Antenna Feed Path Asymmetry for Passive Intermodulation Reduction
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Solution Overview
Problem
Passive intermodulation (PIM) in macro cell base station antennas, particularly in frequency-division duplexing systems, is a significant issue due to nonlinear characteristics of components like ferromagnetic materials, thermal effects, mechanical stress, and faulty craftsmanship, leading to reduced uplink coverage and sensitivity.
Innovation Solution
The antenna design incorporates a signal distribution network where each radiating element is connected to the network via an interface with a signal path length differing by at least 0.05 times the wavelength from other connections, causing PIM signals to destructively interfere and reduce or avoid PIM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple interfaces are used to connect radiating elements to the signal distribution network, then the antenna can support more radiating elements and expand cell coverage, but the risk of PIM generation increases due to more connection points
Solution Approach 1:
The patent introduces asymmetric signal path lengths for different interfaces, where each interface has a unique path length difference of at least 0.05 times the wavelength relative to other interfaces. This asymmetric design ensures that PIM signals generated at different interfaces do not align in phase, preventing constructive interference and reducing overall PIM generation while allowing multiple radiating elements to be connected
2Ease of manufacture
If interfaces are arranged at the same location along the signal path, then the manufacturing process is simplified, but PIM signals add up constructively at the power splitter reducing uplink coverage
Solution Approach 1:
The patent applies local quality by maintaining uniform interface arrangement characteristics for most interfaces while introducing a specific local variation in signal path length for certain interfaces. This allows the majority of the antenna structure to be manufactured with standard processes while specific segments are adjusted to create the required path length differences, balancing manufacturing ease with PIM reduction performance
3Object-generated harmful factors
If active solutions for PIM cancelation are implemented, then PIM can be reduced, but the power consumption and computational complexity increase
Solution Approach 1:
The patent converts the harmful effect of PIM signal superposition into a beneficial outcome by deliberately designing signal path length differences that cause destructive interference. Instead of using active cancellation systems that consume power, the passive structural design causes PIM signals to naturally cancel each other out, transforming the problem of PIM generation into a solution that reduces PIM without additional power consumption
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 design effectively reduces PIM, enhancing uplink coverage and sensitivity, and simplifies manufacturing by allowing for passive interference cancellation without increasing power consumption or computational complexity.
Implementation Method 1
a signal distribution network configured to distribute, through the antenna, an electrical signal having an antenna operating frequency, f
Implementation Method 2
By providing this difference in signal path length of the first electrical coupling compared to the second electrical coupling, any PIM signals which may be generated in the antenna, and in particular at the first and second interfaces, may destructively interfere with each other
Data Source
AI summary
We generally describe an antenna comprising: a signal distribution network configured to distribute, through the antenna, an electrical signal having an antenna operating frequency, f, and a plurality of radiating elements, wherein each one of the radiating elements is electrically coupled to the signal distribution network via a corresponding, respective electrical coupling, wherein each one of the electrical couplings comprises a corresponding, respective interface. A signal path length, between a first one of said interfaces and a corresponding, respective first one of said radiating elements, of a first one of said electrical couplings differs from a signal path length, between a second one of said interfaces and a corresponding, respective second one of said radiating elements, of a second one of said electrical couplings by at least 0.05 times a wavelength, λ, corresponding to the antenna operating frequency, f.