Filter and multiplexer
阅读说明:本技术 滤波器以及多路复用器 (Filter and multiplexer ) 是由 加藤雅则 于 2019-06-03 设计创作,主要内容包括:本发明提供一种具有较宽的通带、较小的插入损耗以及通带端中的陡峭的衰减特性的滤波器。滤波器(10)具备:串联臂谐振器(11),构成连结端子(P1、P2)的信号路径(R)的至少一部分;并联臂谐振器(17),一端接地;电感器(15),一端与串联臂谐振器(11)的一端连接且另一端与并联臂谐振器(17)的另一端连接;以及电感器(16),一端与串联臂谐振器(11)的另一端连接且另一端与并联臂谐振器(17)的上述另一端连接,并联臂谐振器(17)的相对带宽比串联臂谐振器(11)的相对带宽小。(A type filter having a wide passband, a small insertion loss, and a steep attenuation characteristic at a passband end, the filter (10) is provided with a series arm resonator (11) constituting at least part of a signal path (R) connecting terminals (P1, P2), parallel arm resonators (17), 0 ends of which are grounded, an inductor (15), ends of which are connected to an end of the series arm resonator (11) and the other end of which is connected to the other end of the parallel arm resonator (17), and an inductor (16), end of which is connected to the other end of the series arm resonator (11) and the other end of which is connected to the other end of the parallel arm resonator (17), wherein the relative bandwidth of the parallel arm resonator (17) is smaller than the relative bandwidth of the series arm resonator (11).)
1, kinds of filters, comprising:
a series-arm resonator constituting at least a portion of a signal path connecting the th terminal and the second terminal;
a parallel arm resonator, wherein the end is grounded;
an th inductor having a terminal connected to the terminal of the series arm resonator and another terminal connected to the another terminal of the parallel arm resonator, and
a second inductor having an end connected to the other end of the series-arm resonator and an end connected to the other end of the parallel-arm resonator,
the relative bandwidth of the series-arm resonators is wider than the relative bandwidth of the parallel-arm resonators.
2. The filter of claim 1, wherein,
the parallel arm resonator has a substrate made of a piezoelectric material containing lithium niobate, transmits a signal by a Rayleigh wave propagating through the substrate,
the series-arm resonator has a substrate made of a piezoelectric material containing lithium niobate, and signals are transmitted by a love wave propagating through the substrate.
3. The filter of claim 1 or 2,
the filter has a third inductor for matching, the third inductor being connected to at least of a portion between the series-arm resonator and the th terminal of the signal path or a portion between the series-arm resonator and the second terminal of the signal path,
in the pass band of the filter, the Q value of the th inductor and the Q value of the second inductor are both higher than the Q value of the third inductor.
4. The filter of any of claims 1-3, wherein,
the th inductor and the second inductor are each a laminated chip inductor.
5. The filter of any of claims 1-4 wherein,
the inductance of the th inductor is greater than the inductance of the second inductor.
6. The filter of any of claims 1-5, wherein,
the filter has a passband of 2300MHz to 2400MHz, and 2496MHz to 2690MHz, and a stopband of 1427MHz to 2200 MHz.
A multiplexer of the type 7, , having:
the filter of claim 6, namely the th filter;
a second filter having a pass band above 1427MHz and below 2200 MHz; and
a third filter having a passband above 617MHz and below 960MHz,
a terminal of the th filter, a terminal of the second filter, and a terminal of the third filter are connected to each other.
8. The multiplexer of claim 7,
the second filter is composed of an LC resonance circuit and an elastic wave resonator,
the third filter is constituted by an LC resonant circuit.
Technical Field
The invention relates to a filter and a multiplexer.
Background
There are communication devices that support a plurality of frequency bands (multiband) and a plurality of wireless systems (multimode). In the front-end circuit of such a communication device, a multiplexer for demultiplexing and multiplexing signals of a plurality of frequency bands is used. The multiplexer is constituted by, for example, a plurality of filters having mutually different pass bands.
Fig. 13 is a circuit diagram showing examples of the high-frequency circuit disclosed in
The high-frequency circuit shown in fig. 13 includes an
Patent document 1: U.S. patent application publication No. 2016/0191014
Recently, against the background of the release of new frequency bands and narrow gaps between frequency bands, filters constituting multiplexers are required to have a wide pass band, a small insertion loss, and steep attenuation characteristics at pass band ends.
Disclosure of Invention
Therefore, an object of the present invention is to provide kinds of filters having a wide pass band, a small insertion loss, and a steep attenuation characteristic in the pass band end, and a multiplexer using such filters.
In order to achieve the above object, an filter according to the present invention includes a series arm resonator constituting at least 0 portion of a signal path connecting a terminal and a second terminal, a parallel arm resonator having a 1 end grounded, a 2 inductor having a end connected to an end of the series arm resonator and another end connected to another end of the parallel arm resonator, and a second inductor having an end connected to another end of the series arm resonator and another end connected to the another end of the parallel arm resonator, wherein a relative bandwidth of the series arm resonator is wider than a relative bandwidth of the parallel arm resonator.
According to the filter of the present invention, the resonance frequency of the series-arm resonator can be separated from the high-frequency end of the passband more greatly than in the case where the relative bandwidth of the series-arm resonator is set to a relatively narrow relative bandwidth equivalent to that of the parallel-arm resonator. Thus, even when the passband is wide, the resonance frequency of the series-arm resonator can be brought close to the antiresonance frequency of the parallel-arm resonator, and therefore, the reflection loss in the passband can be improved, and the insertion loss of the filter can be reduced. In addition, the steep attenuation characteristic at the passband end can be formed by the frequency characteristic of the parallel arm resonator which is narrow in relative bandwidth and whose impedance decreases steeply in the vicinity of the resonance frequency. As a result, a filter having a wide passband, a small insertion loss, and a steep attenuation characteristic at the passband end can be obtained.
Drawings
Fig. 1 is a block diagram showing examples of the configuration of a multiplexer using the filter of
Fig. 2 is a graph illustrating a pass characteristic required for the filter of
Fig. 3 is a circuit diagram showing examples of the configuration of a filter of a comparative example.
Fig. 4 is a graph showing examples of the pass characteristics of the filter of the comparative example.
Fig. 5 is a graph showing examples of resonance characteristics of a partial circuit of a filter of a comparative example.
Fig. 6A is a graph showing examples of reflection characteristics and pass characteristics of a partial circuit of a filter of a comparative example.
Fig. 6B is a graph showing examples of reflection characteristics and pass characteristics of a partial circuit of the filter of the comparative example.
Fig. 6C is a graph showing examples of the reflection characteristics and the pass characteristics of the entire filter of the comparative example.
Fig. 7 is a circuit diagram showing examples of the configuration of the filter according to
Fig. 8 is a graph showing examples of the pass characteristics of the filter according to
Fig. 9 is a graph showing examples of resonance characteristics of a partial circuit of the filter according to
Fig. 10A is a graph showing examples of reflection characteristics and pass characteristics of a partial circuit of the filter according to
Fig. 10B is a graph showing examples of reflection characteristics and pass characteristics of a partial circuit of the filter according to
Fig. 10C is a graph showing examples of the reflection characteristics and the pass characteristics of the entire filter of
Fig. 11 is a block diagram showing examples of the structure of the multiplexer according to
Fig. 12 is a graph showing examples of the passing characteristics of the multiplexer according to
Fig. 13 is a circuit diagram showing examples of a conventional high-frequency circuit.
Detailed Description
The numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection modes, and the like shown in the following embodiments are examples, and do not limit the present invention.
(embodiment mode 1)
The filter of
Fig. 1 is a block diagram showing examples of the configuration of a multiplexer using the filter of
In fig. 1, the frequency band is 2300MHz to 2690MHz and less, and the second frequency band is 1427MHz to 2200MHz as examples, and for convenience of reference, the frequency band of 2300MHz to 2690MHz is referred to as the high band HB, and the frequency band of 1427MHz to 2200MHz is referred to as the mid band MB.
The terminal of the
In the case where the
In order to realize such carrier aggregation, the
Fig. 2 is a graph for explaining examples of the pass characteristics required for the filter 10 (more precisely, between the antenna terminal ANT of the
The present inventors have studied to realize a filter having such a passband by using a conventional high-frequency circuit. The results of this study will be described below as comparative examples.
Fig. 3 is a circuit diagram showing examples of the configuration of a
Fig. 4 is a example graph showing the passing characteristics between the terminals P1 and P2 of the
As is clear from the broken line along the amplified waveform of fig. 4, the pass characteristic of the
Fig. 5 is a graph showing examples of resonance characteristics of a partial circuit of
The pass characteristic of fig. 4 is analyzed in more detail.
Fig. 6A is a graph showing examples of the reflection characteristic and the pass characteristic of the partial circuit B (in other words, elastic wave resonator 97) of the
Reference numerals fr and fa in fig. 6A denote the resonance frequency and the antiresonance frequency of the
The relative bandwidth of an elastic wave resonator is typically narrow. For example, the relative bandwidth of an elastic wave resonator (hereinafter, abbreviated as LN rely) that has a substrate made of a piezoelectric material containing lithium niobate and transmits a signal by a rayleigh wave propagating through the substrate is several%. Here, the relative bandwidth of the elastic wave resonator is a ratio of a difference between an anti-resonance frequency and a resonance frequency of the elastic wave resonator to a center frequency.
For example, by configuring
Fig. 6B is a graph showing examples of the reflection characteristic and the pass characteristic of the partial circuit C of the
Reference numerals fr and fa in fig. 6B denote the resonance frequency and the antiresonance frequency of the partial circuit C, respectively. The antiresonant frequency fa of the partial circuit C is located outside the high-frequency band HB on the high-frequency side. In the example of fig. 6B,
The relative bandwidth of the partial circuit C is slightly enlarged from the relative bandwidth of the
Fig. 6C is a graph showing examples of the reflection characteristic and the pass characteristic of the entire filter 90 a, where (a) shows the reflection characteristic and (B) shows the pass characteristic, the reflection characteristic and the pass characteristic of fig. 6C are formed by further the combination of the characteristics of the partial circuit B, C of fig. 6A and 6B, and by adding matching by the
As can be seen from the dotted circle in fig. 6C (a), the reflection loss of the entire a of the
As a result, as can be seen from the dotted circle in fig. 6C (b), the insertion loss in the entire filter 90 a has a waveform largely recessed in the high band HB, and the insertion loss increases (deteriorates) in the middle of the high band HB.
Based on such a study, a filter in which deterioration of the insertion loss is improved by alleviating the steepness of the frequency characteristic of
Fig. 7 is a circuit diagram showing examples of the configuration of the filter according to
The end of the
End of
End of inductor 16 is connected to end of
The end of the
The end of the
Fig. 8 is a example graph showing the passing characteristics between the terminals P1 and P2 of the
As is clear from the broken line along the enlarged waveform of fig. 8, the pass characteristic of the
Fig. 9 is a graph showing examples of resonance characteristics of a partial circuit of
Here, by configuring
The pass characteristics of fig. 8 are analyzed in more detail.
Fig. 10A is a graph showing examples of reflection characteristics and pass characteristics of the partial circuit B of the filter 10 (in other words, the elastic wave resonator 17), (a) showing reflection characteristics, and (B) showing pass characteristics, reference numerals fr and fa in fig. 10A respectively showing resonance frequencies and anti-resonance frequencies of the
As described with reference to fig. 6A, by configuring
Fig. 10B is a graph showing examples of the reflection characteristic and the pass characteristic of the partial circuit C of the
Therefore, in the
Fig. 10C is a graph showing examples of the reflection characteristic and the pass characteristic of the entire filter 10a, where (a) shows the reflection characteristic and (b) shows the pass characteristic.
As can be seen from the dotted circle in fig. 10C (a), the intermediate reflection loss of the high band HB is maintained larger than the reflection loss of the
As a result, as can be seen from the dotted circle in fig. 10C (b), the insertion loss in the entire filter 10a has a waveform without a large notch in the high band HB, and the insertion loss is reduced (improved) in the middle of the high band HB.
As described above, according to
Thereby, a filter having a wide passband, a small insertion loss, and a steep attenuation characteristic in the passband end can be obtained.
The configuration of the
For example, in the
Further, both of the
According to such a configuration, since inductors having a relatively high Q value (for example, higher than the Q values of
The inductance value of
With this configuration, the steepness of the attenuation characteristic at the low frequency side of the pass band can be further increased .
In the above description, the high-frequency band HB (or the th part and the second part included in the high-frequency band HB) is described as an example of the pass band of the
(embodiment mode 2)
The multiplexer of
Fig. 11 is a block diagram showing examples of the configuration of the multiplexer according to
In fig. 11, the passband of the
The passband of the
The terminal of the
The
Fig. 12 is a graph showing examples of the pass characteristic of the
The filter and the multiplexer according to the embodiments of the present invention have been described above, but the present invention is not limited to the respective embodiments, and a configuration in which various modifications that can be conceived are applied to the present embodiment by those skilled in the art, and a configuration in which constituent elements in different embodiments are combined and constructed may be included in or a plurality of embodiments of the present invention, as long as the configuration does not depart from the gist of the present invention.
(conclusion)
The filters of the present invention include a series-arm resonator constituting at least 0 part of a signal path connecting a terminal and a second terminal, a parallel-arm resonator having a 1 end grounded, a 2 inductor having a end connected to a end of the series-arm resonator and another end connected to another end of the parallel-arm resonator, and a second inductor having an end connected to another end of the series-arm resonator and another end connected to the another end of the parallel-arm resonator, wherein a relative bandwidth of the series-arm resonator is wider than a relative bandwidth of the parallel-arm resonator.
In a typical filter, the resonance frequency of the parallel-arm resonator is arranged at the low-frequency end of the passband, and the anti-resonance frequency of the series-arm resonator is arranged outside the high-frequency side of the passband. Therefore, if a resonator having a relatively narrow bandwidth is used for both the series-arm resonator and the parallel-arm resonator, the anti-resonance frequency of the parallel-arm resonator and the resonance frequency of the series-arm resonator are located close to both ends in the passband and are largely separated from each other. As a result, the reflection loss in the pass band deteriorates and the insertion loss increases. Such an increase in insertion loss is more significant the wider the passband.
Since it is effective to obtain steepness of frequency characteristics at the low frequency end of the passband to configure the parallel arm resonator by the resonator having a relatively narrow bandwidth, according to the above-described configuration, the series arm resonator is configured by the resonator having a relatively wide bandwidth compared to the parallel arm resonator.
With this configuration, the resonance frequency of the series-arm resonator can be largely separated from the high-frequency end of the passband, as compared with the case where the series-arm resonator is configured by a resonator having a relatively narrow bandwidth equivalent to the parallel-arm resonator. Thus, even when the passband is wide, the resonance frequency of the series-arm resonator and the anti-resonance frequency of the parallel-arm resonator can be brought close to each other.
As a result, the reflection loss in the pass band can be improved, and the insertion loss of the filter can be reduced. In addition, the steep attenuation characteristic at the passband end can be formed by the frequency characteristic of the parallel arm resonator which is narrow in relative bandwidth and whose impedance decreases steeply in the vicinity of the resonance frequency. As a result, a filter having a wide passband, a small insertion loss, and a steep attenuation characteristic at the passband end is obtained.
The parallel-arm resonator may have a substrate made of a piezoelectric material containing lithium niobate, and transmit a signal by a rayleigh wave propagating through the substrate, and the series-arm resonator may have a substrate made of a piezoelectric material containing lithium niobate, and transmit a signal by a love wave propagating through the substrate.
In such a configuration, it is known that an elastic wave resonator (LN rely) having a substrate made of a piezoelectric material containing lithium niobate and transmitting a signal by a rayleigh wave propagating through the substrate has particularly high steepness of frequency characteristics. Therefore, by forming the parallel arm resonators by LN rely, steeper attenuation characteristics can be formed at the low frequency end of the pass band of the filter.
It is also known that an elastic wave resonator (LN love) having a substrate made of a piezoelectric material containing lithium niobate and transmitting a signal by a love wave propagating through the substrate has a relative bandwidth wider than that of LN rely. Therefore, by configuring the series-arm resonator with LN love, the reflection loss in the pass band can be effectively improved, and the insertion loss of the filter can be reduced.
Further, the filter includes third inductors for matching connected to at least of a portion between the series-arm resonator and the -th terminal of the signal path or a portion between the series-arm resonator and the second terminal of the signal path, and both a Q value of the -th inductor and a Q value of the second inductor are higher than a Q value of the third inductor in a pass band of the filter.
According to such a configuration, since the th inductor and the second inductor use inductors having relatively high Q values, steepness of attenuation characteristics at the low frequency end of the pass band can be improved, and insertion loss can be reduced in a wide pass band.
The th inductor and the second inductor may be laminated chip inductors.
According to this configuration, the th inductor and the second inductor are constituted by the laminated chip inductor, and thereby, the Q values of the th inductor and the second inductor can be increased as compared with the case where the th inductor and the second inductor are formed by the pattern conductor in the substrate, and as a result, the insertion loss of the filter can be further reduced .
The inductance value of the th inductor may be larger than the inductance value of the second inductor.
With this configuration, the steepness of the attenuation characteristic at the low frequency side of the pass band can be further increased .
The filter may have a passband of 2300MHz to 2400MHz, a passband of 2496MHz to 2690MHz, and a stopband of 1427MHz to 2200 MHz.
With such a configuration, specifically, a filter in which the high-band and the middle-band mentioned in the present specification are a pass band and a stop band, respectively, is obtained. Such a filter is suitable as a filter for a high band in a multiplexer for demultiplexing and multiplexing a high band and a medium band.
The -mode multiplexer of the present invention has the filter, which is the above-mentioned filter, a second filter having a passband of 1427MHz to 2200MHz inclusive, and a third filter having a passband of 617MHz to 960MHz inclusive, and the terminal of the filter, the terminal of the second filter, and the terminal of the third filter are connected to each other.
With this configuration, a multiplexer is obtained which performs demultiplexing and multiplexing of the signals of 3 bands obtained by adding the low band mentioned in the present specification to the high band and the medium band.
The second filter may be constituted by an LC resonance circuit and an elastic wave resonator, and the third filter may be constituted by an LC resonance circuit.
By using the th filter and the second filter, the signal for the high band and the signal for the intermediate band are completely separated in frequency, and both signals can be simultaneously transmitted and received by the single antenna, whereby carrier aggregation communication based on a combination of the communication band included in the high band and the communication band included in the intermediate band can be performed by the single antenna.
The present invention can be widely applied to communication devices such as mobile phones as a filter and a multiplexer , for example.
Description of the reference numerals
1. A 2 … multiplexer; 10. 20, 30, 40, 90 … filters; 11. 91 … elastic wave resonator (series arm resonator); 17. 97 … elastic wave resonator (parallel arm resonator); 15. 16, 18, 19, 95, 96, 98, 99 … inductors.
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