RF Front-End Filter Switching With Phase Adjustment for Multi-Band Links
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Solution Overview
Problem
Existing radio-frequency front-end circuits face challenges in maintaining optimal communication quality during simultaneous communication using multiple frequency bands, due to excessive attenuation in reception and mismatched impedance for transmission.
Innovation Solution
The proposed solution involves a radio-frequency front-end circuit with separate transmit and receive filters, a switch for connecting the antenna to either filter path, and a phase adjusting circuit to minimize phase differences across frequency bands, thereby maintaining communication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single filter is used for both transmission and reception in the same frequency band, then the filter can provide sufficient attenuation for high-strength transmit signals, but it causes excessive attenuation for low-strength receive signals and fails to provide proper impedance matching for power amplifier transmission
Solution Approach 1:
The patent divides the single filter into separate transmit and receive filters, allowing each filter to be optimized for its specific function. The transmit filter is designed with high attenuation characteristics for strong transmit signals, while the receive filter is designed with low attenuation characteristics for weak receive signals, thereby resolving the contradiction between noise attenuation and signal preservation
Solution Approach 2:
The patent applies different filter characteristics to different signal paths based on local requirements. The transmit filter path is designed with high attenuation properties suitable for power amplifier matching, while the receive filter path is designed with low attenuation properties suitable for LNA matching, achieving optimal performance in each local context
2Reliability
If a switch is used to connect the antenna to different filter paths during transmission and reception, then separate optimized filters can be used for each mode, but the phase of signals in different frequency bands changes during switching, causing EVM degradation
Solution Approach 1:
The patent introduces a phase adjusting circuit as an intermediary component between the switch and the signal processing chain. This phase adjusting circuit compensates for the phase changes that occur during switching between transmit and receive modes, thereby maintaining signal integrity and preventing EVM degradation in simultaneous communication
Solution Approach 2:
The patent applies preliminary phase adjustment to counteract the anticipated phase changes that will occur during switching. By pre-adjusting the phase in the opposite direction of the expected phase shift, the system maintains consistent phase relationships and prevents communication quality degradation
Data Source
AI summary
In simultaneous communication using multiple frequency bands, the degradation in the communication quality is suppressed. The radio-frequency front-end circuit (1) includes an antenna terminal (2), a transmit filter (3), a receive filter, a transport filter, a switch (6), and a phase adjusting circuit (7). The switch (6) is capable of connecting the antenna terminal (2) to the transmit filter (3) or the receive filter and the transport filter simultaneously. The transmit filter (3) is disposed on a transmission path (T1). The receive filter is disposed on a reception path. The transport filter is disposed on a transport path. The phase adjusting circuit (7) is disposed on at least one of paths, the transmission path (T1), the reception path, and a reception/transmission path.