• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.4
• /
• pp.325-331
• /
• 2002

In this paper, surface acoustic wave(SAW) bandpass filters using slanted finger interdigital electrode transducers(IDTs) are 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. For the filter design, input-output IDT structure was simulated with modified impulse model; uniform-withdrawal weighting IDTs, withdrawal-withdrawal weighting IDTs. SAW filters of uniform-withdrawal weighting IDTs structure were designed and fabricated on $128^{\circ}LiNbO_3$ piezoelectric substrates. Implemented SAW filter has a fractional bandwidth of 30%, center frequency of 70MHz and shape factor of $1.12\pm0.01$.

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

• The Journal of the Acoustical Society of Korea
• /
• v.18 no.4
• /
• pp.23-30
• /
• 1999

In this study, we propose a new optimization algorithm for a withdrawal weighted SAW transversal filter to satisfy given, specifications such as bandwidth, ripple, insertion loss, and sidelobe rejection level. An analysis tool for the withdrawal weighted filter has been produced by means of the delta function model, and has been applied to the design of a filter consisting of an uniform input IDT and a withdrawal weighted output IDT. This optimization algorithm consists of three routines, which eventually determines eight design parameters to satisfy the performance specifications. At the first step, the number of input and output IDT fingers and their geometrical size are determined by the insertion loss specification. At the next step, the bandwidth is controlled by the change of the IDT finger position. Finally, the sidelobe rejection level is modified through the add/skip technique of IDT fingers. The algorithm in this paper is distinct from conventional techniques in that it can simultaneously consider all the specifications such as bandwidth, ripple, sidelobe rejection level and insertion loss, and optimize the geometry of the withdrawal weighted SAW filter.

• 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.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.1
• /
• pp.47-55
• /
• 2002

This paper proposes a new improved lumped element equivalent circuit analysis method to analyze withdrawal weighted SAW resonators of irregular electrode configurations, which enables to calculate the frequency response of withdrawal weighted SAW resonators. This method has led to the derivation of Smith equivalent circuit's y-parameters for a single ground electrode and formulated the resonator's admittance by calculating the total current into an IDT assembly. To illustrate the effectiveness of the technique, this method was applied to the design of a simple ladder filter and the change of the filter performance was investigated in relation to the weighting of the series and parallel resonators, respectively. The results shows that the withdrawal weighted resonator ladder filters provide better performance in their bandwidth and transition characteristics than normal ones. This new equivalent circuit analysis method can also serve as a better tool to design and analyze general SAW resonator filters.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.2
• /
• pp.307-315
• /
• 2005

We have studied to obtain the SAW filter for the passband was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have performed to obtain the properly design conditions about phase shift of the SAW filter for WCDMA. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000$\AA$ and 3.6$mu$m, respectively. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 8.2MHz. And we could obtain that return loss is less then 16dB, ripple characteristics is probably 4dB and triple transit echo is less then 18dB after when we have matched impedance.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.3
• /
• pp.602-608
• /
• 2005

We have studied to obtain the SAW filter for the Single Phase Unidirectional Transduce. (SPUDT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulations. Also, we have performed to obtain the properly conditions about impedance matching of the SAW filter for SPUDT. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000A and $3.6{\mu}m$, respectively. And the width of IDT' fingers is $2.4{\mu}m$, and the space between IDT' finger and reflector is $2.0{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.7MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.4dB and standing wave ratio is probably 1.5 after when we have matched impedance.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.5
• /
• pp.69-75
• /
• 2001

In this paper, a fast and easy impedance matching method, which could give the impedance matching component for the general 1 or 2-port network was introduced. First, the entire network structure was defined which consists of the network part to be matched and the impedance matching part composed of inductors and capacitors. Next, the transmission matrix and input and output impedances of the entire network from the terminal impedance conditions were calculated, then the exact solutions for the matching components were obtained. To verify the efficiency of this method, this method was applied to the CDMA If band withdrawal weighted SAW transversal filter, and investigated the effects of the impedance matching before and after, through the simulation and experiment. As the result, the performance of a fractional bandwidth of 1.2%, insertion loss of 29 dB, and VSWR of 80 have improved to a factional bandwidth of 1.8％, insertion loss of 9 dB, VSWR of 3 at 85.38 MHz center frequency. The result shows that this impedance matching method could be used in the SAW devices and other types of 1 or 2-port network.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.3
• /
• pp.699-706
• /
• 2010

We have studied to obtain the slanted finger interdigital(SFIT) type filter was formed on the Langasite substrate and was evaporated two IDT electrode by Aluminum-Copper alloy respectively. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have performed to obtain the properly design conditions about phase shift conditions of the SPIT type filter. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflectors are $5000\;{\AA}$ and $3.6{\mu}m$ respectively. At the first sample, we have employed that the distance from the hot electrode to the reflectors is $2.4{\mu}m$ distance from the ground electrode to the reflectors is $1.8{\mu}m$ and the distance from the hot electrode to the ground is $1.5{\mu}m$ respectively. At the other sample, we have also employed that the distance from the hot electrode to the reflectors and the distance from the ground electrode to the reflectors are $2.4{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.3 MHz. And we could obtain that return is less than -20dB, ripple characteristics is probably 3dB and triple transit echo(TTE) is less than -22dB after when we have matched impedance.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.10
• /
• pp.1916-1923
• /
• 2007

We have studied to obtain the SAW filter for the passband was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and thin we performed computer-simulated by simulator. We cm fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have performed to obtain the properly design conditions about phase shift of the SAW filter for WCDMA. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are $5000\;{\AA}$ and $3.6{\mu}m$ respectively. And we have employed that the distances from the hot electrode to the reflector are $2.0{\mu}m$, $2.4{\mu}m$ and the distance from the hot electrode to the ground is $1.5{\mu}m$ respectively. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7,8MHz. And we could obtain that return loss is less then -18dB, ripple characteristics is probably 3dB and triple transit echo is less then -25dB after when we have matched impedance.