JPH087774A - Microwave tube with built-in protection circuit - Google Patents

Abstract

PURPOSE:To provide a microwave tube which can protect an electron tube, etc., as component member from an excessive reflected power by allowing the microwave tube to incorporate a protection circuit for the excessive reflected power given from the load side, wherein it is not required to install additionally any reflected power sensing means, control circuit to make a protective operation for eventual excessive power, etc., separately in a position outside the microwave tube. CONSTITUTION:A microwave tube is equipped in its input part with a variable attenuator 4, and also in the output part with a directional coupler 5 to extract the reflected power to the microwave tube, a wave detector 6 to be connected with a diverging output part of the directional coupler, and a controller 7 which controls the attenuating amount of the attenuator according to the detecting output of the detector. When the reflected power from the load side to the microwave tube enlarges, the power fed to the microwave tube is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave tube for amplifying microwave power, and more particularly to a high power microwave tube used for an amplifier such as microwave communication and radar transmitter.

[0002]

2. Description of the Related Art In a high-power microwave tube used for an amplifier for microwave communication or the like, when excessive reflected power enters the tube from an output end of the microwave tube, a crack occurs in a vacuum sealing ceramic window. May cause fatal damage such as. Therefore, it is necessary to provide a circuit for preventing excessive reflection power incidence on the microwave tube in view of the amplifier configuration.

However, conventionally, the reflected power suppressing circuit is not built in the microwave tube itself, and a protection circuit provided outside the microwave tube prevents the reflected power of the microwave tube from being exceeded when the reflected power becomes excessive. It had stopped working. An example thereof is shown in FIG. In FIG. 5, 21 is a conventional microwave tube without a built-in reflected power protection circuit, 22 is a microwave input end of the microwave tube, 23 is a microwave output end of the microwave tube, and 24 is a branching extraction of reflected power. Is a directional coupler, 25 is a detector, 26 is an excessive reflection power detection circuit, 27 is an amplifier control circuit, and 28 is a microwave tube power supply.

The microwave power a input from the microwave input end is power-amplified by the microwave tube 21, and the output power c passes from the microwave output end 23 through the directional coupler 24 to a load device such as an antenna. Supplied. The reflected power d generated due to the impedance mismatch in the load device passes through the directional coupler 24 and enters the microwave output end 23.

At this time, a part of the reflected power is extracted by the directional coupler 24 and supplied to the detector 25. The detector 25 outputs a detection output e proportional to the reflected power d,
When the detected output e is input to the excessive reflected power detection circuit 26 and exceeds the reflected power level allowed by the microwave tube 21, the excessive reflected power detection signal f is output to the amplifier control circuit 27. The amplifier control circuit 27 compares the excessive reflection power detection signal f with a preset reference level, and when the excessive reflection power detection signal f exceeds this level, the high voltage output of the microwave tube power supply 28 is used as a protection operation. Cut off. As a result, the output power of the microwave tube is cut off, the reflected power to the microwave tube also disappears, and the microwave tube is protected from the reflected power.

[0006]

In the above-mentioned conventional microwave tube, the reflected power detection means and the control circuit for performing the excessive reflected power protection operation are required outside the microwave tube. In addition, the circuit for controlling the protection operation has a part shared in a time-division manner with the various control circuits for the amplification device. Therefore, it takes time to detect the excess power and perform the protection operation. There was a delay, and the microwave tube might be damaged during that delay.

It has been proposed so far to incorporate the reflected power detecting means in the microwave tube (for example, Japanese Utility Model Laid-Open No. 58-26159), but a control circuit for performing the reflected power excessive protection operation is nevertheless provided. Since it needs to be added to the outside, the above problems cannot be solved. Further, when the impedance characteristic of a load device such as an antenna deteriorates below a certain limit, the line is generally cut off.

According to the present invention, all the protection circuit elements are incorporated in the microwave amplifier to enable a quick and reliable protection operation and the output power is reduced even if the characteristics of the load system are deteriorated. The objective is to realize a microwave tube that can wait for the arrival of maintenance personnel while continuing the operation without completely shutting it off.

[0009]

The present invention has the following means constitution in order to solve the above problems. That is, in the first aspect of the present invention, a microwave tube (1); and a variable attenuation that is provided in an input section of the microwave tube (1) and variably attenuates an input signal input to the microwave tube (1) by a control signal. A directional coupler (5) which is provided at the output of the microwave tube (1) and extracts reflected power from the load side; and a reflection extracted by the directional coupler (5) A detector (6) for detecting electric power; and a control signal for increasing / decreasing the attenuation amount of the variable attenuator according to the magnitude of the detection output of the detector (6) is output to the variable attenuator (4). This is a microwave tube with a built-in protection circuit, characterized in that a power supply type control circuit and are integrally configured.

In the second invention, the variable attenuator 4 is a PI.
This is an N diode microwave attenuator. Further, in the third invention, a light emitting diode 14 for emitting light as an alarm is added to the output of the passive control circuit 7 of the first or second configuration when the output level exceeds a predetermined level. It is a thing.

[0011]

The microwave tube of the present invention operates as follows. That is, the input power a from the microwave input end 2 is amplified by the microwave tube 1, passes through the directional coupler 5, and is supplied from the microwave output end 3 to a load (for example, an antenna device). If a mismatch occurs in the load device including the feeder to the antenna or the like, the degree of failure (VSW
The reflected wave corresponding to R) flows back from the load to the microwave tube.

A part of the reflected power is extracted by the directional coupler 5, detected by the detector 6 and supplied to the control circuit 7. A control current is output from the control circuit 7 when the reflected power exceeds a preset intensity, and the variable attenuator 4 is driven. The amount of attenuation of the variable attenuator is controlled in accordance with the degree of excess level of the reflected power to the microwave tube, which exceeds the set level. That is, the amount of attenuation is controlled to increase as the excess level increases. Therefore, the amount of amplified power input from the microwave input terminal 2 is controlled according to the excess intensity of the reflected power, so that even if a large amount of reflection occurs, the amplified power is fed to the microwave tube before it is destroyed. Input power, and hence output power, is suppressed and protected.

As shown in FIGS. 1 and 2, this built-in protection circuit is independent of the external circuit, and the power source detects and uses a part of the reflected power, and is not necessary again. This means that the response speed is much faster than that of the conventional control circuit sharing type protection circuit, and a reliable protection operation is guaranteed.

In the structure including the light emitting diode shown in FIG. 4, an excessive reflected power alarm can be issued while maintaining electrical isolation from the outside. In this case, by providing a light receiving element at an external light receiving site and receiving this signal, it can be utilized for notification or interruption.

[0015]

Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example thereof. 2 shows the connection of internal elements. 1 is a microwave tube such as a traveling wave tube or a klystron for amplifying a microwave signal, 2 is a microwave input end, 3 is a microwave output end, 4
Is a variable attenuator such as a PIN diode, 5 is a directional coupler for extracting the reflected power to the microwave tube, 6 is a detector such as a crystal diode, and 7 is the detection output of the detector 6 is preset. This is a control circuit that immediately changes the attenuation amount of the variable attenuator 4 when the level exceeds a certain level. The Zener diode 11 incorporated in the control circuit 7 has a critical voltage value selected to have a high value within a range in which the electron tube is not destroyed even in the worst load matching state.

As the resistor 12, the variable attenuator 4 is used.
The resistance value is selected to be as small as possible within the range in which the maximum value of the inflow current into the damping element (PIN diode) does not exceed the allowable value. As a result, even if a mismatch occurs in the load circuit, the attenuation amount of the variable attenuator 4 is controlled so that the reflected power falls within the allowable value of the electron tube, and an appropriate protection operation is secured. As a structure, all of these constituent elements are integrated together with the electron tube in a case made of a metal or plastic material to be compactly enclosed.

A second embodiment will be described. As shown in FIG. 3, in the second embodiment, all the diodes are reverse-polarized with respect to the first embodiment (FIG. 2). For this, a favorable polarity is selected depending on the PIN diode of the variable attenuator 4, the detector element of the detector 6, and the shape of these mounts.

The third embodiment will be described with reference to FIG. As shown in FIG. 4, the light emitting diode 14 is connected to the output section of the control circuit 7 through the resistor 13 in the microwave tube with a built-in protection circuit having the configuration and connection shown in the first or second embodiment. The light emitting portion of the light emitting diode is arranged toward the light transmitting window opened in the outer casing. By this, when the reflected power of the intensity passing through the control circuit is detected, the light emitting diode 14 emits light and is detected by the light receiving element provided outside, and the alarm notification and the high voltage circuit interruption are activated. It is available as a signal.

[0019]

As described above, since the microwave tube according to the present invention has the built-in anti-excessive-reflected-power protection circuit, the reflected-power detection means and the anti-excessive-reflected-power protection operation are newly provided outside the amplifier. Since it is not necessary to provide a control means or the like and the delay associated with the required operation time of the external control circuit is small, quick and reliable protection against excessive reflected power is guaranteed. Further, since it is not necessary to supply power to the control system from the outside as shown in FIG. 2 etc., the circuit configuration is simple and the reliability is improved accordingly.

Further, even if a spark accident occurs due to a high voltage circuit or microwave high power inside or near the microwave tube, the protection circuit is independent, so that damage caused by this spark can be prevented from occurring outside the electron tube. Less likely to affect parts. In addition, even if the characteristics of the load system including the antenna deteriorates and the reflected power to the microwave tube exceeds the limit value, transmission is not completely cut off as in the past, but the output is slightly reduced. However, there is an advantage that it is possible to wait for the arrival of maintenance personnel while continuing the operation within a range that the electron tube can withstand.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a configuration of the present invention.

FIG. 2 is a connection diagram showing an example of a circuit configuration of the present invention.

FIG. 3 is a connection diagram in which the polarities of the diodes according to the present invention are opposite to those in the case of FIG.

FIG. 4 is a connection diagram showing an example in which an alarm light generating element according to the present invention is added.

FIG. 5 is an example of a block diagram of a conventional protection circuit.

[Explanation of symbols]

 1,21 Microwave tube 2,22 Microwave input end 3,23 Microwave output end 4 Variable attenuator 5,24 Directional coupler 6,25 Detector 7 Control circuit 11 Zener diode 12,13 Resistor 14 Light emitting diode 26 Excessive Reflected Power Detection Circuit 27 Amplifier Control Circuit 28 Microwave Tube Power Supply a Input Power b Adjusted Input Power c Output Power d Reflected Power e Detection Output f Alarm Light

Claims (3)

[Claims] 1. A microwave tube (1); and a variable attenuator provided at an input portion of the microwave tube (1) for variably attenuating an input signal input to the microwave tube (1) by a control signal ( 4) and; a directional coupler (5) provided at the output of the microwave tube (1) for extracting reflected power from the load side; and a reflected power extracted by the directional coupler (5). A detector (6) for detecting; a non-feed type for outputting a control signal to the variable attenuator (4) for controlling the increase / decrease of the attenuation amount of the variable attenuator according to the magnitude of the detection output of the detector (6) A microwave circuit tube with a built-in protection circuit, characterized in that the control circuit and; 2. The microwave tube with a built-in protection circuit according to claim 1, wherein the variable attenuator (4) is a PIN diode type microwave attenuator. 3. The microwave tube with a built-in protection circuit according to claim 1, further comprising a light emitting diode that emits light when a control signal output from the parasitic control circuit exceeds a predetermined level.