RF Receiver Path Nonlinearity Testing with Scaled Signals
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Solution Overview
Problem
Current on-chip monitoring methods for RF devices, particularly in radar sensors for automotive applications, fail to accurately determine receiver nonlinearity due to hardware limitations such as restricted chip area, component process variation, and test circuit imperfections, which are exacerbated by low-resolution digital-to-analog converters leading to quantization noise and inherent nonlinearity in test signal generators.
Innovation Solution
A method involving the generation of multiple scaled versions of a test signal using scaling factors less than or equal to 1, followed by digital signal processing to separate impairments from the test signal generator's nonlinearity, allowing precise on-chip linearity testing through Fourier-transformed data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If low-resolution digital-to-analog converters are used in test signal generators to reduce chip area, then chip area is reduced, but quantization noise increases and measurement precision deteriorates
Solution Approach 1:
The test signal generation process is segmented into multiple independent measurements with different scaling factors. Instead of requiring a single high-precision measurement, the system performs N repeated measurements with scaled test signals, then combines them through Fourier transformation to extract nonlinearity characteristics. This segmentation allows low-resolution DACs to achieve effective high-precision measurements through statistical combination.
Solution Approach 2:
The system changes the scaling factor parameter across multiple measurements rather than relying on a single fixed-amplitude test signal. By varying the scaling factor and combining results through Fourier transformation, the system extracts nonlinearity information that would be obscured by quantization noise in single measurements, effectively overcoming the limitations of low-resolution DACs.
2Measurement precision
If test signal generators are designed with high linearity specifications to improve measurement accuracy, then measurement precision improves, but device complexity and chip area increase
Solution Approach 1:
The invention extracts the nonlinearity characteristic measurement from the test signal generator itself and relocates it to the receiver path evaluation. Instead of requiring the TSG to be highly linear, the system measures how the receiver path responds to scaled test signals and extracts nonlinearity information through Fourier transformation of the received signals, effectively separating the measurement function from the signal generation function.
Solution Approach 2:
The receiver path acts as an intermediary that processes multiple scaled versions of the test signal. By introducing this intermediary processing stage with Fourier transformation, the system can determine nonlinearity characteristics without requiring the TSG to have high linearity, as the transformation process separates the nonlinearity information from the test signal imperfections.
3Ease of manufacture
If conventional on-chip test circuitry is used for linearity monitoring, then ease of manufacture is maintained, but the test signal generator's inherent nonlinearity prevents accurate DUT nonlinearity identification
Solution Approach 1:
The system uses feedback through repeated measurements with different scaling factors. By measuring the receiver path response to multiple scaled test signals and combining the results through Fourier transformation, the system creates a feedback mechanism that cancels out the TSG's inherent nonlinearity and isolates the DUT's nonlinearity characteristics, enabling accurate measurement despite using simple on-chip test circuitry.
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
Enables accurate determination of nonlinearity characteristics like third-order intercept point and spurious free dynamic range, overcoming the limitations of conventional methods by using low-area-consuming test signal generators and separating system nonlinearity from test signal generation impairments.
Implementation Method 1
Fourier-transformed data are generated using at least a portion of the set of N×M digital samples
Data Source
AI summary
A method for determining a nonlinearity characteristic of a receiver path includes generating a set of N×M digital samples by repeating N times selecting an scaling factor from a set of N scaling factors, generating a version of a test signal, the version of the test signal corresponding to a test signal scaled by the respective scaling factor, processing the respective version of the test signal in at least a part of the receiver path to generate a respective processed signal, and storing M digital samples corresponding to the respective processed signal. Fourier-transformed data are generated using at least a portion of the set of N×M digital samples and a nonlinearity characteristic of the receiver path is determined based on the Fourier-transformed data.