Feed-Forward Electrical Balance Duplexer for Low-Loss TX/RX Isolation
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Solution Overview
Problem
Conventional transceivers using electrical balance duplexers face challenges with signal insertion loss and increased costs due to the need for additional filters, which also result in limited isolation between transmitter and receiver paths, especially in frequency division duplexing applications.
Innovation Solution
The integration of feed-forward paths into electrical balance duplexers allows for dynamic mode changes, including insertion loss reduction, frequency swap, and high isolation modes, using switches to control these pathways and mitigate signal interference while reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional electrical balance duplexers are used for isolation between transmitter and receiver paths, then signal interference is reduced, but insertion loss increases and device area/cost increases due to additional filters
Solution Approach 1:
The patent extracts the harmful isolation function from traditional filter-based duplexers and implements it through a feed-forward cancellation mechanism. The transmitter signal is tapped, phase-shifted, and subtracted from the receiver path to cancel interference, eliminating the need for bulky filters while maintaining isolation performance.
Solution Approach 2:
The patent introduces an intermediary feed-forward path that captures the transmitter signal and processes it through phase shifters and combiners to create a cancellation signal. This intermediary mechanism mediates between the transmitter and receiver, providing isolation without requiring traditional filtering components.
2Loss of energy
If additional filters are added to reduce insertion loss, then signal quality improves, but device area and manufacturing cost increase
Solution Approach 1:
The patent replaces the mechanical/filter-based isolation system with an electronic feed-forward cancellation system. Instead of using physical filters to block interference, the system uses electronic signal processing with phase shifters and signal combiners to actively cancel the transmitter signal from the receiver path, reducing both insertion loss and device area.
Solution Approach 2:
The feed-forward duplexer structure serves multiple functions simultaneously: it provides isolation between transmitter and receiver, reduces insertion loss, and eliminates the need for separate filter components. The same signal path structure accomplishes what would traditionally require multiple discrete filtering elements.
3Device complexity
If traditional duplexers are used without feed-forward paths, then device complexity is reduced, but isolation between transmitter and receiver paths is limited
Solution Approach 1:
The patent implements a feed-forward feedback mechanism where the transmitter signal is continuously monitored, phase-adjusted, and fed back into the receiver path to cancel interference. This active feedback loop dynamically maintains isolation performance without requiring complex passive filter structures, achieving high isolation with moderate complexity.
Data Source
AI summary
Systems, methods, and devices for reducing insertion loss and/or swapping transmitter (TX) and receiver (RX) frequencies in an electrical balance duplexer (EBD) used in a transceiver device for frequency division duplexing (FDD) applications are provided. Feed-forward receiver path from the antenna to a low noise amplifier (LNA) and a feed-forward path from the antenna to a power amplifier (PA) of the EBD may be used for reducing insertion loss of the RX and TX signals. In some embodiments, switches may be used to selectively alter operational modes for varied levels of isolation and/or swapping of TX and RX frequencies.