DE102019113282A1 - Acoustic delay component - Google Patents

Abstract

An acoustic delay component that provides a wide bandwidth and a high center frequency along with a low insertion loss is provided. The delay component comprises two or more functional cells which are arranged in a transducer of a transducer structure in an acoustic track. The functional cells are selected from excitation cells, pure excitation cells, reflection cells, pure reflection cells, directivity cells, SPUDT cells and non-reflection cells.

Description

The present invention relates to a delay component, e.g. B. a delay component that can be used in an RF signal path and that operates on acoustic waves.

A delay component (a delay device) is a circuit component that transmits a signal, e.g. B. an RF signal, can delay. It is possible for an RF signal to be received from an external circuit environment through the delay component. After a certain amount of time, the delay time, the signal is passed on to an external circuit environment. The signal can be continuous or discrete in terms of time and amplitude. In particular, the signal can be an electrical signal and the delay provided by the delay component can be used to synchronize or desynchronize related signals. In particular, the delay component can be used in an envelope tracking system (envelope tracking system) in order to synchronize the RF signal with a second signal which carries envelope information of the RF signal.

It is possible to use a delay line comprising a signal conductor of a certain length to delay an RF signal. However, if the delay time should be long, then the corresponding signal conductor becomes very long, which is not compatible with the trend towards ongoing miniaturization.

Further, it is desirable to have a delay component that has a constant group delay time; H. a flat shape of the group delay curve versus frequency. Further, a delay component is desired that can provide a delay time in the range of 10 nanoseconds. In addition, the insertion loss should be as low as possible, e.g. B. 4 dB or less. The delay component should operate at a center frequency of about 3600 MHz and provide a flat delay in a frequency band with a bandwidth of 400 MHz, which corresponds to the relatively large bandwidth of 11.1%. Furthermore, the delay component should be producible using conventional photolithographic processes. In particular, the delay component should be compatible with an envelope tracking system of mobile communication circuitry.

For this purpose an acoustic delay component is provided according to the independent claim. Dependent claims provide preferred embodiments and a corresponding RF module with such a delay component.

The acoustic delay component includes an acoustic track. The acoustic track comprises a piezoelectric material and a transducer structure which is arranged on the piezoelectric material. The transducer structure includes a transducer with two bus bars and electrode fingers. Each of the electrode fingers is connected to one of the two bus bars. The converter further includes a plurality of two or more functional cells. The functional cells of the transducers are selected from excitation cells, pure excitation cells, reflection cells, pure reflection cells, directivity cells, SPUDT cells (SPUDT: Single Phase Unidirectional Transducer) and non-reflection cells. Furthermore, an acoustic wave mode with a center frequency f and a wavelength A can propagate in the transducer structure.

Such an acoustic delay component may include an input port and an output port and provide a delay time Δt with respect to an RF signal entering the delay component.

A functional cell in the transducer comprises a certain amount of electrode fingers adjacent to one another and arranged in the acoustic track.

An excitation cell is a group of electrode fingers which - when supplied with an RF signal - can convert between electrical and acoustic RF signals and can excite the acoustic wave mode of the delay component. Furthermore, a pure excitation cell can excite the acoustic wave mode, but does not provide any reflection or directivity for the acoustic wave mode. A reflection cell comprises one or more electrode fingers which are arranged next to one another in the cell. Furthermore, the reflection cell has a certain degree of reflection with respect to acoustic waves. Accordingly, a reflection cell can at least partially reflect an acoustic wave. A pure reflection cell provides a reflection coefficient with respect to acoustic waves and at least partially reflects acoustic waves. Furthermore, the pure reflection cell makes no further contribution to the excitation of acoustic waves. Accordingly, the pure reflection cell has no directivity with regard to an excitation. A directivity cell can at least partially reflect acoustic waves. Furthermore, a directivity cell can contribute to the excitation of acoustic waves. However, every acoustic contribution (reflection or Suggestion) a directivity. This means that the extent of the acoustic effect depends on the direction. A SPUDT cell is a cell that provides directivity with respect to the excitation of acoustic waves. A non-reflection cell is a cell that has a significantly reduced reflection coefficient with respect to waves reaching the cell from one or both sides.

Such an acoustic delay component can provide a delay time of about 5 to 10 ns. Furthermore, such an acoustic delay component can provide a relatively constant group delay time and a flat shape of the frequency dependent group delay time curve. Furthermore, such a delay component can provide an insertion loss below 4 dB and provide a delay time for RF signals in a frequency band with a bandwidth of 400 MHz or more and a center frequency of 3600 MHz. Furthermore, such an acoustic delay component, in particular the transducer structure thereof, can be generated using conventional photolithographic processes. Accordingly, no special requirements related to manufacturing processes are added. Furthermore, such a delay component is compatible with envelope tracking systems of e.g. B. wireless communication circuitry, e.g. B. in a front end circuit of a mobile communication device.

The number of functional cells in the converter can be one, two, three, four, five, six, seven, eight, nine, ten, or more.

Furthermore, the delay component can comprise one or more additional converters. The one or more additional transducers can also comprise the above-mentioned functional cells. Different converters can have the same or similar construction. However, different converters can have different designs that are optimized with respect to different parameters such as bandwidth, insertion loss, and others.

Accordingly, it is possible for the converter structure to include one or more additional converters.

The one or more additional transducers can be placed in the same acoustic track. However, it is possible that the acoustic delay component comprises one or more additional acoustic tracks and the additional transducers are arranged or distributed over the acoustic track and the additional acoustic tracks.

It is possible for each cell to have a length 1 that is an integer multiple of λ: 1 = n λ, where n is an integer greater than or equal to 1. It is possible that n = 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

It is possible for each transducer to have an interdigitated electrode structure. The finger-like interlaced electrode structure has electrode fingers that are interlaced like fingers. Finger-like interlaced electrode fingers are known from conventional electrocaustic transducers, finger-like interlaced electrode fingers producing finger-like interlaced comb-like structures together with two busbars. Typically, each electrode finger is electrically connected to one of the two bus bars.

If two adjacent electrode fingers are electrically connected to opposite busbars, then an excitation center is obtained between the two electrode fingers if the excitation coincides with the corresponding phase of the acoustic wave. A larger contribution to the excitation of an acoustic wave is obtained when the excitation center is located at a position where the acoustic wave has a large amplitude. A smaller contribution or no contribution to the excitation is obtained when the position of the excitation center essentially corresponds to a wave node with no wave amplitude or with no substantial wave amplitude.

A local split finger configuration in the acoustic track is obtained when two adjacent electrode fingers are electrically connected to the same busbar. Then the same electrical potential is applied to two adjacent electrode fingers. If the two centers of the two electrodes - with reference to the direction of propagation of the acoustic wave along the longitudinal direction orthogonal to the extension of the electrode fingers - have a distance of approximately A / 4, then the reflection contributions from one of the two electrode fingers raise the reflection contribution from the respective other electrode fingers and the two fingers do not contribute to the reflection of acoustic waves. Providing such return loss split finger configurations in a cell can be used to reduce or eliminate the reflection coefficient of a cell, e.g. B. to obtain a reflection cell or a pure reflection cell.

Directivity cells - related to the excitation and emission of acoustic waves - and / or SPUDT cells can be obtained by adding an excitation center and a reflection center are provided within a cell, which have a spacing of approximately λ / 8.

It is possible that the transducer structure includes transducers that are interlaced in the manner of fingers.

That is, several converters are electrically connected to an electrical potential by one of their busbars. Second several converters are electrically connected to one of their busbars with a second, e.g. B. opposite electrical potential connected. A finger-like interlaced IDT structure (IIDT structure) is then obtained if transducers of both groups are arranged iteratively and alternately in the acoustic track. Accordingly, the arrangement of transducers interlaced in the manner of fingers is similar to the arrangement of electrode fingers in a transducer.

Such a configuration works well when the converters are bidirectional converters. Such a configuration produces a non-resonant electroacoustic structure which is preferred for a flat group delay curve. Furthermore, an insertion loss below 4 dB is possible with such an IIDT structure.

In an acoustic track comprising IIDT assemblies, the transducers located between the two transducers at the distal ends of the acoustic track are excited in a symmetrical manner. Then they can be adapted electrically and acoustically to the ports of the delay component. Such an adaptation, in particular the reduction of the reflection at the acoustic port, is necessary in order to minimize the triple-pass signal.

However, a low insertion loss can also be obtained with unidirectional transducers that have directivity with respect to the emission of acoustic waves. Such unidirectional transducers can have a minimum structure width (e.g. of an electrode finger) of λ / 8.

Accordingly, it is possible for the input transducer and output transducer (both of which are electrically connected to the different potentials) to be arranged alternately in the acoustic track.

It is possible for one or more of the transducers to be fan-shaped transducers.

In the case of fan-shaped transducers, distances are varied along the longitudinal direction via the transverse direction of the transducer. In particular, the finger period is changed along the transverse direction. The electrode fingers produce a fan structure accordingly. Their spacings vary along the transverse direction, while the busbars remain essentially parallel.

The concept of using fan-shaped transducers corresponds electrically to a parallel connection of several frequency-shifted acoustic partial tracks within a transducer, which simplifies obtaining a relatively large bandwidth.

It is possible that a cell, e.g. B. a SPUDT cell, a length 1: 1> λ.

Such a SPUDT cell is different from conventional SPUDT cells, the distance between an excitation center and a reflection center being equal to λ / 8.

The use of a SPUDT cell has the advantage that it is reflection-free at the inner acoustic port if the regenerated source and load signal is compensated for by the short-circuit reflection. In the time domain, which corresponds to the finger geometry, this means that the short-circuit reflection should correspond to the self-folding of the excitation.

It is possible that a cell has an excitation center and a reflection center and the distance d between the excitation center and the reflection center is greater than A: d> λ.

It is also possible that the number of electrode fingers of one or more cells is an odd number, i.e. H. the number is 2n + 1, where n is an integer. In particular, n is the cell length in units of λ: 1 = n λ.

It is possible for the delay component to include a split finger arrangement in a transducer. Such a split finger arrangement in a transducer can be part of a non-reflection cell.

In particular, it is possible for the number of electrode fingers of one or more cells to be selected from 4, 5, 6 and 7.

Depending on the busbar to which the electrode fingers are connected, and depending on the exact finger width and spacing, such cells can be used to produce reflection cells, excitation cells, directivity cells, non-reflection cells, non-excitation cells, pure excitation cells, pure reflection cells and neutral cells.

It is possible for the delay component to comprise several transducers interlaced in the manner of fingers. Each converter includes a first, one second and third cell. Each cell has a length 1 = 2 A. Each cell has two electrode fingers that are electrically connected to one busbar and three electrode fingers that are electrically connected to the respective other busbar. Then it is possible that the two split finger configurations produced are at longitudinal positions where the acoustic wave mode has a wave node. With such converters, e.g. In an IIDT configuration, delay components can be made with little loss.

In an alternative arrangement, the delay component has a plurality of transducers interlaced in the manner of fingers. Each converter includes a first and a second cell. Each cell has a length 1 = 3 A. Each cell has three electrode fingers connected to one bus bar and four electrode fingers connected to the respective other bus bar.

Such a configuration has a split finger configuration at the center of the transducer where the acoustic wave mode has a wave node. In addition, with such a configuration, a delay component can be provided with little loss.

In another configuration, the delay component includes a ten-cell interdigitated transducer. The ten cells assign them sequence 3 1 3 1 3 1 3 1 2 2 on, where 1 represents an excitation cell (with - at most - a small reflection), 2 represents an excitation cell (with - at most - a small reflection) and 3 represents a pure reflection cell.

The excitation of the cell 1 can be in phase with the excitation of the cell 2 his.

The cell 1 can have a length of 4 times 2/5 A (= 8/5 A) and 4th Have electrode fingers.

The cell 2 can have a length of 5 times 2/5 A (= 2 A) and have 5 electrode fingers.

The cell 3 can have a length of 5 + 2/5 λ (= 12/5 λ) and 5 Have electrode fingers.

Another arrangement of a delay cell includes a ten cell interdigital transducer with the sequence 4 ' 1' 3 ' 1' 3 ' 1' 3 ' 1' 2 ' 2 ' , in which 1' represents an essential excitation cell (with - at most - a low reflection). 2 ' represents an excitation cell. 3 ' represents a reflection cell (with - at most - a small excitation) and 4 ' represents a reflection cell.

The cell 1' can have a length of 4 times 2/5 λ (= 8/5 λ) and have 4 electrode fingers.

The cell 2 ' can have a length of 5 times 2/5 λ (= 2 A) and have 5 electrode fingers.

The cell 3 ' can have a length of 5 + 2/5 λ (= 12/5 λ) and have 5 electrode fingers.

It is possible for the acoustic track to have a metallization ratio η, where η is 0.4 or greater and 0.6 or less.

The metallization ratio η of a transducer or several transducers in an acoustic track is defined as the sum of the finger width of the individual electrode fingers divided by the length of the transducer in the longitudinal direction or divided by the length of the acoustic track in the longitudinal direction.

The provision of the delay components defined above with the transducer structures is such that these metallization ratios can be achieved with essentially conventional manufacturing steps, so that the generation of the delay component is possible with conventional methods for manufacturing surface acoustic wave components.

It is possible that each electrode finger has a width w with w 0.15 µm or w 0.22 µm.

It is also possible that the minimum distance between adjacent fingers is D, with D ≥ 0.15 µm or D ≥ 0.22 µm.

Such structural widths can be obtained using conventional manufacturing steps for setting up acoustic components.

It is possible for the delay component to provide a signal delay Δt with 5 ns Δt 10 ns. In particular, it is possible that Δt = 7 ns applies.

It is possible that the converter structure has a length of l_TD with 20 λ l_TD ≤ 30 λ. In particular, it is possible for the length of the converter structure to be essentially equal to 25λ.

If fan-shaped transducers are used in the transducer structure, then the functional cell 3 ' have the relative finger widths 80.4%, 100%, 92.7%, 78.8%, 62.6%. The functional cell 1' can have the relative finger widths 72.1%, 62.0%, 79.9%, 65.4%. The functional cell 2 ' the relative finger widths can be 84.9%, 60.9%, 68.7 %, 89.4%, 60.3%. The values of the finger widths are relative to those of the widest finger, which is 100%.

A fan-shaped transducer has - with respect to the transversal position - a high-frequency side with smaller grid dimensions and a low-frequency side with higher grid dimensions. With respect to the longitudinal direction x, the transducer has a longer extension on the low-frequency side and a shorter extension on the high-frequency side.

It has been found that further improved delay components can be obtained if finger widths and finger spacings are individually optimized at different locations, in particular at different lateral positions y, within the range of a fan-shaped transducer.

Accordingly, the functional cell can 3 ' or another reflection and excitation cell the relative finger widths 67.2%, 100%, 67.2%, 67.2%, 57.4% on the low frequency side and 72.8%, 91.3%, 90.2% , 86.7%, 66.2% on the high frequency side.

The functional cell 1' or another excitation cell can have the relative finger widths 56.4%, 60.5%, 80%, 53.8%, on the low frequency side and 72.8%, 73.8%, 69.7%, 72.8% have the high frequency side.

The functional cell 2 ' or another reflection cell can have the relative finger widths 77.9%, 55.9%, 63.1%, 82.1%, 55.4%, on the low frequency side and 52.8%, 76.9%, 75.9 %, 73.8%, 75.4% on the high frequency side.

The values of the finger widths are relative to those of the widest finger, which is 100%.

It is possible for one or more fan-shaped transducers to be split transducers.

A split transducer is obtained by dividing a fan-shaped transducer into two or more parts of the split transducer. The divided parts are electrically connected in parallel. Accordingly, a split transducer has two or more parts that are acoustically decoupled but electrically connected in parallel.

The fan angle α is the angle between the extension direction of the first (or last) electrode finger of the fan-shaped transducer and the transverse direction, i.e. H. the direction orthogonal to the direction of propagation of the acoustic waves.

Larger fan angles α lead to 2-dimensional losses that are caused by diffraction effects due to the inclined electrode finger edges.

It is possible to decrease the fan angle by increasing the aperture (i.e. the extent along the transverse direction y) of the corresponding fan-shaped transducer in order to maintain a desired bandwidth.

However, increased apertures lead to longer electrode fingers. Longer electrode fingers lead to increased ohmic losses.

The provision of split transducers comprising electrically connected parts makes it possible to have a small fan angle α along with short electrode fingers while maintaining a large bandwidth. A portion of the split transducer provides a first bandwidth compatible with a given fan angle α and compatible with a given maximum finger length. The one or more parts of the split transducer provide respective further bandwidths that are compatible with a given fan angle α and are compatible with a given maximum finger length. The parallel connection ensures that the bandwidth of the entire split converter is essentially equal to the sum of the individual bandwidths.

It is possible that the number of divided transducers is selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

It is possible that the number of parts of a split transducer is selected from 2, 3, 4, 5, 6, 7, 8, 9, 10.

The number of parts of different split transducers can be the same or different.

It is preferred that there are no gaps between (partial) bandwidths of parts of the split transducers. However, bandwidths of parts of the split transducers may overlap; that is, there may be frequencies belonging to more than one such (partial) bandwidth.

The delay component can be part of an RF module, e.g. B. a power amplifier module. In the power amplifier module, the delay component can be used to synchronize an RF signal with an information signal that includes envelope information of the RF signal.

Central aspects of the delay component and details of preferred embodiments are shown by the accompanying figures.

• 1 zeigt eine grundlegende Konstruktion einer akustischen Verzögerungskomponente ADC, die mehrere funktionale Zellen FC umfasst;
• 2 zeigt eine Zelle mit einer reduzierten (oder unterdrückten) Reflexion, um Resonanzen in der akustischen Spur zu reduzieren oder zu vermeiden;
• 3 zeigt die Verwendung von Dummy-Fingern DF in der akustischen Spur;
• 4 zeigt eine funktionale Zelle FC mit sieben Fingern, die so angeordnet sind, dass die Resonanzen innerhalb der akustischen Spur reduziert oder vermieden werden;
• 5 zeigt einen Wandler TD mit zwei Aufgeteilter-Finger-Anordnungen;
• 6 zeigt einen Wandler TD mit einer Aufgeteilter-Finger-Anordnung;
• 7 zeigt eine IIDT-Konfiguration basierend auf dem in 5 gezeigten Wandler;
• 8 zeigt eine IIDT-Konfiguration basierend auf dem in 6 gezeigten Wandler;
• 9 zeigt einen Wandler in einer SPUDT-Konfiguration;
• 10 zeigt einen alternativen Wandler in einer SPUDT-Konfiguration;
• 11 zeigt elektrische Parameter einer IIDT-Konfiguration basierend auf dem in 5 und 6 gezeigten Wandler;
• 12 zeigt elektrische Parameter einer Verzögerungskomponente basierend auf den in 9 und 10 gezeigten Wandlern;
• 13 zeigt zusätzliche elektrische Parameter einer Verzögerungskomponente basierend auf den in 9 und 10 gezeigten Wandlern;
• 14 zeigt eine mögliche Anwendung einer akustischen Verzögerungskomponente ADC in einem HF-Modul RFM;
• 15 zeigt einen fächerförmigen Wandler; und
• 16 zeigt einen Aufgeteilter-Finger-Wandler.
• 17 zeigt die Niederfrequenzseite (LF: Low Frequency) und die Hochfrequenz(HF: High Frequency)-Seite eines Segments eines fächerförmigen Wandlers mit lokal optimierten Fingerbreiten und Fingerabständen.
• 18 zeigt einen fächerförmigen Wandler mit lokal optimierten Fingerbreiten und Fingerabständen.
• 19 zeigt die Transferfunktionen S12 von fächerförmigen Wandlern mit den Zellensequenzen des in 9 und in 10 gezeigten Wandlers.
• 20 zeigt die Rückflussdämpfung der fächerförmigen Wandler mit den Zellensequenzen des in 9 und in 10 gezeigten Wandlers.
• 21 zeigt die Transferfunktionen S12 der fächerförmigen Wandler mit den Zellensequenzen des in 9 und in 10 gezeigten Wandlers in einer Zoom-Ansicht und entsprechende Gruppenverzögerungszeiten um 7 ns herum.
• 22 zeigt die Impulsantworten der fächerförmigen Wandler mit den Zellensequenzen des in 9 und in 10 gezeigten Wandlers.
• 23 zeigt das Konzept eines aufgeteilten Wandlers.
• 24 zeigt den Effekt des Teilens eines Wandlers.

In the figures:

• 1 shows a basic construction of an acoustic delay component ADC who have favourited multiple functional cells FC includes;
• 2 shows a cell with a reduced (or suppressed) reflection to reduce or avoid resonances in the acoustic track;
• 3 shows the use of dummy fingers DF in the acoustic track;
• 4th shows a functional cell FC with seven fingers arranged in such a way that the resonances within the acoustic track are reduced or avoided;
• 5 shows a converter TD with two split finger arrangements;
• 6th shows a converter TD with a split finger arrangement;
• 7th shows an IIDT configuration based on the in 5 shown converter;
• 8th shows an IIDT configuration based on the in 6th shown converter;
• 9 Figure 3 shows a transducer in a SPUDT configuration;
• 10 Figure 11 shows an alternative transducer in a SPUDT configuration;
• 11 shows electrical parameters of an IIDT configuration based on the in 5 and 6th shown converter;
• 12 FIG. 10 shows electrical parameters of a delay component based on the in FIG 9 and 10 shown converters;
• 13 FIG. 10 shows additional electrical parameters of a delay component based on the in FIG 9 and 10 shown converters;
• 14th shows a possible application of an acoustic delay component ADC in an RF module RFM ;
• 15th Figure 3 shows a fan-shaped transducer; and
• 16 Figure 3 shows a split finger transducer.
• 17th shows the low frequency side (LF: Low Frequency) and the high frequency (HF: High Frequency) side of a segment of a fan-shaped transducer with locally optimized finger widths and finger spacings.
• 18th shows a fan-shaped transducer with locally optimized finger widths and finger spacings.
• 19th shows the transfer functions S12 of fan-shaped transducers with the cell sequences of the in 9 and in 10 shown converter.
• 20th shows the return loss of the fan-shaped transducers with the cell sequences of the in 9 and in 10 shown converter.
• 21st shows the transfer functions S12 the fan-shaped transducer with the cell sequences of the in 9 and in 10 shown converter in a zoom view and corresponding group delay times around 7 ns.
• 22nd shows the impulse responses of the fan-shaped transducers with the cell sequences of the in 9 and in 10 shown converter.
• 23 shows the concept of a split transducer.
• 24 shows the effect of sharing a transducer.

1 shows a basic overview of an acoustic delay component ADC . The acoustic delay component ADC (Acoustic Delay Component) has a piezoelectric material PM and an acoustic track AT that is a segment of the surface of the piezoelectric material PM includes, on. There is a transducer structure in the acoustic track TS arranged. The converter structure TS comprises several functional cells FC . The functional cells FC are arranged in a row configuration along the longitudinal direction x, which is the direction of propagation of the main acoustic mode in the acoustic track AT Are defined. The transverse direction, which defines the direction of extension of electrode fingers, is denoted as y.

The functional cells FC establish transducers or transducer segments comprising electrode fingers and busbars or segments of busbars. The functional cells FC or two or more functional cells FC can be arranged in a single transducer. However, it is possible for any functional cell FC sets up a single converter. Gaps can be created between the functional cells along the longitudinal direction x FC to be ordered. However, it is also possible for functional cells FC right next to each other within the acoustic track AT are arranged.

The functional cells FC are for adding special functionality to the transducer structure TS in the acoustic track AT provided. Every functional cell FC can a Provide excitation functionality, reflection functionality, directivity functionality, etc. The directivity functionality can relate to reflection and / or suggestion. It is possible that one or more functional cells combine different functionalities. Accordingly, it is possible for a functional cell to add a reflection functionality together with an excitation functionality to the acoustic track. In addition, it is possible that a functional cell is free from an excitation functionality or free from a reflection functionality or free from a directivity functionality. Furthermore, it is possible that a functional cell only provides a single functionality, which is selected from excitation, reflection, directivity, while the functional cell does not provide the respective two other functionalities.

The provision of the special functional cells at special positions within a transducer within the acoustic track provides the possibility of obtaining an acoustic delay component which corresponds to the special requirements, in particular the requirement of the high bandwidth, the low insertion loss and the high center frequency while using conventional processes used in setting up surface acoustic wave components.

2 illustrates a functional cell FC , which has an odd number of electrode fingers per integral multiple of the acoustic wavelength λ. In particular shows 2 a functional cell that has five electrode fingers per 2λ lengths. The undulating curve illustrates the phase position of the main acoustic mode. A maximum amplitude of the waveform corresponds to a position where the amplitude reaches a maximum value. At a position where the waveform intersects the center line parallel to the longitudinal direction x in the center of the acoustic track, node corresponds to the main acoustic mode. The length of the arrows indicates the strength of the contribution of excitation centers to the excitation of the acoustic mode. Accordingly, different stimulus centers provide different stimulus contributions. The use of an uneven number of electrode fingers per integral multiple of the acoustic wavelength λ reduces a reflection contribution of the functional cell FC to reduce or avoid resonances in the acoustic track, to provide a flat frequency-dependent group delay curve over a wide frequency range.

3 illustrates the use of dummy fingers DF electrically connected to a bus bar and a distal end of an electrode finger EF opposite. The use of dummy fingers DF improves the setting up of a desired acoustic main mode and reduces unwanted interference modes.

4th illustrates a functional cell FC with seven electrode fingers per three λ-lengths. Compared to the in 2 The structure shown has the functional cell FC out 4th a similar excitation strength per length of the corresponding transducer measured in multiples of the acoustic wavelength A, because a reduced number of cells is required for a given transducer length, while the positions of excitation centers vary more with maximum values of the amplitude with increasing length of the functional cell.

5 shows a converter TD , the three in 3 includes functional cells shown. At interfaces between adjacent functional cells FC For example, a split-finger configuration is arranged without an excitation center. Accordingly, the converter includes TD two split-finger configurations because three functional cells arranged in series in the acoustic track comprise two corresponding interfaces, indicated by the dashed lines extending along the transverse direction y.

In contrast shows 6th a converter TD , the two of the in 4th comprises functional cells shown, wherein a single split-finger configuration in the - with respect to the longitudinal direction x - center position of the transducer TD is arranged.

In Figure 5 or 6th The transducers shown can be used in an IIDT configuration to establish a delay component with a constant group delay time over a wide frequency range along with low insertion loss.

Illustrated accordingly 7th such an Inter-IDT configuration IIDT , the four of the in 5 includes converter shown. Every converter TD is an input transducer or an output transducer and the input transducer and output transducer are alternately distributed over the longitudinal direction of the acoustic track. Each of the converters TD comprises three functional cells FC1 , FC2 , FC3 , being the three functional cells FC1 , FC2 and FC3 of the same type as through 2 are shown.

The acoustic length from one input transducer to the neighboring output transducer is approximately 25 λ. The total length of the acoustic track essentially determines the group delay time of the delay component.

Equally shows 8th an IIDT structure based on the in 6th shown converters TD so that each converter TD two functional cells FC1 , FC2 that are of the same type, so each transducer TD has a split-finger configuration located at the center thereof.

Again, the total length of the transducer structure is approximately 25 λ so that a group delay time of 7 ns is obtained.

9 illustrates a transducer structure that incorporates a SPUDT includes. The SPUDT comprises ten functional cells, which are arranged one after the other in the acoustic track. The SPUDT structure has the functional cell sequence 3 1 3 1 3 1 3 1 2 2 on. 1 represents an excitation cell (with - at most - a small reflection), 2 represents an excitation cell (with - at most - a small reflection) -reflection cell and 3 represents a pure non-reflection cell.
To this end, includes the functional cell 1 a four-electrode finger configuration. Two electrode fingers are electrically connected to one of the two bus bars. The other two electrode fingers are electrically connected to the respective other bus bar. The functional cell 2 essentially corresponds to the in 2 functional cell shown and has three electrode fingers electrically connected to the lower bus bar and two electrode fingers electrically connected to the upper bus bar. The functional cell 3 includes five electrode fingers. Each of the five electrode fingers is electrically connected to the lower busbar.

An alternative arrangement is in 10 shown. 10 includes one SPUDT with the functional cell sequence 4 ' 1' 3 ' 1' 3 ' 1' 3 ' 1' 2 ' 2 ' . 1' represents an essentially excitation cell (with - at most - a small reflection). 2 ' represents an excitation reflection cell. 3 ' represents a reflection and excitation cell (with - at most - a small excitation) and 4 ' represents a reflection cell.

To this end, the functional cell corresponds 2 ' the in 2 and has three electrode fingers electrically connected to the lower bus bar and two electrode fingers electrically connected to the bus bar. The functional cell 1' includes two electrode fingers electrically connected to the lower bus bar and two electrode fingers electrically connected to the upper bus bar. The functional cell 3 ' includes four electrode fingers electrically connected to the lower bus bar and one electrode finger electrically connected to the upper bus bar. The functional cell 4 ' corresponds to the functional cell 3 ' except that all five electrode fingers are electrically connected to the lower bus bar.

11 shows a comparison of P-matrix elements and Y-matrix elements of transducers of length 12 λ, which is the in 2 and 4th functional cells shown.
In particular, the curve shows Y52 the real part of the matrix element y11 of a converter, which contains the in 2 functional cells shown with five electrode fingers per length 2λ comprises. The curve Y73 shows the real part of the matrix element y11 of a transducer which has the length 12 A and two of the in 4th includes cells shown with seven electrode fingers per length 3λ.

The curve shows accordingly P52 the matrix element P11 of a transducer, the six of the functional cells FC out 2 which are arranged in series in the acoustic track. The curve P73 shows the matrix element P11 of a transducer, the four of the functional cells FC out 4th which are arranged in series one after the other, so that a transducer with the length 12λ is obtained. The structures are essentially reflection-free within the frequency range between 3400 and 3800 MHz, as indicated by the dome-shaped curves Y52 and Y73 is shown.

12 shows the real parts of the converter admittances (real part of Y11) and the short-circuit reflections ( P11 ) for the in 9 and 10 shown converter. In particular, the curve shows Y1 the real part of the converter admittance of the converter 9 . The curve Y2 shows the real part of the converter admittance of the in 10 shown converter. The curve P1 shows the short-circuit reflection ( P11 ) the in 9 converter structure shown. The curve P2 shows the short-circuit reflection of a converter with the in 10 electrode structure shown.

In the 12 The curves shown have a flat shape, especially in the frequency range around the center frequency of 3600 MHz.

13 illustrates a comparison between the electroacoustic conversion for the in 9 and 10 transducer geometries shown. In particular, the curve shows P13_1 the electroacoustic conversion P13 of the in 9 shown converter. The curve P13_2 shows the electroacoustic conversion P13 of the in 10 shown converter. The curve P23_1 shows the electroacoustic conversion P23 of the in 9 shown converter. The curve P23_2 shows the electroacoustic conversion P23 of the in 10 shown converter.

In 12 and 13 it can be seen that the characteristics that the in 10 correspond to a wider range than that in 9 Provide provided geometries. The larger bandwidth is obtained through smaller distances between excitation and reflection. This is because, when the distance between an excitation center and a reflection center is large, a small frequency deviation causes a superposition with an imperfect phase relationship of the acoustic waves emitted in a right direction. However, the use of a fan-shaped transducer can compensate for a bandwidth reduction, so that a wide bandwidth can be obtained with low insertion loss of the delay component.

14th illustrates one possible application of the acoustic delay component ADC in an RF module RFM . The RF module RFM has an input port and an output port. A signal line SL is provided for propagating an RF signal from the input port to the output port. Envelope information of the envelope of the signal that is in the signal line SL propagated can be used to provide an amplifier, e.g. B. in an envelope tracking system. The one due to the acoustic delay component ADC Delay Δt provided can be used to compensate for the RF signal that is in the signal line SL propagated to synchronize with the control signal for the amplifier and with the corresponding work of the amplifier.

15th illustrates the basic concept of a fan-shaped transducer. The grid dimension of the transducer varies across the aperture, ie in the transverse direction y, so that a broadband delay component can be obtained.

16 Figure 3 shows a transducer structure that includes split finger assemblies. For each electrode finger, an adjacent electrode finger is connected to the same busbar and the respective other adjacent electrode finger is electrically connected to the respective other busbar. Accordingly, a transducer structure with a reduced or illuminated reflection coefficient is obtained.

17th shows the low frequency side (LF: Low Frequency) and the high frequency (HF: High Frequency) side of a segment of a fan-shaped transducer with locally optimized finger widths and finger spacings.

18th shows a fan-shaped transducer with locally optimized finger widths and finger spacings.

19th shows the transfer functions S12 of fan-shaped transducers with the cell sequences of the in 10 shown converter. The black curve corresponds to finger geometries obtained by scaling a reference track, whereas the red curve results from cell geometries which are independent for the LF side and the HF side and an interpolation between them is optimized.

20th shows the return loss of the fan-shaped transducers with the cell sequences of the in 9 (Curve 9 ) and in 10 (Curve 10 ) shown converter.

21st shows the transfer functions S12 (left scale) of the fan-shaped transducers with the cell sequences of the in 9 (Curve 9 ) and in 10 (Curve 10 ) shown converter in a zoom view and corresponding group delay times (curves 9 ' [ 9 ] and 10 ' [ 10 ]; right scale) around 7 ns.

22nd shows the impulse responses of the fan-shaped transducers with the cell sequences of the in 9 (Curve 9 ) and in 10 (Curve 10 ) shown converter.

23 shows the idea behind a split transducer to keep the fan angle together with the aperture small while maintaining a desired bandwidth. For this purpose, a converter (shown on the left) is replaced by a split converter (shown on the right). The split transducer includes some, e.g. B. 2, parts electrically connected in parallel as indicated by the signal lines connected to respective bus bars.

In 23 if the upper part of the transducer has the higher pitch, which corresponds to the lower frequencies. The lower transducer part has the lower pitch, which corresponds to the higher frequencies. Accordingly, for the overall frequency band, the upper part provides the lower frequency band and the lower part provides the upper frequency band.

Shows accordingly 24 the transmission admittances of the upper part (curve 1 ), the lower part (curve 2 ) and the parallel connection of both parts (curve 3 ), which provides the full bandwidth.

The delay component is not limited to the technical details described above or shown in the figures. The delay component can also include structures, e.g. B. to improve the shaping of the acoustic wave mode, e.g. For obtaining a piston mode. Furthermore, additional circuit elements, e.g. B. passive circuit elements such as impedance elements such as capacitance elements, inductive elements or resistance elements, can be used to match the impedance of the delay component to the impedance of an external circuit environment, e.g. B. at an input port or an output port of the component.

List of reference symbols

ADC:

acoustic delay component

AT:

acoustic trace

BB:

Busbar

DF:

Dummy fingers

EF:

Electrode finger

FC:

functional cell

FC1, FC2, FC3:

functional cells

IIDT:

interdigital IDT structure

PM:

piezoelectric material

RFM:

RF module

SL:

Signal line

SPUDT:

unidirectional single phase converter

TD:

Converter

TS:

Converter structure

Claims (21)

Acoustic delay component that includes: an acoustic track comprising a piezoelectric material and a transducer structure which is arranged on the piezoelectric material, wherein the transducer structure comprises a transducer with two busbars and electrode fingers, each finger being connected to one of the two busbars, - the converter comprises a plurality of two or more functional cells, - the functional cells are selected from excitation cells, pure excitation cells, reflection cells, pure reflection cells, directivity cells, SPUDT cells and non-reflection cells, - Can propagate an acoustic wave mode with a center frequency f and a wavelength λ in the transducer structure. The delay component of the preceding claim, wherein the transducer structure comprises one or more additional transducers. The delay component of any preceding claim, wherein each cell has a length 1 which is an integral multiple of λ: 1 = n λ. Delay component according to one of the preceding claims, wherein each transducer has a finger-like interlaced electrode structure in which the electrode fingers are interlaced like fingers. Delay component according to one of the preceding claims, wherein the transducer structure comprises transducers interlaced in the manner of fingers. Delay component according to the preceding claim, wherein the input transducer and output transducer are arranged alternately. The delay component of any preceding claim, wherein one or more of the transducers are fan-shaped transducers. A delay component according to any one of the preceding claims, wherein a cell is a SPUDT cell having a length l: 1> λ. A delay component according to any preceding claim, wherein - a cell has an excitation center and a reflection center, and - the distance d between the excitation center and the reflection is greater than A: d> A. A delay component according to any preceding claim, wherein the number of electrode fingers of one or more cells is 2 n + 1, and - n is the cell length in units of λ: l = n λ. Delay component according to one of the preceding claims, wherein the number of electrode fingers of one or more cells is selected from 4, 5, 6, 7. A delay component as claimed in any preceding claim, comprising: - several interdigitated transducers, where - each transducer comprises a first, a second and a third cell, - each cell has a length 1 = 2 A, each cell has 2 electrode fingers which are connected to one busbar and 3 electrode fingers which are connected to the respective other busbar. Delay component according to one of the preceding claims, comprising: - several transducers interdigitated in the manner of fingers, wherein - each transducer comprises a first and a second cell, each cell has a length l = 3λ, each cell has 3 electrode fingers which are connected to one busbar and 4 electrode fingers which are connected to the respective other busbar. A delay component as claimed in any preceding claim, comprising: - an interdigital transducer with 10 cells with the sequence 3 1 3 1 3 1 3 1 2 2, where 1 has an excitation cell with a length of 8/5 A, 2 has an excitation cell with a length of 2 A, 3 has a reflection cell with a length of 12/5 Å. A delay component as claimed in any preceding claim, comprising: - an interdigital transducer with 10 cells with the sequence 4 '1' 3 '1' 3 '1' 3 '1' 2 '2', where 1 'represents an excitation cell, 2 'represents an excitation cell, 3 'represents a reflection and excitation cell, 4 'represents a reflection cell. The delay component according to any one of the preceding claims, wherein the acoustic track has a metallization ratio η with: 0.4 ≤ η ≤ 0.6. The delay component of any preceding claim, wherein each finger has a width w with: - w ≥ 0.15 µm. or - w ≥ 0.22 µm. A delay component according to any preceding claim, wherein the minimum distance between adjacent fingers is D with - D ≥ 0.15 µm or - D ≥ 0.22 µm. Delay component according to one of the preceding claims, which provides a signal delay Δt, with: - 5 ns ≤ Δt ≤ 10 ns or - Δt = 7 ns. Delay component according to one of the preceding claims, wherein the converter structure has a length l_ _TD , with: - 20 λ ≤ l_ _TD ≤ 30 λ or - l_ _TD = 25 X. An RF module comprising a delay component according to any one of the preceding claims.

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