As with most timing specifications, special considerations must be taken when measuring phase noise. The primary issue is the noise floor capability of the measurement system. The noise floor can be defined as the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system. If the measurement system does not have the necessary noise-floor performance required by the device under test (DUT), the results will be inaccurate. The phase noise plot will track the noise floor of the equipment instead of the true performance of the DUT. In addition, all precautions must be taken to avoid any additional noises from coupling into the measurement system. Proper shielding must be in place to ensure an accurate measurement. Refer to application note AN-839 for more details. For other questions not addressed by the Knowledge Base, please submit a technical support request.
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