JP2013187839A - Microwave terminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave terminator that can achieve high power resistance, wide band, and miniaturization at the same time.SOLUTION: On the surface of a dielectric substrate 2 formed are: a rectangular membrane resistor 1 one side of which is short circuited to a ground conductor 6 of the rear face of the dielectric substrate 2 and about which the real part of normalization impedance is equal to or less than 1 Ω and the imaginary part is nearly 0 Ω at the center frequency of a transmission signal when the short circuited end side is viewed from the opposite side of the short circuited end; a transmission line 4 which is formed such that one end contacts with the whole width of the opposite side of the short circuited end of the membrane resistor 1 and normalization admittance is nearly 1 S at the center frequency of the transmission signal when the membrane resistor 1 side is viewed from the other end; and a tip open stub 5 which is connected to the other end of the transmission line 4, and about which both of the real part and the imaginary part of normalization impedance are nearly 1 Ω at the center frequency of the transmission signal when the membrane resistor 1 side is viewed from a connection point with the transmission line 4.

Description

  The present invention relates to a microwave terminator.

  In a microwave circuit, one end of an isolator, coupler, hybrid circuit, etc. is terminated with a microwave terminator. However, there is a case where a high power durability terminator capable of terminating a high power microwave signal is often required. is there. In many cases, the high power withstand terminator is required to be small and have a wide bandwidth. In many cases, a microwave terminator configured by a planar circuit uses a film resistor formed on a substrate as a termination resistor. In the case of such a configuration, means for increasing the power durability include increasing the film resistance, reducing the thickness of the substrate, and using a high thermal conductive substrate. However, the increase in film resistance and the reduction in thickness of the substrate increase the parasitic capacitance of the film resistance, so that there is a problem that the reflection characteristics deteriorate in the high frequency band.

  For example, as a technique that enables a small-sized and high-power non-reflective termination, a configuration in which an open-ended stub and a matching circuit are provided on a film resistor configured on a substrate is disclosed (for example, Patent Document 1).

  Further, for example, as a technique for realizing a broadband reflection characteristic, a configuration in which a film resistance formed on a substrate is formed in a tapered shape and connected to a line conductor is disclosed (for example, Patent Document 2).

  In addition, for example, a technique for realizing a broadband characteristic of a reflection characteristic by arbitrarily selecting a dielectric substrate thickness so that an input impedance of a film resistor has a predetermined resistance value and a reactance component is almost zero is disclosed ( For example, Patent Document 3).

Japanese Patent Laid-Open No. 7-7307 JP 2005-260454 A Japanese Patent Laid-Open No. 5-129805

  However, the technique disclosed in Patent Document 1 has a problem that it is difficult to simultaneously realize a wide band and a small size because the matching circuit needs to have a multistage configuration in order to widen the reflection characteristics. there were.

  In the technique disclosed in Patent Document 2, the connection portion between the film resistance and the conductor pattern is only a part of the film resistance, and the microwave power is locally consumed by a part of the film resistance. There was a problem that the effect of the conversion was small.

  Further, in the technique disclosed in Patent Document 3, it is necessary to increase the film resistance in order to obtain high power resistance, and thus it is necessary to increase the thickness of the substrate in order to widen the reflection characteristics. However, when the substrate thickness is increased, the thermal resistance of the substrate is increased and the power durability is lowered. Therefore, there is a problem that it is difficult to simultaneously realize a high power durability and a wide band.

  The present invention has been made in view of the above, and an object of the present invention is to provide a microwave terminator capable of simultaneously realizing high power durability, wide band, and downsizing.

  In order to solve the above-described problems and achieve the object, a microwave terminator according to the present invention is a microwave terminator formed on the surface of a dielectric substrate having a ground conductor on the back surface, and one side of the microwave terminator is A rectangular membrane resistance having a real part of normalized impedance at the center frequency of the transmission signal, which is short-circuited to the ground conductor and viewed from the opposite side of the short-circuited end to the short-circuited end, and an imaginary part of approximately 0Ω, and one end A transmission line that is formed in contact with the entire width of the opposite side of the short-circuit end of the film resistor and has a normalized admittance at the center frequency viewed from the other end of the film resistance side is approximately 1S, and the other end of the transmission line And a tip open stub in which the real part and the imaginary part of the normalized impedance at the center frequency viewed from the connection point with the transmission line are approximately 1Ω.

  According to the present invention, there is an effect that it is possible to obtain a microwave terminator capable of simultaneously realizing high power durability, wide band, and downsizing.

FIG. 1 is a diagram illustrating an example of a microwave terminator according to the first embodiment. FIG. 2 is a Smith chart illustrating an example of frequency characteristics of impedance and admittance when the membrane resistance side is expected from each part of the microwave terminator according to the first exemplary embodiment. FIG. 3 is a diagram illustrating an example of reflection characteristics of the microwave terminator according to the first embodiment. FIG. 4 is a diagram showing a conventional example of a microwave terminator. FIG. 5 is a diagram showing an example of reflection characteristics of the conventional microwave terminator shown in FIG. FIG. 6 is a diagram of an example of the microwave terminator according to the second embodiment. FIG. 7 is a diagram of an example of the microwave terminator according to the third embodiment.

  A microwave terminator according to an embodiment of the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an example of a microwave terminator according to the first embodiment. FIG. 1A is a plan view of the microwave terminator according to the first embodiment, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG.

  As shown in FIG. 1, the microwave terminator according to the first embodiment is formed on the surface of a dielectric substrate 2 having a ground conductor 6 on the back surface, and a through hole (via) 3 is formed on one side of the ground conductor 6. A transmission line 4 formed of a high-impedance line whose one end is in contact with the entire width of the opposite side of the short-circuited end of the film resistance 1, and the other end of the transmission line 4. And an open-ended stub 5 formed of a rectangular low impedance line. A microwave signal that is a transmission signal of a microwave transmission circuit to which the microwave terminator according to the first embodiment is applied is input from an input terminal 7 to which the transmission line 4 and the open-ended stub 5 are connected.

  The operation of the microwave terminator according to the first embodiment formed as described above will be described. The microwave signal input from the input terminal 7 is input to the film resistor 1 impedance-matched by the open-ended stub 5 and the transmission line 4 and is terminated by being converted into heat energy by the film resistor 1. The thermal energy generated by the film resistor 1 is radiated to the ground conductor 6 on the back surface mainly through the dielectric layer of the dielectric substrate 2. Assuming that the temperature of the ground conductor 6 is T1, the thermal resistance of the dielectric layer from the film resistance 1 of the dielectric substrate 2 to the ground conductor 6 is Rth, and the amount of heat generated by the film resistance 1 is Q, the temperature T2 of the film resistance 1 is Is represented by the following formula (1).

  T2 = T1 + Rth × Q (1)

  When the desired power is input to the microwave terminator according to the first embodiment, if the temperature T2 of the film resistor 1 is within the allowable temperature range of the film resistor 1 in the above equation (1), It can satisfy the withstand power.

  The thermal resistance Rth of the dielectric layer from the film resistance 1 to the ground conductor 6 of the dielectric substrate 2 is determined by the thermal conductivity, thickness, and heat generation area of the dielectric substrate 2. In order to increase the withstand power, heat is generated by using a high thermal conductivity material for the dielectric layer of the dielectric substrate 2, reducing the thickness of the dielectric layer of the dielectric substrate 2, and increasing the area of the film resistor 1. Increasing the area is effective. Further, the heat generated by the termination of the microwave signal has a property of being concentrated particularly on the connection portion between the membrane resistor 1 and the transmission line 4. For this reason, in this embodiment, the heat generation area is expanded by expanding the connection width between the film resistor 1 and the transmission line 4 to the width of one side of the film resistor 1. Thereby, the heat generated by the termination of the microwave signal can be efficiently radiated.

  Next, a broadband matching method of reflection characteristics of the microwave terminator according to the first embodiment will be described with reference to FIGS. FIG. 2 is a Smith chart illustrating an example of frequency characteristics of impedance and admittance when the membrane resistance side is expected from each part of the microwave terminator according to the first exemplary embodiment. FIG. 2A is a Smith chart (impedance chart) showing an example of the frequency characteristic of the impedance when the membrane resistance side is expected from a in FIG. 1A, and FIG. 2) is a Smith chart (admittance chart) showing an example of the frequency characteristics of the admittance when the film resistance side is expected from b in FIG. 2, and FIG. 2 (c) is the film resistance side expected from c in FIG. 1 (a). It is a Smith chart (impedance chart) which shows an example of the frequency characteristic of an impedance.

  First, a in FIG. 1A, that is, the real part of the normalized impedance at the center frequency fc of the microwave signal when the film resistor 1 side is viewed from the connection part between the film resistor 1 and the transmission line 4 is 1Ω or less, The area resistivity, width, and length of the film resistor 1 are selected so that the imaginary part is about 0Ω. At this time, the impedance of the side of the membrane resistor 1 viewed from a in FIG. 1A is substantially a DC resistance value at a low frequency as shown in FIG. 2A. It becomes a trajectory that turns around. The conditional expression at this time is expressed by the following expression (2) at the center frequency fc of the microwave signal, where Real (Z1) is the real part of the normalized impedance and Imag (Z1) is the imaginary part of the normalized impedance. be able to.

  Real (Z1) ≦ 1Ω, Imag (Z1) ≈0Ω (2)

  Next, transmission is performed so that the real part of the normalized admittance at b in FIG. 1A, that is, the center frequency fc of the microwave signal viewed through the transmission line 4 at the center frequency fc is about 1S. The width and length of the line 4 are selected. At this time, the impedance when the membrane resistor 1 side is viewed from b in FIG. 1A via the transmission line 4 has frequency characteristics as shown in FIG. The conditional expression at this time can be expressed by the following expression (3) at the center frequency fc of the microwave signal, where Real (Y2) is the real part of the normalized admittance.

  Real (Y2) ≈1S (3)

  Furthermore, c in FIG. 1 (a), that is, the real part of the normalized impedance at the center frequency fc of the microwave signal when the membrane resistor 1 side is viewed from the connection point between the transmission line 4 and the open-ended stub 5 is about 1Ω. The width and length of the open stub 5 are selected so that the imaginary part is about 0Ω. At this time, the impedance when the membrane resistor 1 side is viewed from c in FIG. 1A through the open end stub 5 and the transmission line 4 has frequency characteristics as shown in FIG. The conditional expression at this time is expressed by the following expression (4) at the center frequency fc of the microwave signal, where Real (Z3) is the real part of the normalized impedance and Imag (Z3) is the imaginary part of the normalized impedance. be able to.

  Real (Z3) ≈1Ω, Imag (Z3) ≈0Ω (4)

  Thus, by canceling out the frequency characteristics of the membrane resistor 1 with the transmission line 4 and the open-ended stub 5, broadband matching of the reflection characteristics of the microwave terminator according to the first embodiment becomes possible. FIG. 3 is a diagram illustrating an example of reflection characteristics of the microwave terminator according to the first embodiment. As shown in FIG. 3, the band in which the reflection characteristic of the microwave terminator according to the first embodiment is −25 dB or less is about 40% with respect to the center frequency of the microwave signal, and the reflection characteristic is good over a wide band. It can be seen that

  FIG. 4 is a diagram showing a conventional example of a microwave terminator. FIG. 4A is a plan view of a conventional microwave terminator, and FIG. 4B is a cross-sectional view taken along line A-A ′ in FIG.

  In the example shown in FIG. 4, an example is shown in which the area resistivity, width, and length of the membrane resistor 1 are selected so that the resistance value of the membrane resistor 1 is equal to the standardized impedance 1Ω. For this reason, in order to perform wideband matching, it is necessary to connect the matching circuit by the transmission line 4 and the open end stub 5 in multiple stages. In the example shown in FIG. 4, the matching circuit by the transmission line 4 and the open end stub 5 is used. Shows an example in which two stages are connected. For this reason, a circuit size becomes larger than the microwave terminator concerning this Embodiment.

  FIG. 5 is a diagram showing an example of reflection characteristics of the conventional microwave terminator shown in FIG. As shown in FIG. 5, the band in which the reflection characteristic of the conventional microwave terminator shown in FIG. 4 is −25 dB or less is about 20% with respect to the center frequency of the microwave signal. It can be seen that the band is narrower than the wave terminator.

  As described above, according to the microwave terminator of the first embodiment, a rectangular circuit in which one side is short-circuited to the ground conductor via a through hole (via) on the surface of the dielectric substrate having the ground conductor on the back surface. Forming a membrane resistance having a shape, a transmission line formed at one end in contact with the entire width of the opposite side of the short-circuited end of the film resistance, and an open-ended stub connected to the other end of the transmission line; The area resistivity, width, and length of the membrane resistor 1 so that the real part of the normalized impedance at the center frequency of the microwave signal viewed from the connection part of the wire is 1Ω or less and the imaginary part is about 0Ω. And the width and length of the transmission line 4 are selected so that the real part of the standardized admittance at the center frequency of the microwave signal as viewed through the transmission line through the transmission line is about 1S. Membrane resistance from the connection point between the stub and the open stub The width and length of the open-ended stub are selected so that the real part of the normalized impedance at the center frequency of the microwave signal viewed from the side is about 1Ω and the imaginary part is about 0Ω. The frequency characteristics are canceled by the transmission line and the open-ended stub, and the broadband matching of the reflection characteristics becomes possible.

  Further, since it can be realized by a single-stage matching circuit composed of a set of transmission lines and an open-ended stub, it can be made smaller than a configuration that requires a conventional multi-stage matching circuit.

  In addition, since the transmission line is in contact with the entire width of the opposite side of the short-circuited end of the membrane resistor, heat generated by the termination of the microwave signal can be efficiently radiated, and high power durability can be achieved.

  As described above, it is possible to simultaneously achieve high power durability, wide bandwidth, and downsizing, and it is possible to reduce the size and improve the performance of the microwave transmission circuit to which the microwave terminator according to the first embodiment is applied. Become.

  In the first embodiment described above, the configuration example in which the short-circuited end of the membrane resistor is connected to the ground conductor through a through hole or via has been described. However, the configuration in which the short-circuited end of the membrane resistor is connected to the ground conductor by substrate side metallization. It goes without saying that the same effects as those of the above-described configuration can be obtained.

  Further, it is possible to adopt a configuration in which the tip open stub is formed by a radial stub instead of the rectangular low impedance line, and it goes without saying that the same effect as the above-described configuration can be obtained.

Embodiment 2. FIG.
FIG. 6 is a diagram of an example of the microwave terminator according to the second embodiment. In addition, the same code | symbol is attached | subjected to the component which is the same as that of Embodiment 1, or equivalent, and the detailed description is abbreviate | omitted.

  In the microwave terminator according to the second embodiment shown in FIG. 6, unlike the microwave terminator according to the first embodiment, the short-circuited end of the film resistor 1 is approximately one quarter of the center frequency of the microwave signal. It consists of an open-ended stub with a wavelength length.

  With this configuration, even when it is impossible to electrically connect the film resistor 1 to the ground conductor 6 by through holes, vias, or substrate side metallization, it is possible to cope.

  The configuration of the microwave terminator according to the present embodiment is larger than the configuration described in the first embodiment. However, in the conventional configuration shown in FIG. The size can be reduced as compared with the case of a stub having an open end having a length of approximately a quarter wavelength of the center frequency.

  As described above, according to the microwave terminator of the second embodiment, the short-circuited end of the membrane resistor is configured with the open-ended stub having a length of about a quarter wavelength of the center frequency of the microwave signal. Therefore, even if it is impossible to electrically connect the film resistance to the ground conductor by through holes, vias, or substrate side surface metallization, the same effect as in the first embodiment can be obtained.

Embodiment 3 FIG.
FIG. 7 is a diagram of an example of the microwave terminator according to the third embodiment. In addition, the same code | symbol is attached | subjected to the component which is the same as that of Embodiment 1, or equivalent, and the detailed description is abbreviate | omitted.

  Unlike the microwave terminator according to the first embodiment, the microwave terminator according to the third embodiment illustrated in FIG. 7 is configured by a low impedance line or a radial stub in the configuration of the first embodiment illustrated in FIG. Instead of the open-ended stub 5, a capacitor including a parallel plate capacitor ground electrode 9, a parallel plate capacitor dielectric 11, and a parallel plate capacitor ground electrode 12 is provided.

  The parallel plate capacitor base electrode 12 is short-circuited to the ground conductor 6 through a through hole (via) 3.

  Further, the air bridge 10 is electrically connected between the input terminal 7 and the parallel plate capacitor dielectric 11 and between the parallel plate capacitor dielectric 11 and the transmission line 4.

  By configuring in this way, the matching circuit can be made smaller, although the structure is more complicated than the configuration including the tip open stub 5 described in the first embodiment.

  As described above, according to the microwave terminator of the third embodiment, a capacitor whose one end is short-circuited in place of the open-ended stub 5 configured by a low impedance line or a radial stub in the configuration of the first embodiment. Therefore, the matching circuit can be made more compact than the configuration provided with the open end stub 5 described in the first embodiment, and the microwave transmission to which the microwave terminator according to the third embodiment is applied. The circuit can be further miniaturized.

  In the third embodiment described above, the configuration example in which the short-circuited end of the membrane resistance is connected to the ground conductor through a through hole or via has been described. However, as described in the first embodiment, the short-circuited end of the membrane resistance is It may be configured to be connected to the ground conductor by substrate side surface metallization, and as described in the second embodiment, it is configured by a tip open stub having a length of about a quarter wavelength of the center frequency of the microwave signal. Needless to say, the same effects as those of the above-described configuration can be obtained.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

1 Film resistance 2 Dielectric substrate 3 Through hole (via)
4 Transmission line 5 Open end stub 6 Ground conductor 7 Input terminal 9 Parallel plate capacitor upper electrode 10 Air bridge 11 Parallel plate capacitor dielectric 12 Parallel plate capacitor ground electrode

Claims (7)

A microwave terminator formed on the surface of a dielectric substrate having a ground conductor on the back surface,
A rectangular membrane resistance in which one side is short-circuited to the ground conductor, the real part of the normalized impedance at the center frequency of the transmission signal viewed from the opposite side of the short-circuited end side is 1Ω or less, and the imaginary part is approximately 0Ω. ,
A transmission line having one end in contact with the entire width of the opposite side of the short-circuited end of the film resistor and a normalized admittance at the center frequency viewed from the other end of the film resistor side of approximately 1S;
An open-ended stub connected to the other end of the transmission line, the real part and the imaginary part of the normalized impedance at the center frequency viewed from the connection point with the transmission line at the center frequency are approximately 1Ω,
A microwave terminator comprising:   The microwave terminator according to claim 1, wherein the open end stub is formed by a low impedance line or a radial stub. A microwave terminator formed on the surface of a dielectric substrate having a ground conductor on the back surface,
A rectangular shape in which one side is short-circuited to the ground conductor, the real part of the normalized impedance at the center frequency of the transmission signal is 1Ω or less, and the imaginary part is about 0Ω when viewed from the opposite side of the short-circuited end to the ground conductor The membrane resistance of
A transmission line having one end formed in contact with the entire width of the opposite side of the short-circuited end of the film resistor, and a normalized admittance at the center frequency viewed from the other end of the film resistor side is approximately 1S;
One end is short-circuited to the ground conductor, the other end is connected to the other end of the transmission line, and the real part and imaginary part of the normalized impedance at the center frequency when the membrane resistance side is viewed from the connection point with the transmission line Both of which are approximately 1Ω,
A microwave terminator comprising:   The microwave transmission unit according to any one of claims 1 to 3, wherein the transmission line is formed of a high impedance line.   The microwave terminator according to any one of claims 1 to 4, wherein the short-circuit end of the film resistor is configured by a through hole or a via.   The microwave terminator according to any one of claims 1 to 4, wherein the short-circuit end of the film resistor is configured by substrate side metallization.   5. The microwave termination according to claim 1, wherein the short-circuited end of the film resistor is configured by an open-ended stub having a length of approximately a quarter wavelength of the center frequency. vessel.

Images