Phased Array Antenna IMD Cancellation Using Opposite-Phase Amplifiers
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Solution Overview
Problem
Existing array antenna systems in the 5G millimeter wave frequency band face challenges in suppressing high-order Intermodulation Distortion (IMD) components, particularly the second IMD component in the second band, which interferes with other carriers and reduces throughput, despite using narrow-band Digital Predistortion (DPD) and Band Pass Filters (BPFs, due to increased power consumption and space constraints.
Innovation Solution
The system employs a configuration of antenna elements with paired HPAs, where one HPA amplifies the second IMD component in phase and the other HPA amplifies it with an opposite phase, canceling out the second IMD component at the receiver, using load-pull techniques to adjust impedance for optimal phase alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wide-band DPD is used to suppress high-order IMD components in the second band, then the interference level in adjacent bands is improved, but the power consumption increases and device complexity increases
Solution Approach 1:
The patent segments the IMD suppression function into two parts: narrow-band DPD handles first IMD components in the first band, while a second DPD handles second IMD components in the second band. This segmentation allows each DPD to operate with lower complexity and power consumption compared to a single wide-band DPD, while collectively achieving comprehensive suppression of all IMD components across both bands.
Solution Approach 2:
The patent applies partial action by implementing narrow-band DPD first to suppress the most critical first IMD components in the first band, then adding a second DPD specifically targeted at second IMD components in the second band. This staged approach suppresses IMD components progressively without requiring the excessive power consumption and complexity of a full wide-band DPD implementation from the start.
2Object-affected harmful factors
If Band Pass Filters are added to suppress second IMD components, then the interference in adjacent bands is reduced, but the device complexity and space requirements increase
Solution Approach 1:
The patent replaces the mechanical/electrical filtering approach (Band Pass Filters) with a digital signal processing approach (second DPD). Instead of using physical filters to suppress second IMD components in the second band, the system uses a second DPD that digitally predistorts the signal to cancel these components before they are generated, thereby achieving the same interference reduction without adding physical filter components.
3Use of energy by moving object
If narrow-band DPD is used to reduce power consumption, then the power efficiency is improved, but the suppression of second IMD components in the second band is insufficient
Solution Approach 1:
The patent segments the IMD suppression function into two parts: narrow-band DPD handles first IMD components in the first band, while a second DPD handles second IMD components in the second band. This segmentation allows each DPD to operate with lower complexity and power consumption compared to a single wide-band DPD, while collectively achieving comprehensive suppression of all IMD components across both bands.
Solution Approach 2:
The second DPD acts as an intermediary component that specifically addresses the limitation of narrow-band DPD by handling second IMD components in the second band. This intermediary DPD bridges the gap between power-efficient narrow-band operation and comprehensive wide-band IMD suppression, allowing the system to maintain low power consumption while achieving adequate suppression of all critical IMD components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively suppresses the second IMD component to zero level, maintaining signal strength while reducing interference, thus enhancing overall system throughput without the need for additional hardware like BPFs.
Implementation Method 1
a second phase shifter corresponding to the second antenna element, and applies a phase shift to the transmission signal and the second nonlinear distortion
Data Source
AI summary
An array antenna system includes DPD that suppresses first IMD in a first band adjacent to a band of a transmission signal, antenna elements that include a first element and a second element, phase shifters that each correspond to each of the elements and form a transmission signal directed to a predetermined direction and second IMD, by applying a weight to the signal and the second IMD in a second band adjacent to the first band, a first amplifier that amplifies the signal directed to the direction and first distortion serving as the second IMD, that are output from a first shifter of the first element, and a second amplifier that amplifies the signal directed to the direction and second distortion a phase of which is opposite to that of the first distortion serving as the second IMD, that are output from a second shifter of the second element.