Radar anti-jamming technology

(I) to Radar Electronic Reconnaissance and Radar Anti-Reconnaissance Technology

The electronic reconnaissance of electronic warfare to radar includes: radar intelligence reconnaissance, radar countermeasure support reconnaissance, radar homing and warning, guided jamming, and radiation source positioning.

The main anti-reconnaissance measures of radar: design a low probability of interception radar, control the start-up time of radar, control the operating frequency of radar, the activation of covert radar and new radar must be approved, timely replacement of radar positions that may be known by the enemy, installation of false radar, and emission of false radar signals.

(II) electronic interference

Radar jamming refers to the use of radar jamming equipment to transmit jamming electronic waves or to use materials that transmit, scatter, attenuate, and absorb waves to reflect or attenuate radar waves, thereby disturbing the normal enemy radar or reducing the effectiveness of the radar.

Radar interference can cause the enemy's radar blindness, making it unable to find the target or cause interpretation errors, and unable to correctly implement warnings; in addition, it can also cause radar tracking errors, making the weapon system out of control and unable to exert its power normally.

(III) Radar Jamming Technology

1. Antenna aspect

A. When a long-range jammer interferes with the radar, if you try to maintain a very low antenna sidelobe, you can prevent the interference capability from entering the radar receiver through the sidelobe.

B, the use of narrow antenna beam bandwidth, the use of high-gain antenna to focus on the target, and "penetration" interference.

C, the use of random electronic scanning to prevent spoofing jammers and antenna scanning synchronization.

D. Sidelobe cancellation techniques are used to suppress high duty cycle and noise-like interference entering through antenna sidelobes.

2. Transmitter

It is mainly to properly use and control the power, frequency and waveform of the transmitted signal.

A, increase the effective radiation power

This is a powerful measure against active interference, which can increase the signal/interference power ratio. If the antenna is combined with the "spotlight" illumination of the target, the detection range of the radar at this time can be significantly increased. Power management is used in radar emission to reduce the probability of radar reconnaissance.

B. emission probability

Frequency agility or frequency diversity can be used in the probability of transmission. The former refers to the change of transmission frequency between pulse and pulse or pulse train and pulse train, and the latter refers to the comprehensive utilization of several radar transmitters working at different frequencies. These techniques represent a spread spectrum electronic anti-jamming method, the transmitted signal will be as wide as possible in the frequency domain to reduce the detection of the enemy reconnaissance, and increase the load of the enemy's electronic interference and make the interference more difficult.

C, transmit waveform coding

Waveform coding includes pulse repetition frequency hopping, scrambling and coding, and inter-pulse coding. All of these techniques make spoofing more difficult because the enemy will not be able to learn or predict the exact structure of the transmitted waveform.

Intra-pulse coding can compress complex signals, which can effectively improve the target detection ability. It has a large average power and peak power is small; its wide bandwidth can improve the range resolution and can reduce the reflection of chaff passive interference; because of its low peak power, the radiation signal is not easy to be detected by enemy electronic support measures. Therefore, the pulse compression radar using such complex signals has better electronic anti-reactance performance.

3, with the receiver, signal processor related to the electronic anti-interference.

A. Receiver anti-saturation

If the interference remaining after the antenna anti-interference is large enough, it will cause the saturation of the receiving processing system. Receiver saturation will result in loss of target information. Therefore, according to the use of radar to develop mainly for anti-jamming gain control and anti-saturation circuit. The wide-limit-narrow circuit used is a special circuit mainly used for anti-sweep interference to prevent receiver saturation.

B. signal identification

An effective measure against pulse interference is the color page pulse width and pulse repetition frequency discrimination circuit. After measuring the width and repetition frequency of the received pulse, if the parameters of the signal are found to be different from those of the transmitted signal, they will not be allowed to reach the signal processing equipment or terminal display.

C. Signal processing techniques

Modern radar signal processing technology has been relatively perfect, such as used to eliminate ground and cloud and rain clutter moving target display and moving target detection, for the elimination of chaff and other interference is equally effective. In addition to the above-mentioned coherent processing, the constant false alarm rate circuit of non-coherent processing can reduce the effect of interference by increasing the detection threshold. The signal accumulation gain obtained in the signal processor is an effective means of electronic anti-jamming.