JPH11251858A - Variable attenuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and to prevent the reduction of the variable width of attenuation in a variable attenuator to be used at varying of the level of a transmission signal by communication equipment. SOLUTION: This variable attenuator is provided with a bi-partite means 6 provided with an input port 2, grounded first and second distribution ports 3, 4 and an isolation port 5 and branching a signal inputted to the port 2 into first and second branch signals to send to the ports 3 and 4 and an impedance means 7 reflecting the second branch signal inputted through the port 4 to the port 4 by a phase and reflection, corresponding to an applied control signal when the second branch signal is inputted. Then the means 6 is constituted to fetch a signal produced by mixing a signal obtained by sending the first branch signal to the grounded first distribution port 3 and totally reflecting it and the second branch signal reflected from the means 7 and to fetch a signal attenuated corresponding to the reflection from the port 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable attenuator used to vary the level of a transmission signal in a communication device.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a main part of a conventional variable attenuator. As shown in FIG. 7, capacitors 13 and 15 and pin diodes 14 and 16 are connected in series to the respective distribution ports 3 and 4 of the 90-degree hybrid 6, and the other ends of the pin diodes 14 and 16 are grounded.

[0005] One end of each of coils 11 and 12 is connected between capacitors 13 and 15 and pin diodes 14 and 16, and the other end of each coil is connected to control terminal 1.
The signal applied to the input port 2 of the 90-degree hybrid 6 configured as described above is internally branched toward the distribution ports 3 and 4, and the phase difference between the divided signals at each distribution port is 90 degrees. .

[0004] For example, the phase of the signal distributed to the distribution port 4 side is -9 with respect to the phase of the signal distributed to the distribution port 3 side (the same phase as the phase of the signal applied to the input port).
It becomes 0 degrees.

The signals distributed to the distribution ports 3 and 4 are reflected to the isolation port 5 by the impedance of the pin diodes 14 and 16. At this time, a phase difference of 90 degrees occurs between the signals reflected from the distribution ports 3 and 4 to the isolation port 5, as opposed to when the signal is branched from the input port 2 to the distribution ports 3 and 4. .

For example, from the input port 2 to the distribution port 3,
When the phase difference between the distribution ports 4 is as described above, the phase of the signal from the distribution port 3 side is -90 with respect to the phase from the distribution port 4 side.
Degree.

Therefore, the phase difference between the signal from the distribution port 3 and the signal from the distribution port 4 is eliminated, and the signals are combined with the same phase and equal amplitude and output from the isolation port 5.
Here, the amount of attenuation of the variable attenuator is determined by each distribution port 3,
4 is controlled by the amount of reflection from each distribution port 3,
4 is controlled by the impedance of each of the pin diodes 14 and 16,
Is controlled by a signal (DC current) from the control terminal 1.

That is, since the impedance changes,
The amount of reflection changes. For example, each pin diode 14, 1
When the impedance of the pin diode 6 approaches the characteristic impedance of the 90-degree hybrid 6, the amount of reflection at the pin diode decreases, so that the amount of attenuation increases.
If the impedances 4 and 16 are made equal to the characteristic impedance of the 90-degree hybrid 6, the amount of reflection at the pin diode becomes zero, so that the attenuation becomes the maximum value, and the output from the isolation port 5 becomes zero.

That is, in order to maximize the amount of attenuation, the impedance of each of the pin diodes 14 and 16 must be made equal to the characteristic impedance of the 90-degree hybrid 6 at the same time.

Conversely, when the impedance of each of the pin diodes 14 and 16 is moved away from the characteristic impedance of the hybrid 6 by 90 degrees, the amount of reflection increases and the amount of passage loss, that is, the amount of attenuation, decreases.

Therefore, when the impedance of each of the pin diodes 14 and 16 is maximum or minimum, the distance is farthest from the characteristic impedance of the 90-degree hybrid 6, so that the passage loss, that is, the attenuation is the minimum value.

The impedance component of each of the pin diodes 14 and 16 is mainly dominated by a resistance component.

[0013]

As described in detail above, the impedance of the pin diodes 14, 16 is 90.
Since the reflection is non-reflective when the characteristic impedance is equal to the characteristic impedance of the hybrid 6, the attenuation amount becomes the maximum value. At this time, if the control voltages applied to the pin diodes 14 and 16 are not the same, reflection occurs on one of the pin diodes.

That is, if the pin diodes 14 and 16 have the same characteristic with respect to the control voltage, the control voltage of the pin diode having the same impedance as the characteristic impedance of the 90-degree hybrid 6 becomes the same. The impedance of 14, 16 is 9
It becomes the same as the characteristic impedance of the 0-degree hybrid 6.

Therefore, there is no reflection from both pin diodes 14 and 16, and the attenuation becomes the maximum value. But,
If the balance between the characteristic impedances of the pin diodes 14 and 16 is lost, the reflected signal is output to the output side from the broken distribution port, so that the variable width of the attenuation decreases.

If a control circuit for equalizing the impedance characteristics of each of the pin diodes 14 and 16 is used, there arises a problem that the cost is increased, and further, the manufacturability and miniaturization are difficult.

An object of the present invention is to reduce the size and prevent the variable width from being reduced.

[0018]

FIG. 1 is an explanatory view of the principle of the first present invention, and FIG. 2 is an explanatory view of the principle of the second present invention. 1 and 2, 2 is an input port, 3 and 4 are distribution ports, 5 is an isolation port, 6 is two distribution means, 7
Is impedance variable means.

According to a first aspect of the present invention, there is provided an input port, a grounded first distribution port, a second distribution port, and an isolation port.
Two distribution means for branching into a first branch signal and a second branch signal and sending out the signals to the first distribution port and the second distribution port, and the second branch signal input via the second distribution port. Time,
Impedance varying means for reflecting the reflected light to the second distribution port with a phase and a reflection amount corresponding to the applied control signal is provided.

The two distribution means is connected to the first grounded ground.
The signal obtained by transmitting the first branch signal to the distribution port and totally reflecting the signal and the second branch signal reflected from the impedance variable means are attenuated in accordance with the amount of reflection from the isolation port. The signal is taken out.

According to a second aspect of the present invention, there is provided an input port, a first distribution port in an open state, a second distribution port, and an isolation port. A second distribution means for branching into two branch signals and sending them to the first distribution port and the second distribution port; and a control signal applied when the second branch signal is input via the second distribution port. Impedance variable means for reflecting light to the second distribution port with a corresponding phase and reflection amount is provided.

The two distribution means combines the first branch signal transmitted to the open first distribution port and reflected in the same phase with the second branch signal reflected by the impedance variable means. Then, the signal attenuated according to the amount of reflection was taken out from the isolation port.

Here, the principle of the present invention will be described with reference to FIGS. Generally, the phase relationship between the traveling signal to the distribution port 4 and the reflection signal from the distribution port 4 is such that the pin diode, that is, the impedance Z _IN of the impedance variable means 7 is smaller than the characteristic impedance Z _OUT of the 90-degree hybrid 6. In this case, when the phase of the reflected signal is opposite to the phase of the traveling signal and is inverted by 180 degrees, the impedance of the pin diode, that is, the impedance Z _IN of the impedance variable means 7 is larger than the characteristic impedance Z _OUT of the 90-degree hybrid 6. The phase of the reflected signal is in phase with the traveling signal.

In FIG. 1, the signal passing through the input port 2 and applied to the 90-degree hybrid 6 is branched here, and the phase difference between the signals at the distribution ports 3 and 4 is 90.
Degree.

Since the distribution port 3 is short-circuited, the traveling signal input to the distribution port 3 is totally reflected.
At this time, the phase of the reflected signal is 18
It reverses by 0 degree and returns to 90 degree hybrid 6.

On the other hand, the amount of reflection and the phase of the traveling signal input to the distribution port 4 are controlled by the impedance variable means 7, and the controlled phase is 90 as described above.
Due to the magnitude relationship between the characteristic impedance of the degree hybrid 6 and the impedance of the impedance varying means 7, the phase of the reflected signal returning from the impedance varying means 7 to the 90 degree hybrid 6 progresses from the 90 degree hybrid 6 to the impedance varying means 7. The phase of the signal is in-phase or inverted by 180 degrees.

Therefore, in the 90-degree hybrid 6, the reflected signals from the distribution ports 3 and 4 are isolated by giving a phase difference of 90 degrees opposite to the phase difference between the input port 2 and the distribution ports 3 and 4. Output to port 5.

At this time, if the reflected signal returned through the distribution port 4 has a phase relationship such that the reflected signal reflected by the distribution port 3 cancels the returned signal, the unsolation port 5
Does not appear, and the attenuation is maximized.

However, if the phase of the reflected signal returned through the distribution port 4 is the same as the phase of the reflected signal reflected at the distribution port 3, the output from the isolation port 5 becomes maximum, and the attenuation is reduced. Will be minimal.

That is, by varying the impedance value of the impedance varying means 7, a variable attenuator capable of varying the amount of attenuation from maximum to minimum is obtained. In FIG. 2, the distribution port 3 of the 90-degree hybrid 6 is open unlike the case of FIG. In this case, the reflected signal returning to the distribution port 3 has the same phase as the traveling signal from the distribution port toward the open end.

Accordingly, the phase at which the amount of attenuation becomes maximum to minimum is shifted by 180 degrees as compared with the case of FIG. 1, but a variable attenuator similar to that of FIG. 1 can be obtained with such a configuration.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a block diagram of a main part of a first embodiment of the present invention, FIG. 4 is an operation explanatory diagram of FIG. 3, and FIG. 5 is a block diagram of a main part of a second embodiment of the present invention. 6 is an explanatory diagram of the operation of FIG.

The operation of FIGS. 3 and 5 will be described with reference to FIGS.
4 and FIG. _OUTIs a 90 degree hive
Output impedance of lid 6, Z_INIs impedance
This is the input impedance of the variable means.

The parts described in detail above will be described briefly, and the parts of the present invention will be described in detail. The same reference numerals indicate the same objects throughout the drawings. First,
In FIG. 3, 7 is an impedance variable means, 71 is a coil, 72 is a capacitor which cuts the application of a DC voltage, but does not affect a traveling signal or a reflected signal.
Reference numeral 3 denotes a pin diode whose resistance changes in accordance with the level of a control signal applied via the coil.

As described above, when Z _OUT > Z _IN , 9
The phase of the reflected signal returning to the 0-degree hybrid 6 is opposite to the phase of the traveling signal traveling to the 90-degree hybrid 6, and when Z _OUT <Z _IN , the phase of the reflected signal returning to the 90-degree hybrid 6 is The phase of the traveling signal traveling to the 90-degree hybrid 6 becomes the same.

Next, in FIG. 4, the signal input to the input port 2 is distributed by the 90-degree hybrid 6 to the distribution port 3,
The signal branched to the distribution port 3 is, for example, -90 with respect to the signal branched to the distribution port 3 (the same phase as the signal input to the input port). Degree.

Now, the traveling signal 'output from the distribution port 3 advances in the same phase state, and the reflected signal' whose phase is shifted by 180 degrees reflected by the short-circuit portion is input to the 90 degree hybrid 6 through the distribution port 3. Here, a signal 'whose phase is shifted by 90 degrees is obtained.

On the other hand, the traveling signal output from the distribution port 4 is applied to the impedance varying means 7 with a phase of 90 degrees. At this time, if Z _OUT > Z _IN , the phase of the reflected signal from the impedance variable means is opposite to the phase of the traveling signal, so the signal shown in ₁ is obtained, and Z _OUT <Z _IN
If _IN, since the phase of the reflected signal from the variable impedance unit 7 are in phase with respect to the phase of the progressive signal, ₂
The signal shown in FIG.

[0039] Therefore, the reflected signal _1/2 from the variable impedance unit 7 is input from the distribution port 4 to 90 degree hybrid 6, signal _1/2 of the same phase are obtained, combined with the reflected signal 'from the distribution port 3 And output from the isolation port 5. Where Z _OUT > Z _IN
In the case of ( ₁₎ , the signal becomes plus signal ₁ and the transmission loss becomes minimum. When Z _OUT <Z _IN , the signal becomes minus signal- ₂ and the loss becomes maximum.

That is, the amount of attenuation is controlled by the variable impedance means 7, and the reflected signals reflected from the respective distribution ports 3, 4 are provided when the impedance of the variable impedance means 7 is between the minimum and the characteristic impedance of the 90-degree hybrid 6. Are combined in phase at the isolation port 5 (see signal ₁ + signal '), and as the impedance of the impedance varying means 7 approaches the characteristic impedance of the 90-degree hybrid 6, the signal ₁ reflected from the distribution port 4 decreases, Since the output is only signal ',
The amount of attenuation increases, and the passage loss increases.

When the impedance of the impedance changing means 7 becomes equal to the characteristic impedance of the 90-degree hybrid 6, the distribution port 4 is in a non-reflection state, and there are no signals ₁ and ₁ to be reflected.
Only the signal ′ reflected from is output to the isolation port 5.

Further, while the impedance of the impedance varying means 7 is from the characteristic impedance of the 90-degree hybrid 6 to the maximum, the signals reflected from the respective distribution ports are combined in the isolation port 5 in opposite phases.

That is, as the impedance of the impedance varying means 7 moves away from the characteristic impedance of the 90-degree hybrid 6, the signals ₂ , ₂ reflected from the distribution port 4 increase, and the amount of attenuation further increases.

When the amplitudes of the signals reflected from the respective distribution ports 3 and 4 are equal, they have the same amplitude in opposite phase (signal′−signal ₂ = 0), the attenuation becomes maximum, and the output from the isolation port 5 is obtained. Is gone.

In FIG. 5, the impedance varying means 7 is connected to the distribution port 4 of the 90-degree hybrid 6 as in the case of FIG. 3, but the distribution port 3 is open. Is different from the case.

Therefore, the traveling signal from the 90-degree hybrid 6 to the distribution port 3 is reflected at the open end in the same phase and returns to the 90-degree hybrid 6 as a reflected signal. The phase relationship between the traveling signal and the reflected signal is the same as in FIG.

In FIG. 6, the signal input to the input port 2 is split by the 90-degree hybrid 6 into a signal ′ for the distribution ports 3 and 4, and the phase difference of the split signal at each of the distribution ports 3 and 4. Is 90 degrees.

Then, the traveling signal ′ coming out of the distribution port 3 is reflected in phase at the open end, and the phase of the reflected signal ′ is shifted by 90 degrees by the 90-degree hybrid 6 (see the signal ′) and appears at the isolation port 5.

On the other hand, the traveling signal output from the distribution port 4 is applied to the impedance varying means 7. At this time, Z
_{If OUT} > Z _IN , the reflected signals ₁ , ₁ from the impedance variable means 7, if Z _OUT <Z _IN , the reflected signal
₂ , ₂ pass through the distribution port 4 of the 90-degree hybrid 6 and appear on the isolation port 5 side in the same phase.

Therefore, when Z _OUT <Z _IN , the transmission loss becomes minimum, and when Z _OUT > Z _IN , the transmission loss becomes maximum.
That is, while the impedance of the impedance varying means 7 is from the maximum to the characteristic impedance of the 90-degree hybrid 6, the phases of the signals reflected from the distribution ports 3, 4 are combined in the same phase (see signal '+ signal ₂ '). ), The impedance of the impedance varying means 7 is 9
As the characteristic impedance of the hybrid 6 approaches 0 degrees, the signal ₂ reflected from the distribution port 4 decreases,
The amount of attenuation increases.

When the impedance of the impedance varying means 7 becomes equal to the characteristic impedance of the 90-degree hybrid 6, the distribution port 4 becomes non-reflective (signal
₂ , ₂ = 0), signal reflected from distribution port 3
Only the signal is output from the isolation port 5.

Further, while the impedance of the impedance varying means 7 is from the characteristic impedance of the 90-degree hybrid 6 to the minimum, the signals reflected from the distribution ports 3 and 4 are combined in opposite phases (signal '-signal ₁ ). As the impedance of the impedance varying means 7 moves away from the characteristic impedance of the hybrid 6 by 90 degrees, the signals ₁ , ₁ reflected from the distribution port 4 increase, and the attenuation increases.

When the amplitudes of the signals reflected from the respective distribution ports 3 and 4 are equal, they have the same amplitude in opposite phase (signal '-signal ₁ ), and the attenuation becomes maximum. Therefore,
The transmission signal can be attenuated only by providing the impedance changing means in only one of the distribution ports.

[0054]

As described above in detail, according to the present invention, there is an effect that the variable width of the attenuation amount is large, the cost is low, and the contribution to manufacturability and miniaturization is large.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the first invention.

FIG. 2 is a diagram illustrating the principle of the second invention.

FIG. 3 is a configuration diagram of a main part of the first embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of FIG. 3;

FIG. 5 is a configuration diagram of a main part of a second embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of FIG. 5;

FIG. 7 is a configuration diagram of a main part of a conventional variable attenuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control terminal 2 Input port 3 and 4 Distribution port 5 Isolation port 6 2 Distribution means 7 Impedance variable means 11, 12 Coil 13, 15 Capacitor 14, 16 pin diode 71 Coil 72 Capacitor 73 Diode

Claims (2)

[Claims] An input port, a grounded first distribution port, a second distribution port, and an isolation port, wherein a signal input to the input port is divided into a first branch signal and a second branch signal.
(2) dividing means for branching to the first distribution port and sending it to the first distribution port and the second distribution port, and the control applied when the second branch signal is input via the second distribution port. With the phase and the reflection amount corresponding to the signal, the second
And a variable impedance means for reflecting light at a distribution port of the first and second distribution ports.
A signal which is transmitted and totally reflected and a second branch signal reflected from the impedance varying means are combined to extract a signal attenuated from the isolation port in accordance with the amount of reflection. A variable attenuator characterized in that: 2. An input port, an open first distribution port, a second distribution port, and an isolation port, wherein a signal input to the input port is divided into a first branch signal and a second branch signal.
(2) dividing means for branching to the first distribution port and sending it to the first distribution port and the second distribution port, and the control applied when the second branch signal is input via the second distribution port. With the phase and the reflection amount corresponding to the signal, the second
And a variable impedance means for reflecting light at the distribution ports of the first and second distribution ports.
And a second branched signal reflected by the variable impedance means is combined with the signal reflected by the impedance varying means, and a signal attenuated from the isolation port in accordance with the amount of reflection is obtained. A variable attenuator characterized in that it is taken out.