JP2021190908A - Band rejection filter, composite filter, and communication device - Google Patents

Abstract

To provide a band rejection filter that can easily make the inclination of attenuation steep at the boundary between a pass band and a rejection band.SOLUTION: A band rejection (BE) filter 7 has an elastic wave chip 33 and a substrate structure 53. The elastic wave chip 33 has an elastic wave resonator 15. The substrate structure 53 has a circuit board. A conductor of the circuit board forms a first inductor and a second inductor. The elastic wave chip 33 and the substrate structure 53 form an elastic wave filter 11 and a notch filter 13. The elastic wave filter 11 has a serial resonator 15S forming part of a signal path 9 and the first inductor, and attenuates a signal in a rejection path. The notch filter 13 has the second inductor. An anti-resonance frequency fsa of the serial resonator 15S is located between the resonance frequency fnr of the notch filter 13 and a pass band XB.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a band blocking filter that attenuates a component of a signal having a frequency within a predetermined blocking band, a composite filter including the band blocking filter, and a communication device including the composite filter.

As a bandpass filter, a filter having an elastic wave filter composed of a conductor of a circuit board and an elastic wave filter composed of an elastic wave chip mounted on the circuit board is known (for example, Patent Document 1 below). Surface acoustic waves are, for example, SAW (Surface Acoustic Wave) and BAW (Bulk Acoustic Wave). As is known, a bandpass filter passes a component of an electric signal having a frequency within a predetermined passband (attenuates a component having a frequency outside the passband). Although not particularly exemplified in the literature, a band blocking filter that attenuates a component having a frequency within a predetermined blocking band among electric signals is also known.

Japanese Unexamined Patent Publication No. 2001-102807

Bandwidth blocking filters, compound filters and communication devices that can easily steep the slope of attenuation at the boundary between the passband and the blocking band are awaited.

The band-stop filter according to one aspect of the present disclosure has a pass band and a block band located on the low frequency side or the high frequency side with respect to the pass band, and among the signals flowing in the signal path, the above-mentioned A band-stop filter that attenuates a component having a frequency within the blocking band, and has one or more elastic wave resonators, and each of the one or more elastic wave resonators has a resonance frequency and an anti-resonance frequency. An elastic wave chip and a board structure having one or more circuit boards, wherein one or more first inductors and one or more second inductors are configured by the conductors of the one or more circuit boards. An elastic wave filter that attenuates a component having a frequency within at least a part of the blocking band among the signals flowing in the signal path by the elastic wave chip and the substrate structure. A notch filter that connects the signal path and the reference potential portion and has a resonance frequency at which the impedance between the signal path and the reference potential portion becomes the minimum value is configured, and the elasticity thereof. The wave filter has one or more series resonators constituting a part of the signal path, and one or more first inductors, which are included in the one or more elastic wave resonators. The notch filter has one or more second inductors, and the anti-resonance frequency of at least one of the one or more series resonators is between the resonance frequency of the notch filter and the pass band. Is located in.

The composite filter according to one aspect of the present disclosure has the band blocking filter and a second pass band adjacent to the pass band side of the band blocking filter with respect to the blocking band, and flows through the signal path. It has a bandpass filter that attenuates a component having a frequency outside the second pass band of the signal.

The communication device according to one aspect of the present disclosure includes the composite filter, an antenna electrically connected to one of the input side and the output side of the composite filter, and the input side and the output of the composite filter. It has an integrated circuit element that is electrically connected to the other side.

According to the above configuration, it is easy to steep the slope of attenuation at the boundary between the pass band and the blocking band.

1 (a) is a block diagram schematically showing the configuration of the composite filter according to the embodiment, and FIGS. 1 (b) and 1 (c) are for explaining the characteristics of the composite filter of FIG. 1 (a). It is a figure of. 2 (a) is a block diagram schematically showing the configuration of the band blocking filter included in the composite filter of FIG. 1 (a), and FIG. 2 (b) illustrates the characteristics of the band blocking filter of FIG. 2 (a). It is a figure to do. It is a circuit diagram which shows the structure of the composite filter which concerns on 1st Embodiment. 4 (a) and 4 (b) are schematic cross-sectional views showing the first example and the second example of the structure of the composite filter according to the embodiment. It is a top view schematically showing the structural example of the elastic wave resonator included in the composite filter which concerns on embodiment. It is a circuit diagram which shows the structure of the composite filter which concerns on 2nd Embodiment. It is a circuit diagram which shows the structure of the composite filter which concerns on 3rd Embodiment. It is a circuit diagram which shows the structure of the composite filter which concerns on a comparative example. FIG. 9A is a diagram showing the characteristics of the bandpass filter included in the composite filter according to the embodiment, and FIG. 9B is a diagram showing the characteristics of the composite filter according to the comparative example. 10 (a) and 10 (b) are diagrams showing examples of the characteristics of the composite filter according to the first and second embodiments. It is a figure which shows the example of the characteristic of the composite filter which concerns on 3rd Embodiment. 12 (a) and 12 (b) are diagrams showing an example of the characteristics of the notch filter included in the composite filter according to the embodiment and other examples. 13 (a) and 13 (b) are diagrams showing the characteristics of the composite filter according to the fourth embodiment. It is a block diagram which shows the main part of the communication apparatus which concerns on embodiment. 15 (a) and 15 (b) are circuit diagrams showing modified examples of the notch filter, respectively.

Hereinafter, a plurality of embodiments according to the present disclosure will be described with reference to the drawings. After the description of the first embodiment, basically, only the differences from the previously described embodiments will be described. Matters not specifically mentioned may be the same as those described above. Further, with respect to the configuration corresponding to the configuration of the embodiment described above, the same reference numerals may be used even if there are differences.

<First Embodiment>
(Composite filter)
FIG. 1A is a block diagram schematically showing the configuration of the composite filter 1 according to the embodiment.

The composite filter 1 is configured as, for example, a bandpass filter that outputs a component (an electric signal from another viewpoint) having a frequency within a predetermined pass band among the electric signals input to the input terminal 3A from the output terminal 3B. There is. From another aspect, the composite filter 1 attenuates a component having a frequency outside the pass band among the electric signals flowing through the signal path 9 from the input terminal 3A to the output terminal 3B. The input terminal 3A and the output terminal 3B may be regarded as a part of the composite filter 1 or may be regarded as a member separate from the composite filter 1.

The composite filter 1 is a bandpass filter 5 (hereinafter, may be abbreviated as “BP filter 5”) and a band blocking filter 7 (hereinafter, abbreviated as “BE filter 7”) which are sequentially located on the signal path 9. There is.). The order of the BP filter 5 and the BE filter 7 from the input terminal 3A side to the output terminal 3B side may be reversed from the illustrated example.

In the description of the present disclosure, with respect to the various filters, in the case where the filter is located on the signal path 9, or in the case where a schematic block diagram is shown in an manner in line with such textual representation. The more detailed configuration of the filter may not match such textual representations and / or schematic block diagrams. For example, when focusing on a more detailed configuration, the filter may be in a mode constituting a part of the signal path 9 (a mode as expressed), or an unnecessary signal from the signal path 9 may be used as a reference potential. It may be connected between the signal path 9 and the reference potential portion so as to escape to the portion 17 (see FIG. 2A), or may be a combination of both.

The composite filter 1 may have a configuration other than that shown in the figure. For example, the composite filter 1 may include a filter other than the BP filter 5 and the band blocking filter 7, and may include elements such as a resistor, an inductor and / or a capacitor. From another point of view, the composite filter 1 may include not only a configuration for filtering but also a configuration for other purposes such as impedance matching. Unless otherwise specified, various filters (5, 7, 11, 13, etc.) in the composite filter 1 may be provided with configurations other than those shown in the above. The reference potential portion 17 is a conductor to which a reference potential is applied. As the reference potential, 0 V can be typically exemplified, but the reference potential is not limited to this.

FIG. 1B is a diagram showing the filter characteristics of the BP filter 5 and the BE filter 7.

In this figure, the horizontal axis f (Hz) indicates the frequency, and the frequency is higher toward the right side of the paper. The vertical axis A (dB) shows the amount of attenuation, and the amount of attenuation is larger toward the lower side of the paper. The amount of attenuation is usually represented by a negative value. In the description of the embodiment, the expression that the amount of attenuation is large or small basically means that the absolute value of the amount of attenuation is large or small. The line LP shows the characteristics of the BP filter 5. The line LE shows the characteristics of the BE filter 7.

The BP filter 5 is configured to pass a signal having a frequency within the pass band PB. That is, the attenuation of the BP filter 5 is small in the pass band PB and large outside the pass band PB. Further, the BE filter 7 is configured to attenuate a signal having a frequency within the blocking band EB. That is, the attenuation of the BE filter 7 is large in the blocking band EB and small outside the blocking band EB.

Although not particularly designated, in the line LP, the band in which the attenuation amount on both sides of the pass band PB changes is the transition band of the BP filter 5. The band having a large attenuation amount outside the transition band (the side away from the pass band PB) is the blocking band of the BP filter 5. In the line LE, the band in which the attenuation amount on both sides of the blocking band EB changes is the transition band of the BE filter 7. The band having a smaller attenuation amount outside the transition band (the side away from the blocking band EB) is the pass band of the BE filter 7. Of the two pass bands of the BE filter 7, the pass band of the BP filter 5 on the PB side (high frequency side in this embodiment) is referred to as a pass band XB. The upper limit frequency of the pass band XB on the high frequency side is theoretically infinite. The lower limit frequency of the pass band (sign omitted) on the low frequency side of the BE filter 7 is theoretically 0.

The blocking band EB of the BE filter 7 is adjacent to the low frequency side of the pass band PB of the BP filter 5, for example. The bandwidth of the passband PB is, for example, wider than the bandwidth of the blocking band EB. Further, in the BP filter 5, the rate of change in the amount of attenuation in the transition band (only the absolute value is focused on; the same applies hereinafter) is smaller than the rate of change in the amount of attenuation in the transition band of the BE filter 7. In other words, the slope of the line LP on both sides of the passband PB is gentler than the slope of the line LE on both sides of the blocking band EB. It should be noted that such an inclination is referred to as an attenuation inclination.

In general, when trying to secure a wide pass band PB or stop band EB, the slope of attenuation in the transition band becomes gentle. In the illustrated example, the BP filter 5 is configured to have a relatively wide passband PB, resulting in a gentle slope of attenuation on both sides of the passband PB. On the other hand, it is usually said that the steeper the slope of attenuation in the transition band, the better the filter characteristics.

FIG. 1 (c) is a diagram showing the filter characteristics of the composite filter 1.

In this figure, the horizontal axis and the vertical axis are the same as the horizontal axis and the vertical axis of FIG. 1 (b), and the scale thereof is also the same as that of FIG. 1 (b). The line LC in the figure shows the filter characteristics of the composite filter 1.

The filter characteristic of the composite filter 1 is, for example, the filter characteristic of the BP filter 5 having a steep slope of attenuation on the low frequency side of the pass band PB. The slope of the attenuation is substantially the same as the slope of the attenuation on the high frequency side of the blocking band EB of the BE filter 7. By combining the BP filter 5 and the BE filter 7 in this way, for example, it is possible to obtain a composite filter 1 having a relatively wide pass band CB and having a steep attenuation gradient on the low frequency side of the pass band CB. can.

In the products and the like on the market, the pass band (for example, PB, XB and CB) and the blocking band (for example, EB) may be appropriately specified. For example, it may be specified by a specification or by measuring the filter characteristics of a product. The amount of attenuation required for the pass band and the stop band differs depending on the device to which the composite filter 1 is applied and the like. As an example, a frequency band in which the absolute value of the attenuation is 5 dB or less or 3 dB or less may be specified as a pass band. Further, as an example, a frequency band in which the absolute value of the attenuation amount is 30 dB or more may be specified as a blocking band.

Specific values such as the bandwidth and center frequency of the pass band CB and PB and the blocking band EB are arbitrary. The center frequency is the center frequency between the lower limit frequency of the band and the upper limit frequency of the band (an average value of the two from another viewpoint). An example of the range of the center frequency of the pass band CB or PB is 500 MHz or more and 30 GHz or less. Further, the pass band CB or PB may be set according to an appropriate communication standard. In this case, the pass band CB or PB may correspond to only one band defined by the standard, or may include two or more bands defined by the standard.

As described above, the blocking band EB of the BE filter 7 is adjacent to the pass band PB of the BP filter 5 (from another viewpoint, the pass band CB of the composite filter 1). Adjacent here is, for example, at least a part of the transition band of the pass band PB side (high frequency side in this embodiment) of the BE filter 7 and the blocking band EB side (low frequency side in this embodiment) of the BP filter 5. ) May overlap with at least a part of the transition band. Further, the adjacency may be such that at least a part of the blocking band EB overlaps with at least a part of the transition band on the blocking band EB side of the BP filter 5. Paradoxically, in the adjacency, the slope of the attenuation of the composite filter 1 in the transition band on the blocking band EB side is larger than the slope of the attenuation of the BP filter 5 in the transition band on the blocking band EB side by the BE filter 7. It may be said that it is steep.

In the illustrated example, the frequency of the transition band on the pass band PB side of the BE filter 7 on the end of the pass band PB (from another point of view, the end of the pass band XB on the blocking band EB side) and the pass band PB. It coincides with the frequency at the end of the blocking band EB side. However, unlike the illustrated example, a part or all of the transition band on the pass band PB side of the BE filter 7 may overlap with a part of the pass band PB. On the contrary, the transition band on the pass band PB side of the BE filter 7 and the pass band PB may be separated from each other.

In the illustrated example, the frequency of the end portion of the pass band EB on the pass band PB side (high frequency side in this embodiment) is separated from the frequency of the end portion of the pass band PB on the stop band EB side. However, unlike the illustrated example, the two may be the same. Further, the blocking band EB and the passing band PB may partially overlap each other.

In the illustrated example, the pass band CB of the composite filter 1 and the pass band PB of the BP filter 5 match. However, unlike the illustrated example, a part of the pass band PB of the BP filter 5 and a part of the transition band on the pass band PB side of the BE filter 7 (further, a part of the stop band EB) overlap. Therefore, the pass band CB may be narrower than the pass band PB. In the description of the embodiment, basically, an embodiment in which the pass band BP and the pass band CB match is taken as an example. Also, for convenience, the two may not be distinguished.

(Bandpass filter)
The configuration of the BP filter 5 may be various known configurations or a configuration to which a known configuration is applied. For example, the BP filter 5 uses a resonance circuit (in other words, an LC circuit) including an inductor (coil) and a capacitor (capacitor), and a dielectric resonator in which a dielectric is arranged between conductors (dielectric). It may be a body filter) and / or an elastic wave filter utilizing an elastic wave. The BP filter 5 using a resonance circuit (LC circuit) is, for example, LTCC (Low Temperature Co-fired Ceramics), which is manufactured by firing at a relatively low temperature and has an inductor and a conductor as a capacitor arranged on a laminated substrate made of ceramic. It may be a filter.

(Bandwidth blocking filter)
FIG. 2A is a block diagram schematically showing the configuration of the BE filter 7.

The BE filter 7 has an elastic wave filter 11 and a notch filter 13 which are sequentially located on the signal path 9. The order of the two filters on the signal path 9 is arbitrary. For example, either of the two filters may be on the input terminal 3A side, and any of the two filters may be on the BP filter 5 side.

The elastic wave filter 11 is a filter that attenuates a signal (unnecessary signal) having a frequency within at least a part of the blocking band EB (and / or the band around it). The elastic wave filter 11 has at least one elastic wave resonator 15. In FIG. 2, as the elastic wave resonator 15, the series resonator 15S constituting a part of the signal path 9 is exemplified.

Like the elastic wave filter 11, the notch filter 13 is also a filter that attenuates a signal (unnecessary signal) having a frequency within at least a part of the blocking band EB (and / or the band around it). The notch filter 13 connects, for example, the signal path 9 and the reference potential portion 17, and allows unnecessary signals to escape to the reference potential portion 17. A more specific configuration of the notch filter 13 is arbitrary. However, in the following, an embodiment in which the notch filter 13 does not utilize elastic waves (not an elastic wave filter) will be taken as an example. As shown in FIG. 2A, the reference potential portion 17 may be regarded as a portion different from the notch filter 13, and unlike the representation of FIG. 2A, the notch filter 13 may be regarded as a portion. It may be regarded as a part.

The notch filter is a kind of band-stop filter that attenuates a signal in a predetermined blocking band, and usually refers to a band-stop filter having a narrow blocking band (a high Q value from another viewpoint). In the present disclosure, the term notch filter is used in comparison with the band-stop filter 7. Therefore, for example, the notch filter 13 has a narrower blocking band and / or a higher Q value than the band blocking filter 7. On the other hand, the notch filter 13 does not need to have a narrow blocking band (or a high Q value) in terms of absolute value or in comparison with a general band blocking filter.

FIG. 2B is a diagram for explaining the filter characteristics of the elastic wave filter 11 and the notch filter 13.

In this figure, the horizontal axis f (Hz) indicates the frequency, and the frequency is higher toward the right side of the paper. The vertical axis A (dB) on the left side indicates the amount of attenuation, and the amount of attenuation is larger toward the lower side of the paper. The vertical axis | Z | (Ω) on the right side indicates the absolute value of the impedance, and | Z | is larger toward the upper side of the paper. The line LE shows the attenuation amount of the BE filter 7 as in the line LE of FIG. 1 (b). As can be understood from the shape of the line LE, FIG. 2B mainly shows the frequency range of the blocking band EB and its surroundings. The line LS indicates | Z | of the series resonator 15S. The line LN indicates | Z | between the signal path 9 and the reference potential portion 17 in the notch filter 13. In the following description, | Z | of the notch filter 13 refers to | Z | between the signal path 9 and the reference potential portion 17 unless otherwise specified.

The series resonator 15S (from another viewpoint, the elastic wave resonator 15) has a resonance frequency fsr in which | Z | is a minimum value and an antiresonance frequency fsa in which | Z | is a maximum value. The antiresonance frequency fsa is, for example, higher than the resonance frequency fsr (or vice versa). Since the series resonator 15S constitutes a part of the signal path 9, the component in the band centered on the antiresonance frequency fsa among the signals flowing through the signal path 9 is attenuated. On the other hand, the antiresonance frequency fsa is located in (or around) the blocking band EB. As a result, the signal in at least a part of the blocking band EB is attenuated.

The notch filter 13 has a resonance frequency fnr at which | Z | is a minimum value. Since | Z | here is | Z | between the signal path 9 and the reference potential portion 17 as described above, the notch filter 13 sets the resonance frequency fnr among the signals flowing through the signal path 9. The components in the central band are released to the reference potential portion 17. On the other hand, the resonance frequency fnr is located in (or around) the blocking band EB. As a result, the signal in at least a part of the blocking band EB is attenuated.

The anti-resonance frequency fsa of the series resonator 15S is located on the pass band PB side (high frequency side in this embodiment) with respect to the resonance frequency fnr of the notch filter 13. Further, in general, the elastic wave filter has a steeper slope of attenuation in the transition band than the filter having other configurations. From these facts, the inclination of the attenuation in the pass band PB side (high frequency side in this embodiment) of the BE filter 7 is, for example, the side opposite to the pass band PB side of the BE filter 7 (low frequency side in this embodiment). ), And the attenuation of the BP filter 5 is steeper than the inclination of the attenuation. On the other hand, the notch filter 13 secures, for example, the bandwidth of the blocking band EB.

As illustrated later, the elastic wave filter 11 may have a plurality of series resonators 15S. In this case, the plurality of antiresonance frequencies fsa may be partially or wholly the same (including the case where a tolerance exists), or may be different from each other. The frequency difference in the latter case may be appropriately set, and may be, for example, less than half or more than half the bandwidth of the blocking band EB. When a part or all of the plurality of antiresonance frequencies fsa are the same as each other, for example, the amount of attenuation in the blocking band of the elastic wave filter 11 can be increased. When a part or all of the plurality of antiresonance frequencies fsa are different from each other, for example, the blocking band of the elastic wave filter 11 can be widened by forming a plurality of attenuation poles.

When a plurality of antiresonant frequencies fsa different from each other exist, at least one of them is located on the passband PB side with respect to the resonance frequency fnr. As a result, the above-mentioned steepening action is exerted to some extent. Of course, all the anti-resonance frequency fsa may be located on the passing band PB side of the resonance frequency fnr, and 50% or more of the anti-resonance frequency fsa may be located on the passing band PB side of the resonance frequency fnr. May be.

The resonance frequency fsr and antiresonance frequency fsa of the series resonator 15S and the resonance frequency fnr of the notch filter 13 may be set in an appropriate positional relationship with respect to the pass band CB and PB and the blocking band EB. For example, the antiresonance frequency fsa located on the passband PB side of the resonance frequency fnr and / or the antiresonance frequency fsa not so are on the passband PB side (high in this embodiment) with respect to the center frequency of the blocking band EB. It may be located on the frequency side (frequency side) (example in the figure), may match, or may be located on the opposite side of the pass band PB (low frequency side in the present embodiment). The resonance frequency fsr may be located in the blocking band EB (illustrated example) or may be located outside the blocking band EB. The resonance frequency fnr may be located on the pass band PB side, coincide with the center frequency of the stop band EB, or may be located on the opposite side of the pass band PB. (Example in the figure).

The relative positional relationship between the resonance frequency fsr and the antiresonance frequency fsa of the series resonator 15S and the resonance frequency fnr of the notch filter 13 may be appropriately set. For example, the frequency difference between the anti-resonance frequency fsa (referred to as the first anti-resonance frequency) located on the pass band PB side of the resonance frequency fna and the resonance frequency fna is less than half the bandwidth of the blocking band EB. It may be more than half. Further, the frequency difference may be smaller or the same as the frequency difference between the resonance frequency fsr of the series resonator 15S having the first antiresonance frequency and the first antiresonance frequency (the frequency difference may be smaller or the same). Illustrated example), may be large. Further, the resonance frequency fnr may be located on the passband PB side with respect to the resonance frequency fsr of the series resonator 15S having the anti-resonance frequency fsa located on the passband PB side of the resonance frequency fnr. They may be in agreement (example in the figure), or may be located on the opposite side of the pass band PB.

(Circuit configuration of band cutoff filter)
FIG. 3 is a circuit diagram showing a more detailed configuration of the composite filter 1.

As described above, the composite filter 1 has a BP filter 5 and a BE filter 7 on the signal path 9 from the input terminal 3A to the output terminal 3B. The BE filter 7 has an elastic wave filter 11 and a notch filter 13.

In FIG. 3, for convenience of illustration, a plurality of reference potential portions 17 are shown. A part or all of the plurality of reference potential portions 17 may actually be different conductors from each other, or may actually be the same conductors from each other. Further, in the former case, a plurality of different conductors constituting the plurality of reference potential portions 17 may or may not be electrically connected to each other in the composite filter 1. May be good. Further, in FIG. 3, the reference potential portion 17 is shown in the block showing the elastic wave filter 11 and the notch filter 13. However, as described in the explanation of FIG. 2A, the reference potential portion 17 may be regarded as a part of each filter or may be regarded as a part separate from each filter.

(Circuit configuration of elastic wave filter)
The elastic wave filter 11 has a plurality of (four in the illustrated example) series resonators 15S connected in series with each other. The plurality of series resonators 15S form a part of the signal path 9. A part of this signal path 9 may be referred to as a series arm 19. Further, the elastic wave filter 11 has one or more (multiple in the illustrated example, more specifically three) parallel arms 21 connecting the series arm 19 (signal path 9) and the reference potential portion 17. is doing. The connection position of the parallel arm 21 with respect to the series arm 19 is, more specifically, the position between the series resonators 15S adjacent to each other with respect to the electrical connection.

Although not particularly shown, the parallel arm 21 connected to the input terminal 3A side of the series resonator 15S on the most input terminal 3A side (the earliest stage side) and / or the series resonator on the most output terminal 3B side (the rearmost stage side). A parallel arm 21 connected to the output terminal 3B side of the 15S may be provided. When the number of the series resonators 15S included in the elastic wave filter 11 is only one, the parallel arm 21 may be connected to the front stage and / or the rear stage of the series resonator 15S.

The method and effect of setting the anti-resonance frequency fsa and the like when a plurality of series resonators 15S are provided are as described above. The one or more parallel arms 21 may have various configurations, and their actions may also be various. For example, the parallel arm 21 may have an inductor and / or a capacitor, or may have an elastic wave resonator 15.

In this embodiment, all the parallel arms 21 have only an inductor 23 that connects the signal path 9 and the reference potential portion 17. In other words, the parallel arm 21 does not have the elastic wave resonator 15. Such an inductor 23, for example, reduces the probability that the entire plurality of series resonators 15S will function as a capacitor having a large capacitance, and thus reduces the probability that a signal having a frequency in the blocking band EB will pass through. Contribute to. Further, the inductor 23 may cooperate with the series resonator 15S to form a high-pass filter having a transition band between the blocking band EB and the pass band CB (and / or PB). The inductance of the inductor 23 may be set arbitrarily.

The elastic wave filter 11 may have an inductor 25 connected in parallel to the series resonator 15S. The number of inductors 25 may be one when a plurality of series resonators 15S are provided (example in the figure), or may be two or more and less than or equal to the number of series resonators 15S. Further, one inductor 25 may be connected in parallel to one series resonator 15S, or may be connected in parallel to two or more series resonators 15S. The inductor 25 contributes to increasing the amount of attenuation by forming an attenuation pole on the low frequency side or the high frequency side of the antiresonance frequency fsa, for example.

Although not particularly shown, the elastic wave filter 11 may have a capacitor connected in parallel to the series resonator 15S. When a plurality of series resonators 15S are provided, the number of such capacitors may be one, or may be two or more and less than or equal to the number of series resonators 15S. Further, one capacitor may be connected in parallel to one series resonator 15S, or may be connected in parallel to two or more series resonators 15S. The capacitor connected in parallel to the series resonator 15S contributes to, for example, shifting the antiresonance frequency fsa to the low frequency side.

(Circuit configuration of notch filter)
The notch filter 13 has, for example, one or more inductors and one or more capacitors. In the illustrated example, the notch filter 13 includes inductors 27A and 27B (hereinafter, A and B may be omitted) and capacitors 29A and 29B (hereinafter, A and B may be omitted). is doing. The inductor 27A and the capacitor 29A are connected in parallel between the signal path 9 and the reference potential portion 17. These elements (27A and 29A), the capacitor 29B, and the inductor 27B are connected in series between the signal path 9 and the reference potential portion 17. The order of these series connections may be different from the illustrated example.

In the notch filter 13, at least one of one or more inductors 27 and at least one of one or more capacitors 29 form a series resonant circuit. In the illustrated example, the inductors 27A and 27B and the capacitor 29B form a series resonant circuit. Further, the inductor 27B and the capacitors 29A and 29B also form a series resonant circuit. By constructing the series resonance circuit in this way, the notch filter 13 has a resonance frequency fnr in which the absolute value | Z | of the impedance becomes a minimum value.

The inductor 27A and the capacitor 29A form a parallel resonant circuit. The frequency (antiresonance frequency) at which | Z | of this parallel resonance circuit reaches a maximum value may be located in or around the passband CB (and / or PB), and is relatively far from the passband CB. May be. That is, the parallel resonant circuit may or may not affect the filter characteristics in the pass band CB of the composite filter 1 and the frequencies around it.

Since the illustrated notch filter 13 has four elements of the inductors 27A and 27B and the capacitors 29A and 29B, it can be said that the notch filter 13 has three or more elements. Further, the notch filter 13 shown in the figure includes an inductor 27A connected to the signal path 9 and the reference potential portion 17, and an inductor 27B connected in series to the inductor 27A between the signal path 9 and the reference potential portion 17. , And a capacitor 29A connected in parallel to the inductor 27A.

The inductance of the inductors 27A and 27B and the capacitance of the capacitors 29A and 29B may be appropriately set so that the resonance frequency fnr becomes a desired frequency. For example, a formula for synthesizing the inductance of a series-connected or parallel-connected inductor, a formula for synthesizing the capacitance of a series-connected or parallel-connected capacitor, and a formula for calculating the resonance frequency of a series resonant circuit from the inductance and the capacitance are known. be. Therefore, for example, by calculation based on such an equation, the values of the inductance and the capacitance at which the resonance frequency fnr becomes a desired frequency may be searched.

There are innumerable combinations of inductance and capacitance values that make the resonance frequency fnr a desired frequency. A method of selecting any combination from the innumerable combinations or from the finite number of combinations obtained by exploration may be appropriate. For example, the maximum inductance of one or more (two in the present embodiment) in each combination may be compared between the plurality of combinations, and the combination having the smallest maximum inductance may be selected.

(Structure of compound filter)
The circuit configuration of the composite filter 1 described above may be realized by various structures. Below are some examples.

(First example of structure)
FIG. 4A is a schematic cross-sectional view showing a first example of the structure of the composite filter 1. For convenience, the composite filter 1 having the structure shown in the figure is referred to as a composite filter 1A. In the composite filter 1, any direction may be upward, but for convenience, in the description of FIG. 4 (a) (and FIG. 4 (b) described later), the upper surface of the paper is upward, and the upper surface, the lower surface, and the like are used. Sometimes words are used.

The composite filter 1A is configured as, for example, a surface mount type chip component. The overall shape is, for example, roughly a thin rectangular parallelepiped shape (thickness is shorter than the length of the short side in a plan view) with the vertical direction as the thickness direction. The input terminal 3A and the output terminal 3B described above are provided on the lower surface of the composite filter 1A. The lower surface of the composite filter 1A is one main surface (the widest surface; the same applies hereinafter) of the composite filter 1A. Although not particularly shown, the composite filter 1A is mounted on the circuit board by joining the input terminal 3A and the output terminal 3B to the pad of the circuit board by conductive bumps.

The composite filter 1A has, for example, a circuit board 31, an elastic wave chip 33 mounted on the circuit board 31, and a sealing portion 35 that seals the elastic wave chip 33.

The BP filter 5 is composed of, for example, a circuit board 31. The BE filter 7 is, for example, partially configured by a circuit board 31 and the other partially composed of an elastic wave chip 33. More specifically, the elastic wave filter 11 is partially composed of the elastic wave chip 33 and the other part of the circuit board 31. At least a part of the notch filter 13 is composed of a circuit board 31. From another viewpoint, the elements constituting the composite filter 1A are dispersedly provided on the circuit board 31 and the elastic wave chip 33. Specifically, it is as follows.

The circuit board 31 is formed, for example, in a thin rectangular parallelepiped shape having a vertical direction as a thickness direction. The basic structure and material of the circuit board 31 (the structure excluding the specific conductor pattern and dimensions for forming the composite filter 1) are the same as the structures and materials of various known printed circuit boards. good. For example, the circuit board 31 may be an LTCC substrate. The circuit board 31 has an insulating substrate 37 and a conductor 39 located inside and / or on the surface of the insulating substrate 37.

The insulating substrate 37 has, for example, a plurality of insulating layers 37a laminated with each other. The conductor 39 has, for example, a conductor layer 39a located on the main surface of the insulating layer 37a and a via conductor 39b penetrating the insulating layer 37a. In other words, the conductor layer 39a is a layered conductor located inside or on the surface of the insulating substrate 37 and parallel to the main surface of the insulating substrate 37. In other words, the via conductor 39b is a conductor that penetrates a part or all of the thickness of the insulating substrate 37. The material of the insulating substrate 37 may be, for example, ceramic or resin, or may be a composite material composed of a plurality of types of materials. Examples of the composite material include a base material such as a glass cloth impregnated with a resin and a resin filled with a filler. The material of the conductor 39 may be an appropriate metal such as Cu or Ag.

The elastic wave chip 33 is configured as, for example, a surface mount type chip component. The overall shape is, for example, roughly a thin rectangular parallelepiped with the vertical direction as the thickness direction. The basic structure and material of the elastic wave chip 33 (configuration excluding the specific conductor pattern and dimensions for constituting the composite filter 1) are the same as the structures and materials of various known elastic wave chips. May be done. For example, the elastic wave chip 33 may be a bare chip, may be a WLP (Wafer level Package) type having a cover covering the surface of the bare chip on the circuit board 31 side, or may cover the side surface of the bare chip. It may be a FO (Fan Out) -WLP type having a molded portion. Here, an embodiment in which the elastic wave tip 33 is a bare tip is taken as an example. The elastic wave chip 33 has, for example, a chip substrate 41 and a conductor layer 43 located on a surface (one main surface) of the chip substrate 41 on the circuit board 31 side.

In the chip substrate 41, for example, at least a predetermined region of the surface on the circuit board 31 side is made of a piezoelectric material. The piezoelectric body is made of, for example, a single crystal having piezoelectricity. The single crystal is, for example, a crystal (SiO ₂ ), a lithium niobate (LiNbO ₃ ) single crystal, or a lithium tantalate (LiTaO ₃ ) single crystal. The cut angle may be appropriately set according to the type of elastic wave to be used and the like. For example, the chip substrate 41 may be entirely composed of a piezoelectric material (may be a piezoelectric substrate), or the chip substrate 41 may have a piezoelectric layer formed on a support substrate made of an appropriate material. Alternatively, the piezoelectric substrate and the support substrate may be bonded together. The material of the conductor layer 43 may be an appropriate metal such as Al.

Although not particularly shown, in addition to the above, the elastic wave chip 33 may have an insulating layer that covers the surface of the conductor layer 43 and the chip substrate 41 on the circuit board 31 side while exposing the terminals of the elastic wave chip 33. good. Such an insulating layer may be simply for reducing corrosion of the conductor layer 43, or may have an acoustically advantageous effect. The material of such an insulating layer may be appropriate, for example, SiO ₂ . Further, the side surface and the lower surface of the chip substrate 41 may be covered with an insulating layer or the like thinner than the thickness of the chip substrate 41.

The conductor layer 43 of the elastic wave chip 33 has, for example, the terminal 43a of the elastic wave chip 33. Further, the conductor layer 39a located on the upper surface of the circuit board 31 has a pad 39c facing the terminal 43a. The elastic wave chip 33 is mounted on the circuit board 31 by joining the terminal 43a and the pad 39c by the conductive bump 45. That is, the elastic wave chip 33 is fixed to the circuit board 31 by the bump 45 and is electrically connected. The material of the bump 45 is, for example, solder. Solder includes lead-free solder.

The sealing portion 35 covers, for example, the upper surface of the circuit board 31 from above the elastic wave chip 33. A gap is formed between the elastic wave chip 33 and the circuit board 31 with the thickness of the terminal 43a, the bump 45, and the pad 39c. The sealing portion 35 is not filled in this gap, and the gap is a closed space sealed by the sealing portion 35. The closed space may be in a vacuum state or may be filled with an appropriate inert gas (for example, nitrogen). The material of the sealing portion 35 may be an organic material, an inorganic material, or a combination of both. More specifically, for example, the sealing portion 35 may be made of a resin or a resin containing particles (fillers) made of an inorganic material.

The BP filter 5 is composed of, for example, a resonance circuit (LC circuit) including an inductor and a capacitor. The inductor of the BP filter 5 is composed of, for example, the conductor 39 of the circuit board 31. The electrode of the capacitor of the BP filter 5 is composed of, for example, the conductor 39 of the circuit board 31. The insulating substrate 37 may function as a dielectric between the electrodes of the capacitor.

The elastic wave resonator 15 of the elastic wave filter 11 is composed of a chip substrate 41 of an elastic wave chip 33 and a conductor layer 43. The inductors 23 and 25 of the elastic wave filter 11 are composed of, for example, the conductor 39 of the circuit board 31.

The inductor 27 (27A and / or 27B) of the notch filter 13 is composed of, for example, the conductor 39 of the circuit board 31. The electrode of the capacitor 29 (29A and / or 29B) of the notch filter 13 is composed of, for example, the conductor layer 43 of the elastic wave chip 33. The piezoelectric material of the chip substrate 41 may function as a dielectric material between the electrodes of the capacitor 29, for example.

The inductor composed of the conductor 39 of the circuit board 31 (for example, the inductor of the BP filter 5 and the inductors 23, 25 and 27) may have an appropriate configuration. For example, the inductor may be configured with a meander-like or spiral conductor pattern included in the conductor layer 39a.

The capacitor configured by the conductor 39 of the circuit board 31 (for example, the capacitor of the BP filter 5) may have an appropriate configuration. For example, the pair of electrodes of the capacitor may be composed of the same conductor layer 39a, or may be composed of different conductor layers 39a. Examples of the former include a pair of strip-shaped electrodes facing each other in a plan view and a pair of comb tooth electrodes that mesh with each other in a plan view (see the comb tooth electrodes of elastic wave resonators described later). As the latter, a flat plate electrode that faces each other with the insulating layer 37a interposed therebetween in the thickness direction of the insulating layer 37a can be mentioned.

The electrode of the capacitor 29 composed of the conductor layer 43 of the elastic wave chip 33 may have an appropriate configuration. For example, the capacitor 29 may be composed of a pair of strip-shaped electrodes facing each other in a plan view, or may be composed of a pair of comb tooth electrodes that mesh with each other in a plan view.

(Second example of structure)
FIG. 4B is a schematic cross-sectional view showing a second example of the structure of the composite filter 1. For convenience, the composite filter 1 having the structure shown in the figure is referred to as a composite filter 1B. In the following description, basically, only the differences from the composite filter 1A according to the first example will be described. Matters not specifically mentioned may be the same as in the first example. Further, for the configuration corresponding to the configuration of the composite filter 1A, the same reference numerals may be used even if there are differences.

The composite filter 1B has a circuit board 47 mounted on the circuit board 31. Then, at least a part of the elements composed of the circuit board 31 in the composite filter 1A is composed of the circuit board 47. In the illustrated example, the inductors 23 and 25 of the elastic wave filter 11 and the inductor 27 of the notch filter 13 are configured by the circuit board 47.

The circuit board 47 may be basically the same as the circuit board 31 except whether or not the elastic wave chip 33 is mounted. The description of the circuit board 31 may be incorporated into the circuit board 47 as long as there is no contradiction or the like. For example, the circuit board 47 has an insulating substrate 49 (corresponding to the insulating substrate 37) and a conductor 51 (corresponding to the conductor 39) located inside and / or on the surface of the insulating substrate 49, similarly to the circuit board 31. ing. The electrodes of the inductor and the capacitor are composed of, for example, a conductor layer included in the conductor 51. The circuit board 47 is mounted on the circuit board 31 by bumps 45, for example, like the elastic wave chip 33.

(Other examples of structure)
Although not particularly shown, various structures for realizing the composite filter 1 are possible in addition to the first example and the second example.

For example, the composite filter 1 may be a part of a module instead of a chip component. More specifically, for example, the circuit board 31 has a larger area than the illustrated example, electronic components that do not form the composite filter 1 are mounted, or an element that does not form the composite filter 1 is provided by a conductor 39. It may be configured. In such a case, the composite filter 1 may be connected to another electronic component or an element in the circuit board 31 by a wiring configured by the conductor 39 of the circuit board 31. From another point of view, it is not necessary that there is a portion that clearly matches the concept of the input terminal 3A and the output terminal 3B. Examples of electronic components mounted on the circuit board 31 and not constituting the composite filter 1 include ICs (Integrated Circuits) and chip-type antennas. As an element composed of the circuit board 31 and not constituting the composite filter 1, for example, an antenna can be mentioned.

Further, for example, the structure of the composite filter 1 may be such that the entire band blocking filter 7 is one chip component. More specifically, for example, in the example shown in FIG. 4B, the elastic wave chip 33 is mounted on a circuit board 47 (in other words, a circuit board not including the BP filter 5) and sealed, and the chip component is configured. May be done. Then, the band blocking filter 7 as a chip component may be mounted on a circuit board 31 including the BP filter 5 or a circuit board on which the BP filter 5 is mounted.

Further, for example, the arrangement of the inductor and the capacitor may be different from those described above. For example, in both the first example and the second example, the capacitor 29 of the notch filter 13 may be composed of the circuit board 31 and / or 47 instead of the elastic wave chip 33. Further, for example, in the second example, at least a part of the inductor and the capacitor of the BP filter 5 is composed of the circuit board 47, and / or at least a part of the inductor of the notch filter 13 is composed of the circuit board 47. You may. The element represented as one inductor or one capacitor in the circuit diagram may be composed of two or more conductors dispersed on different chips and / or circuit boards.

Further, for example, the elastic wave tip 33 may constitute an elastic wave filter other than the elastic wave filter 11. More specifically, for example, the illustrated chip components may constitute a duplexer (eg, a duplexer). The elastic wave filter 11 may constitute one of the transmission filter and the reception filter, and the other elastic wave filter may constitute the other of the transmission filter and the reception filter.

Further, for example, an elastic wave chip other than the elastic wave chip 33 may be mounted on the circuit board 31. More specifically, for example, chip components including elastic wave chips 33 and other elastic wave chips may constitute demultiplexers (eg, duplexers). The elastic wave filter 11 may form one of the transmission filter and the reception filter, and the other elastic wave chip may form the elastic wave filter as the other of the transmission filter and the reception filter. In this case, the capacitor 29 of the notch filter 13 may be provided on any elastic wave chip.

The mounting of electronic components such as the elastic wave chip 33 and the circuit board 47 on the circuit board 31 is not limited to the bump 45. For example, the electronic component may be fixed to the circuit board 31 with an insulating adhesive and may be electrically connected to the circuit board 31 by a bonding wire.

In the structure described above, the various inductors are provided not on the elastic wave chip 33 but on the circuit board (31 and / or 47) electrically connected to the elastic wave chip 33. As described above, the various inductors may be provided on the same circuit board, or may be distributed and provided on different circuit boards. In the following, for convenience, a structure that does not include the elastic wave chip 33 and includes a circuit board provided with an inductor may be referred to as a substrate structure 53. For example, in FIG. 4A, the substrate structure 53 is composed of one circuit board 31. In FIG. 4B, the substrate structure 53 comprises two circuit boards 31 and 47.

(Specific example of elastic wave resonator)
The elastic wave resonator 15 of the elastic wave filter 11 may have various configurations. For example, the surface acoustic wave resonator 15 may be a SAW resonator, or may be a BAW resonator that utilizes BAW while having an electrode similar to that of the SAW resonator, or may be a piezoelectric thin film on the cavity. It may be a piezoelectric thin film resonator (sometimes referred to as FBAR (Film Bulk Acoustic Resonator)) that vibrates. Hereinafter, the SAW resonator will be described as an example of the elastic wave resonator 15.

FIG. 5 is a plan view schematically showing the configuration of the SAW resonator as the surface acoustic wave resonator 15. This figure shows a part of the surface of the elastic wave chip 33 on the circuit board 31 side.

FIG. 5 is provided with a Cartesian coordinate system consisting of the D1 axis, the D2 axis and the D3 axis for convenience. The elastic wave resonator 15 may be upward or downward in either direction. However, in the following description, for convenience, terms such as the upper surface or the lower surface may be used with the positive side of the D3 axis facing upward. The D1 axis is defined so as to be parallel to the propagation direction of the elastic wave propagating along the surface (upper surface 41a) of the chip substrate 41 on the circuit board 31 side. The D2 axis is defined to be parallel to the upper surface 41a and orthogonal to the D1 axis. The D3 axis is defined to be orthogonal to the top surface 41a.

The elastic wave resonator 15 is composed of a so-called 1-port elastic wave resonator. The elastic wave resonator 15 outputs, for example, a signal input from one of the two wirings 55 shown on both sides of the paper from the other of the two wirings 55. At this time, the elastic wave resonator 15 converts an electric signal into an elastic wave and an elastic wave into an electric signal.

The elastic wave resonator 15 includes, for example, a chip substrate 41 (at least a part of the upper surface 41a side thereof), an excitation electrode 57 located on the upper surface 41a, and a pair of reflectors 59 located on both sides of the excitation electrode 57. Includes. A plurality of elastic wave resonators 15 may be configured on one chip substrate 41. That is, the chip substrate 41 may be shared by a plurality of elastic wave resonators 15. In the following description, in order to distinguish a plurality of elastic wave resonators 15 that share the same chip substrate 41, for convenience, a combination of the excitation electrode 57 and one reflector 59 (the electrode portion of the elastic wave resonator 15) is used. It may be expressed as if it is an elastic wave resonator 15 (as if the elastic wave resonator 15 does not include the chip substrate 41).

As described above, the chip substrate 41 has piezoelectricity at least in a predetermined region of the upper surface 41a. The excitation electrode 57 and the reflector 59 are composed of a layered conductor provided in the region. The excitation electrode 57 and the reflector 59 are made of, for example, the same material and thickness as each other. The layered conductor constituting these is, for example, a metal. The metal is, for example, Al or an alloy containing Al as a main component (Al alloy). The Al alloy is, for example, an Al—Cu alloy. The layered conductor may be composed of a plurality of metal layers. The thickness of the layered conductor is appropriately set according to the electrical characteristics required for the elastic wave resonator 15. As an example, the thickness of the layered conductor is 50 nm or more and 600 nm or less.

The excitation electrode 57 is composed of a so-called IDT (Interdigital Transducer) electrode, and has a pair of comb tooth electrodes 61 (one of which is hatched for convenience of visibility). Each comb tooth electrode 61 has, for example, a bus bar 63, a plurality of electrode fingers 65 extending in parallel with each other from the bus bar 63, and a plurality of dummy electrodes 67 protruding from the bus bar 63 between the plurality of electrode fingers 65. There is. The pair of comb tooth electrodes 61 are arranged so that the plurality of electrode fingers 65 mesh with each other (intersect).

The bus bar 63 is formed, for example, in an elongated shape having a substantially constant width and extending linearly in the propagation direction (D1 direction) of elastic waves. The pair of bus bars 63 face each other in a direction orthogonal to the propagation direction of the elastic wave (D2 direction). The width of the bus bar 63 may change or may be inclined with respect to the propagation direction of the elastic wave.

Each electrode finger 65 is formed, for example, in a substantially elongated shape extending linearly in a direction (D2 direction) orthogonal to the propagation direction of elastic waves with a substantially constant width. In each comb tooth electrode 61, a plurality of electrode fingers 65 are arranged in the propagation direction of elastic waves. Further, the plurality of electrode fingers 65 of one comb tooth electrode 61 and the plurality of electrode fingers 65 of the other comb tooth electrode 61 are basically arranged alternately.

The pitch p of the plurality of electrode fingers 65 (for example, the distance between the centers of the two electrode fingers 65 adjacent to each other) is basically constant in the excitation electrode 57. The excitation electrode 57 may have a part peculiar with respect to the pitch p. As peculiar parts, for example, a narrow pitch part in which the pitch p is narrower than most (for example, 80% or more), a wide pitch part in which the pitch p is wider than most (for example, 80% or more), and a small number of electrode fingers 65 are substantially interleaved. The thinned out part drawn is mentioned.

In the following, the pitch p refers to the pitch of the portion (most of the plurality of electrode fingers 65) excluding the above-mentioned peculiar portion unless otherwise specified. Further, even in most of the plurality of electrode fingers 65 excluding the peculiar portion, when the pitch is changed, the average value of the pitches of most of the plurality of electrode fingers 65 is used as the value of pitch p. You may use it.

The number of electrode fingers 65 may be appropriately set according to the electrical characteristics required for the elastic wave resonator 15. Since FIG. 5 is a schematic diagram, the number of electrode fingers 65 is shown to be small. In practice, more electrode fingers 65 may be arranged than shown. The same applies to the strip electrode 71 of the reflector 59 described later.

The lengths of the plurality of electrode fingers 65 are, for example, equivalent to each other. The excitation electrode 57 may be subjected to so-called apodization in which the lengths of the plurality of electrode fingers 65 (intersection width W described later from another viewpoint) change depending on the position in the propagation direction. The length and width of the electrode finger 65 may be appropriately set according to the required electrical characteristics and the like.

The dummy electrode 67 projects, for example, with a substantially constant width in a direction orthogonal to the propagation direction of the elastic wave. The width is equivalent to, for example, the width of the electrode finger 65. Further, the plurality of dummy electrodes 67 are arranged at the same pitch as the plurality of electrode fingers 65, and the tip of the dummy electrode 67 of one comb tooth electrode 61 is the tip of the electrode finger 65 of the other comb tooth electrode 61. And face each other through the gap. The excitation electrode 57 may not include the dummy electrode 67.

The pair of reflectors 59 are located on both sides of the plurality of excitation electrodes 57 in the propagation direction of elastic waves. Each reflector 59 may be electrically suspended, or may be given a reference potential. Each reflector 59 is formed in a grid pattern, for example. That is, the reflector 59 includes a pair of bus bars 69 facing each other and a plurality of strip electrodes 71 extending between the pair of bus bars 69. The pitch of the plurality of strip electrodes 71 and the pitch of the electrode fingers 65 adjacent to each other and the strip electrodes 71 are basically the same as the pitch of the plurality of electrode fingers 65.

When a voltage is applied to the pair of comb tooth electrodes 61, the voltage is applied to the upper surface 41a (piezoelectric body) having piezoelectricity by the plurality of electrode fingers 65, and the piezoelectric body vibrates. As a result, elastic waves propagating in the D1 direction are excited. Elastic waves are reflected by a plurality of electrode fingers 65. Then, a standing wave having a pitch p of the plurality of electrode fingers 65 having a pitch p of approximately half a wavelength (λ / 2) is generated. The electrical signal generated in the piezoelectric body by the standing wave is taken out by a plurality of electrode fingers 65.

According to the above principle, the elastic wave resonator 15 functions as a resonator having a resonance frequency (for example, resonance frequency fsr) of an elastic wave having a pitch p as a half wavelength. In the elastic wave resonator 15, the antiresonance frequency (for example, the antiresonance frequency fsa) is basically defined by the resonance frequency defined by the pitch p and the capacitance ratio in the elastic wave resonator 15. The capacitance ratio is the ratio between the capacitance of the elastic wave resonator 15 (excitation electrode 57) and the capacitance (dynamic capacitance) of the series resonant circuit when the elastic wave resonator 15 is represented by an equivalent circuit.

A typical configuration example of one elastic wave resonator 15 has one excitation electrode 57 as described above. However, one elastic wave resonator 15 may have a plurality of excitation electrodes 57 connected in series with each other. In other words, one elastic wave resonator 15 may be divided into a plurality of parts. In this case, for example, since the voltage applied to the elastic wave resonator 15 is dispersed in the plurality of excitation electrodes 57, the electric resistance of the elastic wave resonator 15 is improved.

(Capacitor configuration)
As described above, the pair of electrodes of the capacitor 29 of the notch filter 13 may be composed of a pair of comb tooth electrodes located in the region having piezoelectricity in the upper surface 41a of the chip substrate 41. The above description of the pair of comb-tooth electrodes 61 of the excitation electrode 57 may be appropriately applied to the pair of comb-tooth electrodes constituting the capacitor 29.

However, unlike the excitation electrode 57, the pair of comb tooth electrodes constituting the capacitor 29 does not need to generate elastic waves, and may be configured not to generate elastic waves. Therefore, for example, the orientation of the comb-teeth electrode of the capacitor 29 with respect to the crystal orientation of the piezoelectric body (from another viewpoint, the propagation direction of elastic waves) is arbitrary. For example, unlike the excitation electrode 57, the capacitor 29 may be provided with the electrode fingers in a direction parallel to or inclined with respect to the propagation direction of the elastic wave. Further, for example, the pitches of the plurality of electrode fingers in the capacitor 29 are also arbitrary. For example, the pitch of the electrode fingers in the capacitor 29 may be smaller than the pitch p of the electrode fingers 65 in the excitation electrode 57. In this case, the capacitance of the capacitor 29 can be increased (from another point of view, the capacitor 29 can be miniaturized).

As described above, in the present embodiment, the BE filter 7 has a pass band XB and a blocking band EB located on the low frequency side or the high frequency side (low frequency side in the present embodiment) with respect to the pass band XB. It is a band blocking filter that attenuates a component having a frequency in the blocking band EB among the signals flowing through the signal path 9. The BE filter 7 has an elastic wave chip 33 and a substrate structure 53. The elastic wave chip 33 has one or more elastic wave resonators 15. Each of the one or more elastic wave resonators 15 has a resonance frequency (for example, resonance frequency fsr) and an antiresonance frequency (for example, antiresonance frequency fsa). The substrate structure 53 has one or more circuit boards (31 and / or 47). The conductors (39 and / or 51) of the one or more circuit boards constitute one or more first inductors (inductors 23 and / or 25) and one or more second inductors (inductors 27). The elastic wave chip 33 and the substrate structure 53 constitute an elastic wave filter 11 and a notch filter 13. The elastic wave filter 11 attenuates a component having a frequency in at least a part of the blocking band EB among the signals flowing through the signal path 9. The notch filter 13 connects the signal path 9 and the reference potential portion 17, and has a resonance frequency fnr at which the impedance between the signal path 9 and the reference potential portion 17 becomes the minimum value. The elastic wave filter 11 includes one or more series resonators 15S including a part of the signal path 9, and one or more first inductors (inductor 23 and / /). Or 25) and. The notch filter 13 has one or more inductors 27. At least one antiresonance frequency fsa of one or more series resonators 15S is located between the resonance frequency fnr of the notch filter 13 and the pass band XB.

Therefore, for example, as described above, the slope of attenuation in the transition band on the pass band XB side (high frequency side in this embodiment) of the BE filter 7 is generally due to the elastic wave filter 11 having a steep slope of attenuation in the transition band. Can be steep. On the other hand, the notch filter 13 can, for example, secure the bandwidth of the blocking band EB and increase the amount of attenuation in the blocking band EB. By securing the bandwidth with the notch filter 13, for example, the number of series resonators 15S can be reduced, and the insertion loss in the pass band XB can be reduced. Further, since the inductor 23 and / or 25 of the elastic wave filter 11 and the inductor 27 of the notch filter 13 are composed of the circuit board 31 and / or 47, for example, it is advantageous for miniaturization of the elastic wave chip 33. .. Further, since the dielectric constant of the insulating material of the circuit board 31 and / or 47 is usually lower than the dielectric constant of the piezoelectric material of the elastic wave chip 33, the capacitive component generated in the inductor is reduced. As a result, the influence of the self-resonance of the inductor on the filter characteristics is reduced.

Further, in the present embodiment, the notch filter 13 may have one or more capacitors 29 in addition to one or more inductors 27. The number of at least one of one or more inductors 27 and one or more capacitors 29 may be two or more.

In this case, the degree of freedom in design is improved as compared with, for example, an embodiment in which the notch filter 13 is configured by one inductor 27 and one capacitor 29 (the embodiment may also be included in the technique according to the present disclosure). .. As a result, for example, it becomes easy to increase the resonance frequency fnr of the notch filter 13. As a result, it becomes easy to realize a blocking band EB having a relatively high frequency (for example, a blocking band EB having a lower limit frequency of 2 GHz or more). Further, by improving the degree of freedom in design, for example, the largest inductance among the inductances of one or more inductors 27 can be reduced. As a result, the self-resonant frequency of the inductor 27 can be increased, and the probability that the self-resonant frequency affects the filter characteristics can be reduced.

Further, in the present embodiment, the notch filter 13 may have an inductor 27A, a first capacitor (capacitor 29B), and a second capacitor (capacitor 29C). The inductor 27A may connect the signal path 9 and the reference potential portion 17. The capacitor 29B may be connected in series with the inductor 27A between the signal path 9 and the reference potential portion 17. The capacitor 29A may be connected in parallel to the inductor 27A.

In this case, for example, since the notch filter 13 is composed of three or more elements, the degree of freedom in design is improved as described above. Further, since the series resonance circuit and the parallel resonance circuit are mixed, the series resonance circuit reduces the absolute value | Z | of the impedance at the resonance frequency fnr, and the parallel resonance circuit reduces the band other than the blocking band EB. In, | Z | can be made smaller. As a result, it is possible to reduce the insertion loss in the pass band XB while increasing the amount of attenuation in the blocking band EB with respect to the signal path 9.

Further, in the present embodiment, the notch filter 13 may have one or more capacitors 29 in addition to one or more inductors 27. At least one (eg, all) of one or more capacitors 29 may be composed of a pair of comb-tooth electrodes located on the elastic wave chip 33 (see comb-tooth electrodes 61 of the elastic wave resonator 15).

As described above, the dielectric constant of the piezoelectric material of the elastic wave chip 33 is usually higher than the dielectric constant of the insulating material of the circuit board 31 and / or 47. Further, since the pair of electrodes of the capacitor 29 is a pair of comb tooth electrodes, it is easy to lengthen the lengths of the edges of the pair of electrodes facing each other. As a result, it is easy to secure the capacity of the capacitor 29. From another point of view, it is easy to miniaturize the capacitor 29.

Further, in the present embodiment, the elastic wave filter 11 may have a series arm 19 and one or more parallel arms 21. The series arm 19 may have a plurality of series resonators 15S connected in series with each other in the signal path 9. One or more parallel arms 21 may connect one or more intermediate positions between the plurality of series resonators 15S of the series arms 19 to the reference potential portion 17. At least one of the one or more parallel arms 21 (all in the present embodiment) includes the inductor 23 connecting the above intermediate position and the reference potential portion 17 among the one or more first inductors, and 1 The configuration may be such that none of the above elastic wave resonators 15 is included.

In this case, for example, an embodiment in which all of one or more parallel arms 21 have elastic wave resonators 15 (so-called parallel resonators described later) (the embodiment may also be included in the technique according to the present disclosure). In comparison, the insertion loss in the passband XB can be reduced. The reason is that, for example, the elastic wave resonator 15 functions as a capacitor in a band other than between the resonance frequency and the antiresonance frequency, so that the parallel resonator escapes the high frequency signal to the reference potential portion 17. Can be mentioned.

Further, in the present embodiment, as in the first example shown in FIG. 4A, the elastic wave chip 33 includes one or more first inductors (23 and / or 25) and one or more first inductors (23 and / or 25) among one or more circuit boards. It may be mounted on a circuit board 31 having at least one of one or more second inductors (27).

In this case, for example, the electrical path between the series resonator 15S and the inductor (23, 25 and / or 27) is shortened. As a result, for example, the probability of increased insertion loss or spurious due to parasitic capacitance is reduced.

Further, the composite filter 1 according to the present embodiment has the BE filter 7 and the BP filter 5 as described above. The BP filter 5 has a second pass band (pass band PB) adjacent to the pass band XB side (high frequency side in this embodiment) of the BE filter 7 with respect to the blocking band EB, and provides a signal path 9. Among the flowing signals, the component having a frequency outside the pass band PB is attenuated.

As described with reference to FIGS. 1 (b) and 1 (c), the combination of the BP filter 5 and the BE filter 7 has a relatively wide pass band CB and a transition band on the stop band EB side. The composite filter 1 as a bandpass filter having a steep slope of attenuation is obtained.

In the present embodiment, the BP filter 5 may be composed of a substrate structure 53 having an inductor (23, 25 and / or 27) of the BE filter 7.

In this case, for example, the electrical path between the BP filter 5 and the BE filter 7 is shortened. As a result, for example, the probability of increased insertion loss or spurious due to parasitic capacitance is reduced.

<Second Embodiment>
FIG. 6 is a circuit diagram showing the configuration of the composite filter 201 according to the second embodiment, and corresponds to FIG. 3 of the first embodiment.

The composite filter 201 is different from the composite filter 1 of the first embodiment in the structure of the elastic wave filter. Specifically, the elastic wave filter 211 of the BE filter 207 according to the present embodiment has one less number of series resonators 15S than the elastic wave filter 11 of the first embodiment. Further, among the plurality of parallel arms 21, the parallel arm 21A has a parallel resonator 15P. The specific characteristics (inductance, capacitance, resonance frequency, antiresonance frequency, etc.) of the elements having the same reference numerals as those of the first embodiment are different from those of the first embodiment due to the above differences. good.

Similar to the series resonator 15S, the parallel resonator 15P is composed of the elastic wave resonator 15 and has a resonance frequency and an antiresonance frequency (line LS of the series resonator 15S in FIG. 2B). See.). The parallel resonator 15P (in another aspect, the parallel arm 21A) may be set so that its resonance frequency substantially coincides with the antiresonance frequency fsa of the series resonator 15S, for example. In this case, the parallel resonator 15P and the series resonator 15S provide a band blocking filter having a band slightly narrower than the frequency band from the resonance frequency fsr of the series resonator 15S to the anti-resonance frequency of the parallel resonator 15P. It is composed. Then, the band blocking filter is incorporated in the BE filter 207. When the anti-resonance frequency fsa of the series resonator 15S and the resonance frequency of the parallel resonator 15P match, for example, the difference between the two is the frequency between the resonance frequency fsr and the anti-resonance frequency fsa in the series resonator 15S. It may be 10% or less of the difference.

The parallel arm 21A has an inductor 23 connected in series with the parallel resonator 15P in addition to the parallel resonator 15P. The inductor 23 contributes to, for example, shifting the resonance frequency of the parallel resonator 15P (in another viewpoint, the parallel arm 21A) to the low frequency side. The inductor 23 may not be provided in the parallel arm 21A.

The BE filter 207 according to the second embodiment described above includes the elastic wave filter 211 and the notch filter 13 composed of a plurality of elements dispersed in the elastic wave chip 33 and the substrate structure 53, as in the first embodiment. Have. Therefore, the same effect as that of the first embodiment is obtained. For example, with a configuration in which the number of series resonators 15S is reduced, it is possible to realize a filter characteristic in which the bandwidth of the blocking band EB is wide and the slope of attenuation in the transition band on the pass band XB side is steep.

<Third Embodiment>
FIG. 7 is a circuit diagram showing the configuration of the composite filter 301 according to the third embodiment, and corresponds to FIG. 3 of the first embodiment.

The composite filter 301 differs from the composite filter 1 of the first embodiment in the configuration of the notch filter. Specifically, the notch filter 313 of the BE filter 307 according to the present embodiment has a configuration in which the inductor 27B is eliminated from the notch filter 13 of the first embodiment. The specific characteristics (inductance, capacitance, resonance frequency, antiresonance frequency, etc.) of the elements having the same reference numerals as those of the first embodiment are different from those of the first embodiment due to the above differences. good.

Although the notch filter 313 does not have the inductor 27B, it can be said that the notch filter 313 is composed of three elements (27A, 29A and 29B) like the notch filter 13 of the first embodiment. In other words, the notch filter 313 has one or more second inductors (inductors 27) and one or more capacitors 29, and at least one of one or more second inductors and one or more capacitors 29 (in other words). In this embodiment, the number of capacitors) is 2 or more. Further, as in the first embodiment, the notch filter 313 is located between the second inductor (inductor 27A) connecting the signal path 9 and the reference potential portion 17 and the signal path 9 and the reference potential portion 17. It can be said that it has a first capacitor (capacitor 29B) connected in series to the inductor 27A and a second capacitor (capacitor 29A) connected in parallel to the inductor 27A.

Similar to the first embodiment, the BE filter 307 according to the third embodiment includes an elastic wave filter 11 and a notch filter 313 composed of a plurality of elements dispersed in the elastic wave chip 33 and the substrate structure 53. Have. Therefore, the same effect as that of the first embodiment is obtained. For example, with a configuration in which the number of series resonators 15S is reduced, it is possible to realize a filter characteristic in which the bandwidth of the blocking band EB is wide and the slope of attenuation in the transition band on the pass band XB side is steep.

<Examples according to the first to third embodiments>
Specific characteristic values (inductance, capacitance, etc.) were set for the various elements of the first to third embodiments, and the filter characteristics were obtained by simulation calculation. Then, it was confirmed that the slope of attenuation can be steep. Specifically, it is as follows.

(Comparative example)
Before showing the calculation result, the configuration of the comparative example will be described.

FIG. 8 is a circuit diagram showing the configuration of the composite filter 1001 according to the comparative example, and corresponds to FIG.

The composite filter 1001 according to the comparative example has a BE filter configuration different from that of the embodiment. Specifically, the BE filter 1007 according to the comparative example does not have a notch filter and is composed only of the elastic wave filter 1011. Further, the elastic wave filter 1011 has a larger number of parallel resonators 15P (number of parallel arms 21A including the parallel resonator 15P) than the elastic filter of the embodiment.

(Example of compound filter)
9 (a), 9 (b), 9 (a), 9 (b) and 11 are diagrams showing the filter characteristics obtained as a result of the calculation.

In these figures, the horizontal axis f (GHz) indicates the frequency. The vertical axis A (dB) indicates the amount of attenuation. Similar to FIG. 2B, these figures show the blocking band EB of the BE filter and its surroundings. Therefore, the left end of the horizontal axis f roughly corresponds to the left end of the blocking band EB or a frequency around it. Further, the right end of the horizontal axis roughly corresponds to the left end of the pass band CB and the PB (in another viewpoint, the right end of the blocking band EB) or its surroundings.

FIG. 9A shows the characteristics of the BP filter 5. FIG. 9B shows the characteristics of the composite filter 1001 according to the comparative example. FIG. 10A shows the characteristics of the composite filter 1 according to the first embodiment. FIG. 10B shows the characteristics of the composite filter 201 according to the second embodiment. FIG. 11 shows the characteristics of the composite filter 301 according to the third embodiment. In the composite filter according to the comparative example and the first to third embodiments, the characteristics (inductance, capacitance, etc.) of various elements are adjusted so that the filter characteristics are optimized.

FIG. 9A relating to the BP filter 5 is compared with another diagram relating to the composite filter. From the comparison, it was confirmed that by combining the BE filter including the elastic wave filter with the BP filter 5, the slope of attenuation in the transition band on the low frequency side (the blocking band side of the BE filter) of the BP filter 5 could be steep. can. Specifically, in FIG. 9A, even at the left end (4.2 GHz) of the horizontal axis, the attenuation amount does not reach -30 dB (in other words, a magnitude that can be regarded as the attenuation amount of the blocking band). On the other hand, in the composite filter, the attenuation reaches -30 dB at about 5.0 GHz.

In FIGS. 9 (b) to 11 related to the composite filter, the frequency range of approximately 5.0 GHz or more and 5.1 GHz or less is the transition band on the low frequency side (blocking band EB side) of the composite filter. Comparing Comparative Example (FIG. 9 (b)) and Example (FIGS. 10 (a) to 11) in this frequency range, the steepness of the attenuation gradient in the example is the attenuation gradient in the comparative example. It is equal to or better than steepness. Therefore, it can be said that in the example, although the number of elastic wave resonators 15 is reduced as compared with the comparative example, the steepness of the slope of the attenuation is maintained.

In the comparative example (FIG. 9 (b)), the attenuation in the frequency range of 4.2 GHz or more and 4.35 GHz or less is relatively small, and there are some frequencies in which the attenuation does not reach -30 dB. On the other hand, in the embodiment (FIGS. 10A to 11), the attenuation is less than -30 dB even in the above frequency range (the attenuation is large). From this, it can be confirmed that the bandwidth of the blocking band EB is secured by the notch filter 13.

The frequency range of approximately 5.1 GHz or higher is the range considered to be the pass band CB of the composite filter. In this range, the attenuation amount of the examples (FIGS. 10A to 11) is smaller than the attenuation amount of the comparative example (FIG. 9B). The difference is about 1 dB. From this, it can be confirmed that the insertion loss in the pass band CB (or XB) is small in the embodiment because the number of parallel resonators 15P is reduced as compared with the comparative example.

(Example of notch filter)
The characteristics of the notch filter were calculated by specifically setting the inductance of the inductor of the notch filter and the capacitance of the capacitor (hereinafter, these may be referred to as "element values"). Then, it was confirmed that the maximum inductance in the notch filter can be reduced by configuring the notch filter with three or more elements. Specifically, it is as follows.

The following three configurations are assumed as the configurations of the notch filter.
First configuration example: A configuration having only one inductor 27 and one capacitor 29 connected in series with each other.
Second configuration example: Configuration of the notch filter 13 according to the first embodiment (FIG. 3)
Third configuration example: Configuration of the notch filter 313 according to the third embodiment (FIG. 7)

Then, the element values of the first to third configuration examples were calculated by calculation so that the same resonance frequency fnr could be obtained from each other. At this time, for the second and third configuration examples, the element values were obtained so that the maximum inductance was minimized and the change in the absolute value of the impedance with respect to the frequency was close to that of the first configuration example. .. As a reminder, the notch filter according to the first configuration example may be used for the BE filter according to the embodiment as well as the notch filter according to the second and third configuration examples (the first configuration example is a comparison). Not an example.).

The element values in each configuration example are as follows.
First configuration example:
Inductor: 5.0nH
Capacitor: 0.254pF
Second configuration example:
Inductor 27A: 2.5nH
Capacitor 29A: 0.111pF
Inductor 27B: 0.976nH
Capacitor 29B: 0.304pF
Third configuration example:
Inductor 27A: 3.46nH
Capacitor 29A: 0.0456pF
Capacitor 29B: 0.325pF

FIG. 12A is a diagram showing the characteristics of the first to third configuration examples when the above element values are set.

In this figure, the horizontal axis f (MHz) indicates a frequency. The vertical axis | Z | indicates the absolute value of impedance. The line L1 corresponds to the first configuration example, the line L2 corresponds to the second configuration example, and the line L3 corresponds to the third configuration example.

As shown in these figures, the second and third configuration examples are configurations in which a parallel resonance circuit and a series resonance circuit are combined, but have the same characteristics as the first configuration example of only the series resonance circuit. Has been obtained. Further, as described above, the maximum inductance in the second and third configuration examples (second configuration example: 2.5 nH, third configuration example: 3.46 nH) is the maximum inductance in the first configuration example (5. It is smaller than 0nH). Therefore, it is easy to increase the self-resonant frequency.

In the above, the element values in the second and third configurations are obtained so that the change in the absolute value of the impedance with respect to the frequency in the second and third configurations approaches that of the first configuration. However, the element values of the second and third configuration examples may be set so as to obtain characteristics different from those of the first configuration example. In this case, for example, the maximum inductance can be further reduced.

For example, the following element values can be exemplified for the third configuration example.
Third configuration example:
Inductor 27A: 2.0nH
Capacitor 29A: 0.23pF
Capacitor 29B: 0.404pF

FIG. 12B is a diagram showing the characteristics of the first to third configuration examples when the above element values are set in the third configuration example, and corresponds to FIG. 12A. Lines L1 and L2 are the same as those in FIG. 12 (a). The line L3A shows the characteristics of the third configuration example and corresponds to the line L3 in FIG. 12 (a).

As shown in this figure, the line L3A showing the third configuration example shows the same characteristics as the first and second configuration examples in the vicinity of the resonance frequency (near about 4500 MHz). However, in the third configuration example, the antiresonance characteristic appears between 7000 MHz and 8000 MHz. However, the frequency range in which the antiresonance characteristic appears is relatively far from the blocking band EB (5000 MHz or less). Therefore, it is unlikely that the anti-resonance characteristic reduces the attenuation characteristic in the blocking band EB of the BE filter, and conversely, the anti-resonance characteristic contributes to reducing the insertion loss of the BE filter.

<Fourth Embodiment>
The composite filter according to the fourth embodiment differs from the other embodiments only in the setting of the values such as the resonance frequency and the anti-resonance frequency in the BE filter. The basic configuration of the composite filter of the fourth embodiment may be the same as the configuration of any of the composite filters of the first to third embodiments. Here, for convenience, the reference numerals of the first embodiment are used.

13 (a) and 13 (b) are diagrams showing the characteristics of the composite filter 1 according to the fourth embodiment.

FIG. 13 (a) corresponds to FIG. 1 (b). FIG. 13 (b) corresponds to FIG. 2 (b). The line LE1 shows the filter characteristics of the BE filter 7 as in the line LE of FIG. 1 (b). The other lines are the same as those in FIGS. 1 (b) and 2 (b).

In the first to third embodiments, the blocking band EB of the BE filter 7 is located on the low frequency side with respect to the pass band BP of the BP filter 5 (in another viewpoint, the pass band CB of the composite filter 1). On the other hand, in the present embodiment, the blocking band EB is located on the high frequency side with respect to the pass band BP. Then, on the high frequency side of the pass band BP, the steepness of the attenuation characteristic due to the use of the elastic wave resonator 15 is obtained.

Also in this case, as in the first embodiment, the antiresonance frequency fsa of the series resonator 15S is between the resonance frequency fnr of the notch filter 13 and the pass band XB (or pass band PB or CB) of the BE filter 7. Is located in. The description of the anti-resonance frequency fsa and the resonance frequency fnr described in the first embodiment may be applied to the present embodiment as long as there is no contradiction or the like.

In the present embodiment, unlike the first embodiment, the pass band XB of the BE filter 7 is located on the lower frequency side of the blocking band EB among the two pass bands located on both sides of the blocking band EB. It is a pass band. Further, in the series resonator 15S of the illustrated example, the antiresonance frequency fsa is located on the higher frequency side than the resonance frequency fsr. Therefore, the resonance frequency fnr of the notch filter 13 is located on the opposite side (high frequency side) of the resonance frequency fsr with respect to the antiresonance frequency fsa.

<Other embodiments>
Although not particularly shown, the first to third embodiments (hereinafter, for convenience, only the first embodiment and its reference numerals are used) and the fourth embodiment may be appropriately combined.

For example, the composite filter includes a BP filter 5, a BE filter 7 (first embodiment) having a blocking band EB on the low frequency side with respect to the pass band PB, and a blocking band EB on the high frequency side with respect to the pass band PB. You may have a BE filter 7 (fourth embodiment) having the above. In another aspect, the composite filter may have steep attenuation slopes on both sides of the passband CB.

Further, for example, the BE filter has a series resonator 15S of the first embodiment having an anti-resonance frequency fsa on the high frequency side with respect to the resonance frequency fnr of the notch filter 13 (an elastic wave filter 11 from another viewpoint). And the series resonator 15S of the fourth embodiment (elastic wave filter 11 from another viewpoint) having an anti-resonance frequency fsa on the low frequency side with respect to the resonance frequency fnr may be provided. That is, in the BE filter, the slope of the attenuation may be steep on both sides of the blocking band EB.

<Application example>
FIG. 14 is a block diagram showing a main part of the communication device 151 as an example of using the composite filter.

The communication device 151 performs wireless communication using radio waves. The communication device 151 may have any of the composite filters (or BE filters only) of the plurality of embodiments described above. However, in the following description, for convenience, the reference numerals of the first embodiment will be used.

In the communication device 151, the transmission information signal TIS including the information to be transmitted is modulated and the frequency is raised (converted to a high frequency signal having a carrier frequency) by RF-IC (Radio Frequency Integrated Circuit) 153, and the transmission signal TS is performed. It is said that. The transmission signal TS is amplified by the amplifier 157 and input to the transmission filter 109 of the demultiplexer 101 after the unnecessary components other than the passing band for transmission are removed by the bandpass filter 155. Then, the transmission filter 109 removes unnecessary components other than the passing band for transmission from the input transmission signal TS, and outputs the removed transmission signal TS to the antenna 159. The antenna 159 converts the input electric signal (transmission signal TS) into a radio signal (radio wave) and transmits the radio signal (radio wave).

Further, in the communication device 151, the radio signal (radio wave) received by the antenna 159 is converted into an electric signal (received signal RS) by the antenna 159 and input to the reception filter 111 of the duplexer 101. The reception filter 111 removes unnecessary components other than the passing band for reception from the input reception signal RS and outputs the input to the amplifier 161. The output received signal RS is amplified by the amplifier 161 and unnecessary components other than the passing band for reception are removed by the bandpass filter 163. Then, the frequency of the received signal RS is reduced and demodulated by the RF-IC153 to obtain the received information signal RIS.

The transmission information signal TIS and the reception information signal RIS may be low frequency signals (baseband signals) including appropriate information, and are, for example, analog audio signals or digitized signals. The passing band of the radio signal may be appropriately set, and may be a relatively high frequency passing band (for example, 5 GHz or more). The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of any two or more of these. Although the direct conversion system is exemplified in FIG. 14, the circuit system may be any other appropriate circuit system, and may be, for example, a double superheterodyne system. Further, FIG. 14 schematically shows only the main part, and a low-pass filter, an isolator, or the like may be added at an appropriate position, or the position of the amplifier or the like may be changed.

In such a communication device 151, for example, the transmission filter 109 may be configured by the composite filter 1 according to the embodiment. In this case, the signal from the amplifier 157 is input to the input terminal 3A. The signal output from the output terminal 3B is input to the antenna 159. And / or, the reception filter 111 may be configured by the composite filter 1 according to the embodiment. In this case, the signal from the antenna 159 is input to the input terminal 3A. The signal output from the output terminal 3B is input to the amplifier 161.

As described above, various electronic components may be mounted on the substrate structure 53, or various elements may be built into the substrate structure 53. Thus, for example, the RF-IC153, bandpass filters 155 and 163, amplifiers 157 and 161 described above, and at least one of the antennas 159 are electronic components mounted on the substrate structure 53 (eg, circuit board 31). good. Further, for example, at least one of the bandpass filters 155 and 163 and the antenna 159 may be composed of a conductor of the substrate structure 53 (for example, the circuit board 31 and / or 47).

In the above embodiments, the inductors 23 and 25 are examples of the first inductor, respectively. The inductor 27 is an example of the second inductor, respectively. RF-IC153 is an example of an integrated circuit element. The capacitor 29B is an example of the first capacitor. The capacitor 29A is an example of the second capacitor.

The technique according to the present disclosure is not limited to the above embodiments, and may be implemented in various embodiments. For example:

A BE filter that combines an elastic wave filter and a notch filter can reduce the number of elastic wave resonators (particularly parallel resonators) while achieving desired filter characteristics. However, such reduction of elastic wave resonators may not be performed. For example, each of all parallel arms may have a parallel resonator.

The elastic wave filter may have only one of the inductors 23 and 25 as the first inductor (the inductor composed of the conductor of the substrate structure and constituting the elastic wave filter).

Further, by configuring the notch filter 13 with three or more elements as shown in FIGS. 3, 6 and 7, it is possible to realize desired attenuation characteristics with an inductance and a capacitance that do not require an increase in size in the inductors and capacitors constituting the elements. Can be done. In a notch filter using such three elements and four elements, the connection relationship of each element is not limited to the examples shown in FIGS. 3, 6 and 7. The notch filter 13'in the circuit diagram shown in FIG. 15A, which is the equivalent circuit of the notch file 13 shown in FIGS. 3 and 6, may be used, or FIG. 15 (the equivalent circuit of the notch filter 313 shown in FIG. 7). The notch filter 313'in the circuit diagram shown in b) may be used.

1 ... Composite filter, 3A ... Input terminal, 3B ... Output terminal, 5 ... Bandpass filter (BP filter), 7 ... Band blocking filter (BE filter), 9 ... Signal path, 11 ... Elastic wave filter, 13 ... Notch filter , 15 ... elastic wave resonator, 15S ... series resonator, 17 ... reference potential part, 23 ... inductor (first inductor), 25 ... inductor (first inductor), 27 (27A, 27B) ... inductor (second inductor) ), 31 ... Circuit board, 33 ... Elastic wave chip, 47 ... Circuit board, 53 ... Board structure, XB ... Passing band (of band-stop filter), EB ... Blocking band (of band-stop filter), fnr ... (Notch) Resonance frequency (of the filter), fsa ... Anti-resonance frequency (of the series inductor).

Claims (9)

It has a pass band and a blocking band located on the low frequency side or the high frequency side of the pass band, and among the signals flowing in the signal path, a band that attenuates a component having a frequency within the blocking band. It ’s a blocking filter,
An elastic wave chip having one or more elastic wave resonators and each of the one or more elastic wave resonators having a resonance frequency and an antiresonance frequency.
A substrate structure having one or more circuit boards, wherein one or more first inductors and one or more second inductors are configured by the conductors of the one or more circuit boards.
Have and
By the elastic wave chip and the substrate structure,
An elastic wave filter that attenuates a component having a frequency within at least a part of the blocking band among the signals flowing through the signal path,
A notch filter that connects the signal path and the reference potential portion and has a resonance frequency at which the impedance between the signal path and the reference potential portion becomes a minimum value is configured.
The elastic wave filter is
One or more series resonators including one or more elastic wave resonators constituting a part of the signal path, and one or more series resonators.
It has one or more first inductors, and has
The notch filter has one or more second inductors, and the notch filter has one or more second inductors.
A band-stop filter in which at least one antiresonance frequency of the one or more series resonators is located between the resonance frequency of the notch filter and the passband. The notch filter has one or more capacitors and has one or more capacitors.
The band-blocking filter according to claim 1, wherein the number of at least one of the one or more second inductors and the one or more capacitors is two or more. The notch filter is
The second inductor connecting the signal path and the reference potential portion,
A first capacitor connected in series with the second inductor between the signal path and the reference potential portion, and
The band-blocking filter according to claim 1 or 2, further comprising a second capacitor connected in parallel to the second inductor. The notch filter has one or more capacitors and has one or more capacitors.
The band blocking filter according to any one of claims 1 to 3, wherein at least one of the one or more capacitors is composed of a pair of comb tooth electrodes located on the elastic wave tip. The elastic wave filter is
A series arm having a plurality of the series resonators connected in series with each other in the signal path, and a series arm.
It has one or more intermediate positions between the plurality of series resonators among the series arms and one or more parallel arms connecting the reference potential portion.
At least one of the one or more parallel arms includes the first inductor connecting the intermediate position and the reference potential portion of the one or more first inductors, and the elastic wave resonance of the one or more. The bandwidth blocking filter according to any one of claims 1 to 4, which does not include any of the children. The elastic wave chip is mounted on one of the one or more circuit boards.
One of claims 1 to 5, wherein the circuit board on which the elastic wave chip is mounted has at least one of the one or more first inductors and the one or more second inductors. Band blocking filter as described in section. The band blocking filter according to any one of claims 1 to 6 and the band blocking filter.
It has a second pass band adjacent to the pass band side of the band pass filter with respect to the block band, and attenuates components having frequencies outside the second pass band among the signals flowing in the signal path. Bandpass filter and
A composite filter that has. The composite filter according to claim 7, wherein the bandpass filter is composed of the substrate structure. The composite filter according to claim 7 or 8,
An antenna that is electrically connected to either the input side or the output side of the composite filter,
An integrated circuit element electrically connected to the other of the input side and the output side of the composite filter,
Has a communication device.

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