JPH0195616A - Two-way branching device - Google Patents

Abstract

PURPOSE:To make the voltage standing wave ratio nearly to '1' by using 1st and 2nd branching circuits so as to cancel each other the deviation of the input impedance from the characteristic impedance. CONSTITUTION:The 1st branching circuit BC1 is connected in parallel with a signal trunk line 4A and the 2nd branch circuit BC2 is connected in series. Since th input impedance of the 2-way directional branching device B lowered by the 1st branching circuit BC1 is increased by the 2nd branching circuit BC2, the input impedance is made nearly equal to the characteristic impedance. That is, since the deviation from the characteristic impedance is cancelled by the 1st branching circuit BC1 and the 2nd branching circuit BC2, the input impedance is made nearly equal to the characteristic impedance. Thus, the voltage standing wave ratio is made nearly to '1'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional branch, and in particular, to a bidirectional branching device that connects devices such as computers, OA equipment, terminals, and measuring instruments with signal trunk lines to form a network. This invention relates to a bidirectional branch used to connect a signal trunk line and each device during configuration.

[Conventional technology]

2. Description of the Related Art Within a single building or within a limited area, an information network is constructed by connecting devices such as computers, OA equipment, terminals, and measuring instruments with signal trunk lines. For example, as shown in FIG. 8, this network connects the computers 6 located in two different buildings with a signal trunk line 4B, and connects the signal trunk lines 4B to branchers B□, B2. It is configured by inserting a branch iB, ,B, ,B, &, - OA equipment, a terminal, a measuring device, etc. (hereinafter simply referred to as a terminal 7) by inserting a branch iB, ,B,,B,&,. In this network, the computer 6 outputs necessary signals to each terminal,
A signal is also input from the terminal 7 to the computer 7. Therefore, the branchers B1, B2, . For B, a bidirectional type is used that can pass signals from the signal trunk line 4B to the terminal device 7, and can also pass signals from the terminal device 7 to the signal trunk line 4B. The transmission speed of this signal trunk line 4B is 5M
This is done at high speeds such as bits per second or IOM0M bits per second. Each bidirectional branch BL, B2-B
s has a circuit configuration as shown in FIG. 9, for example. In FIG. 9, B is a bidirectional branch, 1 and 2 are main terminals to which a signal main line 4B is connected, 4A is an internal signal main line of bidirectional branch B, and 3 is a branch terminal. The branch circuit BC in the bidirectional branch B is composed of an autotransformer T whose one end is connected to the internal signal main line 4A and whose other end is grounded, and a resistance element R connected to its intermediate tap. ing. Since the impedance of the autotransformer T itself when viewed from the branch terminal 3 is almost "0", the resistance element R is connected to the branch terminal 3 with the impedance when looking at the branch circuit BC from the branch terminal 3. It is provided for matching with the impedance Z01 of the device.

In such a turnout B, when the signal main line 4B is connected to the main terminal 1.2 and the terminal equipment is connected to the branch terminal 3, for example, when the bidirectional turnout B is viewed from the main terminal 1. If the input impedance at that time is not equal to the characteristic impedance 7.2 of the signal main line 4B connected to the main line terminal 1, reflection will occur at the main line terminal 1.

Then, the reflection becomes noise to other devices connected to the signal main line 4B. The same can be said when viewing the bidirectional turnout B from the main terminal 2.

In order to eliminate reflections, the bidirectional splitter B changes the input impedance Z when viewed from the main line terminal 1 to the characteristic impedance Z of the signal main line 4B. Make it equal to 2. Here, as an example, when the input impedance Z of the bidirectional splitter B is calculated when the attenuation amount (attenuation A) at the branch terminal 3 is designed to be -20 db, it is as follows.

First, with the attenuation amount A and a = 10'', the winding ratio N of the autotransformer T is determined from the following equation (1).

Since the above a is 0.1 when the attenuation amount A is -20,
Substituting this into equation (1) yields the winding ratio N=5.

Then, the linear equation (2
), the number of turns n1 of the primary winding of the autotransformer T and the number n2 of turns of the secondary winding are set.

n1+n.

Formula (2)...N=□ Since the winding ratio N was 5, n-engineering satisfies this.

The value of B2 is 1, for example, n = 12. n,=3.

Next, the input impedance Z0 of the device connected to the branch terminal 3 and the characteristic impedance Z03 of the signal main line 4B
is, for example, 75Ω. Therefore, the resistance value of the resistance element R is also set to 75Ω. At this time, autotransformer T,
The impedance Z1 when the circuit consisting of the resistive element R and the impedance Z0 is viewed from the connection point 5 is expressed by the following formula (3
)become that way.

Formula (3) zz=(R+Z,,)N”= 3750
0 Also, the equivalent circuit when looking at the bidirectional turnout B from the main terminal 1 is shown in Figure 10, and the main terminal 1
On the other hand, the voltage standing wave ratio VSWR of the circuit shown in FIG. Since it is determined by dividing the impedance Z when looking at the device B by the characteristic impedance z0 of the signal trunk line 4B, the following equation (5) is obtained.

Equation (5) ・VSWR=T= 1.02 In this way, the impedance Z of the bidirectional branch B when there is one branch terminal 3 is almost equal to the characteristic impedance Z, (75Ω), and VSWR is "1".

[Problem that the invention seeks to solve]

However, for example, when a plurality of OA devices and terminals are arranged in one room, it is desirable to provide a plurality of branch terminals in one branch and connect the plurality of devices to the signal main line. However, in the conventional bidirectional branch circuit, in order to reduce the number of branch terminals to two, the branch circuit BC in FIG.
Since the two signal main lines 4A are connected in parallel, the equivalent circuit is as shown in FIG. The impedance Z when viewed from the main terminal 1 is 72.13Ω, and the VSWR is 1.039. In other words, when the number of one branch terminals is reduced to two, the input impedance Z of the branch circuit B decreases, and the VSWR deteriorates.6 Furthermore, when the number of one branch terminals 3 is reduced to three, the equivalent circuit of the bidirectional branch circuit B is as follows. 1
It is expressed as shown in Figure 2, and the input impedance Z is 70.
The resistance further decreases to 82Ω, and the VSWR further deteriorates to 1.059. As described above, the conventional bidirectional branching device has a problem in that when the number of branch terminals is increased, the input impedance Z decreases and the VSWR deteriorates.

The present invention has been made to solve the above problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique for suppressing a drop in input impedance, which becomes noticeable as the number of branch terminals increases, in a bidirectional branch, and making the input impedance approximately equal to the characteristic impedance of a signal main line.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

In order to achieve the above object, in the present invention, a first output terminal is provided via a resistive element from the middle point of the winding, one end of which is connected to the signal main line and the other end of which is grounded. A primary winding is connected to the branch circuit and the signal main line, one end of the secondary winding is grounded, and the other end is grounded via the resistive element. A second branch circuit is provided with two output terminals.

Further, a first branch circuit is provided with a first output terminal via a resistive element from an intermediate point of a winding whose one end is connected to the signal main line and whose other end is grounded, and a primary winding connected to the signal main line. is connected, one end of the secondary winding is grounded, and the other end is grounded via a resistance element, and a second output terminal is provided on the resistance element side of the secondary winding. A plurality of sets of the first branch circuit and the second branch circuit are provided such that the branch circuit and the second branch circuit are connected to the signal main line after the first branch circuit. be.

[Effect]

According to the above-mentioned means, the first branch circuit is connected in parallel to the signal main line, and the second branch circuit is connected in series, so that the bidirectional branch reduced by the first branch circuit Since the second branch circuit increases the input impedance of the device, the input impedance can be made approximately equal to the characteristic impedance. That is, since the first branch circuit and the second branch circuit mutually cancel out deviations from the characteristic impedance, the input impedance can be made approximately equal to the characteristic impedance. From this, the voltage standing wave ratio VSWR can be approximately 141++.

Further, a plurality of sets of first branch circuits and second branch circuits are provided on the signal main line, with the second branch circuit being set to compensate for the attenuation of the signal main line impedance due to the connection of the first branch circuit. By the way.

The input impedance of a bidirectional splitter having many branch terminals, such as four, six, or more, can be made approximately equal to the characteristic impedance, and the VSWR can be made approximately equal to "1".

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

In addition, in an attempt to explain the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof will be omitted.

FIG. 1 is a block diagram of a network constructed using bidirectional branching switches according to an embodiment of the present invention.

In FIG. 1, 6 is a CPU (central processing unit), 7 is a terminal, B1. B,,B,is a bidirectional turnout. The bidirectional turnout B1 has two branch terminals, the bidirectional turnout B2 has three branch terminals, and the bidirectional turnout B2 has four branch terminals. For this reason, when a plurality of terminals 7 are arranged in one room, for example, the plurality of terminals 7 can be connected to the signal main line 4B by one bidirectional branch B. Note that the terminal 7 is
It may be a local device such as A equipment or a measuring instrument, or it may be a CPU.
5 may be replaced with the terminal 7 or the other device mentioned above, that is, the terminal or OA equipment.

The network may be configured only with measuring instruments and the like.

Next, FIG. 2 shows a circuit configuration of a bidirectional branch B having two branch terminals 3. In FIG. 2, 1 and 2 are main terminals, 4A is an internal signal main line, and BCl and BC2 are branch circuits, which are provided with two branch terminals 3A and 3B. Branch circuit BCI has the same configuration as that shown in FIG. The branch circuit BC2 includes a transformer T2 and a resistive element R.
It consists of The primary winding n1 of the transformer T2 is connected in series to the internal signal main line 4A, and the secondary winding n2 has one end grounded and the other end connected to the resistance element R.

The other end of the resistive element R is grounded.

The branch terminal 3B is provided at the connection portion of the resistive element R of the secondary winding n3. The resistance element R is connected to the input impedance ZI,3 of the device connected to the branch terminal 3B and the branch circuit BC2.
This is for matching with.

In the branch circuit BCI, when n□=12 and n2=3, the input impedance Z□ when looking at the branch circuit BCI from the connection point 5 is 3750Ω.

On the other hand, from the primary winding n1 of the transformer T2 to the branch circuit BC2
The input impedance Z2 when looking at is determined as follows.

First, the winding ratio N of the transformer T2 is determined from the following equations (6) and (7).

^ a=10 A; Reduction formula (7)...N=- And the input impedance Z2 of the branch circuit BC2 is:
It is determined from the following equation (8).

Here, as an example, when the attenuation amount (attenuation A) is -20 db, the branch circuit BC2 is connected to the primary winding n1.
Let's calculate the impedance Z2 when viewed from the side.

First, the turns ratio N of nl and B2 is 0 from the above equation (6).
．． 2 is sufficient. The number of windings satisfying this winding ratio N is, for example, n=2, n2=10. Then, the impedance Z2 seen from the n1 side is determined from the above equation (8) as follows: Z2=1.5Ω. This impedance Z2 is inserted in series into the internal main line 4A, as shown in FIG. In other words, impedance 2□ is characteristic impedance z0
while the impedance Z
2 is connected in series to the characteristic impedance Z0. Therefore, the input impedance Z when viewed from the main terminal 1 of the circuit of FIG. 3 is calculated from the following equation (9).

Near 5Ω In other words, when two branch circuits BCI are connected to the internal signal main line 4A, the input impedance Z of the main line terminal 1 is 72
．． 13Ω, whereas in the bidirectional splitter B in Fig. 2, the input impedance 2 is equal to the characteristic impedance Z.
, (75Ω). On the other hand, in the VSWR, when the signal main line 4B (zoz) is connected to the main line terminal 1,
This is the value obtained by dividing the input impedance Z when viewed from the main line terminal 2 by the characteristic impedance Z0. here,
The VSWR when viewed from main line terminal 1 and main line terminal 2 are equal. Therefore, the VSWR in FIG. 3 is approximately "1". In this way, in the bidirectional branch B having two branch terminals 3A and 3B, the first
branch circuits BCI are connected in parallel, and a second branch circuit BCI is connected in parallel.
By connecting C2 in series, the second branch circuit BC2 increases the input impedance Z of the bidirectional branch B which has been reduced by the first branch circuit BC1, so that the input impedance 2 is changed to the characteristic impedance Z0. can be made equal to In other words, since the first branch circuit BCI and the second branch circuit BC2 mutually compensate for the deviation of the input impedance Z from the characteristic impedance z0, the input impedance Z can be made equal to the characteristic impedance z0. From this, the voltage standing wave ratio VSWR
can be made almost “1”.

Here, the frequency characteristics of the bidirectional splitter B are shown in FIG.

FIG. 4 is a Smith chart for explaining the frequency characteristics of the bidirectional splitter B that was tested by the inventor, and the horizontal axis R
is the resistance, the vertical axis or reactance, and the concentric circles indicated by dotted lines or solid lines indicate the voltage standing wave ratio VSWR.

The frequency characteristics are measured in the range of 1 mega7 to 40 mega7.

Graph A shows that the branch circuit BCI is connected to two internal signal main lines 4.
The frequency characteristics when connected to A to form a bidirectional branch B are shown. Graph B is.

It shows the frequency characteristics when two branch circuits BC2 are connected between the internal signal main line 4A to form a bidirectional branch B. Further, graph C shows the frequency characteristics when the bidirectional branch B is configured by connecting one branch circuit BC1 and one branch circuit BC2 to the internal signal main line 4A.

As shown in FIG. 4, the branch circuit BCI and the branch circuit BC
2 and one each, the vSWR becomes 1.02.
You can do the following.

Next, the circuit configuration of the bidirectional switch B when three branch terminals are provided will be explained using FIG. 5.

FIG. 5 is a circuit diagram of a bidirectional switch B having three branch terminals.

The bidirectional switch B shown in FIG.
It has CI, BC2, and BC3. 3A, 3B, 3C
are the branch terminals of the respective branch circuits BCI, BC2, BC3. And the 1 branch circuit BC3 is the branch circuit BCI
It has the same circuit configuration as , and Zo4 is the input impedance (75Ω) of the device connected to the branch terminal 3C. Therefore, the impedance Z when viewed from the connection point 5 of the branch circuit BC3 is 3
It becomes 750Ω. The input impedance Z when looking at the bidirectional branch circuit B from the main terminal 1 is given by the following formula (1
0).

= 73.5Ω In other words, when three branch circuits BCI are connected in parallel to the internal signal main line 4A, the input impedance Z at the main line terminal 1 is 70.82Ω, whereas in the circuit of FIG. Since the branch circuit BC1 and the branch circuit BC2 mutually cancel the deviation from the characteristic impedance z0, the input impedance Z can be made the same as the input impedance Z of the bidirectional branch B when the number of branch terminals is one.

Next, FIG. 6 shows a circuit diagram of the bidirectional branch circuit B when six single branch terminals 3 are provided.

In Figure 6, 3A, 3B, 3G, 3D, 3E, 3F
is a branch terminal, Zo, ~201 is a branch terminal 3A, 3
This is the input impedance of the device connected to B, 3C, 3D, 3E, and 3F, and is 75Ω.

The circuit shown in FIG. 6 is the branch circuit BCI shown in FIG.
and branch circuit BC2 are connected to the repeating internal signal main line 4A. Therefore, branch circuit BC
I and the branch circuit BC2 have a characteristic impedance Z. Since the deviations from
Even when the pair is repeatedly provided, the input impedance 2 when viewed from the main line terminal 1 is Z = approximately 75Ω, and V
SWR = approximately 1.

Note that the number of pairs of branch circuits BCI and BC2 is not limited to three, and bidirectional branch B can be configured by providing four, five, or more pairs.

The present invention has been specifically explained above using examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

For example, a bidirectional branching switch according to the present invention may have a circuit configuration as shown in FIG.

〔Effect of the invention〕

A brief explanation of the effects of typical inventions disclosed in this application is as follows.

A first branch circuit is provided with a first output terminal via a resistive element from an intermediate point of a winding whose one end is connected to the signal main line and whose other end is grounded, and a primary winding is connected to the signal main line. A second winding is connected to the resistive element side of the secondary winding in a circuit in which one end of the secondary winding is grounded and the other end is grounded via the resistive element.
By providing a second branch circuit provided with an output terminal.

Since the first branch circuit and the second branch circuit mutually cancel out the deviation of the input impedance Z from the characteristic impedance z0, the input impedance Z can be made almost equal to the characteristic impedance Z.

From this, the voltage standing wave ratio VSWR can be made approximately "1".

Further, a first branch circuit is provided with a first output terminal via a resistive element from an intermediate point of a winding whose one end is connected to the signal main line and whose other end is grounded, and a primary winding connected to the signal main line. is connected, one end of the secondary winding is grounded, and the other end is grounded via a resistance element, and a second output terminal is provided on the resistance element side of the secondary winding. By providing a plurality of sets of the first branch circuit and the second branch circuit such that the branch circuit and the second branch circuit are connected to the signal main line after the first branch circuit. , since each pair of branch circuit BCI and branch circuit BC2 cancels out deviations from characteristic impedance Z0, input impedance Z when viewed from main terminal 1 should be made almost equal to characteristic impedance Z0. Can be done. Therefore, even in a bidirectional branching circuit having many branch terminals, such as four, six, or more, the voltage standing wave ratio VSWR can be made approximately '1'.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a network constructed using bidirectional branching switches according to an embodiment of the present invention. Fig. 2 is a circuit diagram of a bidirectional turnout according to an embodiment of the present invention when two branch terminals are provided, and Fig. 3 is an equivalent circuit diagram of the bidirectional turnout shown in Fig. 2. , Figure 4 is a Smith chart showing the frequency characteristics of the bidirectional splitter. FIG. 5 is a circuit diagram of a bidirectional branch circuit B having three branch terminals, FIG. 6 is a circuit diagram of a bidirectional branch circuit B when six branch terminals 3 are provided, and FIG. FIG. 7 is a circuit diagram showing a modification of the bidirectional branch circuit of the present invention. Fig. 8 is a block diagram of a network configured with a conventional bidirectional switch; Fig. 9 is a circuit diagram of a conventional bidirectional switch having one branch terminal; Fig. 10 is a block diagram of a network configured with a conventional bidirectional switch The equivalent circuit of the bidirectional turnout shown in Figure 11 is the equivalent circuit of the bidirectional turnout when two conventional branch terminals are provided, and Figure 12 is the equivalent circuit of the bidirectional turnout when three conventional branch terminals are provided. This is the equivalent circuit of a bidirectional turnout when In the diagram, 1.2... Main terminal, 3... Branch terminal, 4A
... Internal signal main line, 4B... Signal main line, B... Branch circuit, BC... Branch circuit.

Claims (3)

[Claims] (1) A first branch circuit in which a first output terminal is provided via a resistive element from the middle point of a winding whose one end is connected to the signal main line and the other end is grounded, and a primary winding connected to the signal main line. A second output terminal is provided on the resistance element side of the secondary winding of a circuit in which wires are connected in series, one end of the secondary winding is grounded, and the other end is grounded via a resistance element. A bidirectional turnout comprising a second branch circuit. (2) A first branch circuit in which a first output terminal is provided via a resistive element from the middle point of a winding whose one end is connected to the signal main line and the other end is grounded, and a primary winding connected to the signal main line. A second output terminal is provided on the resistance element side of the secondary winding of a circuit in which wires are connected in series, one end of the secondary winding is grounded, and the other end is grounded via a resistance element. A plurality of sets of the first branch circuit and the second branch circuit are provided such that the second branch circuit and the second branch circuit are connected to the signal main line after the first branch circuit. A bidirectional turnout characterized by: (3) The second branch circuit is set to an equivalent impedance that compensates for the attenuation of the signal trunk impedance due to the connection of the first branch circuit. bidirectional turnout.