# Analysis of Fast Wave Couplers for Transverse Field Beam Type Parametric Amplifiers

01 Feb 1961-International Journal of Electronics (Taylor & Francis Group)-Vol. 10, Iss: 2, pp 147-151

TL;DR: In this paper, a traveling-wave coupler for fast wave excitation only of a transverse field parameter beam amplifier is analyzed, and it is shown that a dip condition can be achieved, insuring almost complete transfer of the fast wave beam noise to the circuit and of the circuit signal power to the fast beam wave.

Abstract: A traveling-wave coupler for fast wave excitation only of a transverse field parameter beam amplifier is analyzed. The analysis indicates that, as expected, "a dip condition" for a transverse field tube can be achieved, insuring almost complete transfer of the fast wave beam noise to the circuit and of the circuit signal power to the fast beam wave. This requires that the slow and fast beam waves be sufficiently separated in velocity (i.e., the cyclotron frequency be high enough), that the circuit wave be in close synchronism with the fast beam wave, and that the coupling between the circuit and the beam be loose. (auth)

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01 Jan 1982

TL;DR: The down-converter with resistive image-termination allows for low-noise conversion gain with positive input and output resistance, if the frequency ratio fin/fout is in the order of the diode dynamic quality factor q = | γs | Q(fin) these merits being lost for conversion ratios which are either a little above unity or very much in excess of q as mentioned in this paper.

Abstract: The preceding discussion has revealed some principal handicaps of single varactor diode circuits; they are, for example, that:
With the amplifier gain can be achieved solely in the frequency-inverting mode of operation with the drawback of negative input resistance. Positive input resistance (and hence the chance of power matching) requires a circulator (Sect.7.3.2). The condition of minimum noise temperature implies a pump frequency which is much higher than the signal frequency (7.34).
The down-converter with resistive image-termination allows for low-noise conversion gain with positive input and output resistance, if the frequency ratio fin/fout, is in the order of the diode dynamic quality factor q = | γs | Q(fin) these merits being lost for conversion ratios which are either a little above unity or very much in excess of q.

##### References

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TL;DR: In this paper, the power output of a traveling-wave tube has been analyzed using a linearized theory only, and no attempt has been made to develop a non-linear theory.

Abstract: A Theoretical Evaluation of the power output of a traveling-wave tube requires a theory of the non-linear behavior of the tube. In this book we have dealt with a linearized theory only. No attempt will be made to develop a non-linear theory. Some results of non-linear theory will be quoted, and some conclusions drawn from experimental work will be presented.

546 citations

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TL;DR: In this paper, the authors derived an expression for the noise figure of a transverse field amplifier with a collimator and showed that the use of such an amplifier is required to give low noise figures.

Abstract: From theoretical considerations of the fluctuations in an electron beam, an expression for the noise figure of a transverse‐field amplifier is derived. There are found to be three statistically uncorrelated sources of noise in the beam of such a tube—(1) that arising from the fluctuations in the transverse emission velocity of electrons in a direction normal to the surface of the beam, (2) that arising from fluctuations in the transverse emission velocity of electrons in a direction parallel to the surface of the beam, and (3) that arising from fluctuations in the mean position of the beam and depending on its thickness. The analysis shows that the use of a collimator is required to give low noise figures. This is illustrated by the following example: for a tube designed to operate at 1000 mc with a collimator whose width is 0.004 in., the theoretical noise figure is 2 db. Without the collimator, the noise figure would be 11 db.

10 citations

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TL;DR: In this article, the principle of varying a circuit reactance to produce gain is applied to an electron beam, where the beam is modulated by an r.f. wave at frequency ω and this supplies energy to a signal at frequency ε and an idler at frequency ǫ which is generated in the beam.

Abstract: The principle of varying a circuit reactance to produce gain is applied to an electron beam. The beam is modulated by an r.f. wave at frequency ω and this supplies energy to a signal at frequency ω1 and an idler at frequency ω2 which is generated in the beam, where ω = ω1 ± ω2 is found that when ω1 + ω2 the signal idler grows exponentially while if ω1 − ω2 power is continuously converted from ω1 to ω2 and back to ω1. For finite size beams, a current modulation threshold must be exceeded to produce growing waves. For the zero thickness beam no such threshold is observed. The growing waves are found to be fast space charge waves for a range of values of the signal to idler frequency ratio in contrast with conventional amplifiers which amplify slow waves and it is the latter class to which minimum noise figure theorems apply. Tho Manloy—Rowe relations are verified for the parametric beam and the gain per unit length is found analytically. Finally, boundary conditions are applied. It is found that wh...

10 citations

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Bell Labs

^{1}TL;DR: The theory and design for fast wave helix couplers for use with longitudinal beam parametric amplifiers are given in this paper, and a matrix formulation of these equations is used to point out a formal mathematical analogue of the Schrodinger equation of quantum mechanics.

Abstract: The theory and design for fast wave helix couplers for use with longitudinal beam parametric amplifiers are given. The TWT equations are put in coupled mode form. A matrix formulation of these equations is used to point out a formal mathematical analogue of the Schrodinger equation of quantum mechanics. This analogue is used to suggest possible techniques of solution and may lead to hitherto unexplored methods of treating this problem. Two special eases are treated. The formulation is equivalent to that used by Haus and Robinson (1954). The design procedure for fast wave couplers is given in detail in a separate section. The coupler consists of a Kompfner dip helix preceded and followed by a velocity jump. By this technique it is shown that a fast space-charge wave can be excited on the beam. The fast mode noise can be completely removed from the beam by the same coupler. The slow mode goes through completely unaffected in amplitude. Since the slow mode is not amplified, noise from the slow mode ...

9 citations

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