Front-end Circuit Using Circulator and Variable Filters for Carrier Aggregation
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Solution Overview
Problem
Existing front-end circuits supporting multiple frequency bands are large in size and suffer from degraded reception sensitivity during carrier aggregation, particularly in low-frequency bands due to the need for numerous switches and band pass filters.
Innovation Solution
A front-end circuit design that eliminates the use of switch ICs in the circuitry for low-frequency bands by employing a circulator and variable filters, allowing for reduced size and effective carrier aggregation across multiple frequency bands, including low bands, while preventing harmonic leakage and ensuring reliable signal separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple switch ICs are used to support multiple frequency bands, then frequency band support is improved, but circuit size increases
Solution Approach 1:
The circulator is configured to handle multiple frequency bands (first communication signal range and second communication signal range) simultaneously through its multiple ports, eliminating the need for separate switch ICs for each frequency band. The first multiplexer also provides multi-functionality by routing signals across different frequency ranges through a single device, thereby reducing the overall number of components and circuit size while maintaining broad frequency band support.
Solution Approach 2:
The patent combines the functions of multiple switch ICs into a single circulator and multiplexer configuration. The circulator integrates signal routing for both first and second communication signal ranges, while the multiplexer consolidates frequency selection functionality, merging what would traditionally require multiple discrete switch ICs into fewer unified components, thus reducing circuit footprint.
2Productivity
If transmission and reception are performed simultaneously in multiple frequency bands (carrier aggregation), then communication capacity is improved, but reception sensitivity is degraded by transmission signals
Solution Approach 1:
The circulator segments the signal paths into distinct ports for transmission and reception, with dedicated routing for first and second communication signal ranges. This segmentation isolates transmission signals from reception paths, preventing interference and maintaining reception sensitivity even during simultaneous carrier aggregation operations across multiple frequency bands.
Solution Approach 2:
The multiplexer acts as an intermediary device that selectively routes transmission and reception signals based on their frequency ranges. By mediating between the antenna and the transmission/reception circuits, it ensures that transmission signals do not leak into reception paths, thereby protecting reception sensitivity while enabling simultaneous multi-band carrier aggregation.
Data Source
AI summary
A front-end circuit includes a multiplexer, a circulator, reception ports, and variable filters. A port in the multiplexer is connected to an antenna. A port in the circulator is connected to a port in the multiplexer. The reception ports are connected to a port in the circulator with the variable filters interposed therebetween. The multiplexer outputs a communication signal having a frequency in a low band to the port and outputs a communication signal having a frequency in a middle band to a port. Each of the low band and the middle band includes a plurality of frequency bands. The middle band is a range of frequencies higher than those in the low band and does not overlap the low band.