Parallel Digital Predistortion for Wideband Multi-Band Transmitters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wide bandwidth transmitters in wireless communication systems face challenges in implementing digital predistortion due to increased hardware requirements and limitations in application-specific integrated circuits (ASICs) and field-programmable gate arrays (FPGAs).
Innovation Solution
The proposed solution involves an apparatus and method that receive a signal with multiple frequency bands, sample it at a given frequency, and process it using both oversampling and non-oversampling predistortion circuits in parallel. This approach allows for efficient handling of linear and non-linear terms causing intermodulation within and outside the Nyquist band, effectively reducing hardware resource requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oversampling is applied to process all non-linear terms in a single predistortion circuit, then intermodulation distortion outside Nyquist band is reduced, but hardware resource requirements increase significantly
Solution Approach 1:
The patent divides the predistortion processing into two separate parallel circuits: a first predistortion circuit that applies oversampling to handle linear terms and composite non-linear terms causing intermodulation outside the Nyquist band, and a second predistortion circuit that processes without oversampling to handle further non-linear terms causing intermodulation inside the Nyquist band. This segmentation allows each circuit to be optimized for its specific function, reducing overall hardware resource requirements while maintaining predistortion accuracy.
2Productivity
If wide bandwidth transmission is implemented using multiple RF bands, then transmission efficiency is improved, but the realization of predistortion becomes more difficult
Solution Approach 1:
The patent segments the predistortion processing based on the frequency characteristics of different non-linear terms. The first predistortion circuit with oversampling handles terms affecting out-of-band emissions across multiple RF bands, while the second circuit handles in-band distortion terms. This segmentation makes wide bandwidth predistortion realizable by breaking down the complex multi-band problem into manageable sub-problems that can be processed in parallel.
Solution Approach 2:
The patent introduces the dimension of oversampling factor to differentiate the processing approaches. By applying oversampling in the first predistortion circuit, the system can handle intermodulation products that fall outside the Nyquist band, which is critical for wide bandwidth multi-RF band transmission. This dimensional approach allows the system to maintain spectral purity across multiple bands without requiring a single overly complex processing circuit.
3Loss of energy
If power amplifier is driven into compression to increase efficiency, then power consumption is reduced, but distortion in output signal increases
Solution Approach 1:
The patent applies predistortion processing before the power amplifier to pre-compensate for the distortion that will be introduced when the amplifier operates in compression mode. By inverting the non-linear characteristics of the power amplifier through predistortion, the system can drive the amplifier into compression for high efficiency while the predistorted signal ensures that the final output signal maintains its quality and linearity.
Data Source
AI summary
As solution for predistorting a signal is presented. The solution comprises receiving (600) as an input a signal comprising at least two signal components on a different band, sampling (602) the input signal comprising linear terms, composite non-linear terms causing intermodulation outside Nyquist band of the input signal and further non-linear terms causing intermodulation inside the Nyquist band, the further non-linear terms comprising multi-band terms. Oversampling (604) by a given factor is applied to the signal in a first predistortion circuit for processing the linear terms and composite non-linear terms causing intermodulation outside Nyquist band; processing (606) the input signal without oversampling in a second predistortion circuit in parallel with the first predistortion circuit for the further non-linear terms. The rates of the output signals of the predistortion circuits are matched (608), combined and filtered (610).