Signal Distortion Measurement via Active Cancellation
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Solution Overview
Problem
Conventional methods for measuring distortion properties of electronic devices face challenges in achieving a wide dynamic range due to internal receiver distortion, which masks small distortion products and requires labor-intensive calibration with multiple filters and manual adjustments.
Innovation Solution
The system actively suppresses fundamental signals by injecting cancellation signals with adjustable magnitude and phase, allowing for deconstructive addition with the output signal to reduce receiver-generated distortion, thereby extending the dynamic range without the need for attenuators or delay lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If signal attenuation is applied to prevent overdriving the receiver, then large signals can be measured effectively, but the noise figure of the receiver degrades and small distortion products are masked in the noise floor
Solution Approach 1:
The invention applies preliminary anti-action by injecting cancellation signals that are 180 degrees out of phase with the fundamental signals before they enter the receiver. This pre-cancellation prevents the fundamental signals from overdriving the receiver, eliminating the need for attenuation while maintaining low noise figure. The cancellation signals are generated and adjusted to destructively interfere with the fundamental signals, allowing small distortion products to be measured above the noise floor.
2Measurement precision
If a low-noise amplifier (LNA) is added to decrease the noise figure, then small distortion products can be detected, but the LNA generates additional distortion
Solution Approach 1:
The invention applies preliminary anti-action by canceling fundamental signals before they enter the LNA. This prevents the LNA from being overdriven and generating distortion products. The cancellation signals are adjusted to destructively interfere with the fundamental signals, allowing the LNA to operate in its linear region and amplify both the remaining small distortion products and the cancellation signals without generating additional distortion.
3Adaptability or versatility
If multiple filters are used to measure signals over a range of frequencies, then frequency response can be compensated, but the calibration procedure becomes labor-intensive and prone to error
Solution Approach 1:
The invention applies universality by using a single receiver system with electronically controllable cancellation signals that can operate across a wide frequency range. The cancellation signal generation and adjustment mechanism works universally for different frequencies, eliminating the need for multiple frequency-specific filters. The system can be calibrated once and then measure distortion products across the entire frequency range by electronically adjusting the cancellation signal parameters.
4Measurement precision
If analog phase shifters and attenuators are used for signal cancellation, then fundamental signals can be suppressed, but manual adjustment is required and resolution is limited to several tenths of a decibel
Solution Approach 1:
The invention applies mechanics substitution by replacing manual analog phase shifters and attenuators with electronically controlled cancellation signal generation. The system uses digital signal processing and electronic phase control to adjust the magnitude and phase of cancellation signals, eliminating the need for manual mechanical adjustments. This provides continuous, high-resolution control of the cancellation signals with resolution much finer than several tenths of a decibel, and enables automated calibration and measurement procedures.
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 results in more accurate and faster measurements with improved sensitivity, reducing noise interference and the need for extensive calibration, enabling the detection of intermodulation distortion products without degrading the noise floor.
Implementation Method 1
inject a first cancellation signal generated by a first signal source into the output signal from the DUT, at least one of a first magnitude and a first phase of the first cancellation signal being adjustable for suppressing the first fundamental signal
Data Source
AI summary
A system has an extended dynamic range for measuring distortion in an output signal of a device under test (DUT), the output signal having at least a first fundamental signal. The system includes a first combiner and a test receiver. The first combiner is configured to inject a first cancellation signal generated by a first signal source into the output signal from the DUT, at least one of a first magnitude and a first phase of the first cancellation signal being adjustable for suppressing the first fundamental signal. The test receiver is configured to receive and measure the output signal having the suppressed first fundamental signal.