JP2009273082A - Left-handed system filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve characteristics of a filter composed by a filter. <P>SOLUTION: In a left-handed system filter, one end of a first parallel body 12 is electrically connected to the other end of a first serial body 11, and one end of a second parallel body 120 is electrically connected to the other end of a second serial body 110. One end of a third serial body 13 is electrically connected to the other end of the first serial body 11, and one end of a fourth serial body 130 is electrically connected to the other end of the second serial body 110. One end of a third parallel body 14 is electrically connected to the other end of the third serial body 13, and one end of a fourth parallel body 140 is electrically connected to the other end of the fourth serial body 130. The other ends of the first, second, third, and fourth parallel bodies 12, 120, 14, and 140 are electrically connected to the ground. A second inter-stage coupling element 19B is interposed between the other end of the third serial body 13 and that of the fourth serial body 130, and the other end of the fourth serial body 130 is electrically connected to a second output end 16B via a second output coupling element 21B. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a left-handed filter used for a mobile phone or the like.

  Conventionally, this type of filter has an input end 1 and an output end 2 as shown in FIG. 11, and an interstage coupling element 3 is interposed between the input end 1 and the output end 2. One end of a first series body 4 composed of a capacitor component 4A and an inductor component 4B is electrically connected between the interstage coupling element 3 and between the input end 1 and one end of the first series body 4. Is connected to the input coupling element 8, and one end of the second series body 5 composed of the capacitor component 5 A and the inductor component 5 B is electrically connected between the output terminal 2 and the interstage coupling element 3, and the output terminal 2 and one end of the second series body 5, an output coupling element 9 is connected, and the other end of the first series body 4 is a first parallel body 6 comprising a capacitor component 6A and an inductor component 6B. One end of the second series body 5 is electrically connected to the other end of the second series body 5 and the capacitor component 7A and the inductor component One end of the second parallel body 7 consisting of B is electrically connected, and the other end of the first parallel body 6 and the second parallel body 7 is electrically connected to the ground, A left-handed transmission line was formed on the dielectric layer.

For example, Non-Patent Document 1 is known as prior art document information related to this application.
Sungtec Kahng and Jeong-ho Ju, Left-Handedness based Bandpass Filter Design for RFID UHF-Band applications, IEEE., PP.165〜168 2007 Korea-Japan Microwave Conference

  Such a conventional left-handed filter has a problem that a differential output signal cannot be extracted.

  That is, the conventional left-handed filter has only one output terminal 2 and cannot output a differential output signal.

  Therefore, an object of the present invention is to extract a differential output signal.

  In order to achieve this object, the present invention provides a resonator having an input end and first and second output ends, the first end being provided between the input end and the first output end. The interstage coupling element is interposed, and one end of a first series body including a capacitor component and an inductor component is electrically connected between the input end and the interstage coupling element, and the first series An input coupling element is electrically connected between one end of the body and the input terminal, and a second series comprising a capacitor component and an inductor component is disposed between the first output terminal and the interstage coupling element. One end of the body is electrically connected, a first output coupling element is electrically connected between one end of the second series body and the output end, and the other end of the first series body is connected to the other end of the first series body. Is electrically connected to one end of a first parallel body composed of a capacitor component and an inductor component. One end of a second parallel body composed of a capacitor component and an inductor component is electrically connected to the other end of the series body, and a third portion composed of a capacitor component and an inductor component is connected to the other end of the first series body. One end of the series body is electrically connected, and the other end of the second series body is electrically connected to one end of a fourth series body composed of a capacitor component and an inductor component, and the third series body One end of a third parallel body composed of a capacitor component and an inductor component is electrically connected to the other end of the body, and a fourth terminal composed of a capacitor component and an inductor component is connected to the other end of the fourth series body. One end of the parallel body is electrically connected, the other end of the first, second, third, and fourth parallel bodies is electrically connected to the ground, and the other end of the third series body and the fourth A second inter-stage coupling element is interposed between the other end of the series body of Serial other end of fourth series body is obtained by the left-handed filter is electrically connected to said second output terminal via a second output coupling element.

  With this configuration, the number of cells constituting the CRLH resonator is 2, so that 0th-order and −1st-order left-handed resonances occur, and as a result, when signals are extracted differentially, they vibrate at the same potential. The zeroth-order resonance cancels out, and only the first-order resonance that vibrates so that the amplitude of the potential is opposite in phase at both ends of the resonator can be extracted.

(Embodiment 1)
Hereinafter, the left-handed filter according to Embodiment 1 of the present invention will be described with reference to the drawings.

  First, the concept of “cell” used in the present invention will be described with reference to FIG.

  As shown in FIG. 1, the unit cell 10 includes a series body 11 composed of a capacitor component 11A and an inductor component 11B, and a parallel body 12 composed of a capacitor component 12A and an inductor component 12B connected to one end of the series body. Composed. The front-rear relationship between the capacitor component 11A and the inductor component 11B may be reversed.

  This unit cell 10 is a minimum unit structure of a right-handed / left-handed composite line called a metamaterial.

  Next, this metamaterial will be described.

  Usually, a substance existing in the natural world has a positive dielectric constant and a positive magnetic permeability, and this is called a right-handed medium. Here, the “right hand system” means that the three directions of the electric field direction, the magnetic field direction, and the wave traveling direction (phase propagation direction) of the electromagnetic wave are in the positional relationship of the right hand thumb, index finger, and middle finger.

  On the other hand, a medium in which both the dielectric constant and the magnetic permeability are simultaneously negative is called a left-handed material or metamaterial. Here, the “left-handed system” means that the three directions of the electromagnetic field direction, the magnetic field direction, and the wave traveling direction (phase propagation direction) are in the positional relationship of the thumb, index finger, and middle finger of the left hand.

  Until now, the existence of a substance having only a negative dielectric constant or a substance having only a negative magnetic permeability has been discovered. For example, the former is plasma, and the latter is ferrite. However, no substance has been found in nature where both permittivity and permeability are negative at the same time. Therefore, such a medium is created by artificially making a fine structure and making the apparent dielectric constant and permeability negative. This is called an artificial medium.

  Next, the operation principle of the transmission line type metamaterial will be described.

  As shown in FIG. 2, the electrical characteristics of a normal right-handed transmission line can be considered as an equivalent circuit in which an infinite number of infinitesimal sections consisting of a series inductor component 11B and parallel capacitor components 12A are connected. This structure is called a pure right-handed transmission line (PRH TL).

  On the other hand, as shown in FIG. 3, the electrical characteristics of the left-handed transmission line can be considered as an equivalent circuit in which an infinite number of infinitesimal sections composed of a series capacitor component 11A and a parallel inductor component 12B are connected. it can. This structure is called a pure left-handed transmission line (PLH TL).

  However, when the series capacitor component 11A as shown in FIG. 3 is made, since it has a physical volume, a right-handed series inductor component 11B as shown in FIG. 2 is inevitably generated as a parasitic component. It becomes.

  Further, when trying to make a parallel inductor 12B as shown in FIG. 3, since it has a physical volume, a right-handed parallel capacitor component 12A as shown in FIG. 2 is inevitably generated as a parasitic component. Become.

  Therefore, the metamaterial of an artificial medium that can be actually realized is a composite composed of a right-handed parallel capacitor component 12A and a series inductor component 11B, a left-handed series capacitor component 11A, and a parallel inductor component 12B as shown in FIG. It is a right-handed / left-handed transmission line (CRLH TL).

This CRLH transmission line has both left-handed and right-handed properties. It has a right-handed nature in the high frequency region and a left-handed nature in the low frequency region. The series body 11 including the left-handed capacitor component 11A (C _L ) and the right-handed inductor component 11B (L _R ) shown in FIG. 1 resonates at an angular frequency ω _se = 1 / (C _L ^* L _R ). The parallel body 12 composed of the left-handed inductor component 12B (L _L ) and the right-handed capacitor component 12A (C _R ) is anti-resonant at the angular frequency ω _sh = 1 / (L _L ^* C _R ). It becomes a parallel resonant circuit that resonates. Here, the case of ω _se = ω _sh is called a balance case, and the right-handed frequency region and the left-handed frequency region are continuously connected. On the other hand, the case of ω _se ≠ ω _sh is referred to as an unbalanced case, and a gap is generated between the right-handed frequency region and the left-handed frequency region, and an attenuation band in which electromagnetic waves cannot propagate is generated in that region.

  When a small gap or the like is formed at the input / output end of the CRLH transmission line to form an input / output coupling capacitor, the CRLH operates as a resonator in the same manner as a right-handed finite length line. In the right-handed finite-length line resonator, the lowest-order resonance having a half wavelength and the resonance of a harmonic that is an integer multiple thereof are recognized. On the other hand, in the CRLH resonator, the number of unique resonance frequencies is determined by the number of cells. For example, as shown in FIG. 10, a CRLH resonator in which seven unit cells 10 are connected and sandwiched between capacitors 81 and 82 and the number of cells is n = 7 is a standing wave having a half wavelength as shown in FIG. From the + first order resonance to the + 6th order resonance exists as a right-handed resonance. Further, as the resonance of the backward wave, the resonance of the left-handed system exists from the minus first-order resonance to the standing wave of the half wavelength. Furthermore, there is a zero-order mode in which all cells vibrate synchronously at the same potential. As shown in FIG. 9, no standing wave is generated in the 0th-order mode, but this mode can be considered as a special resonance mode having an infinite wavelength.

  In the CRLH resonator, the + 1st order and −1st order resonance modes are the same as the standing wave distribution as shown in FIG. 9, and the absolute velocity of the phase velocity of the forward wave of the right hand system and the backward wave of the left hand system is shown. Since the value is the same at a lower frequency in the left-handed system, the left-handed resonant frequency is necessarily lower.

  The high-pass characteristic of the CRLH transmission line is effective at frequencies lower than the sixth order, and a left-handed gap that cannot be propagated at lower frequencies. Further, the low-pass characteristic of the CRLH transmission line is effective at frequencies higher than the + 6th order, resulting in a right-handed gap that cannot propagate at higher frequencies. Therefore, the CRLH resonator exhibits a very wide band-pass characteristic including a low-frequency left-handed region to a high-frequency right-handed region. What is intended to be used in the present invention is not such a broadband bandpass characteristic including both the left-handed system and the right-handed system. The present invention is an ultra-compact bandpass left-handed filter that uses the resonance phenomenon of the left-handed system.

  In order to construct a bandpass left-handed filter having a desired bandwidth using left-handed resonance, it is necessary to collect a plurality of specific left-handed resonance modes to form a bandpass characteristic. . Therefore, in the configuration of the present invention, a multistage left-handed filter having a plurality of resonators is configured using interstage coupling elements.

  Here, it should be noted that each resonance mode corresponds to the number of discrete standing waves even if, for example, adjacent −1st order and −2nd order resonance modes are used in a single-stage resonator. This is because the passband is very narrow because it can only have a separated resonant frequency with a specific frequency interval, and the damping characteristic cannot be controlled.

  For example, when a two-stage left-handed filter is configured using an interstage coupling element with respect to the pass band, the pass band may be formed using the resonance modes of the respective resonators as shown in FIG. it can. At that time, by controlling the size of the interstage coupling element and the input / output coupling element, the desired bandwidth and passband characteristics can be formed. Furthermore, since the present invention uses the −1st order resonance, it is possible to extract signals in a differential manner, and a balanced / unbalanced filter can be created.

  For example, when a two-stage left-handed filter is configured for attenuation characteristics, the input coupling element and the interstage coupling element are connected to the same terminal of the resonator as shown in FIG. 7, and the output coupling element and the interstage coupling element are connected. An attenuation pole can be provided by connecting to the same terminal of another resonator. At that time, by controlling the element value of the series resonance circuit or the parallel resonance circuit of the resonator, the attenuation pole can be arranged at a desired frequency, and a good attenuation characteristic can be obtained. Furthermore, since the present invention extracts signals differentially, the 0th order oscillating at the same potential is not output, and a good attenuation characteristic can be ensured over a wide band. These points are features of the present invention.

  Here, FIG. 4 shows a left-handed filter in the present embodiment.

  As shown in FIG. 4, the left-handed filter in the present embodiment is a filter having an input end 15, a first output end 16A, and a second output end 16B, and the input end 15 and the first output end. Between the input terminal 15 and the interstage coupling element 19A, one end of the first series body 11 including the capacitor component 11A and the inductor component 11B is connected. 17, and one end of the second series body 110 including the capacitor 110 </ b> A and the inductor component 110 </ b> B is electrically connected at the connection point 18 between the first output terminal 16 </ b> A and the interstage coupling element 19 </ b> A. One end of the first series body 11 is electrically connected to one end of the first series body 11, and one end of the first parallel body 12 including the capacitor component 12A and the inductor component 12B is electrically connected to one end of the second series body 110. Completion One end of the second parallel body 120 composed of 120A and the inductor component 120B is electrically connected, and the other end of the first parallel body 12 is electrically connected to the ground. The other end is electrically connected to the ground, and the first series body 11 and the first parallel body 12 constitute the first cell 10A, and the second series body 110 and the second parallel body 120. Thus, the second cell 100A is configured.

  Further, the other end of the first series body 11 is connected to one end of a third series body 13 composed of a capacitor component 13A and an inductor component 13B, and the other end of the second series body 110 is connected to a capacitor component 130A and an inductor component. One end of the fourth series body 130 consisting of 130B is connected to one end of the third parallel body 14 consisting of the capacitor component 14A and the inductor component 14B. One end of the fourth series body 130 is electrically connected to one end of the fourth parallel body 140 composed of the capacitor component 140A and the inductor component 140B, and the other end of the third parallel body 14 is electrically connected to the ground. The other end of the fourth parallel body 140 is electrically connected to the ground, and the third series body 13 and the third parallel body 14 constitute the third cell 10B. Constitute a fourth cell 100B by a fourth series body 130 and fourth parallel body 140.

  Further, the input coupling element 20 is provided between the interstage coupling element 19A and the input terminal 15, the output coupling element 21A is provided between the interstage coupling element 19A and the first output terminal 16A, and the third cell 10B. An interstage coupling element 19B is interposed between the other end of the fourth cell 100B and the other end of the fourth cell 100B, and an output coupling element 21B is interposed between the other end of the fourth cell 100B and the second output end 16B. The configuration is to let

  With such a configuration, the number of cells constituting the CRLH resonator is two, so that the 0th-order and −1st-order left-handed resonance occurs, and as a result, when the signal is extracted differentially, the same potential is obtained. The oscillating zeroth-order resonance cancels out, and only the −1st-order resonance that vibrates so that the amplitude of the potential is opposite in phase at both ends of the resonator can be taken out.

  In addition, when the first CRLH resonator 22 composed of the unit cells 10A and 10B and the second CRLH resonator 23 composed of the unit cells 100A and 100B are electromagnetically coupled to each other, the interstage coupling elements 19A and 19B And the first CRLH resonator 22 and the second CRLH resonator 23, which are electromagnetically coupled, form an equivalent parallel resonance circuit, so that the impedance of the filter viewed from the input side or the output side becomes 0 and the signal As a result, there is a frequency that flows to the ground, so that one pole can be increased in the pass band, and as a result, the attenuation characteristic can be improved.

  Further, by adjusting the capacitance values of the input coupling element 20, the interstage coupling elements 19A and 19B, and the output coupling elements 21A and 21B, the coupling of the −1st order resonance of the two CRLH resonators 22 and 23 can be easily controlled. Therefore, a left-handed filter in which a pass band is formed by −1st order resonance can be formed, and an attenuation pole generated by the electromagnetic coupling of the CRLH resonators 22 and 23 and the interstage coupling element 15 is arranged. -Since it can be controlled, it is possible to provide a left-handed filter having better filter characteristics than a conventional two-stage left-handed filter.

  The input coupling element 20, the interstage coupling elements 19A and 19B, and the output coupling elements 21A and 21B may be configured by inductors instead of capacitors.

  A specific structure is shown in FIG.

  In the structure in which the space between the ground conductors 24 and 25 arranged to face each other is filled with the dielectric 26, the conductor pattern 27 corresponds to the inductor 11B shown in FIG. The conductor pattern 27 and the conductor pattern 28 are configured to be sandwiched between conductor patterns 30 and 31 connected via via conductors 29. Thus, the capacitor 11A shown in FIG. 4 is configured. The conductor pattern 28 is connected to the ground conductor 25 via the via conductor 32. This corresponds to the inductor 12B shown in FIG. Furthermore, the conductor pattern 28 includes the ground conductors 24 and 25 to constitute the capacitor 12A shown in FIG. The above corresponds to the unit cell 10A shown in FIG.

  The conductor pattern 28 also corresponds to the inductor 13B shown in FIG. The conductor pattern 28 and the conductor pattern 33 are configured to be sandwiched between conductor patterns 35 and 36 connected via via conductors 34. Thereby, the capacitor 13A shown in FIG. 4 is configured. The conductor pattern 33 is connected to the ground conductor 25 via the via conductor 37. Thus, the inductor 14B shown in FIG. 4 is configured. Further, the conductor pattern 33 and the ground conductors 24 and 25 constitute the capacitor 14A shown in FIG. The above corresponds to the unit cell 10B shown in FIG.

  The unit cells 10A and 10B form a first CRLH resonator 22.

  The first CRLH resonator 22 and the first CRLH resonator 23 shown in FIG. 4 are configured to be mirror-symmetric with respect to the line segment AA ′ in FIG. 5, and the conductor pattern 38 is the inductor 110B shown in FIG. Corresponding to The conductor pattern 38 and the conductor pattern 39 are configured to be sandwiched between conductor patterns 41 and 42 connected via the via conductor 40. Thus, the capacitor 110A shown in FIG. 4 is configured. The conductor pattern 39 is connected to the ground conductor 25 via the via conductor 48. This corresponds to the inductor 120B shown in FIG. Further, in the conductor pattern 39, the capacitor 120A shown in FIG. The above corresponds to the unit cell 100A shown in FIG.

  The conductor pattern 39 also corresponds to the inductor 130B shown in FIG. The conductor pattern 39 and the conductor pattern 47 are configured to be sandwiched between conductor patterns 45 and 46 connected via the via conductor 44. Thereby, the capacitor 130A shown in FIG. 4 is configured. The conductor pattern 47 is connected to the ground conductor 25 via the via conductor 48. Thereby, the inductor 140B shown in FIG. 4 is configured. Furthermore, the conductor pattern 47 and the ground conductors 24 and 25 constitute the capacitor 140A shown in FIG. The above corresponds to the unit cell 100B shown in FIG.

  The unit cells 100A and 100B form a second CRLH resonator 23.

  The input coupling element 20 shown in FIG. 4 includes a conductor pattern 56 connected from the input terminal 54 via the via conductor 55 and a conductor pattern 38 corresponding to the inductor 120B shown in FIG. The interstage coupling element 19A shown in FIG. 4 includes a conductor pattern 27 constituting a part of the unit cell 10A shown in FIG. 4, a conductor pattern 38 and a conductor pattern 52 constituting a part of the unit cell 100A shown in FIG. The interstage coupling element 19B shown in FIG. 4 includes a conductor pattern 33 corresponding to the inductor 14B shown in FIG. 4 and a conductor pattern 47 and a conductor pattern 53 corresponding to the inductor 140B shown in FIG. The output coupling element 21A shown in FIG. 4 includes the conductor pattern 51 connected from the first output terminal 49 via the via conductor 50, and the impedance shown in FIG. The output coupling element 21B shown in FIG. 4 includes the conductor pattern 59 connected to the second output terminal 57 via the via conductor 58 and the conductor pattern 27 corresponding to the ductor 12B. This is expressed by a conductor pattern 47 corresponding to the inductor 140B.

  The first CRLH resonator 22 and the second CRLH resonator 23 can be electromagnetically coupled to each other by being incorporated in the dielectric 26 as in the present embodiment. In that case, a new attenuation pole can be provided as shown in FIG. 9 due to the electromagnetic field coupling and the resonance of the interstage coupling element 19, and the attenuation characteristic can be improved.

  At this time, the ground conductors 24 and 25 are preferably connected by the side electrodes 60 and 61.

  In addition, although the input coupling element 20 and the output coupling elements 21A and 21B are expressed as capacitors as shown in FIG. 4 this time, when each capacitance is 10 pF or more, the input coupling element 20 and the output coupling elements 21A and 21B are It can be removed and connected directly.

  The left-handed filter of the present invention has an effect that the attenuation characteristic can be improved, and is useful in various electronic devices such as a mobile phone.

Equivalent circuit diagram showing a unit cell in the left-handed filter according to the first and second embodiments of the present invention. Equivalent circuit diagram of right-handed transmission line in left-handed filter shown in Embodiment 1 of the present invention Equivalent circuit diagram of left-handed transmission line in left-handed filter shown in Embodiment 1 of the present invention FIG. 3 is an equivalent circuit diagram showing the left-handed filter according to the first embodiment of the present invention. 1 is an exploded perspective view showing the structure of a left-handed filter according to Embodiment 1 of the present invention. Frequency characteristic diagram of left-handed filter shown in Embodiment 1 of the present invention Frequency characteristic diagram of left-handed filter shown in Embodiment 1 of the present invention Frequency characteristic diagram of CRLH resonator in left-handed filter shown in Embodiment 1 of the present invention The characteristic figure which shows the voltage standing wave of the CRLH resonator in the left-handed filter shown in Embodiment 1 of this invention The perspective view of the CRLH resonator in the left-handed filter shown in Embodiment 1 of the present invention Equivalent circuit diagram of conventional left-handed filter Frequency characteristics of conventional left-handed filter

Explanation of symbols

11 First series body 11A, 12A, 13A, 14A, 110A, 120A, 130A, 140A Capacitor component 11B, 12B, 13B, 14B, 110B, 120B, 130B, 140B Inductor component 12 First parallel body 13 Third Series body 14 Third parallel body 15 Input end 16A First output end 16B Second output end 19A First inter-stage coupling element 19B Second inter-stage coupling element 20 Input coupling element 21A First output coupling element 21B 2nd output coupling element 110 2nd serial body 120 2nd parallel body 130 4th serial body 140 4th parallel body

Claims (3)

A resonator having an input end and first and second output ends,
A first interstage coupling element is interposed between the input terminal and the first output terminal,
One end of a first series body composed of a capacitor component and an inductor component is electrically connected between the input end and the interstage coupling element,
An input coupling element is electrically connected between one end of the first series body and the input end,
One end of a second series body composed of a capacitor component and an inductor component is electrically connected between the first output end and the interstage coupling element,
A first output coupling element is electrically connected between one end of the second series body and the output end,
One end of a first parallel body composed of a capacitor component and an inductor component is electrically connected to the other end of the first series body,
One end of a second parallel body comprising a capacitor component and an inductor component is electrically connected to the other end of the second series body,
One end of a third series body composed of a capacitor component and an inductor component is electrically connected to the other end of the first series body,
One end of a fourth series body composed of a capacitor component and an inductor component is electrically connected to the other end of the second series body,
One end of a third parallel body comprising a capacitor component and an inductor component is electrically connected to the other end of the third series body,
One end of a fourth parallel body comprising a capacitor component and an inductor component is electrically connected to the other end of the fourth series body,
The other ends of the first, second, third, and fourth parallel bodies are electrically connected to the ground,
A second interstage coupling element is interposed between the other end of the third series body and the other end of the fourth series body,
A left-handed filter in which the other end of the fourth series body is electrically connected to the second output end via a second output coupling element. A first cell comprising the first series body and the first parallel body;
A first resonator comprising a second cell comprising the second series body and the second parallel body;
A third cell comprising the third series body and the third parallel body;
A second resonator composed of a fourth cell composed of the fourth series body and the fourth parallel body;
The left-handed filter according to claim 1, which is electromagnetically coupled. The left-handed filter according to claim 1, wherein the first resonator and the second resonator are built in a dielectric.

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