The principle of DRFM for radar jamming
The principle of the radar's work is that it transmits a radar pulse to the target. This pulse collides with the target and then is reflected back to the radar. The radar receives the reflected pulse, and by analyzing it, it can identify the presence of a target in its area.. Then it begins to measure the distance between it and the target by calculating the time taken by the radar pulse from its launch until its reflection and return again to the radar.. The timing difference of receiving pulses is the main element on which the DRFM technology is based on for radar jamming. DRFM receives the original radar pulse emitted by the hostile radar and then works to determine its data in terms of its frequency, wavelength and timing difference between it and the previous and next pulse.
After obtaining this data, DRFM begins to prepare a set of radar pulses that correspond to the original radar pulse, and here the whole idea on which its work revolves. The only thing that DRFM can change about a radar pulse is the pulse timing, or the reception timing difference between the pulses.
A DRFM, or digital radio frequency memory system performs real-time processing of received signals, typically radar, by digitizing, processing and transmitting an adversary’s radar pulses, a DRFM can deceive the radar system, which is especially critical to protect against radar-guided missiles. Typically, DRFM systems consist of broadband RF hardware, high-speed digitization modules and low-latency FPGA processing boards.
Therefore, each pulse of the spoof group cloned by DRFM will be interpreted as an additional air target by the hostile radar that matches the original target in the radar fingerprint. Moreover, each spoofed pulse has its own pulse timing. Thus, the hostile radar will translate every fake pulse as a hostile target that is different from the other in terms of speed, including the real target, which will be difficult to identify in the midst of this number of fake targets. Then the fake data comes in terms of speed and range to increase the complications..
The design of the DRFM system dates back to the seventies of the last century when one of the designers published a research paper in one of the specialized journals explaining a new method of jamming based on digital storage and copying, and this was the beginning of a new revolution in the world of electronic warfare. This new system provided an advantage that no systems before it had.
The systems that were common at the time were all operating in the manner of noise jamming, and these systems have the problem that they reveal themselves and the location of the aircraft in some cases. As soon as the aircraft jams the radar, dots or lines will appear on the operator screen and immediately the crew will know that the radar is subjected to hostile interference and will change its radar frequencies for the purpose of breaking the interference or use other methods to get rid of the interference and often jamming systems that have not been carefully designed will reveal their location due to the appearance of a parallel line on Radar screen and this line is what determines the direction of the source of interference.
There was also a bigger problem represented by the emergence of new systems of air defense and air-to-air missiles, which contain a Monopulse radar. These radars can lock on the source of interference and determine its exact location, just as the air-to-air missiles that use this type of detector automatically lock on the noise source.. Therefore, the disturbances became a real suicide.
From the seventies to the early nineties, no country thought to implement this idea, but the United States first took the initiative to apply this idea to the ALQ-165 jamming system because it had the necessary technical expertise and because this technology required a design based on digital memory and random access memory, which was not mature at the time and quickly this system became the best and most powerful system at the time, Hence global demands have poured on it.
The way this system works is very simple. It monitors the enemy’s radar signal and classifies it according to its library of frequencies. And if it is a hostile radar, it analyzes the signal, frequency, Doppler frequency and Phase, and then performs the conversion process to the baseband. This results from Phase and squaring the wave in Unit I and Q and then the conversion From analog to digital ADC and store it in a memory bank, then do a process of converting from digital to analog DAC with adding adjustments such as time delay and adding a simple energy to the previous pulse train and then send it to the local oscillator LO for the purpose of sending it. The end result is a highly effective receiver and transmitter system. After detecting and analyzing the enemy’s radar wave, the system sends the same wave, the same frequency, and almost the same phase, but with some time delay, and sends it to the enemy’s radar. Because the radar depends mainly on sending the wave and then receiving and analyzing its arrival time for the purpose of knowing the range, The DRFM system works on the same principle as it sends to the radar a signal with the same frequency, phase and characteristics, so it won't be able to differentiate between the original and the spoofed signal, and because the jamming system has a time delay, the spoofed signal will appear in the form of a false target with a false range. Some DRFM systems distort the transmitted signal further by creating a false target with a false range and false angle, and the radar operator can see the enemy aircraft that is 12 km away from him at a range of 120 km and an angle of 10 km.
The design of DRFM systems is characterized by the fact that it depends on the transmission of the exact signal, meaning that the radar will not differentiate between them and will not know that they are misleading. Therefore, no indications that it is subject to interference and no jamming field line will appear on the radar screen. Monopulse systems and detectors will not be able to lock it as in the case of noise jamming systems Because it does not emit any radio emissions of high energy or raise doubts in the radar receiver..
The system has become popular at the global level and is considered the most dangerous among all jamming systems. All modern advanced systems, such as the Spectra jamming system of the Rafale, the Barracuda system for the F-35, the ALQ-126B and ALQ-214 system of the Super Hornet, DEWS of the Silent Eagle, the Saudi and Qatari versions of the F-15E, and the jamming system DASS of the Eurofighter Typhoon and the Russian Khibini system on the Russian Sukhoi-35 and Sukhoi-34 fighters, all of them use the DRFM method of jamming, and there are advanced Chinese, Israeli, Italian and Spanish systems that use this technology. The F-35 fighter is the best in terms of investing in this technology because it contains dozens of methods For jamming and deception, it is able to literally deceive the radars of the S-400 system because it uses a combination of AESA active arrays with FPGA programmable gates that allow for very long range beam formation with very high speed of response, beamforming and delay.. and can generate false targets of real nature and can keep the aircraft hidden from the radar screen using the feature of
Active Cancellation or the deployment of hundreds of false targets on the enemy's radar screen.. It is one of the most dangerous systems in the world..
Source: Different sources
