Antennas and Propagation, Transactions of the IRE Professional Group on
This Transactions ceased publication in 1955. The current retited publication is IEEE Transactions on Antennas and Propagation.
Latest Published Articles

Optimum patterns for arrays of nonisotropic sources
Dec10 2012 
Impedance measurement techniques for twomode guides
Dec10 2012 
Slot radiators and arrays at Xband
Dec10 2012 
Large slots in circular and rectangular waveguides
Dec10 2012 
The lower E and D regions of the ionosphere as deduced from long wave measurements
Dec10 2012
Popular Articles

Design of linesource antennas for narrow beamwidth and low side lobes
Feb24 2011 
A new antenna feed having equal E and Hplane patterns
Jan06 2003 
On the theory of corrugated plane surfaces
Jan06 2003 
Electrically small antennas and the lowfrequency aircraft antenna problem
Jan06 2003 
Microwave radio reflection from ground and water surfaces
Jan06 2003
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Popular Articles (April 2015)
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1. Design of linesource antennas for narrow beamwidth and low side lobes
Publication Year: 1955 , Page(s): 16  28
Cited by: Papers (129)  Patents (3)It is well known that the phenomenon of radiation from linesource antennas is very similar to that of the diffraction of light from narrow apertures. Unlike the optical situation, however, antenna design technique permits the use of otherthanuniform distributions of field across the antenna aperture. Line source synthesis is the science of choosing this distribution function to give a radiation pattern with prescribed properties such as, for example, narrow angular width of the main lobe and low side lobes. In the present article the mathematical relationships involved in the radiation calculation are studied from the point of view of function theory. Some conclusions are drawn which outline the major aspects of synthesis technique very clearly. In particular, the problem of constructing a line source with an optimum compromise between beamwidth and sidelobe level (analogous to the Dolph  Tchebycheff problem in linear array theory) is considered. The ideal pattern is cos π √ {u /sup 2/  A/sup 2/} , where u = (2a/λ) cos θ, a is the halflength of the source, and cosh π A is the sidelobe ratio. Because of theoretical limitations, this pattern cannot be obtained from a physically realizable antenna; nevertheless its ideal characteristics can be approached arbitrarily closely. The procedure for doing this is given in detail. View full abstract»

2. A new antenna feed having equal E and Hplane patterns
Publication Year: 1954 , Page(s): 113  119
Cited by: Papers (29)  Patents (1)When two complementary sources are combined in the proper amplitude and phase, desirable radiation characteristics for feeding a circular aperture are obtained. It is shown that when the feed is achieved there results a circular beam cross section which optimizes the efficiency of illumination of a circular aperture. The back radiation from the feed is down 30 db from that in the forward direction, minimizing interference effects between feed and aperture. It is the purpose of this thesis to show how a feed composed of complementary sources has been physically realized and to present and discuss experimental radiation and impedance data. It is well known that the radiation pattern of an electric dipole is a circle in the plane and a figure 8 in the plane. An openended coaxial line carrying the mode is similar to a magnetic dipole; i.e., the plane is nearly circular while the plane is like a figure 8. These two sources have been combined to produce a feed whose  and plane patterns are of equal width. The complementary source idea has been applied to feeds of both linear and circular polarization. The linearly polarized feed is excited from rectangular waveguide and is simple to fabricate. It can be easily matched over a broadband. This feed has been used to illuminate a 20inch parabola with the result that the secondary and planes are of equal width and the side lobes are 30 db down from the main radiation. The circularly polarized feed is excited from a circularly polarized mode in coaxial line. The radiating structure maintains circular symmetry and the axial ratio remains essentially constant over a large portion of the beam. View full abstract»

3. On the theory of corrugated plane surfaces
Publication Year: 1954 , Page(s): 71  81
Cited by: Papers (40)  Patents (1)An analysis is given of an electromagnetic system composed of a rectangular waveguide in tandem with a corrugated waveguide which feeds a flat, corrugated surface of arbitrary length terminated by a ground plane, whose length is also arbitrary. An improved procedure of field determination is used which combines Floquet's theorem and the variational principle, thus revealing an additional requirement on the corrugation geometry. Factors influencing a match at the feed mouth, and satisfactory launching of the surface wave are discussed. The degree of suppression of the feed radiation is given in db as a function of the geometry of the system. Approximate radiation patterns are derived for two cases, (a) when the system is terminated by an infinite ground plane, and (b) when the system is terminated by a finite ground plane. For the latter case, an upper bound on the tilt angle of the main beam and a lower bound on its beamwidth result from an approximate theory. For both cases, the HansenWoodyard endfire relation is found to provide beam sharpening even when the feed radiation is considered. The presence of higher order surface modes, their effect, and their elimination are discussed. Comparison of the theory with experiment is reasonably good. View full abstract»

4. Electrically small antennas and the lowfrequency aircraft antenna problem
Publication Year: 1953 , Page(s): 46  54
Cited by: Papers (7)This paper is concerned with the properties of antennas which are small relative to their operating wavelength. A brief analysis based upon quasistatic principles is presented, and two experimental procedures suggested by the nature of the analytical results are described. The application of these experimental procedures is illustrated with examples of measurements made in connection with the design of lowfrequency aircraft antennas. View full abstract»

5. Microwave radio reflection from ground and water surfaces
Publication Year: 1952 , Page(s): 37  45Reflection of microwaves from ground and water surfaces for a number of wavelengths between 0.86 and 26.5 centimeters have been measured over paths of a few thousand feet and grazing angles of the reflected ray up to 5 degrees. Antennas with comparable patterns large enough to illuminate a large surface area were used. A variety of surface conditions including bare ground and smooth and choppy water were studied. For the particular overland path used, the ground appeared smooth at 26.5 and 9 centimeters wavelength, evidenced considerable roughness to 3.2 centimeters and appeared very rough to 0.86 centimeters. The mean reflection coefficient decreased with decreasing wavelength. For the overwater paths, the reflection for all wavelengths was that associated with a smooth surface when the conditions were calm. For a choppy surface, the millimeter signal showed large time variations and its apparent reflection coefficient decreased. View full abstract»

6. Analysis of helical transmission lines by means of the complete circuit equations
Publication Year: 1954 , Page(s): 132  143
Cited by: Papers (3)A set of integrodifferential equations, called the "complete circuit equations," are derived from Maxwell's equations and applied to the solution of the parallelwire transmission lines the doublehelix transmission line, and the single helix, or helical waveguide. These equations take into account the effects of inductance and capacitance distribution, retardation, and outward radiation. A generalization of earlier concepts of distributed inductance and elastance (or inverse capacitance) is manifest in the solution of the helical lines where these quantities become functions of the phase coefficient or wavelength of propagation and are Fourier transforms of certain closedform distribution functions. In general, phase velocity is a complicated implicit function of frequency, but under a hypothesis of "mode segregation on the basis of wavelength" the phase velocity and frequency can be obtained parametrically in terms of a third variable, called the phase parameter. Using this hypothesis, plots of phase velocity and characteristic impedance versus frequency were obtained for the double helix and the helical waveguide. View full abstract»

7. Paraboloid reflector and hyperboloid lens antennas
Publication Year: 1954 , Page(s): 119  127
Cited by: Papers (19)A theoretical analysis of the radiating properties of the paraboloid reflector and the hyperboloid lens shows that low amplitude crosspolarized radiation and high gain factors can be obtained from a paraboloid reflector excited by a planewave source. Low amplitude, crosspolarized radiation can also be obtained from the hyperboloid lens with a planewave feed, but with a lower gain factor. It is found that the measured properties of the antennas agree reasonably well with the theoretical predictions. Also it is found experimentally that principal plane side lobes of the order of 40 db can be obtained with a short focal length hyperboloid lens. View full abstract»

8. Impedance matching by means of nonuniform transmission lines
Publication Year: 1952 , Page(s): 107  109A transmission line of varying characteristic impedance is often used as a fourterminal microwave network for the purpose of matching a load having one impedance to a generator having a different impedance. My main point can be summed up by one equation, giving the value of the reflection coefficient at the input or source end of the transmission line. In this equation, x is distance measured along the transmission line, x_{S} and x_{L} are values of x at the generator and load ends of the line respectively, β is the phase constant, and Z_{0} is the characteristic impedance. View full abstract»

9. Large slots in circular and rectangular waveguides
Publication Year: 1952 , Page(s): 108  112This report, which was supported by the Office of Naval Research under contract N7onr29529 with the Antenna Laboratory, Institute of Engineering Research, deals with rectangular apertures in the wall of a waveguide whose dimensions are such that the lengthtowidth ratio is of the order of unity, the length being in the neighborhood of a half wavelength. We speak of these elements loosely as slots, though in the strict sense of the word a slot is an aperture whose width is small compared with its length. The properties of the larger aperture elements are not known as well as those of the narrow slot. The study of the properties was undertaken both for its bearing on the general theory of apertures and for the potentialities of aperture elements for antenna design work. Whereas the nature of the excitation of a narrow slot is a function of its length primarily, that of the larger aperture element is strongly dependent on its position on the waveguide wall and its orientation with respect to the dominant mode in the guide. The excitation also depends on the nature of the termination of the waveguide beyond the aperture. The greater variety of inclinations that can thus be obtained suggests possible developments in beam synthesis techniques. View full abstract»

10. Radiation from a vertical dipole over a stratified ground (Part II)
Publication Year: 1954 , Page(s): 144  146
Cited by: Papers (3)Further results are given for the problem of a vertical electric dipole situated over a horizontally stratified conductor. It is pointed out that under certain conditions the surfacewave field intensity for a stratified conducting ground is greater than the corresponding case for a perfectly conducting ground. Numerical values for the attenuation factor are also given. View full abstract»

11. Theory of waveguidefed slots radiating into parallelplate regions
Publication Year: 1952 , Page(s): 63  66Slotted waveguide arrays feeding into parallelplate regions have been used in some high speed scanners. Parallelplate regions also have been used for the suppression of secondorder beams of highgain arrays. A theoretical expression is derived for the conductance of a longitudinal shuntslot in a rectangular guide when the slot is radiating into a parallelplate region of arbitrary plate spacing. Some peculiarities of the theoretical results are discussed. There is good agreement between theory and experiment. View full abstract»

12. The design of circularly polarized aperture antennas
Publication Year: 1952 , Page(s): 136By using equivalent circuits, the polarization transmitted from an aperture is analized in terms of the reflection properties of the aperture, the length of the Waveguide, and pertinent parameters of the exciting antenns. The techniques described afford a systematic procedure for designing antennas which are circularly polarized at one frequency or which have a low axial ratio over a band of frequencies, This procedure may be used to solve which have been applicable to lessless antennas are derived. Systems for measuring all pertinent parameters are developed and theoretical predictions are correlated with experimental measurements. View full abstract»

13. A rotary joint for two microwave transmission channels of the same frequency band
Publication Year: 1952 , Page(s): 136This dualchannel rotary joint consists of two pairs of rectangular waveguide terminals, a circular waveguide which transmits both channels, and coupling elements between the rectangular waveguide terminals and the circular waveguide which convert the rectangular H
10 mode into the circular H01 and E01 modes. If pure H01 and E01 modes can be excited, perfect separation of the channels as well asconstant amplitudes and phases can be obtained when the Joint rotates. While the conversion into the circular E01 mode is performed by a conventional method, a new method had to be developed for the conversion of the rectangular H10 mode into the circular H01 mode. View full abstract» 
14. Guided wave concept in electromagnetic theory
Publication Year: 1952 , Page(s): 231  239First Page of the ArticleView full abstract» 
15. Modes in waveguides containing ferrites
Publication Year: 1952 , Page(s): 104  105
Cited by: Papers (4)First Page of the ArticleView full abstract» 
16. A synthesis method for circular and cylindrical antennas composed of discrete elements
Publication Year: 1952 , Page(s): 251  261
Cited by: Papers (3)Antennas composed of discrete elements equally spaced in angle around a circle or circular cylinder are studied with the objective of designing such antennas to produce required azimuthal radiation patterns. Much has already been written upon this subject under the assumption that a continuous distribution of elementary sources will be an acceptable solution to the design problem or at least will form a step in the attainment of an acceptable solution. In the present writing, however, it is felt that something may be gained by analyzing the problem from the beginning on the basis of discrete elements. The question of how many elements are needed is discussed in detail and it is shown that the envelope of the excitation coefficients is not necessarily equivalent to the continuous solution available by other methods. Practical procedures for finding the envelope of the excitation coefficients, and hence the coefficients themselves, are outlined. View full abstract»

17. Mechanical scanners for radar antennas
Publication Year: 1952 , Page(s): 135The mechanical scanner is the most versatile and widely used antenna system for airborne radar application. In general, its radiation characteristics are superior to those of electrical scanned systems. There are three basic types of scanners: The wigwag, spiral, and helical. These basic types of scanners, along with various modifications of each, are discussed and compared, insofar as possible, with other than mechanical scanners. Such characteristics as relative size weight, scanning speeds, broadband matching, absolute gain, halfpower beamwidth, relative minor lobe intensity, and aperture efficiency are compared and general rules are submitted as to how to choose which type of scanner will best perform in a given type of service. View full abstract»

18. A twodimensional microwave luneberg lens
Publication Year: 1953 , Page(s): 12  23
Cited by: Papers (13)  Patents (9)SummaryA twodimensional microwave model of the Luneberg lens has been designed employing the TE
10 mode. It consists of two 36inch diameter, almostparallel, conducting plates with the space between plates filled with polystyrene. Its thickness varies with the normalized radius, T, to give the desired index of refraction n = Due to symmetrp about the center, this lens maintains constant gain and beam shape as a feed is scanned over its circumference, while the side lobe level remains at least 18 db below peak power. Experimental patterns show good agreement with computed patterns in the two principal planes. View full abstract» 
19. Double parabolic cylinder pencilbeam antenna
Publication Year: 1955 , Page(s): 4  8
Cited by: Papers (2)Radiation from a point source placed on the focal line of a parabolic cylinder is reflected in succession from this cylinder and from a second parabolic cylinder crossed so that its focal line coincides with the directrix of the first cylinder. The two reflections result in a parallel beam. The theory is applicable to both microwaves and light. The advantages of shipping the cylinders in the form of flat sheets and the possibilities of independent control of horizontal and vertical beamwidths and shapes are pointed out. Experimental models have been built and tested. View full abstract»

20. Slot radiators and arrays at Xband
Publication Year: 1952 , Page(s): 62  84Experimental verification of the validity of Stevenson's expression for a longitudinal shunt slot has been obtained. The theoretical expression has been found to be valid throughout Xband. Substantiating curves are shown, Resonant slot lengths as functions of slot dimensions and position on the waveguide are given. Correlation. between the phase angle of the admittance and the phase angle of the radiated field of a slot has been established. The behavior of the radiation pattern as a function of the position of the slot on the waveguide is shown. The characteristics of linear arrays of these slots are given, and some of the applications are indicated. View full abstract»

21. On spherically symmetric lenses
Publication Year: 1952 , Page(s): 66  71
Cited by: Papers (7)First Page of the ArticleView full abstract» 
22. Mutual impedance of stacked rhombic antennas
Publication Year: 1954 , Page(s): 39
Cited by: Papers (1)First Page of the ArticleView full abstract» 
23. Evaluation of errors in an eightelement adcock antenna
Publication Year: 1954 , Page(s): 159  162
Cited by: Papers (2)An analysis is given for the response of an eightelement direction finding antenna to a localized radiofrequency source. The error between the indicated and true bearing is evaluated and illustrated by graphs. It is also shown that the additional error, introduced by bringing the source into proximity of the antenna system is negligible if the antennasource distance is greater than . This is an important consideration in the calibration of the system. View full abstract»

24. Investigation of a surfacewave line for long distance transmission
Publication Year: 1952 , Page(s): 263  267
Cited by: Papers (1)First Page of the ArticleView full abstract» 
25. An organpipe scanner
Publication Year: 1952 , Page(s): 113  122In designing many scanning antennas, it is desirable to move a feed horn for an objective, a lens, or a reflector, along a curve on the focal surface of the objective. The most direct way to solve this problem is to move a horn on the desired curve mechanically; however, there are mechanical and electrical problems inherent in this type scanner which one would like to avoid. Another approach is the use of a simple mechanical motion, such as a rotation, which could be transformed into an apparent motion along the desired curve. Organ pipes use this approach, they usually consist of a structure for propagating energy from a feed horn through a transition region of waveguide channels to a radiating aperture. By rotating some part of this structure, different portions of the aperture are used, and hence the apparent motion along the line occupied by the aperture, or scanning, is accomplished. View full abstract»

26. Polarization switch and universal horn
Publication Year: 1952 , Page(s): 135  147The desirability of obtaining a radiating structure such that the polarization of the radiating energy could be varied in a controlled manner and yet provide a radiation pattern whose shape was invariant, led to the investigation which is the subject of this paper. View full abstract»

27. The effect of particle shape and composition on microwave attenuation and scattering by precipitation
Publication Year: 1952 , Page(s): 180  185First Page of the ArticleView full abstract» 
28. Thickness effects in slots located in various positions in rectangular waveguide
Publication Year: 1952 , Page(s): 107Theoretical expressions for the equivalent circuit parameters of slots of finite Ã‚Â¿ wall thickness are obtained in terms of the parameters of aerothickness slots of identical crosssection dimensions. The thick slots are treated as composite structures consisting of appropriate junctions and lengths of connecting waveguide, and the parameters of the junctions are determined from those of corresponding zerothickness slots. The latter parameters have been developed in previous work by our group. The thick slots considered include transverse slots coupling identical guides, transverse slots radiating from the end of the guide, slotcoupled Eplane Tees, and slots radiating from the broad face of the guide. Precision measurements have been taken at a wavelength of 3.2 cm as a function of nail thickness, and excellent agreement is obtained with the theoretical predictions. View full abstract»

29. Refraction of radio waves in arbitrary atmosphereraytracing picture
Publication Year: 1952 , Page(s): 36A development following Hartree, etc., is carried out of ray tracing using REAC differential analyzer. Ray families, on 2kinch by 32inch paper, are obtained for an atmosphere with a single n profile (index of refraction versus altitude curve), and for an atmosphere with three n profiles over the region of interest. The n profiles used were measured up to 10,000foot altitude. The variation in radio field strength with separation between airplanes as measured in a recent airtoair propagation flight is correlated with a variation or ray density based on index of refraction data taken during the flight. This was a flight which encountered a radio hole followed by its antihole (region of erulanced and interfering signals) within the geometrical horizon, and then a second hole and antihole at an anomalously large range beyond the horizon. The second antihole is accounted for by an anomalousranee layer near the ground and one in which the refractive gradient has a negative value nearly equal to l/(radius of earth}. In some respects the correlation is striking between raytracing picture and observed radio data. View full abstract»

30. The effect of radar wavelength on meteor echo rate
Publication Year: 1953 , Page(s): 37  42
Cited by: Papers (6)A new theory is given for the way in which the number of echoes received from sporadic meteor ionization trails varies with radar wavelength and other system parameters. Previouslypublished explanations of the echo rate dependence on wavelength are critically examined. The present explanation of echo rate variations is based upon a more complete analysis of the radio reflection process than is afforded by the LovellClegg theory. The effects of high electron density, the linear rate of trail formation, and the initial column radius are discussed. A number of apparent conflicts in earlier investigations are reconciled by the new theory. View full abstract»

31. Distant radio communication theory
Publication Year: 1952 , Page(s): 212
Cited by: Papers (2)Distant radio communication at high frequencies is difficult because the transmission medium, the earth ionosphere duct, is time variable, noisy, and shows dispersive or multipath transmission with consequent fading of the received signal. Because most of these factors are random and not under design control, one can treat the ionospheric communication problem only on a statistical basis in terms, for example, of such things as the probability that a transmitted pulse or bit of information will be received correctly. On this basis it is shown that, by a purely numerical experiment wherein random number tables are used to simulate fading and noise, it is possible to appraise various telegraph transmission systems without the costly process of building them and then testing their performance. An approximate, but simple, analysis is given of receiver signal detection, by which is meant generation of dc for operation of an output printing device. It is shown that the important parameter here is the average or expectation of the difference in dc between a received space and mark signal, divided by the square root of the variance of this difference. Incoherent square law detection is compared with coherent detection using the matched filter or, what is the same thing, correlation. The use of diversity transmission to overcome signal fading at the receiver is considered. The important statistical data regarding timevarying ionospheric transmission are obtained from the auto and crosscorrelation functions of the received signal envelopes for the various diversities. For the correlated fading of signal s in two transmission channels, a simple de sign formula is shown which predicts the improvement in the use of diversity. A brief description is also given of a simple acoustic ionosphere analog simulating timevarying multipath transmission. View full abstract»

32. An experimental investigation of the singlewire transmission line
Publication Year: 1954 , Page(s): 46  56
Cited by: Papers (3)The results of some measurements made on a dielectric coated wire are presented and compared with theoretical results. These measurements indicate that the singlewire line can be considered as a simple transmission line provided account is taken of the "endeffect." View full abstract»

33. Factors affecting the performance of linear arrays
Publication Year: 1952 , Page(s): 85  106The primary problem in the design of antennaarrays is the satisfaction of the requirements of sidelobe level and beamwidth. An additional major consideration which has only recently received an analytical treatment1 is the problem of the deterioration of the beamwidth and sidelobe level arising from the variations in the excitation of each element. These variations are due primarily to the inaccuracies inherent in the manufacturing processes used to produce the array. The first problem has been discussed in great detail by many authors,2 and it will be the purpose of this paper to analyze the second problem. The analysis is formulated in general for a symmetrically excited broadside array and then, as a specific example, is applied to a linear shunt slot array which uses a DolphTchebyscheff3 distribution for the element excitations. This distribution optimizes the relationship between beam width and sidelobe level. However, the method of analysis is general and may be applied to any linear array of radiators with arbitrary excitation, if the total mutual coupling between individual radiators may be neglected and no cross correlation exists between the inaccuracies of any two sources. Consideration will be given to these fundamental assumptions to show that the general method will yield useful results for slot arrays. View full abstract»

34. Modified magic tee phaseshifter
Publication Year: 1952 , Page(s): 126  134A magic tee may be used as a microwave phaseshifter by placing adjustable short circuits in its symmetrical arms. A perfect impedance match will exist through the E and Hplane arms if the distances from the shortcircuits to the tee junction differ by (2n + 1)Ã‚Â¿ g/4. The phase is shifted by simultaneously varying the distances from the short circuits to the tee junction. Orienting the symmetrical arms parallel to each other and replacing the E and Hplane arms by coupling slots on opposite sides of the stucture simplifies the shortcircuit driving mechanism and allows cascading of several phaseshifters. This modification is useful as a precision laboratory phaseshifter and allows the construction of a wideangle scanning array. View full abstract»

35. Theory of radio reflections from electronion clouds
Publication Year: 1955 , Page(s): 32  39
Cited by: Papers (17)Approximations to the reflection coefficients of electronion clouds of various sizes, shapes, and densities are determined. A simplified approach to the problem is employed, wherein the total reflection from the lowdensity clouds is computed by Summing the scattered wavelets from the individual electrons, while the highdensity clouds are treated as total reflectors at the critical density radius. Some of the limitations of this method are discussed. While more elaborate determinations should be used in certain regions of cloud size and density, the method used here provides an overall, firstorder approximation of the effects of size, shape, and density on the reflecting properties of electronion clouds. Several possible applications of the theoretical results are outlined. View full abstract»

36. Symmetrical waveguide junctions
Publication Year: 1952 , Page(s): 106Dicke and Kerns have shown that from a knowledge of the geometrical symmetry of a junction one can deduce the form of the scattering matrix. The synthesis problem; given a desired scattering matrix, to determine whether it is physically realizable in a symmetrical structure, and to find the possible structures, has not been solved completely, although several useful things can be said about the general problem. However, the number of cases that are ever likely to arise in practice is finite, and by solving the analysis problem for each of them and tabulating the results we have effectively given a "bruteforce" solution of the synthesis problem for junctions of six or fewer waveguides. View full abstract»

37. A further study of the patterns of single slots on circular conducting cylinders
Publication Year: 1952 , Page(s): 240  250
Cited by: Papers (1)The azimuthal patterns of both axial and circumferential slots on circular conducting cylinders have been carefully calculated in both magnitude and phase and some experimental checks have been obtained. The calculated patterns show that in the semicircle over which the slot is optically visible, the magnitude, and particularly the phase, of the patterns, are very similar to those, of a similarly situated slot in an infinite ground plane. This conclusion has significant implications in the design of an antenna involving several slots on a cylinder. On the semicircle over which the slot is optically invisible, and partioularly near the midpoint of this range, the pattern is very well represented by where is the value of the pattern at (the point opposite the slot) and is complex. Thus the field of either one of the rear quadrants resembles the voltage of an opencircuited lossy transmission line. The implications of the abovenoted form of the field pattern behind the slot led to the consideration of an expression for the field which is quite different from the usual one originally employed. By an exact transformation of the usual expression it is possible to show that the far field is given by the expansion , where is complex. Near , the first term of this series is dominant, and the results of this approach agree with those noted above. The procedure and its significance are quite closely related to the problem of electromagnetic wave propagation over a sphere, which has been of considerable interest for some time. The various aspects of the cylindrical problem are discussed in some detail. View full abstract»

38. UHF omnidirectional antenna systems for large aircraft
Publication Year: 1954 , Page(s): 6  15
Cited by: Papers (1)This paper discusses the problem of obtaining omnidirectional coverage from antennas operating between 1,000 and 3,000 megacycles on large aircraft. Electromagnetic modeling was used to determine the limitations of several single antenna sites on typical commercial aircraft. Considering all azimuth angles and in elevation to be equally important, the best coverage obtainable from a single radiator is equivalent to the radiation from a freespace dipole for 50 per cent of the time. To improve this, dual antenna systems must be used. Dual antenna requirements depend on whether or not the airborne equipments know when they should be receiving a signal. The distancemeasuring equipment (DME) is a typical system that knows when it should be receiving a signal, while radar safety beacon equipment does not know when or from what direction it is being interrogated. Direct parallel feed, the least complicated method of operating dual antennas, allows simple hybrid multiplexing to be used. With this type of operation interference occurs where the individual patterns overlap. Performance in this region is investigated on a probability basis for beacon operation and found favorable; for DME this region is uncertain. In addition, performance is predicted when the RF voltage in one of the dual antennas is (a) shifted periodically in phase, (b) delayed, and (c) interrupted periodically. Considerations involved in an antenna system common to DME and beacon are discussed. View full abstract»

39. A statistical survey of atmospheric indexofrefraction variation
Publication Year: 1953 , Page(s): 43  46
Cited by: Papers (6)This paper presents a statistical survey of indexofrefraction variations as recorded by an airborne microwave refractometer. Scales and intensities of the index variations are given, as well as the parameter , for data taken over southwest Ohio during summer months and over the Pacific Ocean off the west coast of Washington in August and of California in October. Heights from 2,000 to 25,000 feet, msl, were considered with most of the data taken between 2,000 and 12,000 feet. Approximately 1,200 samples taken on 34 flights were analysed. The composite of the data gave the following median values: Index Scale = 130 feet Index Intensity = /ft View full abstract»

40. Arrays of closelyspaced nonresonant slots
Publication Year: 1954 , Page(s): 109  113
Cited by: Papers (5)Slots laid broadside to each other exhibit mutual coupling of such magnitude that the design of practical linear arrays of such slots has hitherto been difficult, if not impossible. The technique presented here will produce arrays capable of generating pencil beams or shaped beams with controllable sidelobe level. A large number of slots per wavelength are used and the mutualcoupling effects are kept small by making the slots short compared to a half wavelength. Tests have shown that these arrays may be placed side by side without interaction, thus making it possible to construct a twodimensional array. View full abstract»

41. The dielectric properties of ice and snow at 3.2 centimetres as related to the reflection coefficient of snowcovered surfaces
Publication Year: 1952 , Page(s): 39A study has been made of the reflecting properties of snow and icecovered surfaces at a wavelength of 3.2 centimeters. In making this study, two lines of investigation have been followed. In one, controlled laboratory measurements were made of the permittivity and loss tangent of ice and snow of varying density and crystal structure over the temperature range 0?? to ??20?? C, using waveguide techniques. In the other investigation, direct measurements were made, on an outdoor range, of the reflection coefficients of a flat metallic surface covered with snow. View full abstract»

42. A singlecontrol tuning circuit for electrically small antennas
Publication Year: 1955 , Page(s): 12  15
Cited by: Papers (2)It is often desirable to tune electrically small antennas at their feed terminals. An "L" matching circuit for this purpose is considered. It is shown that one fixed element and one variable tuning element are adequate for certain small antennas. The manner in which losses affect the circuit effiiciency and the singlecontrol tuning feature is discussed. Application of the technique to a tunable cavity antenna is noted. View full abstract»

43. The geometrical optics field at a caustic
Publication Year: 1952 , Page(s): 262The asymptotic expansion of a wave field in powers of , where is the wave number, for large k has as its lowest order term what is commonly known as the geometrical optics field. The caustics of geometrical optics are those point sets on which the zero order teen becomes infinite. It is well known that caustics may exist even where the exact wave field is perfectly regular. An investigation of reflection from cylindrical walls of arbitrary cross section shows that the occurrence of caustic points means a change in character of the asymptotic expansion of the true field such that the lowest order term is no longer independent of , but actually contains a factor raised to a positive power. There also occurs a Jump in phase along a ray passing through a caustic which, as is well known, equals in the case of a focal point, but which may differ from in the case of more general types of caustics. In addition, the geometric optics field is worked out in detail for the case of a plane wave incident on a parabolic cylinder, and the field is obtained in its lowest order at the focus and in the neighborhood of the focus. View full abstract»
Aims & Scope
This Transactions ceased publication in 1955. The current retited publication is IEEE Transactions on Antennas and Propagation.
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ISSN:
21680639
Subjects
 Fields, Waves & Electromagnetics