Popular Articles (January 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. A new antenna feed having equal E and Hplane patterns
Publication Year: 1954 , Page(s): 113  119
Cited by: Papers (26)  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. 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»

4. 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»

5. 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»

6. 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»

7. 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»

8. 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»

9. A twodimensional microwave luneberg lens
Publication Year: 1953 , Page(s): 12  23
Cited by: Papers (12)  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» 
10. On spherically symmetric lenses
Publication Year: 1952 , Page(s): 66  71
Cited by: Papers (7)First Page of the ArticleView 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. A broadband microwave quarterwave plate
Publication Year: 1952 , Page(s): 123  125A differential phase shift between two orthogonal TE11 waves in circular hollow waveguide may be achieved with capacitive pins which affect one mode and not the other. Representing the two modes in the guide by two equivalent transmission lines and the pins by shunt susceptances, an analysis of an array of pins may be made to determine, as a function of pin spacing, the required values of susceptance to produce a given phase shift Â¿ with no reflection. By making use of the transmission matrix giving voltage and current at one point in terms of voltage, and current at another point on the line, the following formulas for a threeelement array are derived: View full abstract»

13. 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»

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. Nodal shift impedance measurements in periodic waveguides
Publication Year: 1952 , Page(s): 106The nodal shift method of measuring the properties of a Coupling system connecting two transmission lines is a convenient and accurate method which does not require the existence of good terminations to match the lines. Using a generalized definition of impedance in a periodically loaded waveguide, such as is encountered in the Stanford linear accelerator or in travelingwave tubes, this technique can be extended to determining the properties of a coupling system connected between a smooth waveguide and the periodic one, and when these are known, one can measure impedances in the periodic structure by observing those in the smooth guide. In addition, this impedance relation permits one to deduce the phaseshift constant of the structure at any frequency in the passband. View full abstract»

16. 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»

17. 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»

18. An exact stepup impedanceratio chart of a folded antenna
Publication Year: 1954 , Page(s): 163
Cited by: Papers (4)First Page of the ArticleView full abstract» 
19. 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» 
20. The zero phasefront in microwave optics
Publication Year: 1952 , Page(s): 38  41Many microwave optical devices have been designed and studied, at least in part, by the methods of geometrical optics. Common practice in the microwave field has been to focus attention on the family of rays rather than on the surfaces normal to them, the socalled phasefronts. When phasefronts are examined, they are usually obtained from the rays by passing along each ray a constant electrical distance from a reference phasefront. The clumsy analytical expression for a phasefront thus obtained renders even a routine investigation of it a burdensome exercise in mathematical manipulation. View full abstract»

21. 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»

22. Antenna pattern calculation for asymmetrical aperture distributions
Publication Year: 1952 , Page(s): 60  62
Cited by: Papers (1)A method is presented for calculating the radiation patterns and gain of antennas having asymmetrical phase and amplitude distributions. This method, which determines the radiation pattern from the actual distribution across the aperture, makes use of automatic punch card machines to perform a numerical integration. The patterns obtained for several distributions are discussed for amplitude and phase asymmetry considered both separately and in combination. Results are given for typical distributions obtained with asymmetrical parabolic cylinders. Applications to scanning antenna analysis and the determination of the phase of the radiated pattern are presented. View full abstract»

23. 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» 
24. 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»

25. 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»

26. 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»

27. 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»

28. 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»

29. Mutual impedance of stacked rhombic antennas
Publication Year: 1954 , Page(s): 39
Cited by: Papers (1)First Page of the ArticleView full abstract» 
30. 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»

31. Propagation characteristics of microwave optical links
Publication Year: 1952 , Page(s): 31  36
Cited by: Papers (1)The performance of pointtopoint microwave links is affected considerably by the nature of the terrain which the links traverse and the variable refractivity of the lower atmosphere due to changes in the local meteorological conditions. While a great deal of information is available on these two factors, it is in many cases difficult to predict with any degree of assurance the reliability to be expected on a microwave link installed on a given path. It is usually advisable to mke an experimental survey of propagation char"acteristics and siting factors involved on such a path. This paper describes the reslllts of an experimental propagation survey which was made on two paths in the San Frmcisco Bay (USA) area. View full abstract»

32. 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» 
33. 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»

34. 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»

35. A criticism of the Feinstein  Carroll theory of tropospheric propagation
Publication Year: 1952 , Page(s): 19This paper was withdrawn as being nonapplicable to Feinstein's paper in its present form. View full abstract»

36. Shortperiod skywave fading of CW emissions
Publication Year: 1952 , Page(s): 12  18A study of the shortperiod skywave fading of cw emissions shows that observed characteristics of these fading distributions are functions of the relative amplitudes of the received and magnetoionic components. When the received magnetoionic components are essentially equal at the receiving point, severe and rapid fading occurs and variations in shortperiod fading are maximum. However, when a single mode of propagation is suppressed, the variations in shortperiod fading distributions of the received field are reduced and become lognormal in character. A new parameter is suggested to replace the Rayleigh distribution in cases where a more accurate formulation of shortperiod fading characteristics is desired. Finally, a description is given of a practical method of emitting cw radio transmissions, which yields reflections from the ionosphere of a single ionospheric mode, thereby obtaining some manmade control over shortperiod skywave fading. View full abstract»

37. Transmission loss of space waves propagated over irregular terrain
Publication Year: 1952 , Page(s): 152  166
Cited by: Papers (3)First Page of the ArticleView full abstract» 
38. Application of the microwave homodyne
Publication Year: 1952 , Page(s): 110  116
Cited by: Papers (4)First Page of the ArticleView full abstract» 
39. 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»

40. The microwave measurement of variations in atmospheric refractive index
Publication Year: 1952 , Page(s): 74  78
Cited by: Papers (2)A microwave refractometer for measuring variations in atmospheric refractive index is described, and certain errors associated with the cavities are discussed. A preliminary account is given of observations obtained with two refractometers and other meteorological equipment installed on a 420foot tower. View full abstract»

41. The effects of ions on magnetoionic characteristic polarization
Publication Year: 1953 , Page(s): 23  27
Cited by: Papers (1)There is some evidence for the presence of large numbers of ions in the Eregion. Considering the recent increase in the precision with which skywave polarization measurements can be made, it seems desirable to flu a gap in the usual magnetoionic theory by investigating the effect on the theoretical characteristic polarizations of introducing a mixture of ions and electrons into the calculations. A general formula is derived as an extension of the magnetoionic polarization expression of Goubau. The 100 kc and 300 kc polarizations predicted by this formula have been plotted for a neutral mixture of oxygen ions, nitrogen ions, and electrons. The plots show that polarizations are possible in a mixture that cannot occur when only electrons are present. They also show that characteristic polarizations in a mixture do not define the medium parameters as completely as they do with electrons only. Another interesting feature is that the polarizations in a mixture depend on the relative numbers of each type of charged particle but seem not to depend on the actual charge density when the proportion of electrons is small. View full abstract»

42. 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»

43. A correlation computer and applications to radio propagation
Publication Year: 1952 , Page(s): 4  12Correlation functions of data, such as fading radio signals or temperatureand humidity fluctuations of the atmosphere, offer a powerful tool for analysis. By conventional methods, computation of these functions is long and tedious. Thi paper describes a computer which was constructed for this purpose. The data to be studied are transcribed onto magnetic tapes. These tapes are then run through a computer which computes the auto or crosscorrelation functions, and plots the resulting function through a recording meter. An example of the application of this computer to the study of the turbulence of the atmosphere is shown. View full abstract»

44. Strip transmission line study
Publication Year: 1952 , Page(s): 37A TEM transmission line having a circular or rectangular center conductor placed between two parallel plates or inside a rectangular tube, has been used in the construction of a number of uhf antennas and Â¿ wave filters. The characteristic impedance of the class of transmission lines, of which the abovementioned are particular examples, can be theoretically calculated by a number of methods. A review of the theoretical methods using the above transmission lines as examples will be given. Comparison between theoretical and measured results will be given to show the usefulness of the different theoretical methods. View full abstract»

45. 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»

46. A statistical approach to the problem of multiple radio interference to FM and television service
Publication Year: 1952 , Page(s): 43  49Since the received fields in the uhf and vhf bands vary Â¿ widely in time and space, it is believed that, on many occasions, a statistical approach to communication problems may be necessary. It is the purpose of this paper to present a statistical analysis of the problem of FM and television service in the presence of multiple sources of interference. View full abstract»

47. Sweep frequency backscatterSome observations and deductions
Publication Year: 1954 , Page(s): 56  63
Cited by: Papers (3)Sweepfrequency backscatter records have proved to be of great value in identifying the sources of backscatter seen on a fixed frequency by demonstrating the development of the echo as frequency and range increase. The most commonly observed scatter is ground scatter propagated via the F2 layer, but it is also evident that the other layers propagate ground scatter and that scatter from the distant E region may at times be important. In one group of observations over an 1,150km path on three undisturbed days, the values of F2layer maximum usable frequency scaled from midpoint verticalincidence ionospheric records and those determined by backscatter delay assuming ground scatter agreed almost within experimental error. In another threeday group characterized by a lowlatitude ionospheric disturbance with low geomagnetic indexes but considerable sporadic activity, values of muf determined from scatter were much too high under the groundscatter assumption, errors of about 30% being not uncommon. View full abstract»

48. VHF field intensities in the diffraction zone
Publication Year: 1954 , Page(s): 35  38For the past few years there has been a general interest in the mechanism of propagation of vhf waves in the diffraction zone. Several theories have been advanced which attempt to describe the phenomena quantitatively, however, most calculated results from these theories have yielded signal strengths several decibels below those obtained experimentally. This analysis follows the general procedure of obtaining a solution to the wave equation, subject to the appropriate boundary conditions. In obtaining this solution, it is necessary to make some assumption regarding the distribution of the refractive index as a function of the height above the surface of the earth. The essential difference between this solution and those previously presented is the form of this variation. An exponential form which approaches unity at large heights has been chosen. Using this distribution, an expression for the field strength as a function of separation between the transmitting and receiving antennas and the height of the antennas above the earth is obtained and signal strengths are calculated for comparison with measured values. View full abstract»

49. 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»

50. 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»
Aims & Scope
This Transactions ceased publication in 1955. The current retited publication is IEEE Transactions on Antennas and Propagation.