Radial Transmission Line Research Articles

Analytic Evaluaiion of the LAMPF II Booster Cavity Design

Through the past few decades, a great deal of sophistication has evolved in the numeric codes used to evaluate electromagnetically resonant structures. The numeric methods are extremely precise, even for complicated geometries, whereas analytic methods require a simple uniform geometry and a simple, known mode configuration if the same precision is to be obtained. The code SUPERFISH, which is near the present state of the art of numeric methods, does have the following limitations: No circumferential geometry variations are permissible; there are no provisions for magnetic or dielectric losses; and finally, it is impractical (because of the complexity of the code) to modify it to extract particular bits of data one might want that are not provided by the code as written. This paper describes how SUPERFISH was used as an aid in derivating an analytic model of the LAMPF II Booster Cavity. Once a satisfactory model was derived, simple FORTRAN codes were generated to provide whatever data was required. The analytic model is made up of TEM- and radial-mode transmission-line sections, as well as lumped elements where appropriate. Radial transmission-line equations, which include losses, were not found in any literature, and the extension of the lossless equations1 to include magnetic and dielectric losses are included in this paper.

Resonance in Long Distance Radial Transmission Lines with Static Var Compensation Part I-Frequencies and Mode Shapes

As subsynchhronous resonance and torsional interactions are dangers to be avoided at all costs, it would be reassuring if the resonance frequencies of static VAR compensated transnission lines are all supersynchronous. But are they? Part I provides the groundlwork to the answer, by developing the mathematical tools for the study of the resonance phencmenon based on the iteraction of the shut compensation reactance with the transmission line equations. In order that the actual complexities do not overshadow the fundauental concepts involved, idealistic models are used so that the mathematical relations are simple enough as to provide analytical insights-into the inter-play of basic parameters. Part II proves that a. supersynchronous resonant frequency limit exists.

Resonance in Long Distance Radial Transmission Lines with Static var Compensation, Part I: Frequencies and Mode Shapes

Resonance in Long Distance Radial Transmission Lines with Static var Compensation, Part I: Frequencies and Mode Shapes

Resonance in Long Distance Radial Transmission Lines with Static var Compensation, Part II: Supersynchronous Limit

Resonance in Long Distance Radial Transmission Lines with Static var Compensation, Part II: Supersynchronous Limit

Co-Ordination of Static Var Compensators With Long Distance Radial Transmission System for Damping Improvement

The capability of static var compensators to use supplementary signals for damping improvement has been studied. Damping is shown to be a function of the transmission system loading and a function of the static var compensator The study offers insights as to how static var compensators should be coordinated with respect to the transmission system. The technology under study is based on thyristor controlled reactor with switched capacitors. This paper is concerned with the capability of the static var controller to provide damping in radial long distance transmission lines. It is well known that the lack of positive damping sets a limit to the power transferable across a transmission line By use of supplementary feedback signals, the static var compensator can be made to enhance the system damping. This paper seeks to answer the following questions: 1) For a given design of the supplementary signal feedback, are there any operating regions in which negative damping is encountered? 2) What is the effect of an individual static var compensator in providing damping for a transmission system with multiple compensation systems? 3) What is the analytical model of a static var compensator which uses the thyristor controlled reactor technology? 4) How should the elements of the static var compensator be designed in conjunction with the transmission system when the objective is to improve damping? These questions are answered in the context of a radical line with equally spaced SVC stations as modelled in Fig. 1.

Cross‐sectional equivalent circuits and transmission characteristics of multilayered helical lines having magnetic core

AbstractIt is shown that the transmission characteristics of a cable composed of multilayered media and helical conductors can be solved by network analysis as a radial transmission line problem in cross section. the design method has been simplified for lines such as an H‐line and a multilayer helical line that support surface wave modes. For conventional cable structures the equivalent circuit is given independently for the E‐ and H‐modes if the operating frequency is below the short‐wave range. the circuit elements are then represented as lumped constants appropriate to the medium. the two modes are coupled through the helical conductor, represented by a coupling transformer with a transformation ratio determined by the helical pitch. the equivalent circuit can be simplified by the design condition and as a result the relations between the various cable characteristics and the cable structure and material constants are easily seen, thus easing the problem of cable design. With this method, the transmission characteristics of a two‐layer helical line are calculated and the accuracy is evaluated by comparing the results with those of other methods. It is found that use of a magnetic material in the helix core not only increases the delay effect but also reduces the transmission loss and intensifies the external electromagnetic field.

Multistage linear electron acceleration using pulsed transmission lines

A four-stage linear electron accelerator is described which uses pulsed radial transmission lines as the basic accelerating units. An annular electron beam produced by a foilless diode is guided through the accelerator by a strong axial magnetic field. Synchronous firing of the injector and the acccelerating modules is accomplished with self-breaking oil switches. The device has accelerated beam currents of 25 kA to kinetic energies of 9 MV, with 90% current transport efficiency. The average accelerating gradient is 3 MV/m.

Wideband equivalent circuits for radial transmission lines

This paper reports the wideband impedance characteristics of a radial transmission line, in dominant and higher-order modes, and shows how these characteristics can be accurately represented by a lumped-element equivalent circuit.

A Broad-Band Element for Microstrip Bias or Tuning Circuits (Short Papers)

A microstrip radial transmission line circuit element namely a 180/spl deg/ circular stub or structure, having a reflection coefficient of unity magnitude and phase which varies slowly with frequency is presented. Theoretical reflection coefficient data are shown to agree well with experimental microstrip (epsilon/sub r/=2.35, h =250 mu m) data in X band. Applications of the half-moon microstrip element in the design of broad-band bias or tuning networks are discussed.

Waveguide IMPATT diode oscillators with cap structure

Click to increase image sizeClick to decrease image size Abstract This paper describes the performance of Silicon IMPATT diode (p+ nn+) oscillators with cap structure operating in the IMPATT mode. Our experiments confirm that the oscillation frequency of IMPATT mode can be tuned by varying the cap diameter, which agrees with our calculations using radial transmission line theory.

Circularly symmetric RF commutator for cylindrical phased arrays

A new feed concept is described which greatly simplifies the problem of commutating the RF distribution system of a cylindrical phased array. The feed consists of a circular parallel-plate radial transmission line with a central set of probes and a ring of peripheral probes. The array of probes in the center can be phased to produce an amplitude distribution in the parallel-plate line in any given direction. Proper setting of only two phase shifters connected to the central probes can cause any sector of the peripheral probes to be excited with the proper amplitude distribution necessary to produce a directive pattern with low sidelobes as well as a monopulse difference pattern when the peripheral probes are connected, through collimating phase shifters, to the active radiating elements of a cylindrical array. The cylindrical array can be scanned through <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">360\deg</tex> in fine increments by continued indexing of the amplitude distribution generated by the central probes. Experimental <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> band hardware, built to prove the feed technique, is described. Nine central probes in a 0.25-inch thick 21-in diameter model produced a cardioid distribution and an orthogonal figure-eight distribution which could be commutated together by adjustment of two phase shifters. Measured insertion loss between the central probes and 48 peripheral probes showed only 0.1-dB loss over a 6-percent band. Coupling measurements between the three available central terminals indicated isolation between the various ports of 23-35 dB. The minimum insertion loss and the corresponding transmission phase between the central feed and the peripheral probes was shown to be independent of the setting of the two control phase shifters which were set to have conjugate phase shift.

A flat-feed technique for phased arrays

A recently developed phased-array feed configuration offering significant advantages over the conventional space, corporate, and series feed techniques is described. This technique, referred to as the flat feed, allows power division for monopulse sum and difference pattern illumination functions in a feed depth of less than a half-wavelength with low loss. The technique used to extract energy from the power divider, which consists in part of a radial transmission line, results, in its simplest configuration, in a circular grid of antenna elements. Relations governing the circular grid array geometry design are derived which relate the angular locations of attenuated grating lobes to the spacing between the rings of radiating elements. Experimental S -band hardware, built to prove the feed technique, is described. It includes a multimode launcher with measured coupling between circular wavegulde sum ( TM_{01} ) and difference ( TE_{11} ) modes of less than -37 dB; a seven-ring 1:195 radial power divider measured across a 10-percent band to have insertion loss of 0.1 dB and rms phase and amplitude deviations of less than 3.5\deg and 0.47 dB; a 144-element array whose measured sum and difference beam radiation patterns are compared with calculated patterns for scan angles out to 60\deg and whose sum port VSWR, measured across a 10-percent band, was under 1.8:1 with the array steered to broadside, and under 1.5:1 for other scan angles out to 60\deg .

Characterization of Packaged Microwave Diodes in Reduced-Height Waveguide

A technique for the measurement of package parasitic and equivalent-circuit parameters of microwave semiconductor devices at the frequency of operation is presented. In this method a two-port coupling circuit is found which transforms the impedance measured in rectangular waveguide to the terminals of the equivalent circuit used to represent the semiconductor device. This approach combines known properties of radial transmission lines and of impedance measurement in the TE/sub 10/-mode full-height waveguide to obtain an analytical referencing technique for a diode mounted across a reduced-height waveguide. Application of this technique is illustrated by measurements of several varactor diodes.

Propagation on a Cylindrical Surface Wave Structure Having Radially Nonuniform Dielectric

The possibility that a radially nonuniform dielectric might enhance the propagation characteristics of a surface wave line is discussed in terms of the axial cylindrical surface wave on a cylindrical structure. Attention is given to the field structure in the dielectric to determine the effect of the nonuniformity on the dielectric loss. Conclusions are deferred, however, until the change in surface impedance is also examined, since it essentially determines conductor loss and decay coefficient. The surface impedance is examined using the radial transmission line formalism of Marcuvitz. The modified field structure in the nonuniform dielectric and the concomitant change in dielectric loss is found to be most important for the surface wave structure; the nonuniformity changes the surface impedance only slightly since it is already highly reactive.

Radial Line Band Rejection Filters in Coaxial Waveguides

Among the simplest and least expensive structures which serve as band rejections filters in the microwave region is the coaxial waveguide with a cylindrical cavity forming a discontinuity in the outer conductor. When the outer conductor of a coaxial waveguide is perturbed by a shorted radial transmission line, the structure acquires a zero of transmission for the TEM mode at a resonant frequency that depends on as many as six parameters. Experience indicates that in restricted regions certain approximate methods, in which one or several of the parameters are neglected, produce fairly accurate results. However, discrepancies of 5% or more are encountered in other regions where the same approximations ought to be valid. The approximations most frequently used correspond to either one of the following situations: (a) total disregard of the fringing fields caused by the two close discontinuities, in which case the cylindrical cavity is represented by a series impedance equal to the input impedance of a shorted radial transmission line; (b) consideration of the fringing fields associated with each discontinuity, but neglect of the interaction between the two. In the latter, the discontinuities are accounted for by equivalent shunt lumped reactive elements, however, they must be far enough apart so that the interaction is indeed negligible.

Transmission and Reception Properties of an Equatorial Slot Antenna on a Reentry Sphere

The reentry vehicle model employed in this study consists of a plasma‐clad sphere with a narrow circumferential slot cut at the equator. The slot is excited by a biconical transmission line driven at its center by a coaxial cable. The homogeneous plasma is assumed to be in contact with the sphere.The driving‐point impedance referred to the input terminals and the radiation field in terms of the input current are determined. The efficiency of transmission is calculated by taking the ratio of the power obtained by integrating the Poynting vector over the surface of a great sphere to the power supplied the linearly tapered radial transmission line by the coaxial cable. The voltage appearing across an impedance connected to the terminals of the biconical transmission line is evaluated in terms of the amplitude of an incident plane‐wave electromagnetic field.Numerical results are presented exhibiting the transmission and reception qualities of the equatorial slot antenna on the reentry sphere for a range of frequencies and plasma properties.

An Improved Ground Beacon Antenna

An electromechanical scanning antenna technique is proposed to provide improved TACAN ground-beacon performance over the full 960-to 1215-Mc band.A radially symmetric, shaped-beam reflector is illuminated by an off-set, radial-pillbox horn. The horn is driven by a radial transmission line which contains a central radiator. Parasitic elements are arranged in dielectric rings positioned concentrically with the central radiator. The rings are rotated uniformly about the center line to generate an amplitude-modulated, omnidirectional azimuth pattern. The complex response of the elements controls the percentage modulation, while the geometry of the reflector and its feed independently control the shape of the elevation pattern. The antenna generates uniform azimuth modulation over the elevation angles of interest.

Analysis of Signal Transmission in Ultra High Speed Transistorized Digital Computers

The transmission of digital signals plays an important role in high speed computers, not only because the traveling time on the connecting wire is a significant portion of the total delay, but also because the wire is a distributed parameter coupling network which, as a transmission line, becomes an integral part of the computer circuitry and affects the over-all performance. The classical theories of transmission lines are applied to study the signal waveforms. In the case of low input impedance loads, the radial (or parallel) transmission line scheme should be used. A mathematic relationship can be derived among the ramp slope of signals, the input current to the loads, the length and the impedance of the lines, and the terminations. Then the reflections can be predicted. Guided by this, one chooses the optimum line impedance, the maximum length and the proper termination. For high input impedance loads, the tapped transmission line scheme can be used. The multiple junction reflections are expressed in terms of a series which can be worked out by hand or by machine computation. Likewise, there is a relationship among the impedance of the tapped lines and the feeding line, the spacing of loads and the terminations. There are rules to be followed to decide the transmission scheme.

Leaky wave antennas II: Circular waveguides

The propagation characteristics of leaky waves on slotted circular cylinders are derived by the methods described in an earlier paper on leaky rectangular waveguides. The cross section of a typical leaky circular wavegaide is represented by a radial transmission line network incorporating a lumped terminating admittance which characterizes the slot discontinuity and the external region. The expression for the lumped admittance is obtained by combining an integral equation solution with a variational procedure. The resonances of this transverse network, which yield the complex propagation constants for the leaky waves, are solved by perturbation techniques to produce results in simple and practical form. Solutions are obtained for leaky waves corresponding to two different excitations of a slotted cylinder and these results are shown to compare favorably with measured values.

A Note on the Derivation of the Fields in a Radial Line (Correspondence)

The concept of a radial transmission line is frequently used in the description of such devices as cylindrical cavity resonators and horn radiators. An approach to the prob-lem of determining the electric and magnetic fields in the radial line has been to solve Maxwell's equations in component form with appropriate boundary conditions. While the following derivation yields nothing new, it does, however, have the advantages of being simple and of requiring a minimum of guess work as compared to other methods of solving this problem.