LTE Front End Circuit with Segmented RF Switching
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Solution Overview
Problem
The complexity and cost of manufacturing mobile wireless communications devices are increased due to the complexity of the front end module in LTE devices, particularly in carrier aggregation mode, where self-interference becomes a significant issue as more frequency bands and transceivers are added, leading to difficulties in RF performance.
Innovation Solution
The implementation of a mobile wireless communications device with a front end circuit comprising band pass filters, LNAs, and RF switching circuits, each RF switching circuit being a single-pole, double-throw (SPDT) switch, coupled between LNAs and LTE RF differential inputs, and controlled by a MIPI module, allowing for flexible operation in carrier aggregation mode and reducing the number of pins and components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple band pass duplexers and double-pole switches are used to support multiple frequency bands, then band capability is improved, but device complexity increases
Solution Approach 1:
The front end circuit is divided into multiple independent receive pathways, each handling a specific frequency band. Each pathway contains its own band pass filter and LNA, allowing selective activation based on operational needs. This segmentation reduces the complexity of managing all bands simultaneously while maintaining full band capability.
Solution Approach 2:
The system dynamically selects and activates only the receive pathways needed for current operation. The RF processor can enable or disable specific pathways based on the frequency bands being used, adapting the front end complexity to match the actual operational requirements rather than maintaining maximum complexity at all times.
2Adaptability or versatility
If more transceivers and frequency bands are added to support carrier aggregation, then adaptability is improved, but self-interference increases
Solution Approach 1:
Each receive pathway is independently configured with its own band pass filter and LNA, allowing isolated control of signal paths. This segmentation enables the system to manage multiple frequency bands simultaneously while preventing interference between pathways through proper isolation and selective activation.
Solution Approach 2:
The band pass filters act as intermediaries between the antenna and the RF processor, selectively passing only the desired frequency bands while blocking others. This intermediary filtering prevents out-of-band signals from causing interference in the RF processor, enabling safe operation with multiple active pathways.
3Adaptability or versatility
If multiple double-pole four-throw switches are used for band routing, then band switching capability is improved, but manufacturing cost increases
Solution Approach 1:
The switching function is distributed across multiple simple single-pole double-throw switches, one for each receive pathway, rather than using complex multi-pole multi-throw switches. This segmentation simplifies the switching architecture, reducing component complexity and manufacturing cost while maintaining the ability to route multiple bands.
Solution Approach 2:
Multiple simple switches are combined to achieve the functionality of a single complex switch. By using several single-pole double-throw switches in parallel, each controlling a separate receive pathway, the system achieves equivalent band switching capability with simpler, less expensive components.
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
This solution provides improved RF performance, reduced component count, lower current consumption, better noise immunity, and flexibility to accommodate future band changes without the need for re-spinning the RF IC, enabling efficient support for multiple band combinations and carrier aggregation.
Implementation Method 1
each signal pathway may comprise a filter to help isolate the desired frequency band from extraneous electromagnetic signals
Implementation Method 2
a plurality of LNAs coupled respectively to the plurality of band pass filters
Implementation Method 3
a plurality of RF switching circuits, each RF switching circuit respectively coupled between each LNA and a pair of LTE RF differential inputs
Data Source
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AI summary
A mobile wireless communications device (10) may include an antenna (12), LTE RF differential inputs (18a-18f), and a front end circuit (21-23). The front end circuit may include band pass filters (24a-24b, 31a-31b, 44a-44b) coupled to the antenna, LNAs (25a-25b, 32a-32b, 43a-43b) coupled respectively to the band pass filters, and RF switching circuits (26a-26b, 33a-33b, 42a-42b). Each RF switching circuit may be respectively coupled between each LNA and a pair of LTE RF differential inputs (18a-18b) and configured to switch to one or both of the pair of LTE RF differential inputs.