Multiband Digital Predistortion for Broadband HPA Linearization
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Solution Overview
Problem
Conventional RF transmitters face challenges in efficiently addressing non-linear distortion introduced by high-power amplifiers, particularly when driven near saturation, which leads to spectral spreading and in-band distortion, degrading system performance.
Innovation Solution
The implementation of multiband digital predistortion (mDPD) in RF transmitters, which segments the signal spectrum into multiple frequency sub-bands and applies non-linear distortion compensation for each sub-band, effectively compensating for both in-band and cross-band distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-band DPD is applied on the full signal spectrum, then non-linear distortion compensation is achieved, but sampling rates must be four to eight times the full signal bandwidth which becomes excessively costly and difficult to support
Solution Approach 1:
The patent segments the wideband signal into multiple narrowband sub-signals, each occupying a smaller frequency portion. DPD is then applied independently to each narrowband sub-signal at a reduced sampling rate. This segmentation approach maintains effective distortion compensation while dramatically reducing the sampling rate requirements from 4-8 times the full bandwidth to much lower rates per sub-band.
2Reliability
If high sampling rates are used for broadband DPD, then linearization performance is improved, but practical limitations of DACs, ADCs, and other components become prohibitive
Solution Approach 1:
By dividing the broadband signal into multiple narrowband sub-signals, the patent enables DPD implementation at reduced sampling rates that are practical for existing DACs, ADCs, and other components. Each sub-signal is processed independently at a manageable sampling rate, avoiding the prohibitive component requirements that would result from applying DPD to the entire wideband signal at high sampling rates.
3Device complexity
If conventional DPD approaches are used in very high throughput contexts, then implementation is simplified, but non-linear interactions across bands are neglected resulting in severe performance limitations
Solution Approach 1:
The patent segments the signal into multiple narrowband sub-signals and applies DPD to each sub-band. This segmentation enables the system to capture and compensate for non-linear interactions within each band while maintaining relative implementation simplicity. The independent processing of sub-bands allows for effective linearization performance that conventional single-band approaches cannot achieve in broadband contexts.
Data Source
AI summary
Techniques are described for implementing multiband digital predistortion in a broadband transmitter in a manner that provides effective compensation of non-linear distortion arising from integration of a high-power amplifier (HPA). Embodiments segment the signal spectrum of a transmit signal into multiple sub-band signals and apply non-linear distortion compensation separately and concurrently for each sub-band signal. The resulting multi-band digital predistortion (mDPD) compensates both for in-band distortion and for distortions from non-linear interactions between the frequency sub-bands. The disclosed mDPD can provide enhanced performance features, such as handling of memory effects, reduced sampling rate requirements for DPD components, and minimizing detrimental spectral regrowth at the HPA output.