DE102017120304A1 - Electroacoustic resonator with increased power stability and improved linearity, RF filters and multiplexers - Google Patents

Abstract

There is provided an electroacoustic resonator having increased power resistance and improved linearity. The resonator has two sets of interdigital structures. Both sets are electrically connected in parallel with respect to each other. At least two interdigital structures of the first set are connected in series. Each interdigital structure of the first set corresponds with respect to the connection scheme of an interdigital structure of the second set.

Description

The present invention relates to electroacoustic resonators that can be used in RF filters. RF filters can be used in multiplexers.

The tendency for miniaturization on the one hand and the tendency to increase a number of functions and bands of a mobile communication device on the other hand lead to contradictory requirements for corresponding filters. In addition, new requirements such as e.g. HPUE requirements for time-division LTE systems, high-performance RF filters. However, it is difficult to achieve high performance resistance if linearity requirements should be met at the same time. In particular, generating harmonics is problematic when the frequencies of harmonics are close to downlink frequencies of other standards.

The posts "Generation mechanisms of second-order nonlinearity in surface acoustic wave devices", K. Hashimoto, R. Kodaira, T. Omori, IEEE International Ultrasonic Symposium Proceedings 2014 and "Application of a rigorous non-linear P-matrix method to the simulation of third order intermodulation in test devices in duplexers", M. Mayer, W. Ruile, J. Johnson, J. Kiwitt, R. San Jose, E. Schmidhammer , I. Bleyl, K. Wagner, E. Mayer, IEEE International Ultrasonic Symposium Proceedings 2014 refer to mechanisms that affect the generation of nonlinearity effects in surface acoustic wave components.

Accordingly, it is desirable to have electroacoustic components that allow for an increase in RF power, and that allow for a reduction in spurious, non-linear contributions.

For this purpose, an electroacoustic resonator, an RF filter and a multiplexer according to the independent claim are provided. Dependent claims provide preferred embodiments.

The electroacoustic resonator, which has increased power stability and allows improved linearity, comprises a first set of I interdigital structures and a second set of I interdigital structures. The number I of interdigital structures per set is greater than or equal to zero. Some of the interdigital structures of the first set are connected to the input terminal of the first set, some of the interdigital structures of the first set are connected to the output terminal of the first set. Symmetrically, some of the interdigital structures of the second set are connected to the input terminal of the second set, some of the interdigital structures of the second set are connected to the output terminal of the second set. The first set of interdigital structures is electrically connected in parallel with the second set of interdigital structures, then input terminals S1 and S2 interconnected and output connections S1 and S2 are interconnected. In the first set of interdigital structures, at least two interdigital structures are connected in series or in parallel.

Each interdigital structure of the first set corresponds to an interdigital structure of the second set with respect to its connection scheme. The connection scheme of the first and second sets is symmetric.

The connection scheme may be the type of relationship regarding electrical connection of the interdigital structures, such as parallel or in series. Interdigital structures of S1 and S2 may be interconnected along a line of symmetry, thereby providing a parallel interconnection of a subsection of S1 with his counterpart in S2 form.

The symmetry may be a mirror symmetry with respect to the symmetry line. That is, the respective structures may have a mirrored shape in a staggered position.

However, the symmetry may also be translational symmetry. That is, the respective structures may have a similar or identical shape at a staggered position.

It is preferred that a relatively high degree of symmetry of the connection scheme is enforced. This helps in eliminating non-linear signal cancellation. In addition, small differences This leaves the possibility that a difference in terms of IDS is present, which could result in a fine optimization.

Therefore, an electroacoustic resonator is provided which has an even number of 2 × I = 4 or more interdigital structures. An interdigital structure may be a transducer-type interdigital structure that converts between RF signals and electroacoustic waves. By dividing the 2 × I interdigital structures into a first set and a second set, and by providing correspondences between the interdigital structures of the two sets with respect to the connection scheme, improvements are achieved in both the requirements of power durability and linearity. The correspondence between resonators of the two sets improves linearity unwanted contributions that are generated by an interdigital structure of a sentence, can be compensated by the corresponding interdigital structure of the other set. Improved power stability is achieved because cascading distributes the application of RF power to a larger area, which adds to further improvement in linearity due to reduced power density of RF power applied to a particular area element.

As a result, an electroacoustic resonator is provided which has a symmetry. The connection scheme of interdigital structures of S1 is symmetric along the symmetry line to the interconnection scheme of interdigital structures in S2 , In this context it is possible that at least two corresponding structures in S1 and S2 Designate structures of similar construction (ie geometry) and similar dimensions with respect to a length and a width of the structure. Of course, it is possible that corresponding interdigital structures have the same geometry and the same spatial dimensions.

It is possible that the electroacoustic resonator has I = 4 interdigital structures in the first set.

It is also possible that the interdigital structures in the first set are connected in series.

It is possible that the constructions of an interdigital structure of the first set and its corresponding interdigital structure in the second set are implemented with an antiparallel symmetry. Therefore, for the interdigital structure of the first set, which can trigger a nonlinear even order signal, there is a corresponding interdigital structure of the second set which can trigger a nonlinear even order signal of the same magnitude but opposite polarization. Due to the correspondence of the electrical configuration within each set and due to the parallel connection of the two sets, both unwanted excitations cancel each other and the linearity is improved. For this purpose, the geometry of the interdigital structure of the first set may be mirrored with respect to a symmetry line to obtain the geometry of the corresponding interdigital structure of the second set.

However, there is no need for each interdigital structure of the first set and its counterpart in the second set to have a strictly antisymmetric construction. Differences between the first set and the second set, which differ from a strictly antisymmetric construction, can help to eliminate unwanted harmonic signals.

In addition, the cascading of electroacoustic structures in the first set (and correspondingly the cascading of electroacoustic structures in the second set) offers the possibility of arranging resonators of the first set in a first group and further resonators of the first set in a second group. Correspondingly, resonators of the second set are also classified into a first and a second group. If each of the two sets of electroacoustic structures has four electroacoustic structures, then these four electroacoustic structures can be classified into two groups. Each group can have two electroacoustic structures.

Accordingly, it is possible that at least two corresponding interdigital structures have an antiparallel construction.

Moreover, it is possible that at least two corresponding interdigital structures are cascaded in parallel and have an antiparallel construction. In addition, it is possible that at least two corresponding interdigital structures have constructions different from an antiparallel construction.

In addition, it is possible that at least two corresponding interdigital structures are cascaded in series and have structures that are different from an antiparallel construction.

It is possible that at least two interdigital structures are arranged within the same acoustic track.

An acoustic track refers to the area on or in a piezoelectric material where electroacoustic waves propagate along one direction.

Interdigital structures within the same acoustic track may be acoustically separated by electroacoustic reflectors. However, it is possible that the structures may be acoustically coupled.

Accordingly, it is possible for at least two interdigital structures to be arranged between electroacoustic reflectors.

Electroacoustic reflectors confine acoustic energy to the area between the reflectors within an acoustic track.

The electroacoustic structures may have a transducer-like interdigital geometry where electrode fingers are disposed on a piezoelectric material and connected to a bus bar are interconnected. Excitation regions are disposed between adjacent electroacoustic fingers, which are electrically connected to the busbar. The distance between the center of an electrode finger and the center of an adjacent electrode finger mainly determines half the wavelength A / 2 of an acoustic wave of an operating frequency of the resonator. The electrode structures of a resonator may have a layer structure where two or more metals or alloys of a different composition are arranged one on top of the other. The electrode structures of an electroacoustic resonator may be covered with a dielectric material, such as a TCF (TCF) temperature compensation structure, to compensate for frequency drift caused by temperature. Such a TCF compensation layer may comprise a silicon oxide, such as a silicon dioxide. The piezoelectric substrate may be a monolithic piezoelectric material or a layer system comprising piezoelectric layers, dielectric layers and metal layers.

It is possible that an RF filter comprises one or more electroacoustic resonators as described above.

Such an electroacoustic resonator may be used in conjunction with other electroacoustic resonators in an electrical configuration to provide RF filters, e.g. Bandpass filter or bandstop filter to form. For example, in a ladder-like configuration, series resonators are electrically connected in series in a signal path. Parallel resonators arranged in transverse paths electrically connect the signal path to ground. In such an RF filter, one or some or all of the resonators may include the above-mentioned structures to enable power durability and linearity.

It is possible that one or more such RF filters are electrically interconnected to form a multiplexer. Therefore, a multiplexer may include one or more RF filters as described above. Multiplexers may be duplexers with a bandpass filter for transmit signals and a bandpass filter for receive signals. Between a received-signal bandpass filter (a reception filter) and a transmission-type band-pass filter (a transmission filter), an impedance matching circuit may be provided to electrically decouple the two filters. However, higher order multiplexers, e.g. Quad plexers comprising four bandpass filters or hex plexers comprising six bandpass filters are also possible.

The resonator can be used in RF filters of communication devices that use Band-13 frequencies together with GPS frequencies, the Band-8 frequencies together with Band-3 frequencies, the Band-41 frequencies together with 5-GHz Use Wi-Fi frequencies, or similar combinations are used in which harmonics of a frequency band used collide with other frequency band used. The said bands and frequencies refer to standards which are valid on the date of filing of the present application.

Central aspects of the electroacoustic resonator and details of preferred embodiments are shown in the schematic figures.

• 1 eine schematische Anordnung von Interdigitalstrukturen eines elektroakustischen Resonators.
• 2 eine mögliche Umsetzung mit einer Kaskade 4-ten Grades in jedem Satz.
• 3 eine Implementierung, in der in jedem Satz zwei Interdigitalstrukturen in Reihe kaskadiert sind.
• 4 eine Ausführungsform mit vier Interdigitalstrukturen, die in jedem Satz in Reihe elektrisch kaskadiert sind.
• 5 eine Implementierung, in der Zwischensammelschienen der zwei Sätze galvanisch getrennt sind.
• 6 eine mögliche Konstruktion eines Bandpassfilters in einer leiterartigen Konfiguration.
• 7 eine mögliche Konstruktion eines Duplexers, der zwei elektroakustische Filter umfasst.
• 8 Leistungskompressionsmessungen.
• 9 simulierte Werte für Störungen von zweiten Harmonischen.
• 10 simulierte Werte für Störungen von dritten Harmonischen.
• 11 Extrapolationen eines Lebensdauermodells einer ersten Ausführungsform eines elektroakustischen Resonators.
• 12 frequenzabhängige Eigenerwärmungsleistungen für verschiedene TCF-Ausgleichschichten einer ersten Ausführungsform.
• 13 extrapolierte Lebensdauerwerte für eine zweite Ausführungsform.
• 14 frequenzabhängige Eigenerwärmungsleistungen für eine zweite Ausführungsform.

Show it:

• 1 a schematic arrangement of interdigital structures of an electroacoustic resonator.
• 2 a possible implementation with a cascade of 4th degree in each sentence.
• 3 an implementation in which two interdigital structures are cascaded in series in each set.
• 4 an embodiment with four interdigital structures that are electrically cascaded in series in each set.
• 5 an implementation in which intermediate busbars of the two sets are galvanically isolated.
• 6 a possible construction of a bandpass filter in a ladder-like configuration.
• 7 a possible construction of a duplexer comprising two electro-acoustic filters.
• 8th Power compression measurements.
• 9 simulated values for second harmonic distortion.
• 10 simulated values for third harmonic distortion.
• 11 Extrapolations of a lifetime model of a first embodiment of an electroacoustic resonator.
• 12 frequency-dependent self-heating powers for different TCF compensation layers of a first embodiment.
• 13 extrapolated lifetime values for a second embodiment.
• 14 frequency-dependent self-heating powers for a second embodiment.

1 shows the relationships of different interdigital structures of electroacoustic resonators EAR in relation to each other. Every interdigital structure IDS belongs either to a first sentence S1 or to a second sentence S2 of interdigital structures of the electroacoustic resonator. Interdigital structures can be cascaded in series or in parallel. Accordingly, interdigital structures IDS indicated by two numbers. The first number denotes the "line". The second number denotes the "column". Accordingly, each sentence points S1 . S2 N columns and M rows of interdigital structures.

Row connections within the same row and a parallel connection within the same column are possible. It is preferred that at least one series compound in S1 and S2 is present to improve the constancy of performance, and that a parallel connection between S1 and S2 is present to pick up harmonics.

For every interdigital structure IDS of the first sentence S1 There is a corresponding interdigital structure with the same indexing in the second set, which is similar to the corresponding interdigital structure of the first set with respect to their cascading.

For clarity, electrical connections in the illustration of 1 omitted.

2 FIG. 12 shows an embodiment in which the first set comprises a four-fold row cascade of four interdigital structures IDS1,1 to IDS1,4. The transducers of the interdigital structures are between electroacoustic reflectors REF arranged. A first central busbar electrically connects the first interdigital structures IDS1,1. Two second busbars BB connect the corresponding last interdigital structures IDS1,4.

The acoustic reflectors REF , the busbars BB and the electrode fingers are on a piezoelectric substrate PS arranged and form a SAW resonator (SAW = surface acoustic wave) or a GBAW resonator (GBAW = guided bulk acoustic wave).

A specific embodiment may be thin film SAW devices and / or HQTCF SAW devices.

3 shows a possible arrangement of two interdigital structures IDS1,1 . IDS1,2 per set of interdigital structures. The two interdigital structures are arranged in a line within the same acoustic track. Acoustic energy is limited by acoustic reflectors. Optionally, another acoustic reflector is arranged between the two interdigital structures of the same set.

4 shows the possibility of arranging four series cascaded interdigital structures in a single acoustic track between two acoustic reflectors. A central bus bar at the input terminal, a central bus bar at the output terminal and an intermediate bus bar are used by both sets.

On the other hand shows 5 an embodiment in which the sub-busbar is divided into two separate busbars, so that a galvanic isolation is achieved.

6 shows the possibility of electrically connecting electroacoustic resonators EAR in a ladder-like configuration to form an electro-acoustic filter EAF, such as a band-pass filter or a band-stop filter. If the filter EAF is a receive filter, then RF signals can be sent to the port P2 received and sent to an external circuit environment through connection P1 are provided. However, if the filter EAF is a transmission filter, then the transmission signals at the terminal P1 from an external circuit environment and to an antenna or antenna system at the port P2 provided.

Accordingly shows 7 the possibility of combining two electroacoustic filters EAF1 . EAF2 to a duplexer YOU to build. EAF1 implements a receive filter. EAF2 implements a transmission filter, a matching circuit MN is disposed between the two electroacoustic filters to provide electrical decoupling.

8th shows results of power compression measurements that demonstrate the performance of a configuration according to 2 (Curves 1) with a performance of a configuration according to 5 (Curves 2) compare. The output power is mainly linear with the input power, covering a large input power range.

9 shows second harmonic measurements for the two embodiments for a variety of different printed circuit board materials on which the filter component is disposed. Again, curves relate 1 on the in 2 shown embodiment. curves 2 refer to the embodiment of 5 , The input power is 31 dBm.

10 shows the results of third harmonic measurements for the two embodiments ( 2 . 5 ) for an input power of 31 dBm.

11 Figure 12 shows extrapolations of a lifetime model based on a test at 125 ° C and 55 ° C for a bandpass filter employing a resonator as in 2 shown, has.

12 shows frequency-dependent self-heating densities for a band-pass filter having a structure as in FIG 2 and various TCF layers providing different temperature coefficients of frequencies.

13 and 14 show the corresponding value for an embodiment based on a resonator configuration as in FIG 5 shown, based.

Thus, resonator configurations are provided that allow for improvements in performance and linearity. The electroacoustic resonator is not limited by the details and the illustrated embodiments. Electroacoustic resonators comprising other interdigital structures, series connections and parallel connections of circuit elements are also included.

LIST OF REFERENCE NUMBERS

AT:

Antenna or antenna structure

BB:

bus

C:

Correspondence between interdigital structures of different sentences

YOU:

duplexer

EAF1, EAF2:

First, second electro-acoustic filter of a duplexer

EAR:

Electro-acoustic resonator

IDS:

Interdigital structures

MN:

Matching network

P1, P2:

First, second connection of an electro-acoustic filter

PS:

Piezoelectric substrate

REF:

Acoustic reflector

S1, S2:

First, second set of interdigital structures

SL:

Symmetry line indicating two aspects of symmetry

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• "Generation mechanisms of second-order nonlinearity in surface acoustic wave devices", K. Hashimoto, R. Kodaira, T. Omori, IEEE International Ultrasonic Symposium Proceedings 2014 [0003]
• "Application of a rigorous non-linear P-matrix method to the simulation of third order intermodulation in test devices in duplexers", M. Mayer, W. Ruile, J. Johnson, J. Kiwitt, R. San Jose, E. Schmidhammer , I. Bleyl, K. Wagner, E. Mayer, IEEE International Ultrasonic Symposium Proceedings 2014 [0003]

Claims (11)

An electroacoustic resonator with increased power stability and improved linearity, comprising: a first set of I ≥ 2 interdigital structures, a second set of I ≥ 2 interdigital structures, wherein the first set of interdigital structures is electrically connected in parallel with the second set of interdigital structures, in the first set of interdigital structures at least two interdigital structures are connected in series, - Each interdigital structure of the first set of an interdigital structure of the second set corresponds and the connection scheme of the first and the second set is symmetrical. An electroacoustic resonator according to the preceding claim, comprising I = 4 interdigital structures in the first set. Electroacoustic resonator after Claim 1 , wherein the interdigital structures are connected in series in the first set. Electroacoustic resonator according to one of the preceding claims, wherein at least two corresponding interdigital structures have an antiparallel construction. Electroacoustic resonator according to one of the preceding claims, wherein at least two groups of corresponding interdigital structures are connected in parallel and have an antiparallel construction. An electroacoustic resonator according to any one of the preceding claims, wherein at least two corresponding interdigital structures have constructions different from an antiparallel construction. An electroacoustic resonator according to any one of the preceding claims, wherein at least two corresponding interdigital structures are connected in series and have constructions different from an antiparallel construction. Electroacoustic resonator according to one of the preceding claims, wherein at least two interdigital structures are arranged within the same acoustic track. Electroacoustic resonator according to one of the preceding claims, wherein at least two interdigital structures are arranged between electroacoustic reflectors. An RF filter comprising one or more electroacoustic resonators according to any one of the preceding claims. A multiplexer comprising one or more RF filters according to the preceding claim.

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