IL192857A - High-power microwave generator for emitting short pulses, its use in an array and array comprising such microwave generators - Google Patents

Description

HIGH-POWER MICROWAVE GENERATOR FOR EMITTING SHORT PULSES, ITS USE IN AN ARRAY AND ARRAY COMPRISING SUCH MICROWAVE GENERATORS ttii *\ m oni vmv ,o>isp t pat iio a >- )?tt m ma Pearl Cohen Zedek Latzer P-71039-1L WB/Fg/bu Diehl BGT Defence GmbH & Co. KG, Alte NuBdorfer Strafie 13, 88662 tiberlingen High-power microwave generator for emitting short pulses, its use in an array and array comprising such microwave generators The invention relates to a microwave generator as claimed in the precharacterizing clause of claim 1, and to its use as claimed in claim 10, as well as to an array comprising such microwave generators.

A generator such as this, which is also referred to as a DS-HPM (damped sinusoidal high-power microwave generator), is known from DE 1 03 13 286 B3. A so- called Marx high-voltage generator (referred to for the sake of simplicity in the following text as a Marx generator) is preferably used to charge its resonator with high voltage, in which a number of capacitors are charged in parallel to a high voltage and are then connected in series by means of spark gaps in order to produce a discharge current that is a corresponding multiple of the charging voltage. The capacitance of the resonator connected downstream from the Marx generator is thus charged. This is equipped with a spark gap in order to short-circuit its capacitance when the DC withstand voltage, which is governed by its design, of its spark gap is exceeded, and with an antenna with a dipole characteristic in order to emit the electromagnetic field which is then caused by the highly oscillating pulsed discharge current.

According to DE 1 03 13 286 B3, a plurality of resonators designed in this way are arranged in a group (array) and are connected to a common Marx generator for parallel charging with the direct current at a high voltage. The spark gaps are designed to have breakdown voltages which match one another as well as possible, so that the discharge currents from the resonator capacitances all start as far as possible at the same time. The time superimposition of the alternating fields caused by the discharge currents and resulting from this in the far field governs the spatial geometry of the formation of a narrow beam, as is desirable in the interest of long-distance effectiveness, of the resultant array polar diagram.

However, apart from the respective charging time constant and the response of their spark gaps, the emissions from the individual resonators, which are operated in parallel in this way untriggered, actually start with an unavoidable time offset with respect to one another in particular because of the lengths of the feed lines from the Marx generator. This has a correspondingly detrimental effect on the desired beam formation, that is to say the effective range of the emission characteristic; and in practice this leads to virtually unpredictable swiveling, which it is virtually impossible to predict and influence for this reason, even by control techniques, of the emission direction from the direction, normal to the array. For operational usable microwave generators with group arrangements of resonators which are fed in this way from a common direct-current source and whose individual spark gaps should all respond within a time interval in the typical order of magnitude of at most 100 picoseconds, in the interest of adequate longdistance effectiveness of their interfering emissions, the number of resonators to be grouped is therefore very limited, because of the different lengths of their charging lines.

Against the background of these circumstances, the invention is based on the technical problem of specifying a microwave generator which allows a higher power density to be achieved during array operation and which also allows the beam to be scanned over a wide scanning range as far as possible still without major additional complexity.

According to the invention, this object is achieved by the use of resonators, which as basic modules are equipped with the essential features specified in the main claim, for array grouping of microwave generators. Because each of these basic modules is equipped with its own, and now triggerable, Marx generator for generation of the high voltage for triggering the short-circuiting spark gap of its resonator, this avoids not only the disturbing effects for array operation of charging paths of different length but also the mutual functional relationships which previously occur as a result of reactions via a common charging path. Arrays can therefore now be formed from groups of very many more elements (resonators) , thus overall allowing larger emitting types, that is to say narrower beam formation as a result of superimposition of correspondingly more individual emissions from a larger area, therefore resulting in a greater intensity of the emission characteristic resulting in the far field. Since, on the other hand, each resonator acts autonomously and therefore with dipole emission which has not been formed into a beam, the grouping of basic modules equipped according to the invention also makes it possible to achieve the widest possible angle range for the spatial scanning of the emission characteristic resulting from the superimposition, by triggering the individual basic modules with slight time offsets.

According to one preferred development of the present invention, integration of the Marx generator which can be triggered via one of its spark gaps, preferably together with its triggering circuit which can be energized individually and externally is provided in the resonator itself for practical implementation of the basic modules for the array arrangement of the microwave generators, with a concentric and therefore particularly compact design with a spark gap which is no longer axial but radial, that is to say annular. The DC voltage source together with the DC/DC voltage converter which may follow it is then expediently included in the concentric design and is arranged coaxially in an antenna in the form of a funnel, which is axially adjacent to a quarter-lambda resonator for the microwave generator, to feed the Marx generator. This avoids external wiring for the internal operation of the respective basic module, and therefore disturbance influences, which can otherwise lead to malfunctions, such as premature triggering of one basic module and in consequence to attenuation of the resultant emission characteristic, for example as a result of high-voltage flashovers or injected radio- frequency interference.

For the same reason, the triggering circuits in the individual basic modules are expediently not driven electrically at the same time (for beam optimization) or with a slight time offset (for beam scanning) via cables, but preferably opto-electronically. This can be done, for example, by accessibly integrating a photosensor at the end in the respective resonator, so that all the basic modules of an array, which is housed in a light-proof manner appropriately as required, are triggered at the same time by generation of a signal light flash.

In any case, according to the invention, an array of microwave generators for HPM pulse emissions achieves better long-distance effectiveness by better beamforming of the resultant polar diagram, discharge currents which start more exactly at the same time in their resonators and, in order to scan the resultant polar diagram, a time offset which can be controlled more precisely between discharge currents, when basic modules are used for this purpose which are each equipped with their own Marx generator which can be triggered externally, and preferably optically. A particularly compact embodiment with line routing that is protected against environmental influences is obtained for each of these basic modules with a coaxial design, in which the respective Marx generator is arranged together with its triggering circuit directly in the interior of the resonator, with the input-side connection of the Marx generator in contrast being axially offset to a DC voltage supply which is accommodated in the interior of the antenna, which is in the form of a funnel, and with its output-side connection to the central electrode of an annular short-circuiting spark gap for the resonator.

Additional alternatives and developments relating to the solution according to the invention result from the further claims and from the preferred exemplary embodiment according to the following description, which also deals with further advantages of the invention. The description refers to the attached outline sketch of a basic module according to the invention, which is in the form of an axial longitudinal section that is not entirely to scale, in the interest of a functional description.

The basic module 10 according to the present invention, which is designed in particular for use in an antenna-element array for example according to DE 1 03 13 286 B3 (but now without the resonators being charged from a common Marx generator) includes the coaxial quarter-lambda resonator 11 of a high-power microwave generator 12 with an antenna 13, which is in the form of a funnel and is connected to it coaxially, in a tubular housing 14, which is common to both and is composed of insulating material that is resistant to high voltages.

The resonator 11 of the microwave generator 12, which operates in a pulsed manner, has a cylindrical capacitance 15 in the form of an inner electrode 17, which is concentrically surrounded at a distance by an outer electrode 16 that is stretched in the form of a pot, which inner electrode 17 is approximately in the form of a bottle and its neck 18, which is in the form of a funnel, is adjacent to the small base area 19 of the hollow truncated cone of the antenna 13. A short- circuiting spark gap 20, which in this case is radial, that is to say annular, is formed coaxially between the outer electrode 16 and the inner electrode 17, between the two electrodes 16 and 17, specifically in the form of a shaft stub 21 which is used as a central spark-gap electrode, projects concentrically in the interior of the outer electrode 16 from its base 22, and projects into a hole 23 in the base 24 of the inner electrode 17, with an unobstructed gap on all sides. The effective resonator 11 is governed by the capacitance 15 and the inductance of the spark gap 20, apart from the line inductances that occur.

A Marx generator 26 is accommodated in the elongated interior 25 of the inner electrode 17 and is connected on its high-voltage side to the capacitance 15 of the resonator 11, specifically by its high potential to the shaft stub 21 of the spark gap 20 and by its low potential with respect to the spark gap 20, in the direction of the antenna 13, axially at a distance from the inner electrode 17, which is normally connected to a common ground or directly to ground potential 27.

For autonomous operation of the microwave generator 12, this is equipped with a DC voltage supply 29 in the cavity 28 of its antenna 13. In this example, this supply 29 comprises a (preferably rechargeable) battery 30 followed by a DC/DC voltage converter 31, which in this case operates balanced with respect to ground potential 27, for feeding the Marx generator 26 via wiring which, as shown in the sketch, runs through the bottle neck 18 of the inner electrode 17.

The microwave generator 12 is equipped with an externally triggerable Marx generator 26, in order to initiate it. For this purpose, it has one triggerable spark gap 32 among its spark gaps for switching from parallel to series connection of its capacitors. In order to energize its triggering, a spark gap 32 such as this which is not self-switching but can be triggered can be physically designed with an additional electrode for supplying potential from a triggering circuit 33, or it reacts to some other- type of external power supply, for example by means of UV or laser flashlight, from the triggering circuit 33. This is well shielded from environmental influences within the resonator 11, for example as in the sketch in the Marx generator 26 itself, and is preferably triggered opto-electronically, for interference protection reasons. A photosensor 34 for external optical excitation is accessible for this purpose, approximately concentrically, in a cover, which closes off the antenna 13 from the outside over its relatively large base area, or, as is shown by way of example in the sketch here, in the base 22 of the outer electrode 16. The shaft stub 21 which is provided for this purpose preferably has a longitudinal channel 35 for the protective wiring from the photosensor 34 to the triggering circuit 33.

When, for example, a plurality of basic modules 10 equipped in this way are grouped in a mounting frame to form an array, it is sufficient, if necessary with the effective light delay times being matched by means of optical waveguides that are appropriately cut to length, to generate one external light flash in order to simultaneously initiate all the microwave generators 12 via their photosensors 34, and in this way to achieve optimum superimposition of the individual antenna emissions. In contrast, this leads in a manner known per se to controlled beam scanning, for example in the case of an array which is installed in stationary form, when a light source 36, for example a semiconductor diode which emits radiation, is spatially associated with each photosensor 34 in the array, and current is passed through these light sources in a defined sequence, with slight time delays with respect to one another, from an external control circuit.

List of reference symbols Basic module 11 Quarter-lambda resonator 12 Microwave generator 13 Antenna 14 Housing Capacitance 16 Outer electrode in the form of a pot 7 Inner electrode in the form of a bottle 8 Neck (of 17) 9 Small base area (of 13) 0 Short-circuiting spark gap (between 16-17) 1 Shaft stub (on 22) 2 Base (of 16) 3 Hole (in 24) 4 Base (of 17) Interior (of 17) 6 Marx generator 7 Ground potential 8 Cavity (in 13) 9 DC voltage supply (with 30, 31) 0 Battery 1 DC/DC voltage converter 2 Triggerable spark gap (in 26) 3 Triggering circuit (for 32) 4 Photosensor (in 22, for 33) Longitudinal channel (through 21, from 34 to 33) 6 Light source

Claims (17)

Patent Claims

1. A concentrically constructed high-power microwave generator (12) having a resonator (11) which can be charged from a Marx generator (26) , can be short- circuited via a spark gap (20) and has hollow- cylindrical electrodes (16, 17) for emitting short pulses via an antenna (13), in particular for grouping in an array, characterized in that a Marx generator (26) which is equipped with an externally triggerable spark gap (32) is arranged in the interior (25) of the inner electrode (17).

2. The microwave generator as claimed in claim 1, characterized in that the short-circuiting spark gap (20) is annular.

3. The microwave generator as claimed in the preceding claim, characterized in that the short-circuiting spark gap (20) has a shaft stub (21) which projects from the base (22) of an outer electrode (16), which is in the form of a pot, into a hole (23) in the base (24) of an inner electrode (17), which is in the form of a bottle.

4. The microwave generator as claimed in the preceding claim, characterized in that the output side of the Marx generator (26) is connected on the one hand to the inner electrode (17) and on the other hand via the shaft stub (31) to the outer electrode (16) .

5. The microwave generator as claimed in one of the preceding claims, characterized in that the input side of the Marx generator (26) is connected to a DC voltage supply (29) , which is accommodated in the cavity (28) in the antenna (13), which is in the form of a funnel.

6. The microwave generator as claimed in the preceding claim, characterized in that the supply (29) has a DC/DC voltage converter (31) behind a battery (30).

7. The microwave generator as claimed in one of the preceding claims, characterized in that the Marx generator (26) is equipped with a triggering circuit (33) which can be energized externally, for its triggerable spark gap (32).

8. The microwave generator as claimed in the preceding claim, characterized in that a triggering circuit (33) is provided which can be energized optically via a photosensor (34).

9. The microwave generator as claimed in the preceding claim, characterized in that the photosensor (34) is arranged close to the base (22) of the outer electrode (16), behind a hollow shaft stub (21) .

10. Use of microwave generators (12) as claimed in one of the preceding claims for creation of a generator array.

11. An array comprising microwave generators (12) as claimed in claim 10.

12. The microwave generator according to any one of claims 1-9 substantially as described hereinabove.

13. The microwave generator according to any one of claims 1-9 substantially as illustrated in any of the drawings.

14. Use according to claim 10 substantially as described hereinabove.

15. Use according to claim 10 substantially as illustrated in any of the drawings.

16. An array according to claim 1 1 substantially as described hereinabove.

17. An array according to claim 1 1 substantially as illustrated in any of the drawings. For the Applicant Pearl Cohen Zedek L; Advocates, Notarie!