Claims
- 1. An end face reflection type surface wave resonator comprising:
- a piezoelectric substrate of a rectangular shape, said piezoelectric substrate having a first end face and a second end face which are substantially parallel to each other and reflect shear horizontal type surface waves propagating on a surface of said piezoelectric substrate in a direction perpendicular to said first and second end faces; and
- a first interdigital transducer and a second interdigital transducer provided on said piezoelectric substrate, each of said first and second interdigital transducers including a pair of comb-like electrodes, each end of each of said first and second interdigital transducers being substantially flush with a respective one of said first and second end faces, respectively, thereby forming a first resonant unit which includes said first interdigital transducer and a portion of said piezoelectric substrate and a second resonant unit which includes said second interdigital transducer and a portion of said piezoelectric substrate,
- wherein a number N.sub.1 of fingers of said first interdigital transducer is different from a number N.sub.2 of fingers of said second interdigital transducer, whereby said first resonant unit has a first resonance frequency f.sub.1 and said second resonant unit has a second resonance frequency f.sub.2 which is different from said first resonance frequency.
- 2. An end face reflection type surface wave resonator according to claim 1, wherein said number N.sub.1 satisfies the following inequality:
- (.lambda..sub.1 /2).times.N.sub.1 -.lambda./20.ltoreq.L.ltoreq.(.lambda..sub.1 /2).times.N.sub.1 30 .lambda./20
- where .lambda..sub.1 represents a wavelength of surface waves excited by said first interdigital transducer and L represents a distance between said first and second end faces.
- 3. An end face reflection type surface wave resonator according to claim 2, wherein said number N.sub.2 satisfies either of the following inequalities:
- L<(.lambda..sub.2 /2).times.N.sub.2 -.lambda./20 or (.lambda..sub.2 /2).times.N.sub.2 +.lambda./20<L
- where .lambda..sub.2 represents a wavelength of surface waves excited by said second interdigital transducer.
- 4. An end face reflection type surface wave resonator according to claim 1, wherein said number N.sub.2 satisfies either of the following inequalities:
- L<(.lambda..sub.2 /2).times.N.sub.2 -.lambda./20 or (.lambda..sub.2 /2).times.N.sub.2 +.lambda./20<L
- where .lambda..sub.2 represents a wavelength of surface waves excited by said second interdigital transducer.
- 5. An end face reflection type surface wave resonator according to claim 1, wherein said end face reflection type surface wave resonator is included in a trap circuit in a video intermediate frequency circuit of a television receiver and said first resonance frequency and second resonance frequency are spaced apart such that said first resonance frequency is an adjacent sound carrier frequency to be trapped and said second resonance frequency is an adjacent picture carrier frequency to be trapped.
- 6. An end face reflection type surface wave resonator comprising:
- a piezoelectric substrate of a rectangular shape, said piezoelectric substrate having an upper surface, first and second reflecting end faces which define two sides of said upper surface, at least one groove which is provided on said upper surface to divide said upper surface into a first region and a second region and third and fourth reflecting end faces which are provided by said at least one groove and extend from said upper face to an inside of said piezoelectric substrate;
- a first interdigital transducer provided on said first region of said upper surface, said first interdigital transducer including a pair of comb-like electrodes, each end of each of said pair of comb-like electrodes being substantially flush with a respective one of said first and third reflecting end faces, respectively; and
- a second interdigital transducer provided on said second region of said upper surface, said second interdigital transducer including a pair of comb-like electrodes, each end of each of said pair of comb-like electrodes being substantially flush with a respective one of said second and fourth reflecting end faces, respectively, whereby said first region interposed between said first reflecting end face and said third reflecting end face and said second region interposed between said second reflecting end face and said fourth reflecting end face form reflection type surface wave resonator units, respectively,
- wherein a number N.sub.1 of fingers of said first interdigital transducer is different from a number N.sub.2 of fingers of said second interdigital transducer, whereby said first interdigital transducer has a first resonance frequency f.sub.1 and said second interdigital transducer has a second resonance frequency f.sub.2 which is different from said first resonance frequency.
- 7. An end face reflection type surface wave resonator according to claim 6, wherein said number N.sub.1 satisfies the following inequality:
- (.lambda..sub.1 /2).times.N.sub.1 -.lambda./20.ltoreq.L.ltoreq.(.lambda./2).times.N.sub.1 +.lambda./20
- where .lambda..sub.1 represents a wavelength of surface waves excited by said first interdigital transducer and L represents a distance between said first and second end faces.
- 8. An end face reflection type surface wave resonator according to claim 7, wherein said number N.sub.2 satisfies either of the following inequalities:
- L<(.lambda.2/2).times.N.sub.2 -.lambda./20 or (.lambda..sub.2 /2).times.N.sub.2 +.lambda./20<L
- where .lambda..sub.2 represents a wavelength of surface waves excited by said second interdigital transducer.
- 9. An end face reflection type surface wave resonator according to claim 6, wherein said number N.sub.2 satisfies either of the following inequalities:
- L<(.lambda./2).times.N.sub.2 -.lambda./20 or (.lambda..sub.2 /2).times.N.sub.2 +.lambda./20<L
- where .lambda..sub.2 represents a wavelength of surface waves excited by said second interdigital transducer.
- 10. An end face reflection type surface wave resonator according to claim 6, wherein said end face reflection type surface wave resonator is included in a trap circuit in a video intermediate frequency circuit of a television receiver and said first resonance frequency and second resonance frequency are spaced apart such that said first resonance frequency is an adjacent sound carrier frequency to be trapped and said second resonance frequency is an adjacent picture carrier frequency to be trapped.
Priority Claims (1)
Number |
Date |
Country |
Kind |
6-116975 |
May 1994 |
JPX |
|
Parent Case Info
This is a Continuation of application Ser. No. 08/639,716, filed on Apr. 29, 1996, abandoned, which is a continuation of application Ser. No. 08/453,622, filed on May 30, 1995, abandoned.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
3763446 |
Toyoshima et al. |
Oct 1973 |
|
4647881 |
Mitsutsuka |
Mar 1987 |
|
5010269 |
Hikita et al. |
Apr 1991 |
|
5077545 |
Gopani et al. |
Dec 1991 |
|
5235235 |
Martin et al. |
Aug 1993 |
|
Foreign Referenced Citations (5)
Number |
Date |
Country |
0094683 |
Nov 1983 |
EPX |
0100503 |
Nov 1983 |
EPX |
0023609 |
Jan 1989 |
JPX |
5304436 |
Nov 1993 |
JPX |
2000409 |
Jan 1979 |
GBX |
Non-Patent Literature Citations (2)
Entry |
Patent Abstracts of Japn, vol. 16, No. 312 (E-1230), Jul. 9, 1992, JP-4 87 410 A (Murata Mfg.). |
"Kokusai Gihou", International Electronic Technology Bulletin, No. 16, pp. 1-7, 1992. |
Continuations (2)
|
Number |
Date |
Country |
Parent |
639716 |
Apr 1996 |
|
Parent |
453622 |
May 1995 |
|