Frequency Converter Phase Trace Normalization
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Solution Overview
Problem
Testing frequency converters with embedded local oscillators (LO) face challenges in making accurate phase and group delay measurements due to unknown or unstable LO frequencies, leading to phase drift and erroneous measurements when using a vector network analyzer (VNA).
Innovation Solution
The method involves normalizing the phase trace by selecting a constant phase point and averaging subsequent points, which reduces noise in the phase trace, especially when a large intermediate frequency (IF) bandwidth is used, and compensates for LO drift by adjusting the signal generator LO based on additional frequency measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large intermediate frequency bandwidth is used on the VNA to capture varying IF frequency due to LO drift, then the measurement can capture the full range of frequency variations, but the phase trace becomes noisy
Solution Approach 1:
The patent applies preliminary action by normalizing the phase trace before averaging. Specifically, a reference phase value is determined from the first sweep and used to normalize subsequent sweeps. This preprocessing step removes the effect of LO drift from the phase measurements, allowing the system to use large IF bandwidth for capturing frequency variations while maintaining low noise levels in the final averaged measurement.
2Measurement precision
If phase normalization and averaging is applied to reduce noise, then measurement precision improves, but the measurement process becomes more complex
Solution Approach 1:
The patent implements feedback by using the measured phase information from reference sweeps to correct subsequent measurement sweeps. The normalized phase values are fed back into the averaging process, where they are used to adjust and align the phase references of different sweeps. This feedback mechanism systematically reduces noise accumulation while maintaining a relatively simple implementation that builds upon standard VNA measurement capabilities.
Data Source
AI summary
A method is presented where the phase trace is offset for each sweep such that the first point is always at zero degrees. The resulting traces are then averaged. The average reduces the noise in the phase trace and results in a less noisy group delay trace.