Elastic wave filter circuit, multiplexer, front-end circuit, and communication device

Abstract

In a first frequency band for FDD constituted by a first downlink operating frequency band and a first uplink operating frequency band and a second frequency band for FDD constituted by a second downlink operating frequency band and a second uplink operating frequency band, from the low frequency side, the positions of the frequency bands are in the order of (1) the first downlink operating frequency band, the second downlink operating frequency band, the first uplink operating frequency band, and the second uplink operating frequency band, the frequency range of the first uplink operating frequency band and the frequency range of the second uplink operating frequency band do not overlap, and a filter (11) is formed on a first substrate having piezoelectricity, having a passband including the first uplink operating frequency band and the second uplink operating frequency band.

Description

Technical Field

[0001] This invention relates to an elastic wave filter circuit, a multiplexer, a front-end circuit, and a communication device. Background Technology

[0002] For front-end circuits that support multi-band and multi-mode operation, it is required to transmit and receive multiple high-frequency signals with low loss and high isolation.

[0003] Patent document 1 discloses a receiving module (transmitting circuit) with the following structure: multiple filters with different passbands are connected to the antenna via a multiplexer (switch).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: U.S. Patent Application Publication No. 2016 / 0127015 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In 3GPP (3rd Generation Partnership Project), for example, there are requirements for the simultaneous transmission of high-frequency signals in the 5G (5th generation)-NR (New Radio) band and the 4G (4th generation)-LTE (Long term Evolution) band.

[0009] When transmitting high-frequency signals in the first and second frequency bands with small frequency gaps, the front-end circuitry becomes larger when separate filters are applied to the first and second frequency bands to ensure isolation between them.

[0010] Therefore, the object of the present invention is to provide a small elastic wave filter circuit, multiplexer, front-end circuit and communication device that ensures isolation between two frequency bands with a small frequency gap.

[0011] Solution for solving the problem

[0012] Regarding the elastic wave filter circuit according to one aspect of the present invention, in a first frequency band for frequency division duplexing (FDD) consisting of a first downlink operating frequency band and a first uplink operating frequency band, and a second frequency band for FDD consisting of a second downlink operating frequency band and a second uplink operating frequency band, the positions of the frequency bands, starting from the low-frequency side or the high-frequency side, are in the order of (1) the first downlink operating frequency band, the second downlink operating frequency band, the first uplink operating frequency band, and the second uplink operating frequency band, or in the order of (2) the first downlink operating frequency band, the first uplink operating frequency band, the second uplink operating frequency band, and the second downlink operating frequency band. The frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. The elastic wave filter circuit is formed on a first substrate having piezoelectricity and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

[0013] Regarding the elastic wave filter circuit according to one aspect of the present invention, in a first frequency band for time division duplex (TDD) consisting of a first downlink operating frequency band and a first uplink operating frequency band, and a second frequency band for FDD consisting of a second downlink operating frequency band and a second uplink operating frequency band, the first downlink operating frequency band and the first uplink operating frequency band are in the same frequency range, and the position of the frequency bands, starting from the low-frequency side or the high-frequency side, follows the order of the first frequency band, the second uplink operating frequency band, and the second downlink operating frequency band. The frequency range of the first frequency band does not overlap with the frequency range of the second uplink operating frequency band. The elastic wave filter circuit is formed on a first piezoelectric substrate and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

[0014] Additionally, one embodiment of the present invention includes a multiplexer comprising: an antenna connection terminal; an elastic wave filter circuit according to the above description, which is connected to the antenna connection terminal; and a first filter circuit, which is connected to the antenna connection terminal and has a passband including a first downlink operating frequency band and a second downlink operating frequency band, wherein the first filter circuit is formed on a second substrate different from the first substrate.

[0015] Additionally, one embodiment of the present invention includes a multiplexer comprising: an antenna connection terminal; an elastic wave filter circuit as described above, which is connected to the antenna connection terminal; and a first filter circuit, which is connected to the antenna connection terminal and has a passband including a first downlink operating frequency band and a second downlink operating frequency band, wherein the electrode constituting the elastic wave filter circuit is in contact with a first dielectric layer formed on a first substrate, and the electrode constituting the first filter circuit is in contact with a second dielectric layer formed on the first substrate that is different from the first dielectric layer.

[0016] Additionally, one embodiment of the present invention includes a front-end circuit comprising: an antenna connection terminal; an elastic wave filter circuit as described above, connected to the antenna connection terminal; a second filter circuit, connected to the antenna connection terminal, having a passband including a third uplink operating frequency band, the frequency of which does not overlap with the frequencies of the first and second frequency bands; a power amplifier capable of amplifying high-frequency signals of the first, second, and third frequency bands; a switch for switching the connection between the elastic wave filter circuit and the power amplifier, and the connection between the second filter circuit and the power amplifier; and an impedance matching circuit connected between the power amplifier and the switch, capable of changing the impedance corresponding to the switching of the switch.

[0017] In addition, one aspect of the communication device according to the present invention includes: a signal processing circuit that processes high-frequency signals; and a front-end circuit according to the above description that transmits high-frequency signals between the signal processing circuit and the antenna.

[0018] The effects of the invention

[0019] According to the present invention, a small elastic wave filter circuit, multiplexer, front-end circuit, and communication device can be provided that ensures isolation between two frequency bands with a small frequency gap. Attached Figure Description

[0020] Figure 1 This is a circuit structure diagram of the front-end circuit and communication device involved in the implementation method.

[0021] Figure 2 This is a graph showing the correlation of frequency bands in the implementation method.

[0022] Figure 3A This is a diagram illustrating a first example of a combination of frequency bands in an implementation scheme.

[0023] Figure 3B This is a diagram illustrating a second example of a combination of frequency bands in an implementation scheme.

[0024] Figure 3C This is a diagram illustrating a third example of a combination of frequency bands in an embodiment.

[0025] Figure 3D This is a diagram illustrating a fourth example of a combination of frequency bands in an embodiment.

[0026] Figure 3E This is a diagram illustrating a fifth example of a combination of frequency bands in an embodiment.

[0027] Figure 4 This is a diagram showing the required specifications for the frequency temperature coefficient of the elastic wave filter circuit in the embodiment.

[0028] Figure 5This is a diagram showing the configuration of NS-07 in the first example of the combination of frequency bands in the implementation. Detailed Implementation

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Furthermore, the embodiments described below are general or specific examples. The numerical values, shapes, materials, constituent elements, arrangements of constituent elements, and connection methods shown in the following embodiments are examples and are not intended to limit the present invention.

[0030] Furthermore, the figures are schematic diagrams with appropriate emphasis, omission, or ratio adjustments for illustrating the invention, and are not necessarily strictly illustrative. Sometimes the shapes, positional relationships, and ratios differ from the actual shapes, positional relationships, and ratios. In the figures, substantially identical structures are sometimes labeled with the same reference numerals, and repeated descriptions are omitted or simplified.

[0031] In this disclosure, "connection" means not only direct connection via connection terminals and / or wiring conductors, but also electrical connection via other circuit elements. Furthermore, "connected between A and B" means connected to A and B along the path that connects A and B.

[0032] (Implementation Method)

[0033] [1 Circuit structure of front-end circuit 1 and communication device 5]

[0034] Reference Figure 1 The circuit structure of the front-end circuit 1 and the communication device 5 involved in this embodiment will be explained. Figure 1 This is a circuit structure diagram of the front-end circuit 1 and the communication device 5 involved in the implementation method.

[0035] [1.1 Circuit structure of communication device 5]

[0036] First, the circuit structure of communication device 5 will be explained. For example... Figure 1 As shown, the communication device 5 according to this embodiment includes a front-end circuit 1, an antenna 2, an RF signal processing circuit (RFIC) 3, and a baseband signal processing circuit (BBIC) 4.

[0037] Front-end circuit 1 transmits high-frequency signals between antenna 2 and RFIC 3. The detailed circuit structure of front-end circuit 1 will be described later.

[0038] Antenna 2 is connected to antenna connection terminal 100 of front-end circuit 1 to transmit high-frequency signals output from front-end circuit 1. In addition, it receives high-frequency signals from the outside and outputs the high-frequency signals back to front-end circuit 1.

[0039] RFIC 3 is an example of a signal processing circuit that processes high-frequency signals. Specifically, RFIC 3 processes the high-frequency received signal input via the receiving path of front-end circuit 1 through down-conversion or the like, and outputs the resulting received signal to BBIC 4. Additionally, RFIC 3 processes the transmitted signal input from BBIC 4 through up-conversion or the like, and outputs the resulting high-frequency transmitted signal to the transmitting path of front-end circuit 1. Furthermore, RFIC 3 has a control unit that controls the switches and amplifiers in front-end circuit 1. Moreover, the functions of the control unit in RFIC 3, or all of them, can be installed externally to RFIC 3, for example, on BBIC 4 or front-end circuit 1.

[0040] BBIC 4 is a baseband signal processing circuit that uses an intermediate frequency band with a frequency lower than that of the high-frequency signal transmitted by front-end circuit 1 for signal processing. Signals processed by BBIC 4 include, for example, image signals used for displaying images and / or sound signals used for communication via a speaker.

[0041] Furthermore, in the communication device 5 according to this embodiment, the antenna 2 and BBIC 4 are not essential components.

[0042] [1.2 Circuit Structure of Front-End Circuit 1]

[0043] Next, the circuit structure of front-end circuit 1 will be described. For example... Figure 1 As shown, the front-end circuit 1 includes filters 11, 12, 21 and 22, a power amplifier 51, a low-noise amplifier 52, switches 30, 31 and 32, a matching circuit 41, an antenna connection terminal 100, a high-frequency input terminal 110 and a high-frequency output terminal 120.

[0044] Antenna connection terminal 100 is connected to antenna 2. High-frequency input terminal 110 is used to receive high-frequency transmitted signals from outside the front-end circuit 1. High-frequency output terminal 120 is used to provide high-frequency received signals to outside the front-end circuit 1.

[0045] The power amplifier 51 amplifies the high-frequency transmission signals (hereinafter referred to as transmission signals) input from the high-frequency input terminal 110 in the first, second, and third frequency bands. The power amplifier 51 is connected between the high-frequency input terminal 110 and the switch 31.

[0046] The low-noise amplifier 52 amplifies the high-frequency received signals (hereinafter referred to as received signals) of the first, second, and third frequency bands input from the antenna connection terminal 100. The low-noise amplifier 52 is connected between the high-frequency output terminal 120 and the switch 32.

[0047] Furthermore, each of the first, second, and third frequency bands refers to a frequency band predefined by standardization organizations (such as 3GPP, IEEE (Institute of Electrical and Electronics Engineers), etc.) for communication systems built using Radio Access Technology (RAT). In this embodiment, the communication system can be, for example, an LTE system, a 5G-NR system, and a WLAN (Wireless Local Area Network) system, but is not limited to these systems.

[0048] The first frequency band consists of the first downlink operating frequency band and the first uplink operating frequency band. The second frequency band consists of the second downlink operating frequency band and the second uplink operating frequency band. The third frequency band consists of the third downlink operating frequency band and the third uplink operating frequency band.

[0049] Furthermore, the uplink operating frequency band refers to the frequency range within the aforementioned bands designated for uplink use. Similarly, the downlink operating frequency band refers to the frequency range within the aforementioned bands designated for downlink use.

[0050] In the front-end circuit 1 of this embodiment, the first frequency band is, for example, frequency band B13 used for LTE in Frequency Division Duplex (FDD), the second frequency band is, for example, frequency band B14 used for LTE in FDD, and the third frequency band is, for example, frequency band B8 used for LTE in FDD.

[0051] Filter 11 is an example of an elastic wave filter circuit, having a passband that includes a first uplink operating frequency band (first transmit band) of a first frequency band and a second uplink operating frequency band (second transmit band) of a second frequency band. Filter 11 is connected to antenna connection terminal 100 via switch 30. Filter 11 is a surface acoustic wave filter, or an elastic wave filter using BAW (Bulk Acoustic Wave).

[0052] Filter 12 is an example of a first filter circuit, having a passband that includes a first downlink operating frequency band (first receive band) of a first frequency band and a second downlink operating frequency band (second receive band) of a second frequency band. Filter 12 is connected to antenna connection terminal 100 via switch 30.

[0053] Filter 21 is an example of a second filter circuit, having a passband that includes a third uplink operating frequency band. Filter 21 is connected to antenna connection terminal 100 via switch 30.

[0054] Filter 22 has a passband that includes the third downlink operating frequency band of the third frequency band. Filter 22 is connected to antenna connection terminal 100 via switch 30.

[0055] In addition, filters 21 and 22 can also be configured as a duplexer to allow the transmission and reception signals of the third frequency band to pass through.

[0056] Switch 30 has four SPST (Single Pole Single Throw) type switching elements. One terminal of each switching element is connected to the antenna connection terminal 100. The other terminal of each switching element is connected to filters 11, 12, 21, or 22, respectively. According to this structure, switch 30 can, for example, switch the connection between antenna connection terminal 100 and filter 11, between antenna connection terminal 100 and filter 12, between antenna connection terminal 100 and filter 21, and between antenna connection terminal 100 and filter 22 based on control signals from RFIC 3. Furthermore, the number of switching elements in switch 30 can be appropriately set according to the number of filters in the front-end circuit 1.

[0057] Switch 31 is connected between filters 11 and 21 and power amplifier 51. Specifically, switch 31 has a common terminal and two selection terminals. The common terminal of switch 31 is connected to the output terminal of power amplifier 51 via matching circuit 41. The two selection terminals of switch 31 are connected to filters 11 and 21 respectively. According to this connection structure, switch 31 can switch the connection between filter 11 and power amplifier 51 and the connection between filter 21 and power amplifier 51, for example, based on a control signal from RFIC 3.

[0058] Switch 32 is connected between filters 12 and 22 and low-noise amplifier 52. Specifically, switch 32 has a common terminal and two selection terminals. The common terminal of switch 32 is connected to the input terminal of low-noise amplifier 52. The two selection terminals of switch 32 are connected to filters 12 and 22 respectively. According to this connection structure, switch 32 can switch the connection between filter 12 and low-noise amplifier 52 and the connection between filter 22 and low-noise amplifier 52, for example, based on a control signal from RFIC 3.

[0059] Matching circuit 41 is an example of an impedance matching circuit, connected between power amplifier 51 and switch 31, and can change the impedance in response to the switching of switch 31.

[0060] Alternatively, switch 30 may be omitted, and filters 11, 12, 21, and 22 may be directly connected to antenna connection terminal 100.

[0061] Furthermore, the filters 11 and 12 and the switch 30 in the above-described structure of the front-end circuit 1 constitute a multiplexer. Alternatively, the multiplexer may not have the switch 30, and the filters 11 and 12 may be directly connected to the antenna connection terminal 100.

[0062] in addition, Figure 1 Some of the circuit elements shown may not be included in the front-end circuit 1. For example, the front-end circuit 1 may only have filters 11 and 21, power amplifier 51, switch 31 and matching circuit 41, or it may not have other circuit elements.

[0063] [1.3 Frequency Band Correlation]

[0064] Next, the correlation between the first frequency band, the second frequency band, and the third frequency band in this embodiment will be explained. Figure 2 This is a graph showing the correlation of frequency bands in the implementation method.

[0065] like Figure 2 As shown, the first frequency band is B13, used for LTE in FDD applications. The first downlink operating frequency band is 746MHz-756MHz, and the first uplink operating frequency band is 777MHz-787MHz. The second frequency band is B14, used for LTE in FDD applications. The second downlink operating frequency band is 758MHz-768MHz, and the second uplink operating frequency band is 788MHz-798MHz. The third frequency band is B8, used for LTE in FDD applications. The third downlink operating frequency band is 925MHz-960MHz, and the third uplink operating frequency band is 880MHz-915MHz.

[0066] In other words, in the first and second frequency bands, starting from the low-frequency side, the frequency band positions are in the order of (1) the first downlink operating frequency band, the second downlink operating frequency band, the first uplink operating frequency band, and the second uplink operating frequency band. The frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. Furthermore, there is a frequency gap (TT-Gap: 1MHz) between the first and second uplink operating frequency bands. In addition, the frequency of the third frequency band does not overlap with the frequencies of the first and second frequency bands.

[0067] The filter 11 involved in this embodiment is a filter having a passband (Co-band) that includes a first uplink operating frequency band of a first frequency band and a second uplink operating frequency band of a second frequency band.

[0068] The following describes application examples of the first and second frequency bands in this embodiment.

[0069] Figure 3A This is a diagram illustrating a first example of a combination of frequency bands in an embodiment. The diagram shows... Figure 2 The example shown is an application of the first and second frequency bands. That is, the first frequency band is band B13 used for LTE in FDD, and the second frequency band is band B14 used for LTE in FDD. In the first and second frequency bands, starting from the low-frequency side, the positions of the frequency bands are in the order of (1) first downlink operating band (R), second downlink operating band (R), first uplink operating band (T), and second uplink operating band (T) (RRTT), with a frequency gap (TT-Gap: 1MHz) between the first uplink operating band and the second uplink operating band. In this example, filter 11 is a filter with a passband (co-band) that includes the uplink operating band of band B13 and the uplink operating band of band B14.

[0070] Figure 3B This is a diagram illustrating a second example of the combination of frequency bands in the implementation. The first frequency band is band B13 for LTE used in FDD, with the first downlink operating band at 746MHz-756MHz and the first uplink operating band at 777MHz-787MHz. The second frequency band is band B26 for LTE used in FDD, with the second downlink operating band at 859MHz-894MHz and the second uplink operating band at 814MHz-849MHz. In the first and second frequency bands, starting from the lower frequency side, the positions of the frequency bands are in the order of (1) first downlink operating band (R), first uplink operating band (T), second uplink operating band (T), and second downlink operating band (R) (RTTR), with a frequency gap (TT-Gap: 27MHz) between the first and second uplink operating bands. In this example, filter 11 becomes a passband (co-band) filter that includes the uplink operating band of band B13 and the uplink operating band of band B26.

[0071] Figure 3CThis is a diagram illustrating a third example of the combination of frequency bands in the implementation. The first frequency band is FDD-based LTE band B11, with the first uplink operating frequency band at 1427.9MHz-1447.9MHz and the first downlink operating frequency band at 1475.9MHz-1495.9MHz. The second frequency band is FDD-based LTE band B21, with the second uplink operating frequency band at 1447.9MHz-1462.9MHz and the second downlink operating frequency band at 1495.9MHz-1510.9MHz. In the first and second frequency bands, starting from the lower frequency side, the frequency band positions are in the order of (1) first uplink operating frequency band (T), second uplink operating frequency band (T), first downlink operating frequency band (R), and second downlink operating frequency band (R) (TTRR), and the frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. Furthermore, the frequency gap (TT-Gap) between the first uplink operating band and the second uplink operating band is 0 MHz. In this example, filter 11 becomes a filter with a passband (co-band) including the uplink operating band of band B11 and the uplink operating band of band B21.

[0072] Figure 3D This is a diagram illustrating a fourth example of the combination of frequency bands in the implementation. The first frequency band is FDD-based LTE band B71, with the first uplink operating frequency band at 663MHz-698MHz and the first downlink operating frequency band at 617MHz-652MHz. The second frequency band is FDD-based LTE band B68, with the second uplink operating frequency band at 698MHz-728MHz and the second downlink operating frequency band at 753MHz-783MHz. In the first and second frequency bands, starting from the lower frequency side, the frequency band positions are in the order of (1) first downlink operating frequency band (R), first uplink operating frequency band (T), second uplink operating frequency band (T), and second downlink operating frequency band (R) (RTTR), and the frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. Furthermore, the frequency gap (TT-Gap) between the first and second uplink operating frequency bands is 0MHz. In this example, filter 11 becomes a passband (co-band) filter that includes the uplink operating band of band B71 and the uplink operating band of band B68.

[0073] Figure 3EThis is a diagram illustrating the fifth example of a combination of frequency bands in the implementation. The first frequency band is band B52 for LTE used in Time Division Duplex (TDD), with the first uplink operating band and the first downlink operating band in the same frequency range, both 3300MHz-3400MHz. The second frequency band is band B22 for LTE used in FDD, with the second uplink operating band at 3410MHz-3490MHz and the second downlink operating band at 3510MHz-3590MHz. In the first and second frequency bands, starting from the lower frequency side, the positions of the frequency bands are in the order of (1) the first frequency band (first downlink operating band and first uplink operating band), the second uplink operating band (T), and the second downlink operating band (R) (TR-TR), with a frequency gap (TT-Gap: 10MHz) between the first uplink operating band and the second uplink operating band. In this example, filter 11 becomes a filter having a passband (co-band) that includes the uplink operating band (and downlink operating band) of band B52 and the uplink operating band of band B22.

[0074] Furthermore, the first and second frequency bands in the first to fifth examples above are frequency bands used for LTE, but the first and second frequency bands in the first to fifth examples can also be frequency bands used for NR.

[0075] [1.4 Filter Structure]

[0076] The structure of filters 11 and 12 under the frequency relationship between the first and second frequency bands as described above is explained.

[0077] Filter 11 is an elastic wave filter formed on a first substrate with piezoelectricity, having a passband that includes a first uplink operating frequency band and a second uplink operating frequency band.

[0078] Based on the frequency relationship between the first and second frequency bands described above, the first uplink operating frequency band and the second uplink operating frequency band are adjacent to each other, rather than sandwiching the first and second downlink operating frequency bands. Therefore, when filter 11 is constructed using a surface acoustic wave (SAW) filter, a passband encompassing both the first and second uplink operating frequency bands can be formed using a common IDT (Interdigital Transducer) electrode. Furthermore, since it is a SAW filter, the downlink operating frequency band adjacent to the passband can be rapidly attenuated. Therefore, a small SAW filter circuit can be realized that sufficiently attenuates adjacent downlink operating frequency bands and uses the two uplink operating frequency bands as a common passband.

[0079] Furthermore, it is desirable for the filter 11 to have a small temperature coefficient of frequency (TCF), preferably below 10 ppm / ℃. Accordingly, even if the temperature of the filter 11 increases due to the passage of a high-output transmit signal, frequency drift in the pass-through characteristics of the filter 11 can be suppressed. Therefore, a large attenuation in the downlink operating frequency band of the filter 11 can be ensured.

[0080] Figure 4 This is a diagram illustrating the required specifications for the frequency temperature coefficient (TCF) of filter 11 in the embodiment. The diagram shows the permissible amount when the pass characteristics of filter 11 change frequency due to temperature variations.

[0081] In the attenuation band near the lower frequency side of the passband of filter 11, there is a concern that the passband will shift towards the lower frequency side at high temperatures (+85°C), resulting in a deterioration in attenuation. In this case, it is desirable that the shift of the characteristics towards the lower frequency side is within 1 / 4 of the frequency gap TR-Gap between the first uplink operating frequency band (B13Tx) of the low-frequency band B13 constituting the passband of filter 11 and the second downlink operating frequency band (B14Rx) of the adjacent low-frequency band B14.

[0082] Furthermore, in the attenuation band closer to the high-frequency side of the passband of filter 11, there is a concern that the attenuation will deteriorate due to the passband shifting towards the high-frequency side at low temperatures (-35°C). In this case, it is desirable that the shift of the characteristics towards the high-frequency side is within 1 / 4 of the frequency gap TR-Gap between the second uplink operating frequency band (B14Tx) of the high-frequency band B14 constituting the passband of filter 11 and the adjacent attenuation band on the high-frequency side.

[0083] In other words, it is desirable that, when the center frequency of the passband of filter 11 is set to f0 (Hz), the frequency gap between the first uplink operating frequency band and the first downlink operating frequency band or the second downlink operating frequency band adjacent to the first uplink operating frequency band is set to fgap (Hz), and the maximum temperature change relative to normal temperature (25℃) is set to ΔT, the frequency temperature coefficient TCF (ppm / ℃) of filter 11 satisfies the following relationship.

[0084] TCF≤|[(f0±fgap / 4)-fO] / f0 / ΔT×1000000| (Equation 1)

[0085] Accordingly, the filter 11 can ensure a large attenuation of the low-frequency passband at high temperatures and a large attenuation of the high-frequency passband at low temperatures.

[0086] Especially when the first and second frequency bands are NR bands, the required EVM (Error Vector Magnitude) is stringent, necessitating greater isolation between the transmitted and received signals. To address this, by setting the frequency temperature coefficient (TCF) of filter 11 to satisfy Equation 1, the EVM of the received signals in both the first and second frequency bands can be reduced.

[0087] Figure 5 This diagram illustrates the configuration of NS_07 in a first example of the frequency band combination in the embodiment. In the case where the first and second frequency bands are combined as in the first example, NS_07 (769MHz-775MHz) exists between the second downlink operating frequency band (758MHz-768MHz) and the first uplink operating frequency band (777MHz-787MHz). The unwanted radiation level in this NS_07 must be below a specified value. To this end, by setting the frequency temperature coefficient (TCF) of filter 11 to satisfy Equation 1, the unwanted radiation level in NS_07 can be kept below the specified value.

[0088] Furthermore, the front-end circuit 1 involved in this embodiment includes: an antenna connection terminal 100; a filter 11 connected to the antenna connection terminal 100; a filter 21 connected to the antenna connection terminal 100, having a passband including a third uplink operating frequency band, the frequency of which does not overlap with the frequencies of the first and second frequency bands; a power amplifier 51 capable of amplifying high-frequency signals of the first, second, and third frequency bands; a switch 31 for switching the connection between the filter 11 and the power amplifier 51 and the connection between the filter 21 and the power amplifier 51; and a matching circuit 41 connected between the power amplifier 51 and the switch 31, capable of changing the impedance corresponding to the switching of the switch 31.

[0089] Accordingly, when the filter 11 is connected to the power amplifier 51, the impedance of the matching circuit 41 can be adjusted to minimize the signal distortion of the power amplifier 51, thus ensuring a large attenuation of the attenuation band adjacent to the first uplink operating frequency band and the second uplink operating frequency band.

[0090] Alternatively, filter 11 may be formed on the first substrate, and filter 12 may be formed on a second substrate different from the first substrate.

[0091] Accordingly, filter 11 is formed on the first substrate from the viewpoint of minimizing the temperature coefficient of frequency (TCF). In contrast, filter 12 is not limited to being formed on the first substrate, as it does not have the limitation of minimizing the TCF. Therefore, the design freedom of the electrode parameters, etc., of filter 12 is increased.

[0092] Alternatively, the electrodes constituting filter 11 may be in contact with a first dielectric layer formed on the first substrate, and the electrodes constituting filter 12 may be in contact with a second dielectric layer formed on the first substrate, which is different from the first dielectric layer. The first and second dielectric layers may be made of, for example, a material whose main component is silicon dioxide.

[0093] In the case where filter 11 is a surface acoustic wave filter, a dielectric layer is formed on a piezoelectric substrate or piezoelectric layer. This dielectric layer is formed in contact with the IDT electrode formed on the piezoelectric substrate or piezoelectric layer, and has functions such as (1) protecting the IDT electrode from the influence of the external environment; (2) adjusting the frequency temperature coefficient (TCF) of filter 11; and (3) improving moisture resistance. The dielectric layer can preferentially exhibit any of the functions (1) to (3) mentioned above by making the chemical composition or film thickness different.

[0094] Accordingly, the electrodes constituting filter 11 are in contact with the first dielectric layer for the purpose of minimizing the temperature coefficient of frequency (TCF). In contrast, filter 12 is not subject to the same limitation of minimizing the TCF. Therefore, the electrodes constituting filter 12 are in contact with a second dielectric layer whose chemical composition or film thickness differs from that of the first dielectric layer. This increases the design freedom of the electrode parameters of filter 12. For example, since filter 12 is not subject to the limitation of minimizing the TCF, the piezoelectric substrate or piezoelectric layer can be designed from the perspective of suppressing unwanted waves.

[0095] [1.5 effects, etc.]

[0096] As described above, in the first frequency band for FDD consisting of the first downlink operating frequency band and the first uplink operating frequency band, and the second frequency band for FDD consisting of the second downlink operating frequency band and the second uplink operating frequency band, starting from the low frequency side, the positions of the frequency bands are in the order of (1) the first downlink operating frequency band, the second downlink operating frequency band, the first uplink operating frequency band, and the second uplink operating frequency band. The frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. The filter 11 involved in this embodiment is formed on a first substrate with piezoelectricity and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

[0097] Accordingly, the first uplink operating frequency band and the second uplink operating frequency band are adjacent to each other, rather than sandwiching the first downlink operating frequency band and the second downlink operating frequency band. Therefore, when filter 11 is constructed using a surface acoustic wave (SAW) filter, a passband encompassing both the first and second uplink operating frequency bands can be formed using a common IDT electrode. Furthermore, since it is a SAW filter, the downlink operating frequency band adjacent to the passband can be rapidly attenuated. Therefore, a small SAW filter circuit can be realized that sufficiently attenuates adjacent downlink operating frequency bands and uses the two uplink operating frequency bands as a common passband.

[0098] Alternatively, for example, the first frequency band could be B13, which is used for LTE, and the second frequency band could be B14, which is used for LTE.

[0099] Alternatively, in the first frequency band for TDD consisting of the first downlink operating frequency band and the first uplink operating frequency band, and the second frequency band for FDD consisting of the second downlink operating frequency band and the second uplink operating frequency band, the first downlink operating frequency band and the first uplink operating frequency band are in the same frequency range. Starting from the low frequency side, the position of the frequency band is in the order of the first frequency band, the second uplink operating frequency band, and the second downlink operating frequency band. The frequency range of the first frequency band does not overlap with the frequency range of the second uplink operating frequency band. The filter 11 is formed on a piezoelectric first substrate and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

[0100] Accordingly, the first frequency band used for TDD and the second uplink operating frequency band used for FDD are adjacent to each other instead of sandwiching the second downlink operating frequency band. Therefore, when filter 11 is constructed using a surface acoustic wave (SAW) filter, a passband encompassing both the first and second uplink operating frequency bands can be formed using a common IDT electrode. Furthermore, since it is a SAW filter, the downlink operating frequency band adjacent to the passband can be sharply attenuated. Thus, a small SAW filter circuit can be realized that sufficiently attenuates adjacent downlink operating frequency bands and uses the two uplink operating frequency bands as a common passband.

[0101] Alternatively, for example, the first frequency band could be B52, which is used for LTE, and the second frequency band could be B22, which is used for LTE.

[0102] Alternatively, in the filter 11 of this embodiment, when the center frequency of the passband is set to f0 (Hz), the frequency gap between the first uplink operating frequency band and the first downlink operating frequency band or the second downlink operating frequency band adjacent to the first uplink operating frequency band is set to fgap (Hz), and the maximum temperature change amplitude relative to room temperature is set to ΔT, the frequency temperature coefficient TCF (ppm / ℃) of the filter 11 satisfies the following relationship.

[0103] TCF≤|[(f0±fgap / 4)-f0] / f0 / ΔT|1000000| (Formula 1)

[0104] Accordingly, the filter 11 can ensure a large attenuation of the low-frequency passband at high temperatures and a large attenuation of the high-frequency passband at low temperatures.

[0105] In addition, the multiplexer involved in this embodiment includes: an antenna connection terminal 100; a filter 11 connected to the antenna connection terminal 100; and a filter 12 connected to the antenna connection terminal 100, having a passband including a first downlink operating frequency band and a second downlink operating frequency band, wherein the filter 12 is formed on a second substrate different from the first substrate.

[0106] Accordingly, filter 11 is formed on the first substrate to minimize the temperature coefficient of frequency (TCF), while filter 12 is not limited to being formed on the first substrate due to the limitation of minimizing the TCF. Therefore, the design freedom for the electrode parameters, etc., of filter 12 is increased. Consequently, a compact multiplexer that ensures isolation between the transmitted and received signals can be realized.

[0107] Furthermore, the multiplexer involved in this embodiment includes: an antenna connection terminal 100; a filter 11 connected to the antenna connection terminal 100; and a filter 12 connected to the antenna connection terminal 100, having a passband including a first downlink operating frequency band and a second downlink operating frequency band, wherein the electrode constituting the filter 11 is in contact with a first dielectric layer formed on a first substrate, and the electrode constituting the circuit of the filter 12 is in contact with a second dielectric layer formed on the first substrate that is different from the first dielectric layer.

[0108] Accordingly, the electrodes constituting filter 11 are in contact with the first dielectric layer for the purpose of minimizing the temperature coefficient of frequency (TCF). In contrast, filter 12 is not subject to the same limitation of minimizing the TCF. Therefore, the electrodes constituting filter 12 are in contact with the second dielectric layer, thereby increasing the design freedom of the electrode parameters of filter 12. For example, since filter 12 is not subject to the limitation of minimizing the TCF, the piezoelectric substrate or piezoelectric layer can be designed from the perspective of suppressing unwanted waves.

[0109] Alternatively, the front-end circuit 1 involved in this embodiment may include: an antenna connection terminal 100; a filter 11 connected to the antenna connection terminal 100; a filter 21 connected to the antenna connection terminal 100, having a passband including a third uplink operating frequency band, the frequency of which does not overlap with the frequencies of the first and second frequency bands; a power amplifier 51 capable of amplifying high-frequency signals of the first, second, and third frequency bands; a switch 31 for switching the connection between the filter 11 and the power amplifier 51 and the connection between the filter 21 and the power amplifier 51; and a matching circuit 41 connected between the power amplifier 51 and the switch 31, capable of changing the impedance corresponding to the switching of the switch 31.

[0110] Accordingly, when the filter 11 is connected to the power amplifier 51, the impedance of the matching circuit 41 can be adjusted to minimize the signal distortion of the power amplifier 51, thus ensuring a large attenuation of the attenuation band adjacent to the first uplink operating frequency band and the second uplink operating frequency band.

[0111] In addition, the communication device 5 according to this embodiment includes: an RFIC 3 that processes high-frequency signals; and a front-end circuit 1 that transmits high-frequency signals between the RFIC 3 and the antenna 2.

[0112] Accordingly, the communication device 5 can achieve the same effect as the front-end circuit 1 described above.

[0113] (Other implementation methods)

[0114] The elastic wave filter circuit, multiplexer, front-end circuit, and communication device according to the present invention have been described above based on embodiments. However, the elastic wave filter circuit, multiplexer, front-end circuit, and communication device according to the present invention are not limited to the above embodiments. Other embodiments implemented by combining any of the constituent elements in the above embodiments, variations obtained by implementing various modifications of the above embodiments as conceived by those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above elastic wave filter circuit, multiplexer, front-end circuit, and communication device are also included in the present invention.

[0115] For example, in the circuit structure of the elastic wave filter circuit, multiplexer, front-end circuit, and communication device involved in the above embodiments, other circuit elements and wiring may be inserted between the paths connecting the circuit elements and signal paths shown in the figures.

[0116] Furthermore, while the above embodiments use frequency bands for 5G-NR or LTE, communication frequency bands for other wireless access technologies can also be used, or communication frequency bands for other wireless access technologies can be used instead of the frequency bands for 5G-NR or LTE. For example, communication frequency bands for wireless local area networks can also be used. Additionally, millimeter-wave bands above 7 GHz can also be used. In this case, the front-end circuit 1, antenna 2, and RFIC 3 can constitute a millimeter-wave antenna module, and a distributed constant type filter can be used, for example, as the filter.

[0117] Industrial availability

[0118] This invention, as a high-frequency circuit configured in the front end, can be widely used in communication devices such as portable telephones.

[0119] Explanation of reference numerals in the attached figures

[0120] 1: Front-end circuit; 2: Antenna; 3: RF signal processing circuit (RFIC); 4: Baseband signal processing circuit (BBIC); 5: Communication device; 11, 12, 21, 22: Filters; 30, 31, 32: Switches; 41: Matching circuit; 51: Power amplifier; 52: Low noise amplifier; 100: Antenna connection terminal; 110: High-frequency input terminal; 120: High-frequency output terminal.

Claims

1. An elastic wave filter circuit, wherein, In the first frequency band used for frequency division duplexing (FDD), which consists of the first downlink operating frequency band and the first uplink operating frequency band, and the second frequency band used for FDD, which consists of the second downlink operating frequency band and the second uplink operating frequency band, the frequency band positions, starting from the low-frequency side or the high-frequency side, are in the order of (1) the first downlink operating frequency band, the second downlink operating frequency band, the first uplink operating frequency band, and the second uplink operating frequency band, or in the order of (2) the first downlink operating frequency band, the first uplink operating frequency band, the second uplink operating frequency band, and the second downlink operating frequency band. The frequency range of the first uplink operating frequency band does not overlap with the frequency range of the second uplink operating frequency band. The elastic wave filter circuit is formed on a first substrate with piezoelectric properties and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

2. The elastic wave filter circuit according to claim 1, wherein, The first frequency band is B13, which is used for LTE. The second frequency band is B14, which is used for LTE.

3. An elastic wave filter circuit, wherein, In the first frequency band used for Time Division Duplex (TDD), which consists of a first downlink operating frequency band and a first uplink operating frequency band, and the second frequency band used for Frequency Division Duplex (FDD), which consists of a second downlink operating frequency band and a second uplink operating frequency band, the first downlink operating frequency band and the first uplink operating frequency band are in the same frequency range, and the frequency band positions, starting from the low-frequency side or the high-frequency side, follow the order of the first frequency band, the second uplink operating frequency band, and the second downlink operating frequency band. The frequency range of the first frequency band does not overlap with the frequency range of the second uplink operating frequency band. The elastic wave filter circuit is formed on a first substrate with piezoelectric properties and has a passband that includes the first uplink operating frequency band and the second uplink operating frequency band.

4. The elastic wave filter circuit according to claim 3, wherein, The first frequency band is the B52 band used for LTE. The second frequency band is the B22 band used for LTE.

5. The elastic wave filter circuit according to any one of claims 1 to 4, wherein, With the center frequency of the passband set to f0 (Hz), the frequency gap between the first uplink operating frequency band and the first downlink operating frequency band or the second downlink operating frequency band adjacent to the first uplink operating frequency band set to fgap (Hz), and the maximum temperature change relative to room temperature set to ΔT, the frequency temperature coefficient TCF (ppm / ℃) of the elastic wave filter circuit satisfies the following relationship: TCF≤|[(f0±fgap / 4)-f0] / f0 / ΔT×1000000| (Formula 1).

6. A multiplexer, comprising: Antenna connection terminals; The elastic wave filter circuit according to any one of claims 1, 2, and 5 is connected to the antenna connection terminal; and A first filter circuit, connected to the antenna connection terminal, has a passband that includes the first downlink operating frequency band and the second downlink operating frequency band. in, The first filter circuit is formed on a second substrate, which is different from the first substrate.

7. A multiplexer, comprising: Antenna connection terminals; The elastic wave filter circuit according to any one of claims 1, 2, and 5 is connected to the antenna connection terminal; and A first filter circuit, connected to the antenna connection terminal, has a passband that includes the first downlink operating frequency band and the second downlink operating frequency band. in, The electrodes constituting the elastic wave filter circuit are in contact with the first dielectric layer formed on the first substrate. The electrodes constituting the first filter circuit are in contact with a second dielectric layer formed on the first substrate, which is different from the first dielectric layer.

8. A front-end circuit, comprising: Antenna connection terminals; The elastic wave filter circuit according to any one of claims 1 to 5 is connected to the antenna connection terminal; The second filter circuit is connected to the antenna connection terminal and has a passband that includes a third uplink operating frequency band, the frequency of which does not overlap with the frequencies of the first frequency band and the second frequency band. A power amplifier capable of amplifying high-frequency signals in the first frequency band, the second frequency band, and the third frequency band; A switch that switches the connection between the elastic wave filter circuit and the power amplifier, as well as the connection between the second filter circuit and the power amplifier; as well as An impedance matching circuit, connected between the power amplifier and the switch, is capable of changing the impedance in response to the switching of the switch.

9. A communication device comprising: Signal processing circuits that process high-frequency signals; and The front-end circuit according to claim 8 transmits the high-frequency signal between the signal processing circuit and the antenna.

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