Patent Grant
8145119
The present invention relates to electronic countermeasure jamming systems that are capable of interrupting radio links from triggering devices used in connection with improvised explosive devices. In particular, the invention related to method of using a jamming system that includes distributed jamming units that are free to translate and yaw with respect to one another.
Known countermeasure systems have diverse broadband radio signal generators that are fed into a relatively simple antenna. The antenna attempts to have omni-directional coverage. The simplest antenna is a half dipole oriented vertically at the center of the area to be protected by jamming. The problem with such antennas is that they do not have spherical coverage patterns for truly omni coverage. Coverage of such a simple antenna appears shaped like a donut with gaps in coverage above and below the plane of the donut because the simple dipole cannot operate as both an end fire antenna and an omni antenna. More complex antennas may add coverage in end fire directions but generate interference patterns that leave gaps in coverage.
In an environment where small improvised explosive devices (TED) are placed in airplanes, busses or trains and triggered by radio links distant from the IED, it becomes more important to successfully jam the radio link without gaps in jamming system coverage.
Known omni directional systems radiate to provide 360 degree coverage on a plane with elevations plus or minus of the plane. Very few truly omni directional antenna systems are known to create coverage in three dimensions on a unit sphere. Difficulties are encountered that include, for example, the feed point through the sphere causes distortion of the radiation pattern, metal structures near the antenna cause reflections that distort the radiation pattern, and the individual radiating element of an antenna inherently does not produce a spherical radiation pattern. In addition, providing a spherical radiation pattern over a broad band of frequencies can be extremely difficult. Antenna structures intended to shape the radiation pattern at one frequency can cause distortion in the radiation pattern at another frequency.
The inventor's published International Application, WO 2006/086658 A1, titled “Antenna System”, filed Feb. 13, 2006, describes novel antenna systems and is incorporated by reference herein.
A jamming system includes at least three jamming units. Each jamming unit is separately positionable and pointable. Each jamming unit covers different frequency bands. A method of using the jamming system includes moving a first jamming unit relative to a second jamming unit, and yawing a first jamming unit relative to an orientation of a third jamming unit.
The invention will be described in detail in the following description of preferred embodiments with reference to the following figures.
A novel method of using a jamming system will be described below with respect to a distributed jamming system of a type repackaged from a central integrated jamming system. First, the central integrated jamming system will be described, followed by a description of the repackaging of the central integrated jamming system into the distributed jamming system, and then the method of using the distributed jamming system.
In
In operation and as depicted in
Antenna 10 has a shape similar to a “bow tie” antenna, and it functions as a broad band antenna. The two halves of the “bow tie” are preferably disposed on opposite sides of the insulating substrate 12, but may, in other variations, be formed on the same side. Antenna 10 is preferably fed from an end point instead of a center point as is common with “bow tie” style antennas. However, in other variations, antenna 10 may be fed from other point, such as the center. In one variation of this antenna, the entire antenna is formed from a double sided copper clad epoxy-glass printed wiring board. In such case, conductor 30 is typically a plated through hole, but may be a rivet or pin held in place by solder filets 32 as depicted in
In
In operation, applied RF signal currents fed through coupler 64 pass though feed portions 72, 74 into ground bus 50 and radiating element 62. From there, electric fields extend between ground bus 50 and the radiating element 62 in such a way to cause RF signals to radiate from antenna 60.
In alternative embodiments, any one or more of antennas 80, 82 and 84 are similarly formed on the same insulating substrate. Each alternative antenna embodiment is varied by size and shape to meet frequency requirements and impedance matching requirements according to “patch radiator” technology. The size and shape of the feed portions 72, 74 are defined to match impedances from the coupler 64 to the radiating element of the antenna.
In
Antenna 90 further includes a tap conductor 106 coupled between the first signal conductor 96 of coupler 94 and a predetermined one of the plural turns of the wire 100. The predetermined turn number is determined during early design stages and may be easily defined by trying several different turn numbers and measuring the antenna's performance. A first end of the plural turns of wire 100 is coupled to the second signal conductor 98.
In operation, applied RF signal currents fed through coupler 94 pass though conductor 96, through tap wire 106 to the predetermined one of the plural turns of wire 100, and from there through a portion of wire 100 to the first end of wire 100 to conductor 98.
In
The electronic modules may be placed in locations other than those depicted in
In a first embodiment of an antenna system, the antenna system includes plural antennas. Each antenna is different than every other antenna, and each antenna is characterized by a principal plane. A principal plane of a first antenna 230 is oblique to a principal plane of a second antenna. The second antenna may be located and oriented as depicted by antenna 240 or 250 in
In a first variant of the first embodiment of the antenna system, the second antenna is located and oriented as antenna 240 in
In an example of the first variant of the first embodiment of the antenna system and much as is described with respect to the antenna depicted in
In a first mechanization, the principal planes of the first and third antennas 230, 250 are oblique; and possibly substantially orthogonal.
In an example of the first mechanization, the principal planes of the second and third antennas 240, 250 are substantially parallel.
In a second mechanization, the principal planes of the second and third antennas 240, 250 are substantially parallel.
In a second variant of the first embodiment of the antenna system, the second antenna is located and oriented as antenna 250 in
In a second embodiment of an antenna system, the antenna system includes plural antennas. Each antenna is different than every other antenna, and each antenna is characterized by a principal plane. A principal plane of a first antenna is substantially parallel to a principal plane of a second antenna 240. Much as is described with respect to the antenna depicted in
In a first variant of the second embodiment of the antenna system, the first antenna is located and oriented as antenna 250 in
In a third embodiment of an antenna system, the antenna system includes plural antennas. Each antenna is different than every other antenna, and each antenna is characterized by a principal plane. A principal plane of a first antenna 250 is oblique to a principal plane of a second antenna. The second antenna may be located and oriented as depicted by antenna 230 in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted at 60 in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted at 80 in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted at 82 in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted at 84 in
In many variants of the above embodiments, antennas designed substantially similarly to the antenna depicted in
In a jammer operation, the antennas are fed by signal oscillators. While known broadband jammers require noise generators, with the present invention, inexpensive oscillators may be used. It should be noted that spectral purity of the oscillator is not a requirement. Waveforms distorted from pure sinusoidal waveforms merely add to the broadband coverage. The several antennas, located in the near radiation field (i.e., within 5 to 10 wavelengths) from each other, add to the distortion giving rise to a broadband effect. Signals radiated from one antenna excite parasitic resonance in other nearby antennas. The oscillators for a frequency range from 400 MHz to 500 MHz, for a frequency range from 800 MHz to 900 MHz, for a frequency range from 1,800 MHz to 1,900 MHz, and for a frequency range from 2,400 MHz to 2,500 MHz are located in electronic module 226 of
The overall antenna system is intended to work with the oscillators to disrupt communications in selected bands. When considering design balancing, the need for portable operation and long battery life gives rise to a need for low transmit power. However, high transmit power is generally needed to jam a data link. Long battery life is best achieved by ensuring that the radiation intensity pattern is efficiently used. Coverage for the system described is intended to be omni directional in three dimensions. Thus, the best antenna pattern is achieved when there are no main lobes with great antenna gain and no notches with below normal antenna gain. For at least this reason, placement of the antennas and all conductive elements (e.g., electronic modules 224 and 226) are very important, a requirement that become all the more difficult when another requirement of broadband jamming is required in selected bands.
To meet these stringent requirements, the design process 300 includes measuring performance, analyzing the results and adjusting the antennas' location, orientation and individual antenna design. In
In
In
A first embodiment of a central integrated jamming system is depicted in
In a variant of the first embodiment and as depicted in
1. a noisy signal from generator 1020 to the programmable feed unit;
2. a signal to control phase shifting of the noisy signal in the programmable feed unit; and
3. a signal to control attenuation of the noisy signal in the programmable feed unit.
The phase shifted and/or attenuated version of the noisy signal is then provided by the programmable feed unit to control the controllable amplifier 1064 in the receiver unit. This ensures random noise is produced from the transmit antenna.
In operation, each device tends to oscillate on its own. A signal from the transmit antenna is picked up on the receive antenna. The signal picked up on the receive antenna is received in receiver 1062, amplified in amplifier 1064 and provided to transmitter 1066 that is coupled the respective transmit antenna. When this loop provides enough gain, the device will oscillate. In fact, the proximity of the antennas helps ensure that the loop will have enough gain. Amplifier 1064 may well provide fractional amplification or operate as an attenuator. This loop is adjusted to have a loop gain from just below oscillation to just above oscillation when operated on its own. The receive antenna will pick up additional signals from other transmit antennas in system 1010 and from reflections off nearby reflective surfaces. In addition, signals from the respective programmable feed device 1038, 1048 or 1058, as discussed herein, are added into the loop at amplifier 1064. The loop gain is adjusted to oscillate with a random noisy waveform in this environment.
In another variant of the first embodiment, either the transmit antenna or the receive antenna, or both, of first device 1030 is a directional antenna directed toward a point inside the area to be protected, either the transmit antenna or the receive antenna, or both, of second device 1040 is a directional antenna directed toward the point inside the area to be protected, and either the transmit antenna and the receive antenna, or both, of third device 1050 is a directional antenna directed toward the point inside the area to be protected. In operation, directing antenna gain inside the area to be protected tends to minimize collateral jamming effects outside of the desired area to be protected, and tends to minimize the power required from transmit antennas 1034, 1044 and 1054 to achieve the desired level of jamming inside the area to be protected.
In another variant, the devices 1030, 1040 and 1050 are located near a reflective surface or reflective surfaces that are characterized by a curvature. This produces reflected signals that appear to come from conjugate images of the transmit antennas of the devices.
In yet another variant, the devices 1030, 1040 and 1050 are located near a reflective surface or reflective surfaces that are characterized by a curvature. The reflective surface includes any or all of the inside walls of an aircraft, the inside walls of a railroad car, the inside walls of bus, the walls of a subway tunnel, the walls of an automobile tunnel, and the walls of an auditorium, conference room, studio or the link. This also produces reflected signals that appear to come from conjugate images of the transmit antennas of the devices within the aircraft, the railroad car, the bus, the subway tunnel, the automobile tunnel, or the auditorium.
In another variant of the first embodiment, the generator produces a signal that is characterized by a center frequency. The generator includes a comb generator with a bandwidth greater than 20% of the center frequency and preferably grater than 50% of the center frequency. In practical systems, jamming of signals at frequencies of 312, 314, 316, 392, 398, 430, 433, 434 and 450 to 500 MHz may be desired. A center frequency of 400 MHz and a jamming bandwidth of 200 MHz (307 MHz to 507 MHz, a 50%© bandwidth) would cover this range. A very suitable system for some application may be realized by jamming 430 through 500 MHz (a 20% bandwidth centered on 460 MHz). The frequency band from 312 through 316 MHz may be easily covered by a 2% bandwidth generator, and the 392 and 398 MHz frequencies may be easily covered by a generator with just a little more than 2% bandwidth.
In another variant of the first embodiment, the programmable feed unit in each device includes either a programmable attenuator coupled to the generator, a programmable phase shifter coupled to the generator, or both. In a version of this variant, where the programmable feed unit in each device includes the programmable attenuator, the programmable attenuator includes a variable gain amplifier characterized by a gain controlled by a signal from the generator. In another version of this variant, where the programmable feed unit in each device includes the programmable phase shifter, the programmable phase shifter may be mechanized with several designs.
In one design, the programmable phase shifter includes a network that includes a variable inductor where an inductance of the inductor is controlled by a signal from the generator. An example of such a variable inductor is a saturable inductor. A saturable inductor includes two coils wound around a common magnetic material such as a ferrite core. Through one coil, a bias current passes to bring the ferrite core in and out of saturation. The other coil is the inductor whose inductance is varied according to the bias current. The bias current is generated in generator 1020, and it may be either a fix bias to set the phase shifting property or it may be a pulsed waveform to vary the phase shifting property.
In another design, the programmable phase shifter includes a network that includes a variable capacitor where a capacitance of the capacitor is controlled by a signal from the generator. A back biased varactor diode is an example of such a variable capacitor.
In yet another design, the programmable phase shifter includes a variable delay line where a delay of the delay line is controlled by a signal from the generator. A typical example of this type of delay line at microwave frequencies is a strip line disposed between blocks of ferrite material where the blocks of ferrite material are encircled by coils carrying a bias current so that the ferrite materials are subjected to a magnetizing force. In this way, the propagation properties of strip line are varied according to the magnetizing force imposed by the current through the coil.
In yet another design, the programmable phase shifter includes two or more delay lines, each characterized by a different delay. The phase shifter further includes a switch to select an active delay line, from among the two or more delay lines, according to a signal from the generator.
Whatever the design that is used, the bias current or control signal is generated in generator 1020. It may be either a fixed voltage or current to set the phase shifting property of the programmable feed unit or it may be a pulsed waveform to vary the phase shifting property.
In another variant of the first embodiment, generator 1020 is processor controlled. The processor may be a microprocessor or other processor. A memory stores the modes of operations in the form of a threat table that specifies such parameters as the center frequency and the bandwidth of the signals to be generated by generator 1020 for each threat or application (e.g., tunnel, aircraft, railroad car, office auditorium, etc.) and stores the attenuation and phase shifting properties to be provided to each of the programmable feed units 1038, 1048 and 1058. In a typical generator design, the threat table provides a center frequency for a radio frequency jamming signal and also proved a seed for a random number generator (e.g., digital key stream generator). The random numbers are used to generate a randomly chopped binary output waveform at about 5 to 20 times the center frequency that used as a chopping signal to modulate the signal at the center frequency. Many other types of noise generators may also be used. The output of the chopped center frequency signal is a broadband noise signal that is provided to each of the programmable feed units 1038, 1048 and 1058.
In alternative variants, generator 1020 includes circuits to generate additional randomly chopped binary output waveforms, according to parameters in the threat table, to control the variable attenuator and/or the variable phase shifter in each of the programmable feed units 1038, 1048 and 1058. Alternatively, the threat table may store a fixed number, for each threat, to provide a fixed attenuation and a fixed phase shift in the programmable feed units 1038, 1048 and 1058 that may be selected differently for each threat.
The above described central integrated jamming system is partitioned into three separate jamming units. The first jamming unit covers a low band at selected frequencies, for example, from about 20 MHz to 200 MHz and 462 MHz to 468 MHz, or any band into which it is desired to send a higher level of concentrated jamming power. The second jamming unit broadly covers the low band, for example, from 3 MHz to 500 MHz to jam frequencies that do not require the specific concentration of jamming power. The third jamming unit broadly covers a high band, for example, 0.7 GHz to 3 GHz, or other band into which it is desired to jam.
These three repackaged units are not identical, but instead cover their respective assigned bands. Nevertheless, signals from the all three jamming units inject RF power into the target to be jammed. Additionally, harmonic signals associated with the radiated RF signals from each of the individual jamming units interact with the RF signals radiated from the other jamming units, even though out of band, so as to be additive as nonlinear signal distortions directed into the target to be jammed. In this way, nonlinear distortions in the output signals are enhanced which contributes further to the randomness of the jamming and avoids nulls in coverage.
In a preferable embodiment, the three repackaged jamming units are desired to be compatible with use, i.e. carried in, a man pack. For purposes of this specification, portable as applied to the partitioned jamming units will be defined without limiting the scope of the invention as “man-packable”, meaning having a weight that is sufficiently low to be able to be carried with relative ease by a person or soldier in addition to his other equipment, i.e. preferably less than 4 kilograms plus battery weight. Further, the radiated power is preferably limited to 10 watts, and more preferably to only 7 or 8 watts. A CINGARS battery is one of the most available battery types on modern battlefield, and the limitation of less than 10 watts radiated power, permits adequate operating time using a standard CINGARS battery. The weight limit of 3 or 4 kilograms plus the weight of a CINGARS battery is compatible with man pack use.
This restriction on weight and power is also compatible with splitting the integrated jamming system into the three jamming units discussed above. Even though, each of the jamming units provides different frequency coverage, the radiated power is such that a jamming unit's sphere of coverage overlaps, at a significant power level, the spheres of coverage of the other two jamming unit when operated in accordance with the method of using the distributed jamming system.
The inventor herein has discovered that sufficient spatial overlap of the respective spheres of coverage provides sufficient random distortion in the region of operation to jam desired targets. In particular, the inventor has discovered that the random yaw characteristic of an antenna pattern of a jamming unit carried in a man pack where the soldier carrying the man pack is moving, serves to increase the distortion of the total jamming system and prevent nulls and voids. Furthermore, the inventor has discovered that the random “leap frog” positioning of soldiers carrying a jamming unit in a man pack also serves to increase the distortion of the total jamming system and prevent nulls and voids.
For example, for jamming units described above (e.g., 3 to 4 kilograms and less than 10 watts radiated power) might be carried in man packs of soldiers in close quarter combat. Separation of the soldiers in a team might be limited to 2 or 3 meters. The inventor has discovered that the man pack repackaging and use enhances distortion of signals at the target, even though the central integrated jamming system is now dispersed spatially and each dispersed jamming unit covers a different frequency band. The inventor has discovered that even if the man pack jamming units are separated by 50 meters, overlapping spherical coverages of the jamming units are sufficient to provide effective jamming of targets because of the enhanced distortion caused by random yaw of the antenna patterns and/or the “leap frog” tactics of the soldiers when carrying out close combat missions.
A system using such partitioned portable jamming units may be further enhanced by making a unique selection of the frequencies of the individual units, such that the principal harmonics of the different transmitted frequencies align in phase within the 3-dimensional volume being jammed in order to provide additive regenerative jamming effects over and above those associated with just the principal frequencies being transmitted. It can further be appreciated that by dynamically changing the frequencies of the individual units on a continuing basis, random regenerative jamming signals can be generated over broader frequency spectrum due to these same harmonic effects.
In addition to the foregoing spatial effects, which can create a changeable sphere of coverage based on the relative fixed positions of the individual jamming units at any point in time, the present invention further discloses an additional jamming effect due to the relative dynamic motion (i.e. soldier “leap-frog” tactics) of those same jamming units. This additional jamming effect is a result from the interaction of the differently polarized electromagnetic fields moving relative to teach other in real time, thereby creating a “magnetic shearing” effect. Such shearing effect creates additional broadband noise within the 3-dimensional volume, thereby further enhancing the jamming capabilities of the jamming system over that which would normally be expected in static jamming systems.
Having described preferred embodiments of a novel method of jamming (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope of the invention as defined by the appended claims.
Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.
The entire disclosures of all applications, patents and publications, cited herein and of corresponding U.S. Provisional Application Ser. No. 60/830,670, filed Jul. 14, 2006, are incorporated by reference herein.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
This application is a continuation-in-part of U.S. patent application Ser. No. 11/778,316 filed Jul. 16, 2007 now abandoned, which claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/830,670 filed Jul. 14, 2006.
| Number | Name | Date | Kind |
|---|---|---|---|
| 7697885 | Stoddard | Apr 2010 | B2 |
| 20050168375 | Halladay et al. | Aug 2005 | A1 |
| 20050212673 | Forster | Sep 2005 | A1 |
| 20060060074 | Ham et al. | Mar 2006 | A1 |
| 20060105701 | Cornwell | May 2006 | A1 |
| 20060164282 | Duff et al. | Jul 2006 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20120045984 A1 | Feb 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60830670 | Jul 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11778316 | Jul 2007 | US |
| Child | 11937119 | US |
