Transmit Power Control Loop for Envelope-Preserving RF Accuracy
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Solution Overview
Problem
Existing radio-frequency communication devices face challenges in accurately controlling transmitted power across a wide dynamic range, particularly in systems like WCDMA and LTE, where time-varying signal information and modulation formats can lead to errors and require complex calibration to maintain power step accuracy and account for temperature variations.
Innovation Solution
A mobile transmitter system incorporating an envelope extractor, error extractor, and feedforward multiplier to control transmitted power independently of data patterns, using a variable gain amplifier and multiple stages in the transmit chain, with a control loop that cancels modulation envelopes and adjusts power levels based on instantaneous signal representations and feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control loop bandwidth is increased to achieve fast response for maintaining average power step accuracy, then power control accuracy is improved, but signal envelope information is stripped introducing transmitted signal errors
Solution Approach 1:
The patent segments the power control loop into two distinct bandwidth modes: a fast response mode for maintaining average power step accuracy and a slow response mode for preserving signal envelope information. The system dynamically switches between these segmented modes based on operating conditions, allowing each segment to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent implements dynamic adjustment of control loop bandwidth by switching between pre-configured fast and slow response modes. This dynamic adaptation allows the system to optimize performance for different signal conditions and modulation formats, maintaining power accuracy when needed while preserving signal integrity during high peak-to-average ratio transmissions.
2Reliability
If the control loop bandwidth is decreased to preserve signal envelope information, then transmitted signal accuracy is improved, but power control response becomes too slow to maintain average power accuracy
Solution Approach 1:
The patent segments the power control loop into two distinct bandwidth modes: a fast response mode for maintaining average power step accuracy and a slow response mode for preserving signal envelope information. The system dynamically switches between these segmented modes based on operating conditions, allowing each segment to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent implements dynamic adjustment of control loop bandwidth by switching between pre-configured fast and slow response modes. This dynamic adaptation allows the system to optimize performance for different signal conditions and modulation formats, maintaining power accuracy when needed while preserving signal integrity during high peak-to-average ratio transmissions.
3Measurement precision
If a fast response control loop mode is used, then power control accuracy is improved, but error in transmitted power increases during modulation format changes or data pattern changes
Solution Approach 1:
The patent implements dynamic adjustment of control loop bandwidth by switching between pre-configured fast and slow response modes. This dynamic adaptation allows the system to optimize performance for different signal conditions and modulation formats, maintaining power accuracy when needed while preserving signal integrity during high peak-to-average ratio transmissions.
Solution Approach 2:
The patent employs feedback mechanisms that monitor signal conditions, modulation formats, and data patterns to determine when to switch between fast and slow response modes. This feedback-driven mode selection ensures the control loop adapts to changing transmission conditions, preventing power errors during modulation changes while maintaining accuracy during stable operation.
4Ease of operation
If conventional analog power control schemes with continuously variable gain elements are used, then transmitted power control is achieved, but device complexity and calibration requirements increase significantly
Solution Approach 1:
The patent replaces complex analog continuously variable gain elements with a digital control approach using a lookup table and digital-to-analog converter. This substitution eliminates the need for complex analog calibration while maintaining power control capability, significantly reducing device complexity and calibration requirements.
Solution Approach 2:
The patent changes the control mechanism from analog continuous adjustment to digital discrete steps based on a lookup table. This parameter change simplifies the control architecture by replacing multiple continuously variable gain elements with a single digital control system that achieves the same power control function with reduced complexity.
Data Source
AI summary
Apparatus and methods for transmit power control in wireless communication systems are provided. In one aspect, a wireless communication system includes a transmit chain that generates a transmit signal based on a data signal having a time-varying signal envelope, a power amplifier that amplifies the transmit signal, and a transmit chain controller that generates a first power control signal and a second power control signal that control an adjustable power level of the transmit chain. The transmit chain controller includes an error extractor that generates an error signal based on comparing an output signal power of the power amplifier to the time-varying signal envelope. The transmit chain controller further includes a control signal generator that generates the first power control signal and an adjustment signal based on estimating the error signal, and that generates the second power control signal based on the error signal and the adjustment signal.