JP2012191530A - Differential transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a structure of a left-hand system differential transmission line, for miniaturizing and reducing thickness, so that a common mode filter that uses the left-hand system differential transmission line is adapted to a radio communication apparatus.SOLUTION: A common mode filter is realized which is adaptive to an integrated circuit technology by using a structure that utilizes a flat conductor pattern, for constituting a D-CRLH (dual type right hand/left hand compound) differential transmission line. The left-hand system differential transmission line is a differential transmission line comprising a first transmission line L1 and a second transmission line L2. The first transmission line L1 comprises an A pattern part L1A, a B pattern part L1B, and a C pattern part L1C. The second transmission line L2 comprises, as with the first transmission line L1, an A pattern part L2A, a B pattern part L2B, and a C pattern part L2C. The transmission line has the structure as a basic structure (unit cell), and solves a problem by utilizing a differential transmission line in which a plurality of unit cells are connected in cascade arrangement.

Description

  The present invention relates to a transmission line that passes or blocks electrical signals.

  A communication line excellent in EMC (electromagnetic environment compatibility) by propagating a differential signal (differential mode) between two transmission lines in a differential transmission line in which two transmission lines are arranged symmetrically in parallel. Can be configured. In this differential transmission line, if an in-phase component (common mode) that becomes noise propagates, an electromagnetic wave is leaked to the surroundings to have an adverse effect. Therefore, a common mode filter is required to suppress the common mode component.

  In recent communication devices, communication standards such as USB and HDMI for high-speed data communication are widespread, and these are high-speed serial communication systems using a differential transmission system.

  Although the differential transmission method is excellent in EMC characteristics, the common mode filter is an essential component because the common mode component generated in the signal source causes noise radiation.

  Furthermore, recent EMC-related research has revealed not only EMC problems from signal cables, but also EMC problems between parts due to transmission lines on the board or in the IC, which cannot be solved with commercially available common mode chokes and chip parts. Noise suppression in the vicinity of the noise source is a problem.

  Conventional common mode filters such as common mode choke coils and common mode filters using chip elements are generally known, and a wide variety of common mode filters have been developed depending on the size and size of the applied frequency band. .

  The operation principle of the common mode filter generally uses the mutual coupling between two transmission lines, and in particular, utilizes the difference between the differential mode and the common mode impedance using the mutual inductance M in many cases. . However, the difference in impedance between the differential mode and the common mode is that sufficient characteristics cannot be obtained depending on the frequency band used.

  Further, since the common mode choke coil and the common mode filter using the chip element are based on the operation based on the lumped constant circuit theory, satisfactory design cannot be performed in a high frequency band where the transmission line is handled as a distributed constant circuit. These common mode filters are required to be devised so as not to affect the design by reducing the parasitic capacitance and the parasitic inductance as a distributed constant circuit as much as possible, or to have a complicated design in consideration of the generated parasitic components.

  In either case, if a sufficient difference in impedance between the two modes cannot be obtained, the filter does not function as a common mode filter.

  Further, the above-described conventional common mode filter has a three-dimensional structure, and even a small chip component has a thickness of a sub-mm order component, so that there is a demand for a communication device that requires a reduction in size and thickness. It is difficult to meet

  On the other hand, in recent years, many have been invented, which are called left-handed devices or metamaterials, etc., which operate as negative values of the magnetic permeability and dielectric constant of substances.

  Left-handed transmission lines have no material with negative values of permeability and permittivity, so inductive (lagging phase) elements and capacitive (leading phase) elements are interchanged in the electrical equivalent circuit of transmission lines. What is realized by configuring a circuit is the mainstream. In this case, since the existing inductive element has parasitic capacitance and the capacitive element has parasitic induction, what is called a right-hand / left-handed composite (hereinafter abbreviated as CRLH) transmission line in consideration of these parasitic components, It is realized as a left-handed device (see Non-Patent Document 1).

  However, the CRLH transmission line has a problem that a direct current component cannot be transmitted because a capacitive element is arranged in a series element of the transmission line.

  On the other hand, what is called a dual-type right-hand / left-handed composite (D-CRLH) transmission line has been proposed and is known as a left-handed transmission line that can also transmit a DC component (see Non-Patent Document 2). However, since it is a pair of signal lines and ground lines, there is a problem of radiation of unnecessary noise as a transmission line used at high frequencies.

  The transmission line used for communication has a low noise emission and is less affected by external noise (in order to improve EMC performance). Dynamic transmission lines are mainstream. However, in the differential transmission line, a common (common mode) mode component causes noise and the like, so a common mode filter is required, and a separate common mode filter needs to be loaded.

  Also in the left-handed transmission line, a differential transmission line has been invented to improve EMC performance. In this case, a DC signal is transmitted because the two right-handed / left-handed composite transmission lines are arranged symmetrically. It has a problem that it cannot be performed (see Non-Patent Document 3). Transmission of a DC signal is necessary for the purpose of power supply.

  In the CRLH differential transmission line including the D-CRLH differential transmission line, the common mode noise component cannot be propagated in principle in the frequency band where the differential transmission signal has the left-handed transmission characteristic. It functions as a mode filter (see Non-Patent Document 4).

  In addition, the D-CRLH differential transmission line compensates for the disadvantage that the DC component is not conducted in the conventional left-handed transmission line and has the advantage of being able to transmit a DC signal, so the high-frequency data signal and the DC power supply are the same. It can also be realized on the track.

  In addition, since this structure is a technology realized by a transmission line pattern, it is compatible with the IC process and can be built in the IC chip in the future. Therefore, it is considered to be an effective technique for noise suppression inside the IC described above.

  Based on conventional research, the basic operation of the common mode filter function of the D-CRLH differential transmission line has been demonstrated by trial manufacture and evaluation of devices (see Non-Patent Document 4).

  However, the left-handed operating frequency band that operates as a common mode filter is narrow, the operating frequency band does not correspond to the frequency standards of practical equipment, high frequency or low frequency is required, and signal in the same frequency band The differential (differential) mode has a small transmission coefficient and a large loss.

  The present invention proposes a structure of a common mode filter that satisfies the requirements for miniaturization and thickness reduction of a common mode filter required from communication equipment and satisfies practical performance, and solves the above technical problem.

C. Caloz and T. Itoh: "Application of the Transmission Line Theory of Left-Handed (LH) Materials to the Realization of a Microstrip LH Transmission Line", in Proc.IEEE-AP-S USNC / URSI National Radio Science Meeting, l. 2, pp.412-415 (2002) C. Caloz: "Dual Composite Right / Left-Handed (D-CRLH) Transmission Line Metamaterial", IEEE Microwave Wireless Components Letters, Vol. 16, Issue 11, pp.585-587 (2006) R. Goto, H. Deguchi and M. Tsuji: "Composite Right / Left- Handed Transmission Lines Based on Conductor-Backed Coplanar Strips," IEICE Trans. Electron., Vol. E89-C, No. 9, pp.1306- 1311 (2006) H. Nakayama, K. Fujisawa and T. Itoh: "Fabrication and Estimation of Dual Composite Right / Left Handed Differential Transmission Line", The Papers of Technical Meeting on Magnetics, IEE Japan, MAG-08-195, pp.21-26 (2008)

  Based on the requirements for the common mode filter described above and the problems of the conventional common mode filter, several device structures that solve the technical problems in the small and thin common mode filter are proposed.

  The problems to be solved are small and thin, adjusting the frequency (particularly lowering the frequency) in order to make the common mode operating frequency band compatible with the practical frequency band, widening the operating frequency band, It is an object to reduce the loss of the differential mode in the frequency band, increase the transmission coefficient, and reduce the common mode transmission coefficient.

  The present invention proposes a structure for improving the characteristics of a device structure constituting a D-CRLH differential transmission line, which is adapted to miniaturization and thinning.

  In order to achieve the above object, the transmission line according to the present invention solves the problem with the following device structure.

  A transmission line according to the present invention includes a pair of input / output circuits each forming a series impedance between input and output including an element having a first delayed phase and an element having a first leading phase connected in parallel to each other A second delay phase element and a second lead phase element connected in series between the component and the pair of input / output circuit components, and the pair of transmission lines and the ground potential And a shunt circuit component that constitutes a shunt admittance including elements having a third lead phase respectively connected therebetween.

  According to this differential transmission line, in the circuit component between the pair of input and output constituting the series impedance, a DC path is secured because of the first delayed phase connected in parallel, and the shunt admittance is formed. In the circuit component, the DC shunt is interrupted by the element having the second leading phase connected in series and the element having the third leading phase, so that the DC transmission is performed between the input and output of the transmission line. Is possible.

  Also, in differential mode transmission, the parallel resonance frequency of the pair of input and output circuit components constituting the series impedance and the series resonance frequency of the shunt circuit component constituting the shunt admittance are designed to be lower than the operating frequency. As a result, in a frequency band exceeding these resonance frequencies, the series impedance operates as capacitive and the shunt admittance operates as inductive, and thus operates as a left-handed transmission line.

  On the other hand, in common mode transmission, the phase of the pair of input and output circuit components that make up the two signal lines have the same potential, so the shunt circuit components that make up the shunt admittance are connected in series. The element having the second delay phase and the element having the second lead phase that have been made do not function, and only the element having the third lead phase connected between the transmission line and the ground potential becomes a shunt. . For this reason, since both the series impedance part and the shunt admittance part operate as a capacitive load having a leading phase, the signal is not propagated and functions as a common mode filter.

  In particular, the present invention includes a pair of conductor patterns extending in the input / output direction and parallel to each other, and a ground conductor that is adjacent to the pair of conductor patterns. Thus, according to the differential transmission line having the pair of conductor patterns extending in the input / output direction and parallel to each other and the ground conductor adjacent to the pair of conductor patterns, the differential transmission line extends in the input / output direction. Since a plurality of the above-described differential transmission line structures are connected by the line, the functions as a common mode filter are integrated and a large filter effect can be obtained.

  In this case, the pair of conductor patterns respectively includes an input side pattern portion disposed on the input side in the input / output direction, an output side pattern portion disposed on the output side in the input / output direction, and the input side It is preferable to have an intermediate connection pattern portion that is formed narrower in the direction perpendicular to the input / output direction than the pattern portion and the output side pattern portion, and connects the input side pattern portion and the output side pattern portion. According to this, the intermediate connection pattern portion constitutes an element having a first delay phase, and the gap region between the input side pattern portion and the output side pattern portion has an element having a first advance phase. Configure.

  Further, between the pair of conductor patterns, the input-side gap region in which the input-side pattern portions are arranged to face both sides in the parallel direction and the output-side pattern portion are arranged to face both sides in the parallel direction. And an output side gap region is preferably provided. According to this, the input side gap region and the output side gap region constitute an element having the second lead phase of the shunt circuit component that constitutes the shunt admittance, respectively.

  Here, the element having the first delay phase and the element having the first lead element constituting the series impedance are such that the input side pattern portion and the output side pattern portion are interposed via the intermediate connection pattern portion. The pattern structure is connected in the input / output direction. Further, the element having the second delay phase and the element having the second lead phase constituting the shunt admittance are the input side pattern portion and the output side pattern portion of the pair of conductor patterns, The structure in which the input side pattern portions belonging to each of the pair of conductor patterns face each other through the gap in the parallel direction, and the output side pattern portions belonging to the pair of conductor patterns through the gap in the parallel direction It is comprised by the structure which opposes.

  In this case, since the differential transmission line is constituted by a conductor pattern, it can be realized by a laminated structure of a planar pattern, so that it can be adapted to a thin film process and the device can be thinned. Further, the thin film process is suitable for microfabrication, and the device can be miniaturized by miniaturizing the pattern. Furthermore, since the differential transmission line can be realized by a simple conductor pattern configuration, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In the present invention, the input side pattern portion of the pair of conductor patterns protrudes from the main body portion toward the other input side pattern portion and the other input side pattern portion, and is narrower in the input / output direction than the main body portion. A protrusion portion having a width, and tips of the protrusion portions are opposed to each other in the parallel direction via the input-side gap region, and the output-side pattern portion is connected to the main body portion and the other output-side pattern. Projecting from the main body part toward the part, and having a narrower projecting part in the input / output direction than the main body part, the tips of the projecting parts are opposed to the parallel direction via the output-side gap region It is preferable to do. According to this, by having the narrow projecting portion, it is possible to adjust and particularly increase the inductance component that is an element having the second delayed phase of the shunt admittance. As a result, the resonance frequency of the shunt admittance can be adjusted, and in particular, the frequency can be lowered. Further, since the narrow protrusion mainly constitutes an element having the second delayed phase of the shunt admittance, it can be designed independently of the element having the second leading phase, so that the shunt admittance The design for adjusting the resonance frequency of is easy.

  In addition to this, it is preferable that the protrusion is formed in a T-shape with a tip extended in the input / output direction. According to this, since the projecting portion is formed in a T shape, the element having the second delay phase of the shunt admittance and the element having the second lead phase are designed independently. Therefore, the design for adjusting the resonance frequency of the shunt admittance is further facilitated.

  In the present invention, the pair of conductor patterns are preferably laminated with the ground conductor via an insulating layer. According to this, the differential transmission line realized by the laminated structure has a small planar exclusive area, and thus can be miniaturized. Further, since the element having a delayed phase formed in the gap portion is formed not by the gap on the same plane but by the gap between the laminated conductors, a large capacitance can be realized. As a result, the series impedance and the resonant frequency of the shunt admittance can be adjusted, and in particular, the frequency can be lowered.

  In the present invention, the pair of conductor patterns are preferably formed on the same plane. According to this, since a differential transmission line having a structure in which a conductor pattern is formed on the same plane can form a device with a single conductor layer, the manufacturing process is simplified and the manufacturing cost can be reduced.

  In the present invention, it is preferable that the pair of conductor patterns are laminated on each other via an insulating layer. According to this, the differential transmission line realized by the laminated structure has a small planar exclusive area, and thus can be miniaturized. Further, since the element having a delayed phase formed in the gap portion is formed not by the gap on the same plane but by the gap between the laminated conductors, a large capacitance can be realized. As a result, the series impedance and the resonant frequency of the shunt admittance can be adjusted, and in particular, the frequency can be lowered.

1 is a structural diagram showing a configuration of a left-handed differential transmission line according to Embodiment 1 of the present invention. It is a circuit diagram which shows the structure of the left-handed differential transmission line which concerns on Embodiment 1 of this invention. It is a structural diagram which shows the structure of the left-handed differential transmission line which concerns on Embodiment 2 of this invention. It is a structural diagram which shows the structure of the left hand type | system | group differential transmission line which concerns on Embodiment 3 of this invention. It is a structural diagram which shows the structure of the left-handed differential transmission line which concerns on Embodiment 4 of this invention. It is a structural diagram which shows the structure of the left-handed differential transmission line which concerns on Embodiment 5 of this invention. It is a bird's-eye view of the structure which shows the structure of the left-handed differential transmission line which concerns on Embodiment 6 of this invention. It is a top view of the conductor line pattern of the structure which shows the structure of the left-handed differential transmission line which concerns on Embodiment 6 of this invention. It is a bird's-eye view of the structure where three unit cells were cascade-connected about the structure of the left-handed system differential transmission line which concerns on Embodiment 6 of this invention. As a result of performing a characteristic simulation using a three-dimensional electromagnetic field analysis on a device in which three unit cells of FIG. 9 according to the sixth embodiment of the present invention are connected in cascade, a differential (differential signal) mode and a common (in-phase) This is a comparison of the frequency characteristics of the magnitude of the transmission coefficient of the (noise) mode. As a result of measuring the transmission characteristics of the prototype device with respect to a device in which three unit cells of FIG. 9 according to Embodiment 6 of the present invention are connected in cascade, the differential (differential signal) mode and the common (common mode noise) mode are measured. This is a comparison of the frequency characteristics of the transmission coefficient. As a result of measuring the transmission characteristics of the prototype device for a device in which three unit cells of FIG. 9 according to the sixth embodiment of the present invention are connected in cascade, the frequency characteristics of the phase of the transmission coefficient in the differential (differential signal) mode Is shown.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Embodiment 1
1 is a structural diagram showing the configuration of a left-handed differential transmission line according to Embodiment 1 of the present invention. 2 is an equivalent circuit diagram of the left-handed differential transmission line having the structure of FIG. 1 according to Embodiment 1 of the present invention. The left-handed differential transmission line in FIG. 1 has a structure using a planar conductor such as a printed circuit board. A microstrip line type in which ground is arranged on the lower surface of the plane line of FIG. 1 via an insulating layer, a strip line type in which ground is arranged on both upper and lower sides via an insulating layer, and the same plane. A coplanar line type with a ground can also be configured.

  The transmission line of this structure can be realized by using a printed circuit board manufacturing technique or an IC manufacturing technique. Generally, it is produced based on a photolithography technique. The transmission line of this structure operates by propagation of an electromagnetic field generated in the electromagnetic field propagation medium between the conductor pattern and the ground. The electromagnetic field propagation medium may be a simple insulating material, but the wavelength of the electromagnetic wave is shortened by using a material having a high dielectric constant or a material having a high magnetic permeability. In addition, the insertion loss of the device can be reduced by using a low-loss material. The material constituting the conductor and ground can reduce the insertion loss of the device by selecting a material having high conductivity.

  The left-handed differential transmission line in FIG. 1 is a differential transmission line composed of a first transmission line L1 and a second transmission line L2. The first transmission line L1 includes an A pattern portion L1A corresponding to the input side pattern portion, a B pattern portion L1B corresponding to the output side pattern portion, and a C pattern portion L1C corresponding to the intermediate connection pattern portion. Similarly to the first transmission line L1, the second transmission line L2 includes an A pattern portion L2A, a B pattern portion L2B, and a C pattern portion L2C. The transmission line has this structure as a basic structure (unit cell), and a plurality of these are connected in cascade to form a transmission line. In addition, it is preferable that the length of this structure (unit cell) is sufficiently smaller than the quarter length of the electromagnetic wave wavelength of the frequency to be used.

  The A pattern portions L1A and L2A are rectangular patterns having a width wa and a length la, and the B pattern portions L1B and L2B are rectangular patterns having a width wb and a length lb. The C pattern portions L1C and L2C are band-like patterns having a width wc and a length lc that connect the A pattern portion and the B pattern portion. Here, wc <wa and wc <wb, and wa = wb in the illustrated example. The inner side of the C pattern portion is arranged away from the inner sides of the A pattern portion and the B pattern portion by a distance dc. From the symmetry of the first transmission line L1 and the second transmission line L2, the A pattern part, the B pattern part, and the C pattern part are respectively lines with respect to the center lines of the first transmission line and the second transmission line. Symmetry is preferred. An input-side gap region having a constant gap width da as viewed in the input / output direction is provided between the A pattern portions L1A and L2A, and a fixed amount when viewed in the input / output direction is provided between the B pattern portions L1B and L2B. An output-side gap region having a gap width db is provided.

  The left-handed differential transmission line in FIG. 1 is represented by the equivalent circuit in FIG. The main correspondence between the structure of FIG. 1 and the equivalent circuit of FIG. 2 is as follows. The A pattern portions L1A and L2A in FIG. 1 correspond to the A12 portion surrounded by the dotted line of the equivalent circuit in FIG. 2, and the B pattern portions L1B and L2B in FIG. 1 are surrounded by the dotted line in the equivalent circuit in FIG. Corresponding to the B12 portion, the C pattern portions L1C and L2C in FIG. 1 respectively correspond to the C1 portion and the C2 portion surrounded by the dotted line of the equivalent circuit in FIG.

  A12LL constituting the A12 portion of the equivalent circuit of FIG. 2 is a line inductance component A12LL between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12LL, B12LL constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12LL between the first transmission line L1 and the second transmission line L2 in the B pattern portion. Of these conductor patterns of the A pattern portion and the B pattern portion, these line inductance components are contributed by the conductor pattern inside the position connected to the C pattern portion, and the lengths of wa, wb and dc are the main parameters. Become. A12LL and B12LL contribute as line inductance components of the shunt element and function as circuit elements having a delayed phase of the shunt element in the left-handed frequency band in which the common mode filter operates.

  A12CR constituting the A12 portion of the equivalent circuit of FIG. 2 is a line capacitance component A12CR between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12CR, B12CR constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12CR between the first transmission line L1 and the second transmission line L2 in the B pattern portion. These line-to-line capacitance components are caused by the gap between the first transmission line L1 and the second transmission line L2 in the A pattern portion and the B pattern portion, and the lengths of wa, wb and gap widths da and db. Is the main parameter. A12CR and B12CR contribute as line capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  A1CP and A2CP constituting the A12 portion of the equivalent circuit of FIG. 2 are parasitic capacitance components A1CP and A2CP generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion. . Similar to A1CP and A2CP, B1CP and B2CP constituting the B12 portion of the equivalent circuit of FIG. 2 are parasitics generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the B pattern portion. Capacitance components B1CP and B2CP. These parasitic capacitance components are capacitances between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion and the B pattern portion, and the dimensions of the A pattern portion and the B pattern portion. The distance dd between the transmission line pattern and the ground conductor GND pattern contributes, and the area by wa, la, wb, lb and the length of the distance dd are the main parameters. A1CP, A2CP, B1CP, and B2CP contribute as parasitic capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  C1LR and C2LR constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are inductance components C1LR and C2LR between the A pattern portion and the B pattern portion in the C pattern portion, and the inductances of the C pattern portions L1C and L2C Corresponding to These inductance components are contributed by the size of the C pattern portion, and the lengths of wc and lc are the main parameters. C1LR and C2LR contribute as parallel inductance components of the serial elements of the transmission line, and function as circuit elements having a delay phase of the serial elements in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  C1CL and C2CL constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion, excluding the C pattern portions L1C and L2C. , Corresponding to the capacitance component formed by the gap between the A pattern portion and the B pattern portion. These capacitance components contribute to the size of the gap between the A pattern portion and the B pattern portion, and the lengths of wa, wb, wc and lc are the main parameters. C1CL and C2CL contribute as a parallel capacitance component of the serial element of the transmission line, and function as a circuit element having a leading phase of the serial element in the left-handed frequency band in which the common mode filter operates.

  C1LP and C2LP constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 correspond to inductance components parasitic on the capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion. These inductance components contribute to the dimensions of the A pattern portion and the B pattern portion, and the lengths of wa, wb, la, and lb are the main parameters. C1LP and C2LP contribute as parasitic inductance components of the parallel capacitance of the serial element of the transmission line, and function as circuit elements having a delayed phase of the serial element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  Since the structure of FIG. 1 has a simple pattern shape, the number of dimensional parameter elements when designing a transmission line is small, so that the design can be facilitated. In addition, since the shape is simple, there is an advantage that the size can be easily reduced according to the fine pattern technology of the thin film.

  The operation of the differential transmission line by the equivalent circuit of FIG. 2 will be described below. The left-handed differential transmission line of the equivalent circuit of FIG. 2 based on the structure of the first embodiment of FIG. 1 is composed of two transmission lines L1 and L2, and the signal components are respectively differential signals having opposite phases. To work. Note that the elements C1CL and C2CL in the series impedance C1 and C2 portions are usually composed of capacitance elements and have parasitic inductive components inside, and thus can be delayed phase elements at higher frequencies than the self-resonant frequency due to the parasitic components. By making the resonance frequency sufficiently high, left-handed transmission is realized as a leading phase element. The elements A1CP, A2CP, B1CP, and B2CP between the transmission line and the ground are generally elements having a leading phase, and cause parallel resonance with the capacitances A12CR and B12CR in the shunt admittances A12 and B12. Is made sufficiently higher than the series resonance frequency of the elements A12LL and A12CR and the series resonance frequency of the B12LL and B12CR, thereby realizing left-handed transmission.

  In the DC operation of this transmission line, inductance components C1LR and C2LR having a delayed phase in series impedance elements C1 and C2 serve as a DC path, and capacitance components A12CR and B12CR having a leading phase in shunt admittance elements A12 and B12 are DC. In order to prevent shunting, direct current can be transmitted at the input and output of the transmission line.

  The operation of this transmission line in the low frequency band includes a combination of C1LR and C1CL in the series impedance element C1, a frequency band lower than the parallel resonance frequency by the combination of C2LR and C2CL in the series impedance element C2, and a shunt admittance element A12. Is a frequency band lower than the series resonance frequency due to the combination of A12LL and A12CR and the combination of B12LL and B12CR in the shunt admittance element B12, and the series impedance elements C1 and C2 are equivalently lag elements, shunt admittance elements A12 Since B12 and B12 act equivalently as leading elements, the transmission line has a right-handed transmission characteristic.

  The operation of the transmission line in the high-frequency band is performed in the frequency band higher than the parallel resonance frequency of the combination of C1LR and C1CL in the series impedance element C1, and in the combination of C2LR and C2CL in the series impedance element C2, and A frequency band higher than the series resonance frequency of the combination of A12LL and A12CR and the combination of B12LL and B12CR in the shunt admittance element B12 and lower than the second resonance frequency due to the respective parasitic inductance and capacitance In the band, series impedance elements C1 and C2 are equivalently leading elements, and shunt admittance elements A12 and B12 are equivalently acting as delay elements. It comes to have a left-handed transmission characteristics.

  Further higher than the above frequency band, that is, due to the second self-resonant frequency due to the parasitic inductance components C1LP and C2LP of the series impedance elements C1 and C2, and due to the parasitic capacitance components A12CP and B12CP of the shunt admittance elements A12 and B12 In a frequency band higher than each of the second self-resonant frequencies, the series impedance functions as an equivalent delay element and the shunt admittance functions as an advance element, so that the transmission line has a right-handed transmission characteristic. .

  On the other hand, since the two signal lines have the same potential for the common mode signal, A12LL, A12CR, B12LL, and B12CR do not function among the shunt admittance elements A12 and B12 between them. For this reason, the shunt admittance elements A12 and B12 are only the leading elements of A1CP, A2CP, B1CP, and B2CP, which are parasitic capacitances with the ground conductor GND. Therefore, in the frequency band in which the series impedance elements C1 and C2 function as equivalent advance elements (frequency band having the left-handed transmission characteristics described above), both the series impedance element and the shunt admittance element are advance elements in the transmission line. Therefore, the common mode signal cannot be propagated. Therefore, in the same frequency band having the above-mentioned left-handed transmission characteristics, only the differential signal mode is propagated, so that this transmission line functions as a common mode filter.

  On the other hand, when the series impedance element and the shunt admittance element are both advanced elements or both delayed elements, the signal cannot propagate. The frequency band in these states is called a stop band, and it is preferable to match the resonance frequencies of the series impedance element and the shunt admittance element so that the stop band becomes smaller.

Embodiment 2
FIG. 3 is a structural diagram showing the configuration of the left-handed differential transmission line according to the second embodiment of the present invention. The transmission line having the structure of FIG. 3 is represented by the equivalent circuit diagram of FIG. 2 similarly to the transmission line having the structure of FIG. Since the transmission line having the structure of FIG. 3 is represented by the equivalent circuit diagram of FIG. 2, the circuit operation is the same as that of the left-handed differential transmission line according to the first embodiment of FIG. The structure of the left-handed differential transmission line in FIG. 3 is the same as in the first embodiment shown in FIG. This structure is a structure using a planar conductor such as a printed circuit board. 3 is a microstrip line type in which ground is arranged on the lower surface through an insulating layer, a strip line type in which ground is arranged on both upper and lower sides through an insulating layer, and the same plane. A coplanar line type with a ground can also be configured.

  The transmission line having this structure can be realized by using a printed circuit board manufacturing technique, an IC manufacturing technique, or the like. Generally, it is produced based on a photolithography technique. The transmission line of this structure operates by propagation of an electromagnetic field generated in the electromagnetic field propagation medium between the conductor pattern and the ground. The electromagnetic field propagation medium may be a simple insulating material, but the wavelength of the electromagnetic wave is shortened by using a material having a high dielectric constant or a material having a high magnetic permeability. In addition, the insertion loss of the device can be reduced by using a low-loss material. The material constituting the conductor and ground can reduce the insertion loss of the device by selecting a material having high conductivity.

  The left-handed differential transmission line in FIG. 3 is a differential transmission line composed of a first transmission line L1 and a second transmission line L2. The first transmission line L1 includes an A pattern portion L1A, a B pattern portion L1B, and a C pattern portion L1C and a CL pattern portion CL1 sandwiched therebetween. Similarly to the first transmission line L1, the second transmission line L2 includes an A pattern portion L2A, a B pattern portion L2B, and a C pattern portion L2C and a CL pattern portion CL2 sandwiched therebetween. Also, CR pattern portions CR1A and CR2A sandwiched between the A pattern portion of the first transmission line L1 and the A pattern portion of the second transmission line L2, and the B pattern portion and the second transmission of the first transmission line L1. It is composed of CR pattern portions CR1B and CR2B sandwiched between B pattern portions of the line L2. Here, the point that the widths of the C pattern portions L1C and L2C are smaller than the widths of the A pattern portions L1A and L2A and the B pattern portions L1B and L2B is the same as in the first embodiment. This also applies to other embodiments described later.

  The transmission line has this structure as a basic structure (unit cell), and a plurality of these are connected in cascade to form a transmission line. In addition, it is preferable that the length of this structure (unit cell) is sufficiently smaller than the quarter length of the electromagnetic wave wavelength of the frequency to be used.

  The A pattern portions L1A and L2A are rectangular patterns having a width wa and a length la, and the B pattern portions L1B and L2B are rectangular patterns having a width wb and a length lb. The C pattern portions L1C and L2C are band-like patterns having a width wc and a length lc that connect the A pattern portion and the B pattern portion. The CL pattern portions CL1 and CL2 are arranged in parallel connection between the A pattern portion and the B pattern portion adjacent to L1C and L2C, respectively, and are patterns of an interdigital capacitor structure. The inner sides of the C pattern portions L1C and L2C are arranged away from the inner sides of the A pattern portion and the B pattern portion by a distance dc. The CL pattern portions CL1 and CL2 may be arranged only on the inner side as shown in the drawing, only on the outer side, or on both sides with respect to L1C and L2C.

  The CR pattern portions CR1A and CR2A are arranged between the A pattern portion L1A of the first transmission line L1 and the A pattern portion L2A of the second transmission line L2, and the B pattern portion L1B of the first transmission line L1 and the first The CR pattern portions CR1B and CR2B are arranged between the B pattern portions L2B of the two transmission lines L2. A pair of the CR pattern portions CR1A and CR2A and a pair of the CR pattern portions CR1B and CR2B constitute a shunt admittance element. Each of the CR pattern portions is a T-shaped pattern, and forms an inductance and a capacitance. The T-shaped pattern can be designed easily because the design of the inductance and the capacitance can be made independent as compared with the pattern of the interdigital capacitor structure. From the symmetry of the first transmission line L1 and the second transmission line L2, the A pattern part, the B pattern part, and the C pattern part are respectively lines with respect to the center lines of the first transmission line and the second transmission line. Symmetry is preferred.

  The left-handed differential transmission line in FIG. 3 is represented by the equivalent circuit in FIG. 2 as in FIG. The operation of the equivalent circuit of FIG. 2 is the same as that of the first embodiment. The main correspondence between the structure of FIG. 3 and the equivalent circuit of FIG. 2 is as follows.

  The A pattern portions L1A and L2A and the CR pattern portions CR1A and CR2A in FIG. 3 correspond to the A12 portion surrounded by the dotted line of the equivalent circuit in FIG. 2, and the B pattern portions L1B and L2B in FIG. CR1B and CR2B correspond to the B12 portion surrounded by the dotted line of the equivalent circuit of FIG. 2, and the C pattern portions L1C, L2C, CL1, and CL2 of FIG. 3 are the C1 portion surrounded by the dotted line of the equivalent circuit of FIG. And C2 respectively.

  A12LL constituting the A12 portion of the equivalent circuit of FIG. 2 is a line inductance component A12LL between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12LL, B12LL constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12LL between the first transmission line L1 and the second transmission line L2 in the B pattern portion. Of the conductor patterns of the A pattern portion and the B pattern portion, these line inductance components are mainly contributed by the conductor pattern and the CR pattern portion that are on the inner side of the position connected to the C pattern portion. A12LL and B12LL contribute as line inductance components of the shunt element and function as circuit elements having a delayed phase of the shunt element in the left-handed frequency band in which the common mode filter operates.

  A12CR constituting the A12 portion of the equivalent circuit of FIG. 2 is a line capacitance component A12CR between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12CR, B12CR constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12CR between the first transmission line L1 and the second transmission line L2 in the B pattern portion. These line capacitance components are mainly contributed by the CR pattern portion between the first transmission line L1 and the second transmission line L2 in the A pattern portion and the B pattern portion. A12CR and B12CR contribute as line capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  A1CP and A2CP constituting the A12 portion of the equivalent circuit of FIG. 2 are parasitic capacitance components A1CP and A2CP generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion. . Similar to A1CP and A2CP, B1CP and B2CP constituting the B12 portion of the equivalent circuit of FIG. 2 are parasitics generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the B pattern portion. Capacitance components B1CP and B2CP. These parasitic capacitance components are capacitances between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion, the B pattern portion, and the CR pattern portion, and the A pattern portion and the B pattern. The dimension of the portion, the distance dd between the transmission line pattern and the ground conductor GND pattern contribute, and the area of the pattern and the length of the distance dd are the main parameters. A1CP, A2CP, B1CP, and B2CP contribute as parasitic capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  C1LR and C2LR constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are inductance components C1LR and C2LR between the A pattern portion and the B pattern portion in the C pattern portion, and the inductances of the C pattern portions L1C and L2C Corresponding to These inductance components contribute to the size of the C pattern portion. C1LR and C2LR contribute as parallel inductance components of the serial elements of the transmission line, and function as circuit elements having a delay phase of the serial elements in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  C1CL and C2CL constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion, excluding the C pattern portions L1C and L2C. , Corresponding to the capacitance component formed by the CL pattern portions CL1 and CL2 between the A pattern portion and the B pattern portion. These capacitance components contribute to CL pattern portions CL1 and CL2 between the A pattern portion and the B pattern portion. C1CL and C2CL contribute as a parallel capacitance component of the serial element of the transmission line, and function as a circuit element having a leading phase of the serial element in the left-handed frequency band in which the common mode filter operates.

  C1LP and C2LP constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 correspond to inductance components parasitic on the capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion. These inductance components contribute to the dimensions of the A pattern portion, the B pattern portion, and the C pattern portion. C1LP and C2LP contribute as parasitic inductance components of the parallel capacitance of the serial element of the transmission line, and function as circuit elements having a delayed phase of the serial element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  In the structure of FIG. 3, a CL pattern portion is added to the C pattern portion as compared with the structure of FIG. The CL pattern portion constitutes the capacitances C1CL and C2CL in FIG. 2 and C1LP and C2LP serving as parasitic inductances thereof.

  The CL pattern portion has an interdigital capacitor structure, and since the opposing area between patterns can be increased as compared with the capacitance due to the simple gap in FIG. 1, a large capacitance can be obtained with a small area. For this reason, it is a structure suitable for size reduction.

  Further, in the structure of FIG. 3, a T-shaped conductor pattern is arranged in a portion between the distances da and db between the two transmission lines, as compared with the structure of FIG. 1. In this portion, the inductances A12LL and B12LL and the capacitances A12CR and B12CR in FIG. 2 are formed.

  By making this portion T-shaped as shown in FIG. 3, the design values of the inductance LL and the capacitance CR are changed to the T-shaped vertical line portions (A pattern portion and B pattern portion, while having a relatively simple structure. LL and CR independent design because it is possible to design separately for the narrow width part that protrudes inward from the inside and the horizontal line part (wide part that widens in the input / output direction at the tip (inside) of the narrow width part) Therefore, the structure of FIG. 3 is a structure suitable for setting design circuit parameters easily and flexibly.

Embodiment 3
FIG. 4 is a structural diagram showing the configuration of the left-handed differential transmission line according to Embodiment 3 of the present invention. The transmission line having the structure of FIG. 4 is represented by the equivalent circuit diagram of FIG. 2 in the same manner as the transmission line having the structure of FIG. Since the transmission line having the structure of FIG. 4 is represented by the equivalent circuit diagram of FIG. 2, the circuit operation is the same as that of the left-handed differential transmission line according to the first embodiment of FIG.

  The structure of the left-handed differential transmission line in FIG. 4 can be said as in the first embodiment shown in FIG. This structure is a structure using a planar conductor such as a printed circuit board. On the plane line of FIG. 4, a microstrip line type in which ground is arranged on the lower surface via an insulating layer, a strip line type in which ground is arranged on both upper and lower sides via an insulating layer, and on the same plane A coplanar line type with a ground can also be configured.

  The transmission line of this structure can be realized by using a printed circuit board manufacturing technique or an IC manufacturing technique. Generally, it is produced based on a photolithography technique. The transmission line of this structure operates by propagation of an electromagnetic field generated in the electromagnetic field propagation medium between the conductor pattern and the ground. The electromagnetic field propagation medium may be a simple insulating material, but the wavelength of the electromagnetic wave is shortened by using a material having a high dielectric constant or a material having a high magnetic permeability. In addition, the insertion loss of the device can be reduced by using a low-loss material. The material constituting the conductor and ground can reduce the insertion loss of the device by selecting a material having high conductivity.

  The left-handed differential transmission line in FIG. 4 is a differential transmission line constituted by a first transmission line L1 and a second transmission line L2. The first transmission line L1 includes an A pattern portion L1A, a B pattern portion L1B, and a C pattern portion L1C and a CL pattern portion CL1 sandwiched therebetween. Similarly to the first transmission line L1, the second transmission line L2 includes an A pattern portion L2A, a B pattern portion L2B, and a C pattern portion L2C and a CL pattern portion CL2 sandwiched therebetween. Also, CR pattern portions CR1A and CR2A sandwiched between the A pattern portion of the first transmission line L1 and the A pattern portion of the second transmission line L2, and the B pattern portion and the second transmission of the first transmission line L1. It is composed of CR pattern portions CR1B and CR2B sandwiched between B pattern portions of the line L2.

  The transmission line has this structure as a basic structure (unit cell), and a plurality of these are connected in cascade to form a transmission line. In addition, it is preferable that the length of this structure (unit cell) is sufficiently smaller than the quarter length of the electromagnetic wave wavelength of the frequency to be used.

  The A pattern portions L1A and L2A are rectangular patterns having a width wa and a length la, and the B pattern portions L1B and L2B are rectangular patterns having a width wb and a length lb. The C pattern portions L1C and L2C are band-shaped patterns having a width wc and a length lc that connect the A pattern portion and the B pattern portion. However, in order to increase the line length lc and increase the inductance, the C pattern portions L1C and L2C have a folded structure. ing. The C pattern portions L1C and L2C may have various shapes as patterns that obtain a small and large inductance, such as a spiral structure and a double spiral structure, in addition to the folded structure. The C pattern portions CL1 and CL2 are arranged in parallel connection between the A pattern portion and the B pattern portion, adjacent to L1C and L2C, respectively, and are patterns of an interdigital capacitor structure. The inner sides of the C pattern portions L1C and L2C are arranged away from the inner sides of the A pattern portion and the B pattern portion by a distance dc. In the illustrated example, the C pattern portions L1C and L2C are disposed outside the A pattern portion and the B pattern portion. The CL pattern portions CL1 and CL2 may be arranged only on the inner side as shown in the drawing, only on the outer side, or on both sides with respect to L1C and L2C.

  The CR pattern portions CR1A and CR2A are arranged between the A pattern portion L1A of the first transmission line L1 and the A pattern portion L2A of the second transmission line L2, and the B pattern portion L1B of the first transmission line L1 and the first The CR pattern portions CR1B and CR2B are arranged between the B pattern portions L2B of the two transmission lines L2. A pair of the CR pattern portions CR1A and CR2A and a pair of the CR pattern portions CR1B and CR2B constitute a shunt admittance element. Each of the CR pattern portions is a T-shaped pattern, and forms an inductance and a capacitance. The T-shaped pattern can be designed easily because the design of the inductance and the capacitance can be made independent as compared with the pattern of the interdigital capacitor structure. From the symmetry of the first transmission line L1 and the second transmission line L2, the A pattern part, the B pattern part, and the C pattern part are respectively lines with respect to the center lines of the first transmission line and the second transmission line. Symmetry is preferred.

  The left-handed differential transmission line in FIG. 4 is represented by the equivalent circuit in FIG. 2 as in FIG. The operation of the equivalent circuit of FIG. 2 is the same as that of the first embodiment. The main correspondence between the structure of FIG. 4 and the equivalent circuit of FIG. 2 is as follows.

  The A pattern portions L1A and L2A and the CR pattern portions CR1A and CR2A in FIG. 4 correspond to the A12 portion surrounded by the dotted line of the equivalent circuit in FIG. 2, and the B pattern portions L1B and L2B in FIG. CR1B and CR2B correspond to the B12 portion surrounded by the dotted line of the equivalent circuit of FIG. 2, and the C pattern portions L1C and L2C and the CL pattern portions CL1 and CL2 of FIG. 4 are surrounded by the dotted line of the equivalent circuit of FIG. Correspond to the C1 portion and the C2 portion, respectively.

  A12LL constituting the A12 portion of the equivalent circuit of FIG. 2 is a line inductance component A12LL between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12LL, B12LL constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12LL between the first transmission line L1 and the second transmission line L2 in the B pattern portion. Of the conductor patterns of the A pattern portion and the B pattern portion, these line inductance components are mainly contributed by the conductor pattern and the CR pattern portion that are on the inner side of the position connected to the C pattern portion. A12LL and B12LL contribute as line inductance components of the shunt element and function as circuit elements having a delayed phase of the shunt element in the left-handed frequency band in which the common mode filter operates.

  A12CR constituting the A12 portion of the equivalent circuit of FIG. 2 is a line capacitance component A12CR between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12CR, B12CR constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12CR between the first transmission line L1 and the second transmission line L2 in the B pattern portion. These line capacitance components are mainly contributed by the CR pattern portion between the first transmission line L1 and the second transmission line L2 in the A pattern portion and the B pattern portion. A12CR and B12CR contribute as line capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  A1CP and A2CP constituting the A12 portion of the equivalent circuit of FIG. 2 are parasitic capacitance components A1CP and A2CP generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion. . Similar to A1CP and A2CP, B1CP and B2CP constituting the B12 portion of the equivalent circuit of FIG. 2 are parasitics generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the B pattern portion. Capacitance components B1CP and B2CP. These parasitic capacitance components are capacitances between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion, the B pattern portion, and the CR pattern portion, and the A pattern portion and the B pattern. The dimension of the portion, the distance dd between the transmission line pattern and the ground conductor GND pattern contribute, and the area of the pattern and the length of the distance dd are the main parameters. A1CP, A2CP, B1CP, and B2CP contribute as parasitic capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  C1LR and C2LR constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are inductance components C1LR and C2LR between the A pattern portion and the B pattern portion in the C pattern portion, and the inductances of the C pattern portions L1C and L2C Corresponding to These inductance components contribute to the size of the C pattern portion. C1LR and C2LR contribute as parallel inductance components of the serial elements of the transmission line, and function as circuit elements having a delay phase of the serial elements in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  C1CL and C2CL constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion, excluding the C pattern portions L1C and L2C. , Corresponding to the capacitance component formed by the CL pattern portions CL1 and CL2 between the A pattern portion and the B pattern portion. These capacitance components contribute to CL pattern portions CL1 and CL2 between the A pattern portion and the B pattern portion. C1CL and C2CL contribute as a parallel capacitance component of the serial element of the transmission line, and function as a circuit element having a leading phase of the serial element in the left-handed frequency band in which the common mode filter operates.

  C1LP and C2LP constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 correspond to inductance components parasitic on the capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion. These inductance components contribute to the dimensions of the A pattern portion, the B pattern portion, and the C pattern portion. C1LP and C2LP contribute as parasitic inductance components of the parallel capacitance of the serial element of the transmission line, and function as circuit elements having a delayed phase of the serial element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  In the structure of FIG. 4, a CL pattern portion is added to the C pattern portion as compared with the structure of FIG. The CL pattern portion constitutes the capacitances C1CL and C2CL in FIG. 2 and C1LP and C2LP serving as parasitic inductances thereof. It has the same characteristics as the structure of FIG. The CL pattern portion has an interdigital capacitor structure, and the opposing area between patterns can be increased as compared with the capacitance due to the simple gap in FIG. 1, so that a large capacitance can be obtained with a small area. For this reason, it is a structure suitable for size reduction.

  In the structure of FIG. 4, the L1C and L2C patterns of the C pattern portion are folded in comparison with the structure of FIG. Thereby, a big inductance can be constituted. It is also conceivable to make this part a spiral shape or a double spiral shape.

  In the structure of FIG. 4, similarly to FIG. 3, T-shaped conductor patterns are arranged at intervals da and db between two transmission lines. In this portion, the inductances A12LL and B12LL and the capacitances A12CR and B12CR in FIG. 2 are formed. By making this portion T-shaped as shown in FIG. 4, the design values of the inductance LL and the capacitance CR are divided into T-shaped vertical line portions and horizontal line portions while designing a relatively simple structure. Therefore, the LL and the CR can be designed independently. Therefore, the structure of FIG. 4 is a structure suitable for easily and flexibly setting the design circuit parameters.

Embodiment 4
FIG. 5 is a structural diagram showing the configuration of the left-handed differential transmission line according to the fourth embodiment of the present invention. The transmission line having the structure of FIG. 5 is represented by the equivalent circuit diagram of FIG. 2 similarly to the transmission line having the structure of FIG. Since the transmission line having the structure of FIG. 5 is represented by the equivalent circuit diagram of FIG. 2, the circuit operation is the same as that of the left-handed differential transmission line according to the first embodiment of FIG.

  The structure of the left-handed differential transmission line in FIG. 5 can be said as follows in the same manner as in the first embodiment shown in FIG. This structure is a structure using a planar conductor such as a printed circuit board. 5 is a microstrip line type in which ground is arranged on the lower surface via an insulating layer, a strip line type in which ground is arranged on both upper and lower sides via an insulating layer, and the same plane. A coplanar line type with a ground can also be configured.

  The transmission line of this structure can be realized by using a printed circuit board manufacturing technique or an IC manufacturing technique. Generally, it is produced based on a photolithography technique. The transmission line of this structure operates by propagation of an electromagnetic field generated in the electromagnetic field propagation medium between the conductor pattern and the ground. The electromagnetic field propagation medium may be a simple insulating material, but the wavelength of the electromagnetic wave is shortened by using a material having a high dielectric constant or a material having a high magnetic permeability. In addition, the insertion loss of the device can be reduced by using a low-loss material. The material constituting the conductor and ground can reduce the insertion loss of the device by selecting a material having high conductivity.

  The left-handed differential transmission line in FIG. 5 is a differential transmission line constituted by a first transmission line L1 and a second transmission line L2. The first transmission line L1 includes an A pattern portion L1A, a B pattern portion L1B, and a C pattern portion L1C and a CL pattern portion CL1 that are elements therebetween. Similarly to the first transmission line L1, the second transmission line L2 includes an A pattern portion L2A, a B pattern portion L2B, and a C pattern portion L2C and a CL pattern portion CL2 that are elements therebetween. Also, CR pattern portions CR1A and CR2A that are elements between the A pattern portion of the first transmission line L1 and the A pattern portion of the second transmission line L2, and the B pattern portion of the first transmission line L1 and the first It is comprised from CR pattern part CR1B and CR2B which become an element between B pattern parts of two transmission lines L2.

  Each pattern of CL1, CL2, CR2A, and CR2B is formed as a second pattern layer via the insulating layer SUB1 or SUB2 with respect to the first pattern layer that is the other pattern portion. The second pattern layer may be on one side of the upper part or the lower part of the first pattern layer, or may be on both upper and lower sides. In the case of one side, the structure is simple. In the case of both sides, a large capacitance or the like can be configured.

  The transmission line has this structure as a basic structure (unit cell), and a plurality of these are connected in cascade to form a transmission line. In addition, it is preferable that the length of this structure (unit cell) is sufficiently smaller than the quarter length of the electromagnetic wave wavelength of the frequency to be used.

  The A pattern portions L1A and L2A are rectangular patterns having a width wa and a length la, and the B pattern portions L1B and L2B are rectangular patterns having a width wb and a length lb. The C pattern portions L1C and L2C are band-like patterns having a width wc and a length lc connecting the A pattern portion and the B pattern portion. In order to increase the inductance by increasing the line length lc, the C pattern portions L1C and L2C may have various shapes such as a zigzag folded structure, a spiral structure, a double spiral structure, and the like to obtain a small and large inductance pattern. The inner sides of the C pattern portions L1C and L2C are arranged away from the inner sides of the A pattern portion and the B pattern portion by a distance dc.

  The CL pattern portions CL1 and CL2 are patterns arranged in parallel connection adjacent to L1C and L2C, respectively, between the A pattern portion and the B pattern portion. The CL pattern portions CL1 and CL2 are patterns arranged in another second pattern layer via the insulating layer SUB1 with respect to the first pattern layer in which L1C and L2C are arranged. The CL pattern portions CL1 and CL2 are mainly electrostatically coupled to the A pattern portion and the B pattern portion, and form capacitances C1CL and C2CL between the A pattern portion and the B pattern portion. Capacitances C1CL and C2CL are MIM capacitor structures, and the capacitance can be adjusted by changing the thickness of the insulating layer (I) or changing the facing area between metal (M) patterns. Therefore, the structure is simpler than the interdigital capacitor structure shown in FIG. 4, and it is suitable for adjusting the capacitance and constructing a large capacitance.

  The CR pattern portions CR1A and CR2A are arranged between the A pattern portion L1A of the first transmission line L1 and the A pattern portion L2A of the second transmission line L2, and the B pattern portion L1B of the first transmission line L1 and the first The CR pattern portions CR1B and CR2B are arranged between the B pattern portions L2B of the two transmission lines L2. A pair of the CR pattern portions CR1A and CR2A and a pair of the CR pattern portions CR1B and CR2B constitute a shunt admittance element. The CR pattern portions CR2A and CR2B are patterns arranged in another second pattern layer via the insulating layer SUB1 with respect to the first pattern layer in which CR1A and CR1B are arranged. CR pattern portions CR2A and CR2B are electrostatically coupled with CR1A and CR1B to form capacitances A12CR and B12CR. Capacitances A12CR and B12CR are MIM capacitor structures, and the capacitance can be adjusted by changing the thickness of the insulating layer (I) or changing the facing area between metal (M) patterns. Therefore, the structure is simpler than the interdigital capacitor structure and T-shaped pattern shown in FIG. 4, and it is suitable for adjusting the capacitance and constructing a large capacitance. From the symmetry of the first transmission line L1 and the second transmission line L2, the A pattern part, the B pattern part, and the C pattern part are respectively lines with respect to the center lines of the first transmission line and the second transmission line. Symmetry is preferred.

  The left-handed differential transmission line in FIG. 5 is represented by the equivalent circuit in FIG. 2 as in FIG. The operation of the equivalent circuit of FIG. 2 is the same as that of the first embodiment. The main correspondence between the structure of FIG. 5 and the equivalent circuit of FIG. 2 is as follows.

  The A pattern portions L1A and L2A and the CR pattern portions CR1A and CR2A in FIG. 5 correspond to the A12 portion surrounded by the dotted line of the equivalent circuit in FIG. 2, and the B pattern portions L1B and L2B in FIG. CR1B and CR2B correspond to the B12 portion surrounded by the dotted line of the equivalent circuit of FIG. 2, and the C pattern portions L1C and L2C and the CL pattern portions CL1 and CL2 of FIG. 5 are dotted lines of the equivalent circuit of FIG. It corresponds to the enclosed C1 part and C2 part, respectively.

  A12LL constituting the A12 portion of the equivalent circuit of FIG. 2 is a line inductance component A12LL between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12LL, B12LL constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12LL between the first transmission line L1 and the second transmission line L2 in the B pattern portion. Of the conductor patterns of the A pattern portion and the B pattern portion, these line inductance components are mainly contributed by the conductor pattern and the CR pattern portion that are on the inner side of the position connected to the C pattern portion. A12LL and B12LL contribute as line inductance components of the shunt element and function as circuit elements having a delayed phase of the shunt element in the left-handed frequency band in which the common mode filter operates.

  A12CR constituting the A12 portion of the equivalent circuit of FIG. 2 is a line capacitance component A12CR between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12CR, B12CR constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12CR between the first transmission line L1 and the second transmission line L2 in the B pattern portion. These line capacitance components are mainly contributed by the CR pattern portion between the first transmission line L1 and the second transmission line L2 in the A pattern portion and the B pattern portion. A12CR and B12CR contribute as line capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  A1CP and A2CP constituting the A12 portion of the equivalent circuit of FIG. 2 are parasitic capacitance components A1CP and A2CP generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion. . Similar to A1CP and A2CP, B1CP and B2CP constituting the B12 portion of the equivalent circuit of FIG. 2 are parasitics generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the B pattern portion. Capacitance components B1CP and B2CP. These parasitic capacitance components are capacitances between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion, the B pattern portion, and the CR pattern portion, and the A pattern portion and the B pattern. The dimension of the portion, the distance dd between the transmission line pattern and the ground conductor GND pattern contribute, and the area of the pattern and the length of the distance dd are the main parameters. A1CP, A2CP, B1CP, and B2CP contribute as parasitic capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  C1LR and C2LR constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are inductance components C1LR and C2LR between the A pattern portion and the B pattern portion in the C pattern portion, and the inductances of the C pattern portions L1C and L2C Corresponding to These inductance components contribute to the size of the C pattern portion. C1LR and C2LR contribute as parallel inductance components of the serial elements of the transmission line, and function as circuit elements having a delay phase of the serial elements in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  C1CL and C2CL constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion, excluding the C pattern portions L1C and L2C. , Corresponding to the gap component between the A pattern portion and the B pattern portion and the capacitance component formed by the CL pattern portions CL1 and CL2. These capacitance components contribute to the gap between the A pattern portion and the B pattern portion and the CL pattern portions CL1 and CL2. C1CL and C2CL contribute as a parallel capacitance component of the serial element of the transmission line, and function as a circuit element having a leading phase of the serial element in the left-handed frequency band in which the common mode filter operates.

  C1LP and C2LP constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 correspond to inductance components parasitic on the capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion. These inductance components contribute to the dimensions of the A pattern portion, the B pattern portion, and the C pattern portion. C1LP and C2LP contribute as parasitic inductance components of the parallel capacitance of the serial element of the transmission line, and function as circuit elements having a delayed phase of the serial element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  In the structure of FIG. 5, a CL pattern portion is added to the C pattern portion as compared with the structure of FIG. The CL pattern portion constitutes the capacitances C1CL and C2CL in FIG. 2 and C1LP and C2LP serving as parasitic inductances thereof. It has the same characteristics as the structure of FIG. 3 and FIG.

  The CL pattern portion has an MIM capacitor structure, and the opposing area between patterns can be increased as compared with the capacitance due to the simple gap in FIG. 1, so that a large capacitance can be obtained with a small area. For this reason, it is a structure suitable for size reduction. Further, since the structure is simple compared to the interdigital capacitor structure of FIGS. 3 and 4, the design is easy and a large capacitance can be obtained.

  The L1C and L2C patterns of the C pattern portion of the structure of FIG. 5 may be formed in a spelled shape, a spiral shape, a double spiral shape, or the like as in FIG. Thereby, a big inductance can be constituted.

  Further, in the structure of FIG. 5, the CR pattern portion is arranged in the portions of the distances da and db between the two transmission lines as compared with the structure of FIG. 1. In this portion, the inductances A12LL and B12LL and the capacitances A12CR and B12CR in FIG. 2 are formed.

  Since the MIM capacitor structure as shown in FIG. 5 can increase the opposing area between patterns in this portion as compared with the capacitance due to the simple gap of FIG. 1, a large capacitance can be obtained with a small area. For this reason, it is a structure suitable for size reduction. Moreover, compared with the T-shaped structure of FIG. 3 and FIG. 4, design is easy and a big capacitance can be obtained.

Embodiment 5
FIG. 6 is a structural diagram showing the configuration of the left-handed differential transmission line according to the fifth embodiment of the present invention. The transmission line having the structure of FIG. 6 is represented by the equivalent circuit diagram of FIG. 2 in the same manner as the transmission line having the structure of FIG. Since the transmission line having the structure of FIG. 6 is represented by the equivalent circuit diagram of FIG. 2, the circuit operation is the same as that of the left-handed differential transmission line according to the first embodiment of FIG.

  The structure of the left-handed differential transmission line of FIG. 6 can be said as in the first embodiment shown in FIG. This structure is a structure using a planar conductor such as a printed circuit board. The microstrip line type in which the ground is disposed on the lower surface of the planar line in FIG. 6 via the insulating layer, the strip line type in which ground is disposed on the upper and lower surfaces via the insulating layer, and the same plane. A coplanar line type with a ground can also be configured.

  The transmission line having this structure can be realized by using a printed circuit board manufacturing technique, an IC manufacturing technique, or the like. Generally, it is produced based on a photolithography technique. The transmission line of this structure operates by propagation of an electromagnetic field generated in the electromagnetic field propagation medium between the conductor pattern and the ground. The electromagnetic field propagation medium may be a simple insulating material, but the wavelength of the electromagnetic wave is shortened by using a material having a high dielectric constant or a material having a high magnetic permeability. In addition, the insertion loss of the device can be reduced by using a low-loss material. The material constituting the conductor and ground can reduce the insertion loss of the device by selecting a material having high conductivity.

  The left-handed differential transmission line in FIG. 6 is a differential transmission line composed of a first transmission line L1 and a second transmission line L2. The first transmission line L1 includes an A pattern portion L1A, a B pattern portion L1B, and a C pattern portion L1C serving as an element therebetween. Similarly to the first transmission line L1, the second transmission line L2 includes an A pattern portion L2A, a B pattern portion L2B, and a C pattern portion L2C serving as an element therebetween.

  Note that the first pattern layer, which is a pattern portion constituting the first transmission line L1, and the second pattern layer, which is a pattern portion constituting the second transmission line L2, are stacked via the insulating layer SUB1 or SUB2. Formed. Either the upper or lower positional relationship between the first pattern layer and the second pattern layer may be upper.

  The transmission line has this structure as a basic structure (unit cell), and a plurality of these are connected in cascade to form a transmission line. In addition, it is preferable that the length of this structure (unit cell) is sufficiently smaller than the quarter length of the electromagnetic wave wavelength of the frequency to be used.

  The A pattern portions L1A and L2A are rectangular patterns having a width wa and a length la, and the B pattern portions L1B and L2B are rectangular patterns having a width wb and a length lb. The C pattern portions L1C and L2C are band-like patterns having a width wc and a length lc connecting the A pattern portion and the B pattern portion. In order to increase the inductance by increasing the line length lc, the C pattern portions L1C and L2C may have various shapes such as a zigzag folded structure, a spiral structure, a double spiral structure, and the like to obtain a small and large inductance pattern. The sides of the C pattern portions L1C and L2 are arranged at a distance dc inside the A pattern portion and the B pattern portion. Although not shown in FIG. 6, CL pattern portions CL1 and CL2 may be provided similarly to FIG. 4 in order to increase the capacitance. As the CL pattern portions CL1 and CL2, an interdigital capacitor structure in which the CL pattern portions CL1 and CL2 are arranged in parallel and adjacent to the L1C and L2C between the A pattern portion and the B pattern portion is appropriate. From the symmetry of the first transmission line L1 and the second transmission line L2, the A pattern part, the B pattern part, and the C pattern part are respectively lines with respect to the center lines of the first transmission line and the second transmission line. Symmetry is preferred.

  The left-handed differential transmission line in FIG. 6 is represented by the equivalent circuit in FIG. 2 as in FIG. The operation of the equivalent circuit of FIG. 2 is the same as that of the first embodiment. The main correspondence between the structure of FIG. 6 and the equivalent circuit of FIG. 2 is as follows.

  The A pattern portions L1A and L2A of FIG. 6 correspond to the A12 portion surrounded by the dotted line of the equivalent circuit of FIG. 2, and the B pattern portions L1B and L2B of FIG. 6 are surrounded by the dotted line of the equivalent circuit of FIG. Corresponding to the B12 portion, the C pattern portions L1C and L2C in FIG. 6 respectively correspond to the C1 portion and the C2 portion surrounded by the dotted line of the equivalent circuit in FIG.

  A12LL constituting the A12 portion of the equivalent circuit of FIG. 2 is a line inductance component A12LL between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12LL, B12LL constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12LL between the first transmission line L1 and the second transmission line L2 in the B pattern portion. Of these conductor patterns of the A pattern portion and the B pattern portion, these line inductance components are mainly contributed by the conductor pattern inside the position connected to the C pattern portion. A12LL and B12LL contribute as line inductance components of the shunt element and function as circuit elements having a delayed phase of the shunt element in the left-handed frequency band in which the common mode filter operates.

  A12CR constituting the A12 portion of the equivalent circuit of FIG. 2 is a line capacitance component A12CR between the first transmission line L1 and the second transmission line L2 in the A pattern portion. Similarly to A12CR, B12CR constituting the B12 portion of the equivalent circuit of FIG. 2 is a line inductance component B12CR between the first transmission line L1 and the second transmission line L2 in the B pattern portion. In these line capacitance components, the gap between the first transmission line L1 and the second transmission line L2 in the A pattern portion and the B pattern portion mainly contributes. A12CR and B12CR contribute as line capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  A1CP and A2CP constituting the A12 portion of the equivalent circuit of FIG. 2 are parasitic capacitance components A1CP and A2CP generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion. . Similar to A1CP and A2CP, B1CP and B2CP constituting the B12 portion of the equivalent circuit of FIG. 2 are parasitics generated between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the B pattern portion. Capacitance components B1CP and B2CP. These parasitic capacitance components are capacitances between the first transmission line L1 and the second transmission line L2 and the ground conductor GND in the A pattern portion and the B pattern portion, and the dimensions of the A pattern portion and the B pattern portion. The distance dd between the transmission line pattern and the ground conductor GND pattern contributes, and the area of the pattern and the length of the distance dd are the main parameters. A1CP, A2CP, B1CP, and B2CP contribute as parasitic capacitance components of the shunt element, and function as circuit elements having a lead phase of the shunt element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  C1LR and C2LR constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are inductance components C1LR and C2LR between the A pattern portion and the B pattern portion in the C pattern portion, and the inductances of the C pattern portions L1C and L2C Corresponding to These inductance components contribute to the size of the C pattern portion. C1LR and C2LR contribute as parallel inductance components of the serial elements of the transmission line, and function as circuit elements having a delay phase of the serial elements in a frequency band lower than the left-handed frequency band in which the common mode filter operates.

  C1CL and C2CL constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 are capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion, excluding the C pattern portions L1C and L2C. , Corresponding to the capacitance component formed by the gap between the A pattern portion and the B pattern portion. These capacitance components contribute to a gap between the A pattern portion and the B pattern portion. C1CL and C2CL contribute as a parallel capacitance component of the serial element of the transmission line, and function as a circuit element having a leading phase of the serial element in the left-handed frequency band in which the common mode filter operates.

  C1LP and C2LP constituting the C1 and C2 portions of the equivalent circuit of FIG. 2 correspond to inductance components parasitic on the capacitance components C1CL and C2CL between the A pattern portion and the B pattern portion in the C pattern portion. The dimensions of the A pattern portion and the B pattern portion contribute to these inductance components. C1LP and C2LP contribute as parasitic inductance components of the parallel capacitance of the serial element of the transmission line, and function as circuit elements having a delayed phase of the serial element in a frequency band higher than the left-handed frequency band in which the common mode filter operates. .

  Since the structure of FIG. 6 has a simple pattern shape as in FIG. 1, the number of dimensional parameter elements when designing a transmission line is small, so that the design can be facilitated. In addition, since the shape is simple, there is an advantage that the size can be easily reduced according to the fine pattern technology of the thin film. Furthermore, the structure of FIG. 6 has an advantage that the occupied area can be reduced because the first transmission line L1 and the second transmission line L2 are divided into two layers and laminated as compared with the structure of FIG. is there.

Embodiment 6
FIG. 7 is a bird's-eye view of the structure showing the configuration of the left-handed differential transmission line according to the sixth embodiment of the present invention. FIG. 8 is a top view of a conductor line pattern having a structure showing the configuration of the left-handed differential transmission line according to the sixth embodiment of the present invention. FIGS. 7 and 8 are different views of the same structure, and show a unit cell that is a basic structure of a left-handed differential transmission line. The transmission line having the structure of FIGS. 7 and 8 is represented by the equivalent circuit diagram of FIG. 2 in the same manner as the transmission line having the structure of FIG. Since the transmission line having the structure of FIGS. 7 and 8 is represented by the equivalent circuit diagram of FIG. 2, the circuit operation is the same as that of the left-handed differential transmission line according to the first embodiment of FIG.

  The structure shown in FIGS. 7 and 8 is the same structure based on the second embodiment of the present invention shown in FIG. Therefore, it has the same characteristics as the left-handed differential transmission line according to Embodiment 2 of FIG. Since this structure has the same characteristics as those in FIG. 3, in particular, in the conventional technique (Non-Patent Document 4), the shunt admittance portion is an interdigital capacitor structure, and the series inductance element LL constituting the shunt admittance Although the element design of the series capacitance element CR was complicated without being independent, in this structure, the same part was changed to a T-shape, so that the design of the LL and the CR was separated and easy to design.

  3 is different from the structure of FIG. 3 in that the interdigital capacitor structure of the CL pattern portions CL1 and CL2 in FIG. 3 increases the number of fingers to be elongated and narrows the interval between the fingers, thereby forming a large capacitance CL. It is a point. In addition, the arrangement of the inductance elements of the C pattern portions L1C and L2C in FIG. 3 is arranged outside the transmission line with respect to the CL1 and CL2 portions in FIG. 3, whereas in the structure of FIGS. It is the point arrange | positioned inside the transmission line. By placing the inductance element on the inside, the coupling between the two transmission lines of the differential transmission line is strengthened, so that the mutual inductance increases, and there is a large difference in the inductance of the equivalent circuit between the differential mode and the common mode. Can give birth. This is expected to improve the characteristics of the common mode filter.

  FIG. 9 is a bird's-eye view of a structure in which three unit cells are cascade-connected with respect to the configuration of the left-handed differential transmission line according to the sixth embodiment of the present invention. In principle, the unit cells having the structure shown in FIGS. 7 and 8 are cascaded to form a device composed of three unit cell elements.

  7 and FIG. 8 is different from the structure of FIG. 7 in that the portion constituting the shunt admittance at the input end and the portion constituting the shunt admittance at the output end of FIG. 7 and 8 may be designed with the same dimensions as those of the device shown in FIG. 8, but the dimensional design of the portion constituting the intermediate shunt admittance other than the input / output ends is different from that of the ends.

  When unit cells are connected in cascade, the unit cells may interfere with each other not only structurally but also electromagnetically. If the unit cells are simply arranged, operation of the equivalent circuit is desired. Will change with respect to the design. When the unit cells are connected in cascade, they are not simply connected structurally, but need to be appropriately changed so that the equivalent circuit to be operated satisfies desired characteristics.

  In the structure of FIG. 9, the T-shaped conductor pattern is designed to reduce the inductance mainly by increasing the width of the vertical line portion constituting the inductance, compared to the structure of the shunt admittance element at the input / output end. The capacitance is designed to be large by enlarging the horizontal line portion facing the T-shape and narrowing the interval between the two T-shapes. With these ideas, the parameters of the equivalent circuit are adjusted, and the inductance and capacitance components of the unit cells to be connected are mutually matched to match the resonance frequency and Bloch impedance characteristics. Prevents deterioration.

  FIG. 10 shows a differential (differential signal) mode as a result of a characteristic simulation using a three-dimensional electromagnetic field analysis on a device in which three unit cells of FIG. 9 according to Embodiment 6 of the present invention are connected in cascade. In addition, the frequency characteristics of the magnitude of the transmission coefficient of the common (common mode noise) mode are compared. Three-dimensional electromagnetic field analysis was performed using three-dimensional electromagnetic field analysis software SONNET manufactured by Sonnet Software, USA. SONNET is suitable for analysis of a device model having a planar structure, and uses an analysis method based on the moment method.

  As a three-dimensional electromagnetic field analysis condition, the air layer around the device was set to about 15 mm in the thickness direction of the device and about 5 mm in the width direction of the device in consideration of the influence of the boundary and the analysis region that can be calculated. The conductor material was copper having a thickness of 17 μm, and the dielectric material was assumed to be 1.575 mm thick Rogers RT / 5880 (relative dielectric constant εr = 2.2, tan δ=0.0009@10 GHz). The cell size used for the analysis was set to 0.01 mm × 0.01 mm. As a result of optimizing the device dimensions, the external dimensions of the device were about 17.2 mm in length, about 21.2 mm in width, and about 1.6 mm in thickness when the three unit cells were combined.

  The dimension parameters of each part of the device were set as follows. The line width W1 of each input / output port was 4.58 mm, and the distance d between the ports was 12.02 mm. Capacitance CL by the interdigital capacitor constituting the series impedance element was 10 pairs of interdigital capacitors with the finger line width WCL being 0.08 mm, the spacing SCL being 0.12 mm, and the length LCL being 2.7 mm. The inductance LR by the microstrip line constituting the series impedance element is arranged so that the length L2 is 2.82 mm and the line width WLR is 0.38 mm, and is arranged in parallel with the interdigital capacitor CL. Z was constructed. The shunt capacitance CR1 by the horizontal line portion of the T-shaped structure constituting the shunt admittance element at both end portions (input / output end portions) of the transmission line has a width WCR1 of the T-shaped horizontal line portion of 1.18 mm and a length LCR1. Was 4.08 mm, and the distance SCR1 between the two T-shaped patterns was 0.12 mm. The shunt inductance LL1 by the microstrip line of the vertical line portion of the T-shaped structure constituting the shunt admittance element at both end portions (input / output end portions) of the transmission line is the length LLL1 of the T-shaped vertical line portion. The thickness was 4.77 mm and the line width WLL1 was 0.08 mm. On the other hand, the shunt capacitance CR2 by the horizontal line portion of the T-shaped structure that constitutes the shunt admittance element in the intermediate portion (except for the input / output end) of the transmission line has a width WCR2 of the T-shaped horizontal line portion of 0.98 mm, The length LCR2 was set to 5.58 mm, and the distance SCR2 between the two T-shaped patterns was set to 0.12 mm. The shunt inductance LL2 due to the microstrip line in the vertical line portion of the T-shaped structure constituting the shunt admittance element in the intermediate portion (except for the input / output end) of the transmission line is the length LLL2 of the T-shaped vertical line portion. Was 4.97 mm, and the line width WLL2 was 0.58 mm.

  When considering a device in which three unit cells are connected in cascade, attenuation is larger than that of a single unit cell device. At this time, it is good that the attenuation of the common mode component is increased, but care must be taken because the attenuation of the differential mode component also increases. In order to satisfy the practical performance, it is necessary to make the transmission coefficient of the common mode component smaller than the target value and make the transmission coefficient of the differential mode component larger than the target value. Therefore, when a device is configured by cascade connection of unit cells, the number of cells to be cascaded is set in a range not less than the number of cells that can sufficiently suppress the common mode component and not more than the number of cells through which the differential mode component sufficiently transmits. There is a need. In the design of this device, three were the appropriate number of cells.

  The result of making a prototype of the device designed with the above dimensions is shown. For production, an RT / 5880 substrate manufactured by Rogers (relative dielectric constant εr = 2.2, tan δ=0.0009@10 GHz, dielectric thickness 1.575 mm, copper foil thickness 17 μm, double-sided copper foil) is used. The entire back surface was used as a ground plane as it was, and a conductor pattern was formed on the surface by photolithography and wet etching. SMA connectors are connected to each of the four input / output ports of the completed transmission line board, and the differential / common mode software fixture function is attached to the differential mode and common mode using a 4-port network analyzer (R3767CG manufactured by Advancedtest). The transmission characteristics of were measured.

  FIG. 11 shows the result of measuring the transmission characteristics of a prototype device for a device in which three unit cells of FIG. 9 according to the sixth embodiment of the present invention are connected in cascade. As a result, the differential (differential signal) mode and the common (in-phase) This is a comparison of the frequency characteristics of the magnitude of the transmission coefficient of the (noise) mode.

  FIG. 12 shows the result of measuring the transmission characteristics of the prototype device for a device in which three unit cells of FIG. 9 according to the sixth embodiment of the present invention are connected in cascade. As a result, the differential (differential signal) mode and the common (in-phase) This is a comparison of the frequency characteristics of the magnitude of the transmission coefficient of the (noise) mode.

  From the characteristics shown in FIG. 11, a band satisfying −20 dB or less, which is a practical target specification, was obtained particularly for the common mode component. On the other hand, the attenuation of the differential mode component is also large, and is about −2 to −4 dB in the vicinity of 4 GHz, which causes a somewhat large loss.

  From the characteristics of FIG. 12, when analyzing the left-handed signal transmission band, it can be seen that the phase of the transmission coefficient S21 (the input / output phase difference) is 0 degree at about 4.2 GHz. Since the phase has a periodic property in the range of -180 degrees to +180 degrees, it is difficult to find an intrinsic 0 degree phase, but it is difficult to find the result of collation with the result of electromagnetic field analysis and the result of one unit cell device. The phase change can be analyzed by comparison. From this, it can be analyzed that the higher frequency side than about 4.2 GHz is a right-handed operation, and the lower frequency side is a left-handed operation. Furthermore, considering the frequency of the stop band described above, it can be seen that the left-handed signal transmission band is a band of about 3.7 to 4.2 GHz, which is a result of slightly wider than the left-handed signal transmission band of the conventional device. was gotten.

  When the characteristics as the common mode filter of the device of the three unit cells are rearranged from the frequency characteristics of the transmission coefficient of FIG. 11, the common mode component is a practical target of −20 dB or less in the frequency band of about 3.8 to 4.0 GHz. On the other hand, the differential mode component has a maximum value of about −2 dB, and the practical target specification of −1 dB or more could not be satisfied. However, the value was larger than −8 dB of the conventional prototype device, and the effect of improving the characteristics was obtained.

  Note that the transmission line of the present invention is not limited to the illustrated examples described above, and various modifications can be made without departing from the scope of the present invention.

  The description of the symbols shown in FIG. 1 is as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2. L1A, L1B, L1C, L2A, L2B, and L2C are conductor patterns, respectively. L1A: Conductor pattern of the input A pattern portion of the first transmission line L1, L1B: Conductor pattern of the output B pattern portion of the first transmission line L1, L1C: Input side of the first transmission line L1 A conductor pattern of the C pattern portion between the A pattern and the output B pattern portion, L2A: a conductor pattern of the input A pattern portion of the second transmission line L2, and L2B: an output side B of the second transmission line L2. Conductor pattern of pattern portion, L2C: Conductor pattern of C pattern portion intermediate between input side A pattern and output side B pattern portion of second transmission line L2.

  Wa, wb, and wc are dimensions of the conductor pattern in the width direction (direction perpendicular to the transmission line). wa: L1A and L2A conductor pattern width direction (direction perpendicular to the transmission line) dimension, wb: L1B and L2B conductor pattern width direction (direction perpendicular to the transmission line) dimension, wc: L1C and The width direction (direction perpendicular to the transmission line) dimension of the L2C conductor pattern.

  la, lb, and lc are dimensions in the length direction of the conductor pattern (line direction of the transmission line). la: L1A and L2A conductor pattern length direction (transmission line line direction) dimensions, lb: L1B and L2B conductor pattern length direction (transmission line line direction) dimensions, lc: L1C and L2C conductor patterns Length direction (transmission line direction) dimensions.

  da, db, and dc are dimensions relating to the gap portion between the first transmission line L1 and the second transmission line L2, respectively. da: the gap between the L1A and L2A conductor patterns, db: the gap between the L1B and L2B conductor patterns, dc: the L1A and L2A conductor patterns, or the L1B and L2B conductor patterns, The length dimension of the portion discharged to the inside of the transmission line with respect to the L1C and L2C conductor patterns.

  The description of the reference numerals shown in FIG. 2 is as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2. A circuit portion serving as an input side shunt admittance element is denoted by A12. A circuit portion serving as an output side shunt admittance element is defined as B12. A circuit portion serving as a series impedance element of the first transmission line L1 is defined as C1. A circuit portion serving as a series impedance element of the second transmission line L2 is defined as C2.

  A12, B12, C1, and C2 are each a set of circuit elements. A12: a circuit part serving as an input side shunt admittance element, B12: a circuit part serving as an output side shunt admittance element, C1: a circuit part serving as a series impedance element of the first transmission line L1, C2: second transmission line A circuit portion that is a series impedance element of L2.

  A12LL, A12CR, A1CP, and A2CP are circuit elements included in the circuit portion A12 serving as an input side shunt admittance element. A12LL: a series inductance component acting between the first transmission line L1 and the second transmission line L2, A12CR: a series capacitance component acting between the first transmission line L1 and the second transmission line L2, A1CP: a shunt capacitance component acting between the first transmission line L1 and the ground, A2CP: a shunt capacitance component acting between the second transmission line L2 and the ground.

  B12LL, B12CR, B1CP, and B2CP are circuit elements included in the circuit portion B12 serving as an output side shunt admittance element. B12LL: a series inductance component acting between the first transmission line L1 and the second transmission line L2, B12CR: a series capacitance component acting between the first transmission line L1 and the second transmission line L2, B1CP: a shunt capacitance component acting between the first transmission line L1 and the ground, B2CP: a shunt capacitance component acting between the second transmission line L2 and the ground.

  C1LR, C1CL, and C1LP are circuit elements included in the circuit portion C1 that is a series impedance element of the first transmission line L1. C1LR: parallel inductance component in the series impedance element of the first transmission line L1, C1CL: parallel capacitance component in the series impedance element of the first transmission line L1, C1LP: parallel capacitance component in the series impedance element of the first transmission line L1 Parasitic inductance component included in.

  C2LR, C2CL, and C2LP are circuit elements included in the circuit portion C2 that is a series impedance element of the second transmission line L2. C2LR: parallel inductance component in the series impedance element of the second transmission line L2, C2CL: parallel capacitance component in the series impedance element of the second transmission line L2, C2LP: parallel capacitance component in the series impedance element of the second transmission line L2. Parasitic inductance component included in.

  The description of the reference numerals shown in FIG. 3 is as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2.

  L1A, L1B, L1C, L2A, L2B, and L2C are conductor patterns, respectively, and are the same as the symbols shown in FIG. L1A: Conductor pattern of the input A pattern portion of the first transmission line L1, L1B: Conductor pattern of the output B pattern portion of the first transmission line L1, L1C: Input side of the first transmission line L1 A conductor pattern for mainly forming an inductance component in the C pattern portion between the A pattern and the output side B pattern portion, L2A: the conductor pattern of the input A pattern portion of the second transmission line L2, and L2B: second Conductor pattern for output B pattern portion of transmission line L2, L2C: Conductor for mainly constituting an inductance component in C pattern portion between input A pattern and output B pattern portion of second transmission line L2. pattern.

  CL1 and CL2 are conductor patterns for forming capacitance components, respectively. CL1: Conductor pattern for mainly forming a capacitance component in the C pattern portion in the middle of the input side A pattern and the output side B pattern portion in the first transmission line L1, CL2: input side in the second transmission line L2 A conductor pattern for mainly constituting a capacitance component in the C pattern portion between the A pattern and the output side B pattern portion.

  CR1A, CR2A, CR1B, and CR2B are conductor patterns that constitute a series inductance component and a series capacitance component of a circuit portion that is a shunt admittance element, respectively. CR1A and CR2A together constitute an input side shunt admittance element, and CR1B and CR2B together constitute an input side shunt admittance element.

  4 is the same as that shown in FIG. 3 and is as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2.

  L1A, L1B, L1C, L2A, L2B, and L2C are conductor patterns, respectively, and are the same as the symbols shown in FIG. L1A: Conductor pattern of the input A pattern portion of the first transmission line L1, L1B: Conductor pattern of the output B pattern portion of the first transmission line L1, L1C: Input side of the first transmission line L1 A conductor pattern for mainly forming an inductance component in the C pattern portion between the A pattern and the output side B pattern portion, L2A: the conductor pattern of the input A pattern portion of the second transmission line L2, and L2B: second Conductor pattern for output B pattern portion of transmission line L2, L2C: Conductor for mainly constituting an inductance component in C pattern portion between input A pattern and output B pattern portion of second transmission line L2. pattern.

  CL1 and CL2 are conductor patterns for forming capacitance components, respectively. CL1: Conductor pattern for mainly forming a capacitance component in the C pattern portion in the middle of the input side A pattern and the output side B pattern portion in the first transmission line L1, CL2: input side in the second transmission line L2 A conductor pattern for mainly constituting a capacitance component in the C pattern portion between the A pattern and the output side B pattern portion.

  CR1A, CR2A, CR1B, and CR2B are conductor patterns that constitute a series inductance component and a series capacitance component of a circuit portion that is a shunt admittance element, respectively. CR1A and CR2A together constitute an input side shunt admittance element, and CR1B and CR2B together constitute an input side shunt admittance element.

  The reference numerals shown in FIG. 5 are substantially the same as those shown in FIG. 3 and are as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2.

  L1A, L1B, L1C, L2A, L2B, and L2C are conductor patterns, respectively, and are the same as the symbols shown in FIG. L1A: Conductor pattern of the input A pattern portion of the first transmission line L1, L1B: Conductor pattern of the output B pattern portion of the first transmission line L1, L1C: Input side of the first transmission line L1 A conductor pattern for mainly forming an inductance component in the C pattern portion between the A pattern and the output side B pattern portion, L2A: the conductor pattern of the input A pattern portion of the second transmission line L2, and L2B: second Conductor pattern for output B pattern portion of transmission line L2, L2C: Conductor for mainly constituting an inductance component in C pattern portion between input A pattern and output B pattern portion of second transmission line L2. pattern.

  CL1 and CL2 are conductor patterns for forming capacitance components, respectively. CL1: Conductor pattern for mainly forming a capacitance component in the C pattern portion in the middle of the input side A pattern and the output side B pattern portion in the first transmission line L1, CL2: input side in the second transmission line L2 A conductor pattern for mainly constituting a capacitance component in the C pattern portion between the A pattern and the output side B pattern portion.

  CR1A, CR2A, CR1B, and CR2B are conductor patterns that constitute a series inductance component and a series capacitance component of a circuit portion that is a shunt admittance element, respectively. CR1A and CR2A together constitute an input side shunt admittance element, and CR1B and CR2B together constitute an input side shunt admittance element.

  However, the following symbols in FIG. 5 are different from those in FIG. SUB1 and SUB2 indicate substrates of respective layers of the conductor pattern that is divided into two layers and stacked. The primary first conductor pattern layer is SUB1, and the secondary second conductor pattern layer is SUB2.

  The reference numerals shown in FIG. 6 are substantially the same as those shown in FIG. 5 and are as follows. A conductor pattern between the + input terminal and the + output terminal is defined as a first transmission line L1. The conductor pattern between the input terminal and the output terminal is a second transmission line L2.

  L1A, L1B, L1C, L2A, L2B, and L2C are conductor patterns, respectively, and are the same as the symbols shown in FIG. L1A: Conductor pattern of the input A pattern portion of the first transmission line L1, L1B: Conductor pattern of the output B pattern portion of the first transmission line L1, L1C: Input side of the first transmission line L1 A conductor pattern for mainly forming an inductance component in the C pattern portion between the A pattern and the output side B pattern portion, L2A: the conductor pattern of the input A pattern portion of the second transmission line L2, and L2B: second Conductor pattern for output B pattern portion of transmission line L2, L2C: Conductor for mainly constituting an inductance component in C pattern portion between input A pattern and output B pattern portion of second transmission line L2. pattern.

  SUB1 and SUB2 indicate substrates of respective layers of the conductor pattern that is divided into two layers and stacked. The first conductor pattern layer in which the first transmission line L1 is arranged is SUB1, and the second conductor pattern layer in which the second transmission line L2 is arranged is SUB2.

Claims (6)

A pair of input / output circuit components each constituting a series impedance between input and output including an element having a first delay phase and an element having a first lead phase connected in parallel to each other, and the pair of input / output A second delayed phase element and a second advanced phase element connected in series with each other between the inter-circuit components, and a third connected between the pair of transmission lines and the ground potential, respectively. A differential transmission line comprising a shunt circuit component constituting a shunt admittance including an element having a leading phase of
A pair of conductor patterns extending in the input / output direction and parallel to each other, and a ground conductor adjacent to the pair of conductor patterns,
The pair of conducting and resting patterns respectively include an input side pattern portion disposed on the input side in the input / output direction, an output side pattern portion disposed on the output side in the input / output direction, the input side pattern portion, and It is formed narrower in the direction orthogonal to the input / output direction than the output side pattern portion, and has an intermediate connection pattern portion that connects the input side pattern portion and the output side pattern portion,
Between the pair of conductor patterns, an input side gap region in which the input side pattern portions are arranged to face both sides in the parallel direction, and an output in which the output side pattern portions are arranged to face both sides in the parallel direction. A side gap region is provided,
The element having the first delay phase and the element having the first lead element constituting the series impedance are configured such that the input side pattern portion and the output side pattern portion are input / output via the intermediate connection pattern portion. It consists of a pattern structure connected in the direction,
The element having the second delay phase and the element having the second lead phase constituting the shunt admittance are the input side pattern portion and the output side pattern portion of the pair of conductor patterns, and the pair of pairs. The structure in which the input side pattern portions belonging to the conductor patterns face each other with a gap in the parallel direction, and the output side pattern portions belonging to the pair of conductor patterns face each other in the parallel direction through the gap. Composed by structure,
A differential transmission line characterized by that. The input side pattern portion of the pair of conductor patterns protrudes from the main body portion toward the other input side pattern portion, and a narrower protrusion portion in the input / output direction than the main body portion. And the tips of the projecting portions face each other in the parallel direction through the input-side gap region,
The output side pattern portion includes a main body portion, and protrudes from the main body portion toward the other output side pattern portion, and has a narrower protrusion portion in the input / output direction than the main body portion, The tips of the protrusions face each other in the parallel direction through the output-side gap region.
The differential transmission line according to claim 1.   The differential transmission line according to claim 2, wherein the protrusion is formed in a T shape with a tip extended in the input / output direction.   The differential transmission line according to claim 1, wherein the pair of conductor patterns are laminated with the ground conductor via an insulating layer.   The differential transmission line according to claim 1, wherein the pair of conductor patterns are formed on the same plane.   The differential transmission line according to claim 1, wherein the pair of conductor patterns are stacked on each other via an insulating layer.