DE1085617B - Tunable reverse shaft generator tubes - Google Patents

Description

GERMAN

The invention relates to a tunable reverse wave generator tube, in which the electron beam is guided along a delay line which is inhomogeneous perpendicular to the beam direction, in particular along a double comb line with interlocking links (interdigital line), and the electron beam has a small lateral extent compared to the width of the delay line owns.

When building reverse wave generators, one strives for delay lines that allow it without Too large changes in the DC operating voltages to tune through wide frequency ranges. Furthermore are for the generation of very short waves in the cm and mm range desired delay lines, their Dimensions are not too small.

In practice, so-called double comb lines with interlocking links are often used (Interdigital lines), on which an electron beam, usually a flat beam, on one or both sides, is passed. The generation and guidance of such a flat jet is in many cases Can only be realized with great effort and difficult to realize.

The present invention is based on the object to create a reverse wave generator tube that is tunable over a wide frequency range is and is characterized by a relatively simple structure. The invention uses to solve this problem, a delay line which is inhomogeneous perpendicular to the beam direction, in particular a double comb line with interlocking links (interdigital line). Such lines are known per se. It is also the case with reverse wave generator tubes equipped with such delay lines already known to guide the electron beam so that it is only in the area of the central plane of the delay line with this is coupled, so the electron beam is small compared to the width of the delay line has lateral expansion. Such a reverse wave generator tube can only be found in the fundamentals (room harmonic fundamental wave) excite. Even when using an electron beam that covers the entire If the width of the delay line is covered, the tube can only be excited in the fundamental. Tuning - by changing the beam voltage ■ - · is only possible in a limited frequency range possible. In contrast, there is a tunable reverse wave generator tube in which the electron beam is guided along a delay line which is inhomogeneous perpendicular to the beam direction is, especially along a double comb line with interlocking links (Interdigi tunable Reverse wave generator tube

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Witteisbacherplatz 2

Dr. rer. nat. Werner Veith, Munich,
has been named as the inventor

valley line), and the electron beam is small compared to the width of the delay line has lateral expansion, characterized according to the invention that for tuning in a wide frequency range the delay line and the position of the electron beam can be shifted laterally to one another.

The findings on which the invention is based are explained below with reference to the figures and the essential concept of the invention is described in more detail.

In Fig. 1, a double comb line consisting of the two parts 1 and 2 with interlocking members is shown schematically. An electron beam was guided on one side of this line and the instantaneous values of the high-frequency field strength in the direction of the electron beam in areas I to VII were determined. The course of the high-frequency field strength in the individual areas is shown in FIGS. 2a to 2c for different frequencies with which the line was excited. In these figures, an instantaneous image of the instantaneous value eleven of the high-frequency field strength over a certain distance L is plotted for each of the areas I to VII.

In FIG. 2 a, the line wavelength (X ₁ ) of the frequency f _v with which the line was excited is selected to be greater than twice the width b (FIG. 1) of the delay line. It can be seen that in region IV, which also contains the central axis of the line, there is a sinusoidal profile of the instantaneous values of the high-frequency field strength. The wavelength of this sinusoid is equal to the line wavelength X _{1 of} the fed-in frequency f _± (fundamental frequency). If one looks at the other areas, one recognizes that the further one moves away from the central area IV.

009 567/263

far, the sinusoidal field strength distribution superimposed more and more harmonics (frequency harmonics) are, so that finally in the outer areas I and VII the fundamental frequency is no longer clearly recognizable is.

If one uses the same delay line, and decreasing the wavelength at which the conduit is excited in advance, to the half (line wavelength?. ₂ = λ _1/2), so obtained in the areas I to VII 2b shown the in the Fig. Course of the instantaneous values of the high-frequency field strength. The field strength distribution with a sinusoidal profile now occurs in areas II and VI, the wavelength of the sinusoid being equal to the line wavelength A _{2 of} the frequency fed in / ₂ = 2 Z ₁ . In the other areas, in turn, harmonics (frequency harmonics) of this frequency are superimposed.

If the wavelength is shortened to a third (line wavelength A ₃ = Zl ₁ ZS), the field strength curve shown in FIG. 2 c is obtained. The sinusoidal curve now occurs again in the area of the central axis (area IV). However, this is also available in areas II 'and VI'. For the sake of clarity, the field strength curve is not shown in area ΙΓ; it corresponds to the field strength curve in area VI '.

Note that both the sine wave shown in Fig. 2a and those shown in the other figures shorter sine waves have the same phase velocity, it is easy to see that in a backward wave generator tube with this delay line only the frequency is excited, in which the field strength values (instantaneous values) interact with the electron beam Fields are largest. If you use a flat jet, only the basic frequency will be excited. (In principle, the amplitudes of the waves on the delay line are the same, but since they are perpendicular to the delay line the field strength of the shorter waves decays faster, because of the electron beam always a certain distance from the delay line, always excites the fundamental frequency.)

From Fig. 2a it can be seen that only those parts of the high-frequency field lying in the region of the central axis of the delay line contribute significantly to the excitation of the fundamental frequency ^ ₁ . It is therefore sufficient if, in a known manner, to excite the fundamental frequency, a high-current electron beam with a diameter that is smaller than the dimensions of the wave-guiding arrangement passes the wave-guiding arrangement only in this area of the wave-guiding arrangement. Essentially the same effect is then obtained as with a flat beam and also has the advantage of being able to use an electron beam that is easier to produce and guide. The shape of the electron beam can be of any shape, although a round beam or a beam with a rectangular cross-section is predominantly used. The arrangement operated in this way can be tuned in a manner which is also known per se by changing the operating DC voltages over a limited frequency range. The teaching according to the invention now offers the advantage of considerably expanding this tunable wave range in the area of shorter waves. To do this, the electron beam only needs to be guided along an area in which the amplitude ^{J of} the field strength of the desired frequency is greater than for other frequencies. Applied to the example of Fig. 2b, this means that the electron beam to excite the reverse wave generator tube with half the wavelength either along area II or VI, because in these areas, the amplitude of the high-frequency field strength is greater _{for this frequency / 2 than for} other frequencies. In the case of the example in FIG. 2c, the electron beam would have to be guided in one of the areas II 'or VI' (In area IV, the fundamental frequency Z _{1 would be} excited in accordance with the explanations given above, since its field decays less quickly perpendicular to the delay line.) In order to set the various frequencies, it is particularly advantageous if the position of the wave-guiding arrangement and the electron beam can be displaced relative to one another by electron-optical or mechanical means. A reverse wave generator tube is then obtained, which can be tuned in an overall much larger frequency range than a z. B. backward wave generator tube operated with a flat jet. The limited electronic tuning of the additional frequency bands (through additional changes in the DC operating voltages) has the advantage that, since the frequencies are relatively little dependent on the DC operating voltages, a high level of frequency stability is achieved.

The invention is not limited to the double comb line selected as an exemplary embodiment with interlocking links, but can be applied to any wave-guiding arrangement (delay line) applied, which is inhomogeneous perpendicular to the beam direction.

Claims (2)

Patent claims: 1. Tunable reverse wave generator tube in which the electron beam is along a Delay line is performed, which is inhomogeneous perpendicular to the beam direction, in particular along a double comb line with interlocking links (interdigital line), and the Electron beam has a small lateral extent compared to the width of the delay line possesses, characterized in that the tuning in a wide frequency range Delay line and the electron beam are laterally displaceable in their position to one another. 2. Tunable reverse wave generator tube according to claim 1 ,. characterized, that the lateral displacement is carried out by electron-optical or mechanical means. Considered publications:
German Patent No. 903 726;
British Patent No. 699 893. For this purpose 2 sheets of drawings ®, 009 567/263 7.60