JPH0568820B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a traveling wave tube having a helical slow-wave circuit, and particularly to the configuration of a crossed helical slow-wave circuit consisting of two spirals. .

[Conventional technology]

In recent years, there has been an increasing demand for traveling wave tubes as power amplifier tubes at the final stage of repeaters for satellite communication earth stations, and high output is essential for such applications. As the output increases, the operating voltage and current will naturally become higher and larger, but due to the need to ensure insulation of the electrode tube, appropriate heat dissipation means, and ensure the required beam power, the external shape and dimensions will naturally change. increase However, on the other hand, user needs are toward small, lightweight, easy-to-handle, and low-power consumption devices, including those for mobile use such as on-vehicle and aircraft-mounted devices. Therefore, it has become essential to increase the output of the traveling wave tube without increasing its external dimensions and power consumption, that is, to find some means to increase its efficiency.

Conventionally, the slow wave circuit of a traveling wave tube has generally been a spiral slow wave circuit formed by spirally molding molybdenum or dungsten wire or tape, which have a high melting point. Various highly efficient measures have already been taken. Examples include slow-wave circuits that have a velocity taper pitch added to the output end of the helix to accommodate the slowdown of electrons, and slow-wave circuits that have gold plating on the helix to reduce high-frequency loss at the output end of the helix. be. However, in order to achieve even higher output, it is necessary to create a helical structure that suppresses the power component of the spatial harmonics of the helix, increases the coupling impedance of the fundamental wave, and at the same time reduces the backward wave component.

As one method, a so-called crossed helical slow wave circuit is known, in which a first helix that propagates electromagnetic waves and a second helix that intersects this helix at the same pitch are combined and combined. In this crossed helical slow-wave circuit, the propagation modes of the two helices exist superimposed, and the fundamental wave component electric field in the axial direction becomes stronger in the helical system as a whole, so the helical coupling It is known that impedance becomes higher and therefore higher output can be obtained. However, such a crossed helical slow wave circuit is difficult to form and has almost never been put to practical use.

To explain the crossed helical slow wave circuit in detail, FIG. is the first to propagate electromagnetic waves.
It has a shape that is a composite of two helices: a second helix 2' that intersects this helix 2' and has a reverse winding and the same pitch. On the outer periphery of the intersecting helix 2, a plurality of dielectric A body support 3 is provided, and these spirals 2 and a plurality of dielectric supports 3 are
It is housed in a cylindrical metal envelope 4 and fastened and fixed using an appropriate method. As mentioned above, the shape of the crossed helix 2 is a complicated cage-shaped cylindrical shape formed by combining two helices 2' and 2'' so as to intersect with each other at the same pitch.

[Problem that the invention seeks to solve]

In such a crossed spiral slow-wave circuit structure 1, it is difficult to form the crossed spiral 2, and it is almost impossible to put it to practical use.

For example, even if it is possible to form such a crossed helix using means such as electric discharge machining, it requires high processing accuracy and complex shape processing, resulting in high costs due to low quality products and long construction time, making it difficult to put it to practical use. It's impossible.

[Means for solving problems]

The present invention improves the configuration of the above-mentioned crossed helical slow-wave circuit to a practical form, and also molds a crossed helical slow-wave circuit in which the effect of the crossed helix is improved. The aim is to provide a highly efficient traveling wave tube.

That is, the crossed helical slow-wave circuit used in the traveling wave tube according to the present invention has a first helix that propagates electromagnetic waves, and a second helix overlapping the outer periphery of the first helix that propagates electromagnetic waves. The pitch is larger than the first spiral winding pitch, and the circuit lengths are made equal to each other.

Next, details of the present invention will be explained with reference to the drawings. FIG. 1 shows a three-dimensional diagram of a slow-wave circuit structure of a traveling wave tube according to the present invention. is housed in a cylindrical metal envelope 4. The crossed helix 2 is formed by overlapping a first helix 5 that propagates electromagnetic waves and a second helix 6 in the opposite direction so as to intersect with the first helix 5 on the outer periphery of the first helix 5. Furthermore, the pitch _P2 of the second helix 6 is the pitch of the first helix 5.
It is designed to be larger than P ₁ , and the circuit length (unfolded length) of the first helix 5 when the second helix 6 is wound on the first helix 5 at the same pitch is
l ₁ and the circuit length (developed length) of the second helix 6 is l ₂ , the pitch P ₂ of the second helix 6 is wound so that P ₂ =l ₂ /l ₁ P ₁ .

〔Effect of the invention〕

As explained above, in the traveling wave tube according to the present invention, a crossed spiral slow wave circuit structure can be realized very easily and at low cost, and the phase shift between the two spirals can be corrected, and the crossed spiral slow wave structure can be realized very easily and at low cost. Since it is molded without reducing its effectiveness, it is possible to provide a traveling wave tube that is smaller, lighter, and more efficient. This means that if the first helix 5 and the second helix 6 forming the crossed helix 2 have the same pitch because the second helix 6 is wound over the first helix 5, The circuit lengths of the two helices 5 and 6 are not equal. That is, since the second helix 6 has a larger winding diameter than the first helix 5, the circuit length becomes longer, and a phase difference occurs in the effective propagation mode of the electromagnetic waves. This phase shift weakens the fundamental wave component electric field in the axial direction of the slow wave circuit 1 and leads to a decrease in coupling impedance, resulting in a decrease in output and a reduction in the cross-helix effect.

Therefore, as described above, the crossed helix 2 is formed by winding the second helix 6 with a larger pitch so that the circuit lengths of the first helix 5 and the second helix 6 are equal.

[Brief explanation of the drawing]

FIG. 1 shows a three-dimensional view of a slow-wave circuit structure of a traveling-wave tube according to an embodiment of the present invention, and FIG. 2 shows a three-dimensional view of a conventional slow-wave circuit structure of a traveling-wave tube. 1...Slow wave circuit structure, 2...Cross helix, 2',
2″, 5, 6... Helix, 3... Dielectric support, 4
...A cylindrical metal envelope.

Claims (1)

[Claims] 1. In a traveling wave tube having a crossed helical slow wave circuit formed by two intersecting helices that propagate electromagnetic waves, the helix that propagates the electromagnetic waves is wound at a predetermined pitch on top of the first helix. A second helix is wound in a direction opposite to that of the first helix, and the pitch of the second helix is adjusted so that the circuit length of the first helix is equal to the circuit length of the second helix. A traveling wave tube that has a slow wave circuit that is wound larger than the pitch of the first spiral.