Parallel RF Power Amplifier Linearization Using Analogue Pre-Distortion
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Solution Overview
Problem
RF power amplifiers face challenges in producing high output powers with reduced signal distortion, especially at frequencies above 10 GHz, where non-linearity generates distortion products that can interfere with adjacent channels, and existing digital pre-distortion methods are not suitable for high bandwidth signals like those used in Ku and Ka bands.
Innovation Solution
A low complexity analogue pre-distortion network is used in a parallel amplifier architecture, where distortion products from one amplifier are manipulated and fed back to the other to cancel out distortion, utilizing Wilkinson power splitters and variable attenuators/phaseshifters to suppress third-order and fifth-order intermodulation distortion products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If RF power amplifiers are operated in compression region to achieve high output power, then power output is improved, but signal distortion increases due to non-linearity
Solution Approach 1:
The invention applies preliminary action by introducing pre-distortion to the input signal before amplification. The pre-distortion network modifies the input signal in advance to compensate for the anticipated non-linear distortion that will occur when the amplifier operates in the compression region, thereby maintaining signal integrity while achieving high output power
Solution Approach 2:
The invention converts the harmful non-linear distortion into a beneficial effect by using the distortion characteristics of the amplifier to generate pre-distortion signals that cancel out the harmful distortion products. The distortion generated by operating in compression region is harnessed to create corrective pre-distortion signals through the parallel amplifier architecture
2Object-generated harmful factors
If digital pre-distortion methods are used to reduce distortion, then signal quality is improved, but device complexity increases and is not suitable for high bandwidth signals
Solution Approach 1:
The invention substitutes complex digital pre-distortion processing with a simpler analogue signal processing approach. By using analogue pre-distortion networks and parallel amplifier architectures, the system replaces computationally intensive digital signal processing with direct analogue manipulation, reducing device complexity while maintaining effectiveness for high bandwidth signals
Solution Approach 2:
The invention applies self-service by using the distortion products generated by the amplifiers themselves to create the pre-distortion signals. The system utilizes the inherent distortion characteristics of the amplifiers to generate corrective signals, eliminating the need for external complex pre-distortion processing systems
3Power
If multiple smaller amplifiers are combined in parallel to achieve high output power at frequencies above 10 GHz, then power output is improved, but distortion products increase due to individual amplifier non-linearity
Solution Approach 1:
The invention applies segmentation by dividing the high power amplification function into multiple parallel amplifier channels. Each amplifier operates at lower power levels individually, reducing their individual distortion generation, while the overall system achieves high output power through parallel combination. The pre-distortion network further segments the distortion correction function across the parallel channels
Solution Approach 2:
The invention merges the output signals from multiple parallel amplifiers to achieve high output power. By combining the amplified signals constructively while they are still in the linear region, the system achieves high power output with reduced distortion compared to single high-power amplifiers. The pre-distortion signals are also merged with the main signal paths to provide collective distortion cancellation
Data Source
AI summary
A power amplifier comprising:a first amplifier;a second amplifier, wherein the first and second amplifiers are arranged in parallel;an analogue pre-distortion network;a first coupler; anda second coupler,wherein the first coupler is configured to receive an input signal, direct said input signal to the first amplifier, and direct a first pre-distortion signal to the analogue pre-distortion network, whereinthe first pre-distortion signal comprises a first distortion component generated at the input of the first amplifier, andthe analogue pre-distortion network is configured to receive the first pre-distortion signal and manipulate its amplitude and/or phase to obtain a manipulated first pre-distortion signal, andthe second coupler is configured to direct the manipulated first pre-distortion signal to the second amplifier.