CN213990622U - Chip structure of broadband low-loss surface acoustic wave filter - Google Patents
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Abstract
The utility model provides a broadband low-loss surface acoustic wave filter chip structure belongs to novel components and parts chip field. The utility model is used for solve present surface acoustic wave filter structure and have the very big problem of insertion loss when the broadband, be used for radio frequency signal to carry out shielded shielding strip part between radio frequency signal input part, radio frequency signal output part and input and the output part. Through the utility model discloses an above-mentioned structure can realize good stop band suppression.
Description
Technical Field
The utility model relates to a novel components and parts chip field, concretely relates to broadband low-loss surface acoustic wave filter chip structure.
Background
The Surface Acoustic Wave (SAW) filter is produced by adopting a semiconductor plane process, and has the advantages of small volume, light weight, good consistency, electromagnetic interference resistance, no need of debugging and the like. With the continuous growth of wireless communication services in China, the demand for low-loss filters is increasing day by day. To improve the system noise figure and reduce the required amplifier gain and power consumption, various Surface Acoustic Wave (SAW) filter low loss techniques have been developed.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a broadband low-loss surface acoustic wave filter chip structure has realized that broadband low-loss surface acoustic wave filter insertion loss is 21.1 dB's broadband low-loss target.
The utility model provides a its technical problem, the technical scheme of adoption is:
the chip structure of the broadband low-loss surface acoustic wave filter comprises a radio frequency signal input part, a radio frequency signal output part and a shielding strip part which is used for shielding radio frequency signals between the input part and the output part.
Further, the radio frequency signal input part is the input interdigital transducer, the structure of input interdigital transducer is single-phase one-way transducer structure, the finger width of interdigital strip is different in every cycle of input interdigital transducer for the surface acoustic wave that makes the input interdigital transducer arouse has the unidirectionality, and increases progressively towards the surface acoustic wave energy of output interdigital transducer direction propagation.
Further, the input interdigital transducer includes 40 sub-channels in the aperture direction of the filter, the 40 sub-channels have different acoustic synchronization frequencies and different apertures, and each sub-channel excites the surface acoustic wave at the acoustic synchronization frequency thereof for maximizing the electro-acoustic conversion efficiency of the input interdigital transducer.
Furthermore, the input interdigital transducer adopting the single-phase one-way transducer structure has 94 fingers in total, and the acoustic synchronization frequency and the aperture of 40 sub-channels of the input interdigital transducer are determined by carrying out polarity weighting processing on each finger.
Further, radio frequency signal output part is output interdigital transducer, output interdigital transducer's structure is single-phase one-way transducer structure, the finger width difference of interdigital strip in every cycle of output interdigital energy ware for make the surface acoustic wave that output interdigital transducer received have unidirectionality, and the surface acoustic wave energy that the orientation input interdigital transducer direction was received increases progressively.
Further, the output interdigital transducer includes 40 sub-channels along the aperture direction of the filter, the acoustic synchronization frequency and the aperture of the 40 sub-channels are the same as those of the input interdigital transducer, and each sub-channel receives the surface acoustic wave at the acoustic synchronization frequency thereof, so that the acoustic-electric conversion efficiency of the output interdigital transducer reaches the highest.
Furthermore, the output interdigital transducer adopting the single-phase one-way transducer structure has 94 fingers in total, and the acoustic synchronization frequency and the aperture of 40 sub-channels of the output interdigital transducer which are the same as the input interdigital transducer are determined by carrying out polarity weighting processing on the fingers without the fingers.
Furthermore, the upper parts and the lower parts of the input interdigital transducers and the output interdigital transducers are provided with pressure welding points.
The beneficial effects of the utility model are that, through above-mentioned broadband low-loss surface acoustic wave filter chip structure, through setting up the shielding strip part that is used for radio frequency signal to shield between radio frequency input part, radio frequency signal output part and input and the output part, can realize that broadband low-loss surface acoustic wave filter insertion loss is 21.1 dB's broadband low-loss target.
Drawings
Fig. 1 is a schematic diagram of the overall structure of the wideband low-loss saw filter chip structure of the present invention;
fig. 2 (a) is a diagram illustrating a conventional oblique transducer electrode shape in an embodiment of the present invention, and fig. 2 (b) is a diagram illustrating a quasi-oblique transducer electrode shape in an embodiment of the present invention;
fig. 3 is a schematic diagram of an overall structure of a quasi-tilted transducer structure filter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an operation principle of a quasi-tilted transducer structure filter according to an embodiment of the present invention;
FIG. 5 is a diagram of a single-phase unidirectional transducer used in an input interdigital transducer in an embodiment of the present invention;
fig. 6 is a structural diagram of a single-phase unidirectional transducer adopted by an output interdigital transducer in the embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be described in detail with reference to the accompanying drawings and embodiments.
The utility model provides a broadband low-loss surface acoustic wave filter chip structure, its overall structure schematic diagram is shown in figure 1, and wherein, this structure includes that it carries out the shielding strip part that shields to be used for radio frequency signal between radio frequency signal input part, radio frequency signal output part and input and the output part.
In the structure, the radio frequency signal input part can be called an input interdigital transducer, the structure of the input interdigital transducer can be a single-phase one-way transducer structure, the finger widths of interdigital strips in each period of the input interdigital transducer are different, the surface acoustic wave excited by the input interdigital transducer has one-way property, and the surface acoustic wave energy propagating towards the direction of the output interdigital transducer is increased progressively.
Here, for the input interdigital transducer, on the one hand: because the finger widths of the interdigital strips are different in each period of the interdigital transducer, the surface acoustic wave excited by the input interdigital transducer has unidirectionality, the surface acoustic wave energy propagated towards the direction of the output interdigital transducer is stronger, and the bidirectional loss of the surface acoustic wave excited by the input interdigital transducer is reduced; on the other hand: the input interdigital transducer is synthesized by 40 sub-channels along the aperture direction of the filter, the 40 sub-channels have different sound synchronous frequencies and different apertures, and each sub-channel excites the surface acoustic wave at the sound synchronous frequency of the sub-channel, so that the electro-acoustic conversion efficiency of the input interdigital transducer reaches the highest.
Meanwhile, the input interdigital transducer adopting the single-phase one-way transducer structure has 94 fingers in total, each finger is subjected to polarity weighting, the sound synchronization frequency and the aperture of 40 sub-channels of the input interdigital transducer are determined, the size of the pressure welding point at the upper part and the lower part of the input IDT and the size of the shielding strips at the left side and the right side connected with the pressure welding point of the input IDT are designed, and the realization of the electric parameters of the filter, such as the insertion loss of less than 22dB, the bandwidth of-3 dB more than or equal to 39.8Mhz, the out-of-band rejection more than 40dB, and the like is ensured.
Additionally, the utility model discloses in the radio frequency signal output part that mentions can be called as output interdigital transducer, the structure of output interdigital transducer be single-phase one-way transducer structure, and the output interdigital hua can the ware in every cycle the interdigital point the wide difference for the surface acoustic wave that makes output interdigital transducer receive has the unidirectionality, and the surface acoustic wave energy towards the receipt of input interdigital transducer direction increases progressively.
Here, for the output interdigital transducer, on the one hand: the output interdigital transducer adopts a single-phase one-way transducer structure, and because the finger widths of the interdigital strips in each period of the interdigital transducer are different, the surface acoustic wave received by the output interdigital transducer has one-way property, the surface acoustic wave energy received towards the direction of the input interdigital transducer is stronger, and the two-way loss of the surface acoustic wave received by the output interdigital transducer is reduced; on the other hand: the output interdigital transducer is synthesized by 40 sub-channels along the aperture direction of the filter like the input interdigital transducer, the sound synchronization frequency and the aperture of the 40 sub-channels are completely the same as those of the input interdigital transducer, and each sub-channel receives the surface acoustic wave at the sound synchronization frequency, so that the sound-electricity conversion efficiency of the output interdigital transducer reaches the highest.
Meanwhile, the output interdigital transducer adopting the single-phase one-way transducer structure has 94 interdigital transducers in total, each interdigital transducer is subjected to polarity weighting, the acoustic synchronization frequency and the aperture of 40 sub-channels of the output interdigital transducer are determined to be completely the same as those of the input interdigital transducer, the sizes of the pressure welding points on the upper part and the lower part of the output interdigital transducer and the sizes of the shielding strips on the left side and the right side connected with the pressure welding points of the output interdigital transducer are designed, and the realization of the equal electrical parameters of less insertion loss of a filter, more than 39.8Mhz, more than 40dB out-of-band suppression and the like is ensured.
And the shielding strip part size design of the radio frequency signal between the input interdigital transducer (used for exciting the surface acoustic wave) and the output interdigital transducer (used for receiving the surface acoustic wave) blocks the direct coupling of the radio frequency signal of the input end to the output end, and ensures that the insertion loss of the filter is less than 22dB, the bandwidth of-3 dB is more than or equal to 39.8Mhz, and the out-of-band rejection is more than 40dB, and the like.
Examples
The conventional surface acoustic wave filter structure has a problem that the insertion loss is large in a wide band because the IDT (interdigital transducer) of the periodic sampling has the highest acousto-electric conversion efficiency only at the frequency in acoustic synchronization with the IDT, and the farther from the center frequency, the lower the acousto-electric conversion efficiency. For this purpose, a tilted transducer (SLANT) is used, the electrode period varying along the aperture direction of the device. The lower electrode spacing of the device is smaller, exciting the signal in the high frequency portion of the passband, while the upper electrode spacing of the device is larger, exciting the signal in the low frequency portion.
Thus, the filter is divided into a plurality of sub-channels with different frequencies, for example, 8 sub-channels, each sub-channel generates a narrow pass band with different frequencies, that is, 8 narrow pass band frequency responses, and finally a wide pass band (total frequency response) is synthesized. Weighting the aperture of the sub-channels (adjusting the aperture size of each sub-channel) can achieve a fairly flat overall frequency response, and capacitively weighting, decimating weighting, finger polarity weighting, or finger apodization weighting the structure of the IDT can achieve good stop band rejection.
Each subchannel of the input and output oblique transducers of the filter can adopt finger strip polarity weighting so as to improve the out-of-band rejection and squareness index of the surface acoustic wave filter, and meanwhile, the aperture of each subchannel is weighted to control the response shape of a pass band. A broadband low-loss filter can be realized by adding a SPUDT (single-phase unidirectional transducer) design such as DART or DWSF on the basis of a SLANT transducer (SLANT).
Therefore, the embodiment designs and develops a novel chip structure of a SLANT/SPUDT broadband low-loss surface acoustic wave filter, and achieves broadband low-loss targets of a broadband low-loss surface acoustic wave filter (the central frequency is 76.8Mhz, -the 3dB bandwidth is more than or equal to 39.8Mhz (-the relative bandwidth of 3dB is 51.8%), -the 40dB bandwidth is less than or equal to 50Mhz, the out-of-band rejection is more than 40dB), and the insertion loss is less than 22 dB.
Referring to fig. 2, wherein (a) in fig. 2 is the electrode shape diagram of the conventional tilt transducer in the embodiment of the present invention, and (b) in fig. 2 is the electrode shape diagram of the quasi-tilt transducer in the embodiment of the present invention, this embodiment is a design method for reducing insertion loss of the wideband surface acoustic wave filter by using a quasi-tilt interdigital transducer (SLANT) (as shown in (b) of fig. 2) the electrode shape of the quasi-tilt interdigital transducer), that is, the filter chip is composed of two quasi-tilt interdigital transducers for input and output and a shielding strip between the two quasi-tilt interdigital transducers.
Wherein: firstly, two quasi-inclined interdigital transducers for input and output in the filter chip adopt a single-phase one-way transducer structure, and each quasi-inclined interdigital transducer reduces two-way loss; secondly, input and output two quasi-inclined interdigital transducers in the filter chip are synthesized by 40 sub-channels along the aperture direction of the filter, and each sub-channel excites and receives surface acoustic waves at the acoustic synchronization frequency of the sub-channel, so that the acoustic-electric conversion efficiency of the filter is the highest.
Here, the present embodiment does not adopt the conventional oblique transducer electrode shape shown in (a) in fig. 2, but adopts the quasi-oblique transducer electrode shape shown in (b) in fig. 2, the overall structure schematic diagram of the filter chip composed of the input and output two quasi-oblique interdigital transducers and the shielding strip between the two quasi-oblique interdigital transducers is shown in fig. 3, as can be seen from fig. 3, the two quasi-oblique interdigital transducers in the filter chip are composed of a1, …, Ai, …, AN subchannels, in the present embodiment, AN is 40, i.e., there are 40 subchannels, each two subchannels are connected by a connecting strip δ Ai, in fig. 3, the a1 subchannel and the Ai subchannel are connected by a connecting strip δ a1, the Ai subchannel and the AN subchannel are connected by a connecting strip δ Ai, 39 connecting strips (channels) are shared between the a1 subchannel and the 40 subchannels of the AN subchannel, i.e., δ Ai has an i value from 1 to 39.
Referring to fig. 4, which is a schematic diagram of a working principle of a quasi-tilted transducer structure filter in this embodiment, here, because a wideband low-loss surface acoustic wave filter in this embodiment uses a piezoelectric single crystal as a substrate material, an input interdigital transducer of an a1 sub-channel, under excitation of an input electrical signal, excites a surface acoustic wave that propagates in two directions in an a1 sub-channel according to an inverse piezoelectric effect of the piezoelectric material, when the surface acoustic wave that propagates in a direction toward the output interdigital transducer reaches an area of the output interdigital transducer, the output interdigital transducer receives the surface acoustic wave and converts the surface acoustic wave into an electrical signal for output according to the piezoelectric effect of the piezoelectric material, and the surface acoustic wave that propagates in a direction opposite to the output interdigital transducer and is excited by the input interdigital transducer is absorbed by a sound absorbing material used in a subsequent process. In the a1 subchannel of the present embodiment, the finger widths of the input and output interdigital transducers are uniform and constant, the excitation and reception surface acoustic wave wavelength thereof is λ 1, and the frequency response center frequency of the corresponding a1 subchannel is f 1.
The same principle is that: in the a2 subchannel of the present embodiment, the finger widths of the input and output interdigital transducers are uniform and constant, the wavelength of the surface acoustic wave excited and received is λ 2, and the frequency response center frequency of the corresponding a2 subchannel is f 2; in the Ai subchannel of the embodiment, the widths of the fingers of the input and output interdigital transducers are uniform and invariable, the wavelength of the surface acoustic wave excited and received by the interdigital transducers is lambdai, and the frequency response center frequency of the corresponding Ai subchannel is fi; in the Ai subchannel of the present embodiment, the finger widths of the input and output interdigital transducers are uniform and constant, the surface acoustic wave wavelength to be excited and received is λ 40, and the frequency response center frequency of the corresponding a40 subchannel is f 40.
In summary, the total frequency response of the wideband low-loss saw filter in this embodiment is the sum of the frequency responses of 40 subchannels, which are the a1 subchannel, the a2 subchannel, … …, the Ai subchannel, … …, and the a40 subchannel.
Therefore, the two quasi-tilted interdigital transducers in the filter chip of the present embodiment are composed of 40 sub-channels, such as a1, …, Ai, …, a40, etc., and the center frequency and the surface acoustic wave wavelength of each sub-channel are different, which makes the input interdigital transducer length of each sub-channel different, and in the same way, the output interdigital transducer length of each sub-channel is different. Each sub-channel in this embodiment is connected by one and another quadrilateral, the connection of which is shown as delta a1 connecting bar in the above figure (for connecting the a1 sub-channel and the Ai sub-channel), and delta Ai connecting bar in the above figure (for connecting the Ai sub-channel and the AN sub-channel).
In addition, in this embodiment, the details of the determination of the parameters of the center frequency and the aperture length of the 40 sub-channels of the input and output interdigital transducers, the finger structure of the single-phase unidirectional transducer selected by the input and output interdigital transducers, and the finger polarity weighting scheme are as follows:
according to the electrical parameter requirements of the saw filter in this embodiment, in order to optimize the insertion loss and reduce the bidirectional loss of the input interdigital transducer, the input interdigital transducer in this embodiment employs a single-phase unidirectional transducer, whose structure is shown in fig. 5, where λ (λ ═ Vs/Fo, Vs is the saw wave velocity, and Fo is a certain channel center frequency) is a certain channel saw period wavelength, 4 interdigital strips are present in each period, 2 interdigital strips are present in each period, 4 interdigital strips are present instead of the original 2 interdigital strips, the widths of the interdigital strips are a1 and a2, and each of a1 and a2 is (3 λ/16) and (λ/16), respectively.
As shown in fig. 5, the widths of the interdigital strips are different in each period of the IDT, so that the surface acoustic wave excited by the input interdigital transducer has unidirectionality, the surface acoustic wave propagating towards the output interdigital transducer has stronger energy, and the bidirectional loss of the surface acoustic wave excited by the input interdigital transducer is reduced; on the other hand, the input interdigital transducer is synthesized by 40 sub-channels along the aperture direction of the filter (perpendicular to the propagation direction of the surface acoustic wave), the 40 sub-channels have different acoustic synchronization frequencies (central frequencies) and different apertures, and each sub-channel excites the surface acoustic wave at the acoustic synchronization frequency thereof, so that the electro-acoustic conversion efficiency of the input interdigital transducer is maximized.
According to the electrical parameter requirements of the saw filter in this embodiment, in order to optimize out-of-band rejection, the input interdigital transducer adopting the structure of the single-phase unidirectional transducer shown in fig. 5 has 94 fingers (i.e. 23.5 cycles), each finger is subjected to polarity weighting, and the sound synchronization frequency (center frequency) and aperture of 40 sub-channels of the input interdigital transducer are determined, which is specifically as follows:
1) given that the polarity of the electrode connecting the upper bonding pads of the input interdigital transducer is-1 and the polarity of the electrode connecting the lower bonding pads of the input interdigital transducer is +1, the input interdigital transducer 94 has the following weighting of the polarities of the fingers (from left to right) as shown in table 1 below:
| number of finger | Polarity of finger | Number of finger | Polarity of finger | Number of finger | Polarity of finger | Number of finger | Polarity of finger | Number of finger | Polarity of finger |
| 1 | +1 | 21 | +1 | 41 | +1 | 61 | +1 | 81 | +1 |
| 2 | +1 | 22 | +1 | 42 | +1 | 62 | +1 | 82 | +1 |
| 3 | -1 | 23 | -1 | 43 | -1 | 63 | -1 | 83 | -1 |
| 4 | -1 | 24 | -1 | 44 | -1 | 64 | -1 | 84 | -1 |
| 5 | +1 | 25 | +1 | 45 | +1 | 65 | +1 | 85 | +1 |
| 6 | +1 | 26 | +1 | 46 | +1 | 66 | +1 | 86 | +1 |
| 7 | -1 | 27 | -1 | 47 | -1 | 67 | -1 | 87 | -1 |
| 8 | -1 | 28 | -1 | 48 | -1 | 68 | -1 | 88 | -1 |
| 9 | +1 | 29 | +1 | 49 | +1 | 69 | +1 | 89 | +1 |
| 10 | +1 | 30 | +1 | 50 | +1 | 70 | +1 | 90 | +1 |
| 11 | -1 | 31 | -1 | 51 | -1 | 71 | -1 | 91 | -1 |
| 12 | -1 | 32 | -1 | 52 | -1 | 72 | -1 | 92 | -1 |
| 13 | +1 | 33 | +1 | 53 | +1 | 73 | +1 | 93 | +1 |
| 14 | +1 | 34 | +1 | 54 | +1 | 74 | +1 | 94 | +1 |
| 15 | -1 | 35 | -1 | 55 | -1 | 75 | -1 | ||
| 16 | -1 | 36 | -1 | 56 | -1 | 76 | -1 | ||
| 17 | +1 | 37 | +1 | 57 | +1 | 77 | +1 | ||
| 18 | +1 | 38 | +1 | 58 | +1 | 78 | +1 | ||
| 19 | -1 | 39 | -1 | 59 | -1 | 79 | -1 | ||
| 20 | -1 | 40 | -1 | 60 | -1 | 80 | -1 |
2) The acoustic synchronization frequencies (center frequencies) of the 40 sub-channels of the input and output interdigital transducers are determined as follows in table 2:
3) the aperture lengths of the input and output interdigital transducers (IDTs) 40 sub-channels are determined as follows in Table 3:
in addition, according to the electrical parameter requirements of the saw filter in this embodiment, in order to optimize the insertion loss and reduce the bidirectional loss of the output interdigital transducer, the output interdigital transducer in this embodiment adopts a single-phase unidirectional transducer, and its structure is shown in fig. 6, where λ (λ ═ Vs/Fo, Vs is the saw wave velocity, and Fo is a certain channel center frequency) is a certain channel saw period wavelength, 3 interdigital strips are shared in each cycle, 2 interdigital strips are shared in each cycle, 3 interdigital strips replace the original 2 interdigital strips, the widths of the interdigital strips are respectively a1, a2 and a3, the width of a1 is (2 λ/17), a2 is (4 λ/17), and a3 is (3 λ/17).
As shown in fig. 6, due to the fact that the widths of the interdigital strips are different in each period of the IDT, the surface acoustic wave received by the output interdigital transducer has unidirectionality, the surface acoustic wave received towards the input interdigital transducer has stronger energy, and the bidirectional loss of the surface acoustic wave received by the output interdigital transducer is reduced; on the other hand, the output interdigital transducer is synthesized by 40 sub-channels along the aperture direction of the filter (vertical to the propagation direction of the surface acoustic wave), the 40 sub-channels have different acoustic synchronization frequencies (central frequencies) and different apertures, and each sub-channel excites the surface acoustic wave at the acoustic synchronization frequency of the sub-channel, so that the acoustoelectric conversion efficiency of the output interdigital transducer reaches the highest.
According to the electrical parameter requirements of the saw filter in this embodiment, in order to optimize out-of-band rejection, the output interdigital transducer adopting the structure of the single-phase unidirectional transducer shown in fig. 2 has 94 fingers (i.e. 31.33 cycles), each finger is subjected to polarity weighting, and the sound synchronization frequency (center frequency) and aperture of 40 sub-channels of the output interdigital transducer are determined, which is specifically as follows:
1) given that the polarity of the electrode connecting the upper bonding pads of the output interdigital transducer is-1 and the polarity of the electrode connecting the lower bonding pads of the output interdigital transducer is +1, the polarity of 94 fingers of the output interdigital transducer is weighted (from left to right) as shown in table 4 below:
2) the acoustic synchronization frequency (center frequency) and aperture length of the 40 sub-channels of the output interdigital transducer are identical to those of the input interdigital transducer, see table 2 and table 3 above.
As described above, the input interdigital transducer adopts the single-phase unidirectional transducer structure of fig. 5, and has 94 interdigital fingers (23.5 cycles), and the interdigital finger of a certain channel is connected with the upper and lower channels or the bonding areas in the input interdigital transducer according to the finger polarity weighting manner of table 1, so that the input interdigital transducer with 40 channels is formed; similarly, the output interdigital transducer adopts the single-phase one-way transducer structure shown in fig. 6, and has 94 interdigital fingers (31.33 cycles), and the interdigital finger of a certain channel is connected with the upper and lower channels or the bonding areas in the output interdigital transducer according to the finger polarity weighting mode shown in table 4, so that the output interdigital transducer with 40 channels is formed.
In addition, according to the electrical parameter requirement of the SAW filter in this embodiment, to optimize the insertion loss, Y-cut 127.86 ° lithium niobate (Li) is selectedNbO3) The piezoelectric single crystal is a substrate material of the low-loss surface acoustic wave filter chip of the embodiment, and the main parameters are as follows:
according to the technical solution of the utility model, for obtaining the low-loss surface acoustic wave filter chip photoetching mask plate making data of the CIF format, a low-loss surface acoustic wave filter chip structure computer data output program is compiled, and the plate making data is sent to an outsourcing unit to make the photoetching mask plate. The filter chip was finally sized 9mm (length) 4mm (width) 0.5mm (height) and mounted in an SMD1365 surface mounted ceramic package housing. The external photoetching mask is produced on the production line flow sheet of the surface acoustic wave filter of the company, and the obtained frequency response curve of the surface acoustic wave filter reaches the technical aim of the embodiment. The-3 dB bandwidth of the broadband low-loss surface acoustic wave filter is 39.8Mhz, the out-of-band rejection is more than 40dB), the insertion loss is 21.2dB, and the-40 dB bandwidth is 50Mhz, so that the broadband low-loss target to be realized by the embodiment is achieved.
Therefore, this embodiment reduces the insertion loss of the wideband surface acoustic wave filter by adopting a novel chip structure of the SLANT/SPUDT wideband low-loss surface acoustic wave filter, and compared with the chip structure of the conventional transverse high-loss surface acoustic wave filter, the chip structure of this embodiment can optimize the insertion loss of the filter by 15-20 dB. In addition, the chip structure of the SLANT/quasi-SLANT transducer electrode shape wideband low-loss surface acoustic wave filter of the embodiment uses the minimum number of acoustic channels (40 sub-channels), and compared with the chip structure of the traditional SLANT transducer electrode shape surface acoustic wave filter, the chip structure greatly reduces the number of acoustic channels and the plate making data volume, is easier to manufacture an optical mask plate, and can reduce the chip size by 10-15% or improve the rectangular coefficient.
Claims (6)
1. The chip structure of the broadband low-loss surface acoustic wave filter is characterized by comprising a radio frequency signal input part, a radio frequency signal output part and a shielding strip part which is arranged between the input part and the output part and used for shielding radio frequency signals;
the radio frequency signal input part is an input interdigital transducer, the structure of the input interdigital transducer is a single-phase one-way transducer structure, the finger widths of interdigital strips in each period of the input interdigital transducer are different, and the input interdigital transducer is used for enabling surface acoustic waves excited by the input interdigital transducer to have unidirectionality and increasing the surface acoustic wave energy transmitted towards the direction of the output interdigital transducer;
the radio frequency signal output part is the output interdigital transducer, the structure of output interdigital transducer is single-phase one-way transducer structure, the finger width difference of interdigital finger in every cycle of output interdigital energy ware for the surface acoustic wave that makes the output interdigital transducer receive has the unidirectionality, and the surface acoustic wave energy that orientation input interdigital transducer direction was received increases progressively.
2. The wideband low loss saw filter chip structure of claim 1 wherein the input interdigital transducer includes 40 sub-channels along the filter aperture direction, the 40 sub-channels having different acoustic synchronization frequencies and different apertures, each sub-channel exciting a surface acoustic wave at its acoustic synchronization frequency for maximizing the electro-acoustic conversion efficiency of the input interdigital transducer.
3. The chip structure of the wideband low-loss surface acoustic wave filter of claim 2, wherein the input interdigital transducer using the single-phase unidirectional transducer structure has 94 fingers in total, and the acoustic synchronization frequency and the aperture of 40 sub-channels of the input interdigital transducer are determined by performing polarity weighting processing on each finger.
4. The wideband low loss saw filter chip structure of claim 1 wherein the output idt comprises 40 subchannels in the filter aperture direction, the 40 subchannels have the same acoustic synchronization frequency and aperture as the input idt, and each subchannel receives surface acoustic waves at its acoustic synchronization frequency for maximizing the acousto-electric conversion efficiency of the output idt.
5. The chip structure of the wideband low-loss surface acoustic wave filter of claim 4, wherein the output interdigital transducers adopting the single-phase unidirectional transducer structure have 94 fingers in total, and the acoustic synchronization frequency and the aperture of 40 sub-channels of the output interdigital transducers which are the same as those of the input interdigital transducers are determined by performing polarity weighting processing on no finger.
6. The chip structure of the wideband low loss surface acoustic wave filter according to any of claims 1-5, characterized in that the upper and lower parts of the input and output interdigital transducers are provided with pressure pads.
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