Antenna Isolation Circuit for Concurrent LMR and LTE Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Portable communications devices operating over multiple communication systems, such as LMR and LTE, experience significant RF interference due to substantial coupling between their antennas, leading to decreased communication quality and potential exceedance of regulatory limits on spurious RF emissions.
Innovation Solution
The device incorporates an isolator circuit and a bidirectional diplexer to provide isolation between transceivers and reduce RF coupling, using phasor-shaping networks to minimize interference, and a bidirectional diplexer to manage electrical length and attenuation across different frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple transceivers operate concurrently in a portable device, then communication versatility is improved, but RF interference between transceivers increases
Solution Approach 1:
The patent divides the RF signal paths into separate segments using isolator circuits and bidirectional diplexers. Each transceiver operates in its own isolated frequency band, with physical segmentation of the transmission paths preventing interference between LMR and LTE transceivers while maintaining concurrent operation capability
Solution Approach 2:
The patent introduces isolator circuits and bidirectional diplexers as intermediary components between transceivers and antennas. These intermediaries act as mediators that allow multiple transceivers to share common antennas without direct interference, by selectively routing frequency bands through appropriate isolation paths
2Volume of moving object
If antennas are placed close together to reduce device size, then device compactness is improved, but RF coupling between antennas increases
Solution Approach 1:
The patent places isolator circuits and bidirectional diplexers as intermediary components in the transmission paths between antennas and transceivers. These intermediaries provide RF isolation that prevents harmful coupling between closely-spaced antennas, enabling compact device design without sacrificing interference performance
Solution Approach 2:
The patent applies frequency-selective isolation properties locally at different parts of the RF transmission system. The isolator circuits provide direction-dependent isolation specifically at antenna interfaces, while bidirectional diplexers provide frequency-band-specific isolation, allowing compact antenna placement with targeted interference mitigation
3Object-generated harmful factors
If isolator circuits are added to reduce RF interference, then interference isolation is improved, but device complexity increases
Solution Approach 1:
The patent employs bidirectional diplexers that perform multiple functions simultaneously: they provide RF isolation between transceivers, route different frequency bands to appropriate antennas, and enable bidirectional signal flow. This multi-functionality reduces the need for separate isolation components, managing circuit complexity while maintaining interference mitigation
4Speed
If bidirectional diplexer is used to reduce electrical length, then signal transmission efficiency is improved, but isolation performance may be compromised
Solution Approach 1:
The patent applies frequency-selective properties locally within the bidirectional diplexer, providing different transmission characteristics for different frequency bands. The diplexer optimizes electrical length and signal efficiency for specific bands (e.g., LMR) while maintaining isolation performance for other bands (e.g., LTE) through its frequency-dependent routing behavior
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 configuration achieves concurrent operation with reduced RF interference, improved communication quality, and compliance with regulatory RF emission limits, while allowing efficient use of overlapping and non-overlapping frequency bands.
Implementation Method 1
an isolator circuit provided on the transmission path. The isolator circuit is configured to provide isolation between the first transceiver and the second transceiver when the second transceiver is operating in the second range of frequencies
Implementation Method 2
a bidirectional diplexer provided on the transmission path. The bidirectional diplexer is coupled to the second transceiver and the isolator circuit and configured to reduce an electrical transmission length when the second transceiver is operating over the third range of frequencies
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Portable communications devices (100) with reduced interference between communication systems. One embodiment provides a portable communications device (100) including a first antenna (120), a second antenna (130), a first transceiver (140) configured to operate over a first range of frequencies (760), a second transceiver (150) configured to operate over a second range of frequencies (760) and a third range of frequencies (760). The portable communications device (100) includes an isolator circuit (170) coupling the first transceiver (140) and the second transceiver (150) to the first antenna (120) and the second antenna (130). The isolator circuit (170) is configured to provide isolation between the first transceiver (140) and the second transceiver (150) when the second transceiver (150) is operating in the second range of frequencies (760). The portable communications device (100) further includes a bidirectional diplexer (180) coupling the second transceiver (150) to the isolator circuit (170). The bidirectional diplexer (180) is configured to reduce an electrical transmission length when the second transceiver (150) is operating over the third range of frequencies (760).