CN101997513B - Multi-coupling filter - Google Patents

Abstract

The embodiment of the invention discloses a multi-coupling filter which comprises at least two adjacently stacked coupling filters and a filter isolation layer located between the two adjacent coupling filters. The filter isolation layer comprises two adjacently stacked Bragg layers, wherein the reflection directions of the two Bragg layers are opposite so as to realize signal isolation between the adjacently stacked coupling filters and avoid mutual influence among multiple stacked coupling filters.

Description

Multi-Coupling Filter

technical field

The invention relates to the technical field of communication, in particular to a multi-coupling filter.

Background technique

With the development of wireless communication technology, the circuit complexity of products is getting higher and higher, which makes the filter tend to be miniaturized and integrated. At present, radio frequency filters mainly include dielectric filters, surface acoustic filters and filters based on thin film bulk acoustic resonators (FBAR, Thin Film Bulk Acoustic Resonator). The dielectric filter has the disadvantage of large volume, and the surface acoustic filter is limited by the photolithography process, and the insertion loss is large, so the application of these two filters is limited. The filter based on FBAR is widely used in the field of wireless communication technology due to its advantages of low insertion loss, high operating frequency, small size and easy integration.

At present, there are mainly two types of filters based on FBAR:

(1) Stacked filter, including two adjacent stacked FBARs, and a grounded electrode between the two FBARs.

(2) Coupled Resonator Filters (CRF, Coupled Resonator Filters), CRF includes two adjacent stacked FBARs, and an acoustic coupling layer between the two FBARs, by adjusting the number of acoustic layers of the acoustic coupling layer and each The thickness of the acoustic layer can tune the bandwidth of the CRF.

During the research and practice of the prior art, the inventors of the present invention found that although the FBAR-based filter has the advantages of small size and easy integration, if a plurality of FBAR-based filters are directly stacked together, The acoustic and electric fields of each filter will couple with each other, affecting the performance of the FBAR and causing impedance mismatch. Therefore, when a communication terminal needs to use multiple filters at the same time, each filter cannot be stacked together, but needs to be placed in different positions on the chip, resulting in a large chip area, and it is difficult to realize the miniaturization and integration of the filter module of the communication terminal. design.

Contents of the invention

An embodiment of the present invention provides a multi-coupling filter, which enables multiple filters to be stacked together without affecting each other, so as to realize miniaturization and integrated design of filter modules.

A multi-coupling filter provided by an embodiment of the present invention includes: at least two adjacent stacked coupling filters, and a filter isolation layer between two adjacent stacked coupling filters; The isolation layer includes two Bragg layers stacked adjacently, and the reflection direction of the two Bragg layers faces away, so as to realize signal isolation between adjacently stacked coupled filters;

Wherein, the coupled filter includes two adjacent stacked thin film bulk acoustic resonators, and an acoustic coupling layer located between the two adjacent stacked thin film bulk acoustic resonators.

A series-parallel combined multi-coupling filter provided by an embodiment of the present invention includes: at least two of the above-mentioned multi-coupling filters, and the multi-coupling filters are connected in parallel.

The multi-coupled filter in the embodiment of the present invention includes at least two adjacently stacked coupled filters, and a filter isolation layer between adjacent two coupled filters; the filter isolation layer includes adjacently stacked Two Bragg layers, and the reflection directions of the two Bragg layers are facing away, so as to realize the isolation of signals between adjacent stacked coupling filters, so that multiple filters are stacked together without affecting each other, realizing The miniaturization and integration design of the filter module of the communication terminal.

Description of drawings

Fig. 1 is a schematic diagram of an embodiment of a multi-coupling filter in an embodiment of the present invention;

Fig. 2 is an enlarged schematic diagram of the position of circle a in Fig. 1;

FIG. 3 is a schematic diagram of another embodiment of a multi-coupling filter in an embodiment of the present invention;

FIG. 4 is a schematic diagram of another embodiment of a multi-coupling filter in an embodiment of the present invention;

Fig. 5 is the frequency response diagram obtained by multi-coupling filter simulation in the embodiment shown in Fig. 4;

Fig. 6 is a frequency response diagram of the cellular wireless communication system (Cellular) frequency band receiving band in Fig. 5;

Fig. 7 is a frequency response diagram of the receiving band of the Personal Communications Service (PCS, Personal Communications Service) frequency band in Fig. 5 .

Detailed ways

An embodiment of the present invention provides a multi-coupling filter, which enables multiple filters to be stacked together without affecting each other, thereby realizing miniaturization and integrated design of a filter module of a communication terminal. The details will be described below.

A multi-coupled filter in an embodiment of the present invention includes at least two adjacently stacked coupled filters, and a filter isolation layer between two adjacently stacked coupled filters; the filter isolation layer It includes two Bragg layers stacked adjacently, and the reflection directions of the two Bragg layers are opposite to each other, so as to realize signal isolation between adjacently stacked coupling filters.

Please refer to FIG. 1 . FIG. 1 is a schematic diagram of an embodiment of a multi-coupling filter in an embodiment of the present invention. The multi-coupled filter 1 in this embodiment includes adjacently stacked CRF200 and CRF300, and a filter isolation layer 400 between the CRF200 and CRF300. The CRF200 is disposed below the CRF300 , and the CRF200 is disposed on the substrate 102 .

CRF 200 includes FBAR 210 and FBAR 220 stacked adjacently, and acoustic coupling layer 230 between FBAR 210 and FBAR 220 .

FBAR 210 includes electrode 214 , electrode 212 , and piezoelectric film 216 between electrode 214 and electrode 212 . FBAR 220 includes electrode 224 , electrode 222 , and piezoelectric film 226 between electrode 224 and electrode 222 . The electrode 214 and the electrode 212 serve as the signal input end of the CRF200 , and the electrode 224 and the electrode 222 serve as the signal output end of the CRF200 .

The acoustic coupling layer 230 is located between the electrode 214 of the FBAR 210 and the electrode 222 of the FBAR 220, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 230 The number and the thickness of each acoustic layer can adjust the coupling strength between FBAR210 and FBAR220, and can adjust the bandwidth of CRF200.

CRF 300 includes adjacently stacked FBAR 310 and FBAR 320 , and an acoustic coupling layer 330 between FBAR 310 and FBAR 320 .

The FBAR 310 includes an electrode 314 , an electrode 312 , and a piezoelectric film 316 between the electrode 314 and the electrode 312 . The FBAR 320 includes an electrode 324 , an electrode 322 , and a piezoelectric film 326 between the electrode 324 and the electrode 322 . Electrode 314 and electrode 312 serve as signal input terminals of CRF300 , and electrode 324 and electrode 322 serve as signal output terminals of CRF300 .

The acoustic coupling layer 330 is located between the electrode 314 of the FBAR310 and the electrode 322 of the FBAR320, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 330 The number and the thickness of each acoustic layer can adjust the coupling strength between FBAR310 and FBAR320, and the bandwidth of CRF300 can be adjusted.

Please refer to FIG. 2 , which is an enlarged schematic diagram of the position of circle a in FIG. 1 . It can be seen from FIG. 2 that the filter isolation layer 400 includes a Bragg layer 410 and a Bragg layer 420 stacked adjacently. The reflection directions of the Bragg layer 410 and the Bragg layer 420 are opposite, so that the Bragg layer 410 constitutes the upper boundary of the acoustic wave confinement of the CRF200, and the Bragg layer 420 constitutes the lower boundary of the acoustic wave confinement of the CRF300, so as to realize signal communication between adjacently stacked CRF200s and CRF300s. isolation.

The Bragg layer includes at least two reflective layers made of acoustic materials with different characteristic acoustic impedances. For example, the Bragg layer may include a first acoustic wave impedance layer and a second acoustic wave impedance layer, and the difference between the characteristic acoustic impedances of the second acoustic wave impedance layer and the first acoustic wave impedance layer is greater than or equal to 3. Each reflective layer of the Bragg layer can be made of Al, Au, Ti, Mo, W, Fe, Cr, Ni, Co, Cu, SiO2, Si3N4, ZnO, TiO2, TiN, Al2O3, AlN or PZT.

In this embodiment, the Bragg layer 410 includes the following four reflective layers: a first acoustic wave impedance layer 412 adjacent to the electrode 224 of the FBAR 220, a second acoustic wave impedance layer 414 adjacent to the first acoustic wave impedance layer 412, and a second acoustic wave impedance layer 414 adjacent to the first acoustic wave impedance layer 412. The first acoustic impedance layer 416 adjacent to the acoustic impedance layer 414, and the second acoustic impedance layer 418 adjacent to the first acoustic impedance layer 416; the Bragg layer 420 may include the following four reflective layers: The first acoustic wave impedance layer 428, the second acoustic wave impedance layer 426 adjacent to the first acoustic wave impedance layer 428, the first acoustic wave impedance layer 424 adjacent to the second acoustic wave impedance layer 426, and the first acoustic wave impedance layer 424 adjacent to the first acoustic wave impedance layer. 424 is adjacent to the second acoustic impedance layer 422 .

In this embodiment, the characteristic acoustic impedance of the second acoustic wave impedance layer is higher than that of the first acoustic wave impedance layer, and the difference between the characteristic acoustic impedance of the second acoustic wave impedance layer and the first acoustic wave impedance layer is equal to 15.

It can be understood that the Bragg layer 410 may also include two reflective layers, the first acoustic wave impedance layer and the second acoustic wave impedance layer arranged from bottom to top, or the first acoustic wave impedance layer, Three reflective layers of the first acoustic wave impedance layer and the second acoustic wave impedance layer, or two sets of first acoustic wave impedance layers and four reflective layers of the first acoustic wave impedance layer arranged from bottom to top. In this article, the direction from CRF200 to CRF300 is defined as the direction from bottom to top.

Similarly, the Bragg layer 420 may also include two reflective layers, the first acoustic impedance layer and the second acoustic impedance layer arranged from top to bottom, or the first acoustic impedance layer, the first acoustic impedance layer and the first acoustic impedance layer arranged from top to bottom. Three reflective layers of the acoustic wave impedance layer and the second acoustic wave impedance layer, or two sets of first acoustic wave impedance layers and four reflective layers of the first acoustic wave impedance layer arranged from top to bottom.

The value range of the thickness of each reflective layer of the Bragg layer 410 and the Bragg layer 420 can be [n*85%, n*115%], n is the wavelength of the acoustic signal whose frequency is equal to the first frequency in the acoustic material corresponding to the reflective layer an odd multiple of a quarter of , the first frequency is the center frequency of the coupled filter adjacent to the Bragg layer, that is, corresponding to the Bragg layer 410, and the first frequency is the center frequency of the CRF200 adjacent to the Bragg layer 410, corresponding to For the Bragg layer 420 , the first frequency is the center frequency of the CRF 300 adjacent to the Bragg layer 420 .

In this embodiment, the thickness of each reflective layer of the Bragg layer 410 is a quarter of the wavelength of the acoustic signal in the acoustic material corresponding to the reflective layer with a frequency equal to the center frequency of the CRF200, and the thickness of each reflective layer of the Bragg layer 420 is the frequency An acoustic signal equal to the center frequency of the CRF300 has a quarter of the wavelength in the acoustic material corresponding to the reflective layer.

For example, the value range of the thickness of the first acoustic wave impedance layer 412 of the Bragg layer 410 may be [m*85%, m*115%], wherein, m=(2a+1)λ ₁ /4, λ ₁ is The wavelength of an acoustic signal with a frequency equal to the center frequency of the CRF 200 in the acoustic material corresponding to the first acoustic wave impedance layer 412 , a is an integer greater than or equal to zero. In this embodiment, the thickness of the first acoustic wave impedance layer 412 is equal to λ ₁ /4.

For example, the value range of the thickness of the first acoustic wave impedance layer 428 of the Bragg layer 420 may be [q*85%, q*115%], wherein, q=(2a+1)λ ₂ /4, λ ₂ is The wavelength of an acoustic signal with a frequency equal to the central frequency of the CRF 300 in the acoustic material corresponding to the first acoustic wave impedance layer 428 , a is an integer greater than or equal to zero. In this embodiment, the thickness of the first acoustic wave impedance layer 428 is equal to λ ₁ /4.

The multi-coupled filter in this embodiment includes adjacently stacked CRF200 and CRF300, and a filter isolation layer 400 between CRF200 and CRF300. The filter isolation layer 400 includes adjacently stacked Bragg layers 410 and 420 whose reflection directions are facing away from each other. The thickness range of each reflective layer of the Bragg layer is [n*85%, n*115%], that is, greater than Equal to n*85% and less than or equal to n*115%, n is an odd multiple of a quarter of the wavelength of an acoustic signal with a frequency equal to the first frequency in the acoustic material corresponding to the reflective layer, corresponding to the Bragg layer 410 and the Bragg layer 420 , the first frequencies are respectively the center frequency of the CRF200 adjacent to the Bragg layer 410 and the center frequency of the CRF300 adjacent to the Bragg layer 420, so that the Bragg layer 410 constitutes the upper acoustic confinement of the CRF200 adjacent to the lower surface of the filter isolation layer 400 Boundary, the Bragg layer 420 constitutes the acoustic wave confinement lower boundary of the CRF300 adjacent to the upper surface of the filter isolation layer 400, so that the CRF200 and the CRF300 are stacked together without mutual influence, and the miniaturization and integration of the filter module of the communication terminal are realized design.

It can be understood that, in another embodiment of the present invention, the multi-coupling filter may include at least two adjacent stacked CRFs, and a filter isolation layer located between the two adjacent CRFs. For ease of understanding, the following multi-coupling filter includes three adjacent stacked CRFs, and a filter isolation layer between two adjacent CRFs, and each Bragg layer includes two layers of acoustic materials with different acoustic impedances The manufactured reflective layer is taken as an example to describe the multi-coupling filter in the embodiment of the present invention.

Please refer to FIG. 3 . FIG. 3 is a schematic diagram of another embodiment of a multi-coupling filter in an embodiment of the present invention. The multi-coupling filter 3 in this embodiment includes adjacently stacked CRF500, CRF700 and CRF900, and a filter isolation layer 600 between CRF500 and CRF600, a filter isolation layer 800 between CRF700 and CRF900, CRF500 set on the substrate 1202.

The filter isolation layer 600 is composed of a Bragg layer 610 and a Bragg layer 620 stacked adjacently, and the reflection direction of the Bragg layer 610 and the Bragg layer 620 are opposite to each other, so as to realize signal isolation between the adjacently stacked CRF500 and CRF700. The filter isolation layer 800 is composed of a Bragg layer 810 and a Bragg layer 820 , and the reflection directions of the Bragg layer 810 and the Bragg layer 820 are opposite to each other, so as to realize signal isolation between adjacently stacked CRF900 and CRF700 . Therefore, the filter isolation layer 600 and the filter isolation layer 800 realize the isolation of signals between the CRF500 , the CRF700 and the CRF900 .

Specifically, the Bragg layer 610 includes the following two reflective layers: a first acoustic wave impedance layer 612 adjacent to the upper surface of the CRF500, and a second acoustic wave impedance layer 614 adjacent to the first acoustic wave impedance layer 612; the Bragg layer 620 includes the following Two reflective layers: the first acoustic impedance layer 624 adjacent to the lower surface of the CRF 700 , and the second acoustic impedance layer 622 adjacent to the first acoustic impedance layer 624 .

The Bragg layer 810 includes two reflective layers: a first acoustic impedance layer 812 adjacent to the upper surface of the CRF 700 , and a second acoustic impedance layer 814 adjacent to the first acoustic impedance layer 812 . The Bragg layer 820 includes two reflective layers: a first acoustic impedance layer 824 adjacent to the lower surface of the CRF 900 , and a second acoustic impedance layer 822 adjacent to the first acoustic impedance layer 824 .

In this embodiment, the characteristic acoustic impedance of the second acoustic wave impedance layer is higher than that of the first acoustic wave impedance layer, and the difference between the characteristic acoustic impedance of the second acoustic wave impedance layer and the first acoustic wave impedance layer is greater than or equal to 3.

Moreover, the value of the thickness of each reflective layer of the Bragg layer 610 is a quarter of the wavelength of the acoustic signal whose frequency is equal to the central frequency of the CRF500 in the acoustic material corresponding to the reflective layer, so that the Bragg layer 610 constitutes the acoustic wave confinement upper boundary of the CRF500 . The thickness of each reflective layer of the Bragg layer 620 is set to be a quarter of the wavelength of an acoustic signal with a frequency equal to the central frequency of the CRF700 in the acoustic material corresponding to the reflective layer, so that the Bragg layer 620 constitutes the lower boundary of acoustic confinement of the CRF700.

In addition, the value of the thickness of each reflective layer of the Bragg layer 810 is a quarter of the wavelength of the acoustic signal whose frequency is equal to the center frequency of the CRF700 in the acoustic material corresponding to the reflective layer, and the value of the thickness of each reflective layer of the Bragg layer 820 is The value is a quarter of the wavelength of the acoustic signal whose frequency is equal to the center frequency of CRF900 in the acoustic material corresponding to the reflective layer, so that the Bragg layer 810 and the Bragg layer 820 respectively constitute the upper boundary of the acoustic wave confinement of the CRF700 and the lower boundary of the acoustic wave confinement of the CRF900.

The multi-coupling filter in this embodiment includes CRF500 , CRF700 and CRF900 stacked adjacently, and a filter isolation layer 600 between CRF500 and CRF700 . The filter isolation layer 600 includes a Bragg layer 610 and a Bragg layer 620 whose reflection directions are facing away from each other. The value of the thickness of each reflection layer of the Bragg layer is: an acoustic signal with a frequency equal to the center frequency of the CRF adjacent to the Bragg layer corresponds to A quarter of the wavelength in the acoustic material, so that the Bragg layer 610 and the Bragg layer 620 respectively constitute the upper boundary of the acoustic confinement of the CRF500 and the lower boundary of the acoustic confinement of the CRF700, and the Bragg layer 810 and the Bragg layer 820 respectively constitute the upper boundary of the acoustic confinement of the CRF700 The sound waves of CRF900 and CRF900 limit the lower boundary, so that the sound waves of CRF500, CRF700 and CRF900 do not interfere with each other, and CRF500, CRF700 and CRF900 are stacked together without mutual influence, realizing the miniaturization and integration design of the filter module of the communication terminal.

The multi-coupling filter provided in the above embodiments includes at least two adjacent stacked coupling filters, and a filter isolation layer between the two adjacent stacked coupling filters; the filter isolation layer includes phase Two Bragg layers stacked adjacent to each other, and the reflection directions of the two Bragg layers are opposite to each other, so as to realize signal isolation between adjacent stacked coupling filters.

The CRFs in the above embodiments are connected in series. In practical applications, a series-parallel combination multi-coupling filter is required. Therefore, another embodiment of the present invention also provides a series-parallel combination multi-coupling filter, including at least two of the above-mentioned The multi-coupling filter provided in the embodiment, and the at least two multi-coupling filters provided in the above-mentioned embodiments are connected in parallel.

For ease of understanding, the above-mentioned series-parallel combination multi-coupling filter is described below with a specific embodiment, please refer to FIG. 4 , which is a schematic diagram of another embodiment of the multi-coupling filter in the embodiment of the present invention. The multi-coupling filter 4 in this embodiment includes:

The same two groups of adjacently stacked coupled filters, and the filter isolation layer between the adjacent two coupled filters, specifically, these two groups are:

One group is: adjacently stacked CRF204 and CRF304, and a filter isolation layer 404 between CRF204 and CRF304. The CRF204 is disposed below the CRF304, and the CRF204 is disposed on the substrate 1102;

The other group is: adjacently stacked CRF202 and CRF302, and a filter isolation layer 402 between CRF202 and CRF302. The CRF202 is disposed below the CRF302, and the CRF202 is disposed on the substrate 1102.

Among them, CRF204 and CRF202 are used for the receiving end of the US Cellular frequency band, the working frequency is 869MHz-894MHz, and the center frequency is 881.5MHz; CRF304 and 302 are used for the receiving end of the US PCS frequency band, the working frequency is 1930.5MHz-1989.5MHz, the center frequency 1990MHz.

CRF 204 includes FBAR 270 and FBAR 290 stacked adjacently, and acoustic coupling layer 280 between FBAR 270 and FBAR 290 .

FBAR 270 includes electrode 274 , electrode 272 , and piezoelectric film 276 between electrode 274 and electrode 272 . FBAR 290 includes electrode 294 , electrode 292 , and piezoelectric film 296 between electrode 294 and electrode 292 . Electrode 274 and electrode 272 serve as signal input terminals of CRF204 , and electrode 294 and electrode 292 serve as signal output terminals of CRF204 .

The acoustic coupling layer 280 is located between the electrode 274 of the FBAR 270 and the electrode 292 of the FBAR 290, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 280 The number and the thickness of each acoustic layer can adjust the coupling strength between FBAR270 and FBAR290.

CRF 304 includes adjacently stacked FBAR 370 and FBAR 390 , and acoustic coupling layer 380 between FBAR 370 and FBAR 390 .

FBAR 370 includes electrode 374 , electrode 372 , and piezoelectric film 376 between electrode 374 and electrode 372 , and FBAR 390 includes electrode 394 , electrode 392 , and piezoelectric film 396 between electrode 394 and electrode 392 . Electrode 374 and electrode 372 serve as signal input terminals of CRF304 , and electrode 394 and electrode 392 serve as signal output terminals of CRF304 .

The acoustic coupling layer 380 is located between the electrode 374 of the FBAR370 and the electrode 392 of the FBAR390, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 380 The number and thickness of each acoustic layer can adjust the coupling strength between FBAR370 and FBAR390.

CRF 202 includes FBAR 240 and FBAR 250 stacked adjacently, and acoustic coupling layer 260 between FBAR 240 and FBAR 250 .

FBAR 240 includes electrode 244 , electrode 242 , and piezoelectric film 246 between electrode 244 and electrode 242 . FBAR 250 includes electrode 254 , electrode 252 , and piezoelectric film 256 between electrode 254 and electrode 252 . Electrode 244 and electrode 242 serve as signal input terminals of CRF202 , and electrode 254 and electrode 252 serve as signal output terminals of CRF202 .

The acoustic coupling layer 260 is located between the electrode 244 of the FBAR240 and the electrode 252 of the FBAR250, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 260 The number and the thickness of each acoustic layer can adjust the coupling strength between FBAR240 and FBAR250.

CRF 302 includes adjacently stacked FBAR 340 and FBAR 350 , and acoustic coupling layer 360 between FBAR 340 and FBAR 350 .

The FBAR 340 includes an electrode 344 , an electrode 342 , and a piezoelectric film 346 between the electrode 344 and the electrode 342 . The FBAR 350 includes an electrode 354 , an electrode 352 , and a piezoelectric film 356 between the electrode 354 and the electrode 352 . Electrode 344 and electrode 342 serve as signal input terminals of CRF302 , and electrode 354 and electrode 352 serve as signal output terminals of CRF302 .

The acoustic coupling layer 360 is located between the electrode 344 of the FBAR340 and the electrode 352 of the FBAR350, and includes at least two acoustic layers (not shown) made of acoustic materials with different characteristic acoustic impedances. By adjusting the acoustic layers of the acoustic coupling layer 360 The number and thickness of each acoustic layer can adjust the coupling strength between FBAR340 and FBAR350.

Moreover, the electrode 372 of the FBAR370 is connected to the electrode 342 of the FBAR340 through the conductive metal 107, and the electrode 374 of the FBAR370 is connected to the electrode 344 of the FBAR340 through the conductive metal 108, so that the corresponding CRF304 and CRF302 are connected in parallel. The electrode 272 of the FBAR270 is connected to the electrode 242 of the FBAR240 through the conductive metal 105, and the electrode 274 of the FBAR270 is connected to the electrode 244 of the FBAR240 through the conductive metal 106, so that the corresponding CRF204 and CRF202 are connected in parallel. It can be understood that other existing known technologies can also be used to connect CRF304 and CRF302 in parallel, and CRF204 and CRF202 in parallel, so as to improve the out-of-band rejection capability of the multi-coupling filter 4 .

In each FBAR of CRF204 and 202, each electrode is made of gold, the thickness of each electrode is 0.25 microns, and the area is 385*385 square microns; each piezoelectric film is made of aluminum nitride, and the thickness of each piezoelectric film is 3.94 microns . In each FBAR of CRF304 and 302, each electrode is made of aluminum, the thickness of each electrode is 0.1 microns, and the area is 213*213 square microns; each piezoelectric film is made of aluminum nitride, and the thickness of each piezoelectric film is 2.691 microns .

By adjusting the number of layers of the acoustic coupling layer 280 and the acoustic coupling layer 260 and the thickness of each acoustic layer, the bandwidth of the lower CRF204, 202 can meet the requirements of the Cellular frequency band; The number of acoustic layers and the thickness of each acoustic layer can make the bandwidth of the lower CRFs 304 and 302 meet the requirements of the PCS frequency band.

The filter isolation layer 404 includes a Bragg layer 450 and a Bragg layer 460 stacked adjacently. The reflection directions of the Bragg layer 450 and the Bragg layer 460 are facing away from each other. Specifically, the Bragg layer 450 includes the following four reflective layers: a first acoustic wave impedance layer 452 adjacent to the electrode 294 of the FBAR 290 , and a first acoustic wave impedance layer 452 adjacent to the first acoustic wave impedance layer 452. The second acoustic impedance layer 454, the first acoustic impedance layer 456 adjacent to the second acoustic impedance layer 454, and the second acoustic impedance layer 458 adjacent to the first acoustic impedance layer 456; the Bragg layer 460 includes the following four layers Reflective layer: first acoustic impedance layer 468 adjacent to electrode 372 of FBAR 370 , second acoustic impedance layer 466 adjacent to first acoustic impedance layer 468 , first acoustic impedance layer adjacent to second acoustic impedance layer 466 464, and the second acoustic wave impedance layer 462 adjacent to the first acoustic wave impedance layer 464.

The filter isolation layer 402 includes a Bragg layer 430 and a Bragg layer 440 stacked adjacently. The reflection directions of the Bragg layer 430 and the Bragg layer 440 are facing away. Specifically, the Bragg layer 430 includes the following four reflection layers: the first acoustic wave impedance layer 432 adjacent to the electrode 254 of the FBAR250, the first acoustic wave impedance layer 432 adjacent to the first acoustic wave impedance layer 432 The second acoustic impedance layer 434, the first acoustic impedance layer 436 adjacent to the second acoustic impedance layer 434, and the second acoustic impedance layer 438 adjacent to the first acoustic impedance layer 436; the Bragg layer 440 includes the following four layers Reflective layer: first acoustic impedance layer 448 adjacent to electrode 342 of FBAR 340 , second acoustic impedance layer 446 adjacent to first acoustic impedance layer 448 , first acoustic impedance layer adjacent to second acoustic impedance layer 446 444, and the second acoustic wave impedance layer 442 adjacent to the first acoustic wave impedance layer 444.

In this embodiment, the first acoustic wave impedance layer in the Bragg layer of the filter isolation layer 404 and the filter isolation layer 402 is made of silicon dioxide, the characteristic acoustic impedance is 12.5 Mray1, and the sound velocity of longitudinal waves is 6253 m/s; The acoustic wave impedance layer is made of tungsten, the characteristic acoustic impedance is 105.6Mray1, and the longitudinal sound velocity is 5501m/s.

For the Bragg layer 450 of the filter isolation layer 404 and the Bragg layer 430 of the filter isolation layer 402, the thickness of each reflective layer is equal to the wavelength of the acoustic signal of the center frequency 881.5 MHz of the CRF204 and CRF202 in the acoustic material corresponding to the reflective layer. a quarter. Specifically, the thickness of the first acoustic impedance layer of the Bragg layer 450 and the Bragg layer 430 is 1.774 microns, which is 1.774 micrometers of the wavelength of the acoustic signal with a frequency equal to 881.5 MHz in silicon dioxide; the Bragg layer 450 and the Bragg layer 430 The thickness of the second acoustic impedance layer is 1.561 μm, which is a quarter of the wavelength of the acoustic signal in tungsten with a frequency equal to 881.5 MHz.

For the Bragg layer 460 of the filter isolation layer 404 and the Bragg layer 440 of the filter isolation layer 402, the thickness of each reflective layer is four times the wavelength of an acoustic signal with a frequency equal to the center frequency 1990 MHz of CRF304 and CRF302 in the acoustic material corresponding to the reflective layer. one-third. Specifically, the thickness of the first acoustic wave impedance layer of the Bragg layer 460 and the Bragg layer 440 is 0.797 microns, which is a quarter of the wavelength of the acoustic signal in silicon dioxide with a frequency equal to 1990 MHz; The thickness of the second acoustic wave impedance layer is 0.701 μm, which is a quarter of the wavelength of an acoustic signal with a frequency equal to 1990 MHz in tungsten.

Please combine Fig. 5 to Fig. 7, Fig. 5, Fig. 6 and Fig. 7 respectively show the frequency response diagram obtained by the simulation of the multi-coupling filter in the embodiment shown in Fig. 4, and the frequency response diagram of the receiving band of the Cellular frequency band in Fig. 5 110 and the frequency response diagram 112 of the PCS band receive band in FIG. 5 .

Please refer to Fig. 5, the abscissa in Fig. 5 is the frequency, the unit is gigahertz, and the ordinate is the insertion loss, the unit is decibel. It can be known from FIG. 5 that the filtering performance of the parallel connection of CRF204 and CRF202 and the parallel connection of CRF304 and CRF302 is not affected by each other.

Please refer to Fig. 6, the abscissa in Fig. 6 is the frequency, the unit is gigahertz, and the ordinate is the insertion loss, the unit is decibel. It can be obtained from Figure 6 that the maximum insertion loss of the parallel connection CRF204 and CRF202 is 1.505dB, and the 3dB bandwidth is 34MHz, and the minimum suppression of the parallel connection CRF204 and CRF202 on the cellular transmission frequency band 824MHz-849MHz is 30.451dB.

Please refer to Fig. 7, the abscissa in Fig. 7 is the frequency, the unit is gigahertz, and the ordinate is the insertion loss, the unit is decibel. It can be obtained from Figure 7 that the maximum insertion loss of the parallel CRF304 and CRF302 is 1.073dB, and the 3dB bandwidth is 66MHz, and the minimum suppression of the parallel connection of CRF304 and CRF302 to the PCS transmission frequency band 1850MHz-1910MHz is 21.892dB.

The multi-coupling filter 4 of the present embodiment has the same two groups of two adjacent stacked CRFs, and a filter isolation layer between two adjacent CRFs; and, the two groups corresponding to the positions CRFs are connected in parallel. It can be understood that the multi-coupling filter may also include the same at least two groups of two adjacent stacked CRFs, and a filter isolation layer between two adjacent CRFs, and the positions of each group are the same. The corresponding CRFs are connected in parallel.

In this embodiment, since the upper and lower Bragg layers in the filter isolation layer 402 respectively constitute the acoustic wave limit lower boundary of the CRF302 adjacent to the upper surface of the filter isolation layer 402, and the acoustic wave of the CRF202 adjacent to the filter isolation layer 402 lower surface limit the upper boundary, so that CRF202 and CRF302 are stacked together and do not affect each other; and because the upper and lower Bragg layers in the filter isolation layer 404 respectively constitute the acoustic wave limit lower boundary of the CRF304 adjacent to the filter isolation layer 404 upper surface, and The acoustic wave confinement upper boundary of the CRF204 adjacent to the lower surface of the filter isolation layer 404 makes the CRF202 and the CRF302 stack together without affecting each other, so that the filtering performance of the parallel connection of the CRF204 and CRF202 and the parallel connection of the CRF304 and CRF302 is not affected by each other. Influence, the miniaturization and integrated design of the filter module of the communication terminal are realized.

The multi-coupling filter provided by the embodiment of the present invention has been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The description of the above embodiment is only used to help understand the core of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary, the content of this specification should not be construed as limiting the present invention.

Claims (6)

1. A multi-coupling filter, comprising: at least two adjacent stacked coupling filters, and a filter isolation layer between the two adjacent stacked coupling filters; The filter isolation layer includes two Bragg layers stacked adjacently, and the reflection directions of the two Bragg layers are facing away, so as to realize the isolation of signals between the adjacently stacked coupled filters; Wherein, the coupled filter includes two adjacent stacked thin film bulk acoustic resonators, and an acoustic coupling layer located between the two adjacent stacked thin film bulk acoustic resonators. 2. The multi-coupling filter according to claim 1, wherein the Bragg layer comprises at least two reflective layers made of acoustic materials with different acoustic impedances. 3. The multi-coupling filter according to claim 2, characterized in that: The value range of the thickness of the reflective layer is [n*85%, n*115%], n is a frequency equal to a quarter of the wavelength of the acoustic signal of the first frequency in the acoustic material corresponding to the reflective layer an odd multiple, the first frequency is the center frequency of the coupled filter adjacent to the Bragg layer. 4. The multi-coupling filter according to claim 2, characterized in that: the value of the thickness of each reflective layer of the Bragg layer is equal to the acoustic signal of the first frequency in the acoustic material corresponding to the reflective layer a quarter of the wavelength. 5. The multi-coupling filter according to claim 2, characterized in that: The Bragg layer includes a first acoustic impedance layer and a second acoustic impedance layer, and the difference between the characteristic acoustic impedances of the second acoustic impedance layer and the first acoustic impedance layer is greater than or equal to 3. 6. A series-parallel combined multi-coupling filter, characterized in that it comprises at least two multi-coupling filters according to any one of claims 1 to 5, and the multi-coupling filters are connected in parallel.

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