RF Front End Module Using Common Filter Architecture for TDD Rejection
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Solution Overview
Problem
RF communication systems face challenges in achieving high rejection and low insertion loss in TDD modes, especially when bands are closely spaced, leading to coexistence issues between cellular and WiFi signals, and stringent regulatory requirements for 5G NR.
Innovation Solution
The implementation of a radio frequency front end system with separate transmit and receive filters, multiplexers, and switches that allow for simultaneous operation of multiple bands, using a single-pole N-throw or double-pole quadruple-throw switches to manage signal paths efficiently, and employing supplemental filters to address specific interference issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common filter is used for both transmit and receive paths in TDD mode, then device complexity and cost are reduced, but rejection performance deteriorates when bands are closely spaced
Solution Approach 1:
The filter system is segmented into separate transmit filters and receive filters that can be independently configured and optimized for their respective functions, allowing each filter to be specifically designed for closely spaced bands without compromise
2Reliability
If separate transmit and receive filters are implemented, then rejection performance is improved for closely spaced bands, but device complexity and module size increase
Solution Approach 1:
The filter architecture is designed with universal components that can serve multiple functions - the same filter structure handles both transmit and receive paths with different configurations, reducing overall complexity despite having separate filters for each path
3Reliability
If filters are optimized for high rejection in receive mode, then coexistence between cellular and WiFi signals improves, but insertion loss increases in transmit mode
Solution Approach 1:
Different filter characteristics are applied locally to different signal paths - the receive filter is optimized for high rejection to protect against interferers, while the transmit filter is optimized for low insertion loss to preserve transmitted signal strength, with each filter having tailored properties for its specific function
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 further includes at least one 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.