Large Current Radiators Research Articles

FOCUSING PROPERTIES OF ULTRA WIDEBAND TRANSIENT ARRAYS

Some new focusing properties of time-domain ultra wide band (UWB) focusing array antennas are presented. The large current radiator (LCR) is considered as the UWB antenna element. Each LCR is replaced by a set of inflnitesimal dipoles modeling both the near fleld and the far fleld patterns of the antenna element, as well as the coupling between the elements. Several antenna arrays with difierent sizes and numbers of elements are modeled. It is shown that similar to narrow band antennas, the actual maximum fleld region shifts from the intended focus region towards the antenna aperture.

Use of the Coupling Between Elements of the Vertical Antenna Array of LCRs to Gain Radiation Efficiency for UWB Pulses

The inductance of large current radiators (LCRs) can be reduced by stacking several of them as a vertical array. The reduced inductance permits a shorter rise time for the driving current. Both theory and experimental data show that the radiated field strengths are increased considerably for a fixed, small driving voltage.

Large current radiator with S-diode switch

A large-current radiator (LCR) for the radiation of nonsinusoidal electromagnetic (EM) pulses with duration in the nanosecond range was developed. The time variation of the radiated electric field strength resembles one period of a sinusoid with the peak amplitude of the first half cycle being 1.2 times as large as the peak amplitude of the second half cycle. The duration of the first half cycle measured at one half the peak amplitude is 1 ns while the duration of the whole signal is 3.5 ns. The peak amplitude of the electric field strength at a distance of 3 m from the radiator is 56 V/m.

Correction to "Large-current Radiator With Avalanche Transistor Switch"

Correction to "Large-current Radiator With Avalanche Transistor Switch"

Large-current radiator with avalanche transistor switch

The development and experimental investigation of a large-current radiator (LCR) with a pulse generator using avalanche transistors is reported. The LCR is intend for radiating nonsinusoidal pulse electromagnetic waves with a duration of 2 ns. The radiated field strengths in both the near and the far field are measured. The LCR described produces magnetic field strengths of about 4.2 mA/m at a distance of 5 m for radiator current amplitudes of about 0.7 A with rise time of 1 ns. The width of the antenna pattern, measured by the drop of the field strength to one half of its peak value is 120/spl deg/.

Large-current radiators

One of the most important tasks for the practical use of nonsinusoidal waves in radar is the design of radiators. Just like resonating radiators for sinusoidal waves, they must efficiently transform a driving current and voltage into electromagnetic waves. However, in addition, the distortions caused by the buildup and decay of the energy stored in the near zone must be avoided, a task not required of the radiators of steady-state sinusoidal waves.

Magnetic Lines of Force of a Large-Current Radiator

The radiation of electromagnetic waves from a large-current radiator with a nonsinusoidal current is investigated in terms of constant magnetic flux called lines of force. The magnetic flux of a large-current radiator is a function of the time variation of the current along with the time variation of its integral and derivative, the distance from the radiator, and the geometry and dimensions of the radiator. In the near zone, the magnetic flux depends on the time variation of the integral of the current, the distance from the radiator, and a parameter that is a function of radiator dimensions. The magnetic flux depends on the azimuth angle due to the asymmetry of the radiator around its vertical axis. Plots of lines of force for two time variations of nonsinusoidal currents at various observation times are presented for a large-current radiator with dimensions 8d x d x 8d.

Power Flowing through the Surface of a Large-Current Radiator

A previously developed theory permitted us to calculate the electric and magnetic field strength produced by a current with arbitrary time variation flowing in a large-current radiator for any distance from the surface of the radiator to infinity. This permits one to determine Poynting's vector on the surface of the radiator and, by integrating it over the surface, to calculate the power flowing through the surface of the radiator at any time. One obtains the power radiated to the far zone, the power contained in the various near-zone components, and the required driving voltage. The influence of the antenna dimensions on these quantities may be studied to help with the design of better antennas.

Analysis of electric quadrupole radiation in the time domain: application to large-current radiators

ABSTRACT In this paper, the fields created by a hertzian electric quadrupole fed by a non-sinusoidal signal are analysed in the time domain. The results are compared with those obtained for an electric dipole and are applied to the study of the field created by the practical antenna, the large-current radiator.

Radiation of Nonsinusoidal Waves by a Large-Current Radiator

The calculation of the electric and magnetic field strength produced by a radiator is usually done only for distances large compared with the geometric dimensions of the radiator. This approach makes it Impossible to obtain exact relations between the power fed to the radiator by the driver, the voltage between the radiator terminals, the power radiated to or received from the near zone, and the power radiated to the far zone. This paper develops a solution for the large-current radiator that can be evaluated numerically by computer for any distance, and thus permits the calculation of the power flowing at any time through the surface of the radiator. The knowledge of this power is the basis for the design of efficient radiators.

Some thoughts about the radiation of antennas excited by non-sinusoidal currents

Abstract In this paper, general expressions for the fields produced by an arbitrarily variable charge and current distribution are derived in the time domain. The results are compared with those obtained by Fourier analysis. Starting from these results, the non-sinusoidal fields produced by the basic large-current radiator when fed by different excitation currents, are analysed

Antennas for Nonsinusoidal Waves: Part: III-Arrays

In the previous two papers, we discussed the Hertzian electric dipole and the large-current radiator, used either as radiators or sensors. Several radiators or sensors can be combined into an array. In the case of sinusoidal waves, such an array would yield more power and a directional pattern of the power called the antenna power pattern. For nonsinusoidal waves, one obtains additional patterns. In the particular case of a time variation of the electric and magnetic field strengths equal to that of a rectangular pulse, one obtains an antenna slope pattern caused by the change of the time variation of the field strengths as functions of azimuth and elevation angles. This change is often called a distortion, but in reality it provides us with additional information for the angular resolution. Sinusoidal waves cannot provide this information due to their lack of a bandwidth. This paper investigates both the regular sensor array using the sum of all sensor outputs, and the monopulse array that uses the difference between the sums of the sensor outputs of the right and the left halves of the array. Radiator and sensor arrays for nonsinusoidal waves have been built at least since 1975, but the circuits required for the utilization of the slope patterns are still at the frontier of our technology for pulse durations in the order of 1 to 0.1 ns, which are primarily of interest.