RF Control Circuit for Power Amplifier Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Advanced wireless communication systems require higher linearity in power amplifiers (PAs) to maintain signal quality, but existing semiconductor components like LDMOS, GaN, and GaAs struggle to meet these demands, leading to performance degradation due to bias current drift and nonlinearity issues.
Innovation Solution
A radio frequency (RF) control circuit that uses digital pre-distortion (DPD) and continuously adjusts bias voltage based on PA signatures to maintain linearity, detecting and correcting performance deviations in real-time, thereby enhancing PA performance without the need for extensive calibration or compensation tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation and coding schemes are introduced to pack more data bits into a signal symbol, then data rate is improved, but linearity requirements of the power amplifier become tighter and more difficult to meet
Solution Approach 1:
The patent applies digital pre-distortion (DPD) to the input signal before it reaches the power amplifier. The DPD circuit pre-compensates for the nonlinearity of the PA by introducing an opposite distortion pattern, so that when the signal passes through the PA, the overall system achieves linear output. This preliminary action eliminates the need for extremely high raw linearity in the PA itself while still achieving the tight linearity requirements needed for higher order modulation schemes.
Solution Approach 2:
The patent introduces an intermediary DPD circuit between the signal source and the power amplifier. This intermediary component handles the linearity compensation function, allowing the PA to operate with relaxed raw linearity requirements while still meeting the overall system linearity requirements for high data rate transmission.
2Reliability
If raw linearity of semiconductor components is increased to meet linearity requirements, then PA performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical approach of using extremely high raw linearity semiconductor components with a digital signal processing approach. Instead of relying on the physical linearity of the PA hardware, the system uses digital pre-distortion to compensate for nonlinearity, achieving PA performance without requiring complex, high-linearity semiconductor components.
Solution Approach 2:
The patent changes the operating parameters of the power amplifier dynamically through digital control. By adjusting the pre-distortion coefficients and monitoring PA performance, the system optimizes PA operation without requiring the PA hardware itself to be extremely complex or expensive.
3Reliability
If power amplifier output power is increased to maintain sufficient energy per bit and signal-to-noise ratio, then communication reliability is improved, but linearity performance becomes more difficult to maintain
Solution Approach 1:
The patent applies digital pre-distortion to compensate for the nonlinearity introduced when the power amplifier operates at high output power. The DPD circuit pre-adjusts the signal characteristics so that even though the PA is operating at high power levels, the overall system maintains linear performance, ensuring both high communication reliability and acceptable linearity.
4Manufacturing precision
If digital pre-distortion is applied to compensate for PA nonlinearity, then linearity is improved, but device complexity increases due to additional control circuitry
Solution Approach 1:
The patent designs the control circuitry to perform multiple functions: it monitors PA performance, adjusts pre-distortion coefficients, and compensates for nonlinearity. By making the control circuitry multi-functional, the system achieves improved linearity without proportionally increasing complexity, as the same control hardware serves multiple purposes in the signal processing chain.
Data Source
AI summary
A radio frequency (RF) control circuit is provided. The RF control circuit includes power amplifier (PA) circuitry for amplifying an RF signal and control circuitry configured to improve linearity of the PA circuitry based on a PA signature(s) already available and utilized to perform digital pre-distortion (DPD) in the RF control circuit. In examples discussed herein, the control circuitry determines a performance deviation of the PA circuitry based on the PA signature and continuously adjusts a bias voltage(s) supplied to the PA circuitry until the performance deviation is reduced to a predetermined performance deviation threshold. By continuously monitoring the performance deviation based on the PA signature(s) and adjusting the bias voltage(s), the control circuitry can detect and correct an operation abnormality of the PA circuitry in a timely manner. As a result, it is possible to maintain linearity in the PA circuitry for enhanced PA performance.