Quadrature Power Amplifier with Dynamic Supply Modulation
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Solution Overview
Problem
Conventional RF power amplifiers face challenges in achieving both high power efficiency and linearity, particularly in digital modulated RF power amplifiers, due to issues like power back-off mode and large peak to average power ratio (PAPR) in multicarrier modulation methods, leading to low efficiency and high adjacent channel interference.
Innovation Solution
A digital quadrature amplitude modulated RF power amplifier subsystem with a first and second channel circuit, each having a supply path and gain path, utilizing variable gain amplifiers and DC to DC converters to produce modulated radio signals, with pre-distortion circuits to negate distortion and improve power efficiency by adjusting gain and supply voltage based on input signal thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a quadrature modulated PA is used, then bandwidth expansion is reduced and implementation is easier, but power efficiency is lower
Solution Approach 1:
The patent implements dynamic supply voltage modulation for the I and Q channel power amplifiers based on the instantaneous signal envelope. The supply voltage is adjusted in real-time according to the signal amplitude, allowing the PAs to operate efficiently across varying power levels while maintaining quadrature modulation's bandwidth advantages.
Solution Approach 2:
The patent changes the supply voltage parameter dynamically to improve power efficiency. By modulating the supply voltage to the power amplifiers according to the signal envelope, the system achieves better power efficiency while maintaining the quadrature modulation architecture's bandwidth characteristics.
2Use of energy by moving object
If a polar modulated PA is used, then power efficiency is higher, but bandwidth expansion increases and adjacent channel interference is high
Solution Approach 1:
The patent applies dynamic supply voltage modulation to quadrature modulated PAs, enabling them to achieve power efficiency levels comparable to polar modulated PAs while maintaining the spectral characteristics and low adjacent channel interference inherent to quadrature modulation.
3Reliability
If conventional analog RF transmitter architecture is used, then linearity is improved, but power consumption increases
Solution Approach 1:
The patent applies pre-distortion to the I and Q channel signals before amplification. This preliminary nonlinear correction compensates for the power amplifiers' nonlinearities, achieving good linearity in the final output while allowing the use of efficient nonlinear power amplifiers instead of power-hungry linear analog amplifiers.
Solution Approach 2:
The patent replaces the traditional linear analog power amplifier architecture with a digital pre-distortion approach combined with efficient switching power amplifiers. This substitution enables achieving linearity through digital signal processing rather than through power-intensive analog linear amplification.
4Reliability
If power back-off mode is used in digital modulated RF power amplifier, then linearity is maintained, but power efficiency becomes poor
Solution Approach 1:
The patent implements dynamic supply voltage modulation that tracks the signal envelope, allowing the power amplifiers to operate near saturation efficiently while the pre-distortion maintains linearity. This eliminates the need for power back-off mode by dynamically adjusting the supply voltage to match signal conditions.
Solution Approach 2:
The system uses the signal envelope as feedback to dynamically control the supply voltage to the power amplifiers. This feedback mechanism enables the amplifiers to operate efficiently across different power levels while maintaining linearity through the combination of pre-distortion and adaptive supply modulation.
Data Source
AI summary
A method and system for achieving increased efficiency in a quadrature modulated power amplifier (11) are disclosed. In some embodiments, a supply path (36, 40) and a gain path (38, 42) are provided in each of an I-channel and a Q-channel. The supply path (36, 40) produces a variable voltage and the gain path (38, 42) produces a gain control signal. The variable voltage and gain control signal are used by a variable gain power amplifier (44, 46) to modulate a local oscillator signal to produce a modulated radio signal.