Remote Frequency Response Measurement Using Frequency Compression
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Solution Overview
Problem
Conventional test instruments face challenges in accurately measuring properties of devices under test (DUTs) with large bandwidth signals or those difficult to access, such as long coaxial cables or MIMO antenna arrays, due to bandwidth limitations and the need for expensive high-speed oscilloscopes and synchronized network analyzers.
Innovation Solution
A system and method using a repetitive stimulus signal with a multi-tone or multi-pulse local oscillator to generate a frequency-compressed signal, allowing for digitization and Fourier transformation to determine DUT properties without requiring separate measurement of individual frequency components, enabling efficient measurement of S-parameters and other properties across a wide frequency range without the need for synchronized oscillators or extensive cabling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sampling oscilloscope is used to measure high bandwidth signals, then the bandwidth limitation problem is circumvented, but the signal-to-noise ratio deteriorates due to insufficient energy extraction
Solution Approach 1:
The patent employs periodic sweeping of the local oscillator frequency across the signal bandwidth, repeatedly measuring the same signal multiple times. This periodic action accumulates energy from the signal across many measurement cycles, significantly improving the signal-to-noise ratio while maintaining the ability to measure high bandwidth signals that exceed the oscilloscope's instantaneous bandwidth capability.
Solution Approach 2:
The patent introduces a local oscillator as an intermediary element that mixes with the input signal to downconvert it to a lower intermediate frequency. This intermediary approach enables the measurement of high-frequency signals using lower-bandwidth oscilloscope equipment, while the repeated mixing and measurement process accumulates sufficient signal energy to overcome noise.
2Measurement precision
If two network analyzers are used to measure S21 of a long cable, then amplitude measurement becomes possible, but phase measurement remains impossible due to unpredictable phase variation
Solution Approach 1:
The patent uses a local oscillator as an intermediary to mix with the signal and downconvert it to a lower frequency where the oscilloscope can accurately measure both amplitude and phase. The local oscillator provides a stable reference that enables coherent detection, preserving phase information that would otherwise be lost in direct high-frequency measurements.
Solution Approach 2:
The patent employs periodic sweeping of the local oscillator frequency and repeated measurements to accumulate signal energy and extract both amplitude and phase information. By performing multiple measurements at different frequency points and combining the results, the system recovers complete complex S-parameters including phase, overcoming the limitations of single-shot measurements.
3Ease of operation
If conventional test instruments are used to measure long or hard-to-access DUTs, then transmission measurements become difficult, but the device complexity and cabling requirements increase
Solution Approach 1:
The patent introduces a local oscillator and mixing stage as intermediaries that enable measurement of distant or difficult-to-access devices using a single test instrument. The local oscillator can be positioned near the device under test, mixing the signal locally and converting it to a frequency suitable for transmission back to the oscilloscope, eliminating the need for complex synchronized multi-instrument setups or extensive cabling.
Solution Approach 2:
The patent creates a frequency-translated copy of the high-frequency signal at a lower intermediate frequency that can be easily transmitted and measured. This copied signal contains all the essential information (amplitude, phase, frequency characteristics) of the original high-frequency signal, enabling accurate remote measurement without requiring the oscilloscope to have the full bandwidth capability to handle the original high-frequency signal directly.
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 significantly reduces measurement time and cost, allowing for accurate determination of DUT properties at high frequencies with lower-cost equipment and eliminates the need for synchronized clocks, making it suitable for long or hard-to-access DUTs.
Implementation Method 1
a sinusoidal local oscillator signal is used to extract energy from the signal
Data Source
AI summary
A system for measuring a property of a device under test (DUT) includes a stimulus signal generator and a receiver. The stimulus signal generator generates a repetitive stimulus signal under control of a first clock, and provides the stimulus signal to an input port of the DUT. The receiver receives an input signal output from the DUT, the input signal being based on the stimulus signal provided to the input port of the DUT. The receiver includes a second clock syntonized with the first clock, a memory that stores a calibration measurement of a calibration stimulus signal provided to the receiver during a calibration period without the DUT being connected to the stimulus signal generator, and a data processor configured to determine the property of the DUT by comparing the stored calibration measurement with a measurement of the input signal from the DUT performed under control of the second clock.