Multiplexer Impedance Matching via Direct Filter Connection
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Solution Overview
Problem
Existing multiplexers with acoustic wave filters face increased insertion loss and circuit size due to the requirement of large inductance values to shift impedance to the inductive region, leading to higher propagation loss and increased return loss in certain frequency bands.
Innovation Solution
A multiplexer configuration with first and second common connecting terminals and an inductance element, where the first acoustic wave filter is directly connected to one terminal without the inductance element, and the second and third filters are connected to the other terminal, allowing for improved impedance matching and reduced insertion loss by using a complex-number conjugate relationship between the filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large inductance value is used to shift the impedance of the first receive filter to the inductive region, then the impedance matching between filters is improved, but the propagation loss in the path including the first receive filter increases and the circuit size increases
Solution Approach 1:
The patent changes the connection configuration parameter of the acoustic wave filters, specifically connecting the first receive filter directly to the common terminal without a series inductance element, while connecting other filters through the inductance element. This parameter change allows achieving impedance matching without requiring large inductance values, thereby reducing propagation loss.
2Reliability
If a large inductance value is used to shift the impedance of the first receive filter to the inductive region, then the impedance matching between filters is improved, but the circuit size increases
Solution Approach 1:
The patent modifies the connection configuration parameter by removing the series inductance element from the first receive filter path. This parameter change eliminates the need for large inductance elements, thereby reducing the overall circuit size while maintaining impedance matching through the alternative configuration where other filters are connected through the inductance element.
3Reliability
If the absolute value of the reactance components of the first receive filter becomes smaller than that of the initial impedance, then the return loss of the first receive filter increases, but the insertion loss of the different filter also increases
Solution Approach 1:
The patent inverts the conventional connection approach by connecting the first receive filter directly to the common terminal without the inductance element, while connecting other filters through the inductance element. This inverted configuration prevents the degradation of both return loss and insertion loss that occurs in the conventional approach.
Data Source
AI summary
A multiplexer includes first and second nodes, an inductor, a first transmit/receive filter, and second and third transmit filters. The inductor is connected at one end to the first node and at the other end to the second node. The first transmit/receive filter is connected to the first node without the inductor interposed therebetween and uses the transmit and receive bands of band A as a pass band. The second transmit filter is connected to the second node and uses the transmit band of band B as a pass band. The third transmit filter is connected to the second node and uses the transmit band of band C as a pass band.