An air-gap type FBAR was designed using Leach equivalent model for analyzing a vertical structure of the FBAR. For the top electrode, Pt, and the bottom electrode, Au, of $1.2{\mu}m$ thickness and the piezoelectric of 0.8,urn thickness, the resonance and anti-resonance occurred at 2.401 G...
An air-gap type FBAR was designed using Leach equivalent model for analyzing a vertical structure of the FBAR. For the top electrode, Pt, and the bottom electrode, Au, of $1.2{\mu}m$ thickness and the piezoelectric of 0.8,urn thickness, the resonance and anti-resonance occurred at 2.401 GHz and 2.460 GHz, respectively. $S_{11}$ was increased and $S_{21}$ was decreased as the resonance area of FBAR was widened. We observed the characteristics of insertion loss, bandwidth and out-of-band rejection of ladder-type FBAR BPF by changing resonance areas of series and shunt resonators and by adding stages. As the resonance area of series resonator was increased, insertion loss was improved but out-of-band rejection was degraded. And as the resonance area of shunt resonator was increased, insertion loss was degraded a little but out-of-band rejection was improved even without adding stages. We, also, changed the shape of the resonance area from square shape to rectangle shape to examine the effects of the resonator shape on the characteristics of the BPF. The best performances were observed when the sizes of series and shunt resonator are $150{\mu}m{\times}l50{\mu}m\;and\;5{\mu}m{\times}50{\mu}m$, respectively. Out-of-band rejection was improved about 10dB and bandwidth was broadened from 30MHz to 100MHz utilizing inductor tuning on $2{\times}2\;and\; 4{\times}2$ ladder-type BPFs.
An air-gap type FBAR was designed using Leach equivalent model for analyzing a vertical structure of the FBAR. For the top electrode, Pt, and the bottom electrode, Au, of $1.2{\mu}m$ thickness and the piezoelectric of 0.8,urn thickness, the resonance and anti-resonance occurred at 2.401 GHz and 2.460 GHz, respectively. $S_{11}$ was increased and $S_{21}$ was decreased as the resonance area of FBAR was widened. We observed the characteristics of insertion loss, bandwidth and out-of-band rejection of ladder-type FBAR BPF by changing resonance areas of series and shunt resonators and by adding stages. As the resonance area of series resonator was increased, insertion loss was improved but out-of-band rejection was degraded. And as the resonance area of shunt resonator was increased, insertion loss was degraded a little but out-of-band rejection was improved even without adding stages. We, also, changed the shape of the resonance area from square shape to rectangle shape to examine the effects of the resonator shape on the characteristics of the BPF. The best performances were observed when the sizes of series and shunt resonator are $150{\mu}m{\times}l50{\mu}m\;and\;5{\mu}m{\times}50{\mu}m$, respectively. Out-of-band rejection was improved about 10dB and bandwidth was broadened from 30MHz to 100MHz utilizing inductor tuning on $2{\times}2\;and\; 4{\times}2$ ladder-type BPFs.
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제안 방법
There have been several approaches to constructing FBAR filters[ll]. In this study, we have investigated the ladder filter configuration, which uses series and shunt FBARs. To design such filters, we have used the equivalent-circuit representation previously described for AIN FBAR.
The purpose of this study is to investigate the relationship between the area of resonance and the center frequency by analyzing the characteristics of 2-port resonator. This was done by ideal design using Leach model which is the modified Mason model and equivalent circuit for the application of resonator bandpass filter at high-frequency band.
Using the above results, we estimated the characteristics of ladder-type FBAR filters prior to designing BPFs. The loss was induced from electrical resistance and parasitic components regardless of the connecting type of FBARs.
이론/모형
The purpose of this study is to investigate the relationship between the area of resonance and the center frequency by analyzing the characteristics of 2-port resonator. This was done by ideal design using Leach model which is the modified Mason model and equivalent circuit for the application of resonator bandpass filter at high-frequency band. The changes in bandwidth, insertion loss, and out-of-band rejection as function of the number of resonators and the areas of resonators were, also, observed using FBAR ladder-type BPF.
성능/효과
In general, Sn and S2i of piezoelectric resonator show the opposite tendency with resonance area increases if there is no influence from parasitic components. As a results, changes of these resonance characteristics confirmed numerically that very large decrease of Q value and decrease of Kt2 value were due to parasitic capacitance.
Insertion loss and bandwidth of BPF diversely can be increased by adjusting resonance area, and the influence of parasitic capacitance of BPF was minimized using proper inductor tuning, which can extend pass-band of BPF. The best characteristics were obtained when the sizes of series and shunt resonator are 150 //m><150 //m and 5 ㎛ x50 ㎛, respectively. In addition, out-of-band rejection was improved about 10 dB and bandwidth was broadened from about 30 MHz to about 100 MHz by inductor tuning on 2><2 and 4x2 ladder-type BPF.
Also, the simulation results are summarized in Table 5 and Table 6, respectively. The results showed that the insertion loss of BPF was decreased and the out-ofeband rejection of BPF was increased with inductor tuning. From the results, adjusting resonance area diversely can increase insertion loss and bandwidth of BPF, and pas동-band of BPF can be extended by minimizing the influence of parasitic capacitance using proper inductor tuning.
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