RF Front-End Segmentation for FDD Isolation
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Solution Overview
Problem
Modern RF communication systems face challenges in achieving high isolation and low insertion losses during frequency division duplex (FDD) operations due to Tx carrier signal power and noise leakage into the receive band, which degrades sensitivity and introduces intermodulation distortion.
Innovation Solution
A radio frequency front end system with separate transmit and receive paths, using switches to selectively connect antennas to filters, allowing for concurrent frequency division duplex communication while minimizing interference through separate integrated circuit packages and conductive segments for improved isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Tx and Rx filters are co-designed and connected together into a duplexer to improve isolation, then Tx-to-Rx isolation is improved, but filter loading and insertion losses increase
Solution Approach 1:
The patent divides the RF front-end into separate transmit and receive paths with independent filters, rather than using a single integrated duplexer. The transmit path includes a transmit filter connected to the transmit amplifier, and the receive path includes a receive filter connected to the receive amplifier, with separate antenna connections. This segmentation eliminates the filter loading effect that occurs when filters are ganged together, reducing insertion losses while maintaining isolation through spatial separation and independent filtering.
2Reliability
If Tx and Rx filters are ganged together with common merged connection to meet isolation specifications, then Tx-to-Rx isolation is improved, but sensitivity degrades due to higher insertion losses
Solution Approach 1:
The patent segments the RF front-end into independent transmit and receive paths with separate filters and antenna connections. This eliminates the insertion losses associated with ganged filter connections, thereby improving receive sensitivity. The segmentation allows each filter to operate independently without loading effects, maintaining optimal filtering performance while preserving signal strength for sensitive receive operations.
3Reliability
If separate antenna connections are used for Tx and Rx paths to reduce interference, then Tx-to-Rx isolation is improved, but device complexity increases
Solution Approach 1:
The patent uses separate antenna connections for transmit and receive paths, with the transmit antenna and receive antenna physically separated or isolated. This segmentation provides inherent isolation through spatial separation, reducing the need for complex isolation circuits. The separate connections simplify the overall architecture by eliminating the need for complex switching networks or isolation amplifiers that would be required to achieve the same isolation with shared antenna connections.
Data Source
AI summary
A radio frequency front end system has a first transmit path and a first receive path. There is a first transmit filter within the first transmit path and a first receive filter within the first receive path. One or more switches can be configured to selectively connect a first antenna to the first transmit filter and to selectively connect a second antenna to the first receive filter to allow frequency division duplex communication over the first transmit path and the first receive path in which the first transmit path transmits over the first antenna simultaneous with the first receive path receiving over the second antenna.