2006 Fiscal Year Final Research Report Summary
Research on the design of SAW filters for a duplexer based on network theory
| Project/Area Number |
16560339
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Communication/Network engineering
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| Research Institution | Waseda University (2005-2006)
Kyushu University (2004) |
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Principal Investigator |
NISHI Tetsuo Waseda University, Faculty of Science and Engineering, Professor, 理工学術院, 教授 (40037908)
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| Co-Investigator(Kenkyū-buntansha) |
OGATA Masato Kyushu Sangyo Institute of Technology, Lecturer, 工学部, 講師 (90325548)
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| Project Period (FY) |
2004 – 2006
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| Keywords | portable telephone / SAW filter / lumped-constant model / duplexer / π-type inductance / ladder type SAW filter / π形インダクタンス |
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| Research Abstract |
The aim of this research is to develop the design method of SAW filters, which is usually used in the duplexer of portable phones. A SAW element is a kind of electro-mechanical transducers utilizing the surface acoustic wave, can be manufactured in very small size, and has very high Q (about 800). The characteristics of SAW elements can be modelled by distributed-constant circuits. The use of SAW elements enables high Q bandpass filters with sharp cutoff characteristics for 800Mhz frequency band. The filter has to possess large attenuation at higher frequency band (or lower frequency band) of the passband due to the requirement for duplexers. We use the circuit-theoretic approach for the design.
1. Let T(s)=N(s)/D(s) be a transfer function of a SAW filter. We proposed a design method of filter characteristics T(s) with equiripple attenuation characteristics in the stop band and has the maximally flat passband characteristics.
2. We proposed a design method of SAW filters, (1) which has symmetrical structure, (2) which are composed not only of SAW elements but also lumped-constant inductances. Then the network is modelled as a mixed lumped-and distributed-network and therefore is difficult to analyze and design it.
The π-type or Y-type inductances are placed with a conventional SAW ladder filter. We investigated in detail the effects of inserted inductances for the attenuation frequency bands and showed that the Y-type is better for the analysis and synthesis.
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Research Products
(12 results)
