RF Digital Pre-Distortion for Wideband Power Amplifier Linearity
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Solution Overview
Problem
Existing digital pre-distortion systems in baseband domain face limitations in handling increasing signal bandwidth, leading to inefficiencies and increased hardware requirements, while power amplifiers in transmitters suffer from non-linearity issues that distort signals and adjacent channels.
Innovation Solution
Implementing a digital pre-distortion system in the radio frequency (RF) domain, which performs pre-distortion after up-sampling the baseband signal, using a DPD processing module with a memory array and digital signal processor to compensate for non-linearities in power amplifiers and digital-to-analog converters, reducing interface bandwidth and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital pre-distortion is implemented in baseband domain, then the system can correct non-linearities, but the interface bandwidth and hardware complexity increase significantly
Solution Approach 1:
The patent transitions the DPD implementation from baseband domain to RF domain, changing the operational dimension of signal processing. This dimensional shift allows the system to process signals at higher frequencies where bandwidth requirements are more efficiently managed, reducing interface bandwidth needs while maintaining distortion correction capabilities
Solution Approach 2:
The patent changes key operating parameters by moving DPD to RF domain operation. This includes changing the frequency domain of operation from baseband to RF, which fundamentally alters the bandwidth characteristics and interface requirements, thereby reducing hardware complexity while preserving signal linearity correction
2Reliability
If digital pre-distortion is implemented in baseband domain, then the system can linearize power amplifier output, but the power consumption increases
Solution Approach 1:
By moving DPD to RF domain, the system changes the operational dimension which inherently reduces the computational burden and data rates required, leading to lower power consumption while maintaining the same signal linearity correction function
Solution Approach 2:
The patent extracts the DPD function from the baseband processing chain and relocates it to the RF domain, separating it from high-power baseband operations. This extraction allows DPD to operate independently at lower power levels while still achieving the desired linearization effect
3Adaptability or versatility
If baseband DPD system handles increasing signal bandwidth, then more bandwidth is supported, but the interface requirements and hardware complexity increase
Solution Approach 1:
The patent resolves the bandwidth-scaling problem by changing the operational dimension to RF domain, where bandwidth handling is more efficient. This dimensional change allows the system to support increasing signal bandwidths without proportionally increasing interface requirements, as RF domain processing naturally accommodates wider bandwidths with fewer resources
Data Source
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AI summary
Digital pre-distortion (DPD) systems are often used to improve the linearity of a power amplifier in transmitters. These DPD systems are typically implemented in baseband (prior to modulation). However, ever increasing signal bandwidth requirements limits the practicality of DPD systems implemented in baseband. A DPD system in the radio frequency (RF) domain (as opposed to in baseband) can solve this problem and further improve a DPD system's ability to correct for distortions. The RF domain DPD system is upstream from a digital-to-analog converter, and performs DPD after a baseband signal is up-sampled into the RF domain (after the modulation process). When compared against a baseband DPD system, the RF domain DPD system can handle significantly wider bandwidth, and has an improved ability to linearize a wide variety of distortions present in the spectrum.