Branching Filter with Unified Piezoelectric Substrate
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Solution Overview
Problem
Existing branching filters containing receiving and transmitting bandpass filters are large in size due to the separate piezoelectric substrates for each filter, limiting height reduction and requiring additional space for surface acoustic wave excitation, while boundary acoustic wave filters are inferior in power resistance.
Innovation Solution
A branching filter design that unifies receiving and transmitting filter chips with piezoelectric substrates and insulating layers, using metal plating films for conductors to reduce size and height, and incorporates inductance components for improved performance, with a method involving layer formation and electroplating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate piezoelectric substrates are used for receiving and transmitting bandpass filters, then each filter can be optimized for its specific frequency characteristics, but the overall branching filter size and height increase
Solution Approach 1:
The patent merges the receiving and transmitting bandpass filters onto a single piezoelectric substrate, eliminating the need for separate substrates. This integration reduces the overall height and size of the branching filter while maintaining the distinct frequency characteristics of each filter through separate filter chip designs on the same substrate.
2Reliability
If surface acoustic wave filters are used for both receiving and transmitting bandpass filters, then frequency characteristics can be optimized, but additional space is required for surface acoustic wave excitation
Solution Approach 1:
The patent applies local quality by using boundary acoustic wave filters for the transmitting bandpass filter and surface acoustic wave filters for the receiving bandpass filter. This allows each filter type to be optimized for its specific function while minimizing the overall area required, as boundary acoustic wave filters do not require the same space for wave excitation as surface acoustic wave filters.
3Length of stationary object
If boundary acoustic wave filters are used, then height can be reduced, but power resistance deteriorates
Solution Approach 1:
The patent uses boundary acoustic wave filters specifically for the transmitting bandpass filter where lower height is critical, accepting the trade-off in power resistance. For the receiving bandpass filter, surface acoustic wave filters are used which provide better power resistance. This localized application of different filter types optimizes the overall system performance.
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
The unified filter structure reduces the size and height of the branching filter while maintaining desired properties and shock resistance, enhancing power resistance and mechanical stability.
Implementation Method 1
a first piezoelectric substrate, at least one IDT disposed on the upper surface of the first piezoelectric substrate
Implementation Method 2
a conductor having one end connected to the external terminal and other end electrically connected to the IDT, the conductor including a plating film
Data Source
Figure 1(a)~1(g)
Figure 2(a)~2(d)
Figure 3(a)~3(c)
AI summary
A branching filter capable of being reduced in size, particularly height, is provided. The branching filter has a configuration in which a transmitting filter chip and a receiving filter chip include a first piezoelectric substrate (1) and a second piezoelectric substrate (3), respectively, and are spaced from each other; the transmitting filter chip includes a first insulating layer (9) which extends over an IDT (2) or which is disposed above the IDT (2); the receiving filter chip includes a first insulating layer (10) which extends over an IDT (4) or which is disposed above the IDT (4); the upper surfaces of the transmitting and receiving filter chips are covered with a second insulating layer (14); external terminals (22) arranged on the upper surface of a third insulating layer (20) are electrically connected to the IDTs (2) and (4) through conductors (15, 16) extending through the first insulating layers (9, 10) and the second insulating layer (14); and the conductors (15, 16) include plating films.