Transmitter Gain Calibration via Air-Coupled Loopback
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Solution Overview
Problem
Wireless communications devices face inconsistent performance due to manufacturing variations and temperature effects, particularly in quadrature amplitude modulation (QAM) 16 and higher constellations, leading to transmitter compression issues.
Innovation Solution
A calibration method using an air coupling between transmitter and receiver antennas to adjust the transmitter gain based on a loopback signal, ensuring the signal meets a target level to prevent compression, which involves transmitting a calibration signal, receiving a loopback signal, and iteratively adjusting the gain until the target is achieved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transmitter gain is increased to improve transmission power, then transmission distance is improved, but transmitter compression occurs causing signal distortion
Solution Approach 1:
The patent implements a feedback mechanism where the receiver captures the transmitted calibration signal through its antenna, processes the captured signal, and returns the captured signal as feedback to the transmitter. The transmitter then adjusts its gain based on this feedback to achieve optimal transmission power without compression. This closed-loop feedback system resolves the contradiction by continuously monitoring signal quality and adjusting power accordingly.
Solution Approach 2:
The patent changes the transmission parameter (gain) dynamically based on feedback information. The transmitter adjusts its gain setting in response to the captured signal characteristics, transforming a static transmission system into a dynamic one that adapts to prevent compression while maximizing transmission power. This parameter adjustment resolves the contradiction between power and signal quality.
2Reliability
If calibration signal gain is adjusted to meet target level, then transmitter compression is prevented, but calibration process complexity increases
Solution Approach 1:
The system performs self-calibration using its own transmitted signal captured by its own receiver antenna. The transmitter uses the receiver's capture of its own transmission to determine appropriate gain settings, eliminating the need for external calibration equipment or complex manual adjustment procedures. This self-service approach reduces operational complexity while ensuring reliable transmitter performance.
Solution Approach 2:
The calibration signal acts as an intermediary that carries information about transmitter performance characteristics. By injecting a known calibration signal and capturing it at the receiver, the system uses this intermediary signal to infer transmitter state and adjust gain accordingly, simplifying the calibration process while maintaining performance stability.
3Manufacturing precision
If manufacturing variations are compensated through calibration, then transmitter performance consistency is improved, but calibration time increases
Solution Approach 1:
The patent performs calibration actions before normal transmission operations begin. By establishing the correct gain settings during an initial calibration phase using the feedback mechanism, the transmitter is prepared for optimal performance during subsequent operations. This preliminary calibration action ensures consistency while minimizing time impact on actual transmission tasks.
Solution Approach 2:
The patent replaces complex manual calibration procedures with an automated electronic feedback system. Instead of requiring physical adjustment or complex measurement equipment, the system uses electronic signal capture and processing to automatically determine and adjust gain settings, significantly reducing calibration time while maintaining precision.
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 method improves performance by reducing the effects of temperature changes and manufacturing variations, ensuring stable transmission power and minimizing distortion, thereby enhancing the reliability of wireless communications.
Implementation Method 1
The receiver antenna is to receive wireless signals and provide the wireless signals to the receive path
Implementation Method 2
The transmit path is to communicate transmit signals to the transmitter antenna for wireless transmission
Data Source
AI summary
A calibration signal is transmitted from a transmitter antenna. A receiver antenna receives a loopback signal that results from an air coupling of the receiver antenna and the transmitter antenna. The loopback signal is compared to a target. If the loopback signal does not meet the target, then a gain of the calibration signal is adjusted and the loopback signal is again checked against the target. When the loopback signal meets the target, the gain is taken as a calibrated transmitter gain.