IEEE Transactions on Antennas and Propagation

In this paper, we derive the characteristic equation for the complex propagation constant in a transmission line periodically loaded with dipole elements. This equation is solved for real and imaginary parts of the mode propagation constants. The effect of mutual impedance between antenna elements is included in the formulation and calculation. Theoretical calculations are compared with experiment... View full abstract»

The electromagnetic field in the focal plane of a finite axially-symmetrical paraboloidal reflector illuminated by a plane wave of arbitrary polarization incident nearly normally at the vertex, has been investigated. This paper describes the investigation, explains the method, and summarizes some of its results. The reflector is assumed to be of a focal length which is large compared with the wave... View full abstract»

Experimental measurements have been made of the nose-on backscattering radar cross section over a range of diameters from 0.05 to 1.0 wavelengths of a series of ogives with total included nose angles of40deg,75deg, and120deg; of cone spheres with nose angles of15deg,30deg,40deg60degand120deg; of double-rounded ... View full abstract»

A mathematical model for microwave backscatter from the sea at near-vertical incidence is presented. The model, which is formulated in terms of Huygens principle, expresses the backscatter in terms of an "expected transfer function" of the round-trip path between the antenna and the surface of the sea. In its present form, the model is restricted to describing the case in which the microwave-illum... View full abstract»

Several commonly-used approximations of the transmission coefficient of a uniform plasma slab are critically examined and compared with a new approximation developed in this paper. It is shown that the new approximation, in addition to being very suitable for use on digital computers, gives much higher accuracy than any other for most useful values of plasma and collision frequencies. Regions of v... View full abstract»

A formula for the impedance of a short cylindrical dipole in a magnetoplasma is derived using quasi-static electromagnetic theory. The formula is valid in a lossy plasma and for any dipole orientation with respect to the magnetic field. The dipole impedance is found to have a positive real part under lossless conditions when the quasi-static differential equation is hyperbolic; this indicates that... View full abstract»

An automatic gain control system for stabilizing the gain of microwave radiometers is described. System analysis sets forth the requirements for gain and bandwidth of the AGC loop. Two systems are described. One is a continuous AGC system that maintains a constant detector voltage and, as a result, the system gain is a function of the input signal. For input signals which are small compared to the... View full abstract»

Exact calculations are made of the electromagnetic field radiated by an arbitrary current distribution in an arbitrary stratified lossy medium. The medium thus characterized can include both a stratified earth and a many layer stratified ionosphere. The results of the investigation, which include the input resistance and the efficiency of the antenna, are useful for designing antennas in the ELF, ... View full abstract»

The amplitude and phase of a radio ground wave are calculated for an oblique crossing of a flat-lying coast line. The surface impedance is allowed to change in a continuous and gradual manner in the vicinity of the coast line. The earlier results for an abrupt boundary are recovered as the width of the transition zone is reduced to zero. In general, it is found that the presence of the transition ... View full abstract»

The properties of electric and magnetic probes for the measurement of transient electromagnetic fields in air and in dissipative media are discussed briefly. It is shown that the effective height of an electrically small loop is independent of the ambient medium. This is also virtually true for a thin electrically short dipole (or monopole). If the open-circuit voltage of a magnetic probe can be m... View full abstract»

A theoretical and experimental study of the minimization of the back scattering by a thin cylinder by central loading is presented. The induced current on a centrally loaded cylinder illuminated by a plane wave at normal incidence was determined theoretically and experimentally. The magnitude and phase of the induced current can be greatly changed by a central impedance. The optimum loading to ach... View full abstract»

When an electromagnetic source confined in a homogeneous, anisotropic plasma half space radiates into the exterior medium, focusing effects may occur wherein the influence of the plane interface bounding the plasma is similar to that of an optical lens. The existence and location of the caustics and focus depends on the various plasma parameters, in particular on the strength and orientation of th... View full abstract»

Greater insight into the resolution and accuracy, as well as the data processing, of an interferometer radar is obtained in this partly tutoral paper by the examination of the multidimensional ambiguity function. Two approaches are used for determining the multidimensional ambiguity function. First, it is determined by the classical and more standard procedure in which the signals at the target an... View full abstract»