GB1576455A – Surface wave filters or delay lines
– Google Patents
GB1576455A – Surface wave filters or delay lines
– Google Patents
Surface wave filters or delay lines
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Publication number
GB1576455A
GB1576455A
GB17055/77A
GB1705577A
GB1576455A
GB 1576455 A
GB1576455 A
GB 1576455A
GB 17055/77 A
GB17055/77 A
GB 17055/77A
GB 1705577 A
GB1705577 A
GB 1705577A
GB 1576455 A
GB1576455 A
GB 1576455A
Authority
GB
United Kingdom
Prior art keywords
feeders
delay line
filter
transducers
fingers
Prior art date
1976-04-26
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB17055/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-04-26
Filing date
1977-04-25
Publication date
1980-10-08
1977-04-25
Application filed by Siemens AG
filed
Critical
Siemens AG
1980-10-08
Publication of GB1576455A
publication
Critical
patent/GB1576455A/en
Status
Expired
legal-status
Critical
Current
Links
Espacenet
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Classifications
H—ELECTRICITY
H03—ELECTRONIC CIRCUITRY
H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
H03H9/02—Details
H03H9/125—Driving means, e.g. electrodes, coils
H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
H03H9/14544—Transducers of particular shape or position
H03H9/1455—Transducers of particular shape or position constituted of N parallel or series transducers
H—ELECTRICITY
H03—ELECTRONIC CIRCUITRY
H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
H03H9/02—Details
H03H9/02535—Details of surface acoustic wave devices
H03H9/02818—Means for compensation or elimination of undesirable effects
H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
H—ELECTRICITY
H03—ELECTRONIC CIRCUITRY
H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
H03H9/02—Details
H03H9/02535—Details of surface acoustic wave devices
H03H9/02818—Means for compensation or elimination of undesirable effects
H03H9/02858—Means for compensation or elimination of undesirable effects of wave front distortion
H—ELECTRICITY
H03—ELECTRONIC CIRCUITRY
H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
H03H9/02—Details
H03H9/125—Driving means, e.g. electrodes, coils
H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
H03H9/14517—Means for weighting
H03H9/1452—Means for weighting by finger overlap length, apodisation
Description
PATENT SPECIFICATION
Application No 17055/77 ( 22) Filed 25 Apr 1977 Convention Application No 2618210 ( 32) Filed 26 Apr.
Fed Rep of Germany (DE) Complete Specification Published 8 Oct 1980
INT CL 3 ( 11) 1 576 455 1976 inl H 03 H 9/145 // 9/14 ( 52) Index at Acceptance H 3 U 22 26 Y 29 B 29 Y 32 T ( 54) IMPROVEMENTS IN OR RELATING TO SURFACE WAVE FILTERS OR DELAY LINES ( 71) We, SIEMENS AKTIENGESELLSCHAFT, a German Company of Berlin and Munich, German Federal Republic, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The invention relates to surface wave filters or delay lines, using transducer electrodes on a piezo-electric substrate to launch and/or detect waves transmitted via the substrate.
It is known that any metallising of the surface of a piezo-electric substrate reduces the propagation velocity of elastic surface waves.
In the case of a transducer formed by interdigitated electrodes with longitudinally weighted electrode fingers, for example, this effect causes those parts of any wave front passing the electrode finger overlap zone to encounter a comparatively densely metallised zone, whereas those parts of the -wave front passing outside the overlap zone will each encounter a zone having comparatively little metallisation The wave components passing in the less metallised zone will lead the other parts, and this results in an undesired distortion of the wave front, and thus introduces discrepancies between the effective frequency response and the desired frequency response of any particular transmission element.
In order to eliminate the effects of leading wave components it has been proposed that the deficiency of metallisation outside the finger electrode overlap zone could be compensated by the addition of dummy fingers.
These dummy fingers can be insulated from the electrode fingers, or can be electrically connected to adjacent finger electrodes.
Such dummy fingers have the same breadth as the other electrode fingers, i e.
about a quarter of the synchronous wavelength of a propogated surface wave.
Thus, they have the disadvantage that the reflections of the surface wave at the finger edges are added at the synchronous frequency, and this impairs the amplitude and phase frequency response right in the middle of the transmission band To eliminate these annoying reflections, one proposed solution involves the use of electrode fingers in the form of split-fingers, where each electrode finger is a double strip However, this gives undesirably narrow metallising strips, which are so delicate that they introduce production problems, and also have a higher resistance and thus cause increased losses of electrical energy.
One object of the present invention is to provide a delay line or filter of this type with a transit time compensator effective for elastic surface waves, in the peripheral zone of longitudinally weighted interdigitated electrode transducers, that is easy to manufacture, causes no additional reflections at the finger edges and does not produce high losses of electrical energy.
The invention consists in a surface wave filter or delay line in which a piezo-electric substrate is provided with one or more interdigitated electrode transducers for launching or detecting surface waves of mean frequency fo, via said substrate, the fingers of said transducers being longitudinally weighted and that part of the fingers lying outside their overlap zone forming feeders whose conductive breadth b is in each case at least approximately equal to X 0/2 = v/2 f O; where Xo is the wavelength of the surface waves, at frequency f O; and v is the propagation velocity of the surface waves.
This gives the advantages that the reflection components normally originating from the front and rear edges of the feeders are mutually equalising, so that the transmission band remains free of the edge reflection troubles normally caused by feeders, whilst the low internal resistance of the feeders Ltn 1 fn ( 21) ( 31) ( 33) ( 44) ( 51) 1,576,455 ensures that the area covered by the feeders forms a more precise equipotential area than is the case with known dummy fingers and that any difference in transit time as a result of differing breadths of metallisation is eliminated.
Preferably, the breadth of the feeders is varied to a small extent from 2 in accordance with frequencies within the pass band of the transducers, either such that each feeder individually, or such that groups of feeders, are tuned to mutually differing synchronous frequencies In this way any middle reflections can be kept small despite the use of very broad-banded transmission elements.
The effect of the area covered by the feeders as an equipotential area can be further improved by interconnecting the feeders by additional webbing.
Preferably the feeders are connected with the earthed transducer electrode fingers and form part of a static shielding lying between input and output transducers of a filter or delay line.
The invention will now be described with reference to the drawing, in which a partly diagrammatic plan view is shown of one exemplary embodiment of an interdigitated electrode transducer for exciting elastic surface waves on a piezo-electric substrate with longitudinally weighted electrode fingers.
The transducer has the form of a double symmetrical transducer in which a live electrode structure 1 is disposed centrally between two outer electrodes 2 and 3, which are connected to a reference potential, i e to earth potential A zone 4 is shown by light shading, this being the zone in which finger electrodes 5 and 6 overlap and corresponding to the function y = sin x/x.
The breadth b of feeders 7 extending from the electrodes 2 and 3 to the actual finger electrodes 5 is equal to half the wavelength of the surface wave that is to be transmitted or detected A further reduction in the resistance can be obtained by providing additional transverse webbing 8 between the feeders 7.
Surface wave components moving to the right and generated in an area 41 of the overlap zone 4 would pass through a zone with a much higher metallisation density than those generated in the upper part of the area 42 and also moving to the right if this were not equalised by the broadening of the feeders 7.
In the case where the elctrode fingers 5 and 6 and the interspaces between these electrode fingers 5 and 6 are not equal, i e where the fingers do not have a breadth of a quarter of the wavelength, the metallised area inside and outside the overlap zone could be different If the breadth of the electrode fingers in the overlap zone is reduced, thereby making the metallised area smaller, this must be compensated for outside the overlap zone by reducing the number of feeders, and not by any reduction in the breadth of the feeders.
Then it would be possible to connect a plurality of electrode fingers to any one feeder.
Claims (4)
WHAT WE CLAIM IS: 70
1 A surface wave filter or delay line in which a piezo-electric substrate is provided with one or more interdigitated electrode transducers for launching or detecting surface waves of mean frequency f O via said 75 substrate, the fingers of said transducers being longitudinally weighted and that part of the fingers lying outside their overlap zone forming feeders, whose conductive breadth b is in each case at least approximately equal to 80 Xo /2 = v/2 fo; where Xo is the wavelength of surface waves at frequency fo; and v is the propagation velocity of the surface waves.
2 A filter or delay line as claimed in Claim 1, inwhich thebreadthb of the feeders 85 varies, to a small extent from X 0/2 in accordance with frequencies within the pass band of the transducers, such that individual feeders or groups of feeders are tuned to mutually differing synchronous frequencies 90
3 A filter or delay line as claimed in Claim 1 or Claim 2 in which the feeders are interconnected by connecting webbing.
4 A filter or delay line as claimed in any preceding Claim, in which the feeders are 95 connected with the earthed transducer electrode or electrodes and form part of a static shielding between input and output transducers of the filter or delay line.
A surface wave filter or delay line sub 10 ( stantially as described with reference to the drawing.
For the Applicants G F REDFERN & CO, Marlborough Lodge, 14 Farncombe Road, Worthing BN 11 2 BT ) Printed for Her Majesty’s Stationery Office, by Croydon Printing Company Limited Croydon, Surrey, 1980.
Published by The Patent Office, 25 Southampton Buildings, London WC 2 A l AY, from which copies may be obtained.
GB17055/77A
1976-04-26
1977-04-25
Surface wave filters or delay lines
Expired
GB1576455A
(en)
Applications Claiming Priority (1)
Application Number
Priority Date
Filing Date
Title
DE2618210A
DE2618210C3
(en)
1976-04-26
1976-04-26
Converter electrodes for filters or delay lines based on the surface wave principle
Publications (1)
Publication Number
Publication Date
GB1576455A
true
GB1576455A
(en)
1980-10-08
Family
ID=5976265
Family Applications (1)
Application Number
Title
Priority Date
Filing Date
GB17055/77A
Expired
GB1576455A
(en)
1976-04-26
1977-04-25
Surface wave filters or delay lines
Country Status (7)
Country
Link
US
(1)
US4160219A
(en)
JP
(1)
JPS52130550A
(en)
BR
(1)
BR7702585A
(en)
DE
(1)
DE2618210C3
(en)
FR
(1)
FR2350001A1
(en)
GB
(1)
GB1576455A
(en)
IT
(1)
IT1084935B
(en)
Families Citing this family (11)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
JPS5847090B2
(en)
*
1977-08-10
1983-10-20
株式会社村田製作所
surface acoustic wave filter
FR2428350A1
(en)
*
1978-06-06
1980-01-04
Thomson Csf
SURFACE ELASTIC WAVE FILTER AND INTERMEDIATE FREQUENCY STAGE OF A TELEVISION RECEIVER COMPRISING SUCH A FILTER
US4604595A
(en)
*
1982-06-16
1986-08-05
Murata Manufacturing Co., Ltd.
Surface acoustic wave device having interdigitated comb electrodes weighted for odd/even response
USRE33957E
(en)
*
1982-07-26
1992-06-09
Toyo Communication Equipment Co., Ltd.
High frequency narrow-band multi-mode filter
GB2132844A
(en)
*
1982-12-22
1984-07-11
Philips Electronic Associated
Surface acoustic wave device
US4535265A
(en)
*
1984-05-17
1985-08-13
Kabushiki Kaisha Toshiba
Surface acoustic wave transducer with internal acoustic reflection
US4918349A
(en)
*
1987-11-13
1990-04-17
Hitachi, Ltd.
Surface acoustic wave device having apodized transducer provided with irregular pitch electrode group
JPH02189015A
(en)
*
1989-01-17
1990-07-25
Clarion Co Ltd
Surface acoustic wave device
JPH0685597A
(en)
*
1992-09-02
1994-03-25
Mitsubishi Electric Corp
Saw device
US6791236B1
(en)
*
2000-10-11
2004-09-14
Yuri Abramov
Method utilizing the saw velocity dispersion effect for weighting by shaping the electrode fingers of a saw interdigital transducer and apparatus produced thereby
DE102010055628B4
(en)
2010-12-22
2018-09-06
Snaptrack, Inc.
Electro-acoustic resonator
Family Cites Families (3)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
FR2040881A5
(en)
*
1969-04-16
1971-01-22
Thomson Csf
GB1355418A
(en)
*
1971-05-24
1974-06-05
Mullard Ltd
Acoustic surface wave devices
GB1430725A
(en)
*
1974-08-02
1976-04-07
Mullard Ltd
Acoustic surface wave devices
1976
1976-04-26
DE
DE2618210A
patent/DE2618210C3/en
not_active
Expired
1977
1977-04-01
US
US05/783,837
patent/US4160219A/en
not_active
Expired – Lifetime
1977-04-19
IT
IT22582/77A
patent/IT1084935B/en
active
1977-04-25
FR
FR7712366A
patent/FR2350001A1/en
active
Granted
1977-04-25
GB
GB17055/77A
patent/GB1576455A/en
not_active
Expired
1977-04-25
BR
BR7702585A
patent/BR7702585A/en
unknown
1977-04-26
JP
JP4830677A
patent/JPS52130550A/en
active
Pending
Also Published As
Publication number
Publication date
US4160219A
(en)
1979-07-03
IT1084935B
(en)
1985-05-28
FR2350001A1
(en)
1977-11-25
BR7702585A
(en)
1978-01-10
DE2618210A1
(en)
1977-11-10
DE2618210B2
(en)
1979-07-12
DE2618210C3
(en)
1980-03-13
FR2350001B1
(en)
1980-01-18
JPS52130550A
(en)
1977-11-01
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Legal Events
Date
Code
Title
Description
1980-12-31
PS
Patent sealed [section 19, patents act 1949]
1986-12-17
PCNP
Patent ceased through non-payment of renewal fee
