Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
  • H03H9/14597—Matching SAW transducers to external electrical circuits
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
  • H03H9/0023—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output
  • H03H9/0028—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using surface acoustic wave devices
  • H03H9/0033—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using surface acoustic wave devices having one acoustic track only
  • H03H9/0038—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using surface acoustic wave devices having one acoustic track only the balanced terminals being on the same side of the track
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
  • H03H9/14502—Surface acoustic wave [SAW] transducers for a particular purpose
  • H03H9/14514—Broad band transducers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
  • H03H9/14588—Horizontally-split transducers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
  • H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
  • H03H9/72—Networks using surface acoustic waves

Definitions

• the invention relates to a filter arrangement which comprises a DMS filter and has a filter function with a steep right flank.
• LTE have high requirements regarding
• Low-loss filters with high bandwidth can be realized as DMS filters.
• strain gauge filters have the disadvantage that the upper flank of the passband drops only very flatly and has only a low selectivity compared with a band adjacent to the upper frequency range. The close selection is therefore moderate.
• Object of the present invention is therefore, a
• the strain gauge filter has first and second transducers, which are in particular arranged alternately on a piezoelectric substrate between two reflectors.
• the first transducers are coupled to one input or output of the device, the second transducers to the other from the output or input of the device.
• DMS filter at least one of the transducers of a type selected from first or second transducer, but preferably all transducers of a type symmetrically divided into two partial transducers connected in parallel electrically.
• the two partial transducers are now separated from their original position in the undivided transducer slightly less than half a wavelength ⁇ plus n times ⁇ apart, where n is an integer greater than or equal to zero (0, 1, 2, etc.).
• n is an integer greater than or equal to zero (0, 1, 2, etc.).
• Original converter corresponds, it is so dimensioned that the generated by the two partial transducers
• the converter split into two partial converters will still be considered a converter (with two halves or two
• Sub-converters regardless of whether there are other elements of the filter in between, e.g. Reflector strips are arranged.
• the strain gauge filter is constructed symmetrically, in particular with respect to the transducers, and has an axis symmetry with respect to the arrangement of the individual transducers, the mirror axis of which passes through one of the transducers
• Transducer or passes through the middle between the two partial transducers. This results in the DMS filter having an odd number of transducers.
• Propagation direction of the acoustic wave in the DMS filter is also achieved a high symmetry of the individual signal components, with an exact transfer function can be secured.
• the strain gauge filter can be electrically connected on both sides single-ended. However, it is also possible to operate at least one of the sides of input and output with symmetrical signal processing and thus to provide a balanced input or output of the filter arrangement.
• Arrangement with the new DMS filter is characterized by that it can be produced without additional effort and only has a slightly higher transducer length compared to the known strain gauge filter, but with respect to the
• Partial transducers increased.
• the increase in the number of fingers in the split transducers is the greater the closer the transmission zero point generated by the splitting is at the upper band edge.
• the total number of electrode fingers in the two partial transducers is greater than the sum of the
• Electrode fingers in the undivided transducer of the corresponding known filter are Electrode fingers in the undivided transducer of the corresponding known filter.
• the two partial transducers are moved so far apart that the distance between the two partial transducers, that between the facing each other
• Subverters generated signals by appropriate sizing of the distance so placed that the resonance near the upper edge of the passband comes to rest, the antiresonance, however, outside, but close to the passband.
• a metallization is applied in such a way that the metallization thickness does not change too much across the transducer or the two partial transducers in order not to generate any discontinuities.
• a suitable metallization therefore consists of a strip pattern, that is to say an arrangement of mutually parallel strips whose spacing is selected to be similar to that of the electrode fingers in the partial transducers.
• the DMS filter is characterized by at least one converter subdivided in partial converters. However, according to one embodiment, two or more transducers of a type selected from first and second transducers are divided into sub-transducers in the same or similar manner.
• all transducers of one type are divided into partial transducers. If not all converters are divided into partial transducers, the distribution is symmetrical so as not to jeopardize the good filter properties. This means that the split transducers are distributed symmetrically in the filter.
• the filter for symmetrical operation is again symmetrical and has an odd total number of first and second transducers. Due to the symmetry and the
• Converter type is formed, of which the larger number in the DMS filter is present.
• Transducers of one type are split into partial transducers. These can be individual transducers. Preferably, all transducers of this type are split. It is also possible to divide all converters except for the two mentioned, in the DMS filter outer converter.
• the signals of these two outer transducers can be used to an additional attenuation pole, the additional
• an arrangement according to the invention contains, in addition to the DMS filter, at least one series resonator connected in series with the DMS filter and a parallel resonator connected in parallel thereto.
• the two resonators which are advantageously connected to the input of the filter arrangement, an improved performance stability of the arrangement is achieved. If the resonance frequencies of the resonators are selected to be suitable, they can also be used to form the passband and to further sharpen or control the upper one
• Passband flank can be used.
• the arrangement may comprise further resonators connected in series or parallel to the DMS filter.
• the further resonators can one or more basic elements of a
• the filter arrangement comprises one coil each, which is connected in series with the input and output of the arrangement. With these connection coils is a
• Impedance transformation causes. For this purpose can
• Coils can also be switched parallel to the filter input or output.
• a capacitance is connected in parallel with a resonator to reduce its pole-to-zero distance. In this way it succeeds, a sharper
• capacitances are switched at least in parallel to the series resonators.
• pole-zero spacings are chosen differently for the resonators used in the arrangement. This can be done by using at least one bandwidth means in each of the resonators, with the aid of which the pole-zero distance can be changed and thus made different for different resonators.
• the values of the capacitances connected in parallel with the resonators can be used as bandwidth means
• Reduction of the temperature coefficient of the frequency is applied to adjust differently.
• the height of a SiO 2 layer covering the filter arrangement can be varied particularly easily.
• the parallel resonators of the arrangement are each in
• Parallel branches arranged that connect a serial signal line to a ground terminal.
• the parallel branches may be connected to the ground terminal via a series inductance. It is possible to connect each parallel branch with a separate series inductance to the ground connection.
• the metallization which separates the partial transducers is designed as an electrically floating or electrically short-circuited fringe pattern.
• fingerab ⁇ liens, finger widths and the measured from finger center to finger center pitch in the transition region of a transducer to change the adjacent transducer or from a transducer to the reflector or a transducer to the formed as a striped pattern metallization and in particular to reduce.
• up to n terminal electrode fingers are varied in terms of width and / or distance in order to minimize the changes of these parameters from finger to finger.
• Stripe pattern is set to a value between 3 and 12. n is preferably larger, the greater the distance between the terminal fingers deviates from a multiple of ⁇ / 2 without this variation.
• Figure 2 shows an inventive DMS filter with a
• FIG. 3 shows a DMS filter according to the invention, in which the
• FIG. 4 shows an inventive DMS filter, wherein the
• FIG. 5 shows a strain gauge filter according to the invention, in which two transducers are subdivided into subtransducers separated by a metallic fringe pattern
• Figure 6 shows an arrangement with a DMS filter, the one
• FIG. 7 shows the passage behavior of a filter arrangement according to the invention in comparison with the passage behavior of a filter arrangement known per se with a conventional DMS filter
• FIG. 8 shows a known DMS filter with nine transducers
• FIG. 9 shows a strain gauge filter according to the invention with originally nine transducers, of which four are subdivided into partial transducers
• FIG. 10 shows the transmittance behavior of the strain gauge filter according to the invention shown in FIG
• FIG 11 shows an inventive DMS filter with originally seven transducers, two of which are divided into partial transducers.
• Figure 1 shows a schematic representation of a known per se DMS filter with three transducers. This comprises between a first reflector Rl and a second
• Reflector R2 two first transducer Wll, W12, between which a second transducer W20 is arranged.
• the first transducers are connected in parallel to one another and, for example, coupled to the filter input.
• the second converter W20 is
• Figure 2 shows a first simple embodiment of a DMS filter according to the invention with originally three transducers.
• the converter of one type here the second converter
• T20, ⁇ 20 ⁇ the partial transducers
• the first converters Wll, W12 flank the two
• Partial converter in a conventional manner. Because of the division into partial transducers to increase the total number of electrode fingers for the entire unit of first and second partial converter T20, ⁇ 20 ⁇ compared to the undivided transducer of the known strain gauge structure. The distance between first and second
• Partial transducers T20, ⁇ 20 ⁇ is chosen larger than a finger-finger distance in the transducer and also greater than the distances between the transducers known DMS filter.
• FIG. 3 shows a similar DMS filter according to the invention with the same number of transducers and partial transducers, in which, however, the distance D between the two partial transducers T20, ⁇ 20 ⁇ is further increased.
• the distance D may be a multiple of the distance between a sub-transducer and the directly adjacent "conventional" transducer.
• Figure 4 shows a further inventive DMS filter with initially three transducers and in partial transducers T20, ⁇ 20 in which is ⁇ divided central transducer between the two partial transducers T20, inserted ⁇ 20 ⁇ metallization M in the form of a metallic strip pattern.
• the strip ⁇ pattern is like a conventional reflector formed, but preferably has a lower number of reflector ⁇ stripe on to an acoustic transmission to
• the functionality of the strain gauge filter according to the invention is the degree of permeability of the
• Stripe pattern of metallization M as long as one
• FIG. 5 shows a strain gauge filter according to the invention with originally three transducers as shown in FIG. 1, in which the two first transducers, which correspond to those in the figure above
• arranged connections are divided into partial transducers TU, ⁇ 11 ⁇ or T12, T12 ⁇ are divided.
• the middle converter which is a second converter W20, remains undivided.
• a metallization Mll, M12 inserted is designed as an electrically shorted striped pattern.
• the two partial transducers of a split converter are each electrically connected in parallel.
• the two split first converters can be electrically connected in parallel, so that a single-ended connection of four in total can be connected in parallel
• FIG. 6 shows an arrangement how the DMS filter according to the invention can be connected to further circuit components, in particular resonators, to form an expanded filter arrangement.
• the DMS filter DMS is shown only diagrammatically and may be implemented differently with any number of split and undivided transducers.
• Filter arrangements according to the invention comprise DMS filters DMS according to the invention, in which at least one of the transducers is subdivided into partial transducers.
• DMS filters DMS In series connection with the DMS filter DMS, three series resonators RS1, RS2 and RS3 are connected between input and output of the arrangement. Parallel to this series connection two parallel arms are connected to ground, in each of which a parallel ⁇ resonator RP1, RP2 is arranged.
• At least the series resonators RS are each connected in parallel with a capacitor CS.
• the parallel resonators RP are with a
• Capacitance CP connected in parallel.
• the series connection or the arrangement is respectively connected to a serial coil LSI, LS2, wherein the serial coil LSI, for example, on the input side, the serial coil LS2 can be arranged on the output side.
• Input and output of the arrangement can also
• the parallel branches are each connected via a series inductance LP1, LP2 to ground.
• LP1, LP2 series inductance
• FIG. 7 shows the transfer function S21 of the two arrangements, wherein the curve K1 corresponds to an arrangement according to the invention, but the curve K2 corresponds to the arrangement with the known DMS filter from FIG.
• the curve K of the arrangement according to Inventive ⁇ shows the greatest benefits in the area of the upper pass-band edge which substantially steeper fall to herein as the curve K2 of the arrangement with the known DMS filter.
• the damping is improved in the near stopband.
• both arrangements show almost the same behavior, so that the curves K1 and K2 are almost congruent there.
• Figure 8 shows a per se known DMS filter with nine
• Reflectors Rl, R2 are arranged. All first transducers may be connected in parallel to one terminal of the filter, while the four second transducers may also be connected in parallel to a second terminal of the filter.
• FIG. 9 shows an embodiment according to the invention of such a nine-converter DMS filter.
• all the second transducers (W21 to W24 from FIG. 8) are subdivided into partial transducers T21 to T24, wherein a metallization M2 is arranged between each two partial transducers T2
• Strip pattern can be formed. All partial transducers T21 to T24 can be connected in parallel with a filter connection
• the DMS filter according to the invention shown in Figure 9 can be connected in an arrangement such as shown in Figure 6, interconnected.
• Figure 10 shows the ⁇ tragungsfunktion such an arrangement, as compared with that of an arrangement in the switching elements in accordance with Figure 6 with a DMS filter shown in FIG 8 are connected.
• Curve K1 shows the filter arrangement with the DMS filter according to FIG. 9, while curve K2 shows the filter arrangement with the known DMS filter according to FIG. 8.
• the improvement is predominantly in the region above the pass band and in the near stop band.
• Antiresonance is placed at such a frequency that creates an additional attenuation pole in the near stopband that results in a better attenuation level in this range.
• the invention is particularly advantageous for broadband filters and filter arrangements, it can also be advantageous for narrowband filters. Even narrow passbands must be against adjacent bands with low
• FIG. 11 shows a further variant of a strain gauge filter of the filter arrangement according to the invention.
• a strain gauge filter of the filter arrangement Starting from a known DMS filter with seven transducers are of the original four second transducers W21 to W24, only the two middle second transducer W22, W23 into partial transducers T22, T22 or T23 ⁇ , ⁇ 23 ⁇ divided. The two outer second transducers W21 and W24 remain undivided. Between each two partial transducers resulting from a transducer splitting, a partially transmissive reflector can be arranged, as also shown in the figure.
• the distance between the outer second transducers W21, W24 to the respective adjacent reflector Rl or R2 is designed such that also here the desired effect of the signal cancellation for frequencies in the near stopband occurs.
• Transducers can be achieved. Also with this arrangement is a filter with a steeper upper passband edge and a
• Filter arrangements may contain arbitrarily designed strain gage filters, provided that only one of the transducers is divided in accordance with the invention and desired additional antiresonance which serves to cancel out signals at frequencies in the near stopband.
• Filter input initially provide a parallel resonator and not, as shown in Figure 6, a series resonator.
• Filter arrangements according to the invention may be formed on different piezoelectric substrates
• lithium niobate for example, lithium niobate or lithium tantalate.
• Narrow-band filters according to the invention can also be used
• Advantages of the invention can be achieved independently of the coupling strength of the substrate.

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• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
• Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Cited By (1)

Families Citing this family (5)

Citations (3)

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• 2014
  • 2014-12-05 DE DE102014118000.3A patent/DE102014118000A1/de not_active Withdrawn
• 2015
  • 2015-10-15 WO PCT/EP2015/073903 patent/WO2016087106A1/de not_active Ceased
  • 2015-10-15 EP EP15780896.5A patent/EP3228006B1/de active Active
  • 2015-10-15 JP JP2017529781A patent/JP2018501714A/ja active Pending
  • 2015-10-15 US US15/531,262 patent/US10340884B2/en active Active
  • 2015-10-15 CN CN201580063012.1A patent/CN107005218B/zh active Active

Patent Citations (3)

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