Transmitter PA Gain Tracking Using Feedback Signal Portions
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Solution Overview
Problem
Analog Power Amplifiers (PA) in transmitter circuits experience undesired gain variations due to physical phenomena like temperature changes, leading to inaccurate gain estimation and limited performance in digital radio transmitters and receivers, particularly in high-standard wireless systems like 802.11ax Wi-Fi, which requires low Error Vector Magnitude (EVM) for reliable communication.
Innovation Solution
Implementing a closed-loop transmitter gain tracking system using a transmitter Feedback Receiver (TX FBR) to feed back the transmit signal, determine gain relations between different signal portions, and adjust power to level out gain variations, thereby maintaining consistent signal quality and enabling relaxed RF design considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If analog Power Amplifier is used in transmitter circuit, then signal transmission capability is improved, but gain variation occurs due to temperature changes
Solution Approach 1:
The patent implements a feedback mechanism where the transmitted signal is fed back to the transmitter through a feedback receiver. The feedback signal is processed to determine gain variations, and compensation values are calculated and applied to correct these variations in real-time, thereby stabilizing the PA gain despite temperature changes.
Solution Approach 2:
The patent performs preliminary gain measurement using feedback signals before actual data transmission. By measuring the gain of different signal portions (preamble, data, pilot symbols) in advance and calculating compensation values, the system prepares correction factors that are then applied during transmission to prevent gain variation effects.
2Device complexity
If gain variation compensation is not implemented, then device complexity is reduced, but Error Vector Magnitude performance deteriorates
Solution Approach 1:
The transmitter performs self-diagnosis and self-correction by using its own transmitted signal as the feedback source. The system measures its own gain variations through the feedback receiver and automatically calculates and applies compensation values, eliminating the need for external calibration equipment or complex manual adjustment mechanisms.
Solution Approach 2:
The patent dynamically adjusts the transmit signal parameters (amplitude, power) based on measured gain variations. By changing these parameters in real-time according to the calculated compensation values, the system maintains consistent signal quality and achieves low EVM performance without requiring a completely redesign of the transmitter architecture.
Data Source
AI summary
The present disclosure relates to a transmitter for transmitting a transmit signal comprising a first signal portion and a second signal portion. The transmitter comprises a power amplifier configured to amplify the transmit signal. The power amplifier is prone to undesired gain variations during the first and the second signal portion. The transmitter further comprises a transmit feedback receiver coupled to an output of the power amplifier and configured to feed back the transmit signal to generate a fed back first signal portion and a fed back second signal portion. Processing circuitry is configured to determine a first gain relation between the fed back first signal portion and the first signal portion and to determine at least one second gain relation between the fed back second signal portion and the second signal portion. Power adjustment circuitry is configured to adjust a transmit power of the transmit signal according to a variation between the first gain relation and the second gain relation.