LTE B41 RF Filter Switching for Full-Band Coverage
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Solution Overview
Problem
Conventional mobile terminals face high costs and compatibility issues when implementing a full frequency band for the B41 frequency band, particularly due to the high cost and larger size of BAW filters required for overseas areas, which are not compatible with the smaller SAW filters used in domestic areas.
Innovation Solution
A mobile terminal design that expands the bandwidth of the B41 frequency band by using a radio frequency transceiver, multimode multiband power amplifier, duplexer, first SAW filter, and selection module to selectively route signals through either a duplexer or a SAW filter, allowing for the coverage of the full frequency band without the need for expensive BAW filters, and enabling compatibility with existing circuit designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a BAW filter is used to support the full frequency band of 194 MHz in the B41 frequency band, then the frequency band coverage is improved, but the cost and size increase significantly
Solution Approach 1:
The B41 frequency band is divided into three segments: B41U (uplink), B41D (downlink), and B41C (combined). Each segment is handled by different filter configurations - SAW filters for domestic B41C band and duplexer for overseas extended bands, avoiding the need for a single large BAW filter to cover the entire 194 MHz range
Solution Approach 2:
The duplexer designed for B7 frequency band is made multi-functional by enabling it to handle both B7 and B41 frequency bands. The same duplexer structure serves dual purposes: filtering B7 signals and extending B41 frequency coverage in overseas markets, eliminating the need for separate BAW filters
2Device complexity
If a SAW filter with bandwidth of 100 MHz is used for domestic B41 frequency band, then the cost is reduced, but the frequency band coverage is limited
Solution Approach 1:
The patent merges the functionality of separate filters by enabling the duplexer to handle multiple frequency bands (B7 and B41). The SAW filter covers domestic B41C band while the duplexer extends coverage to overseas B41U and B41D bands, combining their capabilities to achieve full B41 band support without requiring expensive BAW filters
3Adaptability or versatility
If a BAW filter is used to support full frequency band in overseas area, then the frequency band compatibility is improved, but the compatibility with existing SAW filter circuits is lost
Solution Approach 1:
The system dynamically selects between different filter configurations based on the operating region. In domestic areas, the SAW filter is used for B41C band with existing circuitry. In overseas areas, the duplexer is activated to handle B41U and B41D bands, providing frequency band compatibility while maintaining circuit compatibility through software-controlled switching
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 significantly reduces the cost of the circuit by using low-cost SAW filters and maintains compatibility with existing domestic SAW filter sizes, enabling efficient coverage of the full B41 frequency band without the need for circuit redesign or replacement of filters.
Implementation Method 1
a surface acoustic wave (SAW) filter having a bandwidth of 100 MHz (2555 MHz-2655 MHz) is used for a B41 frequency band
Implementation Method 2
A signal in the B7 frequency band received by the TXM module is transmitted to the duplexer in the B7 frequency band
Implementation Method 3
the multimode multiband power amplifier is configured to amplify a power of the initial signal
Data Source
AI summary
A mobile terminal and a method for expanding a bandwidth of a B41 frequency band in LTE are disclosed. The mobile includes a multimode multiband power amplifier, a duplexer, a first surface acoustic wave (SAW) filter, a selection module, and a radio frequency transmission module. When the multimode multiband power amplifier identifies that the initial signal is a signal in the B41 frequency band, the multimode multiband power amplifier determines a frequency band range of the signal in the B41 frequency band and outputs a transmitting signal in the B41 frequency band.