JP2006129131A - Balanced high-frequency filter, common utility antenna, and balanced high-frequency circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a balanced high-frequency filter, and common utility antenna in which the same phase signal component is small in a transmission frequency band, and a balanced high-frequency circuit which makes the same frequency signal component small. <P>SOLUTION: The balanced high frequency filter 101 is configured by a balanced high frequency element 102, and a phase shift circuit 103. The phase shift circuit 103 is configured by a transmission line 104, and arranged between output terminals. The transmission line 104 is a serial resonance circuit which resonates on a predetermined frequency for an in-phase signal component which is established as a length which is nearly λ<SB>T</SB>/2 (λ<SB>T</SB>is a wavelength at a frequency of a transmission frequency band). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a balanced high-frequency filter, an antenna duplexer, and a common-mode signal reduction method in a balanced high-frequency circuit.

  In recent years, with the development of mobile communication, higher performance and smaller size of devices used are expected. Conventionally, a surface acoustic wave filter has been widely used as a filter used in the RF stage. In recent years, a band filter configured by connecting FBARs (Film Bulk Acoustic Resonators) in a ladder shape is expected. With regard to filters and semiconductor elements used in such RF stages, for the purpose of improving noise characteristics against crosstalk between devices, etc., the balance (balancing) has progressed, and good balance characteristics are required. .

  Hereinafter, the improvement of the balance characteristic of the conventional balanced high-frequency device will be described. Regarding the improvement of the balance characteristics of a balanced high-frequency device, a phase shift circuit has been proposed for improving the balance characteristics of a pass band through which a desired wave passes, for example, a receive filter for a receive filter (see, for example, Patent Document 1). . First, a conventional surface acoustic wave filter will be described as an example of a conventional balanced high-frequency device. FIG. 17 is a configuration diagram of a surface acoustic wave filter 1701 having a balanced input / output terminal. In FIG. 17, a surface acoustic wave filter 1701 includes first, second, and third interdigital transducer electrodes (hereinafter referred to as IDT electrodes) 1703, 1704, and 1705 and first and second electrodes on a piezoelectric substrate 1702. It is constituted by reflector electrodes 1706 and 1707. One electrode finger of the first IDT electrode 1703 is connected to the output terminal OUT1, and the other electrode finger of the first IDT electrode 1703 is connected to the output terminal OUT2. One electrode finger of the second and third IDT electrodes 1704 and 1705 is connected to the input terminal IN, and the other is grounded. With the above configuration, a surface acoustic wave filter having an unbalanced-balanced input / output terminal can be realized. In the surface acoustic wave filter of FIG. 17, the impedance of the input / output terminals is designed to be 50Ω. FIG. 18 is a characteristic diagram of the conventional surface acoustic wave filter in the 900 MHz band shown in FIG. In FIG. 18, (a) is the pass characteristic, (b) is the amplitude balance characteristic in the pass band (925 MHz to 960 MHz), and (c) is the phase balance characteristic in the pass band. In FIG. 18, Tx is a transmission frequency band used in the GSM system, and Rx is a reception frequency band used in the GSM system. Here, the pass characteristic is the characteristic of the differential signal component at the balanced terminal, and the pass band is the reception frequency band Rx. As shown in FIG. 18, in the pass band, the amplitude balance characteristic is greatly degraded from −0.67 dB to +0.77 dB, and the phase balance characteristic is significantly degraded from −6.3 ° to + 9.4 °.

  Here, the amplitude balance characteristic represents the amplitude difference between the signal amplitude of the input terminal IN and the output terminal OUT1 and the signal amplitude of the input terminal IN and the output terminal OUT2, and this value cannot be zero. There is no deterioration of the balance characteristics. The phase balance characteristic represents a deviation from 180 ° of the phase difference between the signal phase of the input terminal IN and the output terminal OUT1 and the signal phase of the input terminal IN and the output terminal OUT2. If the value is zero, there is no deterioration of the balance characteristic.

Next, a conventional phase shift circuit will be described with respect to balance characteristics in a conventional balanced high-frequency device. FIG. 19 shows a configuration of a conventional balanced high-frequency device 1901. In FIG. 19, the balanced high-frequency device 1901 includes a balanced high-frequency element 1902 and a phase shift circuit 1903. The phase shift circuit 1903 is constituted by a transmission line 1904 and is arranged between output terminals. Here, the length of the transmission line 1904 is λ _R / 2 (λ _R is the wavelength in the frequency of the reception frequency band). FIG. 20 shows the characteristics of the balanced high-frequency device 1901. In FIG. 20, (a) is the pass characteristic, (b) is the amplitude balance characteristic of the pass band, and (c) is the phase balance characteristic of the pass band. In FIG. 20, Tx is a transmission frequency band used in the GSM system, and Rx is a reception frequency band used in the GSM system. Here, the pass characteristic is the characteristic of the differential signal component at the balanced terminal, and the pass band is the reception frequency band Rx. Compared with the conventional characteristic shown in FIG. 18, the balance characteristic is greatly improved, and the characteristic is almost close to the ideal state.
JP 2003-338724 A

  However, in the conventional technique, the balanced high-frequency device is a phase shift circuit for improving the balance characteristics by focusing on the characteristics in the pass band, and has not been focused on the characteristics outside the pass band. When a balanced high-frequency element as a balanced high-frequency device is connected to the input side of a semiconductor device, characteristics not only in the passband but also outside the passband are important. In particular, when the balanced high-frequency element is a reception filter, not only the reception frequency band but also the characteristics of the transmission frequency band are important.

  FIG. 21 shows the characteristics of the in-phase signal component in the transmission frequency band (880 MHz to 915 MHz) in the surface acoustic wave filter 1701 shown in FIG. Here, the characteristic of the in-phase signal component refers to leakage of the in-phase signal component from the input side to the output side of the balanced high-frequency element. As shown in FIG. 21, the in-phase signal component in the transmission frequency band is about −30 dB, and there is a frequency band larger than the attenuation in the transmission frequency band in FIG. This is the low noise connected to the subsequent stage of the balanced high-frequency element due to the leakage of the in-phase signal component even if the transmission signal in the transmission frequency band is suppressed due to the passing characteristics of the differential signal component of the balanced high-frequency element. This causes saturation and distortion of semiconductor devices such as amplifiers and mixers, and causes deterioration of sensitivity as communication equipment. In particular, in the antenna duplexer, it is necessary to increase the attenuation of the transmission signal and the isolation between transmission and reception, and it is necessary to reduce the leakage of the in-phase signal component in this transmission frequency band. Thus, the conventional balanced high-frequency device has a problem that the common-mode signal component leaking to the balanced terminal on the output side is large.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a balanced high-frequency filter and an antenna duplexer having a small in-phase signal component in a transmission frequency band. It is another object of the present invention to provide such a balanced high-frequency filter, a balanced high-frequency circuit using an antenna duplexer, and a communication device. It is another object of the present invention to provide a balanced high-frequency circuit that reduces the in-phase signal component in the transmission frequency band.

  In order to solve the above-described conventional problems, a balanced high-frequency filter according to the present invention is a balanced high-frequency filter including a balanced high-frequency element having at least one balanced terminal and a phase shift circuit, and the balanced high-frequency filter. The filter has a first frequency band that is a pass band of the balanced high-frequency element and a second frequency band that is an attenuation band of the balanced high-frequency element, and the phase shift circuit is electrically connected between the balanced terminals. Are connected to each other and resonate at a predetermined frequency with respect to the in-phase signal component, and the resonance frequency of the series resonance circuit is set to the second frequency band.

  With this configuration, in-phase signal components in the second frequency band can be reduced.

  In the balanced high-frequency filter, it is preferable that the first frequency band is a reception frequency band and the second frequency band is a transmission frequency band.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  In the balanced high-frequency filter, the phase shift circuit includes a transmission line, and the transmission line has a length that is approximately half of the wavelength in the second frequency band. The phase circuit is preferably connected between the balanced terminals.

  In the balanced high-frequency filter, the phase shift circuit includes at least two transmission lines, and one of the transmission lines has a length approximately half of the wavelength in the second frequency band. Preferably, the other transmission line has a different length from the one transmission line, and the phase shift circuit is connected between the balanced terminals.

  In the balanced high-frequency filter, the phase shift circuit includes at least three impedance elements, and the first impedance element and the second impedance element are connected in series between the balanced terminals. A connection point between the first impedance element and the second impedance element is grounded via a third impedance element, wherein the first impedance element and the third impedance element Preferably, a series resonance circuit is formed by the elements, and a series resonance circuit is formed by the second impedance element and the third impedance element.

  In the balanced high-frequency filter, it is preferable that the first and second impedance elements are capacitors, and the third impedance element is an inductor.

  In the balanced high-frequency filter, it is preferable that the first and second impedance elements are inductors, and the third impedance element is a capacitor.

  In the balanced high-frequency filter, the impedance of the first and second impedance elements in the first frequency band is 3 or more, normalized by one characteristic impedance value of the balanced terminal. It is preferable to set so as to be.

  In the balanced high-frequency filter, the balanced high-frequency element is preferably a surface acoustic wave filter.

  In the balanced high-frequency filter, it is preferable that the balanced high-frequency element is configured by a filter using FBAR.

  In the balanced high-frequency filter, the balanced high-frequency filter is preferably connected to an input side of a low noise amplifier having a balanced terminal.

  In the balanced high-frequency filter, the balanced high-frequency filter is preferably connected to an input side of a mixer having a balanced terminal.

  Moreover, in order to solve the said conventional subject, the antenna sharing device of this invention is equipped with the balanced high frequency filter of Claim 1 or 2.

  In the antenna duplexer, the balanced high-frequency filter is a reception filter in the antenna duplexer, and the first frequency band is a reception frequency band in the antenna duplexer, and the second frequency band. Is preferably a transmission frequency band in the antenna duplexer.

  In the antenna duplexer, the antenna duplexer is preferably connected to an input side of a low noise amplifier having a balanced terminal.

  In order to solve the conventional problems, a balanced high-frequency circuit according to the present invention includes a low-noise amplifier having a balanced terminal, a mixer having a balanced terminal, and a phase shift circuit. In the balanced high-frequency circuit, the first frequency band is a frequency band of a desired wave, the second frequency band is a frequency band of an interference wave, and the phase shift circuit includes the low-noise amplifier and the The phase shift circuit is arranged between balanced lines connecting a mixer, and the phase shift circuit is electrically connected between the balanced terminals and resonates at a predetermined frequency with respect to the in-phase signal component. It is a resonance circuit, Comprising: The resonance frequency of the said series resonance circuit is set to the 2nd frequency band.

  With this configuration, in-phase signal components in the second frequency band can be reduced.

  In the balanced high-frequency circuit, it is preferable that the first frequency band is a reception frequency band and the second frequency band is a transmission frequency band.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  In the balanced high-frequency circuit, it is preferable that the first frequency band is a reception frequency band and the second frequency band is a transmission frequency band.

  In the balanced high-frequency circuit, the phase shift circuit includes a transmission line, and the transmission line has a length that is approximately half of the wavelength in the second frequency band. The phase circuit is preferably connected between the balanced terminals.

  In the balanced high-frequency circuit, the phase shift circuit includes at least three impedance elements, and the first impedance element and the second impedance element are connected in series between the balanced terminals. A connection point between the first impedance element and the second impedance element is grounded via a third impedance element, wherein the first impedance element and the third impedance element Preferably, a series resonance circuit is formed by the elements, and a series resonance circuit is formed by the second impedance element and the third impedance element.

  In the balanced high-frequency circuit, it is preferable that the first and second impedance elements are capacitors and the third impedance element is an inductor.

  In the balanced high-frequency circuit, it is preferable that the first and second impedance elements are inductors, and the third impedance element is a capacitor.

  In the balanced high-frequency circuit, the impedance in the first frequency band of the first and second impedance elements is a value normalized by one characteristic impedance value at the balanced terminal of 3 or more. It is preferable to set so as to be.

  In order to solve the conventional problems, a balanced high-frequency circuit according to the present invention is a balanced high-frequency circuit including a circuit board having a balanced line and a phase shift circuit. The first frequency band is a frequency band of a desired wave, the second frequency band is a frequency band of an interference wave, and the phase shift circuit is mounted on the circuit board, and the phase shift circuit The circuit is a series resonance circuit that is electrically connected between the balanced lines and resonates at a predetermined frequency with respect to the in-phase signal component, and the resonance frequency of the series resonance circuit is set to a second frequency band. Has been.

  With this configuration, in-phase signal components in the second frequency band can be reduced.

  In the balanced high-frequency circuit, it is preferable that the first frequency band is a reception frequency band and the second frequency band is a transmission frequency band.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  Further, in the balanced high-frequency circuit, the phase shift circuit includes a transmission line, and the transmission line has a length approximately half of the wavelength in the first frequency band, and The phase circuit is preferably connected between the balanced terminals.

  In the balanced high-frequency circuit, the phase shift circuit includes at least three impedance elements, and the first impedance element and the second impedance element are connected in series between the balanced terminals. A connection point between the first impedance element and the second impedance element is grounded via a third impedance element, wherein the first impedance element and the third impedance element Preferably, a series resonance circuit is formed by the elements, and a series resonance circuit is formed by the second impedance element and the third impedance element.

  In the balanced high-frequency circuit, it is preferable that the first and second impedance elements are capacitors and the third impedance element is an inductor.

  In the balanced high-frequency circuit, it is preferable that the first and second impedance elements are inductors, and the third impedance element is a capacitor.

  In the balanced high-frequency circuit, the impedance in the first frequency band of the first and second impedance elements is a value normalized by one characteristic impedance value at the balanced terminal of 3 or more. It is preferable to set so as to be.

  Moreover, in order to solve the said conventional subject, the communication apparatus of this invention uses the balanced high frequency filter of Claim 1 or 2.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  Moreover, in order to solve the said conventional subject, the communication apparatus of this invention uses the antenna sharing device of Claim 13 or 14.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  In order to solve the conventional problem, the communication device of the present invention uses the balanced high-frequency circuit according to claim 16 or 17.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  In order to solve the conventional problem, the communication device of the present invention uses the balanced high-frequency circuit according to claim 23 or 24.

  With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low-noise amplifier and mixer connected in the subsequent stage can be improved, and a highly sensitive communication device is provided. can do.

  According to the balanced high-frequency filter and antenna duplexer of the present invention, a balanced high-frequency filter and antenna duplexer having a small in-phase signal component in the transmission frequency band can be realized. In addition, a balanced high-frequency circuit and a communication device using such a balanced high-frequency filter and an antenna duplexer can be provided. In addition, it is possible to provide a balanced high-frequency circuit that reduces the in-phase signal component in the transmission frequency band.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a balanced high-frequency filter according to Embodiment 1 of the present invention. In FIG. 1, the balanced high-frequency filter 101 includes a balanced high-frequency element 102 and a phase shift circuit 103. The phase shift circuit 103 is constituted by a transmission line 104 and is arranged between output terminals. Here, the length of the transmission line 104 is λ _T / 2 (λ _T is the wavelength in the frequency of the transmission frequency band). Here, the transmission frequency band is a transmission frequency band (880 to 915 MHz) used in the GSM system.

FIG. 2A shows the characteristics of the in-phase signal component in the transmission frequency band. Here, lambda _T has a length corresponding to 904MHz. As the balanced high-frequency element, a surface acoustic wave filter having the characteristics shown in FIG. 18 is used. 2A, the characteristics of the in-phase signal component are greatly reduced as compared with the conventional characteristics shown in FIG. FIG. 2B shows the characteristics of the in-phase signal component in the transmission frequency band in the configuration of FIG. In FIG. 2 (b), the length of the transmission line is lambda _R, and a length corresponding to a frequency within the reception frequency band 942.5MHz. In FIG. 2, by setting the length of the transmission line to λ _T / 2, the characteristics of the in-phase signal component are improved as compared with the conventional case.

  FIG. 3 shows the characteristics of the balanced high-frequency device 101. In FIG. 3, (a) is the pass characteristic, (b) is the amplitude balance characteristic of the pass band, and (c) is the phase balance characteristic of the pass band. In FIG. 3, Tx is a transmission frequency band used in the GSM system, and Rx is a reception frequency band used in the GSM system. Here, the pass characteristic is a characteristic of the differential signal component at the balanced terminal, and the pass band is the reception frequency band Rx. In FIG. 3, the balance characteristic is greatly improved as compared with the conventional characteristic shown in FIG. Further, substantially the same characteristics are obtained as compared with the conventional characteristics shown in FIG.

With the above-described configuration, the balanced high-frequency filter of the present invention has a transmission characteristic in the reception frequency band by setting the transmission line as the phase shift circuit to λ _T / 2 and the frequency within the transmission frequency band. In addition, the in-phase signal component in the transmission frequency band can be reduced without degrading the balance characteristic, and a balanced high-frequency filter having excellent characteristics inside and outside the pass band can be realized.

  In the present embodiment, the surface acoustic wave filter has been described as an example of the balanced high-frequency element constituting the balanced high-frequency filter. However, the configuration is not limited thereto. In the present invention, the in-phase signal component in the transmission frequency band output from the balanced high-frequency element is reduced by a phase shift circuit, and the balanced high-frequency element has a balanced terminal, Similar effects can be obtained.

  The balanced high-frequency element may be a filter using FBAR, for example. FIG. 4 shows a configuration diagram of the FBAR. In FIG. 4, the FBAR 401 includes a lower electrode 403, a piezoelectric thin film 404, and an upper electrode 405 formed on a substrate 402. A cavity 406 is provided in the substrate 402 below the lower electrode, thereby realizing an energy confinement type resonator. Here, the lower electrode 403 and the upper electrode 405 correspond to input / output electrodes of a single FBAR. For the substrate 402, Si, sapphire, or the like is used. For the lower electrode 403 and the upper electrode 405, Al, Mo, Au, Cu, Ti, or the like is used. For the piezoelectric thin film 404, AlN, ZnO, or the like is used. FBAR is comprised by setting it as the above structures. By applying the ladder type filter or the mode coupling type filter by FBAR to the balanced type high frequency device of the present invention, the same effect as the present invention can be obtained as a balanced type high frequency filter. Further, the configuration of the FBAR is not limited to this, and for example, a configuration using an acoustic mirror may be used.

In the present embodiment, a single transmission line as a phase shift circuit has been described. However, a plurality of transmission lines may be combined. FIG. 5 shows another configuration diagram of the balanced high-frequency filter according to Embodiment 1 of the present invention. In FIG. 5, the balanced high frequency filter 501 includes a balanced high frequency element 502 and a phase shift circuit 503. The phase shift circuit 503 includes transmission lines 504 and 505 and is arranged between the output terminals. The length of the transmission line 504 is λ _T / 2 (where λ _T is the wavelength at the frequency of the transmission frequency band). Further, the length of the transmission line 504 is λ / 2, and by setting λ to a length corresponding to a frequency different from the transmission frequency band, the characteristics of the in-phase signal component at other frequencies can be improved. For example, if λ is a frequency in the reception frequency band that is a pass band, the pass characteristics can be further improved. Further, if λ is a transmission frequency band of another system, it is possible to reduce the interference wave of the in-phase signal component from the other system due to crosstalk or the like. Thus, the in-phase signal components of a plurality of systems can be reduced by setting the number of λ and the frequency setting.

  The balanced high-frequency filter of the present invention is used by being connected to a low noise amplifier, a mixer, or the like. FIG. 6A is a diagram illustrating a configuration of the balanced high-frequency filter 101 and the low noise amplifier 601. The phase shift circuit 103 is connected between balanced terminals that connect the balanced high-frequency filter 101 and the low-noise amplifier 601. With the above configuration, in-phase signal components in the transmission frequency band can be reduced, saturation and distortion of the low noise amplifier can be reduced, and a more sensitive communication device can be realized. FIG. 6B is a diagram showing the configuration of the balanced high-frequency filter 101, the low noise amplifier 601, and the mixer 602. The phase shift circuit 103 is connected between balanced terminals that connect the low noise amplifier 601 and the mixer 602. With the above configuration, in-phase signal components in the transmission frequency band can be reduced, mixer distortion can be reduced, and a more sensitive communication device can be realized.

  Further, the first frequency band of the present invention corresponds to the reception frequency band in the present embodiment, and the second frequency band of the present invention corresponds to the transmission frequency band in the present embodiment. In the present embodiment, the first frequency band is a pass band, and the second frequency band is an attenuation band.

(Embodiment 2)
Hereinafter, the configuration of the balanced high-frequency filter of the present invention will be described with reference to the drawings.

  FIG. 7 is a configuration diagram of the balanced high-frequency filter 701 according to the second embodiment of the present invention. In FIG. 7, the balanced high frequency filter 701 includes a balanced high frequency element 702 and a phase shift circuit 703. In the balanced high-frequency element 702, the input-side terminal is an input terminal IN which is an unbalanced input / output terminal, and the output-side terminals are output terminals OUT1 and OUT2 which are balanced terminals.

  The phase shift circuit 703 includes capacitors 704 and 705 as impedance elements and an inductor 706. The capacitors 704 and 705 are connected in series between the output terminals, and the connection point 707 of the capacitors 704 and 705 is grounded via the inductor 706. As described above, the phase shift circuit 703 is connected between the output terminals.

In the phase shift circuit of FIG. 7, regarding the differential signal component that is the pass characteristic of the balanced high-frequency filter, the connection point 707 between the capacitors 704 and 705 serves as a virtual ground point, so the values of the capacitors 702 and 703 are sufficiently reduced. As a result, the impedance to the ground plane can be increased, and the differential signal component is transmitted to the output terminals OUT1 and OUT2 without being grounded. Regarding the in-phase signal component, the connection point 707 between the capacitors 704 and 705 is not a virtual ground point, and the capacitor 704 and a part of the inductor 706, and the capacitor 705 and a part of the inductor 706 are in series resonance at a predetermined frequency. A circuit is formed. In the phase shift circuit 703, assuming that the capacitance of the capacitor is C and the inductance of the inductor is L / 2, the resonance frequency of the series resonance circuit related to the in-phase signal component is f _T = 1 / (2π × (LC) ^1/2 ). In-phase signal components in this frequency band are short-circuited to the ground plane.

FIG. 8A shows the characteristics of the in-phase signal component in the transmission frequency band. Here, as the resonance frequency f _T of the series resonant circuit as the transmission frequency band, Oil set with 904MHz. As the balanced high-frequency element, a surface acoustic wave filter having the characteristics shown in FIG. 18 is used. 8A, the characteristics of the in-phase signal component are greatly reduced as compared with the conventional characteristics shown in FIG. FIG. 8B shows the characteristics of the in-phase signal component in the transmission frequency band when it is set to 951 MHz so that the resonance frequency of the series resonance circuit is in the reception frequency band. Thus, by setting the resonance frequency of the series resonance circuit within the transmission frequency band, the characteristics of the in-phase signal component are improved as compared with the conventional case.

  FIG. 9 shows the characteristics of the balanced high frequency filter 701. In FIG. 9, (a) is a pass characteristic, (b) is an amplitude balance characteristic of the pass band, and (c) is a phase balance characteristic of the pass band. In FIG. 9, Tx is a transmission frequency band used in the GSM system, and Rx is a reception frequency band used in the GSM system. Here, the pass characteristic is a characteristic of the differential signal component at the balanced terminal, and the pass band is the reception frequency band Rx. In FIG. 9, the balance characteristic is improved as compared with the conventional characteristic shown in FIG.

  With the above configuration, in the balanced high-frequency filter of the present invention, the phase shift circuit is configured by three impedance elements, and the frequency of the series resonance circuit formed for the in-phase signal component is within the transmission frequency band. By setting, the in-phase signal component in the transmission frequency band can be reduced, and a balanced high-frequency filter having excellent characteristics inside and outside the pass band can be realized.

  Note that the phase shift circuit in this embodiment may have a circuit configuration as shown in FIG. In FIG. 10, the phase shift circuit 1001 includes inductors 1002 and 1003 as impedance elements and a capacitor 1004. The inductors 1002 and 1003 are connected in series between the output terminals, and the connection point 1005 of the inductors 1002 and 1003 is grounded via the capacitor 1004. Thus, the phase shift circuit 1001 is connected between the output terminals.

In the phase shift circuit of FIG. 10, regarding the differential signal component that is the pass characteristic of the balanced high-frequency filter, the connection point 1005 between the inductors 1002 and 1003 is a virtual ground point, so the values of the inductors 1002 and 1003 are sufficiently increased. As a result, the impedance to the ground plane can be increased, and the differential signal component is transmitted to the output terminals OUT1 and OUT2 without being grounded. Regarding the in-phase signal component, the connection point 1005 between the inductors 1002 and 1003 is not a virtual ground point, and the inductor 1002 and part of the capacitor 1004 and the inductor 1002 and part of the capacitor 1004 are in series resonance at a predetermined frequency. A circuit is formed. In the phase shift circuit 1001, when the inductance of the inductor is L and the capacitance of the capacitor is 2 × C, the resonance frequency of the series resonance circuit related to the in-phase signal component is f _T = 1 / (2π × (LC) ^1/2 ). Thus, the in-phase signal component in this frequency band is short-circuited to the ground plane.

  In the phase shift circuit 703, when the capacitance of the capacitor is large, the impedance related to the differential signal component is reduced, and the differential signal component is short-circuited, causing a loss of the filter. The pass characteristics of the filter were evaluated when the impedance of the capacitors 704 and 705 was changed. FIG. 11A shows a loss value with respect to the normalized impedance obtained by dividing the impedance of the capacitors 702 and 703 in the reception frequency band by the characteristic impedance of the terminal. Here, since the characteristic impedance of the balanced output terminal is 50Ω, the characteristic impedance of each terminal is 25Ω. As shown in FIG. 11A, the loss is degraded in the range where the normalized impedance is smaller than 3. The characteristics shown in FIGS. 8 and 9 are characteristics when the normalized impedance is 6.8.

  Further, in the phase shift circuit 1001, when the inductance of the inductor is small, the impedance related to the differential signal component becomes small, and the differential signal component is short-circuited, causing a loss of the filter. The filter pass characteristics were evaluated when the impedances of the inductors 1002 and 1003 were changed. FIG. 11B shows a loss value with respect to the normalized impedance obtained by dividing the impedance of the inductors 1002 and 1003 in the reception frequency band by the characteristic impedance of the terminal. Here, since the characteristic impedance of the balanced output terminal is 50Ω, the characteristic impedance of each terminal is 25Ω. As shown in FIG. 11B, the loss is degraded in the range where the normalized impedance is smaller than 3.

  From the above, the normalized impedance in the passband is preferably 3 or more.

  In the present embodiment, the surface acoustic wave filter has been described as an example of the balanced high-frequency element constituting the balanced high-frequency filter. However, the present invention is not limited to this. In the present invention, the in-phase signal component in the transmission frequency band output from the balanced high-frequency element is reduced by a phase shift circuit, and the balanced high-frequency element has a balanced terminal, Similar effects can be obtained. As the balanced high-frequency element, for example, a filter using FBAR may be used.

  In addition, the phase shift circuit in the present embodiment may include a matching circuit for differential signal components.

  Further, the phase shift circuit in the present embodiment may be applied to the configuration as shown in FIG. Even in this case, the effect of reducing the in-phase signal component and improving the characteristics of the low noise amplifier and the mixer is the same, and a more sensitive communication device can be realized.

  Further, the first frequency band of the present invention corresponds to the reception frequency band in the present embodiment, and the second frequency band of the present invention corresponds to the transmission frequency band in the present embodiment. In the present embodiment, the first frequency band is a pass band, and the second frequency band is an attenuation band.

(Embodiment 3)
Hereinafter, the configuration of the antenna duplexer of the present invention will be described with reference to the drawings.

FIG. 12 is a configuration diagram of an antenna duplexer according to Embodiment 3 of the present invention. In FIG. 12, the antenna duplexer 1201 includes a transmission filter 1202, a reception filter 1203, and a phase shift circuit 1204. The output side of the reception filter 1203 is a balanced terminal, and a phase shift circuit 1204 is connected between the balanced terminals. The phase shift circuit 1204 has the same configuration as that of FIG. 1, is configured by the transmission line 104, and is disposed between the output terminals. The length of the transmission line 104 is λ _T / 2 (where λ _T is the wavelength at the frequency of the transmission frequency band).

  With the above configuration, the antenna duplexer of the present invention can reduce the leakage of the in-phase signal component in the transmission frequency band from the reception filter 1203.

  In addition, in this Embodiment, although the transmission line as a phase shift circuit was demonstrated as one, this may combine a some transmission line.

  As for the phase shift circuit 1204, as shown in FIG. 13, a phase shift circuit 703 having the same configuration as that of FIG. 7 may be used. Even in this case, leakage of the in-phase signal component in the transmission frequency band from the reception filter 1203 can be reduced by setting the resonance frequency of the series resonance circuit formed by the phase shift circuit 703 within the transmission frequency band. Further, the phase shift circuit 1204 may use the phase shift circuit 1001 shown in FIG. Further, when the impedance element is used in this way, it is preferable that the normalized impedance to the virtual ground plane for the differential signal component is 3 or more.

  In the present embodiment, the configurations of the transmission filter 1202 and the reception filter 1203 are not particularly limited. These may use a surface acoustic wave filter or may use FBAR.

  In addition, the phase shift circuit in the present embodiment may include a matching circuit for differential signal components.

  Further, the first frequency band of the present invention corresponds to the reception frequency band in the present embodiment, and the second frequency band of the present invention corresponds to the transmission frequency band in the present embodiment. In the present embodiment, the first frequency band is a desired wave frequency band, and the second frequency band is an interference wave frequency band.

  Further, if the antenna duplexer of the present invention is connected to a low noise amplifier, saturation and distortion due to in-phase signal components in the transmission frequency band of the low noise amplifier can be suppressed, and a more sensitive communication device can be realized.

(Embodiment 4)
Hereinafter, the configuration of the balanced high-frequency circuit of the present invention will be described with reference to the drawings.

FIG. 14 is a configuration diagram of a balanced high-frequency circuit according to Embodiment 4 of the present invention. In FIG. 14A, the balanced high-frequency circuit 1401 includes a low noise amplifier 1402, a mixer 1403, and a phase shift circuit 1404. The output side of the low noise amplifier 1402 is a balanced terminal, the input side of the mixer 1403 connected to the low noise amplifier 1402 is a balanced terminal, and a phase shift circuit 1404 is connected between the balanced terminals. The phase shift circuit 1404 is similar to the configuration in FIG. 1, is configured by the transmission line 104, and is disposed between the output terminals. The length of the transmission line 104 is λ _T / 2 (where λ _T is the wavelength at the frequency of the transmission frequency band).

  With the above configuration, the balanced high-frequency circuit of the present invention can reduce the leakage of the in-phase signal component in the transmission frequency band from the low noise amplifier 1402, and the saturation by the in-phase signal component in the transmission frequency band of the mixer 1403. Communication device with higher sensitivity can be realized.

  In addition, in this Embodiment, although the transmission line as a phase shift circuit was demonstrated as one, this may combine a some transmission line.

  Further, regarding the phase shift circuit 1402, as shown in FIG. 14B, a phase shift circuit 703 having the same configuration as that of FIG. 7 may be used. Even in this case, leakage of the in-phase signal component in the transmission frequency band from the low noise amplifier 1402 can be reduced by setting the resonance frequency of the series resonance circuit formed by the phase shift circuit 703 within the transmission frequency band. Further, the phase shift circuit 1402 may use the phase shift circuit 1001 shown in FIG. Further, when the impedance element is used in this way, it is preferable that the normalized impedance to the virtual ground plane for the differential signal component is 3 or more.

  In addition, the phase shift circuit in the present embodiment may include a low noise amplifier and a mixer matching circuit for differential signal components.

  Further, the first frequency band of the present invention corresponds to the reception frequency band in the present embodiment, and the second frequency band of the present invention corresponds to the transmission frequency band in the present embodiment. In the present embodiment, the first frequency band is a desired wave frequency band, and the second frequency band is an interference wave frequency band.

(Embodiment 5)
Hereinafter, the configuration of the balanced high-frequency circuit of the present invention will be described with reference to the drawings.

FIG. 15 is a configuration diagram of a balanced high-frequency circuit according to the fifth embodiment of the present invention. In FIG. 15, the balanced high-frequency circuit 1501 includes a transmission amplifier 1503, a transmission filter 1504, a switch 1505, a reception filter 1506, a low noise amplifier 1507, a mixer 1508, and a phase shift circuit 1509 mounted on a circuit board 1502. Is done. A transmission signal output from the transmission circuit is output to the antenna terminal ANT via the transmission amplifier 1502, the transmission filter 1503, and the switch 1504. Such a balanced high-frequency circuit 1501 is mainly used for communication equipment of a time division transmission / reception system. A reception signal input from the antenna terminal ANT is input to the reception circuit via the switch 1504, the reception filter 1506, the reception amplifier 1507, and the mixer 1508. Here, since the reception amplifier 1507 is a balanced type and the switch 1504 is an unbalanced type, the reception filter 1506 has an unbalanced-balanced type input / output terminal. The phase shift circuit 1509 is similar to the configuration in FIG. 1, is configured by the transmission line 104, and is disposed between the output terminals. The length of the transmission line 104 is λ _T / 2 (where λ _T is the wavelength at the frequency of the transmission frequency band).

  With the above configuration, the balanced high-frequency circuit of the present invention can reduce the leakage of the in-phase signal component in the transmission frequency band from the low-noise amplifier 1402, and the in-phase signal component in the transmission frequency band of the low-noise amplifier 1507. Saturation due to can be suppressed.

  In addition, in this Embodiment, although the transmission line as a phase shift circuit was demonstrated as one, this may combine a some transmission line.

  Further, regarding the phase shift circuit 1509, a phase shift circuit 703 having the same configuration as in FIG. 7 may be used. Even in this case, leakage of the in-phase signal component in the transmission frequency band from the low noise amplifier 1502 can be reduced by setting the resonance frequency of the series resonance circuit formed by the phase shift circuit 703 within the transmission frequency band. Further, the phase shift circuit 1509 may use the phase shift circuit 1001 shown in FIG. Further, when the impedance element is used in this way, it is preferable that the normalized impedance to the virtual ground plane for the differential signal component is 3 or more.

  In this embodiment, the phase shift circuit is arranged on the input side of the low noise amplifier 1506. However, it may be arranged between the low noise amplifier 1506 and the mixer 1507. Thereby, the leakage of the in-phase signal component in the transmission frequency band can be further reduced, and the saturation of the mixer can be suppressed.

  In addition, the phase shift circuit in the present embodiment may include a matching circuit for differential signal components.

  Further, the balanced high-frequency circuit 1501 has been described using the switch 1505 as means for switching between transmission and reception, but this is a balanced high-frequency circuit 1601 using an antenna duplexer 1602 as shown in FIG. It doesn't matter. Here, the antenna duplexer 1602 is composed of a transmission filter 1603 and a reception filter 1604. Such a balanced high-frequency circuit 1601 is mainly used for communication equipment in a simultaneous transmission / reception system.

  Further, in the balanced high-frequency circuit of this embodiment, the phase shift circuit of the present invention is formed on a circuit board. This includes a reception filter 1506, a low noise amplifier 1507, a mixer 1508, and an antenna duplexer 1602. It may be built in.

  In this embodiment, the configurations of the transmission filter 1504 and the reception filter 1506 and the configurations of the transmission filter 1603 and the reception filter 1604 that configure the antenna duplexer 1602 are not particularly limited. These may use a surface acoustic wave filter or may use FBAR.

  In addition, the phase shift circuit in the present embodiment may include a matching circuit for differential signal components.

  Further, the first frequency band of the present invention corresponds to the reception frequency band in the present embodiment, and the second frequency band of the present invention corresponds to the transmission frequency band in the present embodiment. In the present embodiment, the first frequency band is a desired wave frequency band, and the second frequency band is an interference wave frequency band.

  Further, in this embodiment, by applying the balanced high-frequency circuit of the present invention to a communication device, it is possible to suppress a transmission jamming wave due to an in-phase signal component and to realize a communication device with higher sensitivity.

In the present embodiment, the length of the transmission line as the phase shift circuit is λ _T / 2 (where λ _T is the wavelength in the frequency of the transmission frequency band), but the resonance frequency is within the transmission frequency band. It is sufficient if it can be set, and a slight deviation is acceptable.

  The balanced high-frequency filter, antenna duplexer, and balanced high-frequency circuit according to the present invention are useful as a high-frequency device that can reduce in-phase signal components. It can also be applied to applications such as high-frequency modules and communication equipment.

Configuration diagram of balanced high-frequency filter according to Embodiment 1 of the present invention (A) In-phase signal component characteristic diagram of balanced high-frequency filter according to Embodiment 1 of the present invention (b) In-phase signal component characteristic diagram of conventional balanced high-frequency device (A) Passing characteristic diagram of balanced high-frequency filter according to Embodiment 1 of the present invention (b) Amplitude balance characteristic diagram of balanced high-frequency filter according to Embodiment 1 of the present invention (c) According to Embodiment 1 of the present invention Phase balance characteristic diagram of balanced high-frequency filter Configuration diagram of FBAR in Embodiment 1 of the present invention Another block diagram of the balanced high-frequency filter according to Embodiment 1 of the present invention (A) The figure which shows the structure of the connection of the balanced type high frequency filter in Embodiment 1 of this invention (b) The figure which shows the structure of the other connection of the balanced type high frequency filter in Embodiment 1 of this invention Configuration diagram of balanced high-frequency filter according to Embodiment 2 of the present invention (A) In-phase signal component characteristic diagram of balanced high-frequency filter according to Embodiment 2 of the present invention (b) In-phase signal component characteristic diagram of conventional balanced high-frequency device (A) Passage characteristic diagram of balanced high-frequency filter according to Embodiment 2 of the present invention (b) Amplitude balance characteristic diagram of balanced high-frequency filter according to Embodiment 2 of the present invention (c) According to Embodiment 2 of the present invention Phase balance characteristic diagram of balanced high-frequency filter Another block diagram of the phase shift circuit in Embodiment 2 of this invention (A) Relationship between loss and standardized impedance when using the phase shift circuit shown in FIG. 7 (b) Relationship between loss and standardized impedance when using the phase shift circuit shown in FIG. Configuration diagram of antenna duplexer in Embodiment 3 of the present invention Another block diagram of antenna duplexer in Embodiment 3 of the present invention (A) Configuration diagram of balanced high-frequency circuit according to Embodiment 4 of the present invention (b) Other configuration diagram of balanced high-frequency circuit according to Embodiment 4 of the present invention Configuration diagram of balanced high-frequency circuit according to Embodiment 5 of the present invention Another configuration diagram of the balanced high-frequency circuit in the fifth embodiment of the present invention Configuration of conventional surface acoustic wave filter (A) Passing characteristic diagram of conventional surface acoustic wave filter (b) Amplitude balance characteristic diagram of conventional surface acoustic wave filter (c) Phase balance characteristic diagram of conventional surface acoustic wave filter Configuration diagram of a conventional balanced high-frequency device (A) Passing characteristic diagram of conventional balanced high frequency device (b) Amplitude balance characteristic diagram of conventional balanced high frequency device (c) Phase balance characteristic diagram of conventional balanced high frequency device Characteristics of common-mode signal components of conventional balanced high-frequency devices

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Balance type high frequency filter 102 Balance type high frequency element 103 Phase shift circuit 104 Transmission line 401 FBAR
402 Substrate 403 Lower electrode 404 Piezoelectric thin film 405 Upper electrode 406 Cavity 501 Balanced high frequency filter 502 Balanced high frequency element 503 Phase shift circuit 504 Transmission line 505 Transmission line 601 Low amplifier noise 602 Mixer 701 Balanced high frequency filter 702 Balanced high frequency element 703 Phase shift circuit 704, 705 Capacitor 706 Inductor 707 Connection point 1001 Phase shift circuit 1002, 903 Inductor 1004 Capacitor 1005 Connection point 1201 Antenna duplexer 1202 Transmission filter 1203 Reception filter 1204 Phase shift circuit 1401 Balanced high frequency circuit 1402 Low noise amplifier 1403 Mixer 1404 Phase shift circuit 1501 Balanced high frequency circuit 1502 Circuit board 1503 Transmission amplifier 1504 Transmission filter 1505 Switch H 1506 reception filter 1507 low noise amplifier 1508 mixer 1509 phase shift circuit 1601 balanced high frequency circuit 1602 antenna duplexer 1603 transmission filter 1604 reception filter 1701 surface acoustic wave filter 1702 piezoelectric substrate 1703 first IDT electrode 1704 second IDT electrode 1705 Third IDT electrode 1706, 1707 Reflector electrode 101 Balanced high frequency device 102 Balanced high frequency element 103 Phase shift circuit 104 Transmission line

Claims (33)

A balanced high-frequency filter comprising a balanced high-frequency element having at least one balanced terminal and a phase shift circuit,
The balanced high-frequency filter has a first frequency band that is a pass band of the balanced high-frequency element and a second frequency band that is an attenuation band of the balanced high-frequency element;
The phase shift circuit is a series resonance circuit that is electrically connected between the balanced terminals and resonates at a predetermined frequency with respect to the in-phase signal component,
A balanced high-frequency filter, wherein a resonance frequency of the series resonance circuit is set to a second frequency band. The balanced high frequency filter according to claim 1, wherein the first frequency band is a reception frequency band, and the second frequency band is a transmission frequency band. The phase shift circuit includes a transmission line,
3. The transmission line according to claim 1, wherein the transmission line has a length approximately half of a wavelength in the second frequency band, and the phase shift circuit is connected between the balanced terminals. Balanced high-frequency filter. The phase shift circuit includes at least two transmission lines,
One of the transmission lines is approximately half the wavelength in the second frequency band,
The other of the transmission lines is different in length from the one transmission line,
The balanced high-frequency filter according to claim 3, wherein the phase shift circuit is connected between the balanced terminals. The phase shift circuit includes at least three impedance elements,
The first impedance element and the second impedance element are connected in series between the balanced terminals,
A connection point between the first impedance element and the second impedance element is configured to be grounded via a third impedance element,
A series resonant circuit is formed by the first impedance element and the third impedance element,
The balanced high-frequency filter according to claim 1 or 2, wherein a series resonant circuit is formed by the second impedance element and the third impedance element. The first and second impedance elements are capacitors,
The balanced high-frequency filter according to claim 5, wherein the third impedance element is an inductor. The first and second impedance elements are inductors,
The balanced high-frequency filter according to claim 5, wherein the third impedance element is a capacitor. The impedance in the first frequency band of the first and second impedance elements is set so that a value normalized by one characteristic impedance value in the balanced terminal is 3 or more. The balanced high-frequency filter according to claim 6 or 7. The balanced high-frequency filter according to claim 1 or 2, wherein the balanced high-frequency element is formed of a surface acoustic wave filter. The balanced high-frequency filter according to claim 1, wherein the balanced high-frequency element is configured by a filter using FBAR. The balanced high-frequency filter according to claim 1, wherein the balanced high-frequency filter is connected to an input side of a low-noise amplifier having a balanced terminal. The balanced high-frequency filter according to claim 1, wherein the balanced high-frequency filter is connected to an input side of a mixer having a balanced terminal. An antenna duplexer comprising the balanced high-frequency filter according to claim 1. The balanced high-frequency filter is a reception filter in the antenna duplexer,
The first frequency band is a reception frequency band in the antenna duplexer;
The antenna duplexer according to claim 13, wherein the second frequency band is a transmission frequency band in the antenna duplexer. The antenna duplexer according to claim 14, wherein the antenna duplexer is connected to an input side of a low noise amplifier having a balanced terminal. A balanced high-frequency circuit comprising a low noise amplifier having a balanced terminal, a mixer having a balanced terminal, and a phase shift circuit,
In the balanced high-frequency circuit, the first frequency band is a frequency band of a desired wave, and the second frequency band is a frequency band of an interference wave,
The phase shift circuit is a series resonance circuit that is electrically connected between the balanced terminals connecting the low noise amplifier and the mixer, and resonates at a predetermined frequency with respect to an in-phase signal component,
A balanced high-frequency circuit, wherein a resonance frequency of the series resonance circuit is set to a second frequency band. The balanced high-frequency circuit according to claim 16, wherein the first frequency band is a reception frequency band, and the second frequency band is a transmission frequency band. The phase shift circuit includes a transmission line,
18. The transmission line according to claim 16, wherein the transmission line has a length approximately half of a wavelength in the second frequency band, and the phase shift circuit is connected between the balanced terminals. Balanced high-frequency circuit. The phase shift circuit includes at least three impedance elements,
The first impedance element and the second impedance element are connected in series between the balanced terminals,
A connection point between the first impedance element and the second impedance element is configured to be grounded via a third impedance element,
A series resonant circuit is formed by the first impedance element and the third impedance element,
The balanced high-frequency circuit according to claim 16 or 17, wherein a series resonant circuit is formed by the second impedance element and the third impedance element. The first and second impedance elements are capacitors,
The balanced high-frequency circuit according to claim 19, wherein the third impedance element is an inductor. The first and second impedance elements are inductors,
The balanced high-frequency circuit according to claim 19, wherein the third impedance element is a capacitor. The impedance in the first frequency band of the first and second impedance elements is set so that a value normalized by one characteristic impedance value in the balanced terminal is 3 or more. The balanced high-frequency circuit according to claim 20 or 21. A balanced high-frequency circuit including a circuit board having a balanced line and a phase shift circuit,
In the balanced high-frequency circuit, the first frequency band is a frequency band of a desired wave, and the second frequency band is a frequency band of an interference wave,
The phase shift circuit is configured to be mounted on the circuit board,
The phase shift circuit is a series resonant circuit that is electrically connected between the balanced lines and resonates at a predetermined frequency with respect to the in-phase signal component,
A balanced high-frequency circuit, wherein a resonance frequency of the series resonance circuit is set to a second frequency band. The balanced high-frequency circuit according to claim 23, wherein the first frequency band is a reception frequency band, and the second frequency band is a transmission frequency band. The phase shift circuit includes a transmission line,
25. The transmission line according to claim 23 or 24, wherein the transmission line has a length of approximately ½ of a wavelength in the first frequency band, and the phase shift circuit is connected between the balanced terminals. Balanced high-frequency circuit. The phase shift circuit includes at least three impedance elements,
The first impedance element and the second impedance element are connected in series between the balanced terminals,
A connection point between the first impedance element and the second impedance element is configured to be grounded via a third impedance element,
A series resonant circuit is formed by the first impedance element and the third impedance element,
The balanced high-frequency circuit according to claim 23 or 24, wherein a series resonant circuit is formed by the second impedance element and the third impedance element. The first and second impedance elements are capacitors,
27. The balanced high-frequency circuit according to claim 26, wherein the third impedance element is an inductor. The first and second impedance elements are inductors,
27. The balanced high-frequency circuit according to claim 26, wherein the third impedance element is a capacitor. The impedance in the first frequency band of the first and second impedance elements is set so that a value normalized by one characteristic impedance value in the balanced terminal is 3 or more. The balanced high-frequency circuit according to claim 27 or 28. A communication device using the balanced high-frequency filter according to claim 1. A communication device using the antenna duplexer according to claim 13 or 14. A communication device using the balanced high-frequency circuit according to claim 16. A communication device using the balanced high-frequency circuit according to claim 23 or 24.

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