JPH1074459A - Cathode structure for electromagnetic field orthogonal amplifier tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic field orthogonal amplifier tube CFA with little spurious noise or noise near operating frequency by suppressing excessive electrons in a part where crowded electrons are most vigorously collided to a cathode. SOLUTION: Since excessive electrons in a part where crowded electrons are most vigorously collided to a cathode 1 can be suppressed, a noise separated from the operating frequency by an integer times of the frequency of the electron circulating the cathode can be suppressed by, for example, about 10dB-30dB. The surface treatment of the cathode 1 can be performed by other methods, for example, by sputtering and adhering a metal having a large work function and a small secondary electron emitting coefficient. In an electromagnetic orthogonal amplifier tube CFA using a platinum cathode, a method of partially sputtering a metal can be also adapted. Thus, excessive electrons in a part where the crowded electrons are most vigorously collided to the cathode can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode structure of an electromagnetic field quadrature amplifier tube (hereinafter abbreviated as "CFA") with reduced spurious output.

[0002]

2. Description of the Related Art Conventionally, the cathode of CFA has been known as Thoria (Th
O2) and platinum (Pt) are used, and the shape is usually cylindrical like a magnetron. The emission characteristics of the cathode are uniform over the entire area. In the emission, first, ions excited by the RF input strike the cathode surface, and then secondary electrons are emitted to instantly build up to a desired emission amount.
Then, the electrons are bunched by the interaction of the RF electric field, the magnetic field, and the DC electric field, and the potential energy possessed is given to the microwave circuit, so that the output has a large power. Some of the electrons that have energized the microwave circuit hit the anode and some hit the cathode. The microwave is amplified while repeating such a cycle.

[0003]

In the above-described structure having a uniform cathode over the entire circumference of the cathode, excessive electrons are generated when a part of the electrons gathered at the output portion collides violently with the cathode. However, this causes a problem that it becomes a noise source in the vicinity of the operating frequency, and under some conditions, excessive electrons feed back and oscillate.

[0004]

SUMMARY OF THE INVENTION In the present invention, the surface of the cathode is treated so as to reduce the emission of the cathode portion where the bunched electrons collide, particularly the cathode around the separator. The configuration is such that no excessive electrons are generated.

[0005]

FIG. 1 shows the basic structure of a CFA. 1 is a tria cathode, 2 is a slow wave circuit, and 10 is a group of electrons. FIG. 2 is an enlarged view of the cathode part, and the part a was polished with paper to reduce the emission capacity. Therefore, it is possible to suppress the excessive electrons in a portion where the collected electrons collide with the cathode most intensely. As a result, noise separated from the operating frequency by an integral multiple of the frequency at which electrons circulate around the cathode could be suppressed by about 10 dB to 30 dB. The surface treatment of the cathode can be performed by another method, for example, a method of attaching a metal having a large work function and a small secondary electron emission coefficient by sputtering. In addition, C using a platinum (Pt) cathode
In the case of FA, a method in which metal is partially sputtered can be adopted. As for the range for processing the cathode, if the portion a in FIG. 2 is set too large, the UMB (maximum operating current value) decreases. On the other hand, if the amount is too small, the noise suppressing effect is small. In the present embodiment, a range of about 30 ° to 60 ° in angle with the separator 8 on the output side is appropriate.

[0006]

As described above, according to the present invention, it is possible to obtain a CFA with less spurious and noise near the operating frequency.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of one embodiment of a CFA of the present invention.

FIG. 2 is an enlarged view of a cathode section of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cathode 2 ... Slow-wave circuit 3 ... Input waveguide 4 ... Input window 5 ... Input transition 6 ... Separator 7 ... Output transition 8 ... Output waveguide 9 ... Output window 10 ... … Electronic

Claims (2)

[Claims] 1. An electron emitted from a cylindrical cathode draws a cycloidal trajectory along a surface of an anode constituting a slow-wave circuit by a magnetic field orthogonal to an electric field, and the velocity is increased by a high-frequency electric field generated in a division gap of the anode. In the cathode structure of an electromagnetic field quadrature amplifier tube that receives modulation and amplifies microwave power input from an input window coupled to the slow wave circuit and outputs from a window coupled to the slow wave circuit, A cathode structure of an electromagnetic field quadrature amplifier tube, wherein a material having a work function larger than that of the cathode material and having a small secondary electron emission coefficient is adhered to a part (in the range of an output side angle of 30 ° to 60 °). 2. The cathode structure of an electromagnetic field orthogonal amplification tube, wherein a part of the cathode is mechanically polished to increase the work function of the part.