Separate I and Q Power Amplifiers for Linearity
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Solution Overview
Problem
Mobile wireless communications devices face linearity issues with power amplifiers and poor antenna matching, leading to degradation of total radiated power and harmonic interference due to non-linearity, particularly in I and Q power amplifiers.
Innovation Solution
The implementation of separate power amplifier circuits for In-phase (I) and Quadrature (Q) signals, along with a 3 dB quadrature hybrid power combiner, allows for improved linearity, reduced harmonic emission, and efficient amplitude modulation by enabling better control over power amplifier biasing and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single power amplifier is used for combined I and Q signals, then device complexity is reduced, but linearity deteriorates causing harmonic interference
Solution Approach 1:
The patent divides the single power amplifier into two separate power amplifiers - one for I signal and one for Q signal. This segmentation allows each amplifier to operate independently with optimized biasing, improving linearity and reducing harmonic interference while maintaining manageable device complexity through systematic architecture
2Object-generated harmful factors
If separate power amplifiers are used for I and Q signals, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent combines the outputs of two separate power amplifiers using a power combiner that integrates I and Q signal paths. This merging approach consolidates the complex separate amplifier structures into a unified output interface, reducing overall device complexity while preserving the linearity benefits of separate amplification
Solution Approach 2:
The power combiner serves multiple functions simultaneously - it combines I and Q signals, provides impedance matching for both amplifiers, and enables independent bias control while presenting a single unified output. This multi-functionality reduces the need for additional components, managing device complexity
3Object-generated harmful factors
If power amplifier biasing is optimized for linearity, then harmonic interference is reduced, but power consumption increases reducing battery life
Solution Approach 1:
The patent implements dynamic bias control for the power amplifiers, adjusting bias levels based on signal conditions and power requirements. This dynamic adjustment allows the system to achieve optimal linearity when needed while reducing power consumption during normal operation, thereby extending battery life without compromising harmonic interference reduction
4Power
If antenna impedance matching is improved, then total radiated power is enhanced, but device complexity increases due to additional matching circuits
Solution Approach 1:
The power combiner is designed to provide both signal combination and impedance matching functions simultaneously. By making the combiner multi-functional, the patent achieves improved antenna impedance matching and enhanced total radiated power without adding separate matching circuits, thus avoiding increased device complexity
Data Source
AI summary
A communications device, in one aspect as a portable wireless communications device, includes an in-phase modulator and power amplifier that receives a baseband I signal and modulates and amplifies the I signal. A quadrature modulator and power amplifier receives a baseband Q signal and modulates and amplifies the Q signal. A power combiner sums and outputs the I and Q signals. An I demodulator circuit receives a signal fed back from the I power amplifier and demodulates the fed back signal to produce demodulated I signals. A Q demodulator circuit receives a signal fed back from the Q power amplifier and demodulates the fed back signal to produce demodulated Q signals. A processor compares the digital, baseband I and Q signals with a demodulated I and Q signals to compensate for amplitude, frequency and phase modulation errors.