Network Analyzer Compensation for Nonlinear RF Compression
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Solution Overview
Problem
Network analyzers compress incident RF signals nonlinearly, leading to distorted measurements due to nonlinear relationships between power levels and phases of reflected signals, necessitating a compensation method to maintain linear relationships.
Innovation Solution
A compensation module generates an algorithm based on nonlinear relationships between power levels and phases, using a frequency-dependent expansion operator to convert these relationships to linear ones, minimizing residual errors through a least-squares-error fit of a polynomial Volterra model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the network analyzer measures RF signals directly, then the measurement process is simple, but the power levels and phases become nonlinear due to compression
Solution Approach 1:
The patent applies preliminary action by pre-characterizing the nonlinear compression behavior of the measurement receiver through calibration measurements. The system stores compression characteristics (nonlinear relationships between incident and reflected signal power levels and phases) before actual measurements, then uses these pre-determined characteristics to compensate for nonlinearity during operation, maintaining measurement linearity without changing the basic measurement process
Solution Approach 2:
The patent implements feedback by using the stored nonlinear compression characteristics to adjust and correct the measured reflected signal. The system compares the actual measurement against the pre-characterized nonlinear behavior and applies compensation based on this feedback, ensuring that the final measurement results maintain linear relationships between power levels and phases despite the receiver's compression
2Power
If the network analyzer uses a measurement receiver with high power handling, then the dynamic range increases, but nonlinear compression occurs at lower power levels
Solution Approach 1:
The patent applies parameter changes by storing the nonlinear compression characteristics of the measurement receiver across different power levels, frequencies, and device under test conditions. The system selects and applies the appropriate compression characteristics based on the current operating parameters, allowing the measurement receiver to handle high power levels while maintaining measurement linearity through parameter-based compensation
Data Source
AI summary
A method for compensating for compression of radio frequency (RF) signals by a network analyzer includes receiving a set of measured values for test input signals to a reference receiver of a network analyzer and corresponding test output signals from a measurement receiver of the network analyzer, the test input signals comprising signals with various powers and frequencies. A compensation algorithm is generated based on a nonlinear relationship between power levels of the test output signals and the test input signals and a nonlinear relationship between phases of the test output signals and the test input signals that is configured to convert the nonlinear relationships to linear relationships. The compensation algorithm is applied to subsequent output signals from the measurement receiver.