Wireless Transmitter Phase-Split Branching for Intermodulation Mitigation
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Solution Overview
Problem
Intermodulation distortion caused by non-linear hardware components in wireless transmitters is difficult to filter out and often requires costly pre-distortion, leading to increased power consumption and vulnerability of nearby channels, especially in multi-carrier scenarios.
Innovation Solution
A method and apparatus for a wireless transmitter with multiple signal branches, each comprising a non-linear hardware component, where input signals are modified with specific phase shifts to mitigate intermodulation components by partitioning the input signal spectrum into non-overlapping parts and combining the output signals to cancel distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If pre-distortion is applied to compensate for non-linearity, then intermodulation distortion is reduced, but signal bandwidth must be widened and power consumption increases
Solution Approach 1:
The input signal spectrum is divided into multiple non-overlapping parts (first part, second part, etc.), each processed by separate signal branches with different phase shifts. This segmentation allows targeted mitigation of intermodulation distortion without requiring full-signal pre-distortion, reducing power consumption while maintaining effectiveness.
Solution Approach 2:
Different phase shifts are applied to different parts of the input signal spectrum based on local characteristics. The first phase shift is applied to the first part of the spectrum and the second phase shift to the second part, allowing optimized local distortion mitigation rather than uniform processing of the entire signal.
2Object-generated harmful factors
If pre-distortion is applied to compensate for non-linearity, then intermodulation distortion is reduced, but transmitter bandwidth requirements increase
Solution Approach 1:
The input signal spectrum is divided into multiple non-overlapping parts, each processed independently with specific phase shifts. This segmentation confines the bandwidth expansion effect to only the necessary frequency regions for distortion mitigation, rather than requiring the entire signal bandwidth to be widened as in conventional pre-distortion.
Solution Approach 2:
Instead of applying pre-distortion in the conventional manner that widens the entire signal bandwidth, this invention applies inverse phase shifts to specific spectral parts after non-linearity occurs, effectively canceling distortion products without requiring overall bandwidth expansion.
3Device complexity
If conventional single-branch transmission is used, then device complexity is low, but intermodulation distortion contaminates wide frequency ranges
Solution Approach 1:
The transmitter is divided into multiple signal branches (first signal branch, second signal branch), each processing different parts of the input signal spectrum with different phase shifts. This segmentation enables effective distortion mitigation by creating phase differences that cause intermodulation products to cancel when signals are combined, without requiring overly complex multi-carrier architectures.
Solution Approach 2:
The signal branches are configured with asymmetric phase shift relationships - the first phase shift and second phase shift have specific directional relationships that create asymmetric processing of the input spectrum. This asymmetry is key to generating the phase differences needed for intermodulation cancellation while maintaining relatively simple branch structures.
4Productivity
If multi-carrier techniques are used to increase throughput, then productivity increases, but intermodulation distortion spreads over larger frequency ranges
Solution Approach 1:
The multi-carrier signal is segmented into different spectral parts processed by separate signal branches. Each branch applies specific phase shifts to its assigned spectral portion, enabling parallel processing that maintains high throughput while the phase relationships ensure intermodulation products from multiple carriers cancel rather than accumulate across the frequency spectrum.
Data Source
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AI summary
A method of a wireless transmitter is disclosed. The method is for mitigation of distortion caused by non-linear hardware components of the transmitter, wherein mitigation of distortion comprises mitigating at least one intermodulation component, wherein the transmitter is configured to process an input signal having an input signal spectrum, and wherein the transmitter comprises two or more signal branches, each signal branch comprising a respective non-linear hardware component. The method comprises modifying the input signal for a first one of the signal branches by applying a first phase shift to a first part of the input signal spectrum, wherein the first phase shift has a first sign and a first absolute value, and applying a second phase shift to a second part of the input signal spectrum. The second phase shift has a second sign which is opposite to the first sign, and a second absolute value which is equal to the first absolute value. The first and second parts are non-overlapping. The method also comprises modifying the input signal for a second one of the signal branches by applying the first phase shift to the second part of the input signal spectrum, and applying the second phase shift to the first part of the input signal spectrum. The method further comprises feeding the modified input signals to respective ones of the signal branches. Corresponding apparatus, wireless transmitter, communication device, and computer program product are also disclosed.