Towed decoy and method of improving the same

SWEDEN (12) PATENT (13) C2 di) 522 506 (19) SE ₍₅₁₎

International class ⁷

G01S 7/38

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PATENT AND REGISTRATION (45) (41) (22) (24) (62) (86) (86) (83)

Patent issued Application generally available Patent application for the expiry date

Application number International filing date

Filing date for European patent application Deposit of microorganism

2004-02-10

2003-12-20

2002-06-19

2002-06-19 (21) Patent Application Number (J201872-9

Application received as:

Swedish patent application completed international patent application with number □ converted European patent application with number (30) Priority information (73) (72) (74) (54) (56) (57)

PATENT HOLDER Total Defense Research Institute, 172 90 Stockholm SE INVENTOR Anders Eneroth, Linghem SE

OMBUD The Swedish Defense Materiel Administration

NAME Trailer interference transmitter and ways to improve one

CALLED PUBLICATIONS: - - SUMMARY: _{r J u} , , , ,„_n&gt;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lap jerk transmitter arrangement for a vehicle (20) with a jerk transmitter (21) towed by the vehicle. Threatening signals are received by the vessel and a noise signal is created which is converted up to a frequency which is quickly dampened in air and transmitted to the towed noise transmitter. In this, the received signal is transformed into the interference signal by moving it to the frequency of the threatening signal. The signal is then transmitted from the interference transmitter.

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The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code.

522 506

Summary:

BACKGROUND OF THE INVENTION The present invention relates to a trailer interference transmitter arrangement for a vehicle (20) with a disturbance transmitter (21) towed by the vehicle. Threatening signals are received by the vessel and a noise signal is created which is converted up to a frequency which is quickly dampened in air and transmitted to the towed noise transmitter. In this, the received signal is transformed into the interference signal by moving it to the frequency of the threatening signal. The signal is then transmitted from the interference transmitter.

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The present invention relates to a tow transmitter and a method of improving one. The invention has emerged in an effort to be able to use an existing tow transmitter more efficiently through various additions. However, it is just as good to build a brand new tow truck transmitter in a similar way.

A tow jumper is a type of offboard jumper that is designed to create an angle error in a threat system, primarily against target seekers. You drag the jammed transmitter behind, for example, an airplane and let it create a false target, which should be more powerful than the hull. When using towed transmitters, it is important that there is an angular separation between the target and the rail target. Any type of maneuver is normally required by the aircraft.

However, it is not only aircraft that can have towed transmitters, but also vessels. However, such interference transmitters themselves are more maneuverable than in the airfall. We will present the invention below with examples from the airfall. The same can be stated for the vessel case and no restriction on the scope of protection due to the examples given is not intended.

There are two types of trailer interference transmitters, one where an entire repeater interrupter is implemented in the trailer body and one where the trailer body contains only one transmitter part. In this case, the signal is fed from the aircraft.

In the first case, the threat signal is received in the trailer body. The main transmitter then repeats incoming signals and creates a track target, the size of which depends on the total loop gain in the system. Some form of amplitude or phase modulation may occur.

In the case of the second case, the development of tow-transmitters is being developed in various parts of the world, which receive RF signal via a fiber-optic link from the aircraft's interference transmitter (inboard or outboard mounted). Problems with isolation between the antennas are then radically reduced, which allows a larger target area to be generated and thus provide a greater certainty that the rail target pulls the robot towards it. Another advantage is that the aircraft's interference transmitter is usually more advanced and has a wider range of interference types that

522 506 to choose from. The trailer body also contains less electronics in this case, which means that the cost is kept down, especially if the trailer is hit by the robot or lost in some other way.

The invention provides an advantageous alternative which also means that it is easy to supplement older towing transmitters of the first type and give them greatly improved properties. This is done by providing the invention with the features set forth in the appended independent claims. Other claims relate to suitable embodiments of the invention.

In the following, the invention will be described in more detail with reference to the accompanying drawing, in which Fig. 1 shows an illuminated towed target for aircraft according to the invention and Fig. 2 shows a block diagram of an embodiment of the invention.

The inventive tow-steer transmitter arrangement for a vehicle 20 comprising one of the vehicle-towed transceivers 21. Figure 1 shows what it can look like in the airspace. Fig. Shows how the arrangement can be constructed. In the vehicle, here the aircraft, there is an antenna 1 for receiving threatening signals, such as radar pulses, and an analysis and noise-generating device 2 for property protection. It can either be built-in or carried as a capsule on a loading beam. The interfering signal created is transformed into a frequency that is rapidly attenuated in air and differs from the frequency of the threatening signal. That signal is transmitted via an antenna 5 to the towed interference transmitter.

The towing body (interference transmitter) is provided with an antenna 6 which receives the signal from the antenna 5 of the vehicle and a device 7,8,9,10,11 which transforms the received signal back to a disturbance signal by moving it to the frequency of the threatening signal. This signal goes to an actual noise transmitter 12 with antenna 13 for transmitting the noise signal in the direction of the source of the threat signal. If one assumes an older trailer interference transmitter of the first type described above, the latter actual interference transmitter and the antenna may be the hitherto disturbed transmitter with antenna.

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Figure 2 also gives more concrete examples of how a system according to the invention can be designed. The created interference signal is input to a mixer 3 connected to a local oscillator 4. The antenna 5 is connected to the third port of the mixer 3. The signal received by the antenna 6 is divided into a power divider 7. One branch is used to recreate the local oscillator signal via a bandpass filter 8. The filter has a pass band at the frequency of the LO signal and a bandwidth that allows the LO signal to pass, but blocks the mixed signal. The recreated LO signal is amplified in an amplifier 9 and then feeds a mixer 10. In the mixer, the recreated LO signal is mixed with the transmitted signal from the second port of the power divider. Out of the mixer, the signal is filtered into a low-pass filter 11, and the original signal is recreated and fed to the actual tow transmitter 12.

The absolute greatest danger in using illuminated tow transmitters is that the threat may lock on the signal from the aircraft to the tow body or strong lateral lobes from that signal. First, to eliminate this threat, a different frequency of transmission is used than the frequency of the current threat. The most natural is to convert the signal up in frequency. It is a clear advantage if the frequency band for the transmission is clearly outside the normal frequency band for warning systems. Another way to reduce the risk that the signals between the vehicle and the trailer body are intercepted by the threat is to use signals that are attenuated quickly in air, a target value can be an attenuation of at least 1 dB / km.

It is known that the atmosphere contains different frequency bands with different propagation attenuation. Frequency bands with good transmission (low attenuation) include the various radar bands (L, S, C, X, Ku), some parts of the mm-wave band (26 - 200 GHz), and also IR bands.

A special frequency band around 60 GHz is interesting for opposite reasons. The attenuation is particularly high for this band and allows only short communication distances between transmitter and receiver at this frequency. The millimeter wave band over 58 GHz is interesting for using hard-to-listen links, but there are not very many components. This means that the few that are normally available are very expensive. Higher frequencies are also of interest, as it is very uncommon for eavesdropping systems to operate at these high frequencies.

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Another advantage of the millimeter wave range is that the transmitted bandwidth is large in absolute bandwidth, but small as relative bandwidth. The bandwidth likely in a tactical scenario is between 8 - 18 GHz. 10 GHz at 77 GHz means a relative bandwidth of 13%, which is not remarkable. By comparison, the relative bandwidth of a 10 GHz signal on the X and Ku band is about 77%.

The limited relative bandwidth entails, among other things. that a system can become fairly even in frequency, etc.

Furthermore, the band around 77 GHz is special when used for car radar and therefore 10 starts to be available at competitive prices. Therefore, in a particularly advantageous embodiment of the invention, a signal of frequency 77 ± 5 GHz is used.

An important parameter regarding the lighting antenna is the lobe width. Of course, it is required that the lobe is guaranteed to lie on the trailer body. At the same time, you do not want to spread signals more than necessary. For a given given aperture size, it is generally true that the higher the frequency, the narrower the lobe becomes. For 77 GHz, the aperture becomes very small, which is a big advantage on the target.

The gain of an antenna can be calculated when the lobe angles are known by the following formula (rule of thumb):

30000

O_az Lobe width in azimuth [7 θ_βι Lobwid in elevation / 7

An antenna coverage of ± 10 ° in the respective plane gives an antenna gain of about 18 dB.

The gain for antenna horns is calculated by the following formula:

Zgz_eff ~.

4π · η

A_eff Effective antenna area 30 λ Wavelength

G Antenna gain η Antenna efficiency (about 0.6 for square horns) With 77 GHz input values, the aperture area becomes approximately 1.5 cm².

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