SAW device with suppressed spurious signals
阅读说明：本技术 具有抑制的寄生信号的saw器件 (SAW device with suppressed spurious signals ) 是由 M·迈尔 W·鲁伊莱 A·迈尔 E·迈尔 于 2018-04-19 设计创作，主要内容包括：在SAW器件中包括SAW芯片,SAW芯片承载SAW换能器,SAW换能器被布置在第一信号线内,由于SAW器件的操作频率的高次谐波所致的寄生信号通过补偿部件被电消除,补偿部件包括至少一个第二信号线,至少一个第二信号线具有用于产生抵消信号的部件,抵消信号在符号或相位上不同于寄生信号,或者补偿部件包括分流线,分流线用于将SAW换能器电连接到SAW芯片的背面金属化部。(In a SAW device comprising a SAW chip carrying a SAW transducer, the SAW transducer being arranged in a first signal line, parasitic signals due to higher harmonics of the operating frequency of the SAW device being electrically cancelled by a compensation component, the compensation component comprising at least one second signal line with means for generating a cancellation signal, the cancellation signal differing from the parasitic signals in sign or phase, or the compensation component comprising a shunt line for electrically connecting the SAW transducer to a back metallization of the SAW chip.)
1. A SAW device, comprising:
a SAW Chip (CP) carrying a SAW transducer adapted to operate at an operating frequency and arranged within a first signal line,
-a compensation component connected to the signal line to electrically cancel a nonlinear parasitic signal, wherein the compensation component comprises:
-at least one second signal line (SL2) with means for generating a cancellation signal different in sign or phase from the parasitic signal, or
-shunt lines (SHL) for electrically connecting the SAW transducer to a backside metallization (BSM) of the SAW chip, or
-a shunt resonator (SHR) for electrically connecting the SAW transducer to ground potential at the frequency of the spurious signals to be suppressed.
2. The SAW device of claim 1,
-wherein a backside metallization (BSM) is arranged on the backside of the SAW Chip (CHP) opposite the transducer,
-wherein the transducer comprises a first electrode and a second electrode,
-wherein one of the first and second electrodes is connected to the Back Side Metallization (BSM) via the shunt line (SHL).
3. SAW device according to one of the preceding claims,
-wherein a shunt resonator (SHR) having a resonant frequency at or close to the spurious frequency is coupled between the signal line of the SAW device and ground.
4. The SAW device according to one of the preceding claims, wherein said at least one second signal line (SL 2):
-including a Phase Shifter (PS) or performing a phase shift,
-connected in parallel to the first signal line (SL1),
-providing a useful signal at the operating frequency and a cancelling signal at the spurious frequency, the cancelling signal being equal in magnitude but different in sign or phase from the spurious signal.
5. The SAW device according to one of the preceding claims, wherein a phase shifter (PS1, PS2) is arranged in the first signal line (SL1) and in each of the at least one second Signal Line (SL), wherein the cancellation is achieved by interference of all first and second signal lines.
6. SAW device according to one of the preceding claims,
-wherein the first and second signals (SL1, SL2) are connected in parallel by a circuit, each signal line comprising a series circuit of a first resonator and a second Resonator (RES),
-wherein the first Resonator (RES)A) With respect to the second Resonator (RES)B) Is shifted in its resonance frequency, so as to produce a phase shift of magnitude pi/2 at the frequency of said spurious signal, preferably the second harmonic,
-wherein the order of a first resonator and a second Resonator (RES) is interchanged in said first and second signal lines (SL1, SL2) such that the resulting two said phase shifts of the two said signal lines at the frequency of the spurious signal add up to pi.
7. SAW device according to one of the preceding claims, wherein said Phase Shifter (PS) is embodied as a Resonator (RES) having a resonance frequency at or close to said spurious frequency.
8. The SAW device according to one of the preceding claims, wherein said Phase Shifter (PS) is embodied as a SAW resonator, said SAW resonator being arranged on said SAW chip of said SAW device.
9. The SAW device as claimed in one of the preceding claims, wherein the shunt line is embodied as a VIA (VIA) conducting through the SAW Chip (CHP).
10. The SAW device according to one of the preceding claims, wherein said shunt line (SHL) comprises a segment formed by a housing in which said SAW Chip (CHP) is arranged.
11. SAW device according to one of the preceding claims, embodied as a ladder filter, a DMS filter or a resonator.
Background
In acoustic filters commonly used in modern communication devices, such as mobile phones, non-linearities may arise. These non-linearities generate spurious signals, such as second and higher harmonics and mixing products, which may cause problems in signal processing (like e.g. filtering, selectivity or isolation).
In SAW devices, the second harmonic, referred to as H2, is related to the bulk wave, which produces a signal at twice the passband or resonant frequency of the device in use. This excitation is undesirable in filter applications due to its non-linearity, and therefore many attempts have been made to suppress this excitation. Despite the foregoing, such non-linearities have been used in technical applications such as convolvers.
Some of these attempts have been directed to attenuating the waves at the back of the respective SAW chips or filtering them out by sophisticated filter techniques. However, no solution has been found that can be used to effectively suppress the H2 harmonic in SAW devices of different designs.
Disclosure of Invention
It is therefore an object of the present invention to provide a SAW device which can effectively suppress the second harmonic H2 and associated mixing products.
This and other objects are achieved by a SAW device according to
A SAW device includes a SAW chip, which is a piezoelectric body carrying a SAW transducer on its top surface. The transducer is adapted to operate at an operating frequency of the device, which generally coincides with the resonant frequency of the transducer. The transducer may be part of the filter circuit and disposed within the first signal line. In addition to the feature adapted to operate at the operating frequency, the present invention also provides a compensation component connected to or arranged in the signal line to electrically cancel a nonlinear parasitic signal occurring at a frequency different from the operating frequency.
The compensation member includes:
at least a second signal line having means for generating a cancellation signal different in sign or phase from the parasitic signal, or
Shunt lines for electrically connecting the SAW transducer to the back metallization of the SAW chip, or
A shunt element that implements a short circuit to ground at the frequency at which the spurious signals must be suppressed (e.g., at about twice the resonant frequency for H2 suppression).
In all of the cases mentioned above, the spurious signals are electrically suppressed by: combining and cancelling the parasitic signal with a symmetric signal of a different sign, or short-circuiting the two metallizations carrying the parasitic signal.
A simple solution for the first case is: a second signal line having the same components as the first signal line is provided, and two signal lines having a phase difference of pi from each other at a spurious frequency are combined. Such a phase difference may be achieved by inserting a phase shifter into at least one of the signal lines.
A single phase shifter is required to produce a phase shift of pi, while two or more phase shifters are required to add their phase shifts to a mutual phase difference of pi or more generally (2n +1) pi, where n is an integer. One possible solution combines a + pi/2 phase shifter and a-pi/2 phase shifter.
A simple solution according to the second case comprises a common wire as a shunt line to connect one of the two electrodes of the SAW transducer to the metallization arranged on the back side of the SAW chip. Such shunt lines prevent the build up of voltage between the transducers on the back and top surfaces. Such voltages may be the result of parasitic body waves according to the second harmonic H2. The bulk wave is reflected at the back surface, and standing waves accumulate. Depending on the resonant cavity, and therefore the thickness of the SAW chip, the bulk wave produces unwanted signals at different frequencies. Thereby, a potential difference occurs and as long as it is not short-circuited, a signal can be measured between the two surfaces, i.e. between the metallization (e.g. transducer) thereon and the backside metallization. Shorting these metallizations eliminates the voltage and suppresses the parasitic signals generated. It is essential that the back side metallization is floating and therefore has no connection to ground or a signal source.
The back side metallization may be a continuous metallization covering the total area of the back side of the SAW chip. However, it is preferred that the back metallization is built up by: separating and electrically isolating different partial areas thereof. Each region is opposite to only one single element on the top surface, e.g. opposite to the transducer. The partial regions may be limited in their lateral dimension to the area of the respective top surface element.
According to a further embodiment, a shunt resonator having a resonance frequency at or close to the spurious frequency is arranged in the shunt line, and the shunt line is connected to a ground potential. Thereby, the signal at the spurious frequency according to the resonance frequency of the shunt resonator is short-circuited, while the signal at the operating frequency is not or only negligibly affected.
The shunt resonator may be embodied as a SAW resonator. It may then be formed on the top surface of the SAW chip as additional metallization.
Alternatively, the shunt resonator may be a BAW resonator, or a resonator embodied in another technology in the form of a separate device.
In the first case (first embodiment), two or more second signal lines are connected in parallel with the first signal line. Each of the first signal line and the at least one second signal line includes the same components such that the amplitude of the desired signal and the amplitude of the spurious signal are the same in each signal line. The phase shifter is arranged in at least one of the signal lines and is adapted to shift a phase of the parasitic signal in the at least one second signal line with respect to the first signal line such that the parasitic signals cancel each other due to their phase difference. The useful signals are not subjected to a phase shift and therefore constructively interfere and add their amplitudes.
In a simple solution, the phase shifter is embodied as a SAW resonator with a resonance frequency at or close to the spurious frequency. The SAW resonator may be disposed on a top surface of a SAW chip of the SAW device.
According to a further embodiment, the signal line comprises cascaded resonators. This means that the single original resonator is replaced by a parallel circuit of two series circuits of two resonators each. In such a series circuit, a phase shift can be achieved if the two resonators are detuned with respect to each other. By detuning the two series circuits in opposite directions to each other, the resulting phase shift between the two series circuits can be set to pi at the spurious frequencies.
Since most filter circuits today comprise cascaded resonators, the inventive solution does not require any additional components, space, chip area, effort with respect to the state of the art.
In another embodiment, the phase shifter may be embodied as a symmetric pi member of an impedance element selected from a capacitance and an inductance. However, every other circuit that causes a phase shift is also possible. The phase shifters may be formed as discrete devices that are electrically connected within the respective signal lines. Furthermore, the impedance elements of the phase shifter may be integrated in a carrier substrate, which is part of the package of the SAW chip or its housing. The phase shifter operates in a small frequency band so that the signal at the operating frequency is not affected.
In the second case (second embodiment), the shunt lines may be guided through the SAW chip and may be embodied as vias or through contacts. Alternatively, the shunt lines comprise line conductors that are guided over and around the edges of the SAW chip. Furthermore, the shunt line may have a segment formed by a housing in which the SAW chip is arranged. The shunt line may even be formed entirely by the housing. Then, one electrode of the transducer needs to be connected to the housing, and the housing needs to be grounded. Independently of this, the back metallization can also be grounded, so that the electrode back metallization is short-circuited.
A further way in which standing wave build-up by parasitic bulk wave excitation can additionally be suppressed is to construct the backside in such a way that dispersion of the bulk wave impinging on the backside is achieved. Thereby, delayed (reflected) signals can be suppressed. The structuring may comprise a surface treatment of the piezoelectric chip or a structuring of the back metallization. The last case can be achieved with much lower effort than surface treatment by roughening, sawing, sandblasting or etching.
Finally, the proposed methods for suppressing spurious signals of the mentioned fields can be combined in every arbitrary combination. In particular, the first and second embodiments do not interact with each other and can be implemented in parallel. Thereby, spurious signals of different frequencies may be cancelled or suppressed when using respective frequency selective phase shifters in the first and second signal lines, and/or when implementing frequency selective shunt lines as already explained above.
The invention can be used to suppress spurious signals originating from other spurious effects, such as from the third harmonic H3. In this case, the frequency selective element (phase shifter and/or shunt element) should be optimized to the frequency of the third harmonic, which is 3f, where f is the operating frequency of the SAW device or filter circuit.
According to various embodiments, the SAW device may be or may include a ladder filter, a DMS filter, or a resonator.
The concept of the shunt element of the third embodiment is not limited to the SAW filter. Thus, the concept of providing a short circuit to ground selectively for signals of the frequency to be suppressed (e.g. H2) can also be applied in other filter technologies, e.g. in BAW filters. Even at filters that do not use acoustic signals, such as LC filters, for example, the inventive shunt element may be used in addition to known filter elements.
Drawings
Hereinafter, the present invention is explained in more detail with reference to specific embodiments and the accompanying drawings. The figures are merely schematic and not drawn to scale. Identical elements or elements with identical functions are referred to by identical reference symbols.
Fig. 1 shows different examples according to the first embodiment.
Fig. 2 shows an example according to a second embodiment.
Fig. 3 shows an example for a filter circuit different from those used in the first and second embodiments.
Fig. 4 shows a cross-sectional view of an arrangement with two SAW chips according to a first embodiment.
Fig. 5 shows a cross-sectional view of a SAW chip according to a second embodiment.
Fig. 6 shows a cross-sectional view of a different SAW chip with shunt lines according to a second embodiment.
Fig. 7 compares chip areas necessary for forming the resonator of the related art and the signal line according to the first embodiment.
Fig. 8 shows a SAW filter according to the present invention including shunt resonators.
Fig. 9 compares the two transfer functions of a filter circuit according to the second embodiment with and without the inventive shunt lines.
Fig. 10 shows an enlarged segment of the elements of the S12 matrix of the same filter circuit according to the second embodiment.
Fig. 11 illustrates the excitation of a parasitic bulk wave in a SAW device at the H2 frequency.
Fig. 11 shows a schematic view of a cross-section through a SAW device. An interdigital transducer including a transducer finger TRF is arranged on the top surface of the piezoelectric chip CHP. In a common finger transducer, the transducer fingers TRF are arranged in a generally regular pattern of π/2. At the resonant frequency f, the applied RF signal causes deflection of the transducer fingers so that the fingers move alternately up and down. At the harmonic frequencies of the transducers at the 2f frequency, the synchronous motion of all the transducer fingers can be considered as shown in fig. 11. This synchronized up and down movement of all transducer fingers causes bulk waves that propagate against the backside of the chip CHP to be excited. On the back side of the chip CHP, a back side metallization BSM may be applied. In either case, the bulk wave BWV is reflected at the back to form a reflected wave RWV. The reflected wave travels up to the top surface and may be reflected again at the top surface. Thereby, as in the bulk wave resonator, standing waves accumulate to form resonance. Bulk waves produce spurious signals at all frequencies, while satisfying the resonance condition for standing waves in a cavity of length h, where h is the distance between the transducer fingers TRF and the back metallization BSM in the figure. The parasitic signal can be seen as a potential difference between the back metallization BSM and the transducer finger TRF.
Detailed Description
It is an object of the invention to suppress these spurious signals whose origin is the second harmonic vibration of the transducer.
Fig. 1 shows a different arrangement according to a first embodiment which can achieve this object. Fig. 1 shows at a) signal lines which are split IN two symmetrical signal lines SL1 and SL2, the signal lines SL1 and SL2 being electrically connected IN parallel between the input IN and the output OUT. Each of the two signal lines SL includes a respective first or second filter circuit FC1 and FC2, which are identical and therefore operate in the same manner. Without further means, the two signal lines SL would add their amplitudes constructively at the output OUT. According to the invention, a phase shifter PS2 is inserted between one of the filter circuits FC and the output. In the figure, a phase shifter is inserted in the second
Variant b) differs only slightly from variant a) in the fact that: the phase shifter PS2 is arranged between the input IN and the second
According to variant c), the required phase shift pi between the two signal lines SL at the frequency to be suppressed is achieved by a first phase shifter PS1 arranged in the first signal line SL1 and a second phase shifter PS2 arranged in the second
The variant c) can be extended to the variant d) which includes a parallel circuit of n signal lines SL1 to SLn electrically connected in parallel. All n signal lines SL include the same filter circuit, such as the first filter circuit FC1 and the phase shifter PSn. The phase shifter PS is selected to cause a corresponding phase shift at the output OUT at the spurious signal frequency such that all frequency components of the spurious signal frequency cancel.
Fig. 2 shows an arrangement according to a second embodiment. The filter circuit FC is arranged IN the signal line SL between the input IN and the output OUT. The signal line and the filter circuit FC are arranged on top of the SAW chip. A backside metallization BSM is applied on the backside of the SAW chip, opposite the elements of the filter circuit FC. In this figure, the back side metallization BSM is depicted as a wire that may assume an electrical potential due to polarization of the piezoelectric material caused by spurious waves (such as second harmonics). According to a second embodiment, the invention proposes to electrically connect a shunt line SHL between the signal line SL and the back metallization BSM. The shunt line may be arranged near components of the filter circuit FC, which is located at a position where a maximum potential difference between the filter metallization at the top side and the back side metallization may accumulate. Through the shunt line SHL, the accumulated potential is equalized by the short circuit and thus eliminated.
According to a further development, further shunt lines SHL may be arranged at other locations between the signal lines SL and the back side metallization BSM. This may be necessary in the following cases: the back metallization BSM is separated in partial regions, which are electrically isolated with respect to one another. Each isolated partial region of the back side metallization BSM may then be connected to a signal line by a respective shunt line SHL.
Fig. 3 shows five different examples of circuits FC, or of components of a filter circuit, to which the invention can be applied. Fig. 3A depicts an exemplary filter circuit FC that is electrically connected in a signal line between an input and an output. The filter circuit may comprise different elements electrically or acoustically connected in series. Fig. 3B shows the interdigital transducer TRD electrically connected in a signal line as an essential component of such a SAW filter circuit FC. Another component of the filter circuit FC may be a resonator RES schematically shown in fig. 3C. The transducer as shown in fig. 3B may be part of a resonator, a DMS filter, or another longitudinally coupled resonator filter as shown in fig. 3D. As an example, the resonators shown in fig. 3C may be part of a resonator filter which is part of a ladder arrangement according to fig. 3E comprising series resonators arranged in a signal line and parallel resonators arranged in parallel branches connecting the signal line to ground potential.
Each filter circuit FC may also comprise other components, which may be a combination of the examples shown, or may comprise other elements not depicted in fig. 3.
Fig. 4 shows an example of a filter circuit according to the first embodiment and as implemented according to fig. 3E. As shown IN fig. 1A, the filter circuit FC includes a first signal line SL1 and a second signal line SL2 connected IN parallel circuit between the input IN and the output OUT. In each of the signal lines SL, the series resonators SR are electrically connected in series. The parallel resonators PR are electrically connected in parallel between the corresponding signal line SL and the ground potential GND. For the sake of simplicity, each of the resonators SR, PR is only schematically depicted by three transducer fingers which are interleaved with each other. The first and second filter circuits are depicted using separate chips, each of which is a first chip CHP1 and a
Fig. 5 shows a further variant of the invention according to a second embodiment. Here, the shunt line SHL schematically depicted in fig. 2 includes a shunt resonator SHR electrically connected between the signal line SL and the ground potential. The shunt resonator SHR differs from any resonator arranged in the signal line in its resonance frequency, which is at or close to the frequency of the spurious signal. As a result of this arrangement, the shunt line including the shunt resonator SHR is active only for frequencies close to the resonance frequency of the shunt resonator. Thus, the shunt line is frequency selective only for spurious signals. Such a shunt resonator SHR can advantageously be used in a resonator filter according to fig. 3E and can thus be embodied as another resonator on top of the SAW chip CHP. Alternatively, the shunt resonator SHR may be a separate device that is electrically connected only between the signal line and the ground GND. The separate device may be any type of resonator such as a SAW resonator, a bulk acoustic wave resonator or another technology resonator, e.g. an LC resonator. The shunt resonator SHR may be connected to the same ground line GND to which the parallel branches with the parallel resonators therein are connected.
Fig. 6 shows three examples of how shunt lines and back side metallization can be implemented. In fig. 6A, shunt lines SHL connect signal lines (a portion of which is depicted as a transducer in this figure) and the back metallization BSM on the opposite surface of the chip CHP. The shunt line SHL is partially led over the top surface, guided around the upper edge of the chip CHP, along the side surfaces and around the bottom edge.
Fig. 6B shows an example where the shunt lines are implemented as vias connecting the metallization on the top surface with the back metallization BSM on the bottom surface or back side of the chip CHP. The via may be embodied as a through-hole through the chip CHP, which is metallized at least at its side walls, or which is completely filled with a conductive material. The VIAs VIA extend from the metallization on the top surface to the opposite surface of the chip CHP under the back side metallization BSM.
If the SAW chip CHP has several transducers or several other filter components arranged on the top surface, it is possible to provide at least one further via connecting another component with the back side metallization BSM. Although the back side metallization BSM is depicted as a single layer covering the entire back side of the chip CHP, it may be advantageous to build up the back side metallization and to limit each sub-area of the back side metallization to the opposite area of the transducer to which the back side metallization is connected by the shunt lines.
Fig. 6C shows a variant in which the shunt lines are realized at least partially by the metallization of the housing or package in which the chip is enclosed. Inside the package, the chip CHP is mounted in a flip-chip arrangement on a carrier, which is for example a printed circuit board. The package for the chip comprises a cover layer applied on the chip and connected or sealed to the surface of the carrier such that the cavity is enclosed and sealed between the chip and the carrier. The cover layer comprises a shaping material and at least a conductive layer, while allowing the cover layer to be used as shunt lines SHL. Inside the carrier, the signal lines need to be connected to the conductive layers forming the shunt lines. By this, the signal line is short-circuited to the back metallization BSM. In this example, the cover layer must not be connected to ground. Alternatively, a second conductive cover layer is present over the housing to connect the housing to ground without also shorting the shunt line to ground.
Fig. 7 compares the necessary chip areas of the resonator RES and the filter circuit according to the first embodiment of the present invention. The single resonator operating with acoustic waves may be replaced by a cascaded resonator to achieve higher power durability, thereby improving the lifetime of the resonator. Cascading the individual resonators RES means that it is necessary to provide a series connection of a first resonator and a second resonator, each having twice the resonator area or capacity as the original individual resonator. Doubling the area or capacity of the cascaded resonators can be achieved by: the two series circuits of the first and second resonators are electrically connected in parallel, each of the first and second resonators having the same area as the original single resonator. Fig. 7B shows the signal line split into two parallel lines, which are connected at their two outermost ends. In each partial signal line, two resonators are connected in series. Thus, replacing the single resonator shown by fig. 7A with four resonators connected by a circuit as shown in fig. 7B gives a cascaded resonator that has the same properties as the single resonator, but with enhanced power durability and reduced non-linearity, as is known in the art.
Fig. 7C shows such a cascade resonator which is split into two signal lines and provided with a phase shifter PS in each of the two signal lines. The two phase shifters move the phase of the corresponding parasitic signal line in a direction opposite to that in the other signal line. By this, a phase difference of about pi can be realized, which is effective only for frequencies according to the spurious signals. As can be seen, the necessary chip area for implementing the invention according to the first embodiment is only slightly larger than the chip area for the cascaded resonators.
Another solution that does not require additional chip area has been indicated in fig. 7B and 7D. The resonators are referenced by different indices, meaning that the two resonators are slightly different. The two series-connected resonators are moved relative to one another at their resonant frequency so that the resonator RESAAnd resonator RESBWith different resonant frequencies. The order of the resonators referenced a and the resonators referenced B is interchanged in the respective other signal line. The frequency difference distance between the respective pairs of two series-connected resonators is selected such that a phase shift effective for the frequency of the spurious signal is produced for a part of the signal line. In the corresponding other signal lineAnd due to the interchanged order of the different resonators the corresponding phase shift is valid in the other direction. Therefore, by appropriately selecting the frequencies of the two resonators in each partial signal line of fig. 7B, the same effect as the arrangement shown in fig. 7C can be achieved. However, no additional area for the phase shifter is required, since here the phase shifting can be achieved without the implementation of further components. Similarly, and according to fig. 7D, resonators having different frequencies are used in different signal lines, but the same resonator is used within one of the signal lines.
Fig. 8A and 8B show two exemplary solutions that provide property improvements over comparable filter circuits without the present invention. Fig. 8A shows a T-segment of a ladder type arrangement, which includes first and second series resonators SR1 and SR2 connected in series within a signal line. Between the two series resonators, first and second parallel resonators PR1, PR2 (each arranged in a parallel branch of the circuit) are coupled to the signal line. Between the second parallel resonator PR2 and the second series resonator SR2, a parallel branch is coupled between the signal line and ground. In this branch, the shunt resonator SHR is arranged, the frequency of which is chosen to be about 2f if the parasitic H2 signal has to be suppressed. If H3 must be suppressed, the frequency is approximately 3f, and so on. The two series resonators SR and the two parallel resonators form a ladder-type arrangement to provide a pass band at the frequency f.
Fig. 9A shows the amplitude of the second harmonic that produces a peak at a frequency of about 2 f. The graph belonging to the structure shown in fig. 8A is depicted as
This non-linearity can be further reduced by the structure according to fig. 8B. Fig. 10 depicts the amplitude of only the spurious signal H2 and shows the improvement when comparing curve 2 (improvement according to fig. 8B) with curve 1 (structure according to fig. 8A as discussed above). The amplitude of the spurious H2 signal at a frequency of about 1875 MHz is greatly reduced.
The invention has been explained with reference to a limited number of specific embodiments, but is not limited to these embodiments. Variations and combinations of features described in the singular are also considered to fall under the scope. The scope of the invention should be limited only by the attached claims.
List of terms and reference symbols
BSM backside metallization
BWV body wave
CAR vector
CHP SAW chip
FC filter circuit
GND ground connection
IN (of signal lines) input
OUT (of signal line) output
PR parallel resonator
PS phase shifter
RES resonator
RWV reflection wave
SHL shunt line
SHR shunt resonator
SL signal line
SR series resonator
TRD (interdigital) transducer
TRF transducer finger
VIA VIA
1 transfer curve of reference example
2 transfer curve of the embodiment
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