TWI224891B - Filter device of balanced structure thin-film bulk acoustic resonators (FBAR) and duplexer using this device - Google Patents

Abstract

A filter device having balance structure thin-film bulk acoustic resonators (FBAR) and a duplexer using this device are provided, which use one thin-film bulk acoustic resonators thickness (same resonant frequency) to simultaneously meet the specifications of filter and duplexer. Therefore, production complexity and process instability resulting from the traditional balanced and unbalanced structures using multiple thickness thin-film bulk acoustic resonators are avoided. Besides, this invention adopts inductors or capacitors to replace a part of the thin-film bulk acoustic resonators so the number of the filter using thin-film bulk acoustic resonators is reduced. At the same time, the additional transmission line of the duplexer application is unnecessary so the area of the duplexer and the parasitic problem can be reduced.

Description

1224891

V. Description of the invention (1) [Technical field to which the invention belongs The present invention relates to a wireless communication device. The filter in the communication device is a thin-film bulk acoustic wave resonator filter with a balanced architecture. ^ 'Special [prior art]. Waves (fi 11 er) are widely used in wireless communications, and there are about 10 billion of them each year. It can be mainly divided into LC filter, 1 + estimated surface acoustic wave filter and thin film bulk acoustic wave filter, etc. — 4 miles', while thin film acoustic wave filters are small, easy to reach high frequency, and low Insertion loss ^: Ear-like, and has the ability to integrate with IC, so it is the most promising. Xundouinch currently uses thin-film bulk acoustic wave resonators to make filter culture. ° 3 different texts ^ zero ^ addition structure to distinguish between balanced (Balanced type) and unbalanced gas (Unbalanced type) filters, balanced As shown in the frame, it is composed of the first-film bulk acoustic wave resonator A and the second; body = "oscillator B constitutes a Lattice Type structure. As shown in" Figure 2 "in an unbalanced system, it is composed of the first film The bulk acoustic wave resonator A and the second ^^^ deaf wave resonator B form a ladder-type architecture. The difference between the two Y 1 is that the circuit architecture in [Figure 1] is the main circuit that is paired up and down, left and right, and does not need to pass through an additional unbalanced to balanced architecture conversion circuit, such as 苒 balun and other components to compare with other balanced architectures. Components are connected for anti-matching and signal conversion. The filter of the unbalanced architecture has the largest resistance, requires additional conversion circuits, and due to grounding, capacitance, ice, and interference required by the information. Do not go to external miscellaneous. For example, the United States No. 6 2 7 8 34 2 proposed a balanced circuit to design a filter, which controls the band-pass filter through the area control. 1248891 V. Description of the invention (2) Bandwidth reduction (rol 1-of f), however, its structure still requires many thin-film bulk acoustic resonators with different numbers and different thicknesses. In addition to causing the area of the entire filter to be too large, it has a manufacturing complexity and process stability. Degree is a big test. For the filter specifications in the duplexer, according to different system requirements, the guard band between the required transmission signal and the received signal is usually less than 2% of the carrier frequency, and the transmitted signal and reception The bandwidth of the signal is usually 3% of the carrier frequency, which means that both the filter at the transmitting end and the filter at the receiving end need to have a fairly steep bandwidth roll-off (rolhof f). In addition, in order to ensure that the transmitted signal and the received signal do not interfere with each other, the attenuation of the repulsion band (st oopband) of the two band-pass filters in the passband of the other band-pass filter must comply with specification. On the other hand, in order to ensure that the signal sent from the transmitting end will not be fed back to the receiving end and can be sent directly to the antenna end to send out the signal, the input impedance of the input end of the receiving filter must be high impedance. In the current thin film bulk acoustic wave resonator balanced filter or duplexer, the number of required thin film bulk acoustic wave resonators is too large, which makes it difficult to reduce the area, and like the unbalanced filter or duplexer, a variety of different The thickness of the thin-film bulk acoustic wave resonator causes complexity and instability in the manufacturing process. In addition, when a thin-film bulk acoustic wave resonator is used to design a transmitting-end filter and a receiving-end filter in a duplexer, when the input ends of the transmitting-end filter and the receiving-end filter are connected to the antenna end, the transmission signal and the reception signal are transmitted. The segmentation is mainly determined by the frequency of the signal itself. Therefore, it is necessary to ensure that the signal sent from the transmitting end can be directly sent to the antenna, and to avoid the signal from collapsing to the receiving end, the low-noise amplifier (LNA) at the receiving end Break through

Page 7 1224891 V. Description of Invention (3) Harm. In general, to solve this problem, a quarter-wavelength transmission line is added between the filter at the receiving end and the antenna as a phase shift to form a high impedance to reflect the signal at the transmitting end. The biggest disadvantage of this method is that this transmission line will increase the area of the entire duplexer and will produce unnecessary parasitic effects. Ping Ji Bo Zhi Heng Zhi Zhi Ju Ping Yi Xi Constructing Skills Determining the Structure of Demonstration Explaining the Explaining Types of Exercises Explained by the use of balance to explain the solution, used to develop the purpose of the loan to be installed. Species, ’the main wave point of a filter for the job of Mingzi and mention double. If you want to ask the question, the master and the master are asking the question, and the sound of the wave and the sound of the question are on the question of the eye and the question body has a filter. Let ’s pretend to coexist, and the built-in filter of the built-in vocal filter is based on the body structure of the wave-shaped body. The balance of the membrane is equal to the volume of the body ..... A thin electric reduction with brackets is included, with a terminal end and a decay between one and two. The first one includes the first and the same end including the AND and the phase; One to three thick tones and a fourth-order oscillator are connected to the sub-terminal by the end, two waves and one connected to the same filter and coupling are connected to the sub-terminal, and the end of the wave is connected to the three-terminal. Acoustic four-coupling vibrating body is composed of two parts, one is wave, one is wave, one end is body, one is acoustic, one is anti-body, one is second, and one is thin. One thin and one vibrating the first structure, one or two, and a second middle wave, and the one by one sound

建 第 8 页 1224891 V. Description of the invention (4) The terminal is a third terminal and a fourth terminal, and the device includes a first thin film bulk acoustic wave resonator coupled between the first terminal and the fourth terminal; a first Two thin-film bulk acoustic wave resonators are coupled between the second end and the third end, wherein the first and second thin-film bulk acoustic wave resonators have the same thickness, and the thin-film bulk acoustic wave resonators have more than one of the same resonance frequency; A reactance element is connected between the first end and the second end to adjust the attenuation of the repulsion band; and a second reactance element is coupled between the third end and the fourth end to adjust the repulsion band. The amount of attenuation. According to another object of the present invention, the duplexer of the thin film bulk acoustic wave filter device using the balanced structure disclosed in the present invention has a first port, a second port, and a third port, including: A transmission filter, which is coupled to the first bulk acoustically coupled to the thin-wave resonance structure of the thin-film structure. The thin-medium root-wave device is the stability of the resonance composition. The membrane bulk acoustic filtering device is balanced according to the origin and the use frequency. The other second port is composed of more than one thin frame of a balanced structure in series to form a filtering device; and a receiving filter is connected to the third port. The filter device is composed of more than one vibrator of a balanced structure in series; wherein the thickness of the balanced frame wave resonator filter devices is the same, and the film bulk sound has more than one of the same resonance frequency. Such balanced frame-wave resonator filter devices are the main object according to the present invention. The thin-film bulk acoustic wave resonator of the balanced structure disclosed by the Ming Dynasty is a duplexer of the device. The present invention uses a single-thickness (also the same) thin-film bulk acoustic wave resonator with an inductor or capacitor circuit structure, on the one hand, reducing the complexity of the process Reducing the need for thin-film bulk acoustic resonators for filters

Page 9 1224891 V. Description of the invention (5) The number is required to reduce the area. In addition, through the structure of different series and parallel connection of the thin film bulk acoustic wave resonator with an additional inductor or capacitor, the two band-pass filters in the duplexer have a passband bandwidth that meets the specifications, and the attenuation of the repulsion band reaches a fixed value, and controls Look at the input impedance of the filter from the antenna to the receiver to ensure that it maintains high impedance. The thin-film bulk acoustic wave filter device of the balanced structure and the duplexer using the device according to the present invention allow signals sent from the transmitting end to be transmitted directly through the antenna without being transmitted to the receiving end, eliminating the need for an additional transmission line. Is needed, thus reducing the area of the duplexer and avoiding unnecessary parasitic effects. At the same time, the external converter circuit or components are eliminated, and the problem of interference with noise is eliminated. Regarding the features and implementation of the present invention, the preferred embodiment will be described in detail with reference to the drawings. [Embodiment] First, please refer to "Figure 3", which is the first embodiment of the circuit topology of the thin-film bulk acoustic wave filter device disclosed in the present invention, which has a single thickness (that is, the resonance frequency is the same). A thin-film bulk acoustic resonator and a reactive element (capacitive or inductive) are cross-connected to form a balanced topology filter. As shown in "Figure 3", it includes a first thin-film bulk acoustic wave resonator A coupled between the first end 1 and the second end 2, and a second thin-film bulk acoustic wave resonator B coupled between the third end and the third end. Between the four terminals, the first reactance element Cp1 is coupled between the first terminal 1 and the fourth terminal 4, and the second reactance element Cp2 is coupled between the second terminal 2 and the third terminal 3. In this embodiment, the first reactance element is a first capacitor, and the second

Page 10 1224891 V. Description of the invention (6) The reactance element is a second capacitor. Regarding the second embodiment of the present invention, please refer to "Fig. 4", which uses an inductor as a reactance element. As shown in "Figure 4", it includes a first thin-film bulk acoustic wave resonator A connected between the first end 1 and the second end 2, and a second thin-film bulk acoustic wave resonator B connected between the third end 3 and Between the fourth terminal 4, the first reactance element Lpl is coupled between the first terminal 1 and the fourth terminal 4, and the second reactance element Lp2 is coupled between the second terminal 2 and the third terminal 3. In this embodiment, the first reactance element Lpl is a first inductance, and the second reactance element Lp2 is a second inductance. Please refer to "Figure 5" for the third embodiment of the present invention. As shown in the figure, it includes a first thin-film bulk acoustic resonator horse connected between the first end 1 and the fourth end 4, and a second thin-film bulk acoustic wave. The resonator B is lightly connected between the second end 2 and the third end 3, the first reactance element Csl is coupled to the first end 1 and the second end 2, and the second reactance element C s 2 is coupled to the third end 3 And fourth end 4. In this embodiment, the first reactance element Csl is a first capacitor, and the second reactance element Cs2 is a second capacitor. Please refer to "Figure 6" for the fourth embodiment of the present invention. The capacitor in the third embodiment is replaced by an inductor. As shown in the figure, the first thin-film bulk acoustic wave resonator A is coupled to the first terminal 1 and Between the fourth end 4, the second thin-film bulk acoustic wave resonator B lies between the second end 2 and the third end 3, and the first reactance element Lsi is coupled between the first end 1 and the second end 2, and the second The reactance element Ls2 is coupled between the third terminal 3 and the fourth terminal 4. In this embodiment, the first reactance element L s 1 is a first inductance 'and the second reactance element L s 2 is a second inductance. In the filtering device in the above first to fourth embodiments, the first thin film bulk acoustic wave resonator A and the second thin film bulk acoustic wave resonator B and the first reactance element and

Page 111224891 V. Description of the invention (7) The second reactance element constitutes a balanced structure, in which all the thin-film bulk acoustic wave resonators have the same resonance frequency (single thickness), and the thin-film bulk acoustic wave resonator i has at least one or More than two resonance frequencies. The reactance element is used to adjust the attenuation of the repulsion band. Due to the characteristics of the thin-film bulk acoustic wave resonator, the frequency response of the filter will have a deep bending point (notch) at the high-frequency side or the low-frequency side of the passband, and it will also cause a sharp roll-off of the bandwidth (roll- off). Through the reactance elements (inductance or capacitance) in the first to fourth embodiments, the positions of these bending points can be controlled. As shown in "Figure 7" and "Figure 8", the positions of the bending points vary with The capacitance changes. Regarding the fifth embodiment disclosed in the present invention, the circuit architecture diagram is shown in the reference | "Figure 9", the thin film bulk acoustic resonator in the first embodiment is connected in parallel with a third inductor Lp3 and a fourth inductor The inductor Lp4, or the sixth embodiment shown in FIG. 10, connects the thin film bulk acoustic resonator in the first embodiment with a third inductor L s 3 and a fourth inductor L s 4 in series, respectively. The structures of the fifth and sixth embodiments are that an external adjustment element (such as an inductor or a capacitor) is used in series or in parallel with the thin film bulk acoustic resonator to make the bandwidth of the filter better meet the required specifications. This is because it is limited by the △ f (the difference between the parallel resonance frequency fa and the series resonance frequency fr, determined by the material) of the thin-film bulk acoustic wave resonator itself. The bandwidth of the entire filter may be unsatisfactory, so the fifth and sixth The structure of the embodiment can overcome the above problems and increase its equivalent Δf. The equivalent A f can be increased by adding inductors in series or parallel to the thin-film bulk acoustic resonator (such as "Figure 8"). When the film bulk acoustic resonance

Page 12 1224891 V. Description of the invention (8) If the series capacitor or capacitor is connected in series or in parallel, the equivalent A f will be reduced, and therefore the bandwidth of the filter's passband will be reduced. The seventh embodiment is a filtering structure designed by this parallel inductor. Please refer to "Figure 11" for a band-pass filter. Please refer to "Figure 12" for the frequency response diagram. By applying the above-disclosed embodiment, a duplexer can be fabricated, including a receiving filter and a transmitting filter. When designing the receiving filter Rx in the duplexer, it is necessary to pay attention to whether the signal sent by the transmitting end will reverse back to the receiving end, and pass the low noise amplifier through. Make sure that the impedance seen by the receiving filter from the transmitting end is high impedance in the passband band of the transmitting filter. As for the design of the transmission filter, only the issues of bandwidth and attenuation need to be considered. Based on the above observations, the two band-pass filters are connected to form a thin-film bulk acoustic wave duplexer. As shown in "Figure 13", it consists of a receiver wave Rx and a transmission filter Tx, which is implemented here. In the example, the receiving filter Rx and the transmitting filter Tx are each composed of two thin film bulk acoustic wave resonator filters according to the first embodiment disclosed in the present invention, wherein the transmitting filter is coupled to the first port 10 and Between the second port 20, the receiving filter is coupled between the first port 10 and the third port 30. For another embodiment of the duplexer, please refer to "Figure 14", in which the transmitting-end filter is composed of two thin-film bulk acoustic wave resonator filters of the seventh embodiment. Its insertion loss and reflection loss have characteristics as shown in "Figure 15". The invention utilizes an inductor or a capacitor and a thin-film bulk acoustic wave resonator to form a balanced filter and a duplexer circuit structure, which not only uses a single thin

Page 131224891 V. Description of the invention (9) The film bulk acoustic wave resonator reduces the complexity and instability in the process, and at the same time, the inductor or capacitor is used to reduce the number of thin film bulk acoustic wave resonators required to reduce the area demand. In addition to these inductors or capacitors, you can control the attenuation of the filter in the repulsion band, and at the input end of the receiving filter, let the antenna end look into the receiving end filter as a high impedance, so that the signal sent from the transmitting end will not reverse. To the receiving end, and can be directly sent to the antenna end to send out the signal. In this way, there is no need to add an additional transmission line between the antenna end and the receiving end, which can reduce the area of the duplexer and avoid parasitic effects caused by the additional transmission line. Although the present invention is disclosed in the foregoing preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art of similarity can make some modifications and retouching without departing from the spirit and scope of the present invention. The patent protection scope of the invention shall be determined by the scope of the patent application scope attached to this specification.

Page 141224891 Brief description of the diagram. Figure 1 is a thin-film bulk acoustic wave resonator with a balanced structure disclosed in the prior art. Figure 2 is a thin-film bulk acoustic wave resonator with an unbalanced structure disclosed in the prior art. Filter; Figure 3 is the first embodiment of the thin-film bulk acoustic wave filter of the balanced structure disclosed in the present invention; ~ Figure 4 is the thin-film bulk acoustic wave resonator of the balanced structure disclosed in the present invention; The second embodiment of the filter; ~ FIG. 5 is the third embodiment of the thin-film bulk acoustic wave filter of the balanced structure disclosed in the present invention; and FIG. 6 is the balanced structure of the present disclosure. The fourth embodiment of the thin film bulk acoustic wave filter; FIG. 7 is the frequency response of the filter; FIG. 8 is the frequency response of the filter; and FIG. 9 is the balanced structure disclosed in the present invention. Fifth embodiment of a thin-film bulk acoustic wave filter; FIG. 10 is a sixth embodiment of the thin-film bulk acoustic wave filter of the balanced structure disclosed in the present invention; FIG. 11 is a drawing of the present invention Expose The seventh embodiment of the thin-film bulk acoustic wave resonator filter with balanced structure; ¥ FIG. 12 is a frequency response diagram of the thin-film bulk acoustic wave filter with balanced structure disclosed in the present invention; FIG. A duplexer of a thin film bulk acoustic wave filter using a balanced structure disclosed in the present invention;

Page 151224891 Brief Description of Drawings Figures 14 and 4 are the duplexers of the thin film bulk acoustic wave filter using the balanced structure disclosed in the present invention; and Figure 15 is the duplex of Figures 14 and 14 Device's insertion loss and reflection loss. [Illustration of Symbols] A The first film bulk acoustic wave resonator B The second film bulk acoustic wave resonator

Cpl first reactance element

Cp2 second reactance element

Csl first reactance element

Cs2 Second reactance element L p 1 First reactance element

Lp2 second reactance element LSI first reactance element

Ls2 second reactance element

Lp3 The third inductance L p 4 The fourth inductance

Ls3 third inductor

Ls4 fourth inductor

Tx transmit filter

Rx receive filter 1 first end 2 second end 3 third end 4 fourth end

Page 16 1224891 Simple illustration of the diagram 10 First port 2 0 Second port 30 Third port

Claims (1)

1224891 VI. Application patent scope 1. A thin film bulk acoustic wave filter device with a balanced structure, which has a first end, a second end, a third end, and a fourth end. The device includes ... A thin film bulk acoustic wave resonator is coupled between the first end and the second end; a second thin film bulk acoustic wave resonator is coupled between the third end and the fourth end, wherein the first The thicknesses of the second thin-film bulk acoustic wave resonators are the same, and the thin-film bulk acoustic wave resonators have more than one of the same resonance frequency; a first reactance element is coupled between the first end and the fourth end to adjust An attenuation amount of the repulsion band; and / or a second reactance element coupled between the second end and the third end to adjust the attenuation amount of the repulsion band. 2. The thin film bulk acoustic wave resonator device of the balanced structure according to item 1 of the scope of patent application, wherein the first reactance element and the second reactance element are a capacitor. 3. The thin film bulk acoustic wave resonator device of the balanced structure according to item 1 of the scope of patent application, wherein the first reactance element and the second reactance element are an inductor. 4. The thin film bulk acoustic wave resonator filter device of the balanced structure according to item 1 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have an inductor connected in parallel to adjust the passband of the filter. bandwidth. 5. The thin film bulk acoustic wave resonator device of the balanced structure according to item 1 of the scope of patent application, wherein the first and second thin film bulk acoustic wave resonators Page 18 1224891 6. Scope of patent application A capacitor is connected in parallel to adjust the bandwidth of the passband of the filter. 6. The thin film bulk acoustic wave filter device of the balanced structure according to item 1 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have an inductor connected in series to adjust the passband of the filter. bandwidth. 7. The thin film bulk acoustic wave resonator filter device of the balanced structure according to item 1 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have a capacitor connected in series to adjust the passband of the filter. bandwidth. 8. A filtering device is a filtering device composed of more than one thin film bulk acoustic wave resonator with a balanced structure as described in item 1 of the scope of patent application. 9. A thin-film bulk acoustic wave filter device with a balanced structure having a first end, a second end, a third end, and a fourth end, the device includes a first thin-film bulk acoustic wave resonator Is coupled between the first end and the fourth end; a second thin-film bulk acoustic wave resonator is coupled between the second and third ends, wherein the first and second thin-film bulk acoustic waves The thicknesses of the resonators are the same, and the thin-film bulk acoustic resonators have more than one resonance frequency; a first reactance element is coupled between the first end and the second end to adjust the attenuation of the repulsion band; A second reactance element is coupled between the third terminal and the fourth terminal to adjust the attenuation of the repulsion band. 10. Thin film bulk acoustic wave with balanced structure as described in item 9 of the scope of patent application Page 19 1224891 VI. Scope of patent application The resonator filter device, wherein the first reactance element and the second reactance element are a capacitor. 11. The thin film bulk acoustic wave resonator device of the balanced structure according to item 9 of the scope of the patent application, wherein the first reactance element and the second reactance element are an inductor. 1 2. The thin film bulk acoustic wave filter device of the balanced structure according to item 9 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have an inductor connected in parallel to adjust the filter passband. Bandwidth. 13. The thin film bulk acoustic wave filter device of the balanced structure according to item 9 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have a capacitor connected in parallel to adjust the filter passband. Bandwidth. 14. The thin film bulk acoustic wave resonator device with a balanced structure as described in item 9 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have an inductor connected in series to adjust the filter pass. Bandwidth of the band. 15. The thin film bulk acoustic wave filter device of the balanced structure according to item 9 of the scope of the patent application, wherein the first and second thin film bulk acoustic wave resonators have a capacitor connected in series to adjust the filter passband. Bandwidth. 16. A filter device is a filter device composed of more than one thin film bulk acoustic wave resonator with a balanced structure as described in item 9 of the scope of patent application. Page 201224891 VI. Scope of patent application 1 7. — A duplexer consisting of a thin-film bulk acoustic wave filter and a wave device using a balanced structure, which has a first port, a second port, and a third port Including: a transmission filter coupled between the first port and the second port, which is a filter device composed of more than one film bulk acoustic wave resonator in a balanced structure in series; and a reception filter coupled Between the first port and the third port, more than one thin film bulk acoustic wave resonator in a balanced structure is connected in series to form a filtering and wave device, wherein the thin film bulk acoustic wave filter devices in the balanced structure have the same thickness These thin film bulk acoustic resonators have more than one of the same resonance frequency. 18. The duplexer as described in item 17 of the scope of patent application, wherein each of these thin film bulk acoustic wave filter devices with a balanced structure has a first end, a second end, a third end and A fourth end includes: a first thin film bulk acoustic wave resonator coupled between the first end and the second end; a second thin film bulk acoustic wave resonator coupled between the third end and Between the fourth end, where the thicknesses of the first and second thin-film bulk acoustic wave resonators are the same, the thin-film bulk acoustic wave resonators have more than one resonance frequency of the same; a first reactance element is coupled to the first Between the second terminal and the fourth terminal to adjust the attenuation of the repulsion band; and a second reactance element coupled between the second terminal and the third terminal Page 21 1224891 Sixth, the scope of the patent application, to adjust the rejection 19. For example, the patented patented reactance element and the 20th. For example, the patented patented reactance element and the second 1. For the patented second film bulk sound The entire filter passband 2 2. As the patent application of the second film bulk acoustic filter pass band 2 3. As the patent application of the second film bulk acoustic filter pass band 2 4. As the patent application of the second membrane body acoustic filter Acoustic shaping filter passband 25. For example, the band width of the wave-resonator of the band 18 of the second-reactance element of the second-reactive element of the band of the attenuation range of the patent-pending balanced structure. Bandwidth around the 18th wave resonator. Bandwidth around the 18th wave resonator. Bandwidth around the 18th wave resonator. The 17th volume of the film volume. In the duplexer, the first electrical component is a capacitor. In the duplexer, the first electrical component is parallel to the more separate inductive duplexer, the more separate said duplexer, and the more separate duplexer parallel to the duplexer ground. The ground of the series duplexer is connected in series, where the first has an inductor to adjust,-, where the first, has a capacitor to adjust, where the first has an inductor to adjust, where the first, has a capacitor to adjust- — *, Terminal, a 丨 a second terminal, each of these devices has a first, and includes: a first thin film bulk acoustic wave resonator described by the duplexer wave resonator filter third end and a The fourth end is coupled between the first end and the fourth end; between a second thin third end, a membrane bulk acoustic resonator is coupled between the first and second films at the second end and Of the bulk acoustic wave resonator Page 22 1224891 6. The scope of the patent application is the same, and has the same resonance frequency as the first one; a first reactance element is coupled between the first end and the second end to adjust the attenuation of the repulsion band. And a second reactance element coupled between the third end and the fourth end to adjust the attenuation of the repulsion band. 26. The duplexer according to item 25 of the scope of patent application, wherein the first reactance element and the second reactance element are a capacitor. 27. The duplexer according to item 25 of the scope of patent application, wherein the first reactance element and the second reactance element are an inductor. 28. The duplexer according to item 25 of the scope of patent application, wherein the first and second thin film bulk acoustic resonators have an inductor connected in parallel to adjust the bandwidth of the passband of the filter. 29. The duplexer according to item 25 of the scope of patent application, wherein the first and second thin film bulk acoustic resonators have a capacitor connected in parallel to adjust the bandwidth of the passband of the filter. 30. The duplexer according to item 25 of the scope of the patent application, wherein the first and second thin-film bulk acoustic wave resonators have an inductor connected in series to adjust the bandwidth of the passband of the filter. 3 1. The duplexer according to item 25 of the scope of patent application, wherein the first and second thin-film bulk acoustic wave resonators have a capacitor connected in series to adjust the bandwidth of the filter passband. Page 23