• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.241-244
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• 2001

The design and fabrication of the surface acoustic wave(SAW) bandpass filters using slanted finger interdigital electrode transducers(IDTs) is investigated. The slanted finger IDTs are used to design SAW filters with good shape factor, a flat passband, and good out-of-band rejection characteristic. The slanted finger IDTS filter was simulated of three kind of IDTs structure. uniform-uniform IDT, uniform-withdrawal weighting IDTS, withdrawal weighting-withdrawal weighting IDTS. Uniform-withdrawal weighting IDTs structure SAW filters was designed and fabricated on 112$^{\circ}$ LiTaO$_3$, 128$^{\circ}$LiNbO$_3$ substrates. Designed SAW filter has about a 30% fractional bandwidth and a 70MHz center frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.40-43
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• 1996

Substrates of SAW filter are mainly single crystal such as LiNbO$_3$, LiTaO$_3$. However, fabrication of crystal is difficult and cost is very high. In this study, crystal was substituted for piezoelectric ceramics which has simple fabrication process. The same SAW filter mask was photolithographed on crystal(LiNbO$_3$) substrate and ceramic(PZT4, PZT5A and PZT8) substrate in order to compare experimental value with theoretical value. The difference of center frequency was only 3.7%. PZT8 showed good bandwidth properties. It is considered that PZT8 has higher mechanical quality factor and propagation velocity than PZT4, PTT5A.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1767-1775
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• 2003

The SAW device is extensively used as a electro$.$mechanical band­pass filter in which a two­pairs of interdigital transducers are provided over the surface of the piezoelectric substrate. For the design requirement, the central frequency and the bandwidth of the passband, and the attenuation level of the stopband region are specified. The configuration is made so as to satisfy the specification given. The central frequency is mainly determined by the distance between the pair of the finger electrodes. The design is considered as an optimization problem with which the error norm, the distance between the desired characteristics and the calculated for a given model is to be minimized. The delta function model and the electrical equivalent circuit model are utilized to represent the SAW filter characteristics. Genetic algorithm is used for optimization in which apodization of the transducer fingers is chosen as a design variable.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.837-840
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• 1987

In this paper, an MSK modulator and MSK matched Filter using SAW component which is small size and can process high Frequency and wide band signals are described. This modulator and matched Filter have been shown applicable to the transmitter and receiver of spread spectrum communication systems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.6
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• pp.37-42
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• 1983

The TV IF SAW filter if designed using the windowing method. The procedure for fabricating SAW filters is described. The filter is fabricated on the Y-cut, Z-propagation LiNbO3 wafer. The passband ripple and the smaller upper sidelobe attenuation are obseryed. Further improvements and the mass production can be expected.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.53-59
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• 1999

Of various SPUDT SAW filter types, we select the two most common types, DART and EWC/SPUDT, and analyze their performance with the Smith equivalent circuit method. Based on the results for an exemplary case, a usual apodized SAW filter, we investigate the advantage of one type over the other, if any, in a quantitative manner. To compensate for the performance degradation that can happen in the process of the modification of the apodized filer to the SPUDT structure, we apply the triangular weighting technique to wide fingers of the IDT. Further, the variation in performance of the SPUDT structure is investigated in relation to its electrode thickness and the number of fingers. The results in this paper are expected to enable us to easily select an SPUDT type appropriate for each particular application field.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.245-248
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• 2001

In this paper, we have investigated the design technique and fabricated the surface acoustic wave (SAW) filter for duplexer, which consists of Tx. and Rx. filter, and antenna terminal. For Tx. and Rx. bandpass filters we used the one-port SAW resonators with n-section ladder structure. The structure is composed of couples of series-arm resonators and parallel-arm resonators. RF filter using ladder structure was designed and fabricated on 36$^{\circ}$Y-X LiTaO$_3$ substrates. Designed filters, insertion loss is less than 1.5dB, the bandwidth is more than 25MHz, rejection band level is less than -30dB and center frequency is 820MHz.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.27-32
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• 1984

In SAW filters with a small aperture, diffraction effect is not negligible and degrades the frequency response near the trap. A computer simulation program for diffraction analysis is developed, and an effective diffraction compensation method is proposed to compensate the diffraction effect. A TV-lF SAW filter was designed with the diffraction taken account by the proposed method, which satisfies given frequency specifications.

• Electrical & Electronic Materials
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• v.10 no.2
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• pp.179-184
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• 1997

고주파화로 진행되고 있는 이동통신에서 사용주파수대가 고주파화로 향해감에 따라, 시스템은 소형화, 고기능화가 요구된다. 이러한 요구상황에 SAW 필터가 부응하기 위해서는 삽입손실 개선, Submicron 전극제작기술, 소형화를 위한 면실장기술 등이 앞으로 해결해 나아가야할 과제라고 생각된다. 이상으로 SAW 필터는 그 우수한 특성으로 앞으로 이동통신용 핵심부품으로 발전해 갈 것으로 생각된다. 이에 발맞추어 새로운 기술 향상과 신규시장에 대응하는 시기 적절한 상품화가 주된 관건이며, 국내업체는 위에 기술한 상황에 신속한 대응이 있어야만 세계 시장경쟁에서 살아남을 수 있을 것이라 생각된다.

• The Journal of the Acoustical Society of Korea
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• v.18 no.1
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• pp.10-15
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• 1999

We have studied a method to design and fabricate the Intermediate Frequency(IF) band pass filter with low shape factor which is used for CDMA base station on the 35°Y-cut X-propagation Quartz substrate. In order to fabricate a device of the low shape factor for the IF SAW filter on this substrate, we employed apodization weighted type interdigital transducer(IDT) as an input and withdrawal weighted type IDT as an output by using impulse modelling method. Also, using the Kaiser-Bessel window function, we have adopted 2200pairs and 1000pairs of input and oueut IDT respectively to minimize the effect of ripple. Furthermore, the width and the space of IDT finger are 3.6 ㎛ and 3.5 ㎛ respectively. Thus, we can have optimal results when the IDT thickness is 6000Å in consideration of the ratio of SAW's wavelength while it's aperture is 2mm for impedance matching. The fabricated SAW filter for CDMA had the property of almost 115.2MHz of a center frequency, less then 1.27MHz of bandwidth, less than 1.3 of shape factor, - l5dB of out band attenuation insertion loss and -45dB of rejection band.