CN1286485A - Acoustic surface wave MF filter for European cordless digital telephone - Google Patents
Acoustic surface wave MF filter for European cordless digital telephone Download PDFInfo
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- CN1286485A CN1286485A CN 99119218 CN99119218A CN1286485A CN 1286485 A CN1286485 A CN 1286485A CN 99119218 CN99119218 CN 99119218 CN 99119218 A CN99119218 A CN 99119218A CN 1286485 A CN1286485 A CN 1286485A
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Abstract
An acoustic surface wave MF filter for European cordless digital telephone is composed of piezoelectric substrate and mirror impedence coupling structure consisting of 6 interdigital transducers, and features that the input and output transducers are single-phase monodirectional one and the optimal width of reflection electrode is 1/8 of wavelength. Its advantages are less reflection electrodes, short input and output transducer, small size and broader bandwidth of input and output transducers.
Description
The present invention relates to a kind of Digital European Cordless Telephone (DECT) system surface acoustic wave intermediate-frequency filter that is applied to, refer in particular to a kind of lower insertion loss that has, high stopband suppresses, and the little Surface Acoustic Wave Filter of volume.
The centre frequency of Digital European Cordless Telephone intermediate-frequency filter is 110.592MHz or 112.32MHz, and three dB bandwidth is greater than 1.152MHz, and the 30dB bandwidth is less than 3.456MHz, and requires Insertion Loss low, and volume is little.
The DECT surface acoustic wave intermediate-frequency filter that prior art exists, as the said employing single phase unidirectional transducer design of U.S. Vectron international technology firm catalogue, its shortcoming is an Insertion Loss higher (11.9～13.5dB), bandwidth is not enough, and (0.965MHz～1.04MHz), volume is (12.2 * 6.8 * 3mm greatly
3) or as the said employing single phase unidirectional transducer of 1995 IEEE Ultrasonics Symp.Proc.PP51-54 make the binary channels reflection grating filter structural design of input and output transducer, its shortcoming is Insertion Loss higher (8dB), bandwidth not enough (1.1MHz).
In IEEE 1991 Ultrasonics Symposium Proceedings PP235-239, said image impedance coupling filter can obtain low insertion loss, and high stopband suppresses, big bandwidth and little size.Basic structure as shown in Figure 1, it is by piezoelectric substrate 2 and the coupled transducers 3 and 8 that is produced on the substrate 2, be positioned over the input transducer 4 and 5 of transducer 3 both sides symmetrically along the acoustic surface wave propagation direction, reflecting grating array 6 and 7, be positioned over output transducer 9 and 10, reflecting grating array 11 and 12 compositions of transducer 8 both sides symmetrically along the acoustic surface wave propagation direction.This structure has mainly been utilized the impedance operator of coupled transducers, as the finger logarithm N=1.5/K of coupled transducers
2The time, (K
2Electromechanical coupling factor for substrate material) near the coupled transducers synchronizing frequency in the certain limit, anti-in the impedance of coupled transducers is zero, be pure resistance characteristic, energy is transferred to another coupled transducers fully from a coupled transducers, form the passband of filter, along with this scope of frequency departure, resistance increases in the impedance of coupled transducers, energy is reflected by major part, and loss increases sharply, along with frequency further departs from, the impedance of coupled transducers becomes based on resistance, energy is almost all reflected, and forms stopband, and this structure can obtain steeper transition band.Reflecting grating array 6,7,11 and 12 effect are the two-way losses that reduces the input and output transducer.The shortcoming of this structure is that the two-way loss of adopting reflecting grating array to reduce the input and output transducer makes sizes of substrate bigger, and bandwidth is subjected to certain limitation.
A kind of Surface Acoustic Wave Filter of expectation development can reduce volume, and can increase the bandwidth of filter.
The objective of the invention is to propose the surface acoustic wave intermediate-frequency filter that a kind of Digital European Cordless Telephone of being made up of piezoelectric substrate and the interdigital transducer on piezoelectric substrate is used, it not only reduces volume, and increased bandwidth, thereby solved existing problem in the prior art.
The technical solution adopted in the present invention is that it mainly is made up of piezoelectric substrate and six interdigital transducers that are produced on the piezoelectric substrate.Wherein two edges using as coupled transducers are placed side by side perpendicular to the acoustic surface wave propagation direction, are connected in parallel on the electricity; Be placed on the both sides of a coupled transducers symmetrically along the sonic propagation direction as two interdigital transducers using of input transducer; And be connected in parallel on the electricity; Two interdigital transducers in addition of using as output transducer are positioned over the both sides of another coupled transducers symmetrically along the acoustic propagation direction, and are connected in parallel on the electricity.Coupled transducers adopts withdraw-weighted.Described piezoelectric substrate adopts 36 ° of Y cuttings of rotation, and X propagates lithium tantalate; Or rotating 42 ° of Y cuttings, X propagates lithium tantalate; Or rotate 64 ° of Y cuttings, and X propagates lithium niobate, or rotates 41 ° of Y cuttings, and X propagates lithium niobate or 128 ° of Y cutting X propagate lithium niobate, and perhaps Y cutting Z propagates lithium niobate.It is characterized in that: input, output transducer adopt single phase unidirectional transducer, to adopt the reflecting electrode width weighed single phase unidirectional transducer of inventor's invention (CN98117320.9), the reflecting electrode width is from 1/8th wavelength to eight/three-wavelength, and the best is 1/8th wavelength.
The reflection coefficient of interdigital electrode mainly comes from interdigital electrode should to piezoelectricity short-circuiting effect, mechanics load effect and the acoustic-electric revival of piezoelectric substrate.Preceding two only relevant with the material of piezoelectric substrate and interdigital electrode, irrelevant with external circuit, be called internal reflection.The reflection of reflecting electrode includes only preceding two.The piezoelectricity short circuit is directly proportional with the electromechanical coupling factor of substrate material to the contribution of reflection coefficient, and more relevant than (being the ratio of reflecting electrode width and 1/2nd wavelength) with the metallization of reflecting electrode.For the high coupling coefficient material, as the lithium niobate (LiNbO of various cut types
3) 36 ° of Y of rotation cut, X passes and rotates 42 ° of Y and cut, and X passes lithium tantalate and (writes a Chinese character in simplified form Y36 ° of LiTaO
3With Y42 ° of LiTaO
3) reflection coefficient mainly comes from the contribution of piezoelectricity short circuit.
The invention has the advantages that: adopt the present invention to need less reflecting electrode promptly can obtain same one-way, promptly input and output transducer length can be shorter, can shorten the length of filter like this, and is same, can improve the bandwidth of input and output transducer.
Fig. 1 is the floor map of a conventional surface acoustic wave image impedance coupling filter;
Fig. 2 is that reflecting electrode piezoelectricity short circuit reflection coefficient of the present invention is with the curve chart of metallization than variation;
Fig. 3 is a structure chart of showing embodiment of the invention DECT intermediate-frequency filter;
Fig. 4 is the frequency response curve of embodiment of the invention DECT intermediate-frequency filter.
Further specify preferred embodiment of the present invention in conjunction with above-mentioned each accompanying drawing now.
In the embodiment shown in fig. 3, the piezoelectric substrate 2 of filter 13 adopts Y36 ° of LiTaO
3Upper surface plating aluminium at piezoelectric substrate 2, make transducer 14,15,16,17,18 and 19 then by lithography, transducer 14 and 17 is a coupled transducers, adopts withdraw-weighted, length overall is 98 wavelength, effectively refer to 32 pairs of logarithms, be spaced apart quarter-wave between finger 21 and the finger, the centre-to-centre spacing between the finger 21 is the integral multiple of 2 wavelength, the width of finger 22 is (2n-3/4) wavelength, and n is 1 to 4 positive integer.Transducer 15 and 16 is the input transducer, and transducer 18 and 19 is an output transducer, refers to that logarithm is 28 pairs, and the aperture is 20 wavelength, and the width of reflecting electrode 20 is 1/8th wavelength, it and adjacent electrode be spaced apart quarter-wave.In order to strengthen reflection, the not weighting of reflecting electrode battle array, each cycle is all placed a reflecting electrode 20,28 altogether.If minimum 40 wavelength of length that adopt prior art input shown in Figure 1, output transducer to add reflecting grating array, sizes of substrate is than adopting the present invention to be about 1mm.
Fig. 2 is the relation of the piezoelectricity short circuit of reflecting electrode the reflection coefficient amplitude Re that causes and the ratio that metallizes, wherein Ks
2It is the electromechanical coupling factor of substrate material.From Fig. 2 as seen, metallization equals at 0.25 o'clock, and the reflection that the piezoelectricity short circuit causes is the strongest.
Fig. 4 is a frequency response curve embodiment illustrated in fig. 3, inserts loss less than 4dB, and three dB bandwidth is greater than 1.3MHz, and the 40dB bandwidth is less than 3.2MHz, and stopband suppresses to satisfy fully greater than 50MB the requirement of DECT system.Overall dimensions are 11.4 * 5 * 2.2mm
3Compare Insertion Loss littler (11.9dB), bandwidth wideer (0.965MHz), littler (12.2 * 6.8 * 3mm of volume with U.S. Vectron company product
3).Compare Insertion Loss littler (8dB), bandwidth wideer (1.1MHz) with the product of Siemens Company.
The present invention not only can be used to design the Digital European Cordless Telephone intermediate-frequency filter, can also be used to design other Surface Acoustic Wave Filter.
Claims (5)
1. a Digital European Cordless Telephone surface acoustic wave intermediate-frequency filter is characterized in that, it is made up of piezoelectric substrate and six interdigital transducers that are produced on the piezoelectric substrate; Wherein two edges using as coupled transducers are placed side by side perpendicular to the acoustic surface wave propagation direction, are connected in parallel on the electricity; Two interdigital transducers using as the input transducer are placed on the both sides of a coupled transducers symmetrically along the sonic propagation direction, and are connected in parallel on the electricity; Two interdigital transducers in addition of using as output transducer are positioned over the both sides of another coupled transducers symmetrically along the acoustic propagation direction, and are connected in parallel on the electricity; Coupled transducers adopts withdraw-weighted, it is characterized in that: input, output transducer adopt single phase unidirectional transducer, and the width of reflecting electrode is 1/8th wavelength to eight/three-wavelength.
2. press the described Digital European Cordless Telephone of claim 1 with surface acoustic wave surface acoustic wave intermediate-frequency filter, it is characterized in that said input, output transducer are single-phase transducers.
3. by the described Digital European Cordless Telephone surface acoustic wave surface acoustic wave intermediate-frequency filter of claim 1, it is characterized in that, said reflecting electrode width wavelength, optimum width is 1/8th wavelength.
4. according to the described Digital European Cordless Telephone of claim 1 surface acoustic wave intermediate-frequency filter, it is characterized in that described piezoelectric substrate adopts 36 ° of Y cuttings of rotation, X propagates lithium tantalate; Or rotate 42 ° of Y cutting X and propagate lithium tantalate; Or rotate 64 ° of Y and cut X propagation lithium niobates, or rotate 41 ° of Y cutting X and propagate lithium niobates or 128 ° of Y cutting X propagation lithium niobates, perhaps Y cuts Z and propagates lithium niobates.
5. according to the described Digital European Cordless Telephone of claim 1 surface acoustic wave intermediate-frequency filter, it is characterized in that, said coupled transducers, it adopts withdrawal weighted transducer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99119218 CN1086244C (en) | 1999-08-26 | 1999-08-26 | Acoustic surface wave Mf filter for European cordless digital telephone |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99119218 CN1086244C (en) | 1999-08-26 | 1999-08-26 | Acoustic surface wave Mf filter for European cordless digital telephone |
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| Publication Number | Publication Date |
|---|---|
| CN1286485A true CN1286485A (en) | 2001-03-07 |
| CN1086244C CN1086244C (en) | 2002-06-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99119218 Expired - Fee Related CN1086244C (en) | 1999-08-26 | 1999-08-26 | Acoustic surface wave Mf filter for European cordless digital telephone |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6815868B2 (en) | 2001-04-09 | 2004-11-09 | Murata Manufacturing Co., Ltd. | Surface acoustic wave apparatus and communication unit |
| CN107689784A (en) * | 2016-08-05 | 2018-02-13 | 株式会社村田制作所 | High-frequency model |
| CN112422099A (en) * | 2020-11-25 | 2021-02-26 | 成都燎原星光电子有限责任公司 | Chip structure of broadband low-loss surface acoustic wave filter |
| CN112702040A (en) * | 2021-02-09 | 2021-04-23 | 中国电子科技集团公司第二十六研究所 | Single crystal film surface acoustic wave filter and method for reducing baseband and improving out-of-band rejection |
-
1999
- 1999-08-26 CN CN 99119218 patent/CN1086244C/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6815868B2 (en) | 2001-04-09 | 2004-11-09 | Murata Manufacturing Co., Ltd. | Surface acoustic wave apparatus and communication unit |
| CN107689784A (en) * | 2016-08-05 | 2018-02-13 | 株式会社村田制作所 | High-frequency model |
| CN112422099A (en) * | 2020-11-25 | 2021-02-26 | 成都燎原星光电子有限责任公司 | Chip structure of broadband low-loss surface acoustic wave filter |
| CN112702040A (en) * | 2021-02-09 | 2021-04-23 | 中国电子科技集团公司第二十六研究所 | Single crystal film surface acoustic wave filter and method for reducing baseband and improving out-of-band rejection |
| CN112702040B (en) * | 2021-02-09 | 2024-03-12 | 中电科技集团重庆声光电有限公司 | Single crystal film acoustic surface wave filter and method for reducing baseband and improving out-of-band rejection |
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| Publication number | Publication date |
|---|---|
| CN1086244C (en) | 2002-06-12 |
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