RF Front End Module With Supplemental Filters for TDD Coexistence
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Solution Overview
Problem
RF communication systems face challenges in coexistence between cellular and WiFi signals due to mutual desensitization effects, particularly in adjacent frequency bands, leading to interference and compromised performance in TDD systems.
Innovation Solution
A radio frequency front end system is designed with separate transmit and receive filters, including supplemental filters, and switches to dynamically reconfigure the signal paths, ensuring effective rejection of unwanted frequencies and minimizing interference between cellular and WiFi signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If shared filters are used between transmit and receive paths, then device complexity is reduced, but interference between cellular and WiFi signals increases due to mutual desensitization
Solution Approach 1:
The filter system is segmented into separate transmit filters and receive filters, with each filter optimized for its specific function. The transmit filter handles transmit path filtering while the receive filter handles receive path filtering, eliminating the mutual desensitization problem that occurs with shared filters.
Solution Approach 2:
The system dynamically switches between transmit and receive filter configurations based on operational mode. During transmit operations, the transmit filter is active; during receive operations, the receive filter is active. This dynamic reconfiguration allows optimal filtering performance for each mode without the interference problems of shared filters.
2Object-affected harmful factors
If separate transmit and receive filters are used, then signal interference is reduced, but device complexity increases
Solution Approach 1:
The transmit filter and receive filter are merged into a single integrated filter assembly that can be switched between configurations. This integration reduces the overall complexity compared to having completely separate filter systems, while still providing the benefits of separate filtering paths.
Solution Approach 2:
The filter assembly is designed with multi-functionality, serving both transmit and receive functions through a single structure. The same physical filter assembly can be configured for transmit mode or receive mode, reducing the need for multiple dedicated filter assemblies.
3Reliability
If dynamic reconfiguration is implemented, then rejection levels for blockers close to band edges are maintained, but device complexity increases due to additional switches
Solution Approach 1:
Switches are introduced as intermediary components that manage the connection between the filter assembly and the signal paths. These switches enable dynamic reconfiguration of the filter system without requiring complex changes to the filter assembly itself, simplifying the overall control mechanism.
Data Source
AI summary
Radio frequency front end modules are provided. In one aspect, a front end system includes at least one power amplifier configured to amplify a transmit radio frequency signal, at least one low noise amplifier configured to receive a receive radio frequency signal, an output node coupled to an antenna. The front end system also includes a first switch configured to selectively couple the output node to the at least one power amplifier during a transmit period and to the at least one low noise amplifier during a receive period, at least one transmit filter coupled between the power amplifier and the at least one switch, and at least one receive filter coupled between the low noise amplifier and the at least one switch. The front end system further includes a transmit supplemental filter, a receive supplemental filter, and a second switch.