US20020096968A1 - Surface acoustic wave resonator filter - Google Patents
Surface acoustic wave resonator filter Download PDFInfo
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- US20020096968A1 US20020096968A1 US10/108,623 US10862302A US2002096968A1 US 20020096968 A1 US20020096968 A1 US 20020096968A1 US 10862302 A US10862302 A US 10862302A US 2002096968 A1 US2002096968 A1 US 2002096968A1
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- acoustic wave
- surface acoustic
- coupling type
- longitudinal
- mode coupling
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
- H03H9/644—Coupled resonator filters having two acoustic tracks
- H03H9/6443—Coupled resonator filters having two acoustic tracks being acoustically coupled
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
- H03H9/6436—Coupled resonator filters having one acoustic track only
Definitions
- the present invention relates to a surface acoustic wave resonator filter. More specifically, the invention relates to a band-pass filter of the type of a surface acoustic wave (SAW) resonator utilizing a longitudinal mode resonance of a surface acoustic wave and having a wide band characteristics.
- SAW surface acoustic wave
- FIG. 7A An equivalent circuit of the conventional two pole mode SAW resonator is illustrated in FIG. 7A. It has been known that such SAW resonator includes two series resonating circuits 11 and 12 having frequencies f 11 and f 12 . The phases of two resonating frequencies f 11 and f 12 are in opposite phase relationship. This opposite phase relationship is equivalently illustrated by a transformer 13 .
- FIG. 8A shows a transversal mode coupling type filter, in which two resonators a and b are proximately arranged longitudinally in perpendicular to the propagating direction of the surface acoustic wave.
- the resonator a has an IDT (interdigital) electrode 1 a at a center and reflectors 3 a and 4 a at both sides of the IDT electrode 1 a.
- the resonator b has an IDT electrode 1 b at the center and reflectors 3 b and 4 b at both sides of the IDT electrode 1 b.
- FIG. 8B shows a longitudinal mode coupling type filter, in which two IDT electrodes 1 and 2 are proximately arranged in the longitudinal direction as the propagating direction of the surface acoustic wave. At both sides of these IDT electrodes 1 and 2 , reflectors 3 and 4 are arranged respectively.
- the band-pass filter characteristics as illustrated in FIG. 7B is obtained by the coupling of two modes generated between the input side IDT electrode 1 and the output side IDT electrode 2 .
- a surface acoustic wave resonator filter includes an interdigital electrode on a piezoelectric substrate, and has a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.
- the two-dimensional coupling type structure may be formed by proximately arranging first and second longitudinal mode coupling type resonators on the piezoelectric substrate for establishing transversal coupling.
- a surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, comprises first and second longitudinal mode coupling type resonators utilizing longitudinal mode resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave, the first and second longitudinal mode coupling type resonators being established a parallel connection between inputs and outputs thereof.
- FIGS. 1A and 1B are illustration respectively showing filter characteristics of the present invention.
- FIG. 2A is an equivalent circuit diagram of a filter according to the present invention.
- FIG. 2B is a characteristic chart of the filter of the invention.
- FIG. 3A is an illustration showing a construction of one embodiment of the present invention.
- FIG. 3B is an illustration showing a construction of another embodiment of the invention.
- FIGS. 4A and 4B show results of actual measurement of filter characteristics of one embodiment of the invention.
- FIGS. 5A and 5B show results of actual measurement of the characteristics in case that another embodiment of the filter according to the invention is used for impedance matching;
- FIGS. 6A and 6B show results of actual measurement of the characteristics in case that another embodiment of the filter according to the invention is used for impedance matching;
- FIG. 7A is an equivalent circuit diagram of the conventional SAW resonator
- FIG. 7B is an illustration of a characteristics of the conventional SAW resonator
- FIG. 8A is an illustration showing a construction of the conventional transversal mode coupling type filter.
- FIG. 8B is an illustration showing a construction of the conventional longitudinal mode coupling type filter.
- the equivalent circuit of the resonators A and B satisfying these essential conditions is as illustrated in FIG. 2A.
- the equivalent circuit of the resonator A has a parallel connection 14 of the series resonating circuit having resonance frequencies f 11 and f 12 .
- the equivalent circuit of the resonator B has a parallel connection of a series resonating circuit having resonance frequencies f 21 and f 22 .
- the output signals the high band side resonance frequency f 12 of the resonator A and the low band side resonance frequency f 21 of the resonator B are to be matched to each other in the vector sense (both in the power and phase). This relationship is illustrated in the transformer 16 .
- the composite resonance characteristics becomes as illustrated in FIG. 2B.
- the filter characteristics with established impedance matching becomes wide band as illustrated in FIG. 1A.
- FIG. 3A The embodiment of the filter construction of the present invention satisfying the above-mentioned characteristics is illustrated in FIG. 3A.
- the shown embodiment is constructed by two sets of longitudinal mode coupling type resonators illustrated in FIG. 8B proximately arranged in the transverse direction and transversal mode coupling being acoustically established between these two resonators.
- the SAW filter according to the invention is designed in a two-dimensional mode coupling type structure by coupling the longitudinal mode resonation in the longitudinal direction as the propagating direction of the surface acoustic wave and the transversal mode resonation in the transverse direction perpendicular to the propagating direction.
- two longitudinal mode coupling type resonators A and B are arranged on a piezoelectric substrate 20 in a cross proximity to each other for permitting acoustical transversal mode coupling.
- AN Input IDT electrode 1 A and a dummy electrode 2 A are arranged in the longitudinal direction.
- reflectors 3 A and 4 A are arranged at respective sides thereof. The IDT electrode 1 A, the dummy electrode 2 A and reflectors 3 A and 4 A form the first longitudinal mode resonator A.
- An output IDT electrode 1 B and a dummy electrode 2 B are also arranged in the longitudinal direction. Reflectors 3 B and 4 B are arranged at respective sides. The IDT electrode 1 B, the dummy electrode 2 B and the reflectors 3 B and 4 B form the second longitudinal mode resonator B.
- the dummy electrodes 2 A and 2 B correspond to a single IDT electrode of the longitudinal resonator illustrated in FIG. 8B and have acoustically equivalent function to the IDT electrode. Further discussion will be given for these dummy electrodes 2 A and 2 B.
- the transversal mode coupling is the same as the transversal mode coupling between adjacent two grating waveguides, similarly to the transversal mode coupling type resonator of FIG. 8A.
- the longitudinal mode coupling utilizes resonance mode by a multiple reflection between the reflectors 3 and 4 , resonance mode by multiple reflection between the IDT electrodes, and further resonance mode within the IDT electrode, similarly to the longitudinal mode coupling type resonator illustrated in FIG. 8B.
- the dummy electrodes 2 A and 2 B in the structure of FIG. 3A have equivalent structure to the IDT electrodes except for the structure of electrically shorting the IDT electrodes. Therefore, in the structure where two resonators A and B are adjacent in the transverse direction, both resonators A and B become equivalent to a uniform grating wave guide for the presence of the dummy electrodes 2 A and 2 B. Therefore, the desired transversal mode coupling can be obtained.
- the dummy electrodes 2 A and 2 B are acoustically equivalent to the IDT electrodes. Because of presence of the dummy electrodes, the multiple reflecting resonation between the reflectors, the multiple reflecting resonation between the IDT electrodes, and the resonation of the IDT electrode per se, as the longitudinal mode resonation can be utilized as in the longitudinal mode coupling type resonator.
- the electrodes are arranged to generate two longitudinal mode resonation in the longitudinal direction, SAW propagation in even symmetric mode (f 1 ) and odd symmetric mode (f 2 ) in the transverse direction so that two transversal mode characteristics can be obtained in the even symmetric mode and odd symmetric mode.
- FIG. 2B shows the composite resonance characteristics shown in FIG. 2B.
- the results of actual measurement are shown in FIGS. 4A and 4B.
- FIG. 4B shows in enlarged scale the frequency range near 250 MHz.
- FIGS. 5A and 5B show in enlarged scale the frequency range near 250 MHz.
- the shown SAW filter employs a ST cut quartz substrate, which exhibits capability of increasing of band width to 0.15% of relative band (3 dB band/center frequency) whereas the conventional relative band has been approximately 0.1%. Furthermore, as can be appreciated from the equivalent circuit of FIG. 2A, since the phase is reversed between the even symmetric mode and the odd symmetric mode (by transformer 16 ), attenuation rate can be improved for mutual cancellations of the signals of respective modes in the frequency range out of the pass band.
- FIG. 3B shows another embodiment of the SAW filter according to the present invention.
- a parallel connection is established between input and output of two longitudinal mode coupling type resonators A and B.
- the transversal mode is considered to be established by electrical coupling.
- the resonator A comprises a pair of IDT electrodes 1 A and 2 A, and reflectors 3 A and 4 A at both sides thereof.
- the resonator B comprises a pair of IDT electrodes 1 B and 2 B, the reflectors 3 B and 4 B at both sides thereof.
- the IDT electrodes 1 A and 2 B are electrically connected, and the IDT electrodes 2 A and 1 B are electrically connected to each other.
- two resonators A and B are connected in parallel between the input IN and the output OUT.
- FIG. 3B the relationship of the polarities of the IDT electrodes of the resonators A and B are selected to be opposite to each other. Namely, upper intersecting electrodes of the IDT electrodes 1 A and 2 A are grounded so that lower intersecting electrodes of the IDT electrodes 1 B and 2 B are grounded.
- an opposite phase relationship of signals of two resonators A and B can be established by shifting an interval between the IDT electrodes 1 B and 2 B of the resonator B for n/2 (n is odd integer) wavelength relative to the interval between the IDT electrodes 1 A and 2 A of the resonator A.
- FIGS. 6A and 6B show results of actual measurement of the characteristics for the filter having the structure of FIG. 3B. It should be noted that FIG. 6A is illustrated in the expanded scale for the frequency range near 250 MHz.
Abstract
A surface acoustic wave resonator filter includes an interdigital electrode on a piezoelectric substrate and has a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.
Description
- The present invention relates to a surface acoustic wave resonator filter. More specifically, the invention relates to a band-pass filter of the type of a surface acoustic wave (SAW) resonator utilizing a longitudinal mode resonance of a surface acoustic wave and having a wide band characteristics.
- An equivalent circuit of the conventional two pole mode SAW resonator is illustrated in FIG. 7A. It has been known that such SAW resonator includes two series
resonating circuits transformer 13. - When an impedance matching is established in the two pole mode SAW resonators under a certain condition, a filter characteristics as illustrated in FIG. 7B is obtained with a pass band between the resonance frequencies f11 and f12. A center frequency in the pass band is f1. As a typical filter employing this principle, monolithic quartz filter has been well known. With such filter construction, each insertion loss at the resonance frequencies f11 and f12 becomes substantially consistent with 3 dB point attenuating 3 dB from a minimum insertion loss (generally 0 dB) of the pass band.
- As conventional means for realizing such two pole mode resonator, there are a longitudinal mode resonation type for generating two resonance modes in a propagating direction of the surface acoustic wave and a transversal mode type for generating two resonance modes in a direction transverse to the propagating direction. This two pole mode resonator has been disclosed in M. Tanaka et al., “NARROW BANDPASS FILTER USING DOUBLE-MODE SAW RESONATORS ON QUARTZ” in the 38th Annual Frequency Control Symposium of IEEE, 1984, and M. Tanaka et al., “Narrow Bandpass Double Mode SAW Filter”, of the 15th EM Symposium of Electric Communication Committee, 1986.
- FIGS. 8A and 8B show the concrete construction of this two pole mode resonator. FIG. 8A shows a transversal mode coupling type filter, in which two resonators a and b are proximately arranged longitudinally in perpendicular to the propagating direction of the surface acoustic wave. The resonator a has an IDT (interdigital)
electrode 1 a at a center andreflectors 3 a and 4 a at both sides of theIDT electrode 1 a. Similarly, the resonator b has anIDT electrode 1 b at the center andreflectors IDT electrode 1 b. - In this transversal mode coupling type filter, the band-pass filter characteristics as shown in FIG. 7B is obtained by a coupling of two modes (even symmetric mode illustrated by f1 and odd symmetric mode illustrated by f2) FIG. 8B shows a longitudinal mode coupling type filter, in which two
IDT electrodes IDT electrodes reflectors - With this longitudinal mode coupling type filter, the band-pass filter characteristics as illustrated in FIG. 7B is obtained by the coupling of two modes generated between the input
side IDT electrode 1 and the outputside IDT electrode 2. - In such type of the surface acoustic wave filter, it is necessary to expand the interval between the resonance frequencies of two modes to be used in order to widen the filter characteristics. There is a restriction on the design parameter to cause various problems, such as large use impedance, degradation of the attenuation magnitude out of the band and so forth. Therefore, there is a limitation for widening the band.
- Therefore, it is an object of the present invention to provide a surface acoustic wave resonator filter which permits widening of bands with simple construction.
- According to one aspect of the invention, a surface acoustic wave resonator filter includes an interdigital electrode on a piezoelectric substrate, and has a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.
- The two-dimensional coupling type structure may be formed by proximately arranging first and second longitudinal mode coupling type resonators on the piezoelectric substrate for establishing transversal coupling.
- According to another aspect of the invention, a surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, comprises first and second longitudinal mode coupling type resonators utilizing longitudinal mode resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave, the first and second longitudinal mode coupling type resonators being established a parallel connection between inputs and outputs thereof.
- The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken limitative to the present invention, but are for explanation and understanding only.
- In the drawings:
- FIGS. 1A and 1B are illustration respectively showing filter characteristics of the present invention;
- FIG. 2A is an equivalent circuit diagram of a filter according to the present invention;
- FIG. 2B is a characteristic chart of the filter of the invention;
- FIG. 3A is an illustration showing a construction of one embodiment of the present invention;
- FIG. 3B is an illustration showing a construction of another embodiment of the invention;
- FIGS. 4A and 4B show results of actual measurement of filter characteristics of one embodiment of the invention;
- FIGS. 5A and 5B show results of actual measurement of the characteristics in case that another embodiment of the filter according to the invention is used for impedance matching;
- FIGS. 6A and 6B show results of actual measurement of the characteristics in case that another embodiment of the filter according to the invention is used for impedance matching;
- FIG. 7A is an equivalent circuit diagram of the conventional SAW resonator;
- FIG. 7B is an illustration of a characteristics of the conventional SAW resonator;
- FIG. 8A is an illustration showing a construction of the conventional transversal mode coupling type filter; and
- FIG. 8B is an illustration showing a construction of the conventional longitudinal mode coupling type filter.
- Initially, consideration is given for the case where is a two pole mode SAW resonator A having resonance frequencies f11 and f12 and a two pole mode resonator B having resonance frequencies f21 and f22. When an impedance matching is established for using as a filter, a filter characteristics becomes as illustrated in FIG. 1B, assuming the center frequencies in the pass-bands are respectively f1 and f2. In order to establish a single filter characteristics as illustrated in FIG. 1A by composing these two filter characteristics A and B, it is essential conditions that, in the cross point of these two characteristics A and B, the power of each output signal of each filter is half of the power of the output signal of the pass band and two signals are in the same phase. The equivalent circuit of the resonators A and B satisfying these essential conditions is as illustrated in FIG. 2A. The equivalent circuit of the resonator A has a
parallel connection 14 of the series resonating circuit having resonance frequencies f11 and f12. Similarly, the equivalent circuit of the resonator B has a parallel connection of a series resonating circuit having resonance frequencies f21 and f22. - Then, the output signals the high band side resonance frequency f12 of the resonator A and the low band side resonance frequency f21 of the resonator B are to be matched to each other in the vector sense (both in the power and phase). This relationship is illustrated in the
transformer 16. At this time, the composite resonance characteristics becomes as illustrated in FIG. 2B. Then, the filter characteristics with established impedance matching becomes wide band as illustrated in FIG. 1A. - The embodiment of the filter construction of the present invention satisfying the above-mentioned characteristics is illustrated in FIG. 3A. As shown in FIG. 3A, the shown embodiment is constructed by two sets of longitudinal mode coupling type resonators illustrated in FIG. 8B proximately arranged in the transverse direction and transversal mode coupling being acoustically established between these two resonators. Namely, the SAW filter according to the invention is designed in a two-dimensional mode coupling type structure by coupling the longitudinal mode resonation in the longitudinal direction as the propagating direction of the surface acoustic wave and the transversal mode resonation in the transverse direction perpendicular to the propagating direction.
- In the construction shown in FIG. 3A, two longitudinal mode coupling type resonators A and B are arranged on a
piezoelectric substrate 20 in a cross proximity to each other for permitting acoustical transversal mode coupling. ANInput IDT electrode 1A and adummy electrode 2A are arranged in the longitudinal direction. Also,reflectors IDT electrode 1A, thedummy electrode 2A andreflectors - An
output IDT electrode 1B and adummy electrode 2B are also arranged in the longitudinal direction.Reflectors IDT electrode 1B, thedummy electrode 2B and thereflectors - It should be noted that the
dummy electrodes dummy electrodes reflectors - The
dummy electrodes dummy electrodes - On the other hand, observing as the coupling in the longitudinal direction, it is necessary that the
dummy electrodes - Although the electrodes are arranged to generate two longitudinal mode resonation in the longitudinal direction, SAW propagation in even symmetric mode (f1) and odd symmetric mode (f2) in the transverse direction so that two transversal mode characteristics can be obtained in the even symmetric mode and odd symmetric mode.
- This is illustrated in a form of the equivalent circuit as shown in FIG. 2A, in which the resonating
circuit 14 represents the even symmetric mode and the resonatingcircuit 15 represents odd symmetric mode.Respective resonating circuits - In the shown construction, it is necessary to establish matching as shown in FIG. 2B between the higher side longitudinal mode resonation f12 of the even symmetric mode and the lower side longitudinal mode resonation f21 of the odd symmetric mode. This can be achieved by appropriately selecting the number of IDT pairs N, the longitudinal mutual interval between the IDT electrodes, longitudinal distances between the IDT electrode and the reflectors.
- With the construction set forth above, the composite resonance characteristics shown in FIG. 2B can be obtained. The results of actual measurement are shown in FIGS. 4A and 4B. FIG. 4B shows in enlarged scale the frequency range near 250 MHz. When the filter of FIG. 3A is used with matched impedance, a flat characteristics in the pass band can be obtained as illustrated in FIGS. 5A and 5B. It should be noted that FIG. 5B shows in enlarged scale the frequency range near 250 MHz.
- The shown SAW filter employs a ST cut quartz substrate, which exhibits capability of increasing of band width to 0.15% of relative band (3 dB band/center frequency) whereas the conventional relative band has been approximately 0.1%. Furthermore, as can be appreciated from the equivalent circuit of FIG. 2A, since the phase is reversed between the even symmetric mode and the odd symmetric mode (by transformer16), attenuation rate can be improved for mutual cancellations of the signals of respective modes in the frequency range out of the pass band.
- FIG. 3B shows another embodiment of the SAW filter according to the present invention. In this embodiment, a parallel connection is established between input and output of two longitudinal mode coupling type resonators A and B. The transversal mode is considered to be established by electrical coupling.
- The resonator A comprises a pair of
IDT electrodes reflectors IDT electrodes reflectors IDT electrodes IDT electrodes - Even in this construction. the equivalent circuit the same as FIG. 2A can be established. Here, it becomes necessary that the signals from two resonators has to have opposite phase relationship. Therefore, in FIG. 3B, the relationship of the polarities of the IDT electrodes of the resonators A and B are selected to be opposite to each other. Namely, upper intersecting electrodes of the
IDT electrodes IDT electrodes - On the other hand, as another method, an opposite phase relationship of signals of two resonators A and B can be established by shifting an interval between the
IDT electrodes IDT electrodes - FIGS. 6A and 6B show results of actual measurement of the characteristics for the filter having the structure of FIG. 3B. It should be noted that FIG. 6A is illustrated in the expanded scale for the frequency range near 250 MHz.
- As set forth above, according to the present invention, it becomes possible to widen the band of the filter characteristics by acoustically or electrically coupling two pole modes SAW resonators and composing the characteristics of two resonators of the frequency axis.
- Although the invention has been illustrated and described with respect to exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodies within a scope encompassed and equivalents thereof with respect to the feature set out in the appended claims.
Claims (9)
1. A surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, having a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.
2. A surface acoustic wave resonator filter as set forth in claim 1 , wherein said two-dimensional coupling type structure is formed by proximately arranging first and second longitudinal mode coupling type resonators on said piezoelectric substrate for establishing transversal coupling.
3. A surface acoustic wave resonator filter as set forth in claim 2 , wherein each of said first and second longitudinal mode coupling type resonators is provided a plurality of resonance frequencies and one of the resonance frequencies of the first resonator is equal to one of the resonance frequencies of the second resonator.
4. A surface acoustic wave resonator filter as set forth in claim 3 , wherein the transversal mode coupling of the first and second longitudinal mode coupling type resonators is an acoustic coupling.
5. A surface acoustic wave resonator filter as set forth in claim 4 , wherein each of the first and second longitudinal mode coupling type resonators has a dummy electrode arranged adjacent own interdigital electrode in the longitudinal direction and adjacent to san interdigital electrode of the other resonator in the transverse direction for establishing the acoustic coupling.
6. A surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, comprising first and second longitudinal mode coupling type resonators utilizing longitudinal mode resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave, said first and second longitudinal mode coupling type resonators being established a parallel connection between inputs and outputs thereof.
7. A surface acoustic wave resonator filter as set forth in claim 6 , wherein each of said first and second longitudinal mode coupling type resonators has first and second interdigital electrodes arranged adjacent to each other in the longitudinal direction, the first interdigital electrode of said first longitudinal mode coupling type resonator and the first interdigital electrode of said second longitudinal mode coupling type resonator are electrically connected, and the second interdigital electrode of said first longitudinal mode coupling type resonator and the second interdigital electrode of said second longitudinal mode coupling type resonator are electrically connected.
8. A surface acoustic wave resonator filter as set forth in claim 7 , respective of first interdigital electrodes and respective second interdigital electrodes of said first and second longitudinal mode coupling type resonators are used in the opposite polarities.
9. A surface acoustic wave resonator filter as set forth in claim 7 , wherein each space between the interdigital electrodes of said first and second longitudinal mode coupling type resonators are mutually shifted for a n/ 2 wavelength (n is an odd integer).
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US10/108,623 US20020096968A1 (en) | 1992-08-24 | 2002-03-29 | Surface acoustic wave resonator filter |
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US11099793A | 1993-08-24 | 1993-08-24 | |
US08/419,764 US5592040A (en) | 1992-08-24 | 1995-04-10 | Acoustic wave resonator filter |
US08/674,727 US6437478B1 (en) | 1992-08-24 | 1996-07-02 | Surface acoustic wave resonator filter |
US10/108,623 US20020096968A1 (en) | 1992-08-24 | 2002-03-29 | Surface acoustic wave resonator filter |
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US08/674,727 Expired - Lifetime US6437478B1 (en) | 1992-08-24 | 1996-07-02 | Surface acoustic wave resonator filter |
US10/108,623 Abandoned US20020096968A1 (en) | 1992-08-24 | 2002-03-29 | Surface acoustic wave resonator filter |
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US08/674,727 Expired - Lifetime US6437478B1 (en) | 1992-08-24 | 1996-07-02 | Surface acoustic wave resonator filter |
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GB1512790A (en) * | 1975-08-22 | 1978-06-01 | Mullard Ltd | Acoustic surface wave devices |
US3988703A (en) * | 1975-12-31 | 1976-10-26 | Zenith Radio Corporation | Acoustic surface wave device having split-isolated or split-connected multistrip coupler |
US3987379A (en) * | 1976-01-02 | 1976-10-19 | Zenith Radio Corporation | Acoustic surface wave filter having combined split-isolated and split-connected coupler |
US4060777A (en) * | 1976-05-19 | 1977-11-29 | Piezo Technology Inc. | Guided elastic surface wave filter |
GB1554366A (en) * | 1977-02-04 | 1979-10-17 | Philips Electronic Associated | Acoustic surface wave devices |
JPS5693414A (en) * | 1979-12-27 | 1981-07-29 | Fujitsu Ltd | Elastic surface wave element |
EP0109446B1 (en) * | 1982-05-25 | 1987-08-12 | Nippon Telegraph And Telephone Corporation | Variable frequency oscillator |
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DE4214122C2 (en) | 1992-04-29 | 2001-02-22 | Siemens Ag | Two-track surface wave arrangement with improved selection property |
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DE4447740B4 (en) * | 1993-09-06 | 2008-10-09 | Sanyo Electric Co., Ltd., Moriguchi | Acoustic surface wave filter |
EP0648015B1 (en) * | 1993-10-08 | 2000-05-31 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter |
US5426339A (en) * | 1994-04-01 | 1995-06-20 | Rf Monolithics, Inc. | Surface acoustic wave devices with mode changing characteristics |
-
1993
- 1993-08-23 DE DE69319977T patent/DE69319977T3/en not_active Expired - Lifetime
- 1993-08-23 EP EP93113426A patent/EP0584761B2/en not_active Expired - Lifetime
-
1995
- 1995-04-10 US US08/419,764 patent/US5592040A/en not_active Expired - Lifetime
-
1996
- 1996-07-02 US US08/674,727 patent/US6437478B1/en not_active Expired - Lifetime
-
2002
- 2002-03-29 US US10/108,623 patent/US20020096968A1/en not_active Abandoned
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20120108167A1 (en) * | 2010-10-27 | 2012-05-03 | Hollinworth Fund, L.L.C. | Resonator-Based Filtering |
US8620250B2 (en) * | 2010-10-27 | 2013-12-31 | Hollinworth Fund, L.L.C. | Resonator-based filtering |
Also Published As
Publication number | Publication date |
---|---|
EP0584761B2 (en) | 2005-08-31 |
DE69319977T2 (en) | 1998-12-10 |
US6437478B1 (en) | 2002-08-20 |
US5592040A (en) | 1997-01-07 |
DE69319977D1 (en) | 1998-09-03 |
EP0584761B1 (en) | 1998-07-29 |
DE69319977T3 (en) | 2006-06-14 |
EP0584761A1 (en) | 1994-03-02 |
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Legal Events
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Owner name: NRS TECHNOLOGIES, INC., JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NEC CORPORATION;REEL/FRAME:013548/0434 Effective date: 20021029 |
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STCB | Information on status: application discontinuation |
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