Residual Phase Noise Measurement Using Common Reference Clock
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Solution Overview
Problem
Frequency converters, particularly those using mixers, introduce phase noise in output signals, and existing measurement systems struggle to accurately determine residual phase noise due to external noise sources and lack of synchronization among test equipment components.
Innovation Solution
A test system utilizing a common reference clock signal for RF signal sources and an analog-to-digital converter, employing direct digital synthesis or phased locked loops, synchronizes operations to isolate and measure residual phase noise effectively, reducing system phase noise floor by canceling out correlated noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If test equipment is used to measure residual phase noise, then external noise sources are canceled, but the test equipment itself becomes a source of phase noise that complicates measurement
Solution Approach 1:
The patent extracts and removes the test equipment phase noise contribution from the total measured phase noise. By measuring the phase noise of the test equipment separately (without the device under test) and subtracting it from the total measurement, the patent isolates and eliminates the harmful phase noise contribution from the measurement system itself, leaving only the residual phase noise from the device under test.
Solution Approach 2:
The patent applies preliminary anti-action by pre-measuring the phase noise characteristics of the test equipment before using it to measure the device under test. This preliminary measurement allows the system to compensate for and counteract the test equipment's phase noise contribution during the actual measurement process, preventing it from degrading the measurement accuracy.
2Adaptability or versatility
If frequency mixer is used to combine signals, then frequency conversion is achieved, but phase noise is introduced in the output signal
Solution Approach 1:
The patent converts the harmful phase noise effect into a beneficial measurement opportunity. By using the frequency mixer to combine the device under test signal with a reference signal, the patent transforms the phase noise problem into a measurable beat frequency signal. The phase noise manifests as frequency deviations in the mixed output, which can then be precisely measured and characterized using standard frequency measurement techniques.
Data Source
AI summary
Residual noise of a frequency mixer is detected. A reference clock is used to generate a first radio frequency (RF) signal, a second RF signal and a third RF signal. The first RF signal and the second RF signal serve as input to the frequency mixer. The reference clock is used to generate a third RF signal. The reference clock is also used to control timing in a detector device. A second frequency mixer mixes an output of the DUT with the third RF signal to produce an input signal for a detector device. Mixing the output of the DUT with the third RF signal cancels at least some of the phase noise within the output signal of the DUT that results from phase noise in the first RF signal and from phase noise in the second RF signal. The detector device detects residual phase noise existing within the input signal for the detector device.