EVM Measurement Correction via Lookup Table Mapping
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Solution Overview
Problem
Error vector magnitude (EVM) measurements in test systems are often corrupted by radio frequency (RF) noise and symbol decoding errors, leading to inaccurate assessments of device performance, particularly in quadrature amplitude modulation (QAM) systems.
Innovation Solution
A method is developed to generate a mapping function that relates first EVMs corrupted by RF noise to second EVMs corrupted by both RF noise and symbol decoding errors, using a simulation to determine theoretical and simulation EVMs, and storing this mapping function in a constellation decoder to correct symbol decoding errors in EVM measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EVM measurements are performed using conventional methods, then the measurement process is simple and fast, but the measurement accuracy is degraded due to RF noise and symbol decoding errors
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing mapping relationships between theoretical EVM values and measured EVM values (corrupted by noise and decoding errors) in a lookup table during system initialization or offline processing. This pre-computed mapping data is then used during actual measurements to correct errors without adding real-time computational complexity, thus improving accuracy while maintaining system simplicity
Solution Approach 2:
The patent introduces an intermediary mapping function (lookup table) that mediates between the raw measured EVM values and the corrected theoretical EVM values. This intermediary structure translates corrupted measurements into accurate results by referencing pre-established relationships, effectively separating the complexity of error correction from the measurement process
2Measurement precision
If symbol decoding errors are corrected in real-time, then measurement accuracy improves, but processing time and computational complexity increase
Solution Approach 1:
The patent performs the computationally intensive error correction calculations in advance during system setup or offline processing, storing the results in a lookup table. During actual real-time measurements, the system simply queries this pre-computed table, reducing processing time from complex calculations to simple table lookups, thus maintaining high accuracy while minimizing time loss
Solution Approach 2:
The patent creates a copy of the error correction mapping relationships in a lookup table structure that can be quickly accessed during measurements. Instead of performing full error correction computations during each measurement, the system uses this pre-created copy of correction data, significantly reducing processing time while preserving correction accuracy
Data Source
AI summary
An example test system includes memory (e.g., one or more memory devices) storing (i) instructions that are executable, and (ii) a mapping function that relates first error vector magnitudes (EVMs) for first symbols to second EVMs for the first symbols, where the first EVMs are corrupted by radio frequency (RF) noise and the second EVMs are corrupted by both RF noise and symbol decoding errors. The test system also includes a decoder to receive a signal from a device under test, and to obtain a third EVM for a second symbol that is based on the signal, where the third EVM is corrupted by both RF noise and a symbol decoding error. One or more processing devices are configured to execute the instructions to adjust the third EVM using the mapping function to correct the symbol decoding error in the third EVM.