TW202147775A - Frequency filter - Google Patents

Abstract

Provided is a frequency filter using a piezoelectric thin film, the frequency filter being able to perform frequency-filtering on high-frequency power of bulk power handled in a base station of a mobile phone. The frequency filter 10 comprises: a laminate 11 in which first layers 111 and second layers 112 are alternately laminated one by one in a prescribed number of layers, each first layer 111 being a piezoelectric layer made from a first piezoelectric material and having polarization directed along one prescribed direction, and each second layer 112 being a piezoelectric layer made from a second piezoelectric material and having polarization, of which a component is vertical or parallel to the first layer 111 and is directed along a direction different from that of the polarization of the first layer 111 by 180 DEG, wherein the thickness d1 of the first layer 111 and the thickness d2 of the second layer 112 are within a range of 0.5*(v2/v1) d1 ≤ d2 ≤ 2.0*(v2/v1)d1, where v1 denotes a sound velocity in the first layer 111 and v2 denotes a sound velocity in the second layer 112; and a pair of electrodes (a first electrode 121 and a second electrode 122) provided with the laminate 11 interposed therebetween in the lamination direction, wherein the prescribed number is set to have electric power resistance to high-frequency power of 10W.

Description

frequency filter

The present invention relates to a frequency filter for frequency filtering of high frequency power used in base stations of mobile phones and the like. Here, "high-frequency power" and the following "high-frequency voltage" refer to the power and voltage of the high-frequency signal obtained by receiving electromagnetic waves and/or the high-frequency signal used when transmitting electromagnetic waves, respectively. Typically, the frequency of such high frequency power and high frequency voltage is included in the range of 50 MHz to 30 GHz.

For mobile phone service, multiple base stations are installed in the city to send and receive radio waves to and from mobile phone terminals. In either of the terminal and the base station, a specific frequency is extracted from a plurality of frequencies included in the electromagnetic waves received by the antenna to generate high-frequency power having the specific frequency.

Regarding terminals, conventionally, high-frequency power having a specific frequency is extracted by passing electromagnetic waves having a plurality of frequencies received by an antenna through a high-frequency power frequency filter. As such a frequency filter for high-frequency power, a surface acoustic wave (SAW) filter provided in such a manner that a pair of comb-shaped electrodes are engaged with the surface of a piezoelectric thin film, a piezoelectric A pair of electrode bulk acoustic wave (BAW) filters are provided on both surfaces of the film (for example, refer to Patent Document 1). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2012-049758 [Patent Document 2] Japanese Patent Laid-Open No. 2020-072284

[The problem to be solved by the invention]

In a SAW filter or a BAW filter, the withstand voltage between electrodes is low, and the frequency filtering of high-power high-frequency power that must be processed by the base station cannot be performed. Therefore, in the past, the base station of the mobile phone used a cavity resonator for frequency filtering. However, while the SAW filter or the BAW filter can be miniaturized to several millimeters square, the cavity resonator has a size of several hundreds of millimeters, and it is difficult to miniaturize it. In recent years, it has become increasingly required to install small base stations in urban areas where electromagnetic waves from large-scale base stations are difficult to reach, such as places that are shaded by buildings. However, if a cavity resonator is used in such a small base station, the following problems will occur. The problem is that the occupied space of the base station increases, and the installation cost increases.

The problem to be solved by the present invention is to provide a frequency filter which can be miniaturized, uses a piezoelectric thin film, and can perform frequency filtering of high-power high-frequency power processed by a base station of a mobile phone. [Technical means to solve the problem]

The frequency filter of the present invention accomplished to solve the above-mentioned problems includes: a) a layered body formed by alternately repeating the first layer and the second layer layer by layer and adding a predetermined number of layers, wherein the first layer is The piezoelectric layer made of the first piezoelectric material is polarized in a predetermined direction, and the second layer is made of the second piezoelectric material and the component of the polarization in the direction perpendicular or parallel to the first layer is oriented in the same direction as the first layer. The polarization of the first layer is composed of a piezoelectric layer in a direction in which the components in the above-mentioned directions differ by 180°, or a non-piezoelectric layer made of a non-piezoelectric insulating material, using the speed of sound v _{1 in} the first layer and the The speed of sound v ₂ in the second layer, the thickness d ₁ of the first layer and the thickness d ₂ of the second layer are 0.5×(v ₂ /v ₁ )d ₁ ≦d ₂ ≦2.0×(v ₂ /v ₁ ) _{within the range of d 1} ; and b) 1 pair of electrodes, which are arranged so as to sandwich the above-mentioned laminated body in the lamination direction; characterized in that: are set in such a way as to have power resistance to a high frequency power of 10 W the above-established quantities.

In the frequency filter of the present invention, if high-frequency power including multiple frequencies is input between a pair of electrodes, high-frequency power and high-frequency voltage including these frequencies are generated between the electrodes. In this way, each of the first layers arranged every other layer among the layers constituting the laminated body is caused by the piezoelectric effect at a plurality of specific frequencies determined _{by the thickness d 1} and the speed of sound v _{1 among the above-mentioned plurality of frequencies,} Vibrates with the same phase at each frequency.

On the other hand, the second layer vibrates as follows in the case of being composed of the piezoelectric layer and the case of being composed of the non-piezoelectric layer, respectively.

When the second layer is composed of a piezoelectric layer, the piezoelectric effect vibrates at a plurality of specific frequencies determined _{by the thickness d 2} and the speed of sound v _{2 among the above-mentioned plurality of frequencies.} Here, d ₂ has a value of (v ₂ /v ₁ ) d ₁ or a value close to it (0.5 to 2.0 times), whereby each second layer operates at a plurality of frequencies specified above (that is, the same frequency as the first layer) frequency), vibrate with the same phase at each frequency. Also, the component of the polarization in the direction perpendicular or parallel to the first layer is oriented in a direction that differs by 180° from the component in the above-mentioned direction in the polarization of the first layer, whereby with respect to the vibration direction of the first layer, the The phase of vibration becomes the opposite phase to that of the first layer (180° difference). As a result, the vibrations of the first layer and the second layer complement each other, and the entire layered body generates a plurality of wave numbers each of which is a half-integer number and the above-mentioned specific plurality of frequencies corresponding to the plurality of wave numbers. resonance.

When the second layer is composed of a non-piezoelectric layer, although the second layer does not generate vibration caused by the piezoelectric effect, but receives vibration from the first layer, the second layer has the same specific characteristics as the first layer. Vibrates at multiple frequencies. d ₂ has (v ₂ /v ₁ ) d ₁ or a value close to it (0.5 to 2.0 times), whereby the vibration with the frequency of the first layer satisfies the resonance condition of the second layer. As a result, as in the case where the second layer is constituted by the piezoelectric layer, resonance having the above-mentioned specific plurality of frequencies is generated in the entire laminate, and the above-mentioned specific plurality of frequencies is as much as a half-integer per layer. corresponding wave number.

As described above, in either the case of a piezoelectric layer or a non-piezoelectric layer, when a high-frequency power having a plurality of frequencies is input, the laminated body is at the plurality of frequencies. Resonates at a specified number of frequencies. As a result, only the high-frequency power having the above-mentioned specific plurality of frequencies is amplified, so that the present invention functions as a frequency filter of the high-frequency power.

In the present invention, the larger the total number of the first layer and the second layer (the above-mentioned predetermined number), the thicker the insulator (piezoelectric or non-piezoelectric insulator) between the electrodes becomes, so that the thickness of the insulator (piezoelectric or non-piezoelectric insulator) between the electrodes becomes thicker. High-power high-frequency power for frequency filtering. In the field of mobile phones, the output of electromagnetic waves to be transmitted is about 1 W at the maximum at the terminal, and 10 to 100 W at the base station (see, for example, Patent Document 2). Therefore, in the frequency filter of the present invention, the above-mentioned predetermined number, that is, the total layer of the first layer and the second layer, is set so that the frequency filter has a power resistance of 10 W (or more) corresponding to the output of electromagnetic waves. number. The higher the number of layers, the higher the power resistance. In addition, the frequency of filtering is determined by the thickness of each layer, so even if the number of layers is increased, it has no effect.

Generally speaking, the power resistance is determined by considering the deterioration during use and assuming that a predetermined power is continuously input for a fixed period. When the frequency filter of the present invention is used in a base station of a mobile phone, the predetermined period is set to at least 3 years.

When the second piezoelectric material is used as the material of the second layer, the second piezoelectric material and the first piezoelectric material may be the same material or different materials. In addition, when the above-mentioned non-piezoelectric insulating material is used as the material of the second layer, the insulating material may be a layer composed of an insulating material that is not a piezoelectric body, or may be the following material, although the material may be Piezoelectricity is generated, but piezoelectricity is not generated in the entire second layer because the polarization is oriented in random directions in the second layer.

When the above-mentioned second layer is composed of a non-piezoelectric layer, different from the case of a piezoelectric layer, there is no need to adjust the relationship between the polarization directions of the first layer 211 and the second layer 212 during production, so it can be It is easier to fabricate than in the case of piezoelectric layers.

Preferably, the frequency filter of the present invention further includes an acoustic Bragg reflector on one side of the pair of electrodes. Acoustic Bragg reflectors are formed by alternately laminating two types of layers with different acoustic impedances. By predetermining the thickness of each layer of the acoustic Bragg reflector so as to generate Bragg reflection of sound waves having the frequency of the vibration generated in the laminate, the leakage of the vibration energy of the laminate to the outside can be suppressed.

Furthermore, it is not limited to the application of the base station of the mobile phone, and for other applications, it has not been known until now that there is a first layer as a piezoelectric layer and a non-piezoelectric layer made of a non-piezoelectric insulating material. A frequency filter of a laminated body formed by alternately laminating the second layers one by one. By using the non-piezoelectric layer as the second layer in this way, it is not necessary to control so as to generate polarization in a predetermined direction in the second layer at the time of production, so that the laminated body can be easily produced. In this case, even if the power resistance is lower than that required for a frequency filter for a base station of a mobile phone, it can be used as a frequency filter for other purposes. Taking these aspects into consideration, another aspect of the frequency filter of the present invention is characterized by comprising: a) a laminated body, which is formed by alternately repeating the first layer and the second layer layer by layer and adding up a predetermined number of layers The first layer is a piezoelectric layer made of a first piezoelectric material, and the polarization is oriented in a predetermined direction, and the second layer is a non-piezoelectric layer made of a non-piezoelectric insulating material. The speed of sound v ₁ in the first layer and the speed of sound v ₂ in the second layer, the thickness d ₁ of the first layer and the thickness d ₂ of the second layer are 0.5×(v ₂ /v ₁ )d ₁ ≦d ₂ ≤ 2.0×(v ₂ /v ₁ )d ₁ ; and b) 1 pair of electrodes, which are arranged so as to sandwich the above-mentioned laminate in the lamination direction. Here, the above-mentioned predetermined one direction may be set to any direction. [Effect of invention]

By means of the present invention, a frequency filter can be obtained which can perform frequency filtering of high-frequency high-frequency power processed by a base station of a mobile phone and uses a piezoelectric thin film.

An embodiment of a frequency filter (hereinafter, simply referred to as a "frequency filter") for a base station of a mobile phone according to the present invention will be described with reference to FIGS. 1 to 9 .

(1) Frequency filter of the first embodiment (1-1) Configuration of the frequency filter of the first embodiment FIG. 1 shows the configuration of the frequency filter 10 according to the first embodiment. The frequency filter 10 has a layered body 11 in which the first layer 111 and the second layer 112 are alternately repeated layer by layer to accumulate a predetermined number of layers, and the layered body 11 is stacked in a direction (upper and lower direction in FIG. 1 ). The first electrode 121 and the second electrode 122 are provided so as to sandwich the laminate 11 .

The first layer 111 is made of a piezoelectric material. In this embodiment, the second layer 112 is also made of a piezoelectric material. The piezoelectric material of the first layer 111 is referred to as a first piezoelectric material, and the piezoelectric material of the second layer 112 is referred to as a second piezoelectric material. The first piezoelectric material and the second piezoelectric material may be the same piezoelectric material, or may be mutually different piezoelectric materials. For the first piezoelectric material and the second piezoelectric material, various piezoelectric materials can be used, such as zinc oxide (ZnO), aluminum nitride (AlN), and a part of Al (aluminum) in aluminum nitride is replaced by Sc ( Scandium) AlScN (Al _1-x Sc _x N, 0<x<1), (Zn,Mg)O or (Zn,Ca)O doped with Mg or Ca in zinc oxide, lead titanate (PbTiO _{3 : PTO), lead zirconate titanate (PbTi 1-x} Zr _x O ₃ : PZT) in which a part of Ti (titanium) in lead titanate is partially replaced by Zr (zirconium).

The first layer 111 and the second layer 112 have polarizations in the directions described below, respectively.

The polarization direction P ₁ of the first layer 1111 may be perpendicular to the first layer 111 can also be parallel to the first layer 111 and thus also relative to the first layer 1111 is inclined (i.e., towards the direction neither parallel nor perpendicular ).

Respect to the direction of polarization P ₂ of the second layer 112. The polarization component P ₂ of the first layer and the second layer 111 of 2112 parallel (parallel component) _// P ₂ becomes the first polarization layer 111 of P the parallel component ₁ P _{1 //} direction difference of 180 ° (see FIG. 2), or the polarization component P ₂ of the first layer and the second layer 111 of 2112 perpendicular (vertical component) P ₂ becomes the first layer 1 _⊥ The vertical component P _{1 ⊥} of the polarization P ₁ of 111 differs in the direction of 180°. Furthermore, FIGS. 1 and 2 show examples in which the polarizations P ₁ and P _{2 are both} inclined (neither parallel nor perpendicular) with respect to the first layer 111 and the second layer 112 , but the polarizations P ₁ and/or P ₂ can be parallel to the first layer 111 and the second layer 112 , and the polarizations P ₁ and/or P ₂ can also be perpendicular to the first layer 111 and the second layer 112 .

_{The thickness d 2 of} the second layer 112 is set within the range of 0.5×(v ₂ /v ₁ ) times to 2.0×(v ₂ /v ₁ )d ₁ times the _{thickness d 1} of the first layer 111 . Here, v ₁ is the speed of sound in the first layer 111 , and v ₂ is the speed of sound in the second layer 112 . When the first layer 111 and the second layer 112 are made of the same piezoelectric material, usually v ₁ =v ₂ , so d _{2 only needs} to be 0.5 times to 2.0 times of _{d 1 . Typically,} The first layer 111 and the second layer 112 may have the same thickness.

The first layer 111 and the second layer 112 are alternately repeated layer by layer as described above to accumulate a predetermined number of layers. The higher the number of layers, the higher the power resistance. Therefore, in the frequency filter 10, in order to ensure the power resistance of a frequency filter used as a base station of a mobile phone, the first frequency filter 10 is determined so as to have a power resistance within the range of 10 to 100 W as an upper limit value. The number of laminated layers of the layer 111 and the second layer 112 . Satisfaction of such power resistance can be confirmed by performing simulations or preliminary experiments.

In order to sufficiently ensure the power resistance of 10 W (or more), the number of layers of the layered body 11 is preferably larger, but if it is too large, it will take time and effort to manufacture, so it can be appropriately determined in consideration of these factors.

The first electrode 121 and the second electrode 122 correspond to the above-described pair of electrodes. The materials of the first electrode 121 and the second electrode 122 are not particularly required as long as they have conductivity.

(1-2) Manufacturing method of the frequency filter of the first embodiment 3 and 4, the manufacturing method of the frequency filter 10 of 1st Embodiment is demonstrated. The magnetron sputtering apparatus 30 used to manufacture the frequency filter 10 is shown in FIG. 3 . The magnetron sputtering apparatus 30 has a vacuum vessel 31 whose interior is evacuated by a vacuum pump (not shown). Inside the vacuum container 31 , a magnetron electrode 32 and a substrate holder 33 inclined with respect to the upper surface of the magnetron electrode 32 are provided. The plate-shaped target T which becomes the material of each layer of the frequency filter 10 is placed on the upper surface of the magnetron electrode 32 . The high-frequency power supply 34 is connected to the magnetron electrode 32 via a matching box 341 . The substrate holder 33 is formed of a plate-shaped conductor and is grounded. One end of the substrate holder 33 is provided with a cooling mechanism 35 for cooling the one end of the substrate holder 33 by cooling water.

When a gas is used as the material of the first layer 111 and/or the second layer 112 together with the target, a gas inlet (not shown) is provided in the vacuum container 31 . For example, when fabricating the first layer 111 and/or the second layer 112 made of AlN or AlScN, an Al target or a Sc target is used, and nitrogen gas is introduced into the vacuum chamber 31 from a gas inlet during fabrication.

When manufacturing the frequency filter 10 , first, the substrate S is mounted on the substrate holder 33 , and the target TM made of metal is placed on the upper surface of the magnetron electrode 32 . The target TM is sputtered in this state, whereby the first electrode 121 is formed on the surface of the substrate S ( FIG. 4( a )).

Next, the target T1 serving as the material of the first layer 111 is placed on the upper surface of the magnetron electrode 32 . In this state, one end of the substrate holder 33 is cooled by the cooling mechanism 35, and the target T1 is sputtered to form a first layer 111 on the surface of the substrate S ( FIG. 4( b )). At this time, when the substrate holder 33 is inclined with respect to the upper surface of the magnetron electrode 32 and one end of the substrate holder 33 is cooled by the cooling mechanism 35, a temperature gradient is generated in the surface of the substrate S, whereby the first layer 111 The polarization P ₁ is inclined with respect to the first layer 111 .

Next, the substrate S is temporarily removed from the substrate holder 33 , and the substrate S is rotated 180° about its normal line as an axis, and then mounted on the substrate holder 33 again ( FIG. 4( c )). At the same time, the target T2 to be the material of the second layer 112 is placed on the upper surface of the magnetron electrode 32 . In this state, one end of the substrate holder 33 is cooled by the cooling mechanism 35, and the target T2 is sputtered to form one second layer 112 on the surface of the first layer 111 (FIG. 4(d)). At this time, as described above by rotating the substrate S, and when the first layer 111 generates the same manner as the substrate holder and the substrate holder 33 is inclined 33 one end by a cooling means 35 was cooled, the polarization P ₂ of the second layer 2112 toward a direction inclined with respect to the second layer 112 and the second layer of the parallel polarization component P 112 ₂ become opposite to the direction of polarization P of the first layer 1111 _1.

After that, the following operations are repeated, that is, the next first layer 111 is formed on the second layer 112 by the same method as the first first layer 111, and the first layer 111 is formed on the first layer 111 by the same method as the first layer 111. The next second layer 112 is fabricated in the same manner as the first second layer 112 . Thereby, a predetermined number of the first layer 111 and the second layer 112 are each produced ( FIG. 4( e )).

Finally, the target TM made of metal is placed on the upper surface of the magnetron electrode 32, and the target TM is sputtered in this state, whereby the last layer of the first layer 111 and the second layer 112 on the substrate S is formed. The second electrode 122 is fabricated on the fabricated layer ( FIG. 4( f )). After that, the substrate S is removed as necessary (the state where the substrate S remains) is also required, thereby completing the frequency filter 10 .

(1-3) Operation of the frequency filter of the first embodiment In the frequency filter 10 of the first embodiment, when a high-frequency power including a plurality of frequencies is input between the first electrode 121 and the second electrode 122, the frequency filter 10 includes the plurality of frequencies and the magnitude is the same as the high frequency between the electrodes. The high frequency voltage corresponding to the magnitude of the frequency power. As a result, high-frequency voltages including these multiple frequencies are also applied in the thickness direction to each of the first layers 111 and each of the second layers 112 included in the layered body 11 (in addition, the sum of the voltages applied to the layers corresponds to voltage between the first electrode 121 and the second electrode 122).

Therefore, each first layer 111 uses the piezoelectric effect to operate at the same frequency at each frequency at specific frequencies determined by _{the thickness d 1 of the} first layer 111 and the speed of sound v _{1 among the above-mentioned multiple frequencies.} phase vibration. At this time, the polarizations P _{1 of} the first layers 111 are oriented in the same direction, whereby the first layers 111 vibrate in the same direction. On the other hand, each second layer 112 vibrates at a plurality of specific frequencies determined by _{the thickness d 2 of} the second layer 112 and the speed of sound v _{2 by the piezoelectric effect.} Regarding the phase of vibration, the direction of the parallel component P _{2 // of the polarization P 2} of the second layer 112 (the second direction) and the direction of the parallel component P _{1 //} of _{the polarization P 1 of the first layer 111 (the first direction)} direction) differs by 180°, whereby the second layer 112 vibrates in an opposite phase to that of the first layer 111 . Further, by d ₁ in D ₂ of _{0.5 × (v 2 / v 1} ) times of _{~ 2.0 × (v 2 / v} 1) times in the range of d _1, the first layer 111 to the same specific layer 2 of It vibrates at multiple frequencies and becomes a resonance state. The specific frequencies correspond to the wave numbers which are half-integers per layer.

As a result of the formation of such a resonance state, only the high-frequency power having the above-mentioned specified plurality of frequencies is amplified. Therefore, the invention of the first embodiment functions as a frequency filter.

Regarding the frequency filter 10 of the first embodiment, the number of layers of the first layer 111 and the second layer 112 can be determined so as to have power resistance related to a predetermined power in the range of 10 to 100 W. The output corresponding to this power is used by the base station of the mobile phone.

(1-4) Modification of the frequency filter of the first embodiment FIG. 5 shows a frequency filter 10A as a modification of the first embodiment. In this frequency filter 10A, an acoustic Bragg reflector 13 is provided on the surface of the first electrode 121 of the frequency filter 10 of the first embodiment on the opposite side to the laminate 11 . The acoustic Bragg reflector 13 is formed by alternately laminating two types of layers 131 and 132 having different acoustic impedances. The thicknesses of the layers 131 and 132 are determined according to the materials of the layers 131 and 132 so as to generate Bragg reflection of sound waves having the frequency of vibration of the laminated body 11 . By providing such an acoustic Bragg reflector 13, it is possible to suppress the leakage of the energy of the vibration of the laminated body 11 to the outside.

(1-5) Experiments and calculation results of the frequency filter of the first embodiment Next, the results of experiments and calculations of the frequency filter of the first embodiment will be described. In the experiment, the substrate made of quartz glass for production supports the frequency filter 10 of the first embodiment and the frequency filter 10A of the modification example (that is, the acoustic Bragg reflector 13 is provided). In the produced frequency filters 10 and 10A, the layered body 11 was used in which the first layer 111 and the second layer 112 were each layered by 6 layers, and a total of 12 layers were layered. For the materials of the first layer 111 and the second layer 112, Sc _0.43 Al _0.57 N (ScAlN, x=0.43) was used. The first layer 1111 and _second layer thickness d of the thickness d ₂ of the 2112 target value of 5 μm are produced, but the measured thickness of the overall laminate 11 of 52 μm is obtained, so that the actual d ₁ and d ₂ was about 4.3 (52/12) μm on an average. In addition, in the calculation, _{the values of d 1} and d _{2 were} set to 5 μm. The target values of d ₁ and d ₂ in the experiment and the value "5 μm" used in the calculation are determined in such a way that the frequency filter 10A functions in the frequency region centered at 400 MHz. The acoustic Bragg reflector 13 is fabricated in such a way as to generate the Bragg reflection of sound waves with a frequency of 400 MHz.

The following experiments were performed on the fabricated frequency filter 10 . A high-frequency electric field is applied between the first electrode 121 and the second electrode 122 . The high-frequency electric field is converted into mechanical vibration by the inverse piezoelectric effect in the laminate 11 . The mechanical vibration is reflected on the bottom surface of the quartz glass substrate, and is converted into a high-frequency voltage by the piezoelectric effect in the laminated body 11 . In this experiment, the high-frequency voltage was measured, and the insertion loss was calculated based on the obtained high-frequency voltage. In addition, by subtracting the mechanical loss generated in the quartz glass substrate from the obtained insertion loss, the conversion loss, which is the efficiency of electromechanical conversion by the piezoelectric effect, is obtained. Furthermore, the equivalent circuit model was used to construct the same structure as the experiment, and the theoretical conversion loss was obtained by calculation. The results of these experiments and calculations are shown in FIG. 6 . These experimental and calculation results imply that the down-conversion loss is reduced at a number of frequencies including around 400 MHz (0.4 GHz), functioning as a frequency filter.

In FIG. 7, the result obtained by measuring the (electrical) impedance of the produced frequency filter 10A is shown together with the calculation result. Both the experimental value and the calculated value obtain an impedance of over 200 Ω at a frequency near 400 MHz, so that the frequency filter 10A has sufficient power resistance.

Here, in order to simplify the experiment, the frequency is set to 400 MHz, which is a relatively small value, but by making the thicknesses of the first layer 111 and the second layer 112 thinner, the first layer 111 and the second layer 112 are made thinner. The number of layers of layer 111 and layer 2 112 can obtain frequency filters that can be used even in higher frequency bands (eg, 3.5 GHz band or 4.5 GHz band) used by base stations of mobile phones.

In FIG. 8 , the conversion is obtained by experiment and calculation when the total number of layers of the first layer 111 and the second layer 112 is (a) 8 layers, (b) 4 layers, and (c) 2 layers in a graph. result of loss. The thickness of each layer is the same as in the case of 12 layers in FIGS. 6 and 7 showing the experimental and calculation results (target values in terms of experiments). The same experiments and calculations are also performed for the case where the first layer 111 is only one layer and there is no second layer 112 (not included in the present invention) ( FIG. 8( a )) for reference. It can be seen that the smaller the total number of layers of the first layer 111 and the second layer 112, the less the position in the graph where the conversion efficiency is extremely small, but there is a minimum value at the position around 400 MHz on the horizontal axis. It operates at frequencies around MHz. However, when the number of layers is reduced, the power resistance is lowered. Therefore, the total number of layers of the first layer 111 and the second layer 112 can be determined by comprehensively considering power resistance and cost (the higher the number of layers, the greater the increase).

(2) Frequency filter of the second embodiment FIG. 9 shows the configuration of the frequency filter 20 according to the second embodiment. The frequency filter 20 has a layered body 21 in which the first layer 211 and the second layer 212 are alternately repeated layer by layer to accumulate a predetermined number of layers, and the layered body 21 is provided so as to sandwich the layered body 21 in the layering direction of the layered body 21 . the first electrode 221 and the second electrode 222 . The first electrode 221 and the second electrode 222 in these respective components are the same as the first electrode 121 and the second electrode 122 in the frequency filter 10 of the first embodiment, respectively.

In the second embodiment, as the second layer 212, a non-piezoelectric layer made of a non-piezoelectric insulating material is used. As such a non-piezoelectric insulating material, a dielectric material having no piezoelectricity such as _{SiO 2 is typically exemplified.} In addition, the following materials can also be used as the material of the second layer 212 . Although the material can generate piezoelectricity, it will not generate piezoelectricity as a whole because the polarization is oriented in random directions in the second layer 212 .

For the first layer 211, a material composed of a piezoelectric body is used. Regarding the polarization direction of the first layers 211 , each first layer 211 may be in any direction as long as it is the same direction. Therefore, the polarization direction of the first layer 211 can be perpendicular to the first layer 211 , can also be parallel to the first layer 211 , and can also be inclined (neither vertical nor parallel) with respect to the first layer 211 .

Furthermore, in the example shown in FIG. 9 , the layer closest to the first electrode 221 among the layers in the laminate 21 is referred to as the first layer (piezoelectric layer) 211 , but this layer may be referred to as the first layer. A structure of two layers (non-piezoelectric layers) 212 (therefore, the first layer 211 and the second layer 212 in the example shown in FIG. 9 are exchanged for the entire laminated body 21 ).

As in the case of the first embodiment, _{the thickness d 2 of} the second layer 212 is set to be 0.5×(v ₂ /v ₁ ) times to 2.0×(v ₂ /v ₁ )d _{of the thickness d 1 of the first layer 211 1} times the range.

The number of layers of the first layer 111 and the second layer 112 is in the range of 10 to 100 W in order to ensure the power resistance of a frequency filter used as a base station of a mobile phone, as in the case of the first embodiment. It is determined by the method of power resistance as the upper limit value.

The frequency filter 20 of the second embodiment can be produced by basically the same method as the frequency filter 10 of the first embodiment. However, when the polarization P of the first layer 211 perpendicular to the direction of the case of ₁ 211 to 9 of the first layer, without the substrate surface is inclined with respect to the electrodes or on the magnetron temperature gradient is formed on an inner surface of the substrate The first layer 211 and the second layer 212 may be formed by sputtering after the substrate and the upper surface of the magnetron electrode are arranged parallel to each other.

In the frequency filter 20 of the second embodiment, if a high frequency power including a plurality of frequencies is input between the first electrode 221 and the second electrode 222, the frequency power including the frequency and the magnitude of the high frequency power are generated between the electrodes. The size of the corresponding high-frequency voltage. Therefore, each of the first layers 211 uses the piezoelectric effect to operate at the same frequency at each frequency at specific frequencies determined by _{the thickness d 1} and the speed of sound v _{1 of the first layer 211 among the above-mentioned multiple frequencies.} vibrate in phase. On the other hand, the second layer 212 does not generate vibrations due to the piezoelectric effect, but receives vibrations from the first layer 211 , and the second layer 212 vibrates at the same specific multiple frequencies as the first layer 211 . Here, the thickness of the second layer 212, d _{2 is} identical to the first layer 211 of a thickness d _1, d ₁ or a state close to the _{0.5 × (v 2 / v 1} ) times of _{~ 2.0 × (v 2 / v} 1) d 1 The vibration with the frequency of the first layer 211 thus satisfies the resonance condition of the second layer 212 . As a result, in the entire layered body 21 , resonances having the above-described specific plurality of frequencies corresponding to the plurality of wave numbers that are half-integers per layer are generated. Thereby, the invention of the second embodiment operates as a frequency filter related to the frequency.

In addition, the frequency filter 20 ensures the power resistance of the frequency filter used in the base station of the mobile phone by repeating the first layer 211 and the second layer 212 alternately layer by layer as described above and adding a predetermined number of layers. .

Unlike the frequency filter 10 of the first embodiment, the frequency filter 20 of the second embodiment does not need to adjust the relationship between the polarization directions of the first layer 211 and the second layer 212, so it can be easily manufactured without using the 4 shows the special manufacturing method. On the other hand, in the frequency filter 10 of the first embodiment, not only the first layer 111 but also the second layer 112 is a piezoelectric body, whereby the second layer 112 also becomes a source of vibration. 2. The frequency filter 20 of the embodiment has a stronger output signal.

Furthermore, the frequency filter 20 of the second embodiment can also be used for applications other than base stations of mobile phones. In this case, depending on the application (such as the case of mobile phone terminals), the power resistance to 10 W of high frequency power is not required.

(3) Others As mentioned above, the frequency filter 10 of the first embodiment, the frequency filter 10A of its modification, and the frequency filter 20 of the second embodiment have been described, but the present invention is not limited to these three examples, and Various deformations are made. For example, in the frequency filter 20 of the second embodiment, an acoustic Bragg reflector can be provided in the same manner as the frequency filter 10A of the modification of the first embodiment.

10, 10A, 20: Frequency filter 11, 21: Laminated body 111, 211: First layer 112, 212: Second layer 121, 221: First electrode 122, 222: Second electrode 13: Acoustic Bragg reflector 131 , 132: layer constituting the acoustic Bragg reflector 30: magnetron sputtering device 31: vacuum vessel 32: magnetron electrode 33: substrate holder 34: high frequency power supply 341: matching box 35: cooling mechanism d ₁ , d ₂ : Thickness P ₁ , P ₂ : Polarization P _1// , P _{2 //} : Parallel component S: Substrate T, TM, T1, T2: Target

Fig. 1 is a schematic diagram showing a first embodiment of a frequency filter for a base station of a mobile phone according to the present invention. 2 is a diagram showing the polarization directions of the first layer and the second layer in the frequency filter of the first embodiment. 3 is a schematic diagram showing an example of a magnetron sputtering apparatus for producing the frequency filter of the first embodiment. [FIG. 4] (a)-(f) are schematic diagrams which show the manufacturing process of the frequency filter of 1st Embodiment. 5 is a schematic diagram showing a modification of the frequency filter of the first embodiment. FIG. 6 is a graph showing the result of calculating the conversion loss of the frequency filter (supported by a quartz glass substrate) of the first embodiment by experiment and calculation. FIG. 7 is a graph showing the results obtained by obtaining the impedance of the frequency filter according to the modification of the first embodiment by experiments and calculations. [Fig. 8] The frequency filters ((a) to (c)) of the first layer and the second layer different from the example shown in Fig. 6 and the frequency filter of the reference example ( (d)) Graph of the result obtained by calculating the conversion loss. Fig. 9 is a schematic diagram showing a second embodiment of a frequency filter for a base station of a mobile phone according to the present invention.

10: Frequency filter

11: Laminate

111: Tier 1

112: Tier 2

121: 1st electrode

122: 2nd electrode

d ₁ , d ₂ : thickness

P ₁ , P ₂ : Polarization

Claims (4)

A frequency filter comprising: a) a laminated body formed by alternately repeating a first layer and a second layer layer by layer and adding a predetermined number of layers, wherein the first layer is a piezoelectric material made of a first piezoelectric material layer, the polarization is oriented in a predetermined direction, the second layer is made of a second piezoelectric material, and the component of the polarization in the direction perpendicular or parallel to the first layer is oriented toward the polarization of the first layer. It is composed of a piezoelectric layer in a direction whose components differ by 180°, or a non-piezoelectric layer made of a non-piezoelectric insulating material, using the speed of sound v ₁ in the first layer and the speed of sound v _{2 in the second layer.} , the thickness d ₁ of the first layer and the thickness d ₂ of the second layer are within the range of 0.5×(v ₂ /v ₁ )d ₁ ≦d ₂ ≦2.0×(v ₂ /v ₁ )d ₁ ; and b) 1 pair of electrodes, which are arranged so as to sandwich the above-mentioned laminated body in the lamination direction; characterized in that: the above-mentioned predetermined number is set so as to have power resistance to high-frequency power of 10 W. The frequency filter of claim 1, wherein the second layer is composed of the non-piezoelectric layer. The frequency filter according to claim 1 or 2, further comprising an acoustic Bragg reflector on one side of the pair of electrodes. A frequency filter, comprising: a) a layered body formed by alternately repeating a first layer and a second layer layer by layer and adding a predetermined number of layers, wherein the first layer is a first piezoelectric material made of piezoelectric layers, one of a predetermined polarization direction towards the second layer system is composed of a non-piezoelectric layer of non-piezoelectric insulating material, the sonic velocity within the above-described first layer ₁ v 1 and the second The speed of sound v ₂ in the layer, the thickness d ₁ of the first layer and the thickness d ₂ of the second layer are 0.5×(v ₂ /v ₁ )d ₁ ≦d ₂ ≦2.0×(v ₂ /v ₁ )d ₁ ; and b) 1 pair of electrodes, which are arranged so as to sandwich the above-mentioned laminated body in the direction of lamination.

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