Popular Articles (February 2015)
Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
1. Design of linesource antennas for narrow beamwidth and low side lobes
Publication Year: 1955 , Page(s): 16  28
Cited by: Papers (126)  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. 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»

3. 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» 
4. 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»

5. 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»

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. Tracking noise measurements on a manual tracking radar
Publication Year: 1952 , Page(s): 135Tracking noise measurements have been made on a manual tracking, sectorscan radar, Methods have been devised to measure the operator's tracking error, which has been assumed to be the principal source of tracking noise. In tests made with an actual moving target, it is extremely difficult to distinguish between tracking errors and the true target motion. In order to measure error alone, a technique has been developed in which a fixed target is given, known artificial motion. In this manner tracking error can be recorded for various target courses and speeds. Rate tracking and aided tracking have been simulated to allow experimental determination of optimum values of such parameters as aided tracking time constant and control sensitivity. View full abstract»

8. Radiation from a vertical electric dipole over a stratified ground
Publication Year: 1953 , Page(s): 9  11
Cited by: Papers (9)Expressions for the radiation fields at low frequencies of a vertical electric dipole situated on a horizontally stratified ground are derived. It is indicated that the wellknown numerical results for the homogeneous ground can also be employed for ground wave propagation over a plane couductor composed of any number of parallel layers by suitably defining an "effective numerical distance." View full abstract»

9. 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»

10. Measurement of the effect of irregular terrain on VHF and UHF directive antenna patterns
Publication Year: 1952 , Page(s): 167  178
Cited by: Papers (4)Measurements of antenna patterns of directive antennas were made while driving around transmitters at relatively constant distances of 0.4, 10, and 30 miles. The transmitting antennas for pattern measurement were located at Fort Dix, N.J., and operated at frequencies of 49, 141.75, 239, and 460 mc. The receiving antennas used for recording were groundplane antennas mounted on a retractable mast in the mobile recording unit and could be operated as high as 30 feet, road obstacles permitting. Because of the great number of wires and trees over the road, most measurements were made at 12 and 15 feet. In addition to the measurements made around the transmitters, receiving antenna pattern measurements were made at spot locations around the transmitter with a 460mc corner reflector antenna. View full abstract»

11. Modes in waveguides containing ferrites
Publication Year: 1952 , Page(s): 104  105
Cited by: Papers (4)First Page of the ArticleView full abstract» 
12. Impedance measurement techniques for twomode guides
Publication Year: 1952 , Page(s): 148  152In this paper, work on Ã‚Â¿ which was partially supported by O.N.R. contract N7onr29529, the method of impedance measurements in singlemode guide is extended to twomode guide. Data is presented showing the impedance of a halfwave narrow slot placed parallel to the axis on the broad face of a rectangular waveguide supporting the TE10 and TE20 nodes. View full abstract»

13. 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»

14. 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»

15. 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» 
16. Multiple unit antennas, with skew
Publication Year: 1952 , Page(s): 136
Cited by: Papers (1)The number of antennas required to produce a satisfactory horizontal pattern around a relatively large support structure is reduced in a major degree by a new technique known as "skew". Calculated and measured patterns are discussed, comparing normal radiallydirected units and those with 90degree skew. The results with skew angles varying from 90 degrees down to zero are studied. The effects of progressive increase of structure size are shown. Variation with phasing is studied. A mathematical analysis is made for the purpose of disclosing the fundamental basis for pattern improvement by antennas mounted in a skewed relationship. View full abstract»

17. Publication pians of the professional group on antennas and propagation
Publication Year: 1952 , Page(s): 2  3The prompt exchange of information is vital to the progress of any branch of science, and especially so in rapidly changing branches such as antennas and propagation. In order to expedite the dissemination of information in these fields, the Professional Group on Antennas and Propagation is undertaking the periodic publication of groups of articles and reports of interest to the membership. In order to accomplish the objective of promptness of publication, it is planned to keep the editorial review of papers to a minimum, thus placing the responsibility for accuracy and completeness of material entirely on the author. View full abstract»

18. Quasistatic solution for diffraction of a plane electromagnetic wave by a small oblate spheroid
Publication Year: 1952 , Page(s): 13  36The problem of the diffraction of a plane electromagnetic wave by a small perfectly conducting oblate spheroid for the case of normal incidence has been investigated by an expansion method. By retaining three terms of the exponential function contained in the incident field, it is possible to describe both the incident field and the nearzone scattered field in terms of a finite number of discrete modes which satisfy the third order vector equation Ã‚Â¿ ÃƒÂ— (Ã‚Â¿2 A) = 0, where A denotes a solenoidal vector representing either the electric field or the magnetic field. When the eccentricity of the spheroid approaches zero, the general solution reduces to the exact solution for a small sphere. When the spheroid degenerates into a disk, the expressions for the charge and the current agree with the leading terms of the corresponding expressions obtained by Meixner, Andrejewski, and Bouwkamp. View full abstract»

19. VHF tropospheric recording measurements of plane and circular polarized waves in the great lakes area
Publication Year: 1952 , Page(s): 42To investigate the characteristics of circularlypolarized waves as propagated through the troposphere, a field recording station has been set up at Hudson, Ohio. Continuous field intensity recordings have been made of the horizontal and vertical components as well as the circularlypolarized field over a 125mile path from Columbus, Ohio. The results of these recordings are compared Ã‚Â¿ with recordings of the propagation of plane polarized waves over the same path, as wall as over the path from Detroit, Michigan, this latter path being about 50 per cent over water. A mobile recording survey has been conducted on a radial from Columbus through Hudson, and also on the circumference of a thirtymile radius around Colwdns. An analysis of this survey has been made showing the relationship betmen the horizontal and vertical components of the circularlypolarized field. lh addition, a comparison of the propagation data from Texas is made with the data obtained in this study. This cmparison sham marked daferences in the diurnal variation i n the two regions. This work has been performed under contract betmen the National Bureau of Standards and the mited Broadcasting Company. View full abstract»

20. 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»

21. 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»

22. 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»

23. 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»

24. 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»

25. Discussion on optimum patterns for endfire arrays
Publication Year: 1955 , Page(s): 40  43
Cited by: Papers (7)The method of synthesizing an equalminorlobe directivity pattern suggested by Riblet for the broadside array was applied recently by DuHamel to the case of the endfire array. In the present paper, an alternative synthesis procedure is described, based directly on Dolph's method of synthesis for the broadside array. Advantages of this alternative procedure include (a) applicability to arrays having even as well as odd numbers of elements, and (b) somewhat simpler equations for calculating relative currents for the elements of the array. This alternative procedure is described here in detail, together with numerical examples for the sevenelement array used by DuHamel and for a fourelement array. A tabulation of equations for relative current amplitudes for arrays of 5, 7, 9, 11, and 13 elements is given in an Appendix. In conclusion, an alternative method of overdesigning a supergain antenna is described. View full abstract»

26. On spherically symmetric lenses
Publication Year: 1952 , Page(s): 66  71
Cited by: Papers (7)First Page of the ArticleView full abstract» 
27. 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»

28. Scattersounding: A technique for study of the ionosphere at a distance
Publication Year: 1952 , Page(s): 186  201
Cited by: Papers (4)First Page of the ArticleView full abstract» 
29. 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»

30. 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»

31. Guided wave concept in electromagnetic theory
Publication Year: 1952 , Page(s): 231  239First Page of the ArticleView full abstract» 
32. The length of ionized meteor trails
Publication Year: 1952 , Page(s): 230
Cited by: Papers (4)By studying the rate of coincident detection of meteors at two widely separated locations, as a function of the differential time of first detection, it is possible to deduce the distribution in length of the meteoric ionization columns. A precise determination would require, in addition, that the velocity of the individual meteors used in the test be known. However, in the absence of such data, an approximate distribution of trail lengths whose mean value is probably representative of actual conditions, can still be deduced. For equipment generating about a kilowatt of continuous wave output, and capable of detecting meteors at a total rate of 450 meteors per hour, the mean trail length was found to be 25 or 30 km. Calculations based upon this value of trail length, and upon the use of a corrected rate of meteoric arrival, show that meteors up to the sixth magnitude were detected during the test. The method described provides a measure of trail length dependent upon the ability of the trail to reflect a signal at normal incidence. The accuracy of the determination of frequency of occurrence of trails of various lengths is independent of the rate of detection, but is proportional to the square root of the period of observation. View full abstract»

33. Regularities in the behavior of regions E and F of the ionosphere
Publication Year: 1952 , Page(s): 5This paper describes recent work by Ratcliffe on the regularities in the F2 region of the ionosphere, the results of which are in process of publication in the Journal of Geophysical Research, as well as a study of the phase path of echoes from Region E. The regularities in the behavior of the F2 layer are shown by using a simple method for analyzing routine (h',f) records which is similar to the graphical method of Booker and Seaton. Records from Watheroo, Huancayo, and College have been analyzed to determine the total number, ( ), of electrons below the level of maximum electron density in a column of unit cross section in the F2 region. This analysis shows that is closely related to the sun's zenith angle whereas the maximum electron density is not simply related to . The wellknown anomalies when is studied as a function of time of day, time of year, and geographical position all seem to disappear when n is studied instead of . An anomaly observed at Huancayo is discussed and a relation between thickness and height of the F2 layer which may be of use in ionospheric forecasting is described. The results of three years' observations of the phase of echoes of about 2 mc per second in frequency from Region E are described. These show that the phase height of the region varies qualitatively, but not quantitatively, as would be expected for a simple Chapman region. The effects of fadeouts in increasing the absorption and also the phase heights for echoes from the region are described and measurements are given of the velocities of movement of clouds of ionization in the lower part of the E layer. View full abstract»

34. 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»

35. Paraboloid reflector and hyperboloid lens antennas
Publication Year: 1954 , Page(s): 119  127
Cited by: Papers (18)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»

36. 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»
Aims & Scope
This Transactions ceased publication in 1955. The current retited publication is IEEE Transactions on Antennas and Propagation.