Multiplexer Transformer Self-Interference Cancellation
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Solution Overview
Problem
In duplexers with shared antennas, simultaneous transmission and reception lead to self-interference issues, where high-powered transmit signals obscure low-powered receive signals, necessitating effective frequency isolation and interference cancellation.
Innovation Solution
A multiplexer design incorporating transformers and filters to provide frequency isolation and cancellation, with series connections of windings and filters to invert and cancel leakage signals between transmit and receive ports, and additional filters and impedances to ensure matched impedance and frequency tuning for optimal signal transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a shared antenna is used for simultaneous transmission and reception, then the duplexer achieves efficient signal transfer and compact design, but self-interference occurs where high-powered transmit signals obscure low-powered receive signals
Solution Approach 1:
The patent divides the signal paths into separate transmit and receive filters connected to different ports of the multiplexer, segmenting the harmful transmit signal from the receive path while maintaining shared antenna usage. This segmentation allows simultaneous transmission and reception with reduced interference.
Solution Approach 2:
The patent introduces a multiplexer with transformer-based isolation as an intermediary device between the shared antenna and the transmit/receive signals. The transformer provides galvanic isolation and impedance transformation, acting as a mediator that enables simultaneous transmit and receive operations while minimizing self-interference.
2Object-affected harmful factors
If frequency isolation is increased to reduce self-interference, then receive signal clarity improves, but device complexity increases due to additional filters and isolation components
Solution Approach 1:
The multiplexer serves multiple functions simultaneously: it provides frequency isolation, impedance transformation, and signal routing in a single device. The transformer within the multiplexer performs both isolation and impedance matching, reducing the need for separate components and thereby limiting complexity increase.
Solution Approach 2:
The patent utilizes transformer turns ratios to change impedance parameters and achieve frequency isolation. By adjusting the transformer parameters and filter characteristics, the system achieves effective self-interference reduction while maintaining a relatively compact and manageable circuit arrangement.
3Power
If transmit power is increased to improve transmission range, then signal coverage extends, but self-interference at the receiver increases, obscuring weak receive signals
Solution Approach 1:
The multiplexer with transformer isolation acts as an intermediary that blocks the high-powered transmit signal from coupling into the receive path. The transformer provides galvanic isolation that prevents the increased transmit power from directly interfering with the sensitive receive signals, enabling high-power transmission without proportionally increasing self-interference.
Solution Approach 2:
The patent segments the high-powered transmit signal path from the low-powered receive signal path using separate filters and multiplexer routing. This segmentation ensures that increasing transmit power does not linearly increase the interference level at the receiver, as the paths are electrically isolated through the multiplexer structure.
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
The solution effectively reduces self-interference by isolating transmit and receive signals and cancelling leakage, ensuring clear reception even during simultaneous transmission and reception, thereby enhancing the duplexer's performance in minimizing interference.
Implementation Method 1
a transformer connected at the first port, and having a first winding connected between the first port and one of the third and fourth ports and a second winding connected to the other of the third and fourth ports and electrical ground
Implementation Method 2
a transmit filter connected between the port for connection to the antenna and one of ports to which that port is connected; and a receive filter connected between the port for connection to the antenna and the other of the ports to which that port is connected
Data Source
AI summary
There is disclosed a multiplexer comprising: a first port; a second port; a third port connected to the first port and the second port; a fourth port connected to the first port and the second port; and a transformer connected at the first port, and having a first winding connected between the first port and one of the third and fourth ports and a second winding connected to the other of the third and fourth ports and electrical ground, wherein one of the first to fourth ports is for connection to an antenna, the multiplexer further comprising: a transmit filter connected between the port for connection to the antenna and one of ports to which that port is connected; and a receive filter connected between the port for connection to the antenna and the other of the ports. A cancellation circuit connected between the third and fourth ports, comprises a plurality of parallel channels between the second receive and transmit filters, each channel including a filter.