OTA Chamber Model Predistortion for Signal Reflection Compensation
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Solution Overview
Problem
Over-the-air (OTA) chambers used for radio frequency signal testing suffer from signal distortion due to unwanted reflections and echoes, making it challenging to achieve accurate radio channel emulation, especially with limited budgets.
Innovation Solution
A method involving a calibration antenna and signal processing unit to measure and compensate for reflections and scattering within the OTA chamber by creating an OTA chamber model, which is then used to predistort the radio frequency transmission and cancel out unwanted interactions, allowing for more accurate radio channel emulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional OTA chamber structures (walls, cables, antenna stands) are used, then the chamber can be constructed with moderate budget, but signal reflections and echoes cause distortion to the emulated radio channel
Solution Approach 1:
The patent performs preliminary calibration measurements to characterize the chamber's reflection properties before actual testing. By pre-measuring the chamber model and storing it for later compensation, the system prepares in advance to counteract the harmful reflections, transforming the chamber from an uncontrolled environment into a characterized system that can be mathematically compensated.
Solution Approach 2:
The patent converts the harmful reflections into useful information by measuring them through calibration signals. The reflected signals, which were previously considered noise and distortion, are now captured and processed to create a chamber model that enables compensation. The harmful reflections become the basis for calculating compensation weights that cancel their adverse effects.
2Reliability
If an anechoic chamber is constructed to eliminate reflections, then signal distortion is reduced, but the cost and technical complexity increase significantly
Solution Approach 1:
The patent creates a digital copy (chamber model) of the physical chamber's reflection characteristics through calibration measurements. Instead of physically modifying the chamber to eliminate reflections, the system captures the reflection patterns and stores them as data. This digital replica enables software-based compensation, replacing the need for expensive physical anechoic structures with computational corrections.
Solution Approach 2:
The patent replaces the mechanical approach of using physical anechoic materials and structures with a signal processing approach. Instead of mechanically absorbing reflections with foam materials, the system uses digital signal processing to calculate and apply compensation weights that mathematically cancel the reflections, substituting mechanical solutions with electronic/software solutions.
3Reliability
If calibration measurements are performed to create chamber model, then reflection compensation is enabled, but measurement time and processing complexity increase
Solution Approach 1:
The calibration measurements are performed once in advance to characterize the chamber, and the resulting chamber model is stored for reuse. This preliminary action separates the time-consuming measurement phase from the actual testing phase, so that subsequent tests benefit from the pre-acquired chamber knowledge without repeating the lengthy calibration process.
Solution Approach 2:
The chamber model created through calibration serves multiple purposes: it characterizes the chamber's reflection properties, enables compensation calculation, and can be reused for different test scenarios. This universal model allows the same calibration data to support multiple different antenna configurations and test cases, amortizing the initial measurement time across many uses.
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 distortion-free radio channel emulation in OTA chambers with higher echo levels, improving the quality of testing without requiring an anechoic environment, thus making it more feasible and cost-effective.
Implementation Method 1
receiving, by the at least one calibration antenna, calibration transmission of the over-the-air antennas via interactions between the calibration transmission and structures associated with the over-the-air chamber
Implementation Method 2
un- wanted reflections cause distortion to the emulated radio channel
Implementation Method 3
measure and compensate for reflections and scattering within the OTA chamber
Implementation Method 4
predistort the radio frequency transmission and cancel out unwanted interactions
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A radio channel generator has a radio channel model predistorted on the basis of a predetermined chamber model (98). An emulator (118) receives the weights of the radio channel model predistorted on the basis of the chamber model (98). A transmitter (122) feeds a communication signal to the emulator (118). The emulator (118) weights the communication signal with the radio channel model predistorted on the basis of the chamber model (98). The over-the-air antennas (102-116) receive the weighted communication signal and transmit it to a device under test (300). The chamber model (98) is based on a simulation or a measurement. The chamber model (98) takes into account undesired interactions in the over-the-air chamber for cancelling them during the radio channel emulation.