JP5371792B2 - Lightning protection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting arrester that eliminates the need for separate installation of a filter and a lighting arrester, and is hardly affected by an external environment. <P>SOLUTION: The lighting arrester is connected to a feeder 1B connected to an aerial, wherein an undesired high-frequency signal at a frequency of fr (fp&gt;fr) to a high-frequency signal of a frequency fp flows. The lighting arrester includes: a basic stub 11, where one end is short-circuited for grounding and the other end is connected to the feeder 1B, and length is set based on a wavelength &lambda;p of a high-frequency signal of the frequency fp to make an impedance at a connection point A infinite to the high-frequency signal of the frequency fp; and a correction stub 12, where length is set to make connection to the basic stub 11 by branching and to set the impedance at the connection point A to zero against an undesired high-frequency signal at the frequency fr. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a lightning arrester that protects transmission facilities and reception facilities from the effects of lightning strikes.

  Business departments that use radio in the VHF (Very High Frequency) band or UHF (Ultra High Frequency) band, for example, radios such as transmission and reception equipment for commercial radios used in the power distribution and sales departments of electric power companies In the facility, radio equipment such as a transmitter and a receiver are installed on a mountaintop with a good view. Thereby, a wide range of communication is possible.

  However, it is affected by lightning because the radio is installed at the top of the mountain. In other words, there is a possibility of lightning strike because the metal pillar is used for the antenna of the radio. In order to prevent the effects of lightning, a lightning rod is usually installed near the antenna. Thereby, it is possible to prevent lightning strikes on the antenna. However, when there is a lightning strike on the lightning rod, a strong current from the lightning flows, and an induced current flows through the antenna line and the power supply line connected to the antenna line. This induced current adversely affects the radio equipment to which the feeder line is connected. In order to reduce the influence of this induced current, various lightning arresters are provided on the feeder line (see Cited Documents 1 to 6). These lightning arresters have a configuration in which the other end of a coil whose one end is grounded is connected to the inner conductor of the coaxial cable while preventing the passage of a high-frequency signal. Since the induced current caused by lightning is close to direct current, the coil passes the induced current flowing through the inner conductor to the ground side.

  In addition to these methods, there are lightning arresters in which the inner conductor and the outer conductor of the coaxial cable are short-circuited at one end and grounded, and the other end is connected in parallel to the feeder line path in the vicinity of the antenna line (Cited Document 7). reference). That is, a lightning arrester is formed by a coaxial cable. In this method, when a high-frequency transmission line that is a coaxial cable is made ¼ of the wavelength of a high-frequency signal, and the internal conductor and the external conductor on one end side are electrically short-circuited, The characteristic that the impedance at the frequency of the high frequency signal becomes infinite and the direct current resistance is substantially zero as viewed from the end of the high frequency transmission path is utilized. Damage caused by lightning induced current is reduced by grounding the power supply line in a DC manner.

Japanese Patent Laid-Open No. 2001-230047 JP 2003-208962 A JP 2003-209003 A JP 2003-217907 A JP 2003-229229 A JP 2006-296163 A Japanese Utility Model Application No. 6-16827

  By the way, in a transmission facility, for example, a harmonic is generated with respect to a high-frequency signal to be transmitted. The intensity of this harmonic is regulated by the Radio Law. On the other hand, in a receiving facility, a high-frequency signal not intended for reception is received by an antenna, and it is desirable to eliminate this signal before this signal is input to the receiver. For this reason, in order to suppress harmonics and eliminate unintended high-frequency signals, that is, to remove high-frequency signals with unnecessary frequencies (hereinafter referred to as “unnecessary signals”) The filter is inserted in place.

  However, as described above, since a lightning arrester is installed on the antenna side of the radio equipment, providing a filter for removing unnecessary signals leads to an increase in equipment cost. A filter for removing unnecessary frequencies is generally composed of a lumped constant circuit such as a coil or a capacitor. However, since the radio equipment installed at the top of the mountain is affected by the temperature of the season, metal elements such as coils and capacitors expand and contract depending on the temperature. As a result, the electrical characteristics of the metal elements used in the lumped constant circuit change, and the characteristics of the filter also change. In other words, it is not appropriate to install a filter or the like in the vicinity of an aerial line that is installed outdoors that is easily affected by the external environment such as weather.

  An object of the present invention is to solve the above-described problems, and to provide a lightning arrester that eliminates the need for separately installing a filter and a lightning arrester and is less susceptible to the influence of the external environment.

  In order to solve the above problems, the invention of claim 1 is a power supply line connected to an aerial line, and is connected to a power supply line through which an unnecessary high-frequency signal having a low frequency flows with respect to a predetermined high-frequency signal. A lightning protection device having one end short-circuited and grounded, and the other end connected to the feeder line, and in order to make the impedance at the connection point infinite with respect to the predetermined high-frequency signal, A first distributed constant line whose length is set based on the wavelength of the high frequency signal, and a branching connection to the first distributed constant line and an impedance at the connection point for the unnecessary high frequency signal And a second distributed constant line having a length set in order to set the length to zero, the lightning arrester.

  In the first aspect of the present invention, the frequency of the unnecessary high-frequency signal is lower than the predetermined high-frequency signal, and the first distributed constant line whose length is set based on the wavelength of the predetermined high-frequency signal is used. Thus, a second distributed constant line whose length is adjusted is provided in order to zero the impedance at the connection point for unnecessary high-frequency signals.

  The invention according to claim 2 is a lightning protection device connected to a power supply line connected to an aerial line and connected to a power supply line through which an unnecessary high-frequency signal having a high frequency with respect to a predetermined high-frequency signal flows. A first distributed constant whose length is set based on the wavelength of the unnecessary high-frequency signal in order to make the impedance at the connection point zero with respect to the unnecessary high-frequency signal that is connected to the electric wire and flows through the feeder line In order to make the impedance at the connection point infinite with respect to the predetermined high-frequency signal, the line is short-circuited at one end and grounded and branched to the first distributed constant line and connected at the other end A lightning arrester comprising: a second distributed constant line having a set length.

  In the invention according to claim 2, for the case where the frequency of the unnecessary high-frequency signal is higher than the predetermined high-frequency signal, the first distributed constant line whose length is set based on the wavelength of the unnecessary high-frequency signal is used. In order to make the impedance at the connection point infinite for a predetermined high-frequency signal, a second distributed constant line having a set length is provided.

  The invention of claim 3 is a lightning arrester characterized in that the plurality of lightning arresters according to claim 1 or claim 2 are connected in series with a predetermined interval with respect to the power supply line.

  According to the first aspect of the present invention, a direct current caused by a lightning strike or the like is short-circuited by the first distributed constant line whose one end is short-circuited, and the impedance is infinite for a predetermined high-frequency signal. The impedance becomes zero for an unnecessary high frequency signal. Thereby, the function of a lightning arrester and the function of the filter which attenuates an unnecessary high frequency signal can be provided. Further, according to the present invention, since the device is configured using the distributed constant line, it can be made less susceptible to the influence of the external environment as compared with the conventional filter using the metal element. Further, according to the present invention, it is possible to attenuate a signal having an arbitrary frequency by adjusting the length of the second distributed constant line. Furthermore, according to the present invention, since the first distributed constant line is formed based on a short wavelength of a predetermined high-frequency signal, the apparatus can be reduced in size.

  According to the second aspect of the present invention, a direct current is short-circuited by the second distributed constant line whose tip is short-circuited, and the impedance is infinite for a predetermined high-frequency signal. In addition, the impedance becomes zero for an unnecessary high-frequency signal. Thereby, the function of a lightning arrester and the function of the filter which attenuates an unnecessary high frequency signal can be provided. Further, according to the present invention, similarly to the first aspect of the invention, it is possible to make it less susceptible to the influence of the external environment, and it is possible to attenuate a signal having an arbitrary frequency. Furthermore, according to the present invention, since the first distributed constant line is formed based on the short wavelength of the unnecessary high-frequency signal, the apparatus can be miniaturized.

  According to the invention of claim 3, the amount of attenuation can be increased by cascading a plurality of lightning arresters. Further, if the lightning arrester is configured to attenuate high frequency signals having different frequencies, high frequency signals having a plurality of frequencies can be attenuated.

It is a block diagram which shows the lightning arrester by Embodiment 1, and the transmission equipment to which this lightning arrester is applied. 1 is a configuration diagram illustrating a lightning arrester according to Embodiment 1. FIG. It is explanatory drawing for demonstrating the lightning arrester by Embodiment 1. FIG. It is a figure explaining the basic method of calculating | requiring the length of a stub using a Smith chart, Fig.4 (a) is explanatory drawing for calculating | requiring the reactance from a short circuit point to a midway branch part, FIG.4 (b) is FIG. It is explanatory drawing for calculating | requiring the length of a stub. It is a figure explaining the method of calculating | requiring the length of a stub using a Smith chart, Fig.5 (a) is explanatory drawing for calculating | requiring the reactance from a short circuit point to a midway branch part, FIG.5 (b) is a feed line FIG. 5C is an explanatory diagram for obtaining the stub length. FIG. It is a figure which shows the frequency characteristic of a lightning arrester. It is explanatory drawing explaining the lightning arrester by Embodiment 2. FIG. It is a figure explaining the basic method of calculating | requiring the length of a stub using a Smith chart, Fig.8 (a) is explanatory drawing for calculating | requiring the reactance from a short circuit point to a midway branch part, FIG.8 (b) is FIG. It is explanatory drawing for calculating | requiring the length of a stub. It is a figure explaining the method of calculating | requiring the length of a stub using a Smith chart, Fig.9 (a) is explanatory drawing for calculating | requiring the reactance from a short circuit point to a midway branch part, FIG.9 (b) is a feed line FIG. 9C is an explanatory diagram for obtaining the reactance up to the connecting portion, and FIG. 9C is an explanatory diagram for obtaining the length of the stub. FIG. 10 is a configuration diagram showing a transmission facility based on the third embodiment. FIG. 10 is a diagram illustrating a transmission path for explaining the fourth embodiment. It is a figure for demonstrating a basic stub and a correction | amendment stub. It is a figure for demonstrating the basic stub and correction | amendment stub of the specific example 1. FIG. It is a figure for demonstrating the basic stub and correction | amendment stub of the specific example 2. FIG. It is a figure for demonstrating the basic stub and correction | amendment stub of the specific example 3. FIG. It is a figure for demonstrating the other example of the basic stub and correction | amendment stub of the specific example 3. FIG. It is a figure for demonstrating the basic stub and correction | amendment stub of the specific example 4. FIG.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. In each embodiment, the case where this invention is applied with respect to transmission equipment is taken as an example.

(Embodiment 1)
FIG. 1 shows a lightning arrester according to this embodiment and a transmission facility to which the lightning arrester is applied. The transmission facility in FIG. 1 includes transmitters 1A and 2A. Transmitters 1A and 2A are connected to antennas 1C and 2C by feeder lines 1B and 2B, respectively. Feed lines 1B and 2B are coaxial cables (distributed constant lines) for flowing high-frequency signals from transmitters 1A and 2A. The antennas 1C and 2C are installed away from the installation column 3. The aerial lines 1C and 2C emit high-frequency signals flowing through the feeder lines 1B and 2B into the air by radio waves. Further, a lightning rod 4 is installed on the installation column 3 in order to protect the aerial lines 1C and 2C from lightning, and the lightning rod 4 is grounded by a ground wire 5. Thereby, when there is a lightning strike on the lightning rod 4, a strong current due to the lightning flows to the ground via the ground wire 5.

The transmitter 1A is used for, for example, commercial radio, and the frequency of the high-frequency signal of the transmitter 1A is fp (wavelength λp). The transmitter 2A is used for, for example, industrial radio, and the frequency of the high-frequency signal of the transmitter 2A is fr (wavelength λr). And in this embodiment,
fp> fr
It is.

  The lightning arresters 10 and 20 according to this embodiment are connected to the power supply lines 1B and 2B of such a transmission facility, respectively. Since the lightning arrester 20 is the same as the lightning arrester 10, the lightning arrester 10 will be described below, and the description of the lightning arrester 20 will be omitted.

  As shown in FIG. 2, the lightning arrester 10 is connected in parallel to the feeder line 1B. The lightning arrester 10 includes a basic stub 11 and a correction stub 12, adapters 13 and 14, a plug 15, and a ground terminal 16. The adapter 13 is a T-shaped branching part. Jacks are provided at three ends of the adapter 13, and plugs 15 can be attached to the respective jacks. The basic stub 11 and the correction stub 12 are connected by the adapters 13 and 14 and the plug 15.

  The basic stub 11 is a coaxial cable having a predetermined length. One end of the basic stub 11 is connected to the power supply line 1B by the adapter 13 and the plug 15 at a connection point A (shown by a broken line circle) in the middle of the power supply line 1B. That is, the inner conductor of the basic stub 11 is connected to the inner conductor of the feeder line 1B, and the outer conductor of the basic stub 11 is connected to the outer conductor of the feeder line 1B. Thereby, the basic stub 11 is connected in parallel at the connection point A to the feeder line 1B. The other end of the basic stub 11 is grounded by a ground terminal 16 by short-circuiting the inner conductor and the outer conductor.

  The basic stub 11 has the following action. As shown in FIG. 3, the basic stub 11 having a length L1 is a 3/4 wavelength transmission line having a frequency fp. In FIG. 3, the power supply line 1 </ b> B, the basic stub 11, and the correction stub 12 are shown by two parallel lines for simplification of illustration. When the 3/4 wavelength basic stub 11 having the frequency fp is connected to the feeder line 1B, the impedance of the basic stub 11 viewed from the connection point A of the feeder line 1B becomes infinite with respect to the high-frequency signal having the frequency fp. A high-frequency signal having a frequency fp from the transmitter 1A is prevented from flowing to the basic stub 11. That is, the frequency fp is a passing frequency that allows only the feeder line 1B to pass. On the other hand, since the induced current flowing through the feeder line 1B is a direct current, the basic stub 11 whose other end is grounded flows the induced current to the ground, preventing the induced current from flowing to the transmitter 1A. That is, when there is a lightning strike on the lightning rod 4 and a strong current flows through the grounding wire 5, the basic stub 11 flows the induced current generated in the feeder 1B to the ground, and this induced current passes through the feeder 1B. And the transmitter 1A is protected.

によって得られる。なお、値ｖ_ｐは使用する伝送路の速度係数であり、伝送路中の伝播速度と光速との比である。一方、長さＬ１２の基本スタブ１１は周波数ｆｐの１／２波長であるので、長さＬ１２は、

によって得られる。このように算出した長さＬ１１とＬ１２との和により基本スタブ１１の長さＬ１を算出する。 The length L1 of the basic stub 11 is obtained as follows. The length from the connection point A to the branch point B is L11, and the length from the other short-circuited end to the branch point B is L12. Since the basic stub 11 having the length L11 is a quarter wavelength of the frequency fp, the length L11 is

Obtained by. The value v _p is the speed coefficient of the transmission line used, and is the ratio between the propagation speed in the transmission line and the speed of light. On the other hand, since the basic stub 11 having the length L12 is ½ wavelength of the frequency fp, the length L12 is

Obtained by. The length L1 of the basic stub 11 is calculated from the sum of the calculated lengths L11 and L12.

  The correction stub 12 is a coaxial cable connected to the basic stub 11. One end of the correction stub 12 is connected to the basic stub 11 at a branch point B (shown by a broken line circle) by an adapter 14 and a plug 15. At this time, one end of the correction stub 12 is at a position of a length L11 away from the connection point A by ¼ of the wavelength λp and at a position of a length L12 from the short-circuit point of the basic stub 11. At the branch point B, the inner conductor of the correction stub 12 is connected to the inner conductor of the basic stub 11, the outer conductor of the correction stub 12 is connected to the outer conductor of the basic stub 11, and the correction stub 12 is branched from the basic stub 11. Yes. The other end of the correction stub 12 is open.

  The correction stub 12 has the following action. As described above, the installation pillar 3 is provided with the aerial lines 1C and 2C. Therefore, when the antenna 1C receives the radio wave from the antenna 2C, the high-frequency signal having the frequency fr flowing through the feeder line 1B becomes an unnecessary signal for the transmitter 1A. Therefore, unnecessary signals are removed using the impedance of the correction stub 12 to prevent a high-frequency signal having the frequency fr from passing through the feeder line 1B. Therefore, if the impedance is made zero with respect to the frequency fr at the connection point A shown in FIG. 3, the high-frequency signal of the frequency fr is short-circuited in the feeder line 1B, and the transmission of this signal is prevented. Can do. Therefore, the correction stub 12 having a length L2 is used so that the impedance when the basic stub 11 side is viewed from the connection point A at the frequency fr that is the blocking frequency is zero.

により得られる。同様に、基本スタブ１１の短絡点から分岐点Ｂまでの周波数ｆｒにおける正規化された波長ＮＷ１２は、

により得られる。 For this purpose, the length of the correction stub 12 is set as follows. The normalized wavelength NW11 at the frequency fr from the connection point A to the branch point B of the basic stub 11 is

Is obtained. Similarly, the normalized wavelength NW12 at the frequency fr from the short-circuit point of the basic stub 11 to the branch point B is

Is obtained.

により得られる。この合成正規化リアクタンスＣＸ１の逆符号の正規化リアクタンスである、

を、補正スタブ１２により分岐点Ｂに提供すれば、接続点Ａにおける整合がとれることになる。このために、図４（ｂ）に示すように、スミスチャートを用いて、正規化リアクタンスＸ２を与える正規化波長ＮＷ２を読み取る。そして、補正スタブ１２の長さＬ２を、

により算出する。 Thereafter, as shown in FIG. 4A, normalized reactances X11 and X12 of the normalized wavelengths NW11 and NW12 at the branch point B are obtained using the Smith chart. Since the normalized reactance X11 and the normalized reactance X12 are connected in parallel at the branch point B, these combined normalized reactances CX1 are

Is obtained. This is the normalized reactance of the opposite sign of this synthesized normalized reactance CX1.

Is provided to the branch point B by the correction stub 12, matching at the connection point A can be achieved. For this purpose, as shown in FIG. 4B, the normalized wavelength NW2 that gives the normalized reactance X2 is read using a Smith chart. Then, the length L2 of the correction stub 12 is

Calculated by

Specifically, the frequency fp of the high frequency signal of the transmitter 1A is 370 MHz, and the frequency fr of the high frequency signal of the transmitter 2A is 150 MHz. First, the normalized reactance for 150 MHz from the short-circuit point of the basic stub 11 to the midway branch (branch point B) is obtained. The wavelength from the short-circuit point at the other end of the basic stub 11 to the midway branch (branch point B) is λp / 2. In order to obtain the normalized reactance, as shown in FIG. 5A, the zero point of the line 101A representing the wavelength to the signal source is used as a base point.
0.5λ × (150/370) = 0.2027λ
The point calculated in (1) is connected to the center of the chart by a straight line 102. Thereafter, a normalized reactance value j3.3 at a point where the circle 103 representing the impedance when the resistance component is zero and the straight line 102 intersect is obtained. The value λ is the wavelength of the higher frequency of the pass frequency fp and the stop frequency fr, and is the wavelength λp in this embodiment.

Next, in the connection part (connection point A) between the feeder 1B and the basic stub 11, for a high-frequency signal of 150 MHz, the impedance is zero and the intermediate branch part (branch) from the connection part (connection point A) Find the normalized reactance up to point B). The wavelength from the connection part (connection point A) of the basic stub 11 to the midway branch part (branch point B) is λp / 4. In order to obtain the normalized reactance, as shown in FIG. 5B, the zero point of the line 101A representing the wavelength to the signal source is used as a base point.
0.25λ × (150/370) = 0.014λ
A point 104 is connected to the center of the chart by a straight line 104. Thereafter, a normalized reactance value j0.74 at a point where the circle 103 representing the impedance when the resistance component is zero and the straight line 104 intersect is obtained.

Next, since the normalized reactance j3.3 previously calculated for 150 MHz and the normalized reactance j0.74 are connected in parallel, the value of the combined normalized reactance at this time is
3.3 × 0.74 / (3.3 + 0.74) = 0.604
J0.604 from the value calculated by

The normalized reactance having the opposite sign to the calculated combined normalized reactance is −j0.6040 as shown in FIG. Then, the circuit length of the correction stub 12 having the open end that gives the normalized reactance −j0.6040 of the opposite sign is represented by a line 101B representing the normalized wavelength toward the load side.
0.25-0.87 = 0.163
From this value, it is 0.163λ.

  Thereafter, the length of the correction stub 12 is calculated using the normalized wavelength 0.163λ.

  When the corrected stub 12 having the calculated length is connected to the basic stub 11 at the branch point B, the length L11 generated by the basic stub 11 and the combined reactance generated by the length L12 generated by the basic stub 11 are reversed. Since the correction stub 12 gives the reactance of the sign, the impedance on the basic stub 11 side at the connection point A becomes zero for a high-frequency signal having a frequency fr of 150 MHz.

  Next, the operation of this embodiment will be described. For commercial radio, radio waves are output from the antenna 1C by a high-frequency signal having a frequency of fp from the transmitter 1A. At this time, since the impedance when the basic stub 11 side is viewed from the connection point A of the lightning arrester 10 to the high frequency signal of the frequency fp is infinite, the lightning arrester 10 may affect the high frequency signal of the frequency fp. Absent.

  On the other hand, for the construction radio, radio waves are output from the antenna 2C by a high-frequency signal having a frequency fr from the transmitter 2A. At this time, the antenna 1C receives the radio wave from the antenna 2C, and sends a high-frequency signal having a frequency fr, that is, an unnecessary signal, to the feeder 1B. Since the correction stub 12 is connected to the basic stub 11 at the branch point B at the connection point A of the lightning arrester 10, the impedance on the basic stub 11 side is zero. Thereby, the lightning arrester 10 sends an unnecessary signal having a frequency fr to the basic stub 11 side, and prevents this signal from flowing into the transmitter 1A.

  In addition, when a lightning strike occurs on the lightning rod 4, a strong current flows to the ground through the grounding wire 5. At this time, an induced current also flows through the feeder line 1B. Since the induced current flowing through the feeder line 1B is a direct current, the basic stub 11 having the other end grounded in the lightning arrester 10 causes the induced current to flow to the ground, and the lightning arrester 10 transmits the induced current to the transmitter 1A. Prevents the flow.

  As described above, according to this embodiment, a short circuit is caused with respect to a DC induced current caused by a lightning strike, an impedance is infinite with respect to a high-frequency signal with a frequency fp, and the frequency fr. Since the impedance is zero for the unnecessary signal, it is possible to have both the function of a lightning arrester and the function of a filter for attenuating a high-frequency unnecessary signal. Moreover, according to this embodiment, since the lightning arresters 10 and 20 are mainly composed of the basic stub 11 and the correction stub 12 which are distributed constant lines, the influence of the external environment compared to a conventional filter using metal elements. It can be made difficult to receive. Moreover, according to this embodiment, it is possible to attenuate an unnecessary signal having an arbitrary frequency by adjusting the length of the correction stub 12 of the lightning arresters 10 and 20. Further, according to this embodiment, when the frequency of the high frequency signal of the transmitter 1A is fp and the frequency of the high frequency signal of the transmitter 2A is fr> fr, the wavelength is λp <λr. Therefore, the lightning arresters 10 and 20 can be configured with the shortest transmission path length, and the apparatus can be downsized.

The high frequency signal is
fp = 160MHz
fr = 60 MHz
FIG. 6 shows the frequency characteristics of the lightning arrester 10 in the case of. As shown in FIG. 6, the attenuation at 60 MHz is approximately 30 db, and the attenuation at 160 MHz is approximately zero. This measured data also indicates that the lightning arresters 10 and 20 according to this embodiment have a function as a filter.

  In this embodiment, the basic stub 11 is short-circuited, but both the basic stub 11 and the correction stub 12 are short-circuited by the method of calculating the length of the basic stub 11 and the correction stub 12 according to this embodiment. A lightning arrester 10 can be used, or a lightning arrester 10 in which the basic stub 11 is open and the correction stub 12 is short-circuited.

(Embodiment 2)
In the first embodiment, as shown in FIG. 7, the frequency of the high-frequency signal of the transmitter 1A is fp, and the frequency of the high-frequency signal of the transmitter 2A is fr.
fp> fr
In this embodiment,
fp <fr
The case where there is a relationship will be described. In this embodiment, components that are the same as or the same as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted. In this embodiment, a basic stub 21 and a correction stub 22 are provided instead of the basic stub 11 and the correction stub 12 of the first embodiment.

  The basic stub 21 is a coaxial cable similar to the basic stub 11 and has a length L5. The basic stub 21 is a 3/4 wavelength transmission line with a frequency fp, and one end of the basic stub 21 is connected to the feeder line 1B at a connection point E, and the other end is opened. The basic stub 21 has the following action. With the basic stub 21 having the other end opened, the impedance of the basic stub 21 viewed from the connection point E of the feeder line 1B becomes zero with respect to a high-frequency signal having the frequency fr. That is, the lightning arrester 10 sends the high-frequency signal of the frequency fr that is received by the aerial line 1C and flows through the power supply line 1B to the basic stub 21, and the high-frequency signal passes through the power supply line 1B. The flow to the transmitter 1A is prevented.

によって得られる。一方、長さＬ５２の基本スタブ２１は周波数ｆｒの１／４波長であるので、長さＬ５２は、

によって得られる。このように算出した長さＬ５１とＬ５２との和により基本スタブ２１の長さＬ５を算出する。 The length L5 of the basic stub 21 is obtained as follows. The length from the connection point E to the branch point F is L51, and the length from the other open end to the branch point F is L52. Since the basic stub 21 having the length L51 is ½ wavelength of the frequency fr, the length L51 is

Obtained by. On the other hand, since the basic stub 21 with the length L52 is a quarter wavelength of the frequency fr, the length L52 is

Obtained by. The length L5 of the basic stub 21 is calculated from the sum of the calculated lengths L51 and L52.

  The correction stub 22 is a coaxial cable similar to the correction stub 12 of the first embodiment. One end of the correction stub 22 is connected to the basic stub 21 at a branch point F. At this time, one end of the correction stub 22 is at a position of a length L51 that is separated from the connection point E by 1/2 of the wavelength λr and at a position of a length L52 from the short-circuit point of the basic stub 21. The other end of the correction stub 22 is grounded in the same manner as the other end of the basic stub 11 of the first embodiment. As a result, the correction stub 22 causes an induced current caused by lightning to flow to the ground and prevents the induced current from flowing to the transmitter 1A.

  The correction stub 22 has the following action. As described above, the high-frequency signal having the frequency fr flowing through the feeder line 1B is an unnecessary signal for the transmitter 1A, but the high-frequency signal having the passing frequency fp is a necessary signal. Therefore, if the impedance of the correction stub 22 is used to make the impedance infinite with respect to the frequency fp at the connection point E shown in FIG. 7, the high-frequency signal of the frequency fp is not affected in the feeder line 1B. It will be. Therefore, the correction stub 22 having a length L6 is used so that the impedance when the basic stub 21 side is viewed from the connection point E at the frequency fp is infinite.

により得られる。同様に、スタブ５１の開放端から分岐点Ｆまでの周波数ｆｐにおける正規化された波長ＮＷ５２は、

により得られる。 For this purpose, the length of the correction stub 22 is set as follows. The normalized wavelength NW51 at the frequency fp from the connection point E to the branch point F of the basic stub 21 is

Is obtained. Similarly, the normalized wavelength NW52 at the frequency fp from the open end of the stub 51 to the branch point F is

Is obtained.

により得られる。この合成正規化リアクタンスＣＸ５の逆符号の正規化リアクタンスである、

を、補正スタブ２２により分岐点Ｆに提供すれば、接続点Ｅにおける整合がとれることになる。このために、図８（ｂ）に示すように、スミスチャートを用いて、正規化リアクタンスＸ６を与える正規化波長ＮＷ６を読み取る。そして、補正スタブ２２の長さＬ６を、

により算出する。 Thereafter, as shown in FIG. 8A, normalized reactances X51 and X52 of the normalized wavelengths NW51 and NW52 at the branch point F are obtained using the Smith chart. Since the normalized reactance X51 and the normalized reactance X52 are connected in parallel at the branch point F, these combined normalized reactances CX5 are

Is obtained. It is a normalized reactance of the opposite sign of this combined normalized reactance CX5.

Is provided to the branch point F by the correction stub 22, the matching at the connection point E can be obtained. For this purpose, as shown in FIG. 8B, the normalized wavelength NW6 that gives the normalized reactance X6 is read using a Smith chart. Then, the length L6 of the correction stub 22 is set to

Calculated by

Specifically, it is assumed that the frequency fp of the high-frequency signal of the transmitter 1A is 150 MHz, and the frequency fr of the high-frequency signal of the transmitter 2A is 370 MHz. First, the normalized reactance for 150 MHz from the open point of the basic stub 21 to the midway branch (branch point B) is obtained. The wavelength from the short-circuit point at the other end of the basic stub 21 to the midway branch (branch point F) is λr / 4. In order to obtain the reactance, as shown in FIG. 9A, the point of the value 2.5 of the line 101A representing the wavelength to the signal source is a base point.
0.25λ × (150/370) = 0.014λ
A point separated by the position calculated in (1) is connected to the center of the chart by a straight line 201. Thereafter, a normalized reactance value −j1.36 at a point where the circle 103 representing the impedance when the resistance component is zero and the straight line 201 intersect is obtained. The value λ is the wavelength λr.

Next, in the connection part (connection point E) between the feeder 1B and the basic stub 21, for a high-frequency signal of 150 MHz, the impedance is infinite from the connection part (connection point E) to the midway branching part ( The reactance up to the branch point F) is obtained. The wavelength from the connection part (connection point E) of the basic stub 21 to the midway branch part (branch point F) is λr / 2. As shown in FIG. 9B, the point of the value 2.5 of the line 101A representing the normalized wavelength to the signal source is a base point.
0.5λ × (150/370) = 0.2027λ
A point separated by the position calculated in (1) is connected to the center of the chart by a straight line 202. Thereafter, a normalized reactance value −j0.305 at a point where the circle 103 representing the impedance when the resistance component is zero and the straight line 202 intersect is obtained.

Next, since the normalized reactance −j1.36 calculated previously for 150 MHz and the normalized reactance −j0.305 are connected in parallel, the value of the combined normalized reactance at this time is
(−1.36) × (−0.305) / ((− 1.36) + (− 0.305))
= -0.249
From the value calculated in step -j, 0.249.

  The normalized reactance having the opposite sign to the calculated combined normalized reactance is j0.249, as shown in FIG. Then, the circuit length of the correction stub 22 with a short-circuited tip, which gives this normalized sign of the reactance j0.249, is 0.038λ by the line 101A representing the wavelength toward the power source.

  Thereafter, the length L6 of the correction stub 22 is calculated based on the normalized wavelength 0.038λ.

  When the corrected stub 22 having the calculated length is connected to the basic stub 21 at the branch point F, the same value as the combined normalized reactance generated by the length L51 by the basic stub 21 and the length L52 by the corrected stub 22 is obtained. Therefore, the corrected stub 22 gives the normalized reactance of the opposite sign, so that the impedance on the side of the basic stub 21 becomes infinite at the connection point E for the high-frequency signal of the frequency fp.

  According to this embodiment, the lightning arrester function and the filter function for attenuating unnecessary high-frequency signals can be provided together as in the first embodiment. Further, according to this embodiment, when the frequency of the high-frequency signal of the transmitter 1A is fp and the frequency of the high-frequency signal of the transmitter 2A is fr, the relationship is λp> λr. The lightning protection device 10 can be configured with the shortest transmission path length, and the device can be miniaturized.

(Embodiment 3)
A transmission facility based on this embodiment is shown in FIG. In this embodiment, components that are the same as or the same as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted. In the transmission facility of FIG. 10, a plurality of lightning arresters 10 and 20 according to the first or second embodiment are serially connected to the feeder lines 1B and 2B at a quarter wavelength interval of fr or an odd multiple thereof. Connect to. That is, in this embodiment, the lightning arrester is composed of a plurality of lightning arresters 10 and 20.

  Thus, the amount of attenuation can be increased by cascading a plurality of lightning arresters 10 and 20. Further, if the lightning arresters 10 and 20 are configured to attenuate high frequency signals having different frequencies, unnecessary high frequency signals having a plurality of frequencies can be attenuated according to this embodiment.

(Embodiment 4)
In the first to third embodiments described above, the Smith chart is used to determine the lengths L2 and L6 of the correction stubs 12 and 22, but in this embodiment, the length is calculated using a trigonometric function. L2 and L6 are obtained.

Ｚｓ：入力端におけるインピーダンス
Ｚ_０：伝送路の特性インピーダンス
Ｚ_Ｌ：負荷インピーダンス
Γｓ：入力端から伝送路を見た反射係数
γ：伝播定数（γ＝α＋ｊβ：αは減衰定数、βは位相定数）
ｄ：入力端から伝送路の終端までの線路長
以下では、伝送路が無損失である場合について説明する。伝送路が無損失である場合には伝播定数γにおいて減衰定数α＝０になることから、無損失伝送路のインピーダンスは次のとおりである。

この実施の形態では、先の実施の形態と同様に、使用するスタブは先端短絡と先端開放の２種類である。先端短絡の場合のインピーダンス（実際にはリアクタンス）は、
Ｚ_Ｌ＝０
であるので、先の数１６式にこの条件を代入すると、

になる。ここで、
β＝２π／λ
であるので、インピーダンスは、

になる。 In a typical transmission line, for example, the transmission line shown in FIG. 11, the impedance is as follows.

Zs: impedance at the input end Z ₀ : characteristic impedance of the transmission line Z _L : load impedance Γs: reflection coefficient when the transmission line is viewed from the input end
γ: propagation constant (γ = α + jβ: α is an attenuation constant, β is a phase constant)
d: Line length from the input end to the end of the transmission line A case where the transmission line is lossless will be described below. When the transmission line is lossless, since the attenuation constant α = 0 in the propagation constant γ, the impedance of the lossless transmission line is as follows.

In this embodiment, as in the previous embodiment, there are two types of stubs to be used: tip short circuit and tip opening. The impedance (actually reactance) in the case of a short-circuited tip is
Z _L = 0
Therefore, if this condition is substituted into the previous equation 16,

become. here,
β = 2π / λ
So the impedance is

become.

になる。 The impedance when the tip is open is
Z _L = ∞
Therefore, if this condition is substituted into the previous equation 16,

become.

  As described in each of the previous embodiments, there are two design reference frequencies: a frequency fp to pass through and a frequency fr to block passage. Of these, paying attention to the higher frequency (wavelength λ), as shown in FIG. 12, a basic stub corresponding to 3/4 wavelength is provided. One end of the basic stub is connected to the power supply line at the connection point, and the tip which is the other end is short-circuited or opened. A branch point is provided in the middle of the basic stub, and one end of the correction stub for correcting the reactance is connected in parallel to the basic stub at the branch point. The tip which is the other end of the correction stub is short-circuited or opened. The branch point is the position of the quarter wavelength or the position of the quarter wavelength, and the branch point is selected based on the relationship between the frequency fp and the frequency fr.

Next, a specific example based on the relationship between the frequency fp and the frequency fr will be described.
<Specific example 1>
In specific example 1, the pass frequency fp and the stop frequency fr are
Passing frequency fp> stopping frequency fr × 1.5
This is the case.

  In this specific example, as shown in FIG. 13, the basic stub has a length of 3/4 wavelength of the passing frequency fp, and the tip is short-circuited and grounded. A position at a quarter wavelength of the passing frequency fp from the connection point of the feeder line is a branch point. At this branch point, a correction stub having a length d is connected in parallel to the basic stub. The tip of the correction stub is opened.

インピーダンスＺ１とインピーダンスＺ２の並列合成インピーダンスは、

であり、この並列合成インピーダンスと逆符号のインピーダンスを補正スタブで作成し、分岐点に並列に接続すればよい。つまり、逆符号のインピーダンスは、

である。これより、

となり、補正スタブの長さｄを得ることができる。
＜具体例２＞
具体例２は、通過周波数ｆｐと阻止周波数ｆｒとが、
通過周波数ｆｐ＜阻止周波数ｆｒ×０．５
の関係にある場合である。 The branch point, the 1/4 portion of the wavelength of the line, i.e. base stub feeders side from the branch point, appears impedance Z ₁ of the line short-circuited end with respect to the stopping frequency fr. Similarly, for a half portion of the wavelength of the line, i.e. base stub of short-circuit point side from the branch point, appears impedance Z ₂ of the line short-circuited end with respect to the stopping frequency fr.

The parallel combined impedance of impedance Z1 and impedance Z2 is

It is only necessary to create an impedance having a sign opposite to that of the parallel composite impedance using a correction stub and connect it in parallel to the branch point. In other words, the impedance of the opposite sign is

It is. Than this,

Thus, the length d of the correction stub can be obtained.
<Specific example 2>
In specific example 2, the pass frequency fp and the stop frequency fr are
Passing frequency fp <stopping frequency fr × 0.5
This is the case.

  In this specific example, as shown in FIG. 14, the basic stub has a length of 3/4 wavelength of the stop frequency fr, and the tip is opened. A position at a half wavelength of the blocking frequency fr from the connection point of the feeder line is a branch point. At this branch point, a correction stub having a length d is connected in parallel to the basic stub. The tip of the correction stub is short-circuited and grounded.

インピーダンスＺ１とインピーダンスＺ２の並列合成インピーダンスは、先の数２１式に示すとおりであり、この並列合成インピーダンスと逆符号のインピーダンスを補正スタブで作成し、分岐点に並列に接続すればよい。つまり、逆符号のインピーダンスは、

であり、

である。これより、

となり、補正スタブの長さｄを得ることができる。
＜具体例３＞
具体例３は、通過周波数ｆｐと阻止周波数ｆｒとが、
通過周波数ｆｐ（＝ｆｒ×１．５）＞阻止周波数ｆｒ
の関係にある場合である。 The branch point, the 1/2 portion of the wavelength of the line, i.e. base stub feeders side from the branch point, appears impedance Z ₁ of the line of the open-end with respect to the pass frequency fp. Similarly, for the quarter segment of the wavelength of the line, i.e. the base stub opening point side from the branch point, it appears impedance Z ₂ of the line of the open-end with respect to the pass frequency fp.

The parallel combined impedance of the impedance Z1 and the impedance Z2 is as shown in the above equation (21). The parallel combined impedance and the impedance opposite in sign may be created by the correction stub and connected in parallel to the branch point. In other words, the impedance of the opposite sign is

And

It is. Than this,

Thus, the length d of the correction stub can be obtained.
<Specific example 3>
In specific example 3, the pass frequency fp and the stop frequency fr are
Passing frequency fp (= fr × 1.5)> stopping frequency fr
This is the case.

  In this specific example, as shown in FIG. 15, the basic stub has a length of 3/4 wavelength of the passing frequency fp, and the tip is short-circuited and grounded. A position at a quarter wavelength of the passing frequency fp from the connection point of the feeder line is a branch point. At this branch point, a correction stub having a length d is connected in parallel to the basic stub. The tip of the correction stub is short-circuited.

インピーダンスＺ１とインピーダンスＺ２の並列合成インピーダンスは、先の数２１式に示すとおりであり、この並列合成インピーダンスと逆符号のインピーダンスを補正スタブで作成し、分岐点に並列に接続すればよい。つまり、逆符号のインピーダンスは、

であり、

である。これより、

となり、補正スタブの長さｄを得ることができる。 The branch point, the 1/4 portion of the wavelength of the line, i.e. base stub feeders side from the branch point, appears impedance Z ₁ of the line short-circuited end with respect to the stopping frequency fr. Similarly, for a half portion of the wavelength of the line, i.e. the base stub opening point side from the branch point, it appears impedance Z ₂ of the line short-circuited end with respect to the stopping frequency fr.

The parallel combined impedance of the impedance Z1 and the impedance Z2 is as shown in the above equation (21). The parallel combined impedance and the impedance opposite in sign may be created by the correction stub and connected in parallel to the branch point. In other words, the impedance of the opposite sign is

And

It is. Than this,

Thus, the length d of the correction stub can be obtained.

In the third specific example, as shown in FIG. 16, the apparatus may be configured by shortening the stub length to be used with a basic stub having an open tip.
<Specific Example 4>
In the specific example 4, the pass frequency fp and the stop frequency fr are
Passing frequency fp (= fr × 0.5) <stopping frequency fr
This is the case.

  In this specific example, as shown in FIG. 17, the basic stub has a length of 3/4 wavelength of the stop frequency fr, and the tip is opened. A position at a half wavelength of the blocking frequency fr from the connection point of the feeder line is a branch point. At this branch point, a correction stub having a length d is connected in parallel to the basic stub. The tip of the correction stub is short-circuited and grounded.

インピーダンスＺ１とインピーダンスＺ２の並列合成インピーダンスは、先の数２１式に示すとおりであり、この並列合成インピーダンスと逆符号のインピーダンスを補正スタブで作成し、分岐点に並列に接続すればよい。なお、補正スタブの長さｄは、
ｄ＝ｄ_１＋（ｆｐのλ／４）
である。そして、逆符号のインピーダンスは、

であり、

である。そして、

である。これより、

となり、補正スタブの長さｄを得ることができる。 The branch point, the 1/2 portion of the wavelength of the line, i.e. base stub feeders side from the branch point, appears impedance Z ₁ of the line of the open-end with respect to the pass frequency fp. Similarly, for the quarter segment of the wavelength of the line, i.e. the base stub opening point side from the branch point, it appears impedance Z ₂ of the line of the open-end with respect to the pass frequency fp.

The parallel combined impedance of the impedance Z1 and the impedance Z2 is as shown in the above equation (21). The parallel combined impedance and the impedance opposite in sign may be created by the correction stub and connected in parallel to the branch point. The length d of the correction stub is
d = d ₁ + (λ of fp / 4)
It is. And the impedance of the opposite sign is

And

It is. And

It is. Than this,

Thus, the length d of the correction stub can be obtained.

  The present invention is not limited to wireless transmission facilities and reception facilities, and can be used for facilities and circuits that handle various high-frequency signals.

1A, 2A Transmitter 1B, 2B Feed line 1C, 2C Aerial line 10, 20 Lightning arrester 11, 21 Basic stub (first distributed constant line)
12, 22 Correction stub (second distributed constant line)

Claims (3)

A lightning protection device connected to a power supply line connected to an aerial line and connected to a power supply line through which an unnecessary high-frequency signal having a low frequency with respect to a predetermined high-frequency signal flows,
One end is short-circuited and grounded, and the other end is connected to the feeder line, and in order to make the impedance at the connection point infinite with respect to the predetermined high-frequency signal, based on the wavelength of the predetermined high-frequency signal A first distributed constant line having a set length;
A second distributed constant line that is branched and connected to the first distributed constant line and has a length set to zero the unnecessary high frequency signal at the connection point;
A lightning protection device comprising: A lightning protection device connected to a power supply line connected to an aerial line and connected to a power supply line through which an unnecessary high-frequency signal having a high frequency with respect to a predetermined high-frequency signal flows,
The length is set based on the wavelength of the unnecessary high-frequency signal in order to make the impedance at the connection point zero with respect to the unnecessary high-frequency signal flowing through the power supply line. Distributed constant lines,
In order to make the impedance at the connection point infinite with respect to the predetermined high-frequency signal, one end is short-circuited and grounded and branched to the first distributed constant line and the other end is connected. A second distributed constant line set with:
A lightning protection device comprising:   3. A lightning arrester comprising a plurality of lightning arresters according to claim 1 or 2 connected in series with a predetermined interval with respect to a power supply line.

Images