Large signal analysis of the multicavity klystron

The techniques developed to study large signal effects in the two-cavity klystron have been extended to determine performance of the multicavity tube. Bunching is computed as a function of excitation phase and amplitude at various gaps, tunnel lengths, beam diameter and density. Results of efficiency calculations taking into account velocity distribution within the bunch are discussed.     

Design considerations for the high-power multicavity klystron

A confined-flow large-signal formulation of the klystron interaction equations is presented and applied to the analysis of the multicavity klystron amplifier. The effects of cavity voltage, cavity phase, drift length, and beam parameters are studied. The two- and three-cavity amplifiers are studied in detail, and several numerical examples of four-cavity klystrons are also given. A significant second-harmonic component of velocity modulation is shown to improve the dc to RF conversion efficiency. Two methods of obtaining this modulation are discussed. The large-signal theory presented here has been used to design a five-cavity klystron which is 50 percent efficient and has a controllable power transfer curve. Theoretical and experimental power transfer curves are presented for several 1 1/4-MW klystrons; the calculated output power is between 4 and 10 percent greater than the experimental values.     

Low-noise klystron amplifiers

The principles of low-noise guns have been applied to klystron amplifiers with good corroboration of the theory. In the past, many people thought that klystrons had inherently high noise figures, while others advanced the theory that low-noise guns might be used with klystrons as well as with wave tubes. The development to be described here shows that the former impression is not true and verifies that low-noise klystron amplifiers are possible. The most obvious difference between the guns for low-noise klystron amplifiers and those typical of low-noise traveling-wave tubes is the higher beam current which is required for adequate klystron gain. A byproduct of this higher current is a wide dynamic range. In addition to the development of the electrical parameters, a major effort went into klystron construction techniques somewhat peculiar to low-noise klystron amplifiers. The data taken show that alignment of the low-noise gun electrodes with the drift tube, alignment of the beam with the magnetic field, elimination of the collector's secondary electrons from the beam, and cleanliness of the tube are of primary importance in constructing a low-noise klystron amplifier. Several two-cavity, low-noise klystron amplifiers were built for operation in both S-band and C-band. The typical low-level gain was 11.5 db, and the saturated power output was 180 mw. Several tubes exhibited noise figures below 9 db; the lowest value obtained was 6.7. db.     

Three-dimensional evaluation of energy extraction in output cavities of klystron amplifiers

An accurate three-dimensional analysis of the performance of output gaps in klystron amplifiers was carried out. The parameters investigated were: beam radius, perveance, output gap angle, output gap peak voltage, RF phase, magnetic field, and beam interception. A new, accurate method for computing space-charge forces between axially and radially deformable rings was developed. Rigorous expressions for electric and magnetic fields in the tunnel and the gap were used. The highest computed efficiency for an optimally bunched beam was 80.3 percent with 6 percent "ideal" interception. An important conclusion is that efficiency decreases with increasing normalized tunned radiusbeta_{e}aforb/aconstant in the examined range0.4 and probably beyond. Excellent correlation in efficiency and interception between a model klystron developed by E. Lien of Varian and the authors' program was established.     

Optical klystron

A quantum effect in the interaction between a free electron beam and optical field has been considered. Velocity modulation on the electron beam is produced "classically" when the modulation-gap transit angle ωτ < 1.     

Millimeter-wave extended interaction klystron

The interaction of the HF fields in the distributed resonance system of a high-power millimeter-wave klystron with an electron beam is theoretically and experimentally studied under limitations imposed on the length of interaction space and moderate values of the beam perveance. A possibility of amplifying and generating extended interaction klystrons (EIKs) is demonstrated. The EIKs with the distributed extraction of energy exhibit relatively high efficiencies, output powers, and gains at an acceptable gain band. In the experimental prototypes of the four-cavity packaged EIK working in the mid-millimeter-wavelength range, the output pulse power is no less than 2.5–3 kW, the efficiency is 30%, the gain is 25–30 dB, and the gain band at a level of 3 dB is 0.25–0.35% at an anode voltage of 18 kV and a beam current of 0.5 A.     

Electric field measurements in klystron cavities

A qualitative comparison is made between computed and measured electric fields in typical TM010klystron cavities. The computer code LALA is shown to apply effectively to cavities with offset gaps which are difficult to solve analytically, and a bead-pull technique using a highly directive perturbing needle is utilized to verify the theoretical results. The magnitude of the radial field components is discussed as well as the shape of the axial field resulting from shaping the drift tube noses and offsetting the gap.     

Nonlinearities in stereoscopic phase-differencing

Exploiting the quasi-linear relationship between local phase and disparity, phase-differencing registration algorithms provide a fast, powerful means for disparity estimation. Unfortunately, these phase-differencing techniques suffer a significant impediment: phase nonlinearities. In regions of phase nonlinearity, the signals under consideration possess properties that invalidate the use of phase for disparity estimation. This paper uses the amenable properties of Gaussian white noise images to analytically quantify these properties. The improved understanding gained from this analysis enables us to better understand current methodologies for detecting regions of phase instability. Most importantly, we introduce a new, more effective means for identifying these regions based on the second derivative of phase.     

Nonlinearities of GaAlAs lasers--Harmonic distortion

Narrow stripe lasers (2-6 mum) and transverse junction lasers exhibit excellent linearity. The dependence of relative second-and third-harmonic distortion is investigated as a function of modulation frequency and modulation current. Relative second- and third-harmonic distortion of -50 and -70 dB is observed for an optical signal of 4 mW p-p (f_{m} = 60MHz). Intermodulation products are compared with the harmonic distortion and good agreement is obtained between the two quantities when the relations for a simple nonlinearity without memory are used. The measured distortion is in agreement with distortion calculated from rate equations.     

Instrumentation amplifiers using operational transconductance amplifiers

Instrumentation amplifier circuits using operational transconductance amplifiers (OTAs) as active circuit elements are proposed in this paper. Two new instrumentation amplifier circuits have been described and experimentally verified, where the first circuit comprises four OTAs and five resistors and the second circuit comprises two OTAs and three resistors.     

Experimental analysis of biased gap klystron

A commercially available multicavity klystron rated at 45 percent efficiency and equipped with external cavities was modified so that a dc potential could be applied across the interaction gaps. When the tube was carefully tuned, an efficiency of 60 percent was obtained; when an accelerating bias was applied across the penultimate gap of the tube, efficiencies of 66 percent were recorded without collector depression, and of over 70 percent with collector depression. In addition, applying bias to the tube made possible efficiencies in excess of 60 percent for a five to one range of power levels (for different cathode voltages). Furthermore, it was possible to apply bias to the tube in such a way that, for a constant drive level, the power output remained constant, the efficiency remained constant at over 50 percent, but the phase could be varied through more than 180°.     

一种C波段宽带速调管发射机的设计

介绍了一种C波段宽带速调管发射机的设计,叙述了发射机的组成形式并给出其主要性能指标,重点介绍宽带速调管、回扫电源技术、固态调制器,解决了等激励条件下速调管输出功率起伏较大及散热问题。     

AlGaAs/GaAs visible ridge waveguide laser with multicavity structure

Ridge waveguide lasers of two different cavity configurations are described. First is the multisection ridge laser structure in which the longitudinal mode selection due to the coupled-cavity effect was observed and single-frequency operation was achieved. In this structure, stable single-transverse-mode operation was ensured by the central 5 μm wide section, and the beam waist and power output were enlarged by the outer 10 μm wide sections. Output power of more than 13 mW under pulsed excitation was obtained. The second configuration is the shallow groove ridge laser in which the 5 μm wide shallow groove terminates slightly above the active region and provides an index perturbation that contributes to mode selection. All the lasers are designed to emil in the visible range between 7600 and 7900 Å. The shortest observed wavelength is 7570 Å, and can be seen by the naked eye.     

Some studies on a high-perveance hollow-beam klystron

The performance of an experimental high-perveance hollow-beam klystron has been investigated. Data of small- and large-signal operation are presented in this paper. For strong magnetic confinement of the beam, it is shown that gap interaction and gain and large-signal bunching are well predictable by the appropriate theories. A sensitivity of all measurable RF-quantities to the level of the focusing field has been studied. Efficiencies are lower than predicted from the measured high degree of bunching, and reflect the effect of potential depression.     

A stagger-tuned five-cavity klystron with distributed interaction

This paper describes the operation of a five-cavity klystron with distributed interaction using stagger-tuned cavities. A bandwidth of 64 Mc with a gain of about 30 db at 40 per cent efficiency is typical of the performance of the amplifier.