DE3917670A1 - Defence appts. from missile duplex radio transmitters and receivers - uses Doppler detection techniques to switch off radio transmitter for short periods - Google Patents

Abstract

The equipment transmits radio waves which, when replected from moving objects, produce a Doppler frequency shifted received radio wave at either a higher or lower frequency than the original transmitted wave. The transmitter is switched off for a short period of time delta-t whenever a threshold level is exceeded. Preferably the equipment includes a Doppler radar receivers (60-66) comprising bandpass filter (60), mixer (61), Fast Fourier Transform filter (63), Comparator (64), summator (65) and alarm generator (66); and a transmitter (30-34). USE - Protection of radar installations from antiradiation missiles.

Description

The invention relates to a method for protecting an im Intercom (duplex) operated working radio relay Transmitting / receiving system against destruction by moving geg nerische objects according to the preamble of claim 1 and a directional radio transmitting / receiving system for execution of the procedure.

The introduction of anti-radar missiles ("Antiradiation Mis siles "or" ARMs ") to combat radar installations of Air defense allows the expectation that it is technically possible  will be, unmanned missiles such. ARMs or air or ground-based combat drones to create against Directional radio equipment can be used.

The object of the invention is therefore a Verfah to create a directional radio transmitter / receiver effective against destruction by mobile opponents Objects such as ARMs or combat drones are protected can.

The inventive solution to this problem is in Pa tentanspruch 1 described. The remaining claims enthal th advantageous embodiments and further developments of the invention according to the method and a radio relay according to the invention. Transceiver for implementing the invention Process.

The solution according to the invention is that of the Transmit / receive antenna or from a separate antenna the radio relay transmitter / receiver to be protected be emitted at a in the Radio relay radiation field of the plant moving object such as e.g. an unmanned missile (ARM, combat drone) or reflected in an aircraft and in their frequency position in Dependence on the speed of the object around the Doppler frequency towards lower or higher frequencies be moved.

In the receiving part of the system, the reflected monitoring signals are detected and their level compared with a pre-given threshold. Exceeds the average level for a predetermined period, the threshold, immediately transmitting the operation of the system for a certain time period Δ t is then ( "dead time") is interrupted.

The height of the threshold is determined by the expected range of coverage of the enemy objects, ie the range within which it is possible for an enemy object to detect the radio relay / receiver. The duration Δ t of the interruption of the transmission mode is determined by the speed and the Auffaßreichweite of the opposing object and is greater than the time which must be painted after the detection of the object ver through the system so that the system again outside the Auffaßreichweite of the opposing object to come to rest.

As monitoring signals in the context of the invention are suitable in particular the modulated or unmodulated Trägeri signals issued by the radio transmitter / receiver be sent.

In a preferred embodiment of the invention, the Doppler frequency is determined from the frequency position of the detected control signals and the time period Δ t in which the transmitting operation of the plant would be to interrupt, if appropriate, in function of the determined Doppler frequency chosen so that the time period Δ t is longer so as to is, the lower the determined Doppler frequency, ie the lower the speed of the enemy object.

To determine the Doppler frequency can advantageously the Discrete Fourier Transformation, in particular under Appl Fast Fourier Transformation Method ("FFT") be used.  

In a particularly advantageous embodiment of the method, the OF INVENTION to the invention interruption of operation existing at the moment of Sendebe microwave links of the system for the period Δ t of the interruption are retained. Subsequently, after the interruption, these connections live again.

In the following the invention will be explained in more detail with reference to FIG. 1, which shows an advantageous embodiment of the microwave radio transmission / reception system according to the invention for the lead out of the method according to the invention.

To prevent the enemy radio reconnaissance, i. the cognition and Locations (3 DF locations) of individual radio relay Difficult to transmit / receive equipment of a radio relay network, can in the individual plants a traffic-controlled Sen derleistungsregelung with the known frequency Combined jumping method.

In the frequency hopping method is after a frequency jump program on several frequencies in succession det or receive.

The intercom operation required for directional radio (Duplex mode) requires one frequency for each radio field pair. The distance between the two frequencies (Weichenab is technically the easiest constant, e.g. 40 or 60 MHz. You then come with a controller and a pro out. In frequency hopping one of the mentioned Values upward changing switch distance could be for the  aggravating enemy radio reconnaissance and thus be reasonable with reasonable technical effort.

Albeit through the combination of traffic Transmitter power control and frequency hopping the enemy radio reconnaissance regarding a Radio network can be made considerably more difficult Nevertheless, it can not be ruled out that ARMs, Combat drones or other unmanned missiles to combat tion of individual radio transmission / reception equipment used become.

Since as a result of the frequency hopping radio link not on a characteristic frequency sen det, the sensor of the ARM / combat drones must capture the entire Fre quenzbereich the bundle (for example, 100 frequencies, 300 MHz). Although the radio transmitter sends dau ernd, at the sensor receiver is not known on wel cher frequency of the bundle of stations will appear at the next jump. The sensor must therefore be ready to receive at all frequencies simultaneously, but only receives a signal on one of them (the signals on the different frequencies are not coherent). Thus, the sensor receiver needs an input voltage that is 20 dB higher than the directional radio receiver for the signal / noise ratio on the IF level ( S / R _IF ), which is considered to be necessary, for example 18 dB. The gain of the sensor antenna is 0 dB. The ultimately decisive bandwidth of the control loop for the three-dimensional guidance of the missile will be 3 kHz, which will _yield 30 dB at S / R _ZF . The direction of the transmitting radio antenna is unknown at the start of the ARM / drone. For the gain of this antenna in the direction of the missile can be assumed on average therefore a maximum of 5 dB. This results for the sensor receiver with respect to the radio receiver with respect to the reception field strength:

- 100 times bandwidth | +20 dB - 0 dB antenna gain of the sensor antenna +20 dB - 3 kHz bandwidth of the control loop -30 dB - Antenna transmission antenna gain 5 dB +15 dB +25 dB

The radio field attenuation to the missile (ARM / drone) at the Range limit must therefore be 25 dB lower than be at the radio field. The Auffassaßweite of the sensor today is about 2.5 km. As part of the possible Estimation accuracy can be expected that the steering of the Used missile from this range. Please note but that there are directions from which to approach Missiles have much lower Auffaßreichweiten become.

When an enemy missile detects the radio field Protective measures, if any, are only added Interruption of radio relay possible. If you take a flight body a slow combat drone at a speed of about 150 km / h, so must at a Auffaßreichweite of about 2.5 km the break including a time re serve for example 50% to take about 90 s.  

The radio relay systems are expediently auszustat so (for example, storage capacity) that is above it Connections are held during this time, though no traffic is possible.

Requirement for all active protective measures of the directive Radio system is that the missile of the plant itself is detected. Since the missile is passive, there are too Radar methods required.

The reflection cross section of a missile can be assumed to be 0.01 m ² , for example. Direction and distance measurement is not required. The missile must be detected within the direction and range, in which he in turn understands the radio relay. The antenna antenna can therefore be the same as the directional antenna, the gain being at least 5 dB in the relevant directions.

A radiated from the missile radar signal on at For example, 3 Ghz has a Doppler modulation of 0.5 kHz (50 km / h radial speed) to 4 kHz (750 km / h). The respective Doppler frequency can be received by a FFT (Fast Fourier Transform) filter bank with e.g. 20 filters per 175 Hz bandwidth can be determined. When in one of the filters receives a signal with more than e.g. 14 dB Si gnal-to-noise ratio occurs for a few seconds that the criterion for a missile in the Auffaßbe rich. For a Doppler radar (i.e., emitting an unmodu lierten carrier) results in the specified Parame tern a transmitter power of about 3 W. The function of this Radarsenders can therefore by the radio station (if necessary  with a slight increase in performance be taken over. You get to a frequenzagi len Doppler radar.

An advantageous embodiment of the erfindungsge MAESSEN radio transmission / reception system with integrated ARM detection shows Fig. 1st

The inventive system consists of a directional radio transmitting / receiving antenna 1 , which is connected via a circulator 2 on the one hand to the radio station 30-34 and the other via a branch 50 with the Richtfunkempfän ger 40-45 and the Doppler radar receiver 60-66 .

The radio relay transmitter 30-34 consists of a Phasenmodula gate 33 , which subjects the ZF-level of a generator 8 th th 70 MHz intermediate frequency carrier of a 4-PSK modulation. The modulating data ( 0/1 ) are fed via the modulation input 34 in the modulator 33 . The modulated subcarrier signals are supplied to a mixer 31 via an amplifier 32 . By mixing with a 1570 MHz signal, the modulated 70 MHz carrier is converted to a transmission frequency of 1500 MHz and amplified in an output amplifier 30 and added via the circulator 2 to the transmitting / receiving antenna 1 of the system.

The directional radio receiver 40-45 consists of an input-side bandpass filter / amplifier 40 whose Mittenfre frequency is tuned to the receiving frequency (for example, 1550 MHz) and a mixer 41 is connected downstream. By mixing the example appearing at 1550 MHz received signal with a 1620 MHz signal, the high-frequency received signal is converted to the 70 MHz IF level and in the known manner in the following construction groups 42-44 (intermediate frequency amplifier 42 with Begren zer , FM demodulator 43 ; low-pass filter 44 ) weiterverarbei tet. The received data signals ( 0/1 ) are finally output at the output 45 .

The Doppler radar receiver 60-66 also consists of egg nem input-side bandpass filter / amplifier 60 , the center frequency, however, is tuned to the transmission frequency of the system, ie 1500 MHz, and also a Mi shear 61 is connected downstream. By mixing the doppler shifted transmission frequency with the transmission frequency of 1500 MHz, a conversion into the LF level, so that the Doppler frequency can be determined directly in a downstream FFT filter bank 63 with 20 filters à 175 Hz. In a downstream comparison circuit 64 , the filter output signals are compared with the predetermined threshold (eg 14 dB). The comparison circuit 64 is the output side connected via a summing element 65 with the Doppler radar receiver output 66 , to which a control signal he appears when the centered over a predetermined period telte level of at least one of the filter output signals exceeds the predetermined threshold. The control signal triggers an ARM alarm with the result that is interrupted by a (not shown) control unit of the transmission operation of the system for the time period Δ t.

The frequency hopping programs are routed via a line 70 to a frequency processing unit 71 for the transmitter and receiver, which on the one hand directly with the mixers 31 and 41 in the radio station 30-34 and receiver 40-45 and at another via a further mixer 62 with the mixer 61 of the Doppler radar receiver 60-66 is connected. The weite ren mixer 62 , the 70 MHz output of the generator 8 is also supplied.

The ZF and Umsetzerfrequenzen shown for an exemplary transmission frequency of 1500 MHz show that in Dopp lerempfangsweg the lying in the LF range 0.5-4 kHz, reflected from the possibly existing ARM and shifted by the Doppler frequency transmitter frequency appears. In the numerical example, the duplex spacing (Weichenab stand) example assumed 50 MHz. When an ARM alarm occurs, the transmitter 30-34 is turned off. The reclosure occurs automatically, for example, after 90 seconds. This silence break is changeable in principle, it can be adapted to the ARM function.

In case there will be ARM's (eg fast, on approaching ballistic missiles), which after a erstmali The view of the radio-relay radiation also then with out sufficient accuracy to the target (i.e. fly if this by turning off its transmitter for the ARM "disappears", can with increased technical Auf Were the ARM deceived, i. get distracted.

When an ARM alarm and the radio transmitter shutdown described a battery-powered, non-modulated (rer portable pe) is turned on deceptive with omnidirectional antenna and a few watts transmitter power for the time period Δ t in this case play. The same is placed a few hundred meters away from the radio relay, so that the ARM be steered on this ge. The antenna is built directly on the transmitter housing. The transmitter can be partially buried on a free, radiating favorable terrain. For the transmission of the on / off commands, however, a double core line is required.

Another possibility is that the radio link system after detection of an ARM one or more Deceptive transmitter shoots, but only after a given delay after their firing the Sendebe shoot up, and then only when they are in ei ner sufficiently large distance from the radio relay are located.

These technical possibilities could be on further view especially for particularly critical radio relay nodes with several radio systems and antenna vehicles eye to get nabbed. In these special cases then falls as well the expense of spending the described deception transmitter and possibly the laying of the line little in the weight.

Claims (11)

1. A method for protecting a working in duplex mode the radio transmitter / receiver from destruction by moving enemy objects, in particular Antiradarrak th or combat drones, characterized in that emitted by the radio relay transmitting / receiving system and at a in the radio field radiation of Move moving the object reflected and shifted in their frequency position by the Doppler frequency to lower or higher frequencies out monitoring signals are detected in the receiving part of the system and that subsequently the transmission mode of the system for a certain period of time Δ t is interrupted when the averaged over a predetermined period level this monitoring signals exceeds a predetermined threshold. 2. The method according to claim 1, characterized in that as monitoring signals emitted by the plant and reflected on the object and Doppler shifted Carrier signals are selected. 3. The method according to any one of the preceding claims, characterized in that the Doppler frequency is determined from the frequency position of the detek ended monitoring signals and that the selected period of time Δ t is the longer, the lower the determined Doppler frequency. 4. The method according to claim 3, characterized in that the Doppler frequency over the Discrete Fourier Transforma tion, in particular using the Fast Fourier Trans formation procedure. 5. The method according to any one of the preceding claims, characterized in that at the moment of transmission interruption interrupt existing (n) radio link (s) of the system during the period of time Δ t is held and will be revived after the interruption ( revive). 6. The method according to any one of the preceding claims, since characterized in that during the transmission operation refraction of the facility one or more deceptions in the Environment of the plant on the same frequency as the on able to send deception signals and that the distances the sender of the system are chosen so large that at a destruction of such a deceptive transmitter by the enemy object the radio transmitter / receiver itself is not destroyed.   7. radio transmission / reception system for carrying out the proceedings according to one of the preceding claims, characterized in that the receiving part of the radio relay transmitter / receiver is extended by a Doppler radar receiver ( 60-66 ) that this Doppler radar receiver ( 60-66 ) from the transmitting part ( 30-34 ) of the system emitted and reflected on the object and Doppler shifted monitoring signals detected and their level compared with the PRE-enclosed threshold and exceeding this threshold by the level of a control signal to the interrup tion of the transmission operation of the system for the period Δ t generated. 8. radio transmission / reception system according to claim 7, characterized in that

• - That the Doppler radar receiver ( 60-66 ) eingangssei tig one with its center frequency to the Trä gerfrequenz or at least approximately on the Trä gerfrequenz of the transmitting part ( 30-34 ) of the system has a bandpass filter ( 60 );
• - That the bandpass filter ( 60 ) on the output side via a mixer ( 61 ) to the input of a Fast Fou rier transform filter bank ( 63 ) is connected;
• - That the mixer ( 61 ) is connected at its second input with a modulated with the modulated or unmodulated carrier frequency of the transmitting part ( 30-34 ) oscillating local oscillator;
• - That the individual filter outputs of the filter bank ( 63 ) are each connected to a circuit ( 64 ) for comparison equal to the filter output level with the pre-given threshold threshold;
• - That the circuits ( 64 ) on the output side via a summation element ( 65 ) with a control unit to interrupt the transmission operation of the system are the verbun.

9. radio transmission / reception system according to claim 8, characterized in that the system according to a frequency jump method continuously changes their carrier frequency and that in the Doppler radar receiver ( 60-66 ) of the input-side band passport ( 60 ) with its center frequency and the local oscillator with the frequency of its output signal follow this continuous change of the frequency position synchronously. 10. radio transmission / reception system according to Ansprü 7 to 9, characterized in that the (the) deception transmitter in the vicinity of the system with the control unit is connected (are) and that the (the) deceiver before is preferably designed as an omnidirectional transmitter (are). 11. Directional radio transmitting / receiving system according to one of Ansprü che 7 to 9, characterized in that the system comprises a device for shooting of noise transmitters, that the device only at the moment of interruption of the transmission operation of the system due to the control signal of Dopplerradarempfängers ( 60- 66) one or several verschießt deceptive and deceptive or that the only after a predetermined delay after its shot from the transmission mode within the time period Δ t Transd men and preferably configured as omnidirectional transmitters.