Radio Transmitter Calibration via Open-Loop Control
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Solution Overview
Problem
Mobile radio transmitters face challenges in achieving high accuracy, fast switching, and avoiding adjacent channel interference, particularly due to sensitivity to antenna mismatches which can lead to high power consumption and potential damage, especially in mass production where radio power amplifier properties vary significantly.
Innovation Solution
A method for calibrating radio transmitters involves measuring forward and backward path characteristic quantities of the transmitter control loop, allowing for digital control adjustments to improve stability and homogeneity, even in marginal amplifier distributions, by using open-loop measurements to determine calibration values for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmitter is designed for high accuracy and fast switching, then transmission performance is improved, but sensitivity to antenna mismatch increases leading to high power consumption and potential damage
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before normal transmission operation. The calibration process pre-determines the relationship between control voltage and output power for each specific power amplifier, storing these characteristics for later use. This preliminary characterization allows the transmitter to operate efficiently during normal use without repeatedly measuring and adjusting, thus achieving high accuracy while avoiding the power consumption and damage risks associated with real-time adjustments under mismatch conditions
Solution Approach 2:
The patent implements self-service through the calibration process that automatically characterizes each power amplifier's unique properties and stores this information for self-adjustment during operation. The system uses its own resources (measurement capabilities and control mechanisms) to pre-determine optimal operating parameters, enabling the transmitter to adapt to individual amplifier variations without external intervention during normal operation, thereby maintaining high accuracy while minimizing power consumption
2Ease of operation
If analogue control is used for constant envelope modulation, then control simplicity is improved, but it becomes unsuitable for modulation with changing envelope such as 8PSK
Solution Approach 1:
The patent applies mechanics substitution by replacing the analogue control system with a digital control system. Instead of using continuous analogue voltage control that works only for constant envelope modulation, the invention uses digital signal processing and lookup tables stored in memory to control the power amplifier. This digital approach maintains control simplicity through programmed operations while achieving versatility by being able to handle various modulation types including 8PSK with changing envelopes, as the digital system can adapt its control strategy based on the specific modulation requirements
3Adaptability or versatility
If digital control architecture is used for 8PSK modulation, then modulation compatibility is improved, but calibration complexity increases due to need for precise control loop characterization
Solution Approach 1:
The patent applies segmentation by dividing the calibration process into distinct, manageable steps: first measuring the power amplifier's output characteristics at various control voltages, then storing these measurements in lookup tables, and finally using these pre-computed tables for actual transmission control. This segmented approach breaks down the complex calibration task into separate measurement, storage, and application phases, making the overall process more manageable and systematic while maintaining the digital control architecture's ability to handle 8PSK and other modulation types
Data Source
AI summary
In an embodiment, a radio transmitter may be provided. The radio transmitter may include a radio transmitter control loop; and a controller configured in such a way that it operates the radio transmitter control loop as a closed control loop in a first operating mode, and that it operates the radio transmitter control loop as an open control loop in a second operating mode.