EDGE Polar Transmitter Amplitude Calibration Without Diode Compensation
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Solution Overview
Problem
Existing power amplifiers in portable communication devices face inefficiencies due to the use of linear power amplifiers, which consume more power and require inaccurate diode detector calibration affected by temperature and manufacturing variations, especially in non-constant amplitude output signals.
Innovation Solution
An amplitude calibration element comprising a linear driver, differential detector, and differential comparator is introduced to accurately calibrate the amplitude modulation portion of the signal, eliminating the need for diode detector compensation by generating a gain control signal to control the linear driver's gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear power amplifier is used for non-constant amplitude output, then amplitude modulation accuracy is improved, but power efficiency deteriorates
Solution Approach 1:
The invention segments the power amplifier into two distinct paths: a linear power amplifier for phase modulation and a non-linear power amplifier for amplitude modulation. This segmentation allows each amplifier to operate in its optimal mode, with the linear amplifier handling only phase changes and the non-linear amplifier handling amplitude changes, thereby resolving the contradiction between amplitude modulation accuracy and power efficiency
Solution Approach 2:
The invention introduces an intermediary amplitude modulation detector and control circuit that monitors the output of the non-linear power amplifier and adjusts its operation to maintain amplitude modulation accuracy. This intermediary component enables the non-linear amplifier to achieve accurate AM control without requiring linear operation, thus improving power efficiency while maintaining AM precision
2Use of energy by moving object
If a non-linear power amplifier is used with separate AM and PM feedback loops, then power efficiency is improved, but device complexity increases
Solution Approach 1:
The invention merges the amplitude modulation detection and control functions into a unified feedback mechanism that works specifically with the non-linear power amplifier. By combining these functions and tailoring them to the non-linear amplifier's characteristics, the system achieves efficient AM control without requiring the complex dual-loop architecture that would be needed for general applications, thus reducing overall device complexity while maintaining power efficiency
3Device complexity
If a diode detector is used for AM detection, then device complexity is reduced, but measurement precision deteriorates due to temperature and manufacturing variations
Solution Approach 1:
The invention implements a feedback mechanism where the output of the non-linear power amplifier is continuously monitored and fed back to adjust the amplitude modulation detection. This feedback loop compensates for temperature and manufacturing variations in real-time, maintaining high AM detection accuracy without requiring complex temperature compensation circuits or precision components, thus achieving measurement precision without proportionally increasing device complexity
Data Source
AI summary
An amplitude calibration element comprises a linear driver configured to receive the output of a modulator, the modulator output comprising a voltage signal having an amplitude modulated (AM) portion, a differential detector configured to receive an output of the linear driver and develop a differential signal corresponding to the AM portion, and a differential comparator configured to receive the output of the differential detector and a differential reference signal, the differential comparator configured to develop a gain control signal to control the gain of the linear driver.