JP2008103830A - Filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturized filter capable of input or output of a balanced signal and satisfactorily removing unwanted signal components out of a pass band. <P>SOLUTION: The filter is provided with a first resonator 1 consisting of a pair of 1/4 wavelength resonators 10, 20; and a differential amplifier 7 connected to a pair of balanced terminals 4A, 4B. Signals filtered by the first resonator 1 are outputted from the pair of balanced terminals 4A, 4B. A balanced signal is inputted into an input side of the differential amplifier 7 in a pass frequency band (on the basis of action of a second resonation mode having a low frequency). A common mode signal is inputted into the differential amplifier 7 in a frequency side higher than the pass frequency (on the basis of action of a first resonation mode having a high frequency). However, since the differential amplifier 7 does not amplify the common mode signal, a high frequency component is removed. As a result, only the balanced signal in the pass frequency band can be satisfactorily transmitted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a small filter suitable for a wireless communication device such as a mobile phone, and more particularly to a filter having a balanced terminal.

  For example, there is a demand for downsizing and low loss in a filter used in a radio communication device such as a mobile phone. Therefore, the resonator constituting the filter is also required to be downsized and low loss. Here, as a filter having a balanced terminal, for example, an unbalanced input-balanced output type bandpass filter is known. One such filter uses a balun. The balun mutually converts an unbalanced signal (unbalanced signal) and a balanced signal (balanced signal). Note that, in a line for transmitting an unbalanced signal, a signal is transmitted by the potential of one signal line with respect to a certain reference potential (usually a ground potential). In a line that transmits a balanced signal, a signal is transmitted by a potential difference between a pair of signal lines. A balanced signal can generally be said to be in a state of excellent balance characteristics if the phase of each signal transmitted between a pair of signal lines is 180 ° different from each other and the amplitudes are approximately equal.

  FIG. 23 shows the general structure of a balun. This balun includes a ½ wavelength (λ / 2) resonator 201 and first and second ¼ wavelength resonators 202 and 203. The half-wave resonator 201 has both ends open (open), and an unbalanced input terminal 211 is connected to one open end. The short-circuit ends of the first and second quarter-wave resonators 202 and 203 are opposed to the half-wave resonator 201 so that the open ends of the half-wave resonator 201 are opposed to each other. Are arranged. Balanced output terminals 212 and 213 are connected to the open ends of the first and second quarter-wave resonators 202 and 203, respectively, and a pair of balanced output terminals is formed.

As a balun having this structure, there are stacked balun transformers described in Patent Document 1 and Patent Document 2. In Patent Document 1 and Patent Document 2, each resonator is formed by a spiral conductor line pattern, and the conductor line pattern is formed on a plurality of dielectric substrates to form a laminated structure, thereby reducing the size. I am trying. Patent Documents 3 and 4 describe a multilayer bandpass filter using a half-wave resonator as a balanced output type bandpass filter.
JP 2002-190413 A JP 2003-007537 A JP 2005-045447 A JP-A-2005-080248

  However, in the multilayer balun transformer described in Patent Document 1 and Patent Document 2, the overall size is limited by the size of the 1/2 wavelength resonator (the size of 1/2 wavelength of the operating frequency), Miniaturization is difficult. Patent Documents 1 and 2 also disclose that each resonator has a spiral structure, but in that case, unnecessary coupling between lines and the balance of physical arrangement are lost from the ideal state. For this reason, there is a problem that the amplitude balance and the phase balance are lost when balanced output is performed, and desired characteristics cannot be obtained. Similarly, the multilayer bandpass filters described in Patent Document 3 and Patent Document 4 basically use a ½ wavelength resonator, so that the overall size depends on the size of the ½ wavelength resonator. It is limited and it is difficult to reduce the size.

  Further, it is desirable that the filter removes signal components other than the desired passband satisfactorily. On the other hand, a signal amplifier circuit may be connected to the input side or output side of the filter. However, in general, an amplifier circuit exhibits nonlinear characteristics when an input signal becomes a large signal, and a harmonic signal of 2 times, 3 times, 4 times, 5 times,. Appears. If there is such an unnecessary signal, extra power is consumed and the efficiency of the power deteriorates. Moreover, since it is regulated by law to output such unnecessary signals, it is necessary to prevent the signals from going outside. As a technique for suppressing the distortion component of such an amplifier circuit, there is a technique that employs a circuit configuration in which the distortion components cancel each other out of phase by using, for example, a delay circuit or a directional coupler. However, when a delay circuit or a directional coupler is used, the size of the entire circuit is increased.

  In addition, in a filter that receives or outputs a balanced signal, not only the out-of-band component of the balanced signal (differential mode) but also the common mode even when the common-mode out-of-band component is superimposed on the input or output side. It is desirable that the out-of-band component is removed well.

  In a filter having a balanced terminal, other circuits such as an IC (integrated circuit) are usually connected to the balanced terminal. For example, in a cellular phone or the like, an IC differential amplifier circuit is connected. A DC voltage is required as a power supply voltage for driving the IC and the like. In this case, the power supply voltage can be supplied from the balanced terminal to the IC or the like by applying a DC bias voltage to the balanced signal. For this reason, it is desirable that the resonator to which the balanced terminal is connected be configured to be able to apply a bias voltage. For this purpose, the resonator on the output side must not be connected to the ground electrode in a direct current manner.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a miniaturized filter that can input or output a balanced signal and can satisfactorily remove unnecessary signal components outside the passband. It is to provide.

The filter according to the present invention includes a first resonator having at least one pair of quarter-wave resonators interdigitally coupled to each other, a pair of balanced terminals connected to the first resonator, and an input side or A differential amplifier having a pair of balanced terminals connected to the output side, and a pair of quarter-wave resonators, when the pair of quarter-wave resonators are not interdigitally coupled, the resonance frequency of a single quarter-wave resonator as f ₀ the time, resonance with the first resonant mode and the second lower than the resonance frequency f ₀ at a single resonance frequency f ₂ which resonates at a first resonance frequency f ₁ is higher than the resonance frequency f ₀ by itself And a pass frequency as a filter is set to the _second resonance frequency f ₂ .

In the filter according to the present invention, since the first resonator is composed of a pair of quarter-wave resonators that are interdigitally coupled, the size can be easily reduced. Here, when the pair of quarter-wave resonators is interdigital type and strongly coupled, the resonance frequency f ₀ determined by the length of the physical quarter-wavelength (one each when the interdigital coupling is not performed). The first resonance mode that resonates at a _first resonance frequency f ₁ that is higher than the resonance frequency f ₁ , and the second resonance frequency f ₂ that is lower than the resonance frequency f _0. Two modes, the second resonance mode, appear and the resonance frequency is separated into two. In this case, by setting the second resonance frequency f ₂ having a frequency lower than the resonance frequency f ₀ corresponding to the physical length to the pass frequency (operating frequency) as the filter, the pass frequency as the filter Can be made smaller than when the resonance frequency is set to the resonance frequency f ₀ . Further, the second resonance mode resonating at the second resonance frequency f ₂ having a low frequency is an excitation mode in which the pair of quarter-wave resonators are in opposite phases to each other, and thus has excellent balance characteristics. In the second resonance mode having a low frequency, the current i flows in the same direction in each resonator, and the conductor thickness increases in a pseudo manner, so that the conductor loss is reduced.

When having such two resonance modes, the first resonance mode having a high frequency corresponds to the common mode and the second resonance mode having a low frequency corresponds to the differential mode at the position where the pair of balanced terminals are connected. To do. On the other hand, since the differential amplifier amplifies a differential signal (balanced signal), it does not amplify even when a common mode signal is input. For this reason, in the case of a configuration in which a pair of balanced terminals are connected to the input side of the differential amplifier, first, by the action of the first resonator, in the pass frequency band (by the action of the second resonance mode having a low frequency). ) A balanced signal is input to the differential amplifier, and a common mode signal is input to the differential amplifier on the higher frequency side than the passing frequency (due to the action of the first resonance mode having a higher frequency). However, since the differential amplifier does not amplify the common mode signal, the high frequency component is removed. As a result, only the balanced signal in the pass frequency band is transmitted well.
Conversely, in the case of a configuration in which a pair of balanced terminals are connected to the output side of the differential amplifier, only the balanced signal among the input signals is amplified by the differential amplifier and is not amplified even if the common mode signal is input. . Only the balanced signal amplified by the differential amplifier is input to the first resonator via a pair of balanced terminals. In this case, even if a signal component of harmonic distortion (balanced signal) with respect to the pass frequency is output from the differential amplifier, the first resonator has a higher frequency than the pass frequency (the first high frequency). Since only the common mode signal is transmitted (due to the action of the resonance mode), the harmonic distortion signal component of the balanced signal cannot pass, and as a result, only the balanced signal in the pass frequency band is transmitted satisfactorily.

In the filter according to the present invention, the first resonator has a rotationally symmetric axis and has a rotationally symmetric structure as a whole, and one terminal and the other terminal of the pair of balanced terminals are mutually connected with respect to the rotationally symmetric axis. It is preferable to be connected to the first resonator at a rotationally symmetric position.
By adopting such a configuration, the balanced signal is transmitted with excellent balance characteristics.

In the filter according to the present invention, the pair of quarter-wave resonators are interdigitally coupled to each other by one end being an open end and the other end functioning as a short-circuited end during resonance. A connection conductor that conducts the short-circuit ends of the device and a DC voltage application terminal that is connected to the connection conductor and supplies a power supply voltage to the differential amplifier may be further provided.
In this case, “the other end functions as a short-circuited end during resonance” does not mean that the other end is connected to the ground potential, but when the electric field distribution at the time of resonance is observed, the other end is at least at the time of resonance. This means that the potential is AC in terms of zero potential (that is, the resonance frequency component is zero potential at the other end during resonance). In this case, even if a DC bias voltage is applied, it functions as a short-circuited terminal if it is zero potential in terms of AC.
Also, in this case, “a pair of interdigitally coupled quarter-wave resonators” means the open end of one quarter-wave resonator and the short-circuited end during resonance of the other quarter-wave resonator. Are arranged so that the short-circuited end at the time of resonance of one quarter-wave resonator and the open end of the other quarter-wave resonator are opposed to each other. Says the vessel.

  In the case of this configuration, the short-circuit ends of the pair of quarter-wave resonators in the first resonator are connected to each other by the connection conductor, and a DC voltage application terminal is connected to the connection conductor to supply a DC voltage. . Here, in order to interdigitally couple a pair of quarter-wave resonators, one end of each quarter-wave resonator is normally an open end and the other end is a short-circuited end, and the other end is a ground electrode. Connected and physically dropped to ground potential. However, when it is physically lowered to the ground potential, a voltage is applied to the ground electrode, and power cannot be supplied to the load side. On the other hand, even if each quarter wavelength resonator is not connected to the ground electrode, at the time of resonance, one end becomes an open end and the other end becomes an AC zero potential. In the filter according to the present invention, by utilizing the property at the time of resonance, the other end of the pair of quarter-wave resonators in the first resonator is equivalently interdigitally at the time of resonance without being connected to the ground electrode. Bonds are made. In this case, since the other end is not connected to the ground electrode, a pair of 1/4 wavelength resonators can be obtained by connecting a DC voltage application terminal between the other ends (short-circuit ends) of the pair of 1/4 wavelength resonators. Is supplied with a DC voltage. As a result, a bias voltage is applied in a DC manner to the balanced signal flowing through the pair of balanced terminals, and the power supply voltage can be supplied to the differential amplifier via the pair of balanced terminals.

The filter according to the present invention further includes a second resonator having at least one pair of another pair of quarter-wave resonators that are interdigitally coupled to each other and electromagnetically coupled to the first resonator, The first resonator and the second resonator may be electromagnetically coupled at the _second resonance frequency f2.

  In this case, a pair of balanced terminals are connected to the input side of the differential amplifier, another pair of balanced terminals connected to the second resonator, and another pair of balanced terminals connected to the output side. Further, another differential amplifier may be further provided, and a balanced input-balanced output type may be configured as a whole.

  According to the filter of the present invention, the first resonance mode having a pair of quarter-wave resonators coupled interdigitally and having a high frequency corresponding to the common mode and the second low frequency corresponding to the differential mode are provided. A configuration having two resonance modes, a resonance mode, a pass frequency as a filter, a second resonance mode, and a pair of balanced terminals between the differential amplifier and the first resonator. Since the balanced signal is input or output, the balanced signal can be input or output, and unnecessary signal components outside the passband can be removed well. In addition, since the first resonator is composed of a pair of quarter-wave resonators that are interdigitally coupled, the size can be easily reduced.

  Further, in the filter of the present invention, when the short-circuit ends of the pair of quarter-wave resonators at the time of resonance are made conductive by the connecting conductor, and the DC voltage application terminal is connected to the connecting conductor, the first It becomes possible to supply a direct-current voltage to a pair of quarter-wave resonators in this resonator. As a result, a bias voltage can be applied in a DC manner to the balanced signal flowing through the pair of balanced terminals, and a DC voltage can be supplied as a power supply voltage to the differential amplifier via the pair of balanced terminals.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]

First, the filter according to the first embodiment of the present invention will be described.
FIG. 1 shows a first basic configuration of the filter according to the present embodiment. FIG. 2 shows a second basic configuration of the filter according to the present embodiment. The filter according to the present embodiment is connected to the first resonator 1, the second resonator 2, the unbalanced terminal 3 connected to the second resonator 2, and the first resonator 1. The pair of balanced terminals 4A and 4B and the differential amplifier 7 connected to the pair of balanced terminals 4A and 4B are provided. The differential amplifier 7 amplifies a differential signal (balanced signal) and has a pair of input terminals 7A and 7B and a pair of output terminals 7C and 7D.

  In the configuration example of FIG. 1, the input side (a pair of input terminals 7A and 7B) of the differential amplifier 7 is connected to the pair of balanced terminals 4A and 4B, whereby the unbalanced terminal 3 is used as an input terminal as a whole. An unbalanced input-balanced output type filter is configured. On the other hand, in the configuration example of FIG. 2, the output side (a pair of output terminals 7C and 7D) of the differential amplifier 7 is connected to the pair of balanced terminals 4A and 4B, thereby using the unbalanced terminal 3 as an output terminal. As a whole, a balanced input-unbalanced output type filter is configured.

  The first and second resonators 1 and 2 are constituted by TEM (Transverse Electro Magnetic) lines. The TEM line can be composed of a conductor pattern such as a strip line or a through conductor formed inside the dielectric substrate. The TEM line is a transmission line that transmits an electromagnetic wave (TEM wave) in which both an electric field and a magnetic field exist only in a cross section perpendicular to the traveling direction of the electromagnetic wave.

  The first resonator 1 includes a pair of quarter-wave resonators 10 and 20 that are interdigitally coupled to each other. The first resonator 1 has a rotationally symmetric axis 5 and has a rotationally symmetric structure as a whole. Of the pair of quarter-wave resonators 10 and 20, one balanced terminal 4A is connected to one quarter-wave resonator 10, and the other balanced terminal 4B is connected to the other quarter-wave resonator 20. Is connected. The pair of balanced terminals 4A and 4B are preferably connected to the pair of quarter-wave resonators 10 and 20 at positions that are rotationally symmetric with respect to the rotational symmetry axis 5. Thereby, it can be set as the state excellent in the balance characteristic.

  The interdigital coupling means that one end of the pair of quarter-wave resonators 10 and 20 is an open end, the other end is a short-circuited end, and the open end of one quarter-wave resonator 10 and the other quarter. The short-circuited end of the wavelength resonator 20 is opposed to the short-circuited end of one quarter-wave resonator 10 and the open end of the other quarter-wave resonator 20 is opposed to each other. This means that the / 4 wavelength resonators 10 and 20 are electromagnetically coupled.

  Similarly to the first resonator 1, the second resonator 2 has another pair of quarter-wave resonators 30 and 40 that are interdigitally coupled to each other. The unbalanced terminal 3 is connected to one of the other pair of quarter wavelength resonators 30 and 40. Similarly to the pair of quarter wavelength resonators 10 and 20, the other pair of quarter wavelength resonators 30 and 40 may have a rotationally symmetric axis 6 and may have a rotationally symmetric structure as a whole.

As will be described later, the pair of quarter-wave resonators 10 and 20 are strongly interdigitally coupled at the time of resonance, so that the first resonance mode that resonates at the first resonance frequency f ₁ and the first resonance mode f ₁ And a second resonance mode that resonates at a _second resonance frequency f ₂ lower than the resonance frequency f ₁ . More specifically, when the resonance frequency of each of the quarter-wave resonators 10 and 20 when not interdigitally coupled is f ₀ , the first resonance frequency that is higher than the resonance frequency f ₀ of the single wave resonator. It has a first resonance mode that resonates at f ₁ and a second resonance mode that resonates at a _second resonance frequency f ₂ that is lower than the single resonance frequency f ₀ . Then, the operating frequency (pass frequency of the filter) is configured such that the second resonance frequency f _2.

Similarly, the other pair of quarter-wave resonators 30 and 40 in the second resonator 2 has two resonance modes and is configured to operate at a _second resonance frequency f ₂ having a low frequency. Yes. The filter is configured such that the first resonator 1 and the second resonator ₂ resonate at a _second resonance frequency f ₂ having a low frequency and are electromagnetically coupled. Thus, an unbalanced input-balanced output type or balanced input-unbalanced output type band-pass filter having the second resonance frequency f ₂ as a pass band is configured.

Next, the operation of the filter according to the present embodiment will be described.
First, the resonance mode of a pair of quarter-wave resonators that are interdigitally coupled and constitute the first and second resonators 1, 2 will be described. First, referring to FIG. 5 and FIG. 6, a resonance mode when two resonators that resonate at the same frequency are coupled will be considered. When the distance between the resonators is long, the resonators do not couple at all, so the resonance peaks overlap at the same frequency, but when the resonators are brought close together, radio wave jumps occur, so the resonator is independent. The resonance does not occur, and the two resonators are mixed to form a mixed resonance mode, and the resonance peak is split into two. Here, if the two resonance modes in the hybrid resonance mode are the first resonance mode (mode 1) and the second resonance mode (mode 2), the degree of splitting is small when the coupling between the resonators is weak. As shown in FIG. 5, the bases of the resonance peaks in the two resonance modes overlap. At this time, at the resonance frequency f ₂ of the second resonance mode, which is a low resonance mode, the resonance peaks of the first resonance mode overlap each other, so that the first resonance mode component is slightly included. . However, when strongly coupled, the resonance peak is separated, so that a state having no first resonance mode component can be created at the frequency f ₂ at which the second resonance mode resonates as shown in FIG. In other words, it means that the purity of the resonance mode can be increased by strengthening the coupling between the resonators.

  In the pair of quarter-wave resonators 10 and 20 that are interdigitally coupled in the present embodiment, the resonance state can be divided into two unique resonance modes. The same applies to the other pair of quarter-wave resonators 30 and 40 constituting the second resonator 2. FIG. 3 shows a first resonance mode in the pair of quarter-wave resonators 10 and 20 that are interdigitally coupled, and FIG. 4 shows the second resonance mode. In FIGS. 3 and 4, the curve indicated by the broken line indicates the distribution of the electric field E in each resonator. 3 and 4 show the resonance state of the pair of quarter-wave resonators 10 and 20, and the other end is in the ground state. This is an alternating zero potential. Means.

  In the first resonance mode, the current i flows from the open end side to the short-circuited end side in each of the pair of quarter-wave resonators 10 and 20, and the direction of the current i flowing in each of them is opposite. In the first resonance mode, electromagnetic waves are excited in phase by the pair of quarter-wave resonators 10 and 20. In this first resonance mode, the phase and amplitude of the electric field E are the same at positions that are rotationally symmetric with respect to the physical rotational symmetry axis of the entire pair of quarter-wave resonators. That is, the first resonance mode corresponds to the common mode. If the pair of balanced terminals 4A and 4B are connected to rotationally symmetric positions, a common mode signal is output from the pair of balanced terminals 4A and 4B in the first resonance mode.

  On the other hand, in the second resonance mode, the current i flows from the open end side to the short-circuit end side in one quarter-wave resonator 10 and the other quarter-wave resonator 20 from the short-circuit end side to the open end side. The current i flows through each of them, and the direction of the current i flowing through each of them is the same. That is, in this second resonance mode, as can be seen from the distribution of the electric field E, the pair of quarter-wave resonators 10 and 20 excites electromagnetic waves in opposite phases. In this second resonance mode, the phase of the electric field E is 180 ° different from each other at a rotationally symmetric position with respect to the physical rotational symmetry axis of the entire pair of quarter wavelength resonators, and the absolute value of the amplitude is the same. Become. That is, the second resonance mode corresponds to the differential mode. If the pair of balanced terminals 4A and 4B are connected to a rotationally symmetric position, a balanced signal with good amplitude balance and phase balance can be extracted from the pair of balanced terminals 4A and 4B in the second resonance mode.

By the way, as described with reference to FIGS. 5 and 6, two resonators coupled sufficiently strongly can completely separate the two resonance modes in terms of frequency. That is, if the interdigital coupling is made very strong in the pair of quarter-wave resonators 10 and 20, the second resonance mode in which a balanced signal is output and the first resonance mode in which an unbalanced signal is output. Can be completely separated in frequency. Therefore, by setting the f ₂ frequency pass as a filter to the resonant frequency of the second resonance mode, better balanced signal is obtained.

FIG. 7 shows a distribution state of resonance frequencies in the pair of quarter-wave resonators 10 and 20 that are interdigitally coupled. As a feature of the interdigital coupling, a resonance frequency f ₀ intermediate between the first resonance frequency f ₁ and the second resonance frequency f ₂ is obtained when the resonance occurs at a quarter wavelength determined by the physical length of the line. Frequency (resonance frequency of each ¼ wavelength resonator when not interdigitally coupled). Therefore, by setting the _second resonance frequency f ₂ having a low frequency as the pass frequency, the entire resonator can be made smaller than when the pass frequency is set to the resonance frequency f ₀ . For example, when designing a filter having a pass frequency in the 2.4 GHz band, a quarter wavelength resonator having a physical length corresponding to, for example, 8 GHz can be used. This is smaller than the case of a quarter wavelength resonator whose physical length corresponds to the 2.4 GHz band. Further, in the second resonance mode, when the coupling is strengthened, a magnetic field distribution equivalent to a state in which the pair of quarter-wave resonators 10 and 20 are virtually regarded as one conductor is obtained, and the conductor is virtually There is an advantage that the thickness is increased and the conductor loss can be reduced.

In interdigital coupling, the stronger the coupling is, the more the two resonance modes are split, and the resonance frequency f ₂ of the second resonance mode is lowered and the resonance frequency f ₁ of the first resonance mode is raised. As a result, when the second resonance mode is the pass band, the higher-order resonance mode can be separated in frequency. The high-frequency resonance mode corresponds to a common mode with balanced amplitude.

  By combining the first resonator 1 having the pair of quarter-wave resonators 10 and 20 having such characteristics and the differential amplifier 7, the following operations are performed in the configuration examples of FIGS. 1 and 2, respectively. Is obtained.

  In the filter according to the configuration example of FIG. 1, the unbalanced signal input from the unbalanced terminal 3 is filtered by the resonance action of the first and second resonators 1 and 2, and the filtered signal is a pair of balanced signals. Output from terminals 4A and 4B. A balanced signal is input to the input side of the differential amplifier 7 in the pass frequency band (due to the action of the second resonance mode having a low frequency). A common mode signal is input to the differential amplifier 7 on the higher frequency side than the pass frequency (due to the action of the first resonance mode having a higher frequency). However, since the differential amplifier 7 does not amplify the common mode signal, the high frequency component is removed. As a result, only the balanced signal in the pass frequency band is transmitted well.

  In the filter according to the configuration example of FIG. 2, a balanced signal is input to the pair of balanced terminals 4 </ b> A and 4 </ b> B via the differential amplifier 7. Here, in the differential amplifier 7, only the balanced signal among the input signals is amplified, and the common mode signal is not amplified even if it is input. Only the balanced signal amplified by the differential amplifier 7 is input to the first resonator 1 via the pair of balanced terminals 4A and 4B. The balanced signal is filtered by the resonance action of the first and second resonators 1 and 2 and output from the unbalanced terminal 3 as an unbalanced signal. In this case, even if a signal component of harmonic distortion (balanced signal) with respect to the pass frequency is output from the differential amplifier 7, the first and second resonators 1 and 2 are on the higher frequency side than the pass frequency. Since only the signal of the common mode is transmitted (due to the action of the first resonance mode having a high frequency), the harmonic distortion signal component of the balanced signal cannot pass, and as a result, only the balanced signal in the pass frequency band can be passed. Good transmission.

As described above, according to the present embodiment, the first resonance mode and the differential mode having a pair of quarter-wave resonators 10 and 20 that are interdigitally coupled and having a high frequency corresponding to the common mode. And a second resonance mode having a low frequency corresponding to the frequency, and a pass frequency as a filter is set to the second resonance mode, and the difference is made via a pair of balanced terminals 4A and 4B. Since the balanced signal is input or output between the dynamic amplifier 7 and the first resonator 1, the balanced signal can be input or output, and unnecessary signal components outside the passband can be satisfactorily removed. be able to. Further, since the first and second resonators 1 and 2 are constituted by a pair of quarter-wave resonators 10, 20, 30, and 40 that are interdigitally coupled, miniaturization is facilitated.
[Specific Configuration Example of First Embodiment]

  Hereinafter, a specific configuration example of the resonator portion of the filter according to the first embodiment will be described. In the following configuration example, parts corresponding to the basic configuration shown in FIG.

  8 and 9A and 9B show specific configuration examples. 9A and 9B show the inner layer in FIG. 8 in an exploded manner. FIG. 9A shows the configuration on the lower layer side, and FIG. 9B shows the configuration on the upper layer side. This configuration example includes a substantially rectangular parallelepiped-shaped dielectric block made of a dielectric material, and the dielectric block has a multilayer structure. A conductor line pattern (strip line) is formed inside the dielectric block, and a pair of quarter-wave resonators 10 and 20 and another pair of quarter-wave resonators 30 are formed by the inner line pattern. , 40, an unbalanced terminal 3, and a pair of balanced terminals 4A, 4B are formed as an inner layer. In such a structure, for example, a plurality of sheet-like dielectric substrates are prepared, each line portion is formed on the sheet-like dielectric substrate with a conductor line pattern, and the sheet-like dielectric substrate is overlaid. This can be realized by using a laminated structure. Two opposing side surfaces of the dielectric block are ground electrodes 101 and 102.

  In this configuration example, the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 30 and 40 are each formed with a linear conductor line pattern. The pair of quarter-wave resonators 10 and 20 are stacked in separate planes and are arranged opposite to each other. Similarly, the other pair of quarter-wave resonators 30 and 40 are also laminated in separate planes and are arranged to face each other. One end of one quarter wavelength resonator 10 is an open end, and a conductor line pattern serving as one balanced terminal 4A is linearly formed on the open end side. The other end is connected to the ground electrode 102 on the side surface and serves as a short-circuit end. Similarly, one end of the other quarter wavelength resonator 20 is an open end, and a conductor line pattern to be the other balanced terminal 4B is linearly formed on the open end side. The other end is connected to the ground electrode 101 on the side surface and is a short-circuited end. In the other pair of quarter-wave resonators 30 and 40, one end of one quarter-wave resonator 30 is an open end, and the other end is connected to the ground electrode 101 on the side surface and is a short-circuit end. ing. Further, one end of the other quarter wavelength resonator 40 is an open end, and a conductor line pattern serving as the unbalanced terminal 3 is formed linearly on the open end side. The other end is connected to the ground electrode 102 on the side surface and serves as a short-circuit end.

  In this configuration example, the dimensions of each part are as shown in FIGS. 8 and 9A and 9B. The dielectric constant inside the dielectric block is 7.5. The pair of quarter-wave resonators 10 and 20 are arranged to face each other at an interval of 20 μm and are interdigitally coupled. Similarly, the other pair of quarter-wave resonators 30 and 40 are arranged to face each other at an interval of 20 μm and are interdigitally coupled.

  In this configuration example, as shown in FIG. 10, the unbalanced terminal 3 is the port 1, one balanced terminal 4A is the port 3, and the other balanced terminal 4B is the port 2. FIG. 11 shows the S parameter characteristics in this case. In FIG. 11, the horizontal axis represents frequency, and the vertical axis represents attenuation. S11 indicates the ratio of the signal that is reflected back to port 1 when a signal is input to port 1. S21 indicates the ratio of signals transmitted to port 2 when signals are input to port 1. S31 indicates the ratio of signals transmitted to port 3 when signals are input to port 1. FIG. 12 shows a phase difference (S21-S31) of signals output between the pair of balanced terminals 4A and 4B. As can be seen from FIG. 12, the phase difference is 180 degrees near the pass frequency, but the phase difference is 0 degrees on the higher frequency side. That is, a balanced signal (differential mode) is transmitted near the pass frequency, and an unbalanced signal (common mode) is transmitted on the higher frequency side.

Here, in order to examine the transmission rate in each mode in more detail, port conversion as shown in FIG. 13 is performed. Normal S-parameters are represented by the following matrix.

Instead of the ports 2 and 3, a port d for transmitting a differential mode signal and a port c for transmitting a common mode signal are introduced. In this case, the S parameter S ′ can be converted into the following matrix using a normal S parameter. Here, for example, Sd1 represents the rate at which a signal input from port 1 is converted to a differential mode signal and transmitted to port d, and Sc1 is a signal input from port 1 converted to a common mode signal. The ratio transmitted to port c is shown.

FIG. 14 shows the result of calculating the converted S-parameter characteristics. In FIG. 14, the horizontal axis represents frequency, and the vertical axis represents attenuation. As can be seen from the graph of FIG. 14, it is understood that a common mode signal is transmitted at a frequency higher than the passing frequency. Such a common mode signal can be removed by combining the differential amplifier 7. That is, by combining the resonator shown in FIG. 8 and FIGS. 9A and 9B with the differential amplifier 7 as shown in FIG. 1, only the balanced signal can be transmitted satisfactorily.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component substantially the same as the filter which concerns on the said 1st Embodiment, and description is abbreviate | omitted suitably.

  FIG. 15 shows a first basic configuration of the filter according to the present embodiment. In the configuration example of FIG. 15, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 constituting the first resonator 1 are made conductive by the connection conductor 8 and connected to the configuration example of FIG. 1. A DC voltage application terminal 4C is connected to the conductor 8. In general, the interdigital coupling means that, as shown in FIG. 1, one end of a pair of quarter-wave resonators 10 and 20 has an open end and the other end is a short-circuited end. The open end and the short-circuit end of the other quarter-wave resonator 20 face each other, and the short-circuit end of one quarter-wave resonator 10 and the open end of the other quarter-wave resonator 20 face each other. It arrange | positions so that a pair of 1/4 wavelength resonators 10 and 20 may be electromagnetically coupled. For this reason, normally, in order to set the other end as a short-circuited end, the other end is connected to a ground electrode and is physically dropped to the ground potential (0 V). However, in actual use, in order to perform interdigital coupling, the other end does not need to be at the ground potential, and it is sufficient that the other potential is zero potential in terms of alternating current. On the other hand, at the operating resonance frequency at the time of resonance, even if the pair of quarter-wave resonators 10 and 20 is not connected to the ground electrode, the other end becomes an alternating potential of zero potential (the resonance frequency component is zero at the time of resonance). Potential). That is, at the operating resonance frequency at the time of resonance, the other end automatically functions as a short-circuited end. In the present embodiment, due to this property, the pair of quarter-wave resonators 10 and 20 are interdigitally coupled.

  In the present embodiment, “the other end functions as a short-circuited end during resonance” does not mean that the other end is connected to the ground potential, but the other end when the electric field distribution during resonance is viewed. Means at least zero potential in an alternating manner at the time of resonance (that is, the resonance frequency component at the other end has a zero potential at the time of resonance). In this case, even if a DC bias voltage is applied, it functions as a short-circuited terminal if it is zero potential in terms of AC. Further, “a pair of interdigitally coupled quarter-wave resonators” means that the open end of one quarter-wave resonator 10 and the short-circuited end of the other quarter-wave resonator 20 during resonance. Resonance that is electromagnetically coupled to each other by being arranged so that the short-circuited end at the time of resonance of one quarter-wave resonator 10 and the open end of the other quarter-wave resonator 20 face each other. Says the vessel.

  As shown in FIG. 16 as the second basic configuration, the other pair of quarter-wave resonators 30 and 40 constituting the second resonator 2 is also a pair of one 1 in the first resonator 1. Like the / 4 wavelength resonators 10 and 20, the other ends (short-circuited ends at the time of resonance) are connected to each other by the connecting conductor 9, and the other end is interdigitally coupled without being connected to the ground electrode. Also good. In this case, the other pair of quarter-wave resonators 30 and 40, like the pair of quarter-wave resonators 10 and 20, has one end as an open end and the other end functions as a short-circuited end during resonance. Are interdigitally coupled to each other.

  In the filter according to the present embodiment, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 are connected to each other by the connection conductor 8, and the DC voltage application terminal 4 </ b> C is connected to the connection conductor 8 to supply the DC voltage. Is done. Here, in order to interdigitally couple the pair of quarter-wave resonators 10 and 20, normally, as shown in FIG. 1, one end of each quarter-wave resonator is open and the other end is short-circuited. In order to achieve this, the other end is connected to the ground electrode and physically dropped to the ground potential. However, if the voltage is physically lowered to the ground potential, the power is consumed at the ground when the DC voltage is supplied, and the power is not transmitted to the load. On the other hand, as described above, even if each quarter-wave resonator is not connected to the ground electrode, at the time of resonance, one end becomes an open end and the other end becomes an alternating zero potential. In this embodiment, by utilizing this characteristic at the time of resonance, interdigital coupling is equivalently performed at the time of resonance without connecting the other ends of the pair of quarter-wave resonators 10 and 20 to the ground electrode. The In this case, since the other end is not connected to the ground electrode, the power is grounded by connecting the DC voltage application terminal 4C between the other ends (short-circuit ends) of the pair of quarter-wave resonators 10 and 20. A DC voltage is supplied to the pair of quarter-wave resonators 10 and 20 without being consumed. As a result, a bias voltage is applied to the balanced signals flowing in the pair of balanced terminals 4A and 4B in a DC manner, and the power supply is supplied to the differential amplifier 7 and an external circuit (not shown) via the pair of balanced terminals 4A and 4B. The voltage can be supplied.

Other operations and effects are the same as those in the first embodiment. Also, in the configuration example of FIG. 2, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 are electrically connected by the connection conductor 8, and the DC voltage application terminal 4 </ b> C is connected to the connection conductor 8. Anyway.
[Specific Configuration Example of Second Embodiment]

Hereinafter, a specific configuration example of the resonator portion of the filter according to the present embodiment will be described. In the following configuration example, parts corresponding to the basic configuration shown in FIG. 15 or FIG.
<First specific configuration example>

  17 and 18 show a first specific configuration example of the filter according to the present embodiment. In FIG. 17, the inner layer is omitted, and only the appearance portion is shown in perspective. FIG. 18 is an exploded view of the inner layer omitted in FIG. This configuration example corresponds to the basic configuration of FIG. As shown in FIG. 17, this filter includes a substantially rectangular parallelepiped dielectric block 61 made of a dielectric material, and the dielectric block 61 has a multilayer structure. A conductor line pattern (strip line) is formed inside the dielectric block 61, and another pair of quarter-wave resonators 30, 40 constituting the second resonator 2 is formed by the line pattern inside the dielectric block 61. The unbalanced terminal 3, the pair of quarter-wave resonators 10 and 20 constituting the first resonator 1, the pair of balanced terminals 4A and 4B, and shield electrodes 71 and 72 and 73 and 74 described later. Are formed as an inner layer. On the first side surface of the dielectric block 61, an external terminal electrode for applying a DC voltage to be the DC voltage applying terminal 4C is formed. Further, on the first side surface of the dielectric block 61, external terminal electrodes 62 and 63 for balanced terminals to which a pair of balanced terminals 4A and 4B are connected are formed on both sides of the external terminal electrode for applying DC voltage. ing. Further, external terminal electrodes 64 and 65 for connection that are part of the connection conductor 8 are formed on the second and third side surfaces of the dielectric block 61, respectively. The second and third side surfaces of the dielectric block 61 also have “reference voltage application terminals” for keeping the short-circuit ends of the other pair of quarter-wave resonators 30 and 40 at the reference voltage (ground voltage). The external terminal electrodes 82 and 83 for applying the reference voltage are formed. Furthermore, an external terminal electrode 81 for an unbalanced terminal to which the unbalanced terminal 3 is connected is formed on the fourth side surface of the dielectric block 61.

  In this configuration example, as shown in FIG. 18, the pair of quarter-wave resonators 10 and 20 are formed with a substantially linear conductor line pattern. One end of one quarter-wave resonator 10 is an open end, and a conductor line pattern serving as one balanced terminal 4A is linearly formed in a substantially right angle direction at the open end. As a result, an L-shaped line pattern is formed as a whole. The line pattern of the linear conductor serving as one balanced terminal 4A extends to one external terminal electrode 62 on the first side surface of the dielectric block 61 and is conducted. Similarly, one end of the other quarter-wave resonator 20 is an open end, and a conductor line pattern serving as the other balanced terminal 4B is linearly formed in a substantially right angle direction at the open end. As a result, an L-shaped line pattern is formed as a whole. The line pattern of the linear conductor serving as the balanced terminal 4B extends to the other external terminal electrode 63 on the first side surface of the dielectric block 61 and is conductive.

  In addition, the other end of one quarter wavelength resonator 10 is a short-circuited end at the time of resonance, and the short-circuited end extends to the external terminal electrode 65 for connection on the third side surface portion of the dielectric block 61. Is conducting. Similarly, the other end of the other quarter-wave resonator 20 is a short-circuited end during resonance, and the short-circuited end extends to the external terminal electrode 64 for connection on the second side surface portion of the dielectric block 61. And is conducting.

  The other pair of quarter-wave resonators 30 and 40 is also formed by a line pattern of a substantially linear conductor. One quarter-wave resonator 10 in the pair of quarter-wave resonators 10 and 20 and the other quarter-wave resonator 40 in the other pair of quarter-wave resonators 30 and 40 are in the same plane. Are arranged in parallel. Further, the other quarter wavelength resonator 20 in the pair of quarter wavelength resonators 10 and 20 and the other one quarter wavelength resonator 30 in the other pair of quarter wavelength resonators 30 and 40, They are arranged in parallel in the same plane.

  One end of the other quarter-wave resonator 40 in the other pair of quarter-wave resonators 30 and 40 is an open end, and the line pattern of the conductor serving as the unbalanced terminal 3 is substantially perpendicular to the open end. It is formed in a straight line. As a result, an L-shaped line pattern is formed as a whole. The line pattern of the linear conductor serving as the unbalanced terminal 3 extends to the external terminal electrode 81 for the unbalanced terminal on the fourth side surface of the dielectric block 61 and is conducted. Further, the other end of the other quarter wavelength resonator 40 is a short-circuited end, and the short-circuited end extends to the external terminal electrode 83 for applying the reference voltage on the third side surface portion of the dielectric block 61. Conducted. Similarly, one quarter wavelength resonator 30 has one open end and the other short-circuited end, and the short-circuited end is an external terminal electrode for applying a reference voltage on the second side surface portion of the dielectric block 61. It extends to 82 and is conducted.

  The filter according to this configuration example further includes shield electrodes 71 and 72 that prevent propagation of electromagnetic waves from the pair of quarter-wave resonators 10 and 20 to the outside. The shield electrode 71 is laminated on the upper layer side with respect to the pair of quarter-wave resonators 10 and 20, and the shield electrode 72 is laminated on the lower layer side. The upper layer side shield electrode 71 is provided with a first lead electrode 71A, a second lead electrode 71B, and a third lead electrode 71C. Similarly, the lower extraction electrode 72A is also provided with a first extraction electrode 72A, a second extraction electrode 72B, and a third extraction electrode 72C. The first lead electrodes 71A and 72A of the shield electrodes 71 and 72 extend to the external terminal electrode 64 for connection on the second side surface portion of the dielectric block 61 and are electrically connected. The second lead electrodes 71B and 72B extend to the external terminal electrode 65 for connection on the third side surface portion of the dielectric block 61 and are electrically connected. The third lead electrodes 71C and 72C extend to the external terminal electrode for DC voltage application (DC voltage application terminal 4C) on the first side surface portion of the dielectric block 61 and are conductive.

  The filter also includes shield electrodes 73 and 74 that prevent propagation of electromagnetic waves from the other pair of quarter-wave resonators 30 and 40 to the outside. The shield electrode 73 is laminated on the upper layer side with respect to the other pair of quarter-wave resonators 30 and 40, and the shield electrode 74 is laminated on the lower layer side. A pair of quarter-wave resonators 10 and 20 upper shield electrode 71 and another pair of quarter-wave resonators 30 and 40 upper shield electrode 73 are arranged in parallel in the same plane. Has been. The shield electrode 72 on the lower layer side of the pair of quarter-wave resonators 10 and 20 and the shield electrode 74 on the lower layer side of the other pair of quarter-wave resonators 30 and 40 are parallel in the same plane. Is arranged.

  A first extraction electrode 73A and a second extraction electrode 73B are provided on the shield electrode 73 on the upper layer side of the other pair of quarter-wave resonators 30 and 40. Similarly, the first lead electrode 74A and the second lead electrode 72B are provided on the lower shield electrode 74 as well. The first lead electrodes 73A and 74A of the shield electrodes 73 and 74 extend to the external terminal electrode 82 for applying the reference voltage on the second side surface portion of the dielectric block 61 and are conducted. The second lead electrodes 73B and 74B extend to the external terminal electrode 83 for applying the reference voltage on the third side surface portion of the dielectric block 61 and are conductive.

  In this configuration example, in the first resonator 1, the other end (short-circuit end at the time of resonance) of one quarter wavelength resonator 10 is connected via the external terminal electrode 65 for connection on the third side surface portion. The shield electrodes 71 and 72 are electrically connected. The other end of the other quarter-wave resonator 20 (short-circuited end at resonance) is electrically connected to the shield electrodes 71 and 72 via the connection external terminal electrode 64 on the second side surface portion. As a result, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 are brought into conduction via the external terminal electrodes 64 and 65 and the shield electrodes 71 and 72 for connection. That is, in this configuration example, the shield electrodes 71 and 72 also serve as the connection conductor 8. Further, the shield electrodes 71 and 72 are further conducted to the DC voltage application terminal 4C via the third lead electrodes 71C and 72C, so that a DC voltage is applied.

  In this configuration example, in the second resonator 2, the other end (short-circuited end) of one quarter wavelength resonator 30 is connected to the external terminal electrode 82 for applying the reference voltage on the second side surface portion. Are connected to the shield electrodes 73 and 74. The other end (short-circuit end) of the other quarter-wave resonator 40 is electrically connected to the shield electrodes 73 and 74 via the external terminal electrode 83 for applying a reference voltage on the third side surface portion. As a result, the short-circuit ends of the other pair of quarter-wave resonators 30 and 40 are conducted through the external terminal electrodes 82 and 83 for applying the reference voltage and the shield electrodes 73 and 74. That is, in this configuration example, the external terminal electrodes 82 and 83 and the shield electrodes 71 and 72 are connected to the connection conductor 9 (FIG. 16) that connects the short-circuit ends of the other pair of quarter-wave resonators 30 and 40. It also functions. The external terminal electrodes 82 and 83 for applying the reference voltage are connected to a ground electrode (not shown), so that the other ends of the other pair of quarter-wave resonators 30 and 40 become the ground potential.

In this configuration example, in the first resonator 1, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 are connected to each other through both the upper and lower shield electrodes 71 and 72. Alternatively, the short-circuit ends may be conducted through only one of them. The same applies to the first resonator 1.
<Second specific configuration example>

  19 and 20 show a second specific configuration example of the filter according to the present embodiment. In FIG. 19, the inner layer is omitted, and only the appearance portion is shown in perspective. FIG. 20 shows the inner layer omitted in FIG. 19 in an exploded manner. This configuration example corresponds to the basic configuration of FIG. In the first specific configuration example shown in FIGS. 17 and 18, the shield electrodes 71 and 72 of the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 30 and 40 are used. The shield electrodes 73 and 74 are formed separately, and the short-circuit ends of the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 30 and 40 through the separate shield electrodes. The short-circuit ends were conducted separately. On the other hand, in this configuration example, the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 30 and 40 share a shield electrode, and the common shield electrode is used for the shield electrode. Short-circuit ends of the quarter-wave resonators are commonly connected. That is, as shown in FIG. 20, this filter includes a common shield electrode 91 on the upper layer side and a common shield electrode 92 on the lower layer side. Further, as shown in FIG. 19, the external terminal electrodes 64 and 82 on the second side surface of the dielectric block 61 in the configuration example of FIG. 17 are shared, and a single external terminal electrode 93 is formed on the second side surface. Is formed. Similarly, the external terminal electrodes 65 and 83 on the third side surface of the dielectric block 61 in the configuration example of FIG. 17 are shared, and a single external terminal electrode 94 is formed on the third side surface.

  The upper-layer shield electrode 91 is provided with a first extraction electrode 91A, a second extraction electrode 91B and a third extraction electrode 91C, and a fourth extraction electrode 91D and a fifth extraction electrode 91E. Similarly, the lower extraction electrode 92A is also provided with a first extraction electrode 92A, a second extraction electrode 92B and a third extraction electrode 92C, and a fourth extraction electrode 92D and a fifth extraction electrode 92E. ing. The first extraction electrodes 91A and 92A and the fourth extraction electrodes 91D and 92D of the shield electrodes 91 and 92 extend to the external terminal electrode 93 on the second side surface portion of the dielectric block 61 and are electrically connected. The second extraction electrodes 91B and 92B and the fifth extraction electrodes 91E and 92E extend to the external terminal electrode 94 on the third side surface portion of the dielectric block 61 and are electrically connected. The third lead electrodes 91C and 92C extend to the external terminal electrode for DC voltage application (DC voltage application terminal 4C) on the first side surface portion of the dielectric block 61 and are conducted.

  In this configuration example, the other end (short-circuited end at the time of resonance) of one quarter wavelength resonator 10 in the first resonator 1 is connected to the shield electrode 91, via the external terminal electrode 94 on the third side surface portion. Conducted to 92. Similarly, the other end of the other quarter-wave resonator 40 in the first resonator 1 (short-circuited end during resonance) is connected to the shield electrodes 91 and 92 via the external terminal electrode 94 on the third side surface portion. Conducted. In addition, the other end of the other quarter wavelength resonator 20 in the first resonator 1 (short-circuited end during resonance) is electrically connected to the shield electrodes 91 and 92 via the external terminal electrode 93 on the second side surface portion. Is done. Similarly, the other end of one quarter wavelength resonator 30 in the second resonator 2 (short-circuited end during resonance) is connected to the shield electrodes 91 and 92 via the external terminal electrode 93 on the second side surface portion. Conducted.

  As a result, the short-circuit ends of the pair of quarter-wave resonators 10 and 20 are made conductive through the external terminal electrodes 93 and 94 and the shield electrodes 91 and 92, and the other pair of quarter-wave resonators 30. , 40 are connected to each other. That is, in this configuration example, the shield electrodes 91 and 92 serve as the connection conductor 8 that conducts the short-circuited ends of the pair of quarter-wave resonators 10 and 20, and the other pair of quarters. It also functions as another connection conductor 9 that conducts the short-circuit ends of the wavelength resonators 30 and 40. Further, the shield electrodes 91 and 92 are further conducted to the DC voltage application terminal 4C via the third lead electrodes 91C and 92C, whereby a DC voltage is applied.

In this configuration example, the short-circuited ends of the quarter-wave resonators are connected to each other through both the upper and lower shield electrodes 91 and 92. However, the short-circuited ends are connected to each other through only one of them. You may make it do.
[Other embodiments]

  The present invention is not limited to the above embodiments, and various modifications can be made. For example, another resonator may be provided at an intermediate stage between the first resonator 1 and the second resonator 2. In this case, the configuration of the resonator at the intermediate stage can be configured by a pair of quarter-wave resonators that are interdigitally coupled to each other, like the first and second resonators 1 and 2.

  In each of the above-described embodiments, the first and second resonators 1 and 2 each have only one pair of quarter-wave resonators. Each of the resonators 1 and 2 may be composed of a plurality of pairs of quarter-wave resonators.

  FIG. 21 shows a configuration example in which the first resonator 1 is composed of a plurality of pairs of quarter-wave resonators. In the configuration example of FIG. 21, as in the configuration example shown in FIG. 15, the short-circuit ends of the pair of quarter-wave resonators are made conductive by the connection conductor 8, and the DC voltage application terminal 4C is connected to the connection conductor 8. Is connected. In this configuration example, the first resonator 1 includes two sets of resonators including a pair of quarter-wave resonators 10 and 20 and another pair of quarter-wave resonators 110 and 120. The pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 110 and 120 are stacked in the same direction so as to face each other, for example. Similarly to the pair of quarter-wave resonators 10 and 20, the other pair of quarter-wave resonators 110 and 120 are connected to each other by one end being an open end and the other end functioning as a short-circuited end during resonance. Digitally coupled. Note that the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 110 and 120 are electromagnetically coupled to each other. It can also be considered that three pairs of quarter-wave resonators are formed by adjacent quarter-wave resonators as a result of interdigital coupling. That is, a first pair of quarter-wave resonators is formed by the quarter-wave resonators 10 and 20 from the upper layer side, and a second pair of quarter-wave resonators is formed by the quarter-wave resonators 20 and 110. It can also be considered that a third pair of quarter-wave resonators is formed by the quarter-wave resonators 110 and 120.

  In this configuration example, the entire structure including the pair of quarter-wave resonators 10 and 20 and the other pair of quarter-wave resonators 110 and 120 has the rotationally symmetric axis 5 as a whole. It has a rotationally symmetric structure. In this configuration example, one terminal 4A and the other terminal 4B of the pair of balanced terminals 4A and 4B are formed into any two quarter-wave resonators at positions where they are rotationally symmetric with respect to the rotational symmetry axis 5. It is preferable that they are connected. For example, one terminal 4A may be connected to the uppermost quarter wavelength resonator 10, and the other terminal 4B may be connected to the lowermost quarter wavelength resonator 120. Thereby, it can be set as the state excellent in the balance characteristic.

  In each of the above embodiments, an unbalanced input-balanced output type or balanced input-unbalanced output type filter has been described as an example. However, the present invention provides a balanced input with both input and output terminals as balanced terminals. The present invention can also be applied to a balanced output type filter.

  FIG. 22 shows a basic configuration of a balanced input-balanced output type filter. This configuration example has the same configuration as the filter shown in FIG. 1 except that the second resonator 2 side has a balanced input configuration. This configuration example includes another pair of balanced terminals 3A and 3B in place of the unbalanced terminal 3 in the configuration example of FIG. In addition, another differential amplifier 170 connected to another pair of balanced terminals 3A and 3B is provided. Similar to the differential amplifier 7, the other differential amplifier 170 amplifies a differential signal (balanced signal), and has a pair of input terminals 170A and 170B and a pair of output terminals 170C and 170D. Yes. In this configuration example, the output side (a pair of output terminals 170C and 1707D) of another differential amplifier 170 is connected to the other pair of balanced terminals 3A and 3B, so that a balanced input-balanced output type as a whole. The band-pass filter is configured.

It is a block diagram which shows the 1st basic composition of the filter which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the 2nd basic composition of the filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the 1st resonance mode of a pair of 1/4 wavelength resonator by which the interdigital coupling was carried out. It is explanatory drawing which shows the 2nd resonance mode of a pair of 1/4 wavelength resonator by which the interdigital coupling was carried out. It is explanatory drawing which shows the resonance mode of two resonators when a coupling degree is weak. It is explanatory drawing which shows the resonance mode of two resonators when a coupling degree is strong. It is explanatory drawing which shows the distribution state of the resonant frequency in a pair of 1/4 wavelength resonator by which the interdigital coupling was carried out. It is a perspective view which shows the specific structural example of the resonator part of the filter which concerns on the 1st Embodiment of this invention. It is a top view which shows the specific structural example of the resonator part of the filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the definition of the input-output port in the filter which concerns on the specific structural example shown in FIG. FIG. 9 is a characteristic diagram illustrating S parameters in the filter according to the specific configuration example illustrated in FIG. 8. It is a characteristic view which shows the phase characteristic in the filter which concerns on the specific structural example shown in FIG. It is explanatory drawing which shows the definition of conversion of an input / output port. It is a characteristic view which shows the converted S parameter. It is a block diagram which shows the 1st basic composition of the filter which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the 2nd basic composition of the filter which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the 1st specific structural example of the filter which concerns on the 2nd Embodiment of this invention. It is a disassembled perspective view which shows the 1st specific structural example of the filter which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the 2nd specific structural example of the filter which concerns on the 2nd Embodiment of this invention. It is a disassembled perspective view which shows the 2nd specific structural example of the filter which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the basic composition of the filter which concerns on other embodiment of this invention. It is a block diagram which shows the other basic composition of the filter which concerns on other embodiment of this invention. It is a block diagram which shows the basic structure of the conventional balun.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st resonator, 2 ... 2nd resonator, 3 ... Unbalanced terminal, 4A, 4B ... Balanced terminal, 4C ... DC voltage application terminal, 5, 6 ... Rotation symmetry axis, 7,170 ... Differential Amplifier, 8, 9 ... connecting conductor, 10, 20, 30, 40 ... 1/4 wavelength resonator, 71, 72, 73, 74, 91, 92 ... shield electrode, 93, 94 ... connecting layer.

Claims (6)

A first resonator having at least one pair of quarter-wave resonators interdigitally coupled to each other;
A pair of balanced terminals connected to the first resonator;
A differential amplifier having the pair of balanced terminals connected to the input side or the output side, and
When the resonance frequency of the single quarter-wave resonator alone when the pair of quarter-wave resonators are not interdigitally coupled is f ₀ , the resonance frequency f ₀ is higher than the single resonance frequency f _0. A filter having a first resonance mode that resonates at a _first resonance frequency f ₁ and a second resonance mode that resonates at a _second resonance frequency f ₂ lower than the resonance frequency f ₀ of the single unit; The filter is characterized in that the pass frequency is set to the _second resonance frequency f ₂ . The first resonator has a rotationally symmetric axis and has a rotationally symmetric structure as a whole,
The one terminal and the other terminal of the pair of balanced terminals are connected to the first resonator at positions that are rotationally symmetric with respect to the rotational symmetry axis. The filter described. In the position where the pair of balanced terminals are connected,
The first resonance mode is a common mode;
The filter according to claim 1 or 2, wherein the second resonance mode is a differential mode. The pair of quarter-wave resonators are interdigitally coupled to each other by one end being an open end and the other end functioning as a short-circuited end during resonance.
A connection conductor for conducting the short-circuit ends of the pair of quarter-wave resonators;
The filter according to any one of claims 1 to 3, further comprising a DC voltage application terminal connected to the connection conductor and configured to supply a power supply voltage to the differential amplifier. A second resonator having at least one other pair of quarter-wave resonators interdigitally coupled to each other and electromagnetically coupled to the first resonator;
The first filter according to any one of claims 1 to 4 resonator and said second resonator is characterized in that it is electromagnetically coupled with the second resonant frequency f _2. The pair of balanced terminals are connected to the input side of the differential amplifier,
Another pair of balanced terminals connected to the second resonator;
And further comprising another differential amplifier connected to the other pair of balanced terminals on the output side,
The filter according to claim 5, wherein the filter is configured as a balanced input-balanced output type as a whole.

Images