Duplexer Filter Topology for Wideband Compact RF Modules
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Solution Overview
Problem
Existing duplexers face challenges in achieving high bandwidth and compactness due to the need for multiple inductances with increasing filter stages, and limited bandwidth increase when inductances are connected only to parallel resonators.
Innovation Solution
A duplexer configuration that includes series and parallel resonators with an inductance connected in series to at least one parallel resonator, where the antiresonance frequency of the parallel resonator is equal to or higher than the antiresonance frequency of the series resonators, allowing for wider bandwidth without degrading middle band characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If inductances are connected to each of series resonators and parallel resonators in series to expand the frequency difference between resonance and antiresonance, then wider bandwidth is achieved, but the number of inductances increases and the filter chip cannot be made compact
Solution Approach 1:
The invention extracts the inductance connection from series resonators while maintaining it in parallel resonators. Specifically, the patent removes the series connection of inductances with series resonators (S1-S4) that was present in the conventional configuration, while keeping the series connection with parallel resonators (P1-P4). This selective removal reduces the total number of inductances from 8 to 4, achieving compactness while maintaining the bandwidth expansion benefit through the parallel resonator inductances.
Solution Approach 2:
The invention segments the inductance application by type of resonator. Instead of uniformly connecting inductances to all resonators, the patent applies inductances only to parallel resonators (P1-P4) and omits them from series resonators (S1-S4). This segmentation allows differential treatment of resonator types, optimizing the balance between bandwidth expansion and component count reduction.
2Device complexity
If inductances are connected only to parallel resonators to reduce the number of inductances and make the chip compact, then compactness is improved, but the bandwidth increase is limited by the series resonator frequency difference
Solution Approach 1:
The invention changes the frequency parameters of parallel resonators by introducing series inductances. The inductances L1-L4 connected to parallel resonators P1-P4 shift their resonance frequencies to lower values, thereby expanding the frequency difference between resonance and antiresonance frequencies. This parameter change enables the parallel resonators to provide wider bandwidth contribution, compensating for the removal of inductances from series resonators.
3Reliability
If the number of filter stages is increased to improve suppression characteristics, then suppression performance is improved, but the number of inductances increases and compactness is compromised
Solution Approach 1:
The invention extracts unnecessary inductances from series resonators while maintaining the filter stages for suppression performance. The patent removes inductances from series resonators (S1-S4) but preserves the parallel resonator stages (P1-P4) with their inductances, maintaining the ladder filter structure needed for suppression while reducing overall component count.
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 configuration enables a compact and cost-effective duplexer with wideband characteristics while maintaining low loss, as the inductance is only connected to the parallel resonator, reducing the number of inductances needed and ensuring impedance matching within the passband.
Implementation Method 1
an inductance that is connected in series to at least one of the parallel resonators
Implementation Method 2
resonance frequencies of the resonators to the lower frequency side
Implementation Method 3
an antiresonance frequency of the parallel resonator to which the inductance is connected in series
Data Source
AI summary
The filter includes one or more series resonators and one or more parallel resonators. An inductance is connected in series to at least a parallel resonator of the parallel resonators, and a antiresonance frequency of the parallel resonator to which the inductance is connected in series is equal to or higher than that of the series resonators. The duplexer, the communication module and the communication device are provided with the filter.