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Nowadays, beamless pulsed microwave generators are in a relatively wide use which, seemingly, can be attributed to their large breadth of emission spectrum, rugged structure and relatively low production costs.

However, since in those devices the broad emission spectrum is provided owing to excitation of the electrodynamic structures, or immediately antennas, by a small-width pulse (0.1-1 ns), then despite a high level of radiated pulsed power ~ 109 W, the radiation energy is low, not exceeding usually several joules. It is exactly this fact that imposes certain limitations on usage of those devices.

IEMR, Ltd. has developed several kinds of the beamless generators, namely those that employ excitation of the electrodynamic structures by high-pressure discharges and those based on excitation of the non-linear circuits that have lumped constants by powerful current pulses with a high steepness of the leading edge.

These devices are rugged structurally, enabling to produce high-peak power output levels at a relatively large breadth of the spectrum and a high stability of the shape of radiation pulse generated.

As an example of one type of our proprietary beamless generators, we shall give a brief description of a device enabling to produce single pulses or bursts of pulses generated. Its operation is based on the use of an H-type waveguide driven by large-current high-pressure gas-filled spark gaps.

	Fig. 1. General view of generator employing H-waveguide on experimental stand. 1 – H-waveguide with driver spark gap; 2 – Radiating horn; 3 – Anechoic chamber; 4 – Chamber-to-horn junction; 5 – HV delay line; 6 – Low-inductance storage capacitance; 7 – HV pulsed power supply.

This generator is viewed as an H-type waveguide (1) filled with refined transformer, or silicone, oil in order to prevent breakdowns during operation at high-power levels. The waveguide is driven by one or two (with a certain delay) gas-filled high-pressure spark gaps upon triggering them off with an HV-pulse with an amplitude up to 400 kV that comes from the high-voltage low-inductance storage capacitance (6). The spark gaps which are filled up with SF⁶ , or a mixture of SF⁶ with N² , can be set off either one-by-one, or with a certain delay relative to each other, as introduced by the high-voltage delay line (5). An adjustable high-voltage supply of the transformer type allowing to produce pulses with an amplitude up to 420 kV is used as charging source for the low-inductance capacitance. The use of this high-voltage transformer makes for a very compact voltage source.

Fig. 2 gives an oscillogram of radiated pulse from this generator in the mode of operation of driving the H-waveguide by two spark gaps in that event when the actuation time of one is delayed in relation to the other.

	Fig. 2. Oscillogram of radiated pulse in the mode of generation of a burst of pulses driven by two spark gaps with delay.

Fig. 3 presents an oscillogram of emission from the generator upon driving the H-waveguide with one spark gap. In this case, single pulses are produced.

	Fig. 3. Oscillogram of emission from generator in the mode of production of single pulses of radiation.

As one can see from the above oscillograms, during simultaneous actuation of two spark gaps a burst of pulses with long widths is generated, the radiated power being, however, considerably lower, as compared with the case of one spark gap excitation when a single pulse is radiated. This phenomenon is accounted for by a low value of energy stored in the storage capacitance (6).

The main performances of our proprietary beamless generator are given in Table 1.

Table 1.

This option of the generator also includes an antenna mirror that allows to control the beam position.

Our proprietary generator of single pulses and bursts of broadband pulses can be used in diverse studies on electromagnetic compatibility.