CN1038556A - Synchronizing signal extracting sound surface wave filter - Google Patents
Synchronizing signal extracting sound surface wave filter Download PDFInfo
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- CN1038556A CN1038556A CN 88103334 CN88103334A CN1038556A CN 1038556 A CN1038556 A CN 1038556A CN 88103334 CN88103334 CN 88103334 CN 88103334 A CN88103334 A CN 88103334A CN 1038556 A CN1038556 A CN 1038556A
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Abstract
The present invention discloses a kind of synchronizing signal extracting sound surface wave filter that is applicable to two-forty long-distance optical fiber telecommunication transmission system.The present invention adopts transverse type (disresonance device formula) filter construction, and promptly hobbing calcium carbide English crystal wafer with a ST is substrate, constitutes a pair of its electrode and be configured to 3 interdigital transducers and 4 interdigital transducers on this substrate minute surface.In order not make the signal of telecommunication directly pass to output transducer, an electric screen thing is set between transducer; In order to absorb the bulk wave signal, be coated with the jelly that has the strong bond effect again that one deck can absorb the bulk wave signal at the substrate reverse side.
Description
The present invention relates to surface acoustic wave (SAW-SUrface Acoustic Wane) filter, relate in particular to a kind of synchronizing signal extraction (Synchronizing extraction) SAW filter that is applicable in the two-forty long-distance optical fiber communication system.
In the high rate communication transmission system, in order from input signal, to extract synchronizing signal, recover the signal amplitude decay that causes in the transmission, need synchronizing signal extraction filter (the general load Q value 〉=700-800) of high capacity Q value.At present, in coaxial cable PCM system, as synchronous helicon load Q value lower (the Q value is 120-170), can not be used as two-forty and grow synchronizing signal extraction filter in the optical fiber communication transmission system of distance.The monolithic crystal filter that utilizes the bulk wave theory to make might be competent at this work, but because the process technology of its substrate, when being higher than 100MHZ, relatively difficulty is difficult for producing in batches.In the 100MHZ-1000MHZ frequency range, the processing of SAW filter is easier to, and is convenient to mass production, and very high load Q value (greater than 700-800) is arranged.In addition, compare with active device, it belongs to the passive device category, and this is all very favourable to noise and the power consumption that reduces whole system.
As mentioned above because surface acoustic wave filtering Q value is high, good manufacturability, in recent years, it has obtained application widely, about the patent documentation and the data of SAW filter more.As: U.S. Patent number 4308510 patents relate to the SAW filter that a kind of certain relatively centre frequency that is used for TV tech obtains the nonsymmetric frequencies characteristic, and for example China Patent No. CN85101813 patent of invention (Hitachi-applicant of Amada Co., Ltd.) or the like.Relate to and be same as documents and materials of the present invention, discovery as yet at present.
In view of above-mentioned relevant prior art present situation, purpose of the present invention provides a kind of synchronizing signal that is used for the high rate communication transmission system and extracts the SAW filter, and its load Q value is 700-800.
The present invention adopts transverse type (disresonance device formula) filter construction.Promptly hobbing calcium carbide English crystal wafer with a ST is substrate, on its sheet minute surface, constitute a pair of certain electrode and be configured to 3 interdigital transducers and 4 interdigital transducers, each cycle is respectively A-A-B-B, and A '-A '-B '-B ' respectively is the surface acoustic wave input and output reversible transducer of 57 groups and 73 groups.Input signal through excitation, produces elastic surface wave from input transducer input,, is received through it by output transducer and to convert the signal of telecommunication to and export to propagation along forwards.
In order to make electrical input signal directly not pass to output transducer,, an electric screen thing is set and makes filter impedance and the external circuit impedance coupling at energy converter planar.
The bulk wave signal that produces in order to make as the work of the piezoelectric quartz crystal sheet of its substrate can be absorbed, and one deck can absorb the jelly that such bulk wave signal has the strong bond effect again on substrate reverse side way.
For the SAW that passes to the substrate end face along the direction of propagation can be absorbed, eliminate it and cause second-order effects, be coated with one deck sound absorption material at the substrate end face.
The present invention obtains higher stopband to suppress, select for use its shell housing width and operating frequency wavelength ratio be λ C/ λ＜＜1(λ C is the cavity cut-off wavelength, λ is the cavity operation wavelength.）
SAW filter center frequency accuracy of the present invention is 60-80ppm.We adopt on the control substrate minute surface thickness of metal film 600
-700
Interior way reaches.
The SAW filter of design according to the present invention, as mentioned above, its good manufacturability is suitable for and produces the needs that its technical performance index all can satisfy the two-forty long haul communications systems in batches.It is that synchronizing signal desirable in the two-forty optical fiber telecommunications system is extracted the SAW filter.
To give detailed complete ground to details of the present invention by introduction below to one embodiment of the invention
Fig. 1 is one embodiment of the invention structural upright schematic diagram.(1) is four interdigital transducers among the figure, and (2) are three interdigital transducers, and (3) are electric screen bar between transducer, (4) be the quartz piezoelectric crystal sheet, (5) are input-output line, and (6) are the metallic shield box, (7) be bonded adhesives, (8) are lid, and (9) are sound-absorbing material.
(a) and the planar structure schematic diagram that (b) is respectively three interdigital transducers (2) and four interdigital transducers (1) among Fig. 1 among Fig. 2.λ is a centre frequency surface acoustic wave wavelength among the figure (b), and (3 λ)/4 are width between two electrode groups, and A-A-B-B is that per 4 interdigital groups of types distribute.
Fig. 3 is the measuring frequency-attenuation characteristic of Fig. 1 SAW filter.
Last figure complete display ground has shown structure of the present invention and performance thereof.
Embodiment of the invention SAW filter as mentioned above, is to adopt transverse type (disresonance device formula) filter construction, as shown in Figure 1.Input and output transducer (1) is the combined electrode transducer with (2).This type transducer can be offset the reflected wave in inner between its electrode, refer to that with the division commonly used of general SAW filter the type electrode compares, and under identical process conditions, upper limit operating frequency can double.In order to improve the inhibitory action of its stopband, transducer (1) and (2) are adopted the transducer of 3 interdigital groups of types and 4 interdigital groups of types respectively, as (a) among Fig. 2 with (b) shown in the figure its interdigital be that three or tetrad are arranged.Four interdigital groups of each cycles of type are A-A-B-B(Fig. 2); Three interdigital groups of each cycles of type are A '-A '-B '-B ' (not shown).Transducer two interdigital electrode face width degree are (3 λ)/4.λ is a centre frequency surface wave wavelength in the formula.It is by to 650 that substrate (4) is gone up transducer (1) and (2)
Aluminium vacuum coating photoetching and make, its centre frequency is 139.264MHZ
Greater than 700-800, the interdigitated input and output transducing on the substrate (4) is respectively 57 cycles, with the transducer in 73 cycles in order to obtain filter load Q value (that is (fo)/(Δ f)).
In order to obtain good electric screen characteristic, add an electric screen bar between transducer (1) and (2).Transducer (1) is selected 1425 microns for use with (2) aperture, is 50 ohm thereby make output input impedance, to satisfy the requirement that is complementary with external circuit impedance.
In the embodiment, substrate (4) adopts 37 ° of 50 ' ST to cut single minute surface quartz piezoelectric crystal sheet, and its temperature coefficient is 10
-6/ ℃, to satisfy this SAW filter requirement Q 〉=700-800.
Sound-absorbing material in the example (9) adopts plumbous rubber, as mentioned above, propagates into the SAW ripple signal of substrate (4) end face in order to absorption, eliminates the second-order effects that causes thus.Adhesive glue (7) adopts 207 glue of mixing silver powder, and as mentioned above, this glue not only has the strong bond effect, also has to absorb because the unwanted bulk wave signal that substrate (4) produces.Shielding box (6) adopts the can of 31 * 15 * 5.5mm, with satisfy SAW filter housing housing width with operating frequency wavelength ratio λ C/ λ＜＜1(λ C cavity cut-off wavelength, λ is the cavity operation wavelength).Isolation is α (dB)=27.25((d)/(a) between two transducers (1) and (2)), d is a distance between two transducers (1) and (2) in the formula, a is a housing width.As can be seen from the above equation, big more at interval, cavity is narrow more, and electric feedthrough is low more
SAW synchronizing signal extraction filter of the present invention requires the Q value more than or equal to 700, this means that the filter relative bandwidth is very narrow, be 170KHZ, less than Q=(fo)/(Δ f), therefore, adjust to accurately that centre frequency is a very difficult job, generally require the centre frequency accuracy at 60-70PPm, we reach this accuracy by the following method.Promptly this SAW filter center frequency 139.262MHZ accuracy is transferred in 60-70PPm.
1, control substrate (4) is gone up the aluminum metal film thickness 600
-700
In.Because at metal membrane material one regularly, thickness of metal film is thick more, acoustic surface wave propagation speed is low more.
2, be adjusted at substrate (4) axis of figure and change the SAW propagation velocity to angle with X-axis.
Claims (7)
1, synchronizing signal extracting sound surface wave filter, it is characterized in that having on it-to hob calcium carbide English crystal wafer be substrate to ST, on its sheet minute surface, constitute a pair of its electrode and be configured to 3 interdigital transducers and 4 interdigital transducers, each cycle is respectively A-A-B-B, A '-A '-B '-B ' respectively is the surface acoustic wave input and output reversible transducer of 57 groups and 73 groups; One electric screen thing is set between its transducer, is used for preventing that electrical input signal from directly passing to output transducer; Be coated with the jelly that bulk wave signal that one deck can attract substrates produces at work has the strong bond effect again at its substrate reverse side; At the substrate end face one suction ripple material is set and causes second-order effects because of it to absorb the SAW and the elimination of passing to the substrate end face along the direction of propagation; Selecting its shell housing width and operating frequency wavelength ratio for use is λ c/ λ＞＞1, selects for use on the control substrate minute surface thickness of metal film 600
-700
Adjust its centre frequency precision in the scope in 60-70PPm.
2, according to the SAW filter substrate of claim 1 regulation, it is characterized in that its temperature coefficient is 10
-6/ ℃
3, according to the input and output transducer of the SAW filter of claim 1 regulation, it is characterized in that its aperture is 1425 microns.
4,, it is characterized in that width is (3 λ)/4 between its interdigital electrode group according to the input and output transducer of claim 1 regulation.
5, according to the suction ripple bonding jelly of claim 1 regulation, it is characterized in that adopting 207 adhesive glue that are mixed with silver powder.
6, according to the suction ripple material on the substrate end face of claim 1 regulation, it is characterized in that adopting plumbous rubber.
7, shell housing width and the operating frequency wavelength ratio according to claim 1 regulation is λ C/ λ＞＞1, it is characterized in that adopting 31 * 15 * 5, the can of 5mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 88103334 CN1011934B (en) | 1988-06-07 | 1988-06-07 | Synchronizing signal extracting sound surface wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 88103334 CN1011934B (en) | 1988-06-07 | 1988-06-07 | Synchronizing signal extracting sound surface wave filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1038556A true CN1038556A (en) | 1990-01-03 |
| CN1011934B CN1011934B (en) | 1991-03-06 |
Family
ID=4832546
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 88103334 Expired CN1011934B (en) | 1988-06-07 | 1988-06-07 | Synchronizing signal extracting sound surface wave filter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1011934B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103163217A (en) * | 2013-03-07 | 2013-06-19 | 浙江工商大学 | Sound surface wave resonator series detection and detection method |
| CN106535606A (en) * | 2016-12-30 | 2017-03-22 | 深圳天珑无线科技有限公司 | Radio frequency shielding device |
| CN107359687A (en) * | 2017-08-22 | 2017-11-17 | 深圳传音控股有限公司 | User terminal and its wireless charging method |
| CN109462384A (en) * | 2018-12-28 | 2019-03-12 | 河北时硕微芯科技有限公司 | A kind of SAW filter and production method |
-
1988
- 1988-06-07 CN CN 88103334 patent/CN1011934B/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103163217A (en) * | 2013-03-07 | 2013-06-19 | 浙江工商大学 | Sound surface wave resonator series detection and detection method |
| CN106535606A (en) * | 2016-12-30 | 2017-03-22 | 深圳天珑无线科技有限公司 | Radio frequency shielding device |
| CN106535606B (en) * | 2016-12-30 | 2024-05-10 | 深圳天珑无线科技有限公司 | Radio frequency shielding device |
| CN107359687A (en) * | 2017-08-22 | 2017-11-17 | 深圳传音控股有限公司 | User terminal and its wireless charging method |
| CN109462384A (en) * | 2018-12-28 | 2019-03-12 | 河北时硕微芯科技有限公司 | A kind of SAW filter and production method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1011934B (en) | 1991-03-06 |
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