Degenerated coupled resonator filters

Plessky, V.P.; Thorvaldsson, T.; Kondratiev, S.N.

doi:10.1109/ultsym.1996.583775

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…2%), low-loss filters on leaky-wave substrates. Because the operation of the device is based on the strong resonance arising in the gap region, we conclude that the unsatisfactory performance reported previously in [5] was due to the attenuation in the gap. In the devices studied in this paper, the loss mechanisms in the gap are considerably reduced with the use of distributed gaps, resulting in excellent filter characteristics with minimum IL of 1.07 dB.…”

Section: Discussionmentioning

confidence: 63%

“…A similar device with improved loss levels was later realized by Hong [6]. The topology studied in the present work is similar to that presented in [5], except for gaps that are replaced with distributed gaps, i.e., the phase change conventionally occurring in a metallized gap is realized with short transducer sections. The pitch of the short IDTs is selected so that the necessary phase shift is obtained; typically it should be smaller than in the main IDTs so as to avoid generation of bulk-acoustic waves (BAW) [4], [7].…”

Section: A Double-resonance Structurementioning

confidence: 89%

“…Therefore, care must be taken to counteract the loss mechanisms in the gap region, as they have a significant effect on the operation of the device. In a metallized or free-surface gap, the conversion of SAW into BAW at the edges of periodic structures and propagation loss occurring on the surface of the gap (especially important on 42 • -LiTaO 3 [9]) attenuate the resonance, deteriorating the performance of the filter, and leading to such difficulties as reported in [5].…”

Section: A Double-resonance Structurementioning

confidence: 99%

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Double-resonance SAW filters

Meltaus¹,

Hong

Holmgren³

et al. 2007

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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A novel surface acoustic wave filter on a leakywave substrate is studied. It features a hiccup-type resonance occurring around a distributed gap between two long interdigital transducers. Compared to a classical coupled resonator filter, it enables a relatively narrow passband (1% to 2% of center frequency) with low insertion loss, steep skirts, and improved suppression levels. The structure consists of long transducers having the number of fingers greater than 1=K 2 and 1= , where K 2 is the coupling coefficient of the substrate material and is the reflectivity per wavelength, separated with short transducer sections constituting a distributed gap. A strong, localized resonance is formed in the gap region, in addition to the resonance arising in the long structures-hence, the name doubleresonance filter. The substrate studied here is 42 -rotated lithium tantalite. We show experimental results for both single-ended and unbalanced-to-balanced filters at 1.6 GHz, having a minimum insertion loss of 1.07 dB, suppressions of 30 dB, and absolute ;3-dB bandwidth of 29 MHz (1.9% of the center frequency). For the balanced device, the amplitude imbalance over the passband ranges from ;0.6 dB to 2 dB and the phase imbalance from 1 to 4.5 . Furthermore, we have measured the acoustical power distributions using a scanning laser interferometer, and we compare these results with the profiles simulated using a coupling-of-modes model.

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Section: Discussionmentioning

confidence: 63%

Section: A Double-resonance Structurementioning

confidence: 89%

Section: A Double-resonance Structurementioning

confidence: 99%

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Double-resonance SAW filters

Meltaus¹,

Hong

Holmgren³

et al. 2007

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…These resonances resemble "hiccup" resonances occurring in λ/4-gaps in synchronous resonators [3], [4]; therefore, throughout this paper they are referred to as hiccup resonances. A similar structure was first proposed by Plessky et al [5], but due to losses occurring in metallized gaps, the performance of realized devices was not satisfactory. If the losses in the gap are reduced by replacing the metallized gap with short IDT sections (distributed gap), low-loss, narrow-band filter operation with fast transition to rejection band and high rejection levels can be obtained on strong piezoelectric substrates, such as 42 • -LiTaO 3 [1].…”

Section: Introductionmentioning

confidence: 85%

6H-6 High-Suppression SAW Filters Based on Double-Resonance Structure

Meltaus

Hong²,

Plessky³

2006

2006 IEEE Ultrasonics Symposium

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A novel type of surface acoustic wave bandpass filter is presented. The operation of the device is based on the doubleresonance filter structure in which relatively long interdigital transducers (IDTs) are coupled acoustically. The filter consists of 3 main IDTs on a leaky-wave 42 • -LiTaO3 substrate, separated by short IDT sections with a reduced period (distributed gaps). Electrical input signal is connected to one of the side IDTs and electrical output to the other. The middle IDT is either left open (floating) or grounded. If the middle IDT is floating, acoustic energy is transferred from input to output by the resonances created in the gaps, corresponding to two 2-IDT filters cascaded. When the middle IDT is grounded, it effectively blocks the acoustic wave propagation from input to output. Therefore, the filter can be switched off by grounding the middle IDT. The device features a 3-dB relative bandwidth of ∼2% at 1575 MHz, with relatively low insertion loss (IL) in the passband, steep transitions and high rejection levels. Experimental results show minimum IL of 3.1 dB in the filter passband and suppressions on the order of -50 dB (after removal of electromagnetic feedthrough), with a relative -3-dB bandwidth of 27 MHz (1.7% of center frequency).

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“…A hiccup-type structure with long IDTs and a λ/4 metallized gap on a leaky substrate was proposed in 1996 by Plessky et al [3]. Although simulations promised excellent filter performance, experimental devices on 36°-LiTaO 3 showed unexpectedly high insertion loss in the passband and strong ripple on the transfer curve.…”

Section: Hiccup-type Double-resonance Resonators On Leaky-wave Sumentioning

confidence: 99%