JP2001035399A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a spurious level to a low level by setting an electric field minimum point of a filter to a position separated by a specific distance decided to a guide wavelength of the fundamental frequency from an electric field minimum point in the output waveguide of a magnetron. SOLUTION: λg is set as an in-guide wavelength of a fundamental frequency, N is set as a natural number, and the electric field minimum point of a filter is placed at a position separated by λg/4+N×λg/2±λg/10 from an electric field minimum point of an output waveguide of a magnetron. A magnetron oscillating part 11 is jointed to the output waveguide 13 through an output part 12, and microwaves generated in the oscillating part 11 is outputted to the waveguide 13 through the output part 12 to proceed to a radar antenna. In the relationship between a phase distance and a damping quantity of a corrugated filter 14, fundamental wave output is stabilized at a distance becoming almost λg/4+N.λg/2 in an electrical distance between an electric field minumum point of a magnetron output part and an electric field minimum point of the corrugated filter 14 and in a range of almost ±λg/10 in front back of the distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron for a radar, and more particularly to a structure of an output section.

[0002]

2. Description of the Related Art FIG. 6 is a plan view of an anode portion of a conventional magnetron for a radar device. A cathode 1 is surrounded by a cylindrical anode 2 and is separated by a vane 3. Since a magnetron having such a multi-polarized structure has several resonance spaces, generating spurs other than the fundamental wave in accordance with the state of operation of the magnetron is, in principle, an event with a sufficiently high possibility. Has become.

[0003] The spurious level is strictly regulated by the Radio Law. Radar equipment is required to have an oscillation output of -40 dBc or less with respect to the fundamental wave oscillation output. It is a situation that it is difficult to hold down.

[0004]

In recent years, the regulation of the level of spurious radiation from a radar device has become more stringent. In the above-mentioned conventional magnetron, other characteristics are sufficiently satisfied, but spurious is always required. It is difficult to keep within regulation values. Also, it was very difficult to control spurs with a higher margin.

On the other hand, when a filter is mounted between the magnetron and the output antenna for use, the resonance of the filter and the resonance of the magnetron interfere with each other, and abnormal oscillation of the magnetron and the original attenuation characteristics of the filter are obtained. Not often situations occur. Therefore, it is necessary to insert an element such as a circulator or an isolator between the two for the purpose of removing interference between the two, and there has been a problem in terms of cost and space efficiency.

In view of such a situation, an object of the present invention is to solve the above-mentioned problems and to manufacture a magnetron having a small spurious level.

[0007]

In order to achieve the above object, the present invention relates to a magnetron having a filter at an output section, wherein λg is a guide frequency of a fundamental frequency, and N is a position of the filter and the magnetron output section. When a natural number is used, the minimum point of the electric field of the filter is λg / 4 + N × from the minimum point of the electric field in the output waveguide of the magnetron.
It is characterized by being placed at a distance of λg / 2 ± λg / 10.

Further, in the magnetron having the above configuration,
A stub is provided between the filter and the magnetron output section so as to be able to change the amount of insertion into the output waveguide.

[0009]

FIG. 1 shows an embodiment of the present invention.
Reference numeral 11 denotes a magnetron oscillation unit, which is coupled to the waveguide 13 through an output unit 12. Therefore, the microwave generated by the oscillating unit 11 is transmitted through the output unit 12 to the waveguide 1.
It is output to 3 and heads for the radar antenna. Reference numeral 14 denotes a corrugated filter, whose frequency characteristics are shown in FIG.
Looking at the characteristics according to this embodiment, the attenuation at the frequency of the fundamental wave (at the oscillation frequency of the magnetron) is 0.2 dB.
The amount of attenuation at the frequency of the π-1 mode, which usually occurs as spurious, is 33 dB.

Initially, when the spurious level of the magnetron alone is -45 dBc with respect to the fundamental wave,
If the attenuation of 33 dB considered as the maximum value of the attenuation of the corrugated filter can be achieved, the spurious should be able to be suppressed to -78 dBc or less with respect to the fundamental wave. If it is attached to an arbitrary position (electrical position) with respect to the output unit, not only the effect of 33 dB cannot be obtained, but also the fundamental oscillation is affected depending on the attachment position, and the output power is reduced. This may lead to a decrease or deterioration of the fundamental oscillation spectrum.

FIG. 3 shows the relationship between the phase distance of the corrugated filter and the amount of attenuation. The horizontal axis represents the phase distance (electrical length) of the corrugated filter to the output waveguide, and the vertical axis represents the output power and spurious of the fundamental wave. It is a graph showing the amount of attenuation. The phase distance on the horizontal axis is the electrical distance between the minimum point of the electric field of the magnetron output unit and the minimum point of the electric field of the corrugated filter. This distance is approximately λg / 4 + N · λg / 2 and before and after the distance. In the range of approximately ± λg / 10, the fundamental wave output power is stable and the spurious attenuation amount is the maximum. Outside this range, the fundamental wave output power sharply decreases and the spurious attenuation amount is reduced. Is getting smaller. That is, the minimum point of the electric field of the filter is set to be approximately λg / 4 + N ·
It can be seen that the effect of the filter can be maximized by placing it at a distance of λg / 2 ± λg / 10 (where λg is the guide wavelength of the fundamental wave and N is a natural number). From this graph, the distance between the minimum point of the electric field of the output unit and the minimum point of the electric field of the filter is approximately λg / 4 + N · λg / 2 ±
It is understood that the effect of the filter can be maximized by separating λg / 10. (Here, λg is the guide wavelength of the fundamental wave, and N is a natural number.)

Next, FIG. 4 shows an embodiment in which a stub 45 capable of changing the insertion amount is attached between the antenna output section 42 and the corrugated filter 44. It is known that the output phase of the magnetron usually has a variation of about ± 35 degrees.

Since the phase distance may slightly deviate due to this variation, a stub for adjustment is arranged between them. By this fine adjustment, the effect of the filter is maximized.

FIG. 5 is an output spectrum of the magnetron according to the present embodiment. By utilizing the present invention,
With respect to the fundamental wave, it is possible to suppress spurious to a very small value of -78 dBc.

As described above, according to the present invention, the spurious emission level of the magnetron can be stably suppressed at a low level, so that the spurious level of the entire radar apparatus can be further reduced as compared with the prior art. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an attenuation characteristic of a corrugated filter.

FIG. 3 is a diagram showing the relationship between the phase distance and the amount of attenuation of a corrugated filter.

FIG. 4 is a view showing an embodiment in which a stub is attached.

FIG. 5 is a diagram showing an output spectrum of the magnetron of the present invention.

FIG. 6 is a diagram showing the internal structure of a conventional magnetron.

[Explanation of symbols]

1: Cathode, 2: Anode, 3: Vane 11: Oscillator, 12: Output, 13: Output waveguide, 14: Corrugated filter, 42: Output, 43: Output waveguide, 4
4: Corrugated filter, 45: stub,

Claims (2)

[Claims] In a magnetron having a filter at an output part, when λg is a guide wavelength of a fundamental frequency and N is a natural number, the minimum point of the electric field of the filter is determined by the position of the filter and the magnetron output part. From the electric field minimum point in the output waveguide, λg / 4 + N ×
A magnetron characterized by being placed at a distance of λg / 2 ± λg / 10. 2. The magnetron according to claim 1, further comprising a stub provided between the filter and the magnetron output section so that the insertion amount into the output waveguide can be changed.