• Journal of electromagnetic engineering and science
• /
• v.6 no.2
• /
• pp.110-116
• /
• 2006

A reflective array type surface acoustic wave(SAW) dispersive delay line(DDL) with high time-bandwidth at the V/UHF-band is designed and fabricated for compressive receiver applications. This type of the SAW DDL has the properties of the relative bandwidth of 20 %, the time delay of 49.89 usec, the insertion loss of 38.5 dB and the side lobe rejection of 39 dB. In comparison with a commercial SAW DDL, the insertion loss, amplitude ripple and side lobe rejection are improved by $1.5dB{\pm}0.6dB$ and 4 dB respectively. Using the fabricated SAW DDL, the prototype of the compressive receiver is developed. It is composed of RF converter, fast tunable LO, chirp LO, A/D converter, signal processing unit and control unit. This prototype system shows a fine frequency resolution of below 30 kHz with high scan rate.

• The Journal of the Acoustical Society of Korea
• /
• v.18 no.4
• /
• pp.53-59
• /
• 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
• /
• 1998.10a
• /
• pp.31-34
• /
• 1998

CDMA base station SAW filter has been designed and fabricated successfully. Through the computer simulation, SAW filter is designed to have center frequency of 69.99MHz, ripples lower than 0.7dB and rejection level lower than 50dB. To obtain low noise band pass SAW filter, Input electrode has a apodization type and output electrode has a withdrawal type. For the fabrication of the SAW filter, Al thin film is deposited to the quartz substrates. The fabricated SAW filter has center frequency of 70.5MHz, ripples of 1dB and rejection level of 45dB.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.7
• /
• pp.647-655
• /
• 2003

Commonly used SAW duplexers have a difficulty on manufacture so that a transmission line is printed on the package or an LTCC multi-layer is needed because a quarter-wave transmission line which is a kind of an isolation network is applied to the SAW duplexers. In this study, new structures of one chip type SAW duplexers are proposed. In the proposed structure, Tx and Rx SAW ladder filters and isolation networks are located on a single 36LiTaO$_3$ piezoelectric substrate. The manufacture process is very simple than commonly used product. It is possible to improve tile performance by means of optimizing the micro-strip line lumped elements. It is easy to integrate and modulate with other surrounding components. The optimal design techniques can be applied to other kind of multi-port devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.1
• /
• pp.85-92
• /
• 2002

In this study, we analyzed and experimented micro-strip line inductors and capacitors for a SAW duplexer, an important devise for mobile communication. For SAW duplexers, micro-strip line lumped elements must have small impedance values, below several tens of nH or several tens of pF, and a small area pattern. In this study, we performed theoretical analysis of flat line type, meander line type, and spiral line type inductors and interdigital capacitors on a LiTaO$_3$ Piezo-crystal. We proposed a measurement method to evaluate small values of lumped elements accurately with network analyzer. In experiments, we confirmed validity of the theoretical analysis method through fabrication and characterization of micro-strip line lumped elements. The analysis method in this paper can be applied to SAW duplexers well as other microwave devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.5
• /
• pp.435-443
• /
• 2001

As power durable RF SAW filters, AL-(0∼2wt%)Cu alloy multi-layered thin electrodes were deposited on 42° LiTaO$_3$ piezoelectric substrates by magnetron sputtering process, and then ladder-type RF SAW filters, satisfying the electrical specification of CDMA transmission band, were fabricated through optimizing SAW resonator structures. The temperature of film electrodes in SAW filter was increased with RF power, and reached the maxima to cause a failure of SAW filters at the cut-off frequencies of the RF filter band. As RF power increases, the electrodes of Al-Cu alloy showed higher power durability than that of pure Al. The multi-layer laminated film of Al-1wt.% Cu/Cu/Al-1wt%Cu resulted in the best power durability up to 4W of RF power. Every film electrode, however, was destroyed within seconds whenever applying a critical RF power to SAW filters, regardless of the composition and structure of film electrodes. The breakdown of film electrodes under FR power seems to believe due to the fatigue of electrodes caused by repetitive cyclic stress of surface acoustic wave, which is amplified as RF power increases.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1985.10a
• /
• pp.72-74
• /
• 1985

In this work we describe a new type of SAW FM discriminator which is structurely single layer planar type and uses the elastic nonlineatity compared with acoustoelectric SAW FM discriminator. This device shows successful FM discrimination of among as well as digital signals.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.2
• /
• pp.102-109
• /
• 2002

This paper proposes a new design algorithm to optimize the withdrawal weighted SAW ladder devices, Withdrawal weighting on SAW resonators gives enhanced bandwidth and transition band characteristics, so an optimization algorithm was developed for ladder type SAW filters. To illustrate the validity of the technique, this method was applied to the design of RF band CDMA TX SAW filters, and the design results were confirmed to show good agreement with experimental performance.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.359-362
• /
• 1999

본 연구에서는 작은 삽입손실을 구현하기 위해 적용되는 SPUDT 중에서 현재 가장 널리 사용되고 좋은 성능을 가지는 DART와 EWC/SPUDT형 SAW 필터에 대해서 그 효용성을 Smith 등가회로 해석법을 이용하여 분석하였다. 그리고 apodization weighting된 SAW 필터에 단순히 SPUOT를 적용하였을 때 발생하는 일부 특성열화를 보상하기 위한 방법으로, 이 두 종류 SPUDT의 폭이 넓은 전극에 대한 weighting을 독립적으로 행하였고 전극두께를 조절하여 성능변화를 보았다. 그 결과로 동일 전극길이를 갖는 경우에는 EWC/SPUDT형 SAW 필터가 DART형 SAW 필터보다 삽입손실이 더 작으나 리플이 크고, apodization weighting된 SAW필터에 SPUDT를 적용한 경우에는 전반적으로 DART형 SAW 필터가 EWC/SPUDT형 SAW 필터보다 우수한 성능을 가지는 것으로 나타났다. 본 연구의 결과는 특정 형태의 SAW 필터에 SPUDT를 적용하는 문제에 있어서 적절한 SPUDT의 타입을 결정하는데 도움을 주리라 기대된다.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.10
• /
• pp.72-79
• /
• 2021

A circular saw is an effective tool for cutting glass and carbon-fiber hybrid composites. This study investigated tool wear and cut quality when reusing saw blades. The carbide saws wear four times faster than the new ones, and polycrystalline diamond (PCD) is very resistant to tool wear, except at the end of its lifespan. The cut cross-section quality is affected by the blade type, tool wear, and spindle speed. Alternate top bevel (ATB)-type blades are suitable for cutting fiber-reinforced plastics, but triple-chip grind (TCG)-type blades are unsuitable because they cause fiber-pullout defects. Tool wear and low spindle speeds increase the occurrence of arc scratches, due to the rear saw blade. A microscopic examination showed that the burr, which is a mixture of fiber chips and epoxy matrix, was bonded on top, and glass-fiber delamination occurred on the bottom glass-fiber-reinforced polymer (GFRP) surface.