Power Amplifier Output Correction Circuit for VSWR Stability
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Solution Overview
Problem
Varying Voltage Standing Wave Ratio (VSWR) due to environmental factors like a mobile terminal's antenna being placed near the body causes fluctuations in load impedance, leading to deviations in output power of the power amplifier, which affects battery life, quality of service, and increases the likelihood of dropped calls and peak current.
Innovation Solution
An all-digital output power correction circuit that adjusts the ramping signal based on the difference between detected and desired output power signals, incorporating time alignment, over current, and over voltage detection and correction to maintain target output power during transmit bursts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open loop power amplifiers are used, then device complexity is reduced, but output power stability deteriorates due to VSWR variations
Solution Approach 1:
The patent implements a feedback mechanism where the detected output power signal is fed back to the output power correction circuit. The circuit compares the detected output power with the desired output power and generates a corrected ramping signal to compensate for deviations caused by VSWR variations, thereby maintaining output power stability without requiring complex control circuitry.
Solution Approach 2:
The output power correction circuit automatically adjusts the ramping signal based on the detected output power and desired output power difference. The system self-corrects for VSWR-induced power variations through the integration circuitry that generates adjustment signals, eliminating the need for external manual calibration or complex control mechanisms.
2Stability of the object's composition
If output power correction is implemented, then output power stability is improved, but device complexity increases due to additional correction circuitry
Solution Approach 1:
The patent replaces complex analog power correction mechanisms with an all-digital output power correction circuit. The digital implementation uses digital signal processing to compare detected and desired output power signals, generating corrected ramping signals through logical operations and digital integration, thereby reducing hardware complexity while maintaining correction effectiveness.
Solution Approach 2:
The correction circuit dynamically adjusts the ramping signal parameters based on the detected output power deviations. By changing the magnitude and timing of the ramping signal in response to VSWR variations, the system maintains optimal output power without requiring fixed complex circuitry for all possible operating conditions.
3Device complexity
If VSWR variations are not corrected, then device complexity remains low, but reliability deteriorates due to dropped calls and peak current issues
Solution Approach 1:
The output power correction circuit performs preliminary adjustment of the ramping signal before the power amplifier generates the output power. By pre-correcting the ramping signal based on anticipated VSWR variations detected during the ramp-up phase, the system prevents power deviations before they occur, ensuring reliable operation and avoiding dropped calls or peak current conditions.
Solution Approach 2:
The correction circuit operates specifically during the critical ramp-up phase of the transmit burst, where VSWR variations have the most significant impact. By focusing correction efforts on this critical period rather than continuously adjusting during the entire transmit cycle, the system achieves reliable power control with minimal additional circuitry.
Data Source
AI summary
A system is provided for correcting an output power of a power amplifier in a transmit chain of a mobile terminal. In one embodiment, the system includes output power correction circuitry that corrects the output power of the power amplifier during ramp-up for a transmit burst. The output power of the power amplifier is controlled based on a power control signal, which is provided by combining an amplitude component of a modulated signal and a corrected ramping signal provided by the output power correction circuitry. In general, a power amplifier ramp generator provides a ramping signal. The ramping signal is converted to a desired output power signal, which is subtracted from a detected output power signal to provide an error signal. The error signal is integrated to provide an adjustment signal, which is combined with an ideal ramping signal to provide the corrected ramping signal.