Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1956"
TL;DR: In this article, an analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented, where the input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes.
Abstract: An analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented. The input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes. A zero decibel directional coupler is described and its possible use as a duplexer is proposed. The design of multiple stub directional couplers for any degree of coupling is discussed. A method of computing the bandwidth of all these couplers is outlined, and the bandwidth curves, the power out the various arms with respect to frequency of the zero decibel coupler, are computed. A tabulation is made for six different 3 db couplers (even-power split) and their standing wave ratio, evenness of power split and isolation of the fourth arm as a function of frequency assuming perfect performance at the band center.
471Â citations
TL;DR: In this paper, the theory of operation of coupled strip line tilt ers and directional couplers is described, and information from which these components may be easily designed, and the results of these components are presented.
Abstract: This paper describes the theory of operation of coupled strip line tilt ers and directional couplers, and presents information from which these components may be easily designed. Low-pass, band-pass, all-pass, and all-stop filter characteristics are obtained from these coupled lines either by placing open or short circuits at two of the four available terminal pairs, or by interconnecting two of the terminal pairs. Directional couplers having perfect dk-ectivity and constant input impedance at all frequencies, and for all degrees of coupliig, are obtained by placing equal resistive loads at each of the four terminal pairs.
379Â citations
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TL;DR: In this article, the properties of two-wire and single-wire transmission lines are compared on a comparative basis and the main domain of the twowire lines lies in the frequency range below 100 cm and that of the single wire line in the range above 100 cm.
Abstract: The properties of two-wire lines and single wire lines (surface wave transmission lines) are discussed on a comparative basis. The two-wire line is actually a system of two coupled single wire lines and thus requires a high degree of symmetry to maintain the desired wave mode. While the single wire line is more affected by bends it has the advantages that it is simpler in construction and is less susceptible to weather conditions. The main domain of the two-wire lines lies in the frequency range below 100 mc and that of the single wire line in the range above 100 mc.
310Â citations
TL;DR: In this article, a new type of microwave filter is presented in which resonance occurs in the form of a traveling wave rather than in the conventional form of standing wave, which is a constant-resistance circuit, and therefore presents a very low input vswr.
Abstract: A new type of microwave filter is presented in which resonance occurs in the form of a traveling wave rather than in the conventional form of a standing wave. This device is a constant-resistance circuit, and therefore presents a very low input vswr. Formulas for loaded Q and insertion loss are given. Experimental results verify the theoretical approach. This filter, which is constructed of a transmission-line loop and two directional couplers, finds application in multiplexing filters as well as in matched band-pass and band-rejection filters.
56Â citations
TL;DR: In this paper, the authors proposed a low-loss circulator for the 10.7 kmc to 11.7kmc band with a more than 30-db return loss at each terminal, an isolation of 30 db or greater between isolated terminals, and a 0.35db insertion loss between transmission terminals.
Abstract: The discovery of a simple, low loss way to hold Faraday rotation constant over a broad-band (coupled with the development of wide-band, high return loss, circular-to-rectangular waveguide transformers, and polarization couplers) has made it possible to design and build a high quality circulator for use in the 10.7 kmc to 11.7 kmc band. The essential characteristics of the described unit include a more than 30-db return loss at each terminal, an isolation of 30 db or greater between "isolated" terminals, and a 0.35-db insertion loss between transmission terminals.
44Â citations
TL;DR: In this paper, the characteristic impedance of the shielded slab line is worked out exactly in terms of elliptic functions, and a design graph is given to cover most practical applications, which is the basis for this paper.
Abstract: The characteristic impedance of the shielded slab line is worked out exactly in terms of elliptic functions. A design graph is given to cover most practical applications.
38Â citations
TL;DR: In this paper, a variational method is used to develop an expression for the characteristic impedance of a "trough line" consisting of a circular cylinder mounted inside and parallel to the walls of a semi-infinate rectangular trough.
Abstract: A variational method is used to develop an expression for the characteristic impedance of a "trough line" consisting of a circular cylinder mounted inside and parallel to the walls of a semi-infinate rectangular trough. The "slab line" consisting of a circular cylinder between infinite, parallel plates is treated as a special case of the trough line in which the bottom of the trough is taken to be infinitely remote from the circular cylinder. The solution has not been restricted to cylinders that are mounted exactly half way between the parallel walls of the trough; a simple formula is presented for calculating the tolerances which must be placed on the "centering" of the center conductor for a given allowable error in the characteristic impedance. The expression for the characteristic impedance is presented as the sum of three terms. The first is a "zero order" logarithmic term, the second a "second order" correction term which vanishes as the center conductor becomes infinitely small, and the third is an "off-center" correction term which arises when the cylinder is not exactly half way between the parallel walls of the trough. The second order correction term amounts to about 0.3 ohms when the characteristic impedance is of the order of 50 ohms. A fourth order approximation using the same method changes this by about 0.001 ohm.
35Â citations
TL;DR: In this paper, the authors considered the design of loop couplers of any length and their application to either coaxial line or waveguide are discussed, and the theoretical basis for design is established by first considering the theory of coupled transmission lines.
Abstract: For many years the design of loop type directional couplers has relied heavily on experiment. One of the most common varieties has been the loop coupler much shorter than a wavelength and having a built-in termination (vestigial arm). In this paper the criteria for the design of loop couplers of any length are considered, and their application to either coaxial line or waveguide are discussed. The theoretical basis for design is established by first considering the theory of coupled transmission lines. Several designs which utilize a quarter-wavelength or shorter loops and which have very desirable features with regard to coupling, directivity, and band-width are illustrated. Typical performance of couplers having couplings of 20-40 db and directivities of over 30 db are presented.
34Â citations
TL;DR: In this article, the authors present theoretical and experimental results in the application of finline coupler techniques to low-pass microwave filters and conclude with a discussion of the origin and successful elimination of such effects.
Abstract: Detailed studies of transmission properties of the finline coupler have revealed existence of certain phenomena which adversely affect the transmission characteristics. A discussion of the origin and successful elimination of such effects is described. New applications for the finline coupler have been found in the design of hybrid junctions, twists and bends in multimode waveguide, and other polarization selective devices. The paper concludes with a presentation of theoretical and experimental results in the application of finline techniques to low-pass microwave filters.
33Â citations
TL;DR: In this paper, a broadband dual-mode waveguide transducer designed to couple two orthogonal TE/sub 11/circular waveguide modes in separate rectangular waveguide ports is described.
Abstract: This paper describes a broad-band dual-mode waveguide transducer designed to couple two orthogonal TE/sub 11/ circular waveguide modes in separate rectangular waveguide ports. A compact, rugged, and economical junction has been developed to operate from 8600 mc to 9600 mc with a vswr of less than 1.15 at the rectangular port and a mode isolation of 50 db or greater. Developmental models are described to indicate the evolution from theory to the final model. Some problems encountered in attaining a small physical size are discussed in detail. The new junction has application to mode multiflexing, circular waveguide ferrite devices, circular polarization, and as a circular wave guide magic-T.
30Â citations
TL;DR: Theory and performance of a narrow band circulator employing but a single junction and a 45-degree Faraday rotator are discussed in this article, where factors affecting bandwidth are considered and pertinent curves are plotted.
Abstract: Theory and performance of a narrow band circulator employing but a single junction and a 45-degree Faraday rotator are discussed. Factors affecting bandwidth are considered and pertinent curves are plotted. Isolation bandwidth curves permit prediction of performance. This compact circulator, although frequency sensitive, is tunable and provides high reverse and cross isolations making it especially suited to duplexing, isolating and switching applications.
TL;DR: In this paper, design techniques for waveguide hybrid tee junctions, resulting in convenient structures and simple internal matching elements for increased bandwidth and power-handling capacity are described, and experimental data are given.
Abstract: Design techniques for waveguide hybrid tee junctions, resulting in convenient structures and simple internal matching elements for increased bandwidth and power-handling capacity are described, and experimental data are given.
TL;DR: In this paper, a serrated choke was proposed to permit cuts or gaps anywhere on the walls of a rectangular waveguide and the low gap impedance was provided essentially by closely spaced, quarterwave-length, open-ended, two-wire-line stubs.
Abstract: A new type of serrated choke will permit cuts or gaps anywhere on the walls of a rectangular waveguide. The low gap impedance is provided essentially by closely spaced, quarter-wave-length, open-ended, two-wire-line stubs. Low power and high power characteristics of many designs are presented.
TL;DR: In this paper, the propagation of a second type of TEM mode in a slotted coaxial line is analyzed by means of variational expressions giving upper and lower bounds to the true value.
Abstract: The propagation of a second type of TEM mode in a slotted coaxial line is analyzed. The characteristic impedance of the slotted line is evaluated by means of variational expressions giving upper and lower bounds to the true value. A two term approximation to the charge distribution and a one term approximation to potential distribution give results accurate to within +-2 per cent. Curves of characteristic impedance against angular slot width are presented.
TL;DR: In this article, the relationship between dielectric constant and the measured shift in standing-wave minimum is plotted in such a way that all possible values within any predetermined range are read directly from the graph with no computation whatsoever.
Abstract: The problem of evaluating dielectric constant and loss tangent by the short-circuited-waveguide technique has been encountered continually in recent years in the study of artificial dielectric media and radome materials. In general, practical measurements have involved materials with low loss and dielectric constants less than 10. The analytical method normally applied to data on such materials requires laborious computation. The available graphical methods have not completely eliminated computation and have provided answers of unsatisfactory accuracy. The present paper describes rapid graphical techniques for evaluating dielectric constant and loss tangent from the quantities normally measured with the slotted line, using samples of arbitrarily chosen length. It begins with equations previously derived for the case of low-loss media. By use of a new parameter, the relationship between dielectric constant and the measured shift in standing-wave minimum is plotted in such a way that all possible values of dielectric constant within any predetermined range are read directly from the graph with no computation whatsoever. A graph can be readily prepared to apply over a full range of frequency to all sizes of rectangular waveguide.
TL;DR: In this paper, the reverse-to-forward loss ratio of these isolators is high (150 to 1 at X band) and the reverse loss per unit length is also high (20 db/inch at X bands).
Abstract: The early resonance isolators, using nearly full waveguide height ferrite slabs, gave a high reverse loss per unit length but a disappointingly low reverse-to-forward loss ratio. By substantially reducing the height of the ferrite slabs, the reverse-to-forward loss ratio can be increased at the expense of reverse loss per unit length. More recently, it has been found that the addition of certain dielectric loading in rectangular waveguide resonance isolators results in generally improved performance. Thus, the reverse-to-forward loss ratio of these isolators is high (150 to 1 at X band) and the reverse loss per unit length is also high (20 db/inch at X band). The broad-banding problem will also be briefly discussed.
TL;DR: In this paper, the state-of-the-art with respect to rectangular ridge waveguide is described, giving tables and data from standard waveguide sizes and constructional techniques for both rigid and flexible waveguide.
Abstract: This paper describes the present state of the art with respect to rectangular ridge waveguide giving tables and data from standard waveguide sizes and constructional techniques for both rigid and flexible waveguide. The problems inherent in waveguide connectors are discussed along with the various methods for producing waveguide assemblies. The problems inherent with present-day waveguide standardization are also discussed. It is essential that a series of standard waveguide for high pressure operation and for extremely broadband operation (ridgeguide) be standardized. The latest RETMA miniature standard flanges are shown along with present-day thinking on a series of pressurized contact flanges.
TL;DR: In this paper, the effect of finite thickness in the idealized situation of a semi-infinite array of perfect conductivity, is treated theoretically and experimentally for normal incidence of a uniform plane wave on the plane interface separating the medium from free space.
Abstract: An array of parallel metallic plates of finite thickness are useful in microwave lenses. The effect of finite thickness in the idealized situation of a semi-infinite array of perfect conductivity, is treated theoretically and experimentally for normal incidence of a uniform plane wave on the plane interface separating the medium from free space. The theoretical discussion involves the approximate variational method and a procedure is given for estimating the order of magnitude of the error in the final result. It is shown that it can be advantageous to use plates of finite thickness since the reflection from the interface can be reduced from that existing for infinitely thin plates.
TL;DR: In this paper, a new broadband unidirectional transmission line was built utilizing the difference in energy distribution between two counter-rotating circularly polarized waves in a circular waveguide containing a ferrite.
Abstract: A new type broadband unidirectional transmission line has been built utilizing the difference in energy distribution between two counter-rotating circularly polarized waves in a circular waveguide containing a ferrite. This principle of isolation is different from those which have been used previously. A large difference is observed in the energy distribution of two counter-rotating TE/sub 11/ modes in a ferrite loaded circular waveguide. A ferrite rod magnetized along its axis presents an effective rf permeability of approximately two for the mode rotating in a negative screw sense with respect to the direction of magnetization. For the positive sense of rotation the effective rf permeability becomes very small and negligible energy is transmitted through the ferrite rod.
TL;DR: In this article, a solution to the problem of propagation of higher modes in a transversely magnetized ferrite-filled rectangular waveguide has been found in the form of four rigorous nonlinear algebraic equations.
Abstract: A solution to the problem of propagation of higher modes in a transversely magnetized ferrite-filled rectangular waveguide has been found. The solutions to the problem are expressed in the form of four rigorous nonlinear algebraic equations which characterize the problem and are ready for numerical solution. The dependence of the fields in the direction of magnetization is the same as for the classical modes.
TL;DR: Strip transmission lines offer an alternate medium in which microwave filters can be realized as mentioned in this paper, and strip lines provide a practical means of realizing filters which are simply fabricated and which represent an appreciable saving in size and weight.
Abstract: Strip transmission lines offer an alternate medium in which microwave filters can be realized. Since bandpass filters designed in waveguide or coaxial lines would necessarily be large at ultra-high frequencies, strip lines provide a practical means of realizing filters which are simply fabricated and which represent an appreciable saving in size and weight.
TL;DR: The isometric circles for the direct and inverse linear fractional transformations can be used for transformations of impedances and polarization ratios as mentioned in this paper, and they can also be used to prove the Weissfloch transformer theorem.
Abstract: The isometric circles for the direct and inverse linear fractional transformations can be used for transformations of impedances and polarization ratios. In the Ioxodromic case an inversion is performed in the isometric circle of the direct transformation, followed by a reflection in the symmetry line of the two circles, and a rotation around the origin of the isometric circle of the inverse transformation. In the nonloxodromic case only the first two operations have to be applied. Three illustrative examples are given: the first shows the transformation of the right half of the complex impedance plane into the unit circle (Smith Chart); the second gives a circular proof of the Weissfloch transformer theorem; the third shows an example of cascading, Iossless, two terminal-pair networks.
Abstract: The extension of the (reciprocal) modified Wheeler network to include the more general nonreciprocal two-port is given. This representation is derived via a known decomposition of the general nonreciprocal network into two portions, one reciprocal, the other nonreciprocal. The reciprocal portion is then taken as the modified Wheeler network. Recombination of the elements results in the desired representation which is constituted of a minimum number, i.e., of eight, passive elements. Each of these is a natural idealization of a physical microwave component. Since six of the elements belong to the class of "bilaterally matched" networks, some of the properties of this class are discussed. Two of the bilaterally matched elements embody the nonreciprocal properties of the network: a one-way attenuator and a one-way phase-shifter. Many of the characteristics of the (reciprocal) modified Wheeler network carry over directly to this nonreciprocal representation. The microwave measurement of the network parameters is also indicated.
TL;DR: In this article, the nature of the electromagnetic field of an antenna in the vicinity of a surface of large radius of curvature is discussed, and the solution for a dipole source in the form of the Watson residue series is transformed to a more rapidly converging series which is preferable at short distances.
Abstract: The nature of the electromagnetic field of an antenna in the vicinity of a surface of large radius of curvature is discussed. Assuming a spherical surface, the solution for a dipole source in the form of the Watson residue series is transformed to a more rapidly converging series which is preferable at short distances. Using this result, numerical data is presented in graphical form for the currents induced on the spherical surface. The curves are applicable to both a stub and slot antenna mounted on the conducting surface.
TL;DR: In this paper, the authors derived the effective noise temperature of a gas-discharge noise generator over a wide frequency range by substitution of a loss measurement for the more difficult noise temperature measurement.
Abstract: The effective noise temperature of the output impedance of a Iossy passive network at an arbitrary noise temperature connected to one or more resistive loads at arbitrary noise temperature lies between the highest and the lowest of these noise temperatures, as determined by the losses between the output terminals and the loads. The determination of the effective noise temperature of a gas-discharge noise generator over a wide frequency range is simplified by the substitution of a loss measurement for the more difficult noise temperature measurement. For minimum-noise radar applications care must be used in considering the excess noise of crystal mixers and gas-discharge duplexers. The influeuce of galactic radiation on a receiving system is such that there is an optimum frequency in the region of 200 to 600 mc for minimum "operating noise figure." Typical examples of radio-astronomy measurements are amenable to analysis of the type given. Finally, several corrections to measured noise figure are analyzed.
TL;DR: In this paper, the authors found that the method of shorts as described in three previous papers was too laborious to be practical and proposed a simplification based on reinterpreting and combining the ideas of earlier authors.
Abstract: During the evaluation measurements of several two-port junction devices over a wide band of frequencies the authors found that the method of shorts as described in three previous papers was too laborious to be practical. By reinterpreting and combining the ideas of earlier authors, a valuable simplification was obtained. Since this paper is based upon the previous articles, no fundamental proofs will be given except to show the necessary extensions involved.
TL;DR: Two band-rejection microwave filters employing the waveguide cutoff effect are discussed in this paper, where one type utilizes the cutoff property in the series arm of an E plane tee to improve the filter's characteristics, while the other utilizes this property in both the E and H arms of a magic tee.
Abstract: Two band-rejection microwave filters employing the waveguide cutoff effect are discussed One type utilizes the cutoff property in the series arm of an E plane tee to improve the filter's characteristics, while the other utilizes this property in the E and H arms of a magic tee Experimental data for both single and multistage filters are presented Methods of obtaining low standing wave ratios over a broad pass-band are also presented
TL;DR: In this article, a single-sideband modulator for shifting the frequency of an x-band signal by means of a rotating magnetic field transverse to a ferrite differential half-wave section is described.
Abstract: This paper describes a single-sideband modulator for shifting the frequency of an x-band signal by means of a rotating magnetic field transverse to a ferrite differential half-wave section. The device is one of the first practical applications of the double-refraction properties of ferrites. Improvements over an earlier model include reduction in size and continuous operation without drift. An efficient and compact magnetic structure has been designed for producing the rotating magnetic field. Excessive heating of the ferrite and voltage breakdown of the coils is eliminated by a forced-air cooling system. The modulator shifts the microwave-carrier frequency of 9375 mc by plus or minus 20 kc. With a rotating field of approximately 200 oersteds the microwave insertion loss is 1.0 db. The undesired sideband suppression is above 40 db while the carrier suppression is 23 db. For a frequency bandwidth of 500 mc, the insertion loss remains below 5 db.
TL;DR: In this paper, absolute measurements of noise figures in the UHF range were described, using hot and cold thermal sources as standards, and it was found that the noise temperature of the T-5 6 watt fluorescent tube is 16.1 kO.
Abstract: Absolute measurements of noise-figures in the UHF range are described, using hot and cold thermal sources as standards. It was found that the noise temperature of the T-5 6 watt fluorescent tube is 16.1 kO.6 db above k T delta v. Noise diodes were found to be in error at these frequencies by approximately 1 db.
TL;DR: The ferrite isolator and the ferrite circulator have been applied separately to improve the accuracy of measuring small microwave noise powers or small power differences as discussed by the authors, which has been shown to increase the sensitivity of the receiver to near the theoretical limit.
Abstract: The ferrite isolator and the ferrite circulator have been applied separately to improve the accuracy of measuring small microwave noise powers or small power differences. Either the isolator or the circulator effectively isolated the input circuit of a microwave receiver from the impedance of the source. As a result, the measurement errors introduced by mismatched source impedances were reduced by as much as 98 per cent. The added input circuit losses of the ferrite components reduced the receiver sensitivity by only about 10 per cent. Since the accuracy of measuring small noise power differences was limited principally by impedance errors, the addition of ferrite isolation to the receiver input circuit increased the sensitivity of measurement to near the theoretical limit. The ferrite isolator was used as a passive transmission element in these experiments. The ferrite circulator, however, was used as an electrically-operated, microwave switch. This switch was used to replace the mechanical chopper in a Dicke-type radiometer. In addition to impedance isolation, the ferrite switch makes possible rapid comparison measurements of the microwave noise powers from any two sources, or of the noise powers from the same source in two different polarizations.