ELECTRON GUN, ELECTRON TUBE AND HIGH-FREQUENCY CIRCUIT SYSTEM

Abstract

The purpose is to make it possible to autonomously suppress a reduction in an electron beam without providing a means for supervising the electron beam intensity of a monitor or the like. An electron gun, provided with: a heater (12) in which one terminal serves as a heater terminal (H) and the other terminal serves as a shared terminal (HK), and in which a low-voltage power supply (21) is connected between the terminals, the heater (12) generating heat due to a current being supplied from the low-voltage power supply (21); and a cathode electrode (11) connected to the shared terminal (HK) and heated by the heater (12) to discharge thermal electrons. A cathode current (Ik) due to the thermal electrons discharged from the cathode electrode (11), and a current (Ih) due to the low-voltage power supply, flow in opposite directions through the heater (12).

Claims

1. An electron gun comprising: a heater, including one terminal as a heater terminal and another terminal as a shared terminal, to generate heat by current supply from a low-voltage power supply being connected between the terminals; and a cathode electrode, connected to the shared terminal, to form thermal electrons by being heated by the heater; wherein a cathode current generated by thermal electrons formed by the cathode electrode and a current generated by the low-voltage power supply flow through the heater in opposite directions.

2. An electron tube comprising: a heater, including one terminal as a heater terminal and another terminal as a shared terminal, to generate heat by current supplied from a low-voltage power supply being connected between the terminals; a cathode electrode, connected to the shared terminal, to form thermal electrons by being heated by the heater; and a collector electrode that is an opposite electrode to the cathode electrode, wherein a high-voltage power supply is connected between the cathode electrode and the collector electrode, thermal electrons formed by the cathode electrode due to an electric field by the high-voltage power supply are collected by the collector electrode to make a cathode current flow via the heater, and the cathode current flows in a reverse direction to an electric current by the low-voltage power supply.

3. The electron tube according to claim 2, wherein the low-voltage power supply is a constant current power supply.

4. The electron tube according to claim 2, further comprising a control unit that controls the low-voltage power supply in such a way that a predetermined specified current flows through the heater; controls the high-voltage power supply in such a way that, when the heater reaches a constant temperature due to the specified current, the cathode current flows to the cathode electrode; and controls the low-voltage power supply in such a way that, after the cathode current has flowed, an electric current being supplied from the low-voltage power supply to the heater is increased by a value corresponding to the cathode current.

5. A high-frequency circuit system comprising: an electron tube according to claim 3; and a power supply to supply electric power to the electron tube.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a block diagram of an electron tube according to a present example embodiment.

[0026] FIG. 2 is a diagram illustrating time changes of a low-voltage current, a heater current and a cathode current, and (a) is a diagram describing a case when Ik=0, (b) is a diagram when making a cathode current Ik flow, (c) is a diagram when adjusting a low-voltage current Ih, and (d) is a diagram illustrating a self-compensation operation of a heater current If.

[0027] FIG. 3 is a block diagram of an electron tube to be applied to illustration of the related technology.

DESCRIPTION OF EMBODIMENTS

[0028] An example embodiment of the present invention will be described. FIG. 1 is a block diagram of a high-frequency circuit system 3 including an electron tube 2 according to the present embodiment. The high-frequency circuit system 3 includes the electron tube 2 and a power supply to supply electric power to the electron tube 2, and, for example, there are illustrated a high power amplifier (HPA) that amplifies a microwave in order to transmit information such as images, data, sound and the like in satellite communication, ground microwave communication or the like, a microwave power module (MPM) that is a modularized version of HPA or the like.

[0029] The electron tube 2 includes a cathode electrode 11, a heater 12, a helix electrode 13 and a collector electrode 14. Note that the cathode electrode 11 and the heater 12 constitute an electron gun. The cathode electrode 11 and the heater 12 are connected to each other inside the electron tube 2. In FIG. 1, a connection point is indicated by a reference symbol HK.

[0030] The electron tube 2 is driven in a controlled manner by a control driving means composed of a low-voltage power supply 21, a high-voltage power supply 22, and a control unit 24. Further, the high-voltage power supply 22 includes a collector power supply 22a and a helix power supply 22b. Note that the power supply of the high-frequency circuit system 3 is also the power supply for the above-mentioned electron tube 2.

[0031] The low-voltage power supply 21 is connected to a heater terminal H and a heater terminal HK, and supplies electric current to the heater 12. Further, the heater terminal HK is also connected to the cathode electrode 11, and thus the heater terminal HK is hereinafter described as a shared terminal HK.

[0032] The low-voltage power supply 21 is a constant current power supply, and, when a heating signal G1 is received from the control unit 24, outputs an electric current of a numerical value set in advance. Hereinafter, an electric current to be outputted from the low-voltage power supply 21 is described as the low-voltage current Ih. The low-voltage current Ih flows through a circuit composed of the heater terminal H, the heater 12 and the shared terminal HK. Further, in the following description, an electric current which actually flows through the heater 12 is defined as the heater current If. This is because the low-voltage current Ih and the heater current If are not identical necessarily.

[0033] The collector power supply 22a included in the high-voltage power supply 22 is a power supply for drawing out electrons formed by the cathode electrode 11 to make the formed electrons be an electron beam. The helix power supply 22b is a power supply for accelerating thermally formed electrons to generate a microwave.

[0034] The collector power supply 22a is connected between the collector electrode 14 and the heater terminal H. The helix power supply 22b is connected between the helix electrode 13 and the heater terminal H.

[0035] By such connection relationship, electrons formed by the cathode electrode 11 are accelerated by the electric potential difference between the cathode electrode 11 and helix electrode 13, and are collected by the collector electrode 14. An electric current at that time is an electron beam, and also is the cathode current Ik.

[0036] That is, the cathode current Ik flows through a circuit composed of the heater terminal H, the heater 12, the cathode electrode 11, the collector electrode 14, the collector power supply 22a and the heater terminal H. Accordingly, the heater current If that flows through the heater 12 will be expressed as follows:

If=Ih+Ik(1)

[0037] In Formula 1, Ih is a low-voltage current and Ik is a cathode current. Then, although the low-voltage current Ih and the cathode current Ik flow through the heater 12 together, the current directions of these are reverse directions to each other. Accordingly, considering the current directions, Formula 1 can be written as follows:

If=IhIk(2)

This means that, when the cathode current Ik flows, the heater current If becomes smaller than the low-voltage current Ih.

[0038] Next, such control driving of electron tube 2 will be described. FIG. 2 is a diagram illustrating time changes of the low-voltage current Ih, the heater current If and the cathode current Ik, and (a) is a diagram indicating a case when Ik=0, (b) is a diagram when making the cathode current Ik flow, (c) is a diagram when adjusting the low-voltage current Ih, and (d) is a diagram illustrating the self-compensation operation of the heater current If.

[0039] First, the control unit 24 outputs the heating signal G1 that directs to apply the low-voltage current Ih to the low-voltage power supply 21 (Referring to FIG. 2(a)). In FIG. 2(a), Low voltage ON indicates the timing at which the low-voltage power supply 21 is driven and the heater 12 is begun to be energized. The heater current If will be the same numerical value as the low-voltage current Ih (If=Ih) because the low-voltage current Ih is supplied to the heater 12 and, in addition, an extraction signal G2 has not been outputted yet to the high-voltage power supply 22 at that time (Ik=0).

[0040] The heater 12 generates heat by the low-voltage current Ih, and the temperature of the cathode electrode 11 rises and thermal electrons are formed. Then, at the time when the cathode electrode 11 reaches a fixed temperature, the control unit 24 outputs the extraction signal G2 to the high-voltage power supply 22. In FIG. 2(b), High voltage ON indicates the operation timing of the high-voltage power supply 22. As a result, voltage is applied between the helix electrode 13 and the heater 12, and between the collector electrode 14 and the heater 12, and the cathode current Ik flows.

[0041] Alternately, it is possible to perform control in such a way that, when a time set in advance has passed after the control unit 24 has outputted the heating signal G1, it is assumed that the cathode electrode 11 has reached a fixed temperature. In this way, temperature monitoring of the cathode electrode 11 is unnecessary, and thus there is an advantage that the circuit configuration of the control unit 24 becomes simple.

[0042] Since the cathode current Ik and the low-voltage current Ih at that time are electric currents in opposite directions, the low-voltage current Ih is of a smaller value than the heater current If by the cathode current Ik (Referring to Formula 2). This means that the cathode current Ik functions as an operation margin to a rated current of the heater 12 because, even if the low-voltage power supply 21 is outputting the rated current, only a heater current smaller than the rated current by the cathode current Ik flows through the heater 12.

[0043] Although such operation margin can be used as an operation margin, there may be cases where it is not necessary to consider an operation margin so much since the low-voltage power supply 21 is a constant current power supply and the heater 12 is a current active element.

[0044] In such cases, it is also possible to increase the low-voltage current Ih (Referring to FIG. 2(c)). In FIG. 2(c), the low-voltage current Ih is increased by Ih (=Ik) corresponding to the operation margin at the timing of High voltage ON. Further, timing when the low-voltage current Ih is increased may be any time after the turning on of the high voltage.

[0045] It is supposed that, in a case where operation is continued in such state, an amount of the thermal electrons formed by the cathode electrode 11 is decreased due to deterioration of the characteristics of the cathode electrode 11. The dotted line K1 in FIG. 2(d) indicates decrease in the cathode current Ik due to deterioration of the heat electron emission characteristics. Here, let a deterioration amount of the cathode current Ik be Ik. At that time, the heater current If becomes as follows:

[00001]$\begin{array}{cc}\begin{array}{c}\mathrm{If}=.Math.\mathrm{Ih}-\left(\mathrm{Ik}-.Math..Math.\mathrm{Ik}\right)\\ =.Math.\mathrm{Ih}-\mathrm{Ik}+.Math..Math.\mathrm{Ik}\end{array}& \left(3\right)\end{array}$

[0046] In other words, when the emission amount of thermal electrons decreases due to characteristics deterioration of the cathode electrode 11, the heater current If increases by Ik and a heat generation amount by the heater 12 increases. As a result, the temperature of the cathode electrode 11 rises, and decrease in a heat electron emission amount is compensated autonomously.

[0047] As it has been described above, decrease in an electron beam amount due to deterioration of heat electron emission characteristics in a cathode electrode is compensated autonomously by making a low-voltage current and a cathode current which flow through a heater flow in opposite directions, and, therefore, a highly reliable electron gun and electron tube can be provided using a low-cost and simple structure.

[0048] As above, the present invention has been described taking the example embodiment mentioned above as an exemplary example. However, the present invention is not limited to the example embodiment mentioned above. In other words, various aspects which a person skilled in the art can understand can be applied to the present invention within the scope of the present invention.

[0049] This application is based upon and claims the benefit of priority from Japanese patent application No. 2015-186732, filed on Sep. 24, 2015, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

[0050] 2 Electron tube [0051] 3 High-frequency circuit system [0052] 11 Cathode electrode [0053] 12 Heater [0054] 13 Helix electrode [0055] 14 Collector electrode [0056] 21 Low-voltage power supply [0057] 22 High-voltage power supply [0058] 22a Collector power supply [0059] 22b Helix power supply [0060] 24 Control unit