A. M. Efremov

High-power ultrawideband radiation source

The article presents a source producing high-power ultrawideband electromagnetic pulses. The source includes a generator of monopolar pulses, a bipolar pulse former, and a combined ultrawideband transmitting antenna. Monopolar 150-kV, 4.5-ns pulses are transformed into bipolar 120-kV, 1-ns pulses, which are emitted by the antenna. The pulse repetition rate of the setup is up to 100 Hz. The peak power of the source is 170 MW as measured with a TEM-type receiving antenna having 0.2-2 GHz passband. The pattern width of the transmitting antenna at a half-level of peak power is 90° and 105° for the H- and E-planes, respectively. The electric field strength measured 4 m from the transmitting antenna in the direction of the main radiation maximum is 34 kV/m.

High-power ultrawideband electromagnetic pulse radiation

Basing on energetic processes studying in the near-field radiator zone, a new concept of antenna synthesizing for ultrawideband electromagnetic pulse radiation has been suggested. The results of experimental investigations of the antennae developed with using of this concept for high-power applications are presented. The antennae have small dimensions, high electrical strength, cardioid pattern with linear polarization of the pulse radiated and they are ideally adapted to be used as a steering antenna array element. A high-voltage nanosecond bipolar pulse generator design to excite antennae is described.

High-power sources of ultra-wideband radiation with subnanosecond pulse lengths

Sources of high-power ultra-wideband electromagnetic pulses of nanosecond duration are described. A bipolar voltage pulse with a length of 0.5 ns and an amplitude of ∼200 kV is fed to the input of a radiating system (a 16-element array antenna or a single antenna). The values of the effective radiation potential EpR = 260 kV for a source with a single antenna and EpR = 690 kV for a source with a 16-element antenna array were obtained at a pulse repetition frequency of 100 Hz.

Generation and emission of high-power ultrabroadband picosecond pulses

The generation and emission of high-power ultrabroadband electromagnetic pulses are studied. The possibility of high-voltage (about 100 kV) bipolar voltage pulses with a duration of about 200 ps is demonstrated. The electromagnetic pulses with a FWHM of less than 100 ps, an effective potential of up to 400 kV, and a repetition rate of 100 Hz are generated using the 16-element antenna array.

A source of high-power pulses of elliptically polarized ultrawideband radiation.

Here, we describe a source of high-power ultrawideband radiation with elliptical polarization. The source consisting of a monopolar pulse generator, a bipolar pulse former, and a helical antenna placed into a radioparent container may be used in tests for electromagnetic compatibility. In the source, the helical antenna with the number of turns N = 4 is excited with a high-voltage bipolar pulse. Preliminary, we examined helical antennas at a low-voltage source aiming to select an optimal N and to estimate a radiation center position and boundary of a far-field zone. Finally, characteristics of the source in the operating mode at a pulse repetition rate of 100 Hz are presented in the paper as well. Energy efficiency of the antenna is 0.75 at the axial ratio equal to 1.3. The effective potential of radiation of the source at the voltage amplitudes of the bipolar pulse generator equal to -175/+200 kV reaches 280 kV.

A four-channel source of high-power pulses of ultrawideband radiation

A source of nanosecond ultrawideband radiation is described. Four output bipolar pulses from the source can be synchronized with an rms deviation of less than 100 ps in the time of the voltage passage through zero or delayed by the moment of this passage in some pulse formers relative to other ones by a time of up to 300 ps using the pressure control in two-electrode discharge switches. At a 3-ns bipolar-pulse length, the obtained values of the effective potential of radiation at a pulse repetition rate of 100 Hz were 400 kV. The possibility of the wave-beam steering within limits of 12° was demonstrated.

High-power ultrawideband electromagnetic pulse source

The source of high-power ultrawideband (UWB) radiation based on single compact antenna excited with 1-ns bipolar pulse has been created. Antenna input pulse amplitude is up to 120-kV and pulse repetition rate up to 100 Hz. The antenna efficiency by peak power was 60%. The peak power of the source was 170 MW. The antenna pattern width by half-power is 100/spl deg/ for the H-plane and 105/spl deg/ for the E-plane. The efficient voltage of the source equal to product of the peak field strength and the distance made /spl sim/130 kV.

A low-impedance high-voltage bipolar pulse former

The results on the formation of bipolar pulses with amplitudes of up to 100 kV, a duration of 2 ns, and a pulse repetition rate of 100 Hz across a 12.5-Ω load are presented. Lines with a characteristic impedance of 6.25 Ω were switched using multichannel ring switches with 70-mm-diameter electrodes in a nitrogen medium at a pressure of 40–60 atm. At a pressure of 40 atm, the rms deviation of the operation time of the sharpening switch reaches 40 ps at a voltage-pulse rise rate of 7 × 1013 V/s at the electrodes. As the pressure increases, the stability of the output bipolar pulses deteriorates; this is probably associated with a disturbance of the multichannel-switching mode in the sharpening switch. The performed simulation of the pulse-former operation showed that the energy loss in the switches reaches 40% of the stored energy in the output line of the Sinus-160 generator.

Emission of High-Power Ultrawideband Elliptically Polarized Pulsed Radiation by a Cylindrical Helical Antenna

Ultrawideband elliptically polarized radiation is numerically and experimentally studied. The analysis is performed for the axial radiation of a cylindrical helical antenna that is excited by a bipolar voltage pulse with a duration of 2 ns. The results are used for construction of a source of high-power ultrawideband pulses with elliptical polarization. The radiation pulses with an effective potential of 300 kV are generated at an amplitude of the bipolar voltage pulse of 200 kV and a repetition rate of 100 Hz.

Radiation of High-power Ultrawideband Pulses with Elliptical Polarization by a Conical Helical Antenna

A high-power source of ultrawideband radiation with elliptical polarization was developed on the basis of exciting a conical helical antenna by a bipolar voltage pulse with a length of 1 ns. The antenna parameters were preliminarily estimated using analytical formulas and then optimized via numerical simulation. The results of low-voltage test measurements were compared with the data that were obtained using a program that was developed on the basis of the finite-difference method in the time domain. In high-voltage measurements, the energy efficiency of the radiator was 0.85 and the coefficient of the hodograph ellipticity measured along the antenna axis was 0.9. The effective radiation potential of the source at an amplitude of bipolar voltage pulses of 190 kV was 270 kV, while the efficiency with respect to the peak field strength was 1.35. The high-power source of ultrawideband radiation operated at a pulse repetition frequency of 100 Hz.