WO2017219251A1 - 一种梯形结构宽带压电滤波器 - Google Patents

一种梯形结构宽带压电滤波器 Download PDF

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Publication number
WO2017219251A1
WO2017219251A1 PCT/CN2016/086596 CN2016086596W WO2017219251A1 WO 2017219251 A1 WO2017219251 A1 WO 2017219251A1 CN 2016086596 W CN2016086596 W CN 2016086596W WO 2017219251 A1 WO2017219251 A1 WO 2017219251A1
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Prior art keywords
resonator
filter
inductor
series
resonators
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PCT/CN2016/086596
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English (en)
French (fr)
Inventor
庞慰
郑云卓
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诺思（天津）微系统有限公司
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Priority to US16/312,257 priority Critical patent/US10965273B2/en
Priority to PCT/CN2016/086596 priority patent/WO2017219251A1/zh
Priority to CN201680083811.XA priority patent/CN109643984B/zh
Publication of WO2017219251A1 publication Critical patent/WO2017219251A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/542—Filters comprising resonators of piezoelectric or electrostrictive material including passive elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/205—Constructional features of resonators consisting of piezoelectric or electrostrictive material having multiple resonators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/60—Electric coupling means therefor
    • H03H9/605—Electric coupling means therefor consisting of a ladder configuration
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/6433—Coupled resonator filters
    • H03H9/6483—Ladder SAW filters

Definitions

  • the present invention relates to the field of filtering devices for communication, and in particular to piezoelectric filters fabricated using the principle of piezoelectric effect.
  • the small-sized medium-frequency RF filter that can satisfy the communication terminal is mainly a piezoelectric acoustic wave filter
  • the resonators constituting such an acoustic wave filter mainly include: FBAR (Film Bulk Acoustic Resonator), SMR (SMR (Film Bulk Acoustic Resonator)) Solidly Mounted Resonator, SAW (Surface Acoustic Wave).
  • the topology of the filter circuit is mainly composed of a ladder structure and a grid structure.
  • the former is mainly used for a single-port (un-balance) input/output filter, and the latter is mainly used for at least one end of a dual port/differential. (balance) filter. Because the single-port filter is more convenient to use in the RF link, the design of the ladder structure dominates the design of high-performance acoustic filters and duplexers.
  • Figure 11 (a) is the electrical symbol of the piezoelectric acoustic resonator
  • Figure 11 (b) is its equivalent electrical model diagram, the electrical model is simplified to L m , C m and C 0 without considering the loss term.
  • Resonant circuit According to the resonance condition, the resonant circuit has two resonance frequency points: one is f s when the impedance value of the resonant circuit reaches a minimum value, f s is defined as the series resonant frequency point of the resonator; the other is when the resonant circuit impedance value reaches a maximum when f p, f p defines the parallel resonant frequency for the resonator. among them,
  • f s is smaller than f p .
  • Kt 2 eff of the resonator is defined, which can be expressed by f s and f p :
  • Figure 12 shows the relationship between the resonator impedance and f s and f p .
  • the larger the effective electromechanical coupling coefficient the greater the frequency difference between f s and f p , that is, the further away the two resonance frequencies are.
  • FIG. 1 is a circuit diagram of a conventional trapezoidal piezoelectric bandpass filter 100 of the prior art.
  • 131 is the input terminal of the filter
  • 132 is the output terminal of the filter.
  • first resonators 101, 102, 103, 104 connected in series at the series path position, the first resonator having a first series resonant frequency f s1 and a first parallel resonant frequency f P1 , and a series of second resonators 111 , 112 , 113 at a parallel path position connected in parallel from certain nodes on the series path, the second resonator having a second series resonant frequency f s2 and a second parallel resonance Frequency f p2 ; at the same time, auxiliary inductors 121 and 122 are added in order to connect the first resonator to the input and output terminals of the filter, and auxiliary inductors 123 and 124 are added in order to connect the second re
  • the auxiliary inductors may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball, etc., and their inductance values are generally It is located in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH.
  • Figure 13 (a) shows the first series resonant frequency f s1 and the first parallel resonant frequency f p1 of the first resonator of the prior art described above, and the second series resonant frequency f s2 and the second of the second resonator
  • the relationship between the parallel resonant frequencies f p2 : f s1 ⁇ f p1 , f s2 ⁇ f p2 , and f s1 is approximately equal to f p2 .
  • the first resonator and the second resonator can satisfy the above frequency characteristics by adding a mass load on the second resonator; for SAW, the first resonator can be adjusted by The pitch length, gap, distribution, thickness, and the like of the two resonator transducers such that the first resonator and the second resonator satisfy the above frequency characteristics.
  • the ladder structure filter 100 there are three relatively representative frequencies, and the following is explained by the principle of impedance division, how these three special frequency points constitute a piezoelectric band pass filter: when the frequency When f p1 is equal, the impedance of the first resonator at the series position reaches a maximum value, and the impedance of the second resonator at the parallel position is much lower than the impedance of the first resonator, and the signal flowing from the terminal 131 is absolutely large.
  • the filter 100 has a characteristic of blocking the passage of the signal; when the frequency is equal to f s1 or f p2 , the impedance of the first resonator at the series position reaches a minimum value, The impedance of the second resonator located at the parallel position reaches a maximum value, and most of the signal flowing from the terminal 131 flows through the series path through the first resonator to the terminal 132, and the filter 100 conducts a signal to the signal; when equal to f s2, the impedance of the second resonator positioned in parallel position reaches a minimum value, the impedance of the first resonator is located at a position far greater than the series impedance of the second resonator from the terminal 131 The signal, most of the flow through the second resonator to the ground, can not reach the terminal 132, the filter 100 is in signal characteristic of hindering.
  • filter 100 which is the stop band of the filter, other than f s2 or f p1 , can be obtained.
  • Near f s1 or f p2 is the pass band of the filter.
  • the bandwidth of a ladder structure filter such as 100 mainly depends on the difference between the series resonance frequency of the resonators it contains and the parallel resonance frequency, or, depending on the resonators it contains.
  • Effective electromechanical coupling coefficient in order to achieve a wider bandwidth filter, we must find ways to improve the effective electromechanical coupling coefficient of the resonator.
  • the electromechanical coupling coefficient is related to many factors and cannot be increased without limitation according to the needs of the user.
  • An example of an FBAR resonator fabricated using aluminum nitride (AlN) as a piezoelectric material has an effective electromechanical coupling coefficient of up to about 7.2%, and a bandpass filter that can be fabricated generally has a relative bandwidth of up to about 4.5%.
  • some communication frequency bands need to allocate a wider communication frequency band, for example, the 41st frequency band (Band41) according to the 3GPP protocol, and the passband range is from 2496MHz to 2690MHz. It has a bandwidth of 194MHz and a relative bandwidth of up to 7.5%. At the same time, it requires a low-frequency side communication signal, such as WLAN (2402.5MHz to 2481.5MHz), Band 40 (2300MHz to 2400MHz), etc., with a certain degree of suppression. At this time, it is no longer effective to extend the application bandwidth of the filter by using the traditional method of increasing the electromechanical coupling coefficient. This requires a special method to realize such a band-pass filter with high bandwidth and high suppression requirements.
  • WLAN 2402.5MHz to 2481.5MHz
  • Band 40 2300MHz to 2400MHz
  • a conventional method for expanding the application bandwidth of a filter by increasing the electromechanical coupling coefficient cannot satisfy all the needs, and the present invention provides a filter having an improved bandwidth.
  • Embodiments of the present invention provide a filter including: a plurality of first resonators, the plurality of first resonators being connected in series; a plurality of second resonators, each of the second resonators Connected between one end of one of the plurality of first resonators and a ground point; a bandwidth adjustment unit, a node connected between any two of the plurality of first resonators, and said Between the grounding points; wherein the parallel resonant frequency of the second resonator is lower than the series resonant frequency of the first resonator.
  • the bandwidth adjustment unit comprises a third resonator and a first inductor, the third resonator being connected in series with the first inductor.
  • the bandwidth adjustment unit comprises a capacitor and a first inductor, the capacitor being connected in series with the first inductor.
  • the bandwidth adjustment unit comprises a first inductor.
  • the difference between the series resonant frequencies of the second resonator and the first resonator is between 30% and 80% of the passband bandwidth of the filter.
  • the third resonator has a different resonant frequency than the second resonator.
  • the third resonator has the same resonant frequency as the first resonator.
  • the third resonator has a resonant frequency close to the first resonator.
  • the capacitors in the bandwidth adjustment unit are integrated on the chip using a semiconductor process.
  • the capacitor is a discrete capacitive component disposed outside the chip and integrated in a package carrier, the package carrier comprising the chip.
  • one end of the capacitor is connected to the node, one end of the first inductor is connected to the ground point; or one end of the capacitor is connected to the At a ground point, one end of the first inductor is connected to the node.
  • the first resonator is connected to an external signal port through a second inductor; and the second resonator is connected to the ground point through a third inductor.
  • the second inductor and the third inductor comprise bonding wires for connecting the chip to the package carrier, or comprising flip chip soldering the package in the package a metal conductor on the carrier.
  • the inductance values of the second inductor and the third inductor are in the range of 0.1 nH to 2 nH.
  • an impedance matching device coupled between the ground point and an input port or an output port of the filter.
  • the impedance matching device is a passive device, and the passive device includes an inductor, a capacitor, and a transmission line, and the implementation of the passive device includes a bonding wire and chip integration.
  • Passive device IPD, integrated or discrete device on a package carrier.
  • the inductance of the first inductor is in the range of 1 nH to 10 nH.
  • the resonator in the filter comprises a bulk acoustic wave piezoelectric resonator (FBAR) having an air gap, a solid-state assembly acoustic wave piezoelectric resonator (SMR) having a Bragg impedance reflection layer, or Surface acoustic wave piezoelectric resonator (SAW) having a cross-toothed structure.
  • FBAR bulk acoustic wave piezoelectric resonator
  • SMR solid-state assembly acoustic wave piezoelectric resonator
  • SAW Surface acoustic wave piezoelectric resonator
  • the filter of the invention realizes the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process, and has better out-of-band rejection.
  • Figure 1 is a schematic diagram of a ladder structure commonly used in current single-port bandpass filter designs
  • FIG. 2 is a schematic diagram of a broadband, highly suppressed piezoelectric filter 200 which is modified based on a conventional ladder structure filter according to the present invention
  • Figure 3 is a schematic diagram of an embodiment 300 in accordance with the present invention.
  • FIG. 4 is a schematic diagram of yet another embodiment 400 in accordance with the present invention.
  • FIG. 5 is a schematic diagram of yet another embodiment 500 in accordance with the present invention.
  • Figure 6 is a schematic diagram of yet another embodiment 600 in accordance with the present invention.
  • Figure 7 is a schematic diagram of yet another embodiment 700 in accordance with the present invention.
  • FIG. 8 is a schematic diagram of yet another embodiment 800 in accordance with the present invention.
  • Figure 9 is a schematic diagram of yet another embodiment 900 in accordance with the present invention.
  • Figure 10 is a schematic diagram of yet another embodiment 1000 in accordance with the present invention.
  • Figure 11 (a) is an electrical symbol of a piezoelectric acoustic wave resonator
  • Figure 11 (b) is an equivalent electrical model diagram of a piezoelectric acoustic wave resonator
  • Figure 12 is a schematic diagram showing the relationship between the impedance of the resonator and f s and f p ;
  • Figure 13 (a) is a schematic diagram showing the relationship of resonant frequency of a resonator in a prior art ladder structure filter
  • Figure 13 (b) is a schematic diagram showing the relationship between the filter curve and the resonant frequency in the prior art ladder structure filter
  • FIG. 14 is a schematic diagram showing the relationship of resonant frequency of a resonator in a ladder-structure wideband filter according to the present invention.
  • 15 is a graph showing amplitude-frequency response of insertion loss and return loss of the filter 200
  • 16 is a graph showing amplitude-frequency response of insertion loss and return loss of the filter 1000
  • 17 is a schematic diagram showing the relationship of resonator resonance frequency in the filter 400.
  • Figure 18 is a schematic illustration of the resonant frequency of the resonator in filter 900.
  • the present invention proposes a circuit structure that is different from the conventional ladder structure, and does not change the electromechanical coupling coefficient of the resonator, nor does it change the complexity of the manufacturing process.
  • a special parallel ground path is added to achieve the expansion of the relative bandwidth of the filter, and at the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for the piezoelectric filter.
  • the filter provided by the embodiment of the present invention has a bandwidth value exceeding at least 20% of the limit value of the conventional ladder structure, and the out-of-band rejection is not significantly deteriorated, especially the out-of-band rejection on the low-frequency side of the passband is not obvious. Deterioration.
  • FIG. 2 is a circuit diagram of a piezoelectric band pass filter 200 improved on the basis of the trapezoidal structure of FIG. 1.
  • 241 is the input terminal of the filter
  • 242 is the output terminal of the filter
  • the input and output terminals are ports connected to the external signal of the filter.
  • a resonant frequency f s1 and a first parallel resonant frequency f p1 and a series of second resonators 211, 212, 213 located at parallel path locations, drawn from certain nodes on the series path and grounded, wherein the second resonator One end of the second electrode 212 is connected to a node between the first resonator 201 and the first resonator 202; one end of the second resonator 212 is connected to a node between the first resonator 202 and the first resonator 203; the second resonator One end of the 213 is connected to a node between the first resonator 203 and the first resonator 204.
  • the second resonator 211, 212, 213 has a second series resonant frequency f s2 and a second parallel resonant frequency f p2 , and the relationship between the resonant frequencies of the first resonator and the second resonator is illustrated by Figure 14, where f P2 ⁇ f s1 .
  • the filter 200 further includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path that is extracted from a node where the first resonators 202 and 203 on the series path meet, the special The parallel ground path is composed of a third resonator 231 and a first inductor 226 connected in series and connected to a ground point.
  • the third resonator 231 has the same series resonant frequency as the first resonator, that is, the first series resonant frequency f s1 , and the same parallel resonant frequency, that is, the first parallel resonant frequency f p1 .
  • the first inductor 226 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 221 and 222 are added in order to connect the second resonator to the ground (wherein “ground” in the present invention may also be referred to as " The grounding point "), the auxiliary inductors 223, 224, 225 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 221, 222, 223, 224, 225 may also be referred to as second inductors, the inductance of which is typically in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance of the first inductor is greater than the inductance of the second inductor.
  • a third inductor 227 for impedance matching is added near the input terminal 241, and a resistor for impedance matching is added near the output terminal 242.
  • Three inductors 228 Three inductors 228.
  • the impedance matching device for impedance matching is not limited to an inductor, and may also include other passive devices such as capacitors, transmission lines, and the like, and implementations of the passive device include, but are not limited to, bonding wires, chip integrated passive devices. (IPD), package carrier integration, discrete devices, etc.
  • IPD chip integrated passive devices
  • Fig. 15 is a graph showing the amplitude-frequency response of the insertion loss and the return loss of the filter 200, wherein the graph (a) in Fig. 15 is the insertion loss curve of the filter wide band, and the graph (b) in Fig. 15 is the filter.
  • the passband insertion loss curve is shown in Figure 15 (c) is the return loss curve of the filter input port, and Figure 15 (d) is the return loss curve of the filter output port.
  • the filter has a center frequency of 2 GHz, a 3 dB bandwidth of 124 MHz, and a relative bandwidth of 6.25%. If the same resonator and the traditional ladder circuit structure are used, only the 3dB bandwidth of 70MHz can be achieved, that is, the relative bandwidth is about 4%.
  • the filter 200 increases the bandwidth while using the third resonator 231 and the first inductor 226, while the return loss is still better than -10 dB, and the out-of-band rejection on the low-frequency side of the passband is 33 dB.
  • the out-of-band suppression is not significantly deteriorated, and in particular, the out-of-band suppression on the low-frequency side of the pass band is not significantly deteriorated.
  • the filter 200 can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. It has better out-of-band rejection characteristics and meets the high performance requirements of piezoelectric filters.
  • the filter provided by the embodiment of the present invention has a bandwidth value exceeding at least 20% of the limit value of the conventional ladder structure, and the out-of-band rejection is not significantly deteriorated, especially the out-of-band rejection on the low-frequency side of the passband is not obvious. Deterioration.
  • FIG. 3 is a schematic diagram of an embodiment 300 in accordance with the present invention.
  • 341 is the input terminal of the filter
  • 342 is the output terminal of the filter.
  • first resonators 301, 302, 303, 304, 305, 306 connected in series at the position of the series path, the first resonators 301, 302, 303, 304 , 305, 306 having a first series resonant frequency f s1 and a first parallel resonant frequency f p1 ; and a series of second resonators 311, 312, 313 located in parallel path positions, connected in parallel from certain nodes on the series path 314, wherein one end of the second resonator 311 is connected to a node between the first resonators 301 and 302; one ends of the second resonators 312 and 313 are connected together and connected between the first resonators 303 and 304 One node; one end of the second resonators 301, 303, 304,
  • the second resonator 311, 312, 313, 314 has a second series resonant frequency f s2 and a second parallel resonant frequency f p2 , and the relationship between the resonant frequencies of the first resonator and the second resonator can be referred to FIG. f p2 ⁇ f s1 .
  • the filter 300 further includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path that is extracted from a node where the first resonators 303 and 304 on the series path meet, the special The parallel ground path is composed of a third resonator 331 and a first inductor 326 connected in series and connected to ground.
  • the third resonator 331 has the same series resonant frequency as the first resonator, that is, the first series resonant frequency f s1 , and the same parallel resonant frequency, that is, the first parallel resonant frequency f p1 .
  • the first inductor 326 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 321 and 322 are added, and in order to connect the second resonator to the ground, auxiliary inductors 323, 324, 325 are added, of which the second The other ends of the resonators 312 and 313 are connected together and connected to ground through an auxiliary inductor 324.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 321, 322, 323, 324, 325 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 327 for impedance matching is added near the input terminal 341, and a resistor for impedance matching is added near the output terminal 342.
  • the three inductors 328, and the devices for impedance matching in the filter 300 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • the filter 300 according to an embodiment of the present invention can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • FIG. 4 is a schematic diagram of yet another embodiment 400 in accordance with the present invention.
  • 441 is the input terminal of the filter
  • 442 is the output terminal of the filter.
  • first resonators 401, 404 and third resonators 402, 403 which are connected in series at the series path position, and the third resonators 402 and 403 are connected in series
  • the first resonators 401, 404 have a first series resonant frequency f s1 and a first parallel resonant frequency f p1 ; and a series of certain parallel path locations, from the series path a second resonator 411, 412, 413 whose node is grounded in parallel, wherein one end of the second resonator 411 is connected to a node between the first resonator 401 and the third resonator 402; one end of the second resonator 412 is connected to A node
  • the filter 400 further includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path that is taken from a node where the third resonators 402 and 403 on the series path meet, wherein A special parallel ground path is composed of a third resonator 431 and a first inductor 426 connected in series and connected to ground.
  • the third resonator 402, 403, 431 has a third series resonant frequency f s3 and a third parallel resonant frequency f p3 .
  • the relationship between the resonance frequencies of the first resonator, the second resonator, and the third resonator is shown by Fig. 17, where f p2 ⁇ f s3 ⁇ f s1 .
  • the first inductor 426 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 421 and 422 are added, and in order to connect the second resonator to the ground, auxiliary inductors 423, 424, and 425 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 421, 422, 423, 424, 425 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 427 for impedance matching is added near the input terminal 441, and a resistor for impedance matching is added near the output terminal 442.
  • the filter 400 can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • FIG. 5 is a schematic diagram of yet another embodiment 500 in accordance with the present invention.
  • 541 is the input terminal of the filter
  • 542 is the output terminal of the filter.
  • one end of the second resonator 511 is connected to a node between the first resonators 501 and 502; one end of the second resonator 512 is connected to a node between the first resonators 502 and 503, and the third resonator 513 is One end is connected to a node between the first resonators 503 and 504.
  • filter 500 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the special parallel ground path is taken from a node where the first resonators 502 and 503 are connected in series
  • the special parallel ground path is composed of a capacitor 531 and a first inductor 526 connected in series and connected to the ground.
  • Capacitor 531 can be integrated on the chip using a semiconductor process, and capacitor 531 can be integrated into the package carrier independently of the chip, such as with discrete capacitive devices, or by other processes. The order in which signals flow through capacitor 531 and first inductor 526 in a particular parallel ground path is interchangeable.
  • the first inductor 526 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 521 and 522 are added, and in order to connect the second resonator to the ground, auxiliary inductors 523, 524, and 525 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 521, 522, 523, 524, 525 may also be referred to as second inductors, the inductance of which is typically in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 527 for impedance matching is added near the input terminal 541, and a resistor for impedance matching is added near the output terminal 542.
  • the three inductors 528, and the devices for impedance matching in the filter 500 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • the filter 500 based on one embodiment of the present invention does not change the electromechanical coupling coefficient of the resonator, Under the premise of not changing the complexity of the manufacturing process, the special parallel parallel grounding path is added to realize the expansion of the relative bandwidth of the filter, and at the same time, it has better out-of-band suppression characteristics and achieves the high performance requirement of the piezoelectric filter.
  • FIG. 6 is a schematic diagram of yet another embodiment 600 in accordance with the present invention.
  • 641 is the input terminal of the filter
  • 642 is the output terminal of the filter.
  • the relationship between the series resonance frequency f s2 and the second parallel resonance frequency f p2 , the resonance frequencies of the first resonator and the second resonator can be referred to FIG.
  • one end of the second resonator 611 is connected to a node between the first resonators 601 and 602, and one end of the second resonator 612 is connected to a node between the first resonators 603 and 604.
  • filter 600 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the special parallel ground path is taken from a node where the first resonators 602 and 603 are connected in series, and the special parallel ground path is composed of a third resonator 631 and a first inductor 625 connected in series and Connect to the ground.
  • the third resonator 631 has the same series resonant frequency as the first resonator, that is, the first series resonant frequency f s1 , and the same parallel resonant frequency, that is, the first parallel resonant frequency f p1 .
  • the first inductor 625 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 621 and 622 are added, and in order to connect the second resonator to the ground, auxiliary inductors 623 and 624 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 621, 622, 623, 624 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH.
  • the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 626 for impedance matching is added near the input terminal 641, and a resistor for impedance matching is added near the output terminal 642.
  • the three inductors 627, and the devices for impedance matching in the filter 600 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • the filter 600 according to an embodiment of the present invention can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • FIG. 7 is a schematic diagram of yet another embodiment 700 in accordance with the present invention.
  • 741 is the input terminal of the filter
  • 742 is the output terminal of the filter.
  • first resonators 701, 702, 703, 704 connected in series at series path positions, and the first resonators 701, 702, 703, 704 have a first series connection.
  • one end of the second resonator 711 is connected to a node between the first resonators 701 and 702
  • one end of the second resonator 712 is connected to a node between the first resonators 702 and 703
  • the second resonator 713 One end is connected to a node between the first resonators 703 and 704.
  • filter 700 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the particular parallel ground path is drawn from a node where the first resonators 702 and 703 on the series path meet, and the particular parallel ground path includes the first inductor 726 and is connected to ground.
  • the first inductor 726 has a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 721 and 722 are added, and in order to connect the second resonator to ground, auxiliary inductors 723, 724, and 725 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 721, 722, 723, 724, 725 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 727 for impedance matching is added near the input terminal 741, and a resistor for impedance matching is added near the output terminal 742.
  • Three inductors 728, and in the filter 700 for impedance matching devices and filters 200 The impedance matching device is similar and will not be described here.
  • the filter 700 according to an embodiment of the present invention can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • FIG. 8 is a schematic diagram of yet another embodiment 800 in accordance with the present invention.
  • 841 is the input terminal of the filter
  • 842 is the output terminal of the filter.
  • first resonators 801, 805 and third resonators 802, 803, 804 which are connected in series at the series path position, and the third resonators 802, 803, 804 Connected in series between the first resonators 801, 805 having a first series resonant frequency f s1 and a first parallel resonant frequency f p1 ; and a series of positions in the parallel path from the series path
  • the second resonators 811, 812, 813, 814 whose nodes are grounded in parallel have a second series resonant frequency f s2 and a second parallel resonant frequency f p2 .
  • one end of the second resonator 811 is connected to a node between the first resonator 801 and the third resonator 802; one end of the second resonator 812 is connected to a node between the third resonators 802 and 803; One end of the resonator 813 is connected to a node between the third resonators 803 and 804; and one end of the second resonator 814 is connected to a node between the third resonator 804 and the first resonator 805.
  • filter 800 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the special parallel ground path is led from a node where the third resonators 802 and 803 on the series path are connected and a node where the third resonators 803 and 804 are connected, wherein a special parallel ground path is made up of a third Resonator 831 and first inductor 827 are formed in series and connected to ground, and another special parallel ground path is composed of a third resonator 832 and first inductor 828 connected in series and connected to ground.
  • the third resonators 802, 803, 804, 831, 832 have a third series resonant frequency f s3 and a third parallel resonant frequency f p3 .
  • the relationship between the resonance frequencies of the first resonator, the second resonator, and the third resonator can be referred to Fig. 17, where f p2 ⁇ f s3 ⁇ f s1 .
  • the first inductors 827, 828 have a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 821 and 822 are added, and in order to connect the second resonator to ground, auxiliary inductors 823, 824, 825, and 826 are added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 821, 822, 823, 824, 825, 826 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 829 for impedance matching is added near the input terminal 841, and a resistor for impedance matching is added near the output terminal 842.
  • the three inductors 830, and the devices for impedance matching in the filter 800 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • the filter 800 according to an embodiment of the present invention can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • 9 is a schematic diagram of yet another embodiment 900 in accordance with the present invention.
  • 941 is the input terminal of the filter
  • 942 is the output terminal of the filter.
  • first resonators 901, 902, 903, 904, 905 connected in series at the series path position, the first resonators 901, 902, 903, 904, 905 Having a first series resonant frequency f s1 and a first parallel resonant frequency f p1 ; and a series of second resonators 912, 913 and a third resonator 911 located in parallel path positions, connected in parallel from certain nodes on the series path 914, the second resonator 912, 913 has a second series resonant frequency f s2 and a second parallel resonant frequency f p2 .
  • the third resonator 906, 907 are respectively connected to the first parallel resonator 901,905, 906,907,911,914 and the third resonator having a third series resonance frequency f s3 and the third parallel resonance frequency f p3.
  • the relationship between the resonance frequencies of the first resonator, the second resonator, and the third resonator is shown by Fig. 18, where f p2 ⁇ f p3 ⁇ f s1 .
  • one end of the third resonator 911 is connected to a node between the first resonators 901 and 902
  • one end of the second resonator 912 is connected to a node between the first resonators 902 and 903
  • the second resonator 913 is One end is connected to a node between the first resonators 903 and 904
  • one end of the third resonator 914 is connected to a node between the first resonators 904 and 905.
  • filter 900 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the special parallel ground path is led from the node where the first resonators 902 and 903 are connected in the series path and the node where the first resonators 903 and 904 are connected, wherein a special parallel ground path is formed by a capacitor 931.
  • the first inductor 927 in series Connected to ground, another special parallel ground path consists of a capacitor 932 and a first inductor 928 connected in series and connected to ground.
  • Capacitors 931, 932 may be integrated on the chip using a semiconductor process, and capacitors 931, 932 may be independent of the chip, such as with discrete capacitive devices, or integrated into the package carrier using other processes.
  • the sequence of signals flowing through capacitor 931 and first inductor 927 in a particular parallel ground path and the order of flow through capacitor 932 and first inductor 928 are interchangeable.
  • the first inductors 927, 928 have a large inductance value, typically between 1 nH and 10 nH.
  • auxiliary inductors 921 and 922 are added, and in order to connect the second resonators 912, 913 and the third resonators 911, 914 to the ground, an auxiliary is added.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 921, 922, 923, 924, 925, 926 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 929 for impedance matching is added near the input terminal 941, and a resistor for impedance matching is added near the output terminal 942.
  • the three inductors 930, and the means for impedance matching in the filter 900 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • the filter 900 according to an embodiment of the present invention can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • FIG. 10 is a schematic diagram of yet another embodiment 1000 in accordance with the present invention.
  • 1041 is the input terminal of the filter
  • 1042 is the output terminal of the filter.
  • first resonators 1001, 1003, 1004, 1005, 1006 connected in series at the series path position
  • the first resonators 1001, 1003, 1004, 1005, 1006 Having a first series resonant frequency f s1 and a first parallel resonant frequency f p1
  • a series of second resonators 1011, 1012, 1013, 1014 at a parallel path position, connected in parallel from certain nodes on the series path
  • the two resonators 1011, 1012, 1013, 1014 have a second series resonant frequency f s2 and a second parallel resonant frequency f p2 .
  • one end of the second resonator 1011 is connected to a node between the first resonators 1001 and 1003
  • one end of the second resonator 1012 is connected to a node between the first resonators 1003 and 1004
  • the second resonator 1013 is One end is connected to a node between the first resonators 1004 and 1005
  • one end of the second resonator 1014 is connected to a node between the first resonators 1005 and 1006, and wherein the other ends of the second resonators 1011 and 1012 Connected together, the other ends of the second resonators 1013 and 1014 are connected together.
  • first resonators 1002, 1007 are respectively connected in parallel with the first resonators 1001, 1006, and the first resonators 1002, 1007 also have a first series resonance frequency f s1 and a first parallel resonance frequency f p1 , the first resonance
  • the relationship between the resonant frequency of the second resonator and the second resonator can be referred to Fig. 14, where f p2 ⁇ f s1 .
  • filter 1000 also includes a bandwidth adjustment unit, and the bandwidth adjustment unit includes a special parallel ground path.
  • the special parallel ground path is led from a node where the first resonators 1003 and 1004 on the series path meet and a node where the first resonators 1004 and 1005 are connected, wherein a special parallel ground path is formed by a third
  • the resonator 1031 and the first inductor 1025 are formed in series and connected to the ground
  • the other special parallel ground path is composed of a third resonator 1032 and a first inductor 1026 connected in series and connected to the ground, wherein the third resonator 1033 is connected in parallel. Connected to the third resonator 1032.
  • the third resonators 1031, 1032, 1033 have the same series resonant frequency as the first resonator, ie the first series resonant frequency f s1 , and the same parallel resonant frequency, ie the first parallel resonant frequency f p1 .
  • the first inductors 1025 and 1026 have a large inductance value, and are generally between 1 nH and 10 nH. The inductance values of the first inductors 1025 and 1026 may be the same or different.
  • auxiliary inductors 1021 and 1022 are added, and in order to connect the second resonators 1011, 1012, 1013, and 1014 to the ground, an auxiliary inductor 1023 is added, 1024, wherein one end of the second resonators 1011 and 1012 connected together is connected to the ground through the auxiliary inductor 1023, and the connected ends of the second resonators 1013 and 1014 are connected to the ground through the auxiliary inductor 1024.
  • the auxiliary inductor may be a bonding wire for connecting the chip to the package carrier, or a metal conductor for flip chip soldering on the package carrier, such as a copper pillar, a solder ball or the like.
  • the auxiliary inductors 1021, 1022, 1023, 1024 may also be referred to as second inductors, and the inductance values of the second inductors are generally in the range of 0.1 nH to 2 nH, such as 0.1 nH to 0.8 nH. That is, the inductance value of the first inductor is larger than the inductance value of the second inductor.
  • a third inductor 1027 for impedance matching is added near the input terminal 1041, and a resistor for impedance matching is added near the output terminal 1042.
  • the three inductors 1028, and the devices for impedance matching in the filter 1000 are similar to the impedance matching devices in the filter 200, and are not described herein again.
  • Fig. 16 is a graph showing the amplitude-frequency response of the insertion loss and the return loss of the filter 1000, wherein the graph (a) in Fig. 16 is the insertion loss curve of the filter wide band, and the graph (b) in Fig. 16 is the filter.
  • the passband insertion loss curve, Figure (c) in Figure 16 is the return loss curve of the filter input port, and Figure (d) in Figure 16 is the return loss curve of the filter output port.
  • the filter 1000 can be used as a filter of the Band 41, wherein the insertion loss of the filter 1000 in the pass band from 2496 MHz to 2690 MHz is less than 2.5 dB, and the out-of-band rejection at the WLAN (2402.5 MHz to 2481.5 MHz) is achieved - 40dB, the out-of-band rejection in LTE-Band 40 is at least -18dB.
  • the filter 1000 can improve the return loss while using the third resonators 1031, 1032, 1033 and the first inductors 1025, 1026 to increase the bandwidth, and improve the out-of-band of the low-frequency side of the pass band.
  • the filter 1000 can realize the expansion of the relative bandwidth of the filter by adding a special parallel grounding path without changing the electromechanical coupling coefficient of the resonator or changing the complexity of the manufacturing process. At the same time, it has better out-of-band rejection characteristics and achieves high performance requirements for piezoelectric filters.
  • the present invention proposes a circuit structure that is different from the traditional ladder structure.
  • filtering is implemented by adding a special parallel grounding path.
  • the relative bandwidth of the device is enlarged, and at the same time, it has better out-of-band rejection characteristics, achieving the high performance requirement for the piezoelectric filter.
  • the filter provided by the embodiment of the present invention has a bandwidth value exceeding at least 20% of the limit value of the conventional ladder structure, and the out-of-band rejection is not significantly deteriorated, especially the out-of-band rejection on the low-frequency side of the passband is not obvious. Deterioration.

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Abstract

一种梯形结构宽带压电滤波器，由一系列串联相接的第一谐振器，一系列并联相接的第二谐振器，位于滤波器输入端或输出端附近的阻抗匹配器件，以及至少一条由串联节点引出的特殊的并联接地通路组成。所述特殊的并联接地通路，至少包含一个电感值稍大的电感，同时包含一个与某串联支路谐振频率相同的谐振器或一个电容器，其中所述的大电感与所述的谐振器或电容器在并联通路上是串接的关系。本发明所提供的梯形滤波器结构，可以达到比传统梯型结构滤波器高至两倍以上带宽，同时还具有优秀的带外抑制特性。

Description

一种梯形结构宽带压电滤波器 技术领域
本发明涉及通信用滤波类器件领域，特别地，指利用压电效应原理制作的压电滤波器。
背景技术
随着无线通讯终端和设备市场的迅猛发展，无线通信频段划分也日益繁杂，多模、多频段成为当前无线通讯终端的主流发展趋势，在终端尺寸没有较大改变的情况下，对尺寸小、质量轻、性能高的高频滤波器的需求也越来越大。
目前，能够满足通讯终端使用的小尺寸中射频滤波器主要是压电声波滤波器，构成此类声波滤波器的谐振器主要包括：FBAR(Film Bulk Acoustic Resonator，薄膜体声波谐振器)，SMR(Solidly Mounted Resonator，固态装配谐振器)和SAW(Surface Acoustic Wave，表面声波谐振器)。利用谐振器设计滤波器电路的拓扑结构主要有梯形结构和网格状结构，前者主要用于单端口(un-balance)输入输出的滤波器，后者主要用于至少有一端是双端口/差分(balance)的滤波器。由于在射频链路中单端口的滤波器使用起来比较方便，因此在高性能声波滤波器和双工器的设计中，梯形结构的设计方法占据了主流地位。
图11(a)是压电声波谐振器的电学符号，图11(b)是其等效电学模型图，在不考虑损耗项的情况下，电学模型简化为Lm、Cm和C0组成的谐振电路。根据谐振条件可知，该谐振电路存在两个谐振频点：一个是谐振电路阻抗值达到最小值时的fs，将fs定义为该谐振器的串联谐振频点；另一个是当谐振电路阻抗值达到最大值时的fp，将fp定义为该谐振器的并联谐振频点。其中，
Figure PCTCN2016086596-appb-000001
并且，fs比fp要小。同时，定义了谐振器的有效机电耦合系数Kt2 eff，它可以用fs和fp来表示：
Figure PCTCN2016086596-appb-000002
图12示出了谐振器阻抗与fs和fp之间的关系。在某一特定的频率下，有效机电耦合系数越大，则fs和fp的频率差越大，即两个谐振频点离得越远。
图1是现有技术比较常见的梯形结构压电带通滤波器100的电路图。131为滤波器的输入端子，132为滤波器的输出端子。在131和132之间，有一系列位于串联通路位置、串联相接的第一谐振器101、102、103、104，这些第一谐振器具有第一串联谐振频率fs1和第一并联谐振频率fp1，以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器111、112、113，这些第二谐振器具有第二串联谐振频率fs2和第二并联谐振频率fp2；同时，为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器121和122，为了将第二谐振器连接到地，添加了辅助电感器123、124、125。这些辅助电感器可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等，它们的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。
图13(a)示出了上述现有技术的第一谐振器的第一串联谐振频率fs1和第一并联谐振频率fp1，以及第二谐振器的第二串联谐振频率fs2和第二并联谐振频率fp2之间的关系：fs1<fp1，fs2<fp2，并且，fs1近似等于fp2。对于FBAR或SMR来说，可以通过在第二谐振器上添加质量负载的方法，使得第一谐振器与第二谐振器满足上述频率特性；对于SAW来说，可以通过调整第一谐振器和第二谐振器换能器的交趾长度、间隙、分布、厚度等，使得第一谐振器与第二谐振器满足上述频率特性。
这样，对于该梯形结构滤波器100来说，存在三个比较有代表性的频率，下面用阻抗分压原理来说明，这三个比较特殊的频点如何构成压电带 通滤波器：当频率等于fp1时，位于串联位置的第一谐振器的阻抗达到极大值，位于并联位置的第二谐振器的阻抗远远低于第一谐振器的阻抗，从端子131流入的信号，绝大部分通过第二谐振器流到地上，无法到达端子132，滤波器100呈阻碍信号通过的特性；当频率等于fs1或fp2时，位于串联位置的第一谐振器的阻抗达到极小值，位于并联位置的第二谐振器的阻抗达到极大值，从端子131流入的信号，绝大部分通过第一谐振器流经串联通路到达端子132，滤波器100对信号呈导通特性；当频率等于fs2时，位于并联位置的第二谐振器的阻抗达到极小值，位于串联位置的第一谐振器的阻抗远远大于第二谐振器的阻抗，从端子131流入的信号，绝大部分通过第二谐振器流到地上，无法到达端子132，滤波器100呈阻碍信号通过的特性。
如果用类似的方法分析整个频段，那么就可以得到类似图13(b)，滤波器100的幅度-频率响应曲线，在fs2或fp1以外，是滤波器的阻带(stop band)，在fs1或fp2附近，是滤波器的通带(pass band)。
从上面的介绍可以看出，如100这样的梯形结构滤波器的带宽主要取决于其所包含的谐振器的串联谐振频率与并联谐振频率的差值，或者说，取决于其所包含谐振器的有效机电耦合系数，为了实现较宽带宽的滤波器，就要想办法提高谐振器的有效机电耦合系数。但是，机电耦合系数与多种因素相关，并不可以按用户的需要而无限制的提高。以氮化铝(AlN)为压电材料制作的FBAR谐振器举例，其有效机电耦合系数最高可达7.2％左右，可制作的带通滤波器相对带宽一般最高可达4.5％左右。
然而，某些通信频段为了满足高小区容量、大数据传输速率的要求，需要分配较宽的通信频段，例如根据3GPP协议所划分的第41频段(Band41)，其通带范围是从2496MHz到2690MHz，具有194MHz的带宽，相对带宽高达7.5％，同时又要求对其低频一侧的通信信号，如WLAN(2402.5MHz到2481.5MHz)，Band 40(2300MHz到2400MHz)等，有一定的抑制度。这时，再采用传统的提高机电耦合系数的方法来拓展滤波器的应用带宽已经不再有效，这就需要采取特殊的方法来实现这种高带宽，高抑制要求的带通滤波器。
发明内容
针对传统的通过提高机电耦合系数来拓展滤波器的应用带宽的方法无法满足所有方面的需要，本发明提供了一种具有提高的带宽的滤波器。
本发明的实施例提供了一种滤波器，其特征在于，包括：多个第一谐振器，所述多个第一谐振器串联连接；多个第二谐振器，每一个第二谐振器都连接在所述多个第一谐振器中的一个第一谐振器的一端和接地点之间；带宽调节单元，连接在所述多个第一谐振器中任意两个之间的节点和所述接地点之间；其中，所述第二谐振器的并联谐振频率低于所述第一谐振器的串联谐振频率。
根据本发明的一个实施例，所述带宽调节单元包含第三谐振器和第一电感器，所述第三谐振器与所述第一电感器串联连接。
根据本发明的一个实施例，所述带宽调节单元包含电容器和第一电感器，所述电容器与所述第一电感器串联连接。
根据本发明的一个实施例，所述带宽调节单元包含第一电感器。
根据本发明的一个实施例，所述第二谐振器与所述第一谐振器的串联谐振频率的差值为所述滤波器的通带带宽的30％-80％。
根据本发明的一个实施例，所述第三谐振器具有与所述第二谐振器不同的谐振频率。
根据本发明的一个实施例，所述第三谐振器具有与所述第一谐振器相同的谐振频率。
根据本发明的一个实施例，所述第三谐振器具有与所述第一谐振器相近的谐振频率。
根据本发明的一个实施例，所述带宽调节单元中的电容器利用半导体工艺集成在芯片上。
根据本发明的一个实施例，所述电容器为分立的电容器件，设置在芯片外部并且集成在封装载体中，所述封装载体包括所述芯片。
根据本发明的一个实施例，所述电容器的一端连接至所述节点，所述第一电感器的一端连接至所述接地点；或者所述电容器的一端连接至所述 接地点，所述第一电感器的一端连接至所述节点。
根据本发明的一个实施例，所述第一谐振器通过第二电感器与外部的信号端口连接；以及所述第二谐振器通过第三电感器与所述接地点连接。
根据本发明的一个实施例，所述第二电感器和所述第三电感器包括用于芯片与封装载体相连接的键合线、或者包括用于将所述芯片倒装焊接在所述封装载体上的金属导体。
根据本发明的一个实施例，所述第二电感器和所述第三电感器的电感值在0.1nH～2nH范围内。
根据本发明的一个实施例，其特征在于，还包括阻抗匹配器件，所述阻抗匹配器件连接在所述接地点和所述滤波器的输入端口或输出端口之间。
根据本发明的一个实施例，其特征在于，所述阻抗匹配器件为无源器件，所述无源器件包括电感器、电容器、传输线，所述无源器件的实现方式包括键合线、芯片集成无源器件(IPD)、封装载体上的集成或分立器件。
根据本发明的一个实施例，所述第一电感器的电感值在1nH～10nH的范围内。
根据本发明的一个实施例，所述滤波器中的谐振器包括具有空气隙的体声波压电谐振器(FBAR)、具有布拉格阻抗反射层的固态装配体声波压电谐振器(SMR)、或具有交趾换能结构的声表面波压电谐振器(SAW)。
本发明的滤波器在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
附图说明
附图用于更好地理解本发明，并不构成对本发明的不当限定。其中：
图1是目前单端口带通滤波器设计中通常采用的梯形结构原理图；
图2是本发明提出的一种在现有梯形结构滤波器基础上变化得到的宽带、高抑制的压电滤波器200的原理图；
图3是基于本发明的一个实施例300的原理图；
图4是基于本发明的又一个实施例400的原理图；
图5是基于本发明的又一个实施例500的原理图；
图6是基于本发明的又一个实施例600的原理图；
图7是基于本发明的又一个实施例700的原理图；
图8是基于本发明的又一个实施例800的原理图；
图9是基于本发明的又一个实施例900的原理图；
图10是基于本发明的又一个实施例1000的原理图；
图11(a)是压电声波谐振器的电学符号；
图11(b)是压电声波谐振器的等效电学模型图；
图12是谐振器阻抗与fs和fp之间的关系示意图；
图13(a)是现有技术梯形结构滤波器中谐振器谐振频率关系示意图；
图13(b)是现有技术梯形结构滤波器中滤波器曲线与谐振频率关系示意图；
图14是本发明提出的梯形结构宽带滤波器中谐振器谐振频率关系示意图；
图15是滤波器200的插入损耗和回波损耗的幅度-频率响应曲线图；
图16是滤波器1000的插入损耗和回波损耗的幅度-频率响应曲线图；
图17是滤波器400中谐振器谐振频率关系示意图；
图18是滤波器900中谐振器谐振频率关系示意图。
具体实施方式
针对现有技术制作宽带压电滤波器存在的问题，本发明提出了一种区别于传统梯形结构的电路结构，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。本发明的实施例提供的滤波器具有超出传统梯型结构极限带宽值至少20％以上的带宽值，并且带外抑制不会明显的恶化，特别是通带低频一侧的带外抑制不会明显的恶化。
图2是在图1梯形结构基础上改进的一种压电带通滤波器200的电路图。241为滤波器的输入端子，242为滤波器的输出端子，该输入和输出端 子为连接至滤波器的外部信号的端口。在输入端子241和输出端子242之间，有一系列位于串联通路位置上、串联相接的第一谐振器201、202、203、204，第一谐振器201、202、203、204具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点引出并且接地的第二谐振器211、212、213，其中，第二谐振器211的一端连接至第一谐振器201和第一谐振器202之间的节点；第二谐振器212的一端连接至第一谐振器202和第一谐振器203之间的节点；第二谐振器213的一端连接至第一谐振器203和第一谐振器204之间的节点。第二谐振器211、212、213具有第二串联谐振频率fs2和第二并联谐振频率fp2，第一谐振器和第二谐振器的谐振频率之间的关系由图14示出，其中fp2<fs1。
另外，滤波器200还包括带宽调节单元，并且该带宽调节单元包括特殊的并联接地通路，该特殊的并联接地通路从串联通路上的第一谐振器202和203相接的节点引出，该特殊的并联接地通路由一个第三谐振器231和第一电感器226串联组成并连接到接地点。第三谐振器231具有与第一谐振器相同的串联谐振频率，即第一串联谐振频率fs1，和相同的并联谐振频率，即第一并联谐振频率fp1。第一电感器226具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器221和222，为了将第二谐振器连接到地(其中，本发明中的“地”也可以称为“接地点”)，添加了辅助电感器223、224、225。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器221、222、223、224、225也可称为第二电感器，该第二电感器的电感值一般在0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值比第二电感器的电感值大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子241附近添加了用于阻抗匹配的第三电感器227，在靠近输出端子242附近添加了用于阻抗匹配的第三电感器228。其中，用于阻抗匹配的阻抗匹配器件不限于电感器，其还可以包括其他无源器件，诸如电容器、传输线等，并且无源器件的实现方式包括但不限于键合线、芯片集成无源器件(IPD)、封装载体集成、分立器件等。
图15是滤波器200的插入损耗和回波损耗的幅度-频率响应曲线图，其中图15中的图(a)是滤波器宽频带的插入损耗曲线，图15中的图(b)是滤波器通带插入损耗的曲线，图15中的图(c)是滤波器输入端口的回波损耗曲线，图15中的图(d)是滤波器输出端口的回波损耗曲线。该滤波器的中心频点为2GHz，3dB带宽达到了124MHz，相对带宽达到6.25％。而如果采用同样的谐振器和传统的梯形电路结构，只能做到3dB带宽70MHz，即相对带宽为4％左右。相比之下，滤波器200在利用第三谐振器231和第一电感器226增加了带宽的同时，回波损耗仍能保持优于-10dB，通带低频侧的带外抑制都达到了33dB以上，并没有明显的恶化，既满足宽带通信的要求，同时对通带外干扰信号起到较好的抑制。从而利用本发明的滤波器200，使得带外抑制不会明显的恶化，特别是通带低频一侧的带外抑制不会明显的恶化。
基于本发明的一个实施例的滤波器200，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。本发明的实施例提供的滤波器具有超出传统梯型结构极限带宽值至少20％以上的带宽值，并且带外抑制不会明显的恶化，特别是通带低频一侧的带外抑制不会明显的恶化。
图3是基于本发明的一个实施例300的原理图。341为滤波器的输入端子，342为滤波器的输出端子。在输入端子341和输出端子342之间，有一系列位于串联通路位置上、串联相接的第一谐振器301、302、303、304、305、306，第一谐振器301、302、303、304、305、306具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器311、312、313、314，其中，第二谐振器311的一端连接至第一谐振器301和302之间的节点；第二谐振器312和313的一端连接在一起并且连接至第一谐振器303和304之间的节点；第二谐振器314的一端连接至第一谐振器305和306之间的节点。第二谐振器311、312、313、314具有第二串联谐振频率fs2和第二并联谐振频率fp2，第一谐振器和第二谐振器的谐振频率之间的关系可以参考图14， 其中fp2<fs1。
另外，滤波器300还包括带宽调节单元，并且该带宽调节单元包括特殊的并联接地通路，该特殊的并联接地通路从串联通路上的第一谐振器303和304相接的节点引出，该特殊的并联接地通路由一个第三谐振器331和第一电感器326串联组成并连接到地。第三谐振器331具有与第一谐振器相同的串联谐振频率，即第一串联谐振频率fs1，和相同的并联谐振频率，即第一并联谐振频率fp1。第一电感器326具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器321和322，为了将第二谐振器连接到地，添加了辅助电感器323、324、325，其中第二谐振器312和313的另一端连接在一起并且通过辅助电感器324连接到地。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器321、322、323、324、325也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子341附近添加了用于阻抗匹配的第三电感器327，在靠近输出端子342附近添加了用于阻抗匹配的第三电感器328，并且滤波器300中的用于阻抗匹配的器件与滤波器200中的阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器300，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图4是基于本发明的又一个实施例400的原理图。441为滤波器的输入端子，442为滤波器的输出端子。在输入端子441和输出端子442之间，有一系列位于串联通路位置上、串联相接的第一谐振器401、404和第三谐振器402、403，并且第三谐振器402和403串联连接在第一谐振器401和404之间，第一谐振器401、404具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接 地的第二谐振器411、412、413，其中，第二谐振器411的一端连接至第一谐振器401和第三谐振器402之间的节点；第二谐振器412的一端连接至第三谐振器402和403之间的节点；第二谐振器413的一端连接至第三谐振器403和第一谐振器404之间的节点。第二谐振器411、412、413具有第二串联谐振频率fs2和第二并联谐振频率fp2。
另外，滤波器400还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路，该特殊的并联接地通路从串联通路上的第三谐振器402和403相接的节点处引出，其中，该特殊的并联接地通路由一个第三谐振器431和第一电感器426串联组成并连接到地。第三谐振器402、403、431具有第三串联谐振频率fs3和第三并联谐振频率fp3。第一谐振器、第二谐振器和第三谐振器的谐振频率之间的关系由图17示出，其中fp2<fs3<fs1。第一电感器426具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器421和422，为了将第二谐振器连接到地，添加了辅助电感器423、424、425。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器421、422、423、424、425也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子441附近添加了用于阻抗匹配的第三电感器427，在靠近输出端子442附近添加了用于阻抗匹配的第三电感器428，其中，第三电感器427和428位于输入端子和输出端子附近，而不是直接连接至输入端子和输出端子，具体而言，第三电感器427和428连接至谐振器，并且第三电感器427和428可以是集成芯片上的无源器件，诸如IPD。并且基于本发明的一个实施例的滤波器400，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图5是基于本发明的又一个实施例500的原理图。541为滤波器的输 入端子，542为滤波器的输出端子。在输入端子541和输出端子542之间，有一系列位于串联通路位置上、串联相接的第一谐振器501、502、503、504，第一谐振器501、502、503、504具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器511、512、513，第二谐振器511、512、513具有第二串联谐振频率fs2和第二并联谐振频率fp2，第一谐振器和第二谐振器的谐振频率之间的关系可以参考图14，其中fp2<fs1。其中，第二谐振器511的一端连接至第一谐振器501和502之间的节点；第二谐振器512的一端连接至第一谐振器502和503之间的节点，第三谐振器513的一端连接至第一谐振器503和504之间的节点。
另外，滤波器500还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第一谐振器502和503相接的节点处引出，并且该特殊的并联接地通路由一个电容器531和第一电感器526串联组成并连接到地。电容器531可以利用半导体工艺集成在芯片上，并且电容器531可以独立于芯片，如采用分立的电容器件、或利用其它工艺集成在封装载体中。特殊的并联接地通路中信号流经电容器531和第一电感器526的顺序是可以互换的。第一电感器526具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器521和522，为了将第二谐振器连接到地，添加了辅助电感器523、524、525。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器521、522、523、524、525也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子541附近添加了用于阻抗匹配的第三电感器527，在靠近输出端子542附近添加了用于阻抗匹配的第三电感器528，并且滤波器500中的用于阻抗匹配的器件与滤波器200中的阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器500，在不改变谐振器机电耦合系数， 也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图6是基于本发明的又一个实施例600的原理图。641为滤波器的输入端子，642为滤波器的输出端子。在输入端子641和输出端子642之间，有一系列位于串联通路位置、串联相接的第一谐振器601、602、603、604，第一谐振器601、602、603、604具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器611和612，第二谐振器611和612具有第二串联谐振频率fs2和第二并联谐振频率fp2，第一谐振器和第二谐振器的谐振频率之间的关系可以参考图14，其中fp2<fs1。其中，第二谐振器611的一端连接至第一谐振器601和602之间的节点，并且第二谐振器612的一端连接至第一谐振器603和604之间的节点。
另外，滤波器600还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第一谐振器602和603相接的节点处引出，并且该特殊的并联接地通路由一个第三谐振器631和第一电感器625串联组成并连接到地。第三谐振器631具有与第一谐振器相同的串联谐振频率，即第一串联谐振频率fs1，和相同的并联谐振频率，即第一并联谐振频率fp1。第一电感器625具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器621和622，为了将第二谐振器连接到地，添加了辅助电感器623、624。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器621、622、623、624也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子641附近添加了用于阻抗匹配的第三电感器626，在靠近输出端子642附近添加了用于阻抗匹配的第三电感器627，并且滤波器600中的用于阻抗匹配的器件与滤波器200中的 阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器600，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图7是基于本发明的又一个实施例700的原理图。741为滤波器的输入端子，742为滤波器的输出端子。在输入端子741和输出端子742之间，有一系列位于串联通路位置上、串联相接的第一谐振器701、702、703、704，第一谐振器701、702、703、704具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器711、712、713，第二谐振器711、712、713具有第二串联谐振频率fs2和第二并联谐振频率fp2，第一谐振器和第二谐振器的谐振频率之间的关系可以参考图14，其中fp2<fs1。其中，第二谐振器711的一端连接至第一谐振器701和702之间的节点，第二谐振器712的一端连接至第一谐振器702和703之间的节点，以及第二谐振器713的一端连接至第一谐振器703和704之间的节点。
另外，滤波器700还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第一谐振器702和703相接的节点处引出，并且该特殊的并联接地通路包括第一电感器726并连接到地。第一电感器726具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器721和722，为了将第二谐振器连接到地，添加了辅助电感器723、724、725。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器721、722、723、724、725也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子741附近添加了用于阻抗匹配的第三电感器727，在靠近输出端子742附近添加了用于阻抗匹配的第三电感器728，并且滤波器700中的用于阻抗匹配的器件与滤波器200中 的阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器700，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图8是基于本发明的又一个实施例800的原理图。841为滤波器的输入端子，842为滤波器的输出端子。在输入端子841和输出端子842之间，有一系列位于串联通路位置、串联相接的第一谐振器801、805和第三谐振器802、803、804，并且第三谐振器802、803、804串联连接在第一谐振器801和805之间，第一谐振器801、805具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器811、812、813、814，第二谐振器811、812、813、814具有第二串联谐振频率fs2和第二并联谐振频率fp2。其中，第二谐振器811的一端连接至第一谐振器801和第三谐振器802之间的节点；第二谐振器812的一端连接至第三谐振器802和803之间的节点；第二谐振器813的一端连接至第三谐振器803和804之间的节点；以及第二谐振器814的一端连接至第三谐振器804和第一谐振器805之间的节点。
另外，滤波器800还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第三谐振器802和803相接的节点以及第三谐振器803和804相接的节点处引出，其中一条特殊的并联接地通路由一个第三谐振器831和第一电感器827串联组成并连接到地，另一条特殊的并联接地通路由一个第三谐振器832和第一电感器828串联组成并连接到地。第三谐振器802、803、804、831、832具有第三串联谐振频率fs3和第三并联谐振频率fp3。第一谐振器、第二谐振器和第三谐振器的谐振频率之间的关系可以参考图17，其中fp2<fs3<fs1。第一电感器827、828具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器821和822，为了将第二谐振器连接到地，添加了辅助电感器823、824、825、826。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器 821、822、823、824、825、826也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子841附近添加了用于阻抗匹配的第三电感器829，在靠近输出端子842附近添加了用于阻抗匹配的第三电感器830，并且滤波器800中的用于阻抗匹配的器件与滤波器200中的阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器800，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图9是基于本发明的又一个实施例900的原理图。941为滤波器的输入端子，942为滤波器的输出端子。在输入端子941和输出端子942之间，有一系列位于串联通路位置上、串联相接的第一谐振器901、902、903、904、905，第一谐振器901、902、903、904、905具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器912、913和第三谐振器911、914，第二谐振器912、913具有第二串联谐振频率fs2和第二并联谐振频率fp2。另外，第三谐振器906、907分别与第一谐振器901、905并联连接，并且第三谐振器906、907、911、914具有第三串联谐振频率fs3和第三并联谐振频率fp3。第一谐振器、第二谐振器和第三谐振器的谐振频率之间的关系由图18示出，其中fp2<fp3<fs1。其中，第三谐振器911的一端连接至第一谐振器901和902之间的节点，第二谐振器912的一端连接至第一谐振器902和903之间的节点，第二谐振器913的一端连接至第一谐振器903和904之间的节点，以及第三谐振器914的一端连接至第一谐振器904和905之间的节点。
另外，滤波器900还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第一谐振器902和903相接的节点以及第一谐振器903和904相接的节点处引出，其中一条特殊的并联接地通路由一个电容器931和第一电感器927串联组 成并连接到地，另一条特殊的并联接地通路由一个电容器932和第一电感器928串联组成并连接到地。电容器931、932可以利用半导体工艺集成在芯片上，并且电容器931、932可以独立于芯片，如采用分立的电容器件、或利用其它工艺集成在封装载体中。特殊的并联接地通路中信号流经电容器931和第一电感器927的顺序以及流经电容器932和第一电感器928的顺序是可以互换的。第一电感器927、928具有较大的电感值，一般位于1nH～10nH之间。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器921和922，为了将第二谐振器912、913和第三谐振器911、914连接到地，添加了辅助电感器923、924、925、926。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器921、922、923、924、925、926也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子941附近添加了用于阻抗匹配的第三电感器929，在靠近输出端子942附近添加了用于阻抗匹配的第三电感器930，并且滤波器900中的用于阻抗匹配的器件与滤波器200中的阻抗匹配器件类似，在此不再赘述。并且基于本发明的一个实施例的滤波器900，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
图10是基于本发明的又一个实施例1000的原理图。1041为滤波器的输入端子，1042为滤波器的输出端子。在输入端子1041和输出端子1042之间，有一系列位于串联通路位置上、串联相接的第一谐振器1001、1003、1004、1005、1006，第一谐振器1001、1003、1004、1005、1006具有第一串联谐振频率fs1和第一并联谐振频率fp1；以及一系列位于并联通路位置、从串联通路上的某些节点并联接地的第二谐振器1011、1012、1013、1014，第二谐振器1011、1012、1013、1014具有第二串联谐振频率fs2和第二并联谐振频率fp2。其中，第二谐振器1011的一端连接至第一谐振器1001和 1003之间的节点，第二谐振器1012的一端连接至第一谐振器1003和1004之间的节点，第二谐振器1013的一端连接至第一谐振器1004和1005之间的节点，以及第二谐振器1014的一端连接至第一谐振器1005和1006之间的节点，并且其中，第二谐振器1011和1012的另一端连接在一起，第二谐振器1013和1014的另一端连接在一起。另外，第一谐振器1002、1007分别与第一谐振器1001、1006并联连接，并且第一谐振器1002、1007也具有第一串联谐振频率fs1和第一并联谐振频率fp1，第一谐振器和第二谐振器的谐振频率之间的关系可以参考图14，其中fp2<fs1。
另外，滤波器1000还包括带宽调节单元，并且带宽调节单元包括特殊的并联接地通路。其中，该特殊的并联接地通路从串联通路上的第一谐振器1003和1004相接的节点以及第一谐振器1004和1005相接的节点处引出，其中一条特殊的并联接地通路由一个第三谐振器1031和第一电感器1025串联组成并连接到地，另一条特殊的并联接地通路由一个第三谐振器1032和第一电感器1026串联组成并连接到地，其中第三谐振器1033并联连接至第三谐振器1032。第三谐振器1031、1032、1033具有与第一谐振器相同的串联谐振频率，即第一串联谐振频率fs1，和相同的并联谐振频率，即第一并联谐振频率fp1。第一电感器1025、1026具有较大的电感值，一般位于1nH～10nH之间，其中，第一电感器1025和1026的电感值可以相同也可以不同。为了将第一谐振器与滤波器的输入、输出端子相接，添加了辅助电感器1021和1022，为了将第二谐振器1011、1012、1013、1014连接到地，添加了辅助电感器1023、1024，其中第二谐振器1011和1012的连接在一起的一端通过辅助电感器1023连接到地，第二谐振器1013和1014的连接在一起的一端通过辅助电感器1024连接到地。上述辅助电感可以是用于芯片与封装载体相连接的键合线，也可以是用于将芯片倒装焊接在封装载体上的金属导体，如铜柱、锡球等。辅助电感器1021、1022、1023、1024也可称为第二电感器，该第二电感器的电感值一般位于0.1nH～2nH范围内，诸如0.1nH～0.8nH。即第一电感器的电感值相比第二电感器的电感值较大。为了使滤波器在通带范围内都能达到较好的特性，在靠近输入端子1041附近添加了用于阻抗匹配的第三电感器1027，在靠近 输出端子1042附近添加了用于阻抗匹配的第三电感器1028，并且滤波器1000中的用于阻抗匹配的器件与滤波器200中的阻抗匹配器件类似，在此不再赘述。
图16是滤波器1000的插入损耗和回波损耗的幅度-频率响应曲线图，其中图16中的图(a)是滤波器宽频带的插入损耗曲线，图16中的图(b)是滤波器通带插入损耗的曲线，图16中的图(c)是滤波器输入端口的回波损耗曲线，图16中的图(d)是滤波器输出端口的回波损耗曲线。根据实施例，滤波器1000可以作为Band 41的滤波器，其中，滤波器1000在通带2496MHz～2690MHz内的插损小于2.5dB，同时在WLAN(2402.5MHz～2481.5MHz)的带外抑制达到-40dB，在LTE-Band 40的带外抑制至少为-18dB。从图中可知，滤波器1000在利用第三谐振器1031、1032、1033和第一电感器1025、1026增加了带宽的同时，仍能改善回波损耗，并且改善了通带低频侧的带外抑制，既满足宽带通信的要求，同时对通带外干扰信号起到较好的抑制。并且基于本发明的一个实施例的滤波器1000，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。
根据各个实施例，本发明提出了一种区别于传统梯形结构的电路结构，在不改变谐振器机电耦合系数，也不改变制作工艺复杂度的前提下，通过添加特殊的并联接地通路，实现滤波器相对带宽的扩大化，同时具有较好的带外抑制特性，达到对压电滤波器的高性能要求。本发明的实施例提供的滤波器具有超出传统梯型结构极限带宽值至少20％以上的带宽值，并且带外抑制不会明显的恶化，特别是通带低频一侧的带外抑制不会明显的恶化。
此外，本发明中出现的“近似”、“相近”、“大约”等是指在本领域技术人员所公认的误差范围内。
上面论述了若干实施例的部件，使得本领域普通技术人员可以更好地理解本发明的各个方面。本领域普通技术人员应该理解，可以很容易地使用本发明作为基础来设计或更改其他用于达到与这里所介绍实施例相同的 目的和/或实现相同优点的处理和结构。本领域普通技术人员也应该意识到，这种等效构造并不背离本发明的精神和范围，并且在不背离本发明的精神和范围的情况下，可以进行多种变化、替换以及改变。

Claims (18)

  1. 一种滤波器，其特征在于，包括：
    多个第一谐振器，所述多个第一谐振器串联连接；
    多个第二谐振器，每一个第二谐振器都连接在所述多个第一谐振器中的一个第一谐振器的一端和接地点之间；
    带宽调节单元，连接在所述多个第一谐振器中任意两个之间的节点和所述接地点之间；
    其中，所述第二谐振器的并联谐振频率低于所述第一谐振器的串联谐振频率。
  2. 根据权利要求1所述的滤波器，其特征在于，所述带宽调节单元包含第三谐振器和第一电感器，所述第三谐振器与所述第一电感器串联连接。
  3. 根据权利要求1所述的滤波器，其特征在于，所述带宽调节单元包含电容器和第一电感器，所述电容器与所述第一电感器串联连接。
  4. 根据权利要求1所述的滤波器，其特征在于，所述带宽调节单元包含第一电感器。
  5. 根据权利要求1所述的滤波器，其特征在于，所述第二谐振器与所述第一谐振器的串联谐振频率的差值为所述滤波器的通带带宽的30％-80％。
  6. 根据权利要求2所述的滤波器，其特征在于，所述第三谐振器具有与所述第二谐振器不同的谐振频率。
  7. 根据权利要求6所述的滤波器，其特征在于，所述第三谐振器具有与所述第一谐振器相同的谐振频率。
  8. 根据权利要求6所述的滤波器，其特征在于，所述第三谐振器具有与所述第一谐振器相近的谐振频率。
  9. 根据权利要求3所述的滤波器，其特征在于，所述电容器利用半导体工艺集成在芯片上。
  10. 根据权利要求3所述的滤波器，其特征在于，所述电容器为分立的电容器件，设置在芯片外部并且集成在封装载体中，所述封装载体包括所述芯片。
  11. 根据权利要求3所述的滤波器，其特征在于，所述电容器的一端连接至所述节点，所述第一电感器的一端连接至所述接地点；或者所述电容器的一端连接至所述接地点，所述第一电感器的一端连接至所述节点。
  12. 根据权利要求1所述的滤波器，其特征在于，
    所述第一谐振器通过第二电感器与外部的信号端口连接；以及
    所述第二谐振器通过第三电感器与所述接地点连接。
  13. 根据权利要求12所述的滤波器，其特征在于，所述第二电感器和所述第三电感器包括用于芯片与封装载体相连接的键合线、或者包括用于将所述芯片倒装焊接在所述封装载体上的金属导体。
  14. 根据权利要求13所述的滤波器，其特征在于，所述第二电感器和所述第三电感器的电感值在0.1nH～2nH范围内。
  15. 根据权利要求1所述的滤波器，其特征在于，还包括阻抗匹配器件，所述阻抗匹配器件连接在所述接地点和所述滤波器的输入端口或输出端口之间。
  16. 根据权利要求15所述的滤波器，其特征在于，所述阻抗匹配器件为无源器件，所述无源器件包括电感器、电容器、传输线，所述无源器件的实现方式包括键合线、芯片集成无源器件(IPD)、封装载体上的集成或分立器件。
  17. 根据权利要求2-4中任一权利要求所述的滤波器，其特征在于，所述第一电感器的电感值在1nH～10nH的范围内。
  18. 根据权利要求17所述的滤波器，其特征在于，所述滤波器中的谐振器包括具有空气隙的体声波压电谐振器(FBAR)、具有布拉格阻抗反射层的固态装配体声波压电谐振器(SMR)、或具有交趾换能结构的声表面波压电谐振器(SAW)。
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