The electronic offensive and defensive confrontation of modern warfare has long been dominated by electronic warfare. If radar is to be effective in an increasingly advanced and complex electronic offensive and defensive confrontation, it must find a breakthrough in its basic principles and system, and must have effective electronic anti-jamming and electronic defense measures. Therefore, new radars such as sparse array integrated aperture radar and passive anti-stealth radar have emerged one after another, and have been significantly developed. The new principle of radar makes the aircraft difficult to detect, unable to locate, unable to interfere, and locked by rigidity.
Sparse array radar.
1: Sparse array integrated pulsed aperture meter-wave radar (SIAR).
Many research results show that radars with long wavelengths, such as meter-wave radar, are direct and effective methods for dealing with stealth technology and anti-radiation missiles, but the Achilles' heel of meter-wave radar is the poor angular resolution. Sparse array integrated pulse aperture radar (SIAR) is a new type of meter-wave distributed array radar, which is mainly used for long-range warning and tracking. It retains the traditional advantages of meter-wave radar and overcomes the main shortcomings such as low angular resolution, poor measurement accuracy and weak anti-jamming ability. The main feature of SIAR radar is that the antenna adopts a sparse array, generally non-directional reflection, and its transmit and receive patterns are obtained at the receiving end through digital signal processing, so it can form multiple beams at the same time to observe multiple directions at the same time. Because it does not use traditional mechanical antennas to scan space beams, it can form a beam by calculating and forming a long-term uninterrupted staring at the target for a long time and carry out long-term coherent accumulation, which improves the radar's detection ability and radar's four anti-anti capabilities (i.e., anti-stealth technology, anti-reflection missile, integrated electronic anti-jamming and anti-low-altitude penetration technology).
B2 strategic bomber.
1.1. Rarefied antennas
Meter-wave radar to obtain high angular resolution, the antenna aperture of the radar must be very large, generally 100 meters even if it is fixed is very large, so often use sparse array antennas, sparse array with a few units can get a narrow beam, which is at a cost, its side lobes will be improved and energy utilization rate will decrease. Taking the linear array with the array element n as an example, if the wavelength of 1 2 is equally spaced sparse array antenna, the gain is unchanged and the beam width is (n-1) 2, if the interval is increased k times, the gain of the equidistant sparse array antenna is unchanged, and the beampower is compressed to k, and there will be a lobe as high as the main lobe, which is not allowed. The irregular arrangement of several new radars that are difficult to interfere with by array elements can reduce the grating lobe under the premise that the main beam index does not change much, and the grating lobe radiation is dispersed into the side lobes and the sidelobe level is increased. The problem of high sidelobes can be solved by combining the multiple properties of the system.
Meter-wave phased array radar
1.2 How it works:
The antenna system of SIAR radar is composed of M (25) transmitting antenna elements and M (25) receiving antenna elements evenly distributed in two circles, wherein the excitation signal is a pulse with a certain width of a certain value, which adopts a group of orthogonal bases with a cross-scatter variation as the modulated signal of multi-frequency transmission, and then becomes a signal of different carrier frequencies and is assigned to each transmitting element after being used. When the signals emitted by each array element are orthogonal to each other, the non-directional emission of the radar antenna is formed. Each receiver converts the radar echo signal into a digital signal and sends it to the central processing station. The central processing station forms the corresponding receiving beams of the signals from each receiver. The MTI filter is then formed by the output connection of the receive beam, the purpose of which is to suppress most of the clutter of the clutter. The matching processor of the transmit beam of the MTI output panel performs N transmit signal separation, phase adjustment, and summation processing. After the matching process, the coherent accumulated Doppler filter is used to further improve the signal-to-noise ratio and determine the radial velocity of the target.
YLC-8B radar
1.3 SIAR radar performance characteristics: sparse array integrated pulse aperture radar is a kind of radar with good low intercept probability performance. Its main performance has the following four characteristics. (1) The SIAR radar adopts an omnidirectional emission mode, and there is no distinction between the main lobe and the side lobe of the transmitted radar waveTherefore, the reconnaissance and receiving equipment of the other side cannot obtain radar information from the main beam and roughly locate the radar. (2) SIAR radar can do long-term coherent accumulation, which is required for the same operating distanceThe transmitting power of the radar is small, and if a large time-wide product signal is used, its average radiated power can be smaller, so its concealment is better and it is not easy to be reconnoitred
SLC-7 multifunctional radar
3) SIAR radar is an active array radar, and the phase coding and frequency coding of the signal emitted by each array element are different and can change randomly, which is a complex waveformTherefore, the enemy cannot use signal processing means to obtain the transmitted beam, and it is difficult to locate the radarIt is difficult to obtain more detailed radar waveform parameters, so it is impossible to implement effective dry reactance on them.
4) SIAR radar works in ultra-wide band mode, the bandwidth can be very large, in different repetition cycles, can achieve 1 2 octave frequency hopping workFor example, the center frequency can jump from 100MHz to 300MHz to work, making it difficult for enemy radar reconnaissance equipment to detect the frequency used by radar.
F35** fighter.
2: Passive anti-stealth radar.
2.1. When ordinary radar discovers targets such as aircraft, the target is confirmed by the echo signal formed by the radar receiver receiving the transmitted signal and the reflection of the target. The first aircraft is to reduce the cross-sectional area of the target radar by taking various measures to reduce the signal received by the radar to achieve the purpose of target stealth. The new passive anti-stealth radar adopts the theory of blind signal processing. Using blind signal processing technology, the air noise caused by the aircraft in flight is directly collected as an observation measurement without active transmission, and then the target is locked through computer algorithm processing, which can not only not expose its own position, but also clearly and stably track the aircraft.
Our YLC-29 passive anti-stealth radar
2.2 Status quo. It took nearly 20 years for the American company Loma to successfully develop the "Silent Sentinel Passive Surveillance Radar System." The system is to establish a basic database of U-V-band television signals and civil FM stations in the area to be monitored, and as long as more than three television or radio signals reflected by the target are received by the system, according to the principle of coherence of radio waves, it can accurately detect and track targets such as flying objects in flight. Television broadcasts are ubiquitous in space, so they can be used anywhere in the world. A typical configuration of a "Silent Sentinel" system includes a high-sensitivity receiver, processor, visualization software, and analysis software, ranging from $3 million to $5 million per set.
The YLC-29 passive anti-stealth radar is a bistatic radar
2.3. Performance characteristics.
The new passive anti-stealth radar itself does not emit radio waves like radar, but uses the continuous wave carrier frequency (50 800 mh) of civil radio and television signals and the envelope on these stable carrier signals to provide a distinguishing feature for measuring the arrival time difference between the direct signal and the reflected signal. Therefore, it has a good anti-radiation missile (ARM) attack ability and self-protection ability. Key to the new Silent Sentinel technology in the United States is a large dynamic range digital receiver, phased array antennas, a powerful commercial computer from Silicon Graph (SGI) (parallel processing speed of several dry megafloating-point operations per second), and innovative software and algorithms from Automated Advanced Products (AEP) (including a three-dimensional terrain database that allows the operator to select a transmitting station with the best geographic coverage and a clear line of sight in the area of interest). In the processing algorithm, the angle of arrival, time delay and Doppler frequency shift information of the signal are used to locate the target.
Sparse array radar.
China began to study passive anti-stealth radar at the beginning of the century, and after more than 10 years of efforts, in-depth research has been carried out on the theory and application of blind signal processing, and a series of innovative achievements have been made, and there are products that can be used. In addition, a series of innovations have been made in the development of sparse array integrated pulsed aperture radar, and at present, China has reached or approached the world's advanced level in the new system of radar.
Of course, the sparse array radar also has its own shortcomings, first of all, the radar antenna is more, the equipment is more scattered, the whole system covers a large area, so it is easy to be detected and attacked by the other side, the battlefield survivability is lower than the conventional radar, in addition, the system has higher requirements for the signal data processing system, the radar principle and technology are still developing, and further technical research is needed, so the sparse array radar is generally mixed with conventional radar to form a comprehensive radar detection system to improve the detection ability of the entire radar network. After the successful development of the sparse array radar, the ability of China's air defense radar network to fight stealth targets has been effectively enhanced, especially stealth fighters such as the F-22
As we all know, the F-22 has supersonic cruise capability, and the exposure time in the radar network is reduced, which further reduces the detection efficiency of the opponent's radar At the same time, it can also provide F-22 accurate target information, so that it can provide better command and guidance for our fighters, and can intercept them at a greater distance. Looking forward to the future, I believe that with the unremitting efforts of China's radar technicians, China will achieve more brilliant results in the field of anti-stealth radar, launch more advanced anti-stealth radar, and better defend the safety of national airspace.