to compensate for the different clock rates. An interrogation signal is generated with two “events” spaced a known number of samples apart, at the nominal sampling rate of the DUT. The interrogation signal is played through the DUT and recorded by a measurement system. The number of samples between the two “events” is measured in the sampled signal to determine the shift introduced by the different clock rates. The adjustment is then applied to either the original frequency response measurement signal by adjusting the sampling rate of a frequency response measurement signal to compensate for the different clock rates, or to the measured signal before averaging, to align the samples and prevent cancelling.