S-Parameter Measurement Using Dispersion and Sideband Frequencies
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Solution Overview
Problem
Measuring S-parameters at high frequency ranges and in harsh environments is challenging due to laser phase noise and sensitivity of devices to environmental changes, making direct phase measurement difficult or impossible.
Innovation Solution
A system and method that generate a test signal with a carrier and multiple sideband frequencies, using optical sources and a square law detector to produce a signal with a carrier and sidebands, which allows for the detection of S-parameters and dispersion, and combines these measurements to provide enhanced characterization of electrical networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct phase measurement is performed at optical frequencies, then S-parameters can be measured, but laser phase noise makes measurement difficult or impossible
Solution Approach 1:
The patent introduces an intermediary approach by measuring dispersion (derivative of phase) instead of phase directly. The sideband frequencies act as intermediaries that are less sensitive to laser phase noise, allowing indirect determination of phase characteristics through the relationship between dispersion and phase.
Solution Approach 2:
The patent changes the measurement parameter from direct phase to dispersion (frequency derivative of phase). By measuring how phase changes with frequency rather than phase itself, the system avoids the direct impact of laser phase noise while still obtaining phase information through integration of dispersion measurements.
2Measurement precision
If S-parameters are measured in harsh environments, then device characterization is achieved, but environmental changes corrupt the phase measurements
Solution Approach 1:
The patent uses dispersion as an intermediary measurement that is more robust to environmental changes. Since dispersion is a local derivative measurement rather than an absolute phase measurement, it is less affected by environmental drifts, allowing accurate characterization even in harsh conditions.
Solution Approach 2:
The patent replaces direct phase measurement (mechanically sensitive) with dispersion measurement using sideband frequencies (optically more stable). This substitution moves from a measurement method vulnerable to environmental mechanical changes to one that is more stable against such disturbances.
3Reliability
If conventional S-parameter measurement methods are used, then measurement simplicity is maintained, but reliability decreases in challenging conditions
Solution Approach 1:
The patent merges S-parameter measurement with dispersion measurement into a single unified approach. By combining these measurements and using their mutual relationship, the system achieves higher reliability without proportionally increasing complexity, as both measurements are obtained simultaneously through the same sideband-based methodology.
Solution Approach 2:
The patent employs feedback by using the measured dispersion to correct and enhance the S-parameter measurements. The dispersion information provides feedback that compensates for measurement uncertainties, improving reliability while the computational feedback loop manages the overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more accurate and reliable measurement of S-parameters and dispersion, even in challenging conditions, by exploiting the relationship between S-parameters and dispersion, and using techniques like Kalman filtering to enhance measurement accuracy.
Implementation Method 1
a square law detection device configured to receive the combined modulated first optical signal and second optical signal and in response thereto to produce an electrical signal which includes a carrier as a beat frequency between the first frequency and the second frequency
Implementation Method 2
an electrical signal which includes a carrier as a beat frequency between the first frequency and the second frequency
Implementation Method 3
the first optical source is further configured for modulating the first optical signal; which further includes at least two sideband frequencies generated in response to the modulating of the first optical signal
Data Source
AI summary
A system includes a test signal generator generating a test signal having a carrier and at least two sidebands, and provides the test signal to a device under test (DUT). A plurality of couplers sense an incident signal, a reflected signal, and a transmitted signal for the DUT at corresponding test ports of the test system when the test signal is supplied to the DUT. A signal processing apparatus: detects S-parameters for the DUT from the carrier present in each of the incident signal, reflected signal, and transmitted signal for the device under test; measures a dispersion for the DUT at each of the test ports from the two sidebands present in the incident signal, reflected signal, and transmitted signal for the device under test using the two frequencies; and combines the detected S-parameters and the measured dispersions to output enhanced measurements of the S-parameters and the dispersions.