JP4952577B2 - Transmission line type noise filter, manufacturing method thereof, and printed circuit board - Google Patents

Description

  The present invention relates to a transmission line type filter as a power supply decoupling element effective for suppressing electromagnetic interference between circuits, a manufacturing method thereof, and a printed board including the transmission line type filter.

  Electromagnetic interference (EMI: Electro-Magnetic Interference) and electromagnetic interference of electronic devices are becoming more and more important problems as the speed and frequency of circuits increase. Particularly in recent years, digital circuits and analog circuits have been mixedly mounted, and the problem of electromagnetic interference between circuits has been attracting attention. For example, the high-frequency power leaking from the power supply terminal of the LSI has components over a wide frequency range from several kHz to several GHz, and causes electromagnetic interference between circuits and radiation interference (EMI) to other devices. It has been known. Encapsulating such high-frequency power in or near an LSI that is a generation source is considered as one means for reducing electromagnetic interference problems and realizing stable operation of a circuit. As an example of the means, an element for power supply decoupling that functions in a wide band has been proposed.

  The element for power supply decoupling is an element for enclosing high-frequency power generated by switching of an electronic circuit such as an LSI in the vicinity of the generation source so as not to propagate to a wide range of a mounting board such as a printed circuit board. Conventionally, noise filters such as capacitors have been used as such power supply decoupling elements.

  However, the development of noise filters for power supply decoupling that can cope with the widening and high frequency of noise frequency accompanying the increase in the speed of digital circuits has been delayed, especially in capacitors because of their self-resonance phenomenon. It was difficult to maintain up to the high frequency region. Therefore, the conventional power supply decoupling element using a noise filter is currently combined with a plurality of noise filters in order to remove broadband noise. However, this has a problem in that a plurality of different types of noise filters are installed, which increases the mounting area and the cost.

In order to solve these problems, transmission line type noise filters using a transmission line structure have been proposed (see, for example, Patent Documents 1 to 4). These transmission line type noise filters use a phenomenon that electromagnetic waves are reflected when impedance changes when impedance elements having different characteristic impedances are connected. That is, in these transmission line type noise filters, the generated noise is reflected by the filter and confined in the vicinity of the LSI by lowering the characteristic impedance and increasing the difference from the impedance of the wiring (impedance mismatching).
JP 2002-164760 A Japanese Patent Laid-Open No. 2003-101311 JP 2002-335107 A JP 2004-15706 A Japanese Patent Laid-Open No. 5-347501

  By the way, in a finite-length transmission line, a resonance phenomenon occurs due to the influence of multiple reflection or the like inside the transmission line at a frequency at which the length of the line is halved with respect to the wavelength of the electromagnetic wave in the transmission line. In the vicinity of this resonance frequency, the input impedance of the transmission line type noise filter increases, so that the difference between the impedance of the noise filter and the impedance of the wiring (impedance mismatching) decreases, and the reflection of electromagnetic waves on the transmission line decreases. Therefore, the transmission line type noise filter described in each of the above patent documents has a problem that the effect as a noise filter is reduced in the vicinity of the self-resonant frequency depending on the length of the filter.

  In the transmission line type noise filter, the electromagnetic wave entering the filter is converted into heat by dielectric loss to reduce the influence of resonance due to multiple reflection, and as a result, noise is reduced. However, in order to reduce noise that has entered the noise filter using dielectric loss, it is important to set the dielectric loss to an appropriate value. When the dielectric loss is too large, the characteristic impedance of the noise filter is increased and impedance mismatching is reduced, so that the characteristics as a transmission line type noise filter are deteriorated. In addition, when the dielectric loss is small, the conversion to heat due to the dielectric loss does not work sufficiently, and the influence of resonance due to multiple reflection cannot be reduced. For such a problem, it is sufficient that the dielectric loss can be easily controlled. However, since the dielectric loss is determined by the material of the dielectric, there is a problem that the options for controlling the dielectric loss are narrow.

  The present invention has been made in view of such a problem, and is a transmission line type filter as a power supply decoupling element effective for suppressing electromagnetic interference between circuits, which suppresses resonance, and is contained inside the filter. To provide a transmission line type filter capable of effectively losing noise that has entered and adjusting a loss corresponding to a dielectric loss as a transmission line, a manufacturing method thereof, and a printed circuit board including the transmission line type filter. Objective.

  A transmission line type filter according to the present invention is a transmission line type filter having a dielectric layer and a resistance layer between electrically opposing conductors, and having a circular or rectangular cross-sectional shape, When the characteristic impedance when the resistance layer at the resonance frequency is a conductor is Zo and the length of the transmission line is L, the conductance value Gc per unit length of the resistance layer satisfies the relationship of the following formula 1. It is characterized by that. Hereinafter, this transmission line type filter is referred to as “transmission line type filter A”.

  According to the present invention, in a transmission line type filter having a structure in which a dielectric layer and a resistance layer are provided between electrically opposed conductors, the conductance value per unit length of the resistance layer is expressed by the relationship of Equation 1 above. Since it is configured to satisfy, the resistance layer acts to increase the filter effect of the electromagnetic wave in the transmission line and to suppress the resonance depending on the length of the filter element. As a result, the transmission line type filter of the present invention having the resistance layer satisfying the relationship of the above formula 1 can be used as a power supply decoupling element effective for suppressing electromagnetic interference between circuits, and enters the inside of the filter. Noise can be effectively lost.

  In the present invention, the transmission line type filter A has (1) a structure having one dielectric layer and one resistance layer between the conductors, and (2) two dielectric layers between the conductors. And one resistive layer, the resistive layer being positioned between the two dielectric layers, and (3) having one dielectric layer and two resistive layers between the conductors The dielectric layer may be positioned between the two resistance layers.

  According to the inventions of the above (1) to (3), any of them is composed of a structure having a dielectric layer and a resistance layer satisfying the relationship of the above formula 1 between electrically opposed conductors. The transmission line type filter of the present invention having the configuration can be used as a power supply decoupling element effective in suppressing electromagnetic interference between circuits, and can effectively lose noise entering the filter.

  Further, the present invention may be configured such that, in the transmission line type filter A, the electrically opposed conductors are a central conductor and an external conductor disposed so as to surround the outside of the central conductor. it can. According to the present invention, when the cross-sectional shape is rectangular, a shield strip type transmission line type filter can be obtained, and when the cross-sectional shape is circular, a coaxial transmission line type filter can be obtained.

  Further, the present invention is the transmission line type filter A, wherein the electrically opposing conductor is a signal conductor located in the center, and a ground conductor disposed so as to be sandwiched from above and below the signal conductor, The resistance layer may be formed on the signal conductor so as to surround the signal conductor. According to the present invention, the conductor is constituted by the signal conductor located at the center and the ground conductor disposed so as to be sandwiched from above and below the signal conductor, and the resistance layer is formed so as to surround the signal conductor. Therefore, it can be a strip transmission line type filter.

  Further, the present invention may be configured such that in the transmission line type filter A, the electrically opposed conductors are a flat lower conductor and an upper conductor disposed to face the lower conductor. it can. According to the present invention, since the conductor is constituted by the flat lower conductor and the upper conductor disposed above the lower conductor, a parallel plate type transmission line type filter can be obtained.

  According to the present invention, in each of the transmission line type filters, the conductivity of the resistance layer is preferably 1/100 or less of the conductivity of the conductor. According to the present invention, since the conductivity of the resistance layer is sufficiently small, that is, 1/100 or less of the conductivity of the conductor, the current flowing along the conductor and the resistance layer in the filter almost passes through the conductor. Therefore, the presence of the resistance layer hardly affects the impedance of the conductor, and the resistance layer enters in series with the admittance of the dielectric layer in terms of an equivalent circuit. Therefore, when the frequency is low such that ωC << Gc. Has almost no influence of the resistance layer, exhibits the characteristics of a conventional transmission line type filter, and when ωC is much larger than Gc, that is, when the frequency is high such that ωC >> Gc, the resistance layer is the transmission line. In the vicinity of the frequency at which resonance occurs, ωC is much smaller than Gc, that is, ωC << Gc is satisfied, and ωC is much larger than Gc, that is, ωC >>. Resonance of the filter can be suppressed by setting Gc to change to a condition that satisfies Gc. Here, ω represents an angular frequency, and C represents a capacitance per unit length of the transmission line type filter.

  According to the present invention, in each of the transmission line type filters described above, the resistance layer is preferably formed of a carbon material, a conductive polymer material, a solid electrolyte, a liquid electrolyte, a low resistance alloy, or a semiconductor material. In the transmission line type filter of the present invention, the resistive layer may be a laminated resistive layer composed of two or more layers.

  A method for manufacturing a transmission line type filter according to the present invention is a method for manufacturing a transmission line type filter according to the present invention having a dielectric layer and a resistance layer between electrically opposed conductors, the method comprising: Forming a dielectric layer, forming a resistance layer composed of two or more layers so as to cover the dielectric layer, and forming an external conductor on the resistance layer, The resistance layer composed of two or more layers is a laminate of conductive polymer layers formed by different polymerization methods. In this manufacturing method, the step of forming a resistance layer composed of two or more layers includes a first step of forming a conductive polymer layer by chemical oxidative polymerization, and a high conductivity by electrolytic polymerization after the first step. It is preferable to have a second step of forming a molecular layer.

  In addition, a method for manufacturing a transmission line type filter according to another aspect of the present invention includes a transmission line type filter according to the present invention having a dielectric layer and a resistance layer between electrically opposed conductors and having a circular cross-sectional shape. A method of manufacturing, comprising the steps of plating a resistance material on the inner and outer surfaces of a cylindrical dielectric to form two resistance layers, and plating a conductive material on the two resistance layers to provide a conductor And a step of forming.

  A method for manufacturing a transmission line type filter according to still another aspect of the present invention is a method for manufacturing a transmission line type filter according to the present invention having a dielectric layer and a resistance layer between electrically opposing conductors. Forming an oxide film as a dielectric layer on the inner surface of the outer conductor made of valve metal, forming an oxide film as a dielectric layer on the outer surface of the central conductor made of valve metal, and forming an oxide film And injecting an electrolyte as a resistance layer between the outer conductor and the inner conductor.

  Furthermore, the printed circuit board according to the present invention is a printed circuit board on which the transmission line type filter of the present invention is mounted, wherein the transmission line type filter is installed between the power supply wiring and the LSI power supply wiring. Features. At this time, one of the central conductor and the outer conductor constituting the transmission line type filter connects the power supply wiring and the LSI power supply wiring, and the other one is connected to the ground wiring.

  According to the transmission line type filter of the present invention, the resistance layer provided between the dielectric layer and the conductor acts so as to suppress the resonance of the electromagnetic wave in the transmission line, and depends on the length of the filter element. It acts to suppress resonance. As a result, the transmission line type filter of the present invention having the resistance layer satisfying the relationship of the above formula 1 can be used as a power supply decoupling element effective for suppressing electromagnetic interference between circuits, and enters the inside of the filter. Noise can be effectively lost.

  In addition, according to the transmission line type filter of the present invention, the resistance of the resistance layer is sufficiently small, that is, 1/100 or less of the conductivity of the conductor, and the current flowing along the conductor and the resistance layer in the filter hardly passes the conductor. Therefore, the presence of the resistance layer hardly affects the impedance of the conductor, and the resistance layer is put in series with the admittance of the dielectric layer in terms of an equivalent circuit. As a result, there is almost no influence of the resistance layer at the low frequency where ωC << Gc, and the characteristics of the conventional transmission line type filter are exhibited, and at the high frequency where ωC >> Gc, the resistance layer Absorbs noise flowing in the transmission line, and near the frequency at which resonance occurs, Gc changes from the condition where ωC << Gc is satisfied to the condition where ωC >> Gc is satisfied. Can be suppressed.

  In addition, according to the method for manufacturing a transmission line type filter of the present invention, the transmission line type filter of the present invention having the above-described effects can be easily manufactured.

  Further, according to the printed circuit board of the present invention, the LSI and the power source are separated through the transmission line type filter of the present invention, so that noise superimposed on the power line is applied to the transmission line type noise filter of the present invention. As a result, the noise that enters the transmission line type noise filter 251 is reflected or absorbed by the transmission line type noise filter and does not propagate to the power supply circuit side. Thereby, noise does not propagate to other LSIs connected to the same power supply circuit, and the problem of unnecessary electromagnetic waves caused by radiation from the power supply wiring can be solved.

1 is a schematic perspective view showing a first embodiment of a transmission line type filter of the present invention. It is a schematic diagram which shows the equivalent circuit in the micro area of a general transmission line. It is a schematic diagram which shows the equivalent circuit in the micro area of the transmission line type noise filter of FIG. It is a graph which shows electric power transmission characteristic S21 when a in Formula 12 is changed. It is a graph which shows the experimental example of electric power transmission characteristic S21 of the transmission line type filter of this invention. It is a schematic cross section which shows 2nd Embodiment of the transmission line type filter of this invention. It is a schematic cross section which shows 3rd Embodiment of the transmission line type filter of this invention. It is a schematic cross section which shows 4th Embodiment of the transmission line type filter of this invention. It is a model perspective view which shows 5th Embodiment of the transmission line type filter of this invention. It is a model perspective view which shows 6th Embodiment of the transmission line type filter of this invention. It is a model perspective view which shows 7th Embodiment of the transmission line type filter of this invention. It is a perspective view of a general shield stripline type device. It is A-A 'longitudinal cross-sectional view of the shield stripline type | mold element shown in FIG. FIG. 13 is a B-B ′ longitudinal sectional view of the shield stripline element shown in FIG. 12. It is a sectional view showing an example of a transmission line type filter concerning the present invention which inserted a resistance layer. It is sectional drawing from the other direction of the transmission line type filter of FIG. 1 is a cross-sectional view illustrating a shield stripline element of Example 1. FIG. It is sectional drawing from the other direction of the shield stripline type | mold element of FIG. It is a block diagram when measuring the power transmission characteristic of a transmission line. It is a measurement result of the electric power transmission characteristic of the shield stripline type | mold element of Example 1. FIG. It is a block diagram which measures by connecting the shield stripline type | mold element of Example 1 to a network analyzer. 6 is a perspective view showing a coaxial ceramic coaxial line type noise filter of Example 2. FIG. It is C-C 'sectional drawing of the ceramic coaxial line type noise filter of FIG. It is D-D 'sectional drawing of the ceramic coaxial line type noise filter of FIG. It is a circuit diagram which shows an example in the case of performing power supply decoupling. It is sectional drawing of the printed circuit board which concerns on this invention after mounting | wearing with a transmission line type | mold filter. It is a top view of the printed circuit board concerning the present invention after mounting a transmission line type filter. It is sectional drawing of the board | substrate before mounting | wearing with a transmission line type filter.

Explanation of symbols

10, 20, 30, 60, 70, 80, 90, 100, 110, 120, 130, 170 Transmission line type filters 11, 61, 71, 81, 91, 101, 111, 131, 171 Center conductors 12, 62, 72, 82, 92, 102, 112a, 112b, 132, 172 Outer conductors 13, 63, 73, 83a, 83b, 93, 103, 113, 133, 173 Dielectric layers 14, 64, 74a, 74b, 84, 94 , 104, 114, 134, 174 Resistive layer 21, 31 Conductor resistance in minute section equivalent circuit 22, 32 Conductor inductance in minute section equivalent circuit 23, 33 Conductance of dielectric layer in minute section equivalent circuit 24, 34 Minute section Capacitance of the dielectric layer in the equivalent circuit 35 Ductance 105 Hollow portion 121 Anode terminal 122 Cathode terminal 123 Mold resin 174a, 174b Conductive polymer layer 174c Carbon paste layer 176 Mask 220 Transmission line type filter 221 Anode conductor 222 Cathode conductor 223 Dielectric layer 224 Resistance layer 225 Mask

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. A transmission line type noise filter according to the present invention is a transmission line type filter having a dielectric layer and a resistance layer between electrically opposed conductors and having a circular or rectangular cross-sectional shape, the transmission line type filter When the characteristic impedance at the resonance frequency is Zo and the length of the transmission line is L, the conductance value Gc per unit length of the resistance layer satisfies the relationship of the formula 1. Yes. In other words, a transmission line type filter having a dielectric layer between electrically opposing conductors and having a circular or rectangular cross-sectional shape, where Zo is the characteristic impedance at the resonance frequency of the transmission line type filter, and the transmission line When the length of L is defined as L, the conductance value Gc per unit length of the resistance layer provided between the conductors satisfies the relationship of the formula 1. The conductance value Gc per unit length of the resistance layer is defined as S (Siemens) / m or 1 / Ωm. Further, since the characteristic impedance Zo has frequency characteristics, the characteristic impedance Zo is at the resonance frequency.

  The present invention is a transmission line type filter having a structure having a dielectric layer and a resistance layer between electrically opposing conductors, and the conductance value per unit length of the resistance layer satisfies the relationship of the above formula 1. Thus, the resistance layer acts to increase the filter effect of the electromagnetic wave in the transmission line and to suppress the resonance depending on the length of the filter element. As a result, the transmission line type filter of the present invention having the resistance layer satisfying the relationship of the above formula 1 can be used as a power supply decoupling element effective for suppressing electromagnetic interference between circuits, and enters the inside of the filter. Noise can be effectively lost.

  Hereinafter, the transmission line type noise filter of the present invention that exhibits the above-described effects will be described in detail with reference to the drawings as necessary.

(First embodiment)
FIG. 1 is a schematic perspective view showing a first embodiment of a transmission line type filter of the present invention. A transmission line type filter 10 shown in FIG. 1 is a shield stripline type noise filter, and a center conductor is interposed between a center conductor 11 and an outer conductor 12 arranged so as to surround the outside of the center conductor 11. A dielectric layer 13 and a resistance layer 14 are sequentially formed from the side. That is, the transmission line type filter 10 includes a center conductor 11, a dielectric layer 13 formed around the center conductor 11, a resistance layer 14 formed around the dielectric layer 13, and the resistance layer 14 And an outer conductor 12 formed around the outer periphery.

(Transmission line characteristics)
Here, the characteristics of the transmission line in the transmission line type filter of the present invention will be considered based on a minute section equivalent circuit.

  First, a minute section equivalent circuit in a general transmission line will be described. FIG. 2 is a schematic diagram showing an equivalent circuit in a minute section of a general transmission line having a dielectric layer between electrically opposing conductors. More specifically, it is a schematic diagram showing an equivalent circuit of a transmission line type filter having a configuration in which a resistance layer is removed from the transmission line type filter having the configuration shown in FIG. The equivalent circuit 20 is obtained by dividing a transmission line into minute sections (length Δx) and expressing the minute sections with resistance, inductance, conductance, and capacitance. The resistance per unit length is R, the inductance is L, the conductance is G, and the capacitance is C. As shown in FIG. 2, R · Δx, L · Δx, G · Δx, C · It is assumed that Δx is infinitely arranged, and represents resistance, inductance, conductance, and capacitance that exist in a distributed manner on the transmission line. By doing so, the characteristics as a transmission line can be expressed.

  The characteristic of a general transmission line is represented by a characteristic impedance Zo and a propagation constant γ. The characteristic impedance Zo represents the ratio of voltage and current flowing in the transmission line, and the propagation constant γ represents the loss and phase velocity in the transmission line. The characteristic impedance Zo and the propagation constant γ are expressed by the following formula 2 when the impedance entering in series with the line A in FIG. 2 is Z and the admittance entering in parallel with the line B in FIG. It becomes like this.

Further, the characteristics of the filter can be evaluated by the S ₂₁ parameter which is a power transmission characteristic. The power transmission characteristic S ₂₁ of the transmission line is expressed by the following Equation 3 by the characteristic impedance Z _{o of} the transmission line, the propagation constant γ, the length l of the transmission line, and the characteristic impedance Z _L of the wiring connected to the filter. .

  The filter characteristics of the transmission line are deteriorated by the resonance of the transmission line, and this resonance can be suppressed by increasing the loss of the transmission line represented by the real part of the propagation constant γ. Generally, the loss of the transmission line is affected by the resistance 21 and the conductance 23. By increasing the resistance 21 and the conductance 23, the loss in the transmission line can be increased. However, when the resistance 21 and the conductance 23 are increased, the loss of direct current and low frequency power that should be passed through increases and cannot be used as an element inserted into the power line. Therefore, it is desirable that the noise filter inserted into the power supply circuit has a small loss at a direct current and a low frequency and an increase at a frequency at which transmission line resonance occurs.

  FIG. 3 is a schematic diagram showing an equivalent circuit in a minute section of the transmission line type noise filter of FIG. This equivalent circuit 30 is an equivalent circuit in which the conductance 35 of the resistance layer is placed in series with the capacitance 34 and the conductance 33 of the dielectric because the resistance layer 14 having the form shown in FIG. The transmission line type filter 10 of FIG. 1 shows such an equivalent circuit 30 because the conductivity of the resistance layer 14 is sufficiently smaller than the conductivity of the conductors (the central conductor 11 and the outer conductor 12). At this time, since the current flowing through the transmission line almost passes through the conductor, the resistance layer hardly affects the impedance Z of the portion A shown in FIG. 2, and the dielectric corresponding to the portion B shown in FIG. The admittance Y enters the series. Therefore, the admittance Y entering the transmission line in parallel is expressed as the following Equation 4.

  In the transmission line filter 10 of FIG. 1 represented by the equivalent circuit 30 of FIG. 3, the conductance G is a very small value of 10 −6 or less. Therefore, in the frequency band in which the transmission line filter is used, ωC >> G, and the term of G can be ignored. Therefore, in the transmission line filter, only the relationship between the conductance value Gc per unit length of the resistance layer and the capacitance C needs to be considered. In the above equation 4, when Gc >> ωC, equation 4 can be approximated as Y = jωC, but this approximate equation is the same as the case of a general transmission line filter. Therefore, in the frequency region where Gc >> ωC, the same characteristics as a general transmission line filter are exhibited.

  On the other hand, in the above formula 4, when Gc << ωC, the formula 4 can be approximated as Y = Gc. At this time, the propagation constant γ of the transmission line is as shown in Equation 5 below.

  The real part of the propagation constant γ represents the transmission line loss. Therefore, in the case of Gc << ωC, the loss increases as the frequency increases. As the loss inside the transmission line increases, the effect as a filter increases. However, in the case of Gc << ωC, there are also the following problems, for example. The characteristic impedance Zo of the transmission line type filter having resistance is expressed by the following formula 6.

  The transmission line type filter can reflect an electromagnetic wave due to mismatching impedance by setting the characteristic impedance ZL of the wiring to ZL >> Zo, and can exhibit a filter effect. However, when Gc << ωC, the characteristic impedance Zo at the resonance frequency of the transmission line type filter is increased as compared with the case where there is no admittance of the resistance layer. Therefore, impedance mismatch between Zo and ZL is reduced, and as a result, the filter effect due to reflection is reduced.

  By the way, the relationship between Gc and ωC changes with the angular frequency ω. When the frequency is low, Gc >> ωC, and when the frequency is high, Gc << ωC. Therefore, the transmission line type filter changes from a transmission line characteristic having no loss to a transmission line characteristic having a large loss in the transmission line as the frequency increases.

  Here, a case is considered where Gc is set so as to satisfy the condition of Gc >> ωC at the direct current and low frequency, and to change to the condition of Gc << ωC near the resonance frequency. When Gc is set in this way, the characteristics of a transmission line type filter having a resistance layer (see FIG. 1) show the characteristics of a conventional transmission line type filter at DC and low frequencies, and the resonance of the transmission line is At the generated frequency, the loss is increased and the resonance is suppressed. That is, resonance can be suppressed by increasing high-frequency loss without increasing DC and low-frequency loss. Therefore, the filter characteristic can be improved by putting a resistance layer in the transmission line type filter and setting the conductance value Gc of the resistance layer to an appropriate value.

  Therefore, an appropriate conductance value Gc is obtained. Here, since it suffices to change to a condition of Gc << ωC in the vicinity of the angular frequency ωo at the time of resonance, Gc that satisfies Gc = ωC at the resonance frequency ωo is considered as a reference. C is expressed by the following equation from the characteristic impedance Zo and the propagation constant γ.

  However, im (x) is an imaginary coefficient of x and is represented by the following formula 8.

  Therefore, Gc is expressed by the following formula 9.

  Here, when the transmission line length is 1 and the resonance frequency is ω0, the condition expressed by the following formula 10 is satisfied.

  Substituting this equation into Equation 9 gives the following Equation 11.

  Here, in a normal transmission line type filter having a dielectric layer between electrically opposed conductors (that is, a transmission line type filter constituting the equivalent circuit shown in FIG. 2), im (Z0) ≈0. . Accordingly, the reference Gc is expressed by the following formula 12. When im (Z0) ≈0, the previous expression of Expression 12 is obtained, and otherwise Gc is a constant a times as shown in the subsequent expression of Expression 12.

  Here, an optimum value was obtained by changing an arbitrary constant a in the above formula 12. The power transmission characteristic S21 was evaluated from the formulas 2 and 3. FIG. 4 shows the power transmission characteristic S21 when a is changed. As can be seen from the results of FIG. 4, it was found that the characteristics of the transmission line filter were improved in the range of 0.05 ≦ a ≦ 5. Therefore, the optimum conductance value Gc is in the range expressed by Equation 1.

  When the conductance value Gc per unit length of the resistance layer 14 in FIG. 1 is set so as to satisfy the relationship of Equation 1, the filter characteristic is a conductance 35 rather than an influence of the capacitance 34 when the transmission line approaches the resonance frequency. (Gc >> ωC). For this reason, when approaching the resonance frequency, the characteristics of the transmission line having a large conductance are approached, and the loss of the transmission line rapidly increases. On the other hand, at a frequency sufficiently lower than the resonance frequency, the influence of the conductance 35 is sufficiently smaller than the influence of the capacitance 34 (Gc << ωC), so that the filter characteristics greatly affect the impedance as the transmission line. Therefore, the conventional characteristics can be maintained. Therefore, at a low frequency, the characteristics of the conventional transmission line type noise filter can be maintained, and the loss of the noise filter can be increased as the resonance frequency of the noise filter is approached. As a result, the transmission line type filter according to the present invention prevents the resonance and becomes a noise filter having higher cutoff characteristics.

  FIG. 5 is a graph showing an experimental example of the power transmission characteristic S21 of the transmission line type filter of the present invention. The power transmission characteristic S21 of FIG. 5 is calculated assuming that the characteristic impedance Zo is 0.1Ω, the line length L is 3 cm, the wavelength shortening rate is 1/30, and the coefficient of Equation 1 is 1 (a in Equation 12 is 0.5). It is obtained by this. In FIG. 5, a curve 51 is the power transmission characteristic S21 when the conductance value Gc is 0, and a curve 52 is the power transmission characteristic S21 when the conductance value Gc = 1 × π / (L × Zo). Compared with the power transmission characteristic (curve 51) in the transmission line without loss, the power transmission characteristic (curve in the transmission line when the conductance value Gc is 1 × π / (L × Zo) by inserting an appropriate resistance layer 52) shows almost the same characteristics at a frequency (point P) up to 1/4 of the resonance frequency in the transmission line without loss, and resonance is lost at 1/4 or more of the resonance frequency, and shows high cutoff. It was confirmed that The transmission line type filter of the present invention having such a power transmission characteristic S21 can increase the cutoff performance logarithmically as the frequency increases, and can adjust the loss by adjusting the resistance layer.

  The resonance of the transmission line can be suppressed by adjusting the dielectric loss and adjusting the resistance of the conductor. However, when the resistance of the conductor is adjusted, there is a problem that the loss of DC power increases. In particular, the power supply decoupling element inserted into the power supply needs to have little loss of DC power, and therefore the resistance of the conductor cannot be adjusted practically. On the other hand, since the dielectric loss is determined by the material and manufacturing method of the dielectric, in order to adjust the dielectric loss, it is necessary to change the material or the manufacturing method and cannot be easily controlled. In particular, when aluminum is used for the conductor and aluminum oxide is used for the dielectric as disclosed in Japanese Patent Application Laid-Open No. 2003-101311, the dielectric is formed by oxidizing the conductor. I can't. However, the adjustment by the resistance layer as in the present invention can be performed relatively easily. For example, the conductance of the resistance layer can be easily adjusted by adjusting the thickness of the resistance layer.

  Here, the resonance frequency will be briefly described. The resonance frequency is determined by the transmission line length l and the imaginary part (wavelength compression ratio) of the propagation constant γ. Resonance occurs when the time t during which an electromagnetic wave reciprocates in the transmission line coincides with 1 / f, which is a fraction of the frequency of the electromagnetic wave. Electromagnetic waves that enter from one end of the transmission line are reflected back at the other end. When the returned electromagnetic wave and the incoming electromagnetic wave are in phase, the electromagnetic waves in the transmission line are strengthened and resonance occurs. If 1 / f and the round-trip time t coincide with each other, the phases naturally coincide with each other. If this is expressed in terms of wavelength, half of the wavelength of the electromagnetic wave passing through the transmission line coincides with the length of the transmission line. The electromagnetic wave travels at a speed of light c in vacuum, but inside the dielectric, it has a speed that is a fraction of the wavelength compression ratio determined by the dielectric constant and permeability of the dielectric. From these, when the formula is established, the condition of the above formula 9 is satisfied. When the loss is 0, the above formula 10 is substituted into the above formula 3 to obtain 1. That is, when resonating, the electromagnetic wave travels through the entire transmission line. In addition, when the loss in the transmission line is large, the electromagnetic wave is lost before it is reflected and returned, so that the returned electromagnetic wave and the incoming electromagnetic wave do not intensify, so that resonance is suppressed.

(Second to seventh embodiments)
FIG. 6 is a schematic cross-sectional view showing a second embodiment of the transmission line type filter of the present invention. A transmission line type filter 60 shown in FIG. 6 is a shield stripline type noise filter, and a center line between a center conductor 61 and an outer conductor 62 arranged so as to surround the outside of the center conductor 61. A resistance layer 64 and a dielectric layer 63 are formed in this order from the conductor side. That is, the transmission line type filter 60 includes a center conductor 61, a resistance layer 64 formed around the center conductor 61, a dielectric layer 63 formed around the resistance layer 64, and the dielectric layer 63. And an outer conductor 62 formed around the outer periphery.

  FIG. 7 is a schematic cross-sectional view showing a third embodiment of the transmission line type filter of the present invention. A transmission line type filter 70 shown in FIG. 7 is a shield stripline type noise filter, and a center line between a center conductor 71 and an outer conductor 72 arranged so as to surround the outside of the center conductor 71. A resistance layer 74a, a dielectric layer 73, and a resistance layer 74b are formed in this order from the conductor side. That is, the transmission line type filter 70 includes a center conductor 71, a resistance layer 74a formed around the center conductor 71, a dielectric layer 73 formed around the resistance layer 74a, and the dielectric layer 73. A resistance layer 74b formed around the resistance layer 74b and an outer conductor 72 formed around the resistance layer 74b. The transmission line type filter 70 includes a step of plating a resistance material on the inner surface and the outer surface of a cylindrical dielectric (dielectric layer 73) to form two resistance layers (resistance layer 74a and resistance layer 74b). And a method of forming a conductor (a central conductor 71 and an outer conductor 72) by plating a conductive material on the two resistance layers (the resistance layer 74a and the resistance layer 74b).

  Since the transmission line type filter 70 can be manufactured by forming the resistance layers 74a and 74b on the dielectric layer 73 by means of plating or the like, it is effective in terms of productivity. Specifically, first, a cylindrical dielectric (dielectric layer 73) is prepared, and then resistance layers 74a and 74b are formed on the inner and outer surfaces of the dielectric by plating, and then the resistance layer 74a. , 74b by forming the conductors 71, 72 by means of plating or the like, the transmission line type filter shown in FIG. 7 can be manufactured. In this case, the conductance value Gc of the resistance layers 74a and 74b can be adjusted by a value obtained by combining the two resistance layers 74a and 74b formed inside and outside the dielectric. The conductance value Gc is determined by [surface area of the resistance layers 74a and 74b] / [thickness of the resistance layers 74a and 74b] × [conductivity of the resistance layers 74a and 74b]. As the layer thickness increases, the surface area changes and must be determined by integration.

  FIG. 8 is a schematic sectional view showing a fourth embodiment of the transmission line type filter of the present invention. A transmission line type filter 80 shown in FIG. 8 is a shield stripline type noise filter, and a center line between a center conductor 81 and an outer conductor 82 arranged so as to surround the outside of the center conductor 81. A dielectric layer 83a, a resistance layer 84, and a dielectric layer 83b are formed in this order from the conductor side. That is, the transmission line type filter 80 includes a center conductor 81, a dielectric layer 83a formed around the center conductor 81, a resistance layer 84 formed around the dielectric layer 83a, and the resistance layer 84. A dielectric layer 83b formed around the outer periphery of the dielectric layer 83 and an outer conductor 82 formed around the dielectric body 83b.

  In this transmission line type filter 80, the two dielectric layers 83a and 83b may be formed of the same material, or may be formed of different materials. In addition, when the center conductor 81 and the outer conductor 82 are made of aluminum, the dielectric layers 83a and 83b adjacent to each conductor can be easily formed as an aluminum oxide film. The resistance layer 84 at this time can be formed of, for example, an electrolytic solution. As described above, by forming the polar elements in multiple layers, it is possible to realize nonpolarity without breaking even when a reverse bias is applied. In the fourth embodiment, a resistive layer is provided between polar elements. It can be realized by putting The transmission line type filter 80 includes a step of forming an oxide film as a dielectric layer 83b on the inner surface of the outer conductor 82 made of valve metal such as aluminum, and the outer surface of the central conductor 81 made of valve metal such as aluminum. And a step of injecting an electrolytic solution as the resistance layer 84 between the outer conductor 82 and the inner conductor 81 on which the oxide layer is formed, and a process of forming an oxide film as the dielectric layer 83a. .

  FIG. 9 is a schematic perspective view showing a fifth embodiment of the transmission line type filter of the present invention. The transmission line type filter 90 is a coaxial line type noise filter, and a dielectric is formed between the center conductor 91 and the outer conductor 92 disposed so as to surround the outside of the center conductor 91 from the center conductor side. The body layer 93 and the resistance layer 94 are formed in this order. That is, the transmission line type filter 90 includes a center conductor 91, a dielectric layer 93 formed around the center conductor 91, a resistance layer 94 formed around the dielectric layer 93, and the resistance layer 94. And an outer conductor 92 formed around the outer periphery.

  FIG. 10 is a schematic perspective view showing a sixth embodiment of the transmission line type filter of the present invention. This transmission line type filter 100 is a ceramic coaxial line type noise filter in which the central conductor 101 has a hollow portion 105, and other configurations are the coaxial line type of the fifth embodiment (see FIG. 9). This is the same as the noise filter 90. In this transmission line type filter 100, the central conductor 101 has a cylindrical shape having a hollow portion 105, and examples of the constituent material include metals, alloys such as copper, silver, nickel, tin, and gold. . The dielectric 103 formed around the central conductor 101 is made of a high dielectric insulating material, and is made of a ceramic material having a high dielectric constant such as calcium zirconate, barium titanate, magnesium titanate, or calcium stannate. It is formed.

  In such a ceramic coaxial line type transmission line type filter 100, a ceramic pipe having a hollow portion is prepared, a resistance layer 104 is formed on the outer peripheral surface of the ceramic pipe, and then the inner surface of the ceramic pipe and the resistance layer are plated. It can be manufactured by forming a conductor. The resistance layer 104 can be formed using a resistance paste.

  FIG. 11 is a schematic perspective view showing a seventh embodiment of the transmission line type filter of the present invention. The transmission line type filter 110 is a strip line type noise filter, and is composed of a signal conductor (center conductor) 111 and two flat ground conductors (external conductors) arranged so as to sandwich the signal conductor 111 from above and below. ) A resistance layer 114 and a dielectric layer 113 are formed in this order from the signal conductor side between 112a and 112b. That is, the transmission line type filter 110 includes a signal conductor 111, a resistance layer 114 formed around the signal conductor 111, a dielectric layer 113 formed around the resistance layer 114, and the dielectric layer 113. Have two flat ground conductors 112a and 112b arranged so as to be sandwiched from above and below.

(Description of each component)
Next, components of the above embodiments will be described.

  The center conductor and the outer conductor are desirably conductors with high conductivity (1,000,000 S / m or more) such as metals such as copper, silver, gold, aluminum, nickel, tin, and alloys thereof. Such a central conductor and an outer conductor can be formed by plating or the like. In order to use the transmission line type noise filter as a power supply decoupling element, it is necessary that the center conductor and the outer conductor can flow DC power efficiently. Therefore, it is preferable that the conductivity of the center conductor is as high as possible. The electrical conductivity of the center conductor and the outer conductor is preferably 1,000,000 S / m or more, because, when used as a power supply decoupling element, the loss of DC power due to the resistance of the center conductor and the outer conductor is reduced. This is because it needs to be reduced.

  Further, the center conductor and the outer conductor may be made of a valve metal (bubble metal). Examples of such a material include aluminum, aluminum alloy, tantalum, tantalum alloy, niobium, niobium alloy and the like. The valve metal can easily form an oxide film that is an insulator. The oxide film serves as a dielectric layer in the present invention.

  The dielectric layer can be an oxide film in which an oxide film is formed on the surface of the central conductor and / or the outer conductor. That is, by anodizing the surface of the center conductor and / or the outer conductor, an oxide film having an enlarged surface area of the center conductor and / or the outer conductor is formed, and this oxide film acts as a dielectric. Note that, as in the case of the sixth embodiment in FIG. 10, a ceramic pipe having a hollow portion 105 can also be used.

  The resistance layer is, for example, a carbon material, or a conductive polymer material such as polypyrrole, polythiophene, or polyaniline, or a solid electrolyte or liquid electrolyte, or a metal or alloy having low conductivity such as nickel, manganese, or chromium, or It is preferable to use a material whose conductivity is 1/100 or less of the conductivity of the conductor, such as a semiconductor such as silicon or gallium arsenide.

  In the transmission line type filter of the present invention, the resistance layer may be a laminated resistance layer composed of two or more layers. Various methods can be adopted as a method of forming two or more resistance layers, and examples thereof include a method of laminating a conductive polymer layer. In this case, the same material may be sufficient and a different material may be sufficient. Further, the same material may be laminated by different methods, or different materials may be laminated by the same method. As an example, as will be described later in Examples, after forming a conductive polymer layer by chemical oxidative polymerization, a conductive polymer layer can be formed and laminated by electrolytic polymerization.

  When the resistance layer is configured using a liquid electrolyte, water, ethylene glycol, ethylene glycol monomethyl ether, glycerin, γ-butyrolactone, N-methylformamide, or the like is used as a solvent, and boric acid, adipic acid, Mention may be made of maleic acid, benzoic acid, phthalic acid, salicylic acid, ammonia, triethylamine or tetramethylammonium hydroxide.

  The thickness of the resistance layer is determined from the width of the transmission line type noise filter element and the conductivity of the resistance layer so that a conductance value Gc satisfying the relationship of the above equation 1 can be realized. More specifically, the thickness of the resistance layer is obtained as follows.

  In the present invention, the resistance layer is made of a material having a conductivity of 1/100 or less of the conductivity of the conductor, so that the conductance value Gc per unit length of the resistance layer satisfies the relationship of the above equation 1, and the filter Most of the current flowing through the conductor will pass through the conductor. Therefore, the presence of the resistance layer hardly affects the impedance of the conductor, and the resistance layer enters in series with the admittance of the dielectric layer in terms of an equivalent circuit. Therefore, when the frequency is low such that ωC << Gc. Has almost no influence of the resistance layer, exhibits the characteristics of the conventional transmission line type filter, and absorbs the noise flowing through the transmission line at the high frequency where ωC >> Gc, Further, in the vicinity of the frequency at which resonance occurs, the resonance of the filter can be suppressed by changing Gc from the condition that satisfies ωC << Gc to the condition that satisfies ωC >> Gc.

  The conductance value Gc is generally determined by “resistance conductivity × resistance area / resistance thickness”. In the present invention, “conductivity of resistance layer (S / m) × peripheral length of resistance layer (m) × 1 (unit length) / thickness (m) = conductance value Gc (S / m)” Become. Here, since the perimeter of the resistance layer varies depending on the thickness (that is, the perimeter becomes longer as the resistance layer becomes thicker), the perimeter of the resistance layer is actually set to f (x) ( (Function of thickness x), ∫1 / (conductivity · f (x)) · dx = 1 / Gc. When the resistance layer is formed on the central conductor or the dielectric layer, the peripheral length of the resistance layer is expressed by the outer peripheral length of the central conductor or the dielectric layer. When the resistance layer is formed on the inner side, it is represented by the inner peripheral length of the outer conductor or the inner side length of the dielectric layer. When the resistance layer is formed as an intermediate layer, the thickness direction of the formed resistance layer It is expressed by the perimeter passing through the center of.

  As an example, a mathematical expression when a resistance layer is provided on the outer periphery of a dielectric layer in a cylindrical shape like the coaxial line type noise filter shown in FIG. 9 and FIG. When the outer radius of the dielectric layer is r, the conductivity of the resistive layer is σ, the outer radius of the resistive layer is R, and the peripheral length of the resistive layer is a function f, the thickness d of the resistive layer is as follows: become.

  As described above, the thickness of the resistance layer can be obtained relatively easily if the cross-sectional structure is simple like a cylinder, but if the cross-sectional structure becomes complicated by etching or the like, it can be obtained by a simple formula. Not. However, if it is assumed that the resistance layer is thin and the outer periphery does not change regardless of the thickness of the resistance layer, it can be obtained by “conductivity × peripheral length / thickness = conductance value Gc”. In many cases, the thickness of the resistive layer is sufficiently thin and can be determined by this equation.

  In the transmission line type noise filter of the present invention, when the characteristic impedance at the resonance frequency of the transmission line type noise filter is Zo and the length of the transmission line is L, the conductance value Gc per unit length of the resistance layer. Is configured so as to satisfy the relationship of Equation 1 above. In the present invention, it is desirable that the conductance value Gc per unit length of the resistance layer is set to the value of the following formula 14.

  The characteristic impedance Zo at the resonance frequency can be obtained from simulation, an approximate expression, and measurement. From the value of the characteristic impedance Zo at the obtained resonance frequency and the length L of the transmission line portion of the noise filter, the above formula 1 Is used to determine the conductance value Gc per unit length of the resistance layer.

  The characteristic impedance Zo can be obtained from simulation, an approximate expression, or measurement, and the unit length of the resistance layer using the above expression 1 based on the obtained characteristic impedance Zo and the length L of the transmission line portion of the noise filter. The per conductance value Gc is determined. A specific procedure will be described with an example of a shield stripline element.

  FIG. 12 is a perspective view of a general shield stripline element, FIG. 13 is an A-A ′ longitudinal sectional view thereof, and FIG. 14 is a B-B ′ longitudinal sectional view thereof. First, the characteristic impedance Zo is obtained. The characteristic impedance Zo of the shield stripline element can be obtained from a cross-sectional structure (cross-sectional view shown in FIG. 14) perpendicular to the direction in which the electromagnetic wave of the transmission line propagates. At this time, the characteristic impedance Zo to be obtained is obtained in a state before the resistance layer is inserted. That is, it is obtained in a state where the inside and outside of the dielectric layer 133 are conductors (the center conductor 131 and the outer conductor 132). Here, in the case of the shield strip line illustrated in FIGS. 12 to 14, since the thickness d of the dielectric layer 133 is very small, the influence of corners is sufficiently small, and the central conductor 131 is processed by etching or the like. If not, the peripheral length t of the dielectric layer 133 = (w1 + w2) / 2 × 2 + (h1 + h2) / 2 × 2 (considering the average of the inner and outer peripheries), and the dielectric The following equation 15 is obtained from the dielectric constant ε of the body layer 133 and the magnetic permeability μ of the dielectric layer 133.

  The obtained characteristic impedance Zo and transmission line length L (L in FIG. 13) are substituted into Equation 1, and the conductance value Gc of the resistance layer to be inserted is calculated. From the calculated minimum value GcL and maximum value GcH of the conductance value Gc, the resistance layer having the target conductance value Gc becomes the resistance layer to be inserted into the transmission line type filter of the present invention.

Next, from the electrical conductivity ρ of the resistance layer and its cross-sectional structure, the required structure of the resistance layer is obtained by calculation,
A resistance layer is inserted between the conductor (the center conductor 131 or the outer conductor 132) and the dielectric layer 133. At this time, it is desirable to insert a resistive layer so as not to change the shape of the dielectric layer 133. Therefore, the shape of the conductor (the central conductor 131 or the outer conductor 132) is partially changed. Considering the case where a resistance layer is provided on the outer periphery of the dielectric layer 133, the resistance layer has a shape covering the dielectric layer 133, and thus the parameter that can be changed is the thickness of the resistance layer. Therefore, the thickness for realizing the resistance layer having the desired conductance value is obtained. Here, it is assumed that the thickness of the resistance layer is sufficiently smaller than the width w2 of the dielectric layer 133 and the influence of the corners is little. At this time, the following Expression 16 can be constructed from the outer peripheral length of the dielectric layer 133 (t2 = w2 × 2 + h2 × 2) and the conductivity σ of the resistance layer.

  From these equations, the thickness of the target resistance layer is obtained, and the resistance layer is inserted between the outer conductor 132 and the dielectric layer 133. 15 and 16 are cross-sectional views illustrating an example of a transmission line type filter according to the present invention in which a resistance layer 134 is inserted. Thus, a transmission line type noise filter having a resistance layer can be configured.

  Next, the transmission line type noise filter of the embodiment specifically manufactured to demonstrate the effect of the present invention will be described in detail.

Example 1
A solid electric field capacitor type shield stripline element having a cross-sectional structure shown in FIG. 17 was produced. FIG. 18 is a sectional view of the side surface. The appearance of this shield stripline element is the same as in FIG. The shield stripline element 170 according to the first embodiment includes a center conductor 171, a dielectric 173 formed around the center conductor 171, and a resistance layer 174 (conductive polymer layer 174a) formed around the dielectric 173. , 174b), a conductive carbon paste layer 174c formed around the resistance layer 174 and functioning as an adhesive layer, and an outer conductor 172 formed around the conductive carbon paste layer 174c.

  A method for manufacturing the shield stripline element of Example 1 will be described in order. In this embodiment, there are a step of forming a dielectric layer on the central conductor, a step of forming a two-layer resistance layer so as to cover the dielectric layer, and a step of forming an external conductor on the resistance layer. And the resistance layer which consists of the two layers is formed with a different polymerization method, and the conductive polymer layer is laminated | stacked. More specifically, first, rectangular aluminum was used as the center conductor 121. Next, the surface of the center conductor 171 was etched to increase the surface area. In the etching process, the surface of the central conductor 171 made of aluminum was selectively dissolved by applying an alternating current in an aqueous chloride solution to increase the surface area. The etching depth at this time was about 40 μm, and the surface area could be increased about 100 times by etching. Further, in order to protect the portion to which the anode terminal 121 is connected, a mask 176 was produced for each 2 mm of both ends in the length direction of the central conductor 171. The mask 176 was formed by dipping in a fluororesin (hexafluoropropylene) solution and drying. Because of this mask 176, the length L of the line portion in this embodiment is 16 mm obtained by subtracting the length of the mask from the length of the center conductor 171. Thereafter, the surface of the central conductor 171 was anodized at a voltage of 6.3V. By this anodic oxidation, a dielectric layer 173 made of aluminum oxide was formed on the surface of the central conductor 171. The dielectric layer 173 has a thickness of 10 nm, a dielectric constant ε of about 7.1 × 10 −11 F / m, and a magnetic permeability μ of about 1.26 × 10 −6 H / m.

  A resistance layer 174 made of conductive polymer layers 174a and 175b was formed so as to cover the dielectric layer 173. In this embodiment, the conductance values of the conductive polymer layers 174a and 174b are set to an appropriate conductance value Gc expressed by Equation 1. Therefore, first, Zo in this embodiment is obtained. In this embodiment, since the surface area is increased by etching, it is considered as a transmission line having a large area because the surface area is increased. In other words, if the length of each side of the line portion is increased by the square root of the surface area enlargement ratio, the line portion is 1.5 mm wide × 16 mm long, and therefore 15 mm wide × 160 mm long. Calculate assuming. Further, in the present embodiment, since the dielectric layer 173 is very thin, the characteristic impedance Zo is obtained on the assumption that the electromagnetic wave propagates in the transmission line in the TEM mode in which the electric field and the magnetic field are completely orthogonal. At this time, the characteristic impedance Zo is obtained by the following equation 17 from the capacitance C per unit length of the element, the dielectric constant ε and the magnetic permeability μ of the dielectric layer.

In the case of the present embodiment, the capacitance per unit length of the line portion was 21 μF, so that the capacitance C per unit length is about 130 μF / m when divided by the length of the expanded line portion. Accordingly, the characteristic impedance Zo when the square root of the enlargement ratio is widened is 72 μΩ. From this characteristic impedance Zo and the expanded line length, an appropriate conductance value Gc in the case where it is expanded by the square root of the expansion rate from Equation 1 is 2.7 × 10 ⁴ S / m to 2.7 × 10 ⁶ S /. between m. Since this value is a value obtained by expanding the square root of the enlargement ratio, it is 2.7 × 10 ³ S / m to 2.7 × 10 ⁵ S / m, which is 1 of the square root of the enlargement ratio.

The conductive polymer layers 174a and 174b have a two-layer structure in order to easily control the conductivity, and the formation is performed using the method described in Example 2 of Japanese Patent Application Laid-Open No. 64-82515. It was. That is, after the conductive polymer 174a was formed by chemical polymerization, the conductive polymer 174b was formed by electrolytic polymerization. At this time, the production conditions of the electrolytic polymerization such as the thickness were changed so that the conductance value Gc of the conductive polymer layers 174a and 174b is represented by the formula 1. In this embodiment, the surface of the central conductor 171 is roughened by etching, and it is difficult to obtain the conductance value from the structure. Therefore, a condition for obtaining a desired conductance value was adopted from the result of forming the conductive polymer under some conditions, and as a result, the conductivity of the conductive polymer was set to about 100 S / m. In addition, the conductive polymer was formed so as to fill the unevenness roughened by the etching of the central conductor 171 and to have a thickness of about 3 μm from the protrusion. At that time, the final resistance layer conductance value (measured after forming the following outer conductor) was 1.3 × 10 ⁴ S / m.

  In this embodiment, the conductive polymer layers 174a and 174b are layers that function as resistance layers. Specifically, the conductive polymer layers 174a and 174b can be formed of a polymer such as polypyrrole, polythiophene, or polyaniline. As the first conductive polymer layer 174a, a polypyrrole film was formed by chemical oxidation polymerization, and as the second conductive polymer layer 174b, a polypyrrole film was formed by electrolytic polymerization. The conductive polymer layers 174a and 174b can be combined with an electron-donating or electron-withdrawing dopant to increase the conductivity. In Example 1, however, dodecylbenzenesulfone sun ferric iron and did. In addition, usable dopants include compounds that act as Lewis acids such as halogen compounds such as iodine, chlorine and perchlorate anions, aromatic sulfonic acid compounds, and Lewis bases such as lithium and tetraethylammonium cations. What to do can also be mentioned.

  Next, a conductive carbon paste layer 174c is formed on the conductive polymer layers 174a and 174b. The conductive carbon paste layer 174c functions as an adhesive layer, and is formed to adhere the conductive polymer layer 174b and the outer conductor 172 made of silver paste. The conductive carbon paste was applied onto the conductive polymer layer 125 and cured so that the conductive carbon paste layer 174c had a thickness of about 20 μm. Further, an outer conductor 172 having a thickness of 60 μm made of silver paste was formed on the conductive carbon paste layer 174c.

  Regarding the power transmission characteristics of the transmission line thus formed, the power transmission characteristics in the state before connecting the terminals were measured with a network analyzer. FIG. 19 is a configuration diagram when measuring the power transmission characteristics of the transmission line. A coaxial connector was directly connected to the formed transmission line element, and the coaxial cable connected to the coaxial connector was connected to a network analyzer and measured as shown in FIG. The network analyzer is a measuring instrument that can measure how much power output from one port has propagated to the other port as one function. The reason for measuring the elements before connecting the terminals is to measure the characteristics of the transmission line that are not affected by the terminals by measuring in this state. FIG. 20 shows the measurement results. As can be seen from FIG. 20, the filter performance increases with increasing frequency.

  Next, the cathode terminal 122 made of a metal plate is bonded to the surface of the outer conductor 172 made of silver paste with the silver paste. The cathode terminal 122 functions as an external conductor together with the silver paste, and further functions as a terminal for connecting to a substrate or the like. The metal plate that is the cathode terminal 122 has an H shape in which a rectangle having a thickness of 100 μm, a width of 1.5 mm, and a length of 16 mm is added with a rectangle having a width of 1 mm and a length of 3 mm on both sides of the lengthwise direction. ing. Then, as shown in FIG. 19, the element is bonded to a rectangular portion (width line portion in FIG. 19) having a width of 1.5 mm × length of 16 mm. Moreover, the part added to the right and left of the both ends of a length direction becomes a cathode terminal for connecting with a printed circuit board.

  As shown in FIG. 18, anode terminals 121 made of a metal plate are connected to both ends of the central conductor 171 in the length direction. For this purpose, a mask of about 1.4 mm is removed by cutting from both ends of the central conductor 171 in the length direction. A part of the remaining 0.6 mm mask 176 is left to separate the anode terminal 121 and the cathode terminal 122. Then, the mask removal part of the center conductor 171 and the anode terminal 121 are connected by welding techniques, such as ultrasonic welding, laser welding, and resistance welding. The anode terminal 121 has a rectangular shape with a thickness of 100 μm × width 1.5 mm × length 5 mm.

  Packaging is performed by the mold 123 with the anode terminal 121 and the cathode terminal 122 partially exposed. Thereafter, the terminal portions of the anode terminal 121 and the cathode terminal 122 are bent. Thereby, the transmission line type noise filter concerning Example 1 is produced.

(Example 2)
A coaxial ceramic coaxial line type noise filter having the form shown in FIG. 22 was produced. FIG. 23 is a sectional view taken along the line CC ′, and FIG. 24 is a sectional view taken along the line DD ′. First, a dielectric (dielectric layer 223) made of a high dielectric constant ceramic having a cylindrical shape having an inner diameter r of 1.3 mm, an outer diameter R of 1.66 mm, and a length L of 5.4 mm was produced. This dielectric can be manufactured by the material and manufacturing method of a cylindrical ceramic capacitor generally used for high frequency applications. In this example, a ceramic having a relative dielectric constant εr of about 10,000 and a relative permeability μr of 1 was produced. . Anode conductors 221 were manufactured at both ends of the ceramic dielectric in the length direction with a length of 0.7 mm from the end. Therefore, the actual transmission line length L is 4.0 mm. Further, in order to separate the anode conductor 221 and the cathode conductor 222, a mask 225 having a width of 0.3 mm to 0.4 mm was formed on the outer periphery. Next, a resistance layer 224 was formed around the dielectric (dielectric layer 223). In the case of the dielectric layer 223 of the present embodiment, the characteristic impedance Zo is obtained from the inner diameter r and the outer diameter R by the following formula 18.

  Therefore, the characteristic impedance Zo is about 0.15Ω. Therefore, when applied to Equation 1, the conductance value Gc of the resistance layer 224 may be 5.4 × 10 2 S / m to 5.4 × 10 4 S / m. Therefore, a resistance paste (ruthenium oxide paste) is applied on the dielectric layer 223 to form the resistance layer 224. Although the thickness d of the resistance layer 224 varies depending on the resistance paste used, when the conductivity of the resistance paste is represented by σ, the thickness d is expressed by the following mathematical formula 19.

  When the electrical conductivity σ of the resistance paste is 100 S / m, the thickness d of the resistance layer 224 is calculated to be 4.9 μm to 660 μm. In this embodiment, the thickness d of the resistance layer 224 is 50 μm, and the conductance value Gc is 5.4 × 10 3 S / m. Next, an anode conductor 221 serving as a central conductor and a cathode conductor 222 serving as an external conductor were produced. These conductors were produced by using a method suitable for the production site and using vapor deposition, sputtering, plating, etc., so that the metal conductor (copper) layer had a thickness of 50 μm or more. Thus, a coaxial ceramic coaxial line type noise filter as shown in FIG. 22 can be obtained. Both ends 0.4 mm of the outer periphery of the element are anode terminals, and the width of the center 4 mm of the outer periphery is a cathode terminal.

(Example of use)
Next, a usage example of the transmission line type filter of the present invention will be described. The transmission line type noise filter is a two-terminal pair (four-terminal) element, and is mainly used as an element for power supply decoupling of a power supply line. FIGS. 25 to 28 are examples of the case where power supply decoupling is performed, FIG. 25 is a circuit diagram, FIG. 26 is a cross-sectional view of the printed circuit board of the present invention, and FIG. 27 is an upper surface of the printed circuit board of the present invention. FIG. 28 is a sectional view of the substrate before the transmission line type noise filter is applied. In this application, the printed circuit board carrying the transmission line type | mold filter of this invention mentioned above is provided. In the printed circuit board of the present invention, the transmission line type filter 251 according to the present invention is installed between the power supply wiring 255 and the LSI power supply wiring 254. As shown in FIG. 26, in this printed board, either the central conductor or the external conductor constituting the transmission line type filter 251 connects the power supply wiring 255 and the LSI power supply wiring 254, and the other one is connected to the ground. Used as a wiring board configured to be connected to the wiring 256. Reference numeral 257 indicates a substrate insulating layer.

  As shown in FIG. 28, the power supply wiring surrounded by A is separated from the substrate before applying the transmission line type noise filter, and the LSI 252 and the power supply 253 are electrically separated. Instead of the disconnected power supply wiring, a transmission line type noise filter 251 is installed as shown in FIG. As a result, the LSI 252 and the power source 253 are disconnected via the transmission line type noise filter 251. Since the LSI 252 and the power supply 253 are disconnected, noise superimposed on the power supply line from the LSI enters the transmission line type noise filter 251. The noise that enters the transmission line type noise filter 251 is reflected or absorbed by the transmission line type noise filter and does not propagate to the power supply circuit side. As a result, noise does not propagate to other LSIs connected to the same power supply circuit. Also, the problem of unnecessary electromagnetic waves caused by radiation from the power supply wiring can be solved.

  The present invention is effective as a transmission line type filter as a power supply decoupling element effective in suppressing electromagnetic interference between circuits.

Claims (16)

A transmission line type filter having a dielectric layer and a resistance layer between electrically opposing conductors and having a circular or rectangular cross-sectional shape, wherein the resistance layer at the resonance frequency of the transmission line type filter is a conductor A transmission line type filter characterized in that the conductance value Gc per unit length of the resistance layer satisfies the relationship of the following equation, where Zo is the characteristic impedance and L is the length of the transmission line.

  2. The transmission line type filter according to claim 1, further comprising one dielectric layer and one resistance layer between the conductors.   2. The transmission line type filter according to claim 1, further comprising two dielectric layers and one resistance layer between the conductors, wherein the resistance layer is located between the two dielectric layers.   2. The transmission line type filter according to claim 1, further comprising a dielectric layer and two resistance layers between the conductors, wherein the dielectric layer is located between the two resistance layers.   The transmission line according to any one of claims 1 to 4, wherein the electrically opposing conductors are a center conductor and an outer conductor disposed so as to surround the outside of the center conductor. Type filter.   The electrically opposing conductor is a signal conductor located at the center and a ground conductor disposed so as to be sandwiched from above and below the signal conductor, and the resistance layer is arranged on the signal conductor. The transmission line type filter according to claim 1, wherein the transmission line type filter is formed so as to surround.   The transmission line type filter according to claim 1, wherein the electrically opposed conductors are a flat lower conductor and an upper conductor arranged to face the lower conductor.   The transmission line type filter according to any one of claims 1 to 7, wherein a conductivity of the resistance layer is 1/100 or less of a conductivity of the conductor.   The resistance layer is formed of a carbon material, a conductive polymer material, a solid electrolyte, a liquid electrolyte, a low-resistance alloy, a semiconductor material, or the like. Transmission line type filter.   The transmission line type filter according to any one of claims 1 to 9, wherein the resistance layer is a laminated type resistance layer including two or more layers.   2. The method of manufacturing a transmission line type filter according to claim 1, further comprising a dielectric layer and a resistance layer between electrically opposing conductors, the step of forming a dielectric layer on a central conductor, and the dielectric A step of forming a resistance layer composed of two or more layers so as to cover the layer, and a step of forming an external conductor on the resistance layer, wherein the resistance layer composed of the two or more layers differs in polymerization A method for manufacturing a transmission line type filter, which is a laminate of conductive polymer layers formed by the method.   The step of forming a resistance layer composed of two or more layers includes a first step of forming a conductive polymer layer by chemical oxidative polymerization, and a step of forming a conductive polymer layer by electrolytic polymerization after the first step. The method of manufacturing a transmission line type filter according to claim 11, comprising two steps.   2. The method of manufacturing a transmission line type filter according to claim 1, wherein a dielectric layer and a resistance layer are provided between electrically opposing conductors and the cross-sectional shape is circular, wherein the inner surface and the outer surface of the cylindrical dielectric are formed. A transmission line type filter comprising: a step of plating a resistance material on a surface to form two resistance layers; and a step of plating a conductive material on the two resistance layers to form a conductor. Manufacturing method.   2. The method of manufacturing a transmission line type filter according to claim 1, further comprising a dielectric layer and a resistance layer between electrically opposing conductors, wherein an oxide film as a dielectric layer is formed on an inner surface of an outer conductor made of a valve metal. Forming an oxide film as a dielectric layer on the outer surface of the central conductor made of valve metal, and injecting an electrolyte as a resistance layer between the outer conductor and the inner conductor on which the oxide film is formed And a process for manufacturing a transmission line type filter.   It is a printed circuit board carrying the transmission line type filter according to any one of claims 1 to 10, wherein the transmission line type filter is installed between a power supply wiring and an LSI power supply wiring. Printed circuit board.   16. The center conductor or the outer conductor constituting the transmission line type filter connects a power supply wiring and an LSI power supply wiring, and the other one is connected to a ground wiring. Printed circuit board as described in 1.

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