Hello everyone, welcome back to the new post today. Smart jammers, also known as misleading jammers or digital radio frequency memory (DRFM) jammers, are commonly utilized in national defense to confuse enemy radars and safeguard their own sites.

Smart jammers, also known as misleading jammers or digital radio frequency memory (DRFM) jammers, are commonly utilized in national defense to confuse enemy radars and safeguard their own sites.

DRFM technology entails sampling an RF signal, storing and restoring it digitally, and modifying some or all of the signal's properties according to the spoofing technique.

The DRFM system digitizes the received RF signal at the proper frequency and bandwidth, then recreates the RF signal as needed. The most crucial feature of DRFM is that it overlaps with the received signal as a digital "copy." It continuously cyclically repeats the energy of the front-end amplifier without generating signal deterioration, providing a larger spectrum of interference effects than analog circuits.

Ⅰ. Typical Characteristics of DRFM System

Can generate the RF signal's coherent time delay (usually in radar applications)

To the enemy's radar system, create cohesive deception jamming (intelligent jamming):

With a brief delay, the captured radar pulse can be replayed.

Changes in the fake target's latency can cause it to appear to be moving.

Other interference effects can be created by modulating the amplitude, frequency, and phase of the collected pulse data.

The range and range rate trackers in the radar are correlated by increasing the Doppler frequency shift.

Multiple replays of the collected pulse can result in a large number of false targets.

From files, DRFM may generate arbitrary waveforms.

When dealing with radar that uses linear frequency modulation, use DRFM jammers (LFM)

Ⅱ. Continuously Evolving DRFM Interference Technology

Modern DRFM features include a smaller compact, faster reaction, and a huge amount of low-latency computing power. The superheterodyne receiver's core is DRFM. The jammer system's core structure is made up of it. Narrowband signals must be processed at the same time in the jammer system to avoid interference.

DRFM has a complicated programming function (based on the digital signal processing technology generator) that can make many false echoes with complex kinematics rules and waveform synthesis, and it can realize coherent technology (coherent copy of the received signal).

Coherent replication entails using the same threat radar signal as the seed of the jamming signal, resulting in the jamming signal being undetectable from the real echo and being processed with the same processing gain (increased J/S ratio).

Coherent copies are used in spoofing technology to adjust the distance between two points by transmitting pulses with various delays relative to the real echo (distance door extension/closer) or sending relative to the real echo (speed door extension/reduction). To modify the speed, a signal with variable Doppler frequency shift is used.

The signal in DRFM can also be utilized as a noise modulation seed. The noise is thus tailored to the radar instantaneous frequency bandwidth or Doppler bandwidth in this manner. The goal of this technology is to minimize the enemy by producing a noise Doppler frequency band that is centered on the target's true Doppler (for example, shielding the speed gate of the semi-active seeker). The ability of square radar to detect and track the target's Doppler.

Instead of utilizing a locally synthesized radio frequency carrier (non-coherent noise), using the received and stored signal as a radio frequency carrier (creating coherent noise) can improve the performance of interference noise and better match the radar bandwidth (this is for relative noise). Participation in the radar is quite crucial).

When interference is added, interference noise performance is defined as a reduction in the global signal-to-noise ratio (S/(N+J)), which is dependent on the matching between the interference signal and the true echo (how many interference signals can enter the radar matching bandwidth The processing gain of the radar is obtained within) and how much noise characteristics can be assumed to be similar to thermal (Gaussian) noise.

The noise quality index (NQI) is determined by the Gaussianity of interference noise and the ratio of interference bandwidth to radar matching bandwidth (good noise quality is obtained when the ratio factor of the minimum interference BW to the radar BW is 3).

In order to achieve the goal of tuning the interference carrier to the threatening radio frequency range, or to perform coherent interference, continuous noise generation in the forwarding mode necessitates regular switching of transceivers to receive, store, and process the interference carrier (coherent interference) before transmission. receives the signal

Naturally, if the pulse properties do not vary over time, previous pulses can be used to construct the present coherent duplicate. If the pulse characteristics vary, all pulses must be received; however, if the jammer obtains the complete pulse, it cannot be broadcast during the reception and acquisition phase, therefore it is impossible to construct a false target that is closer than the pulse width.

Ⅲ. Slice Transponder

The slice transponder is also a coherent DRFM function mode that may rebuild the coherent interference copy using only a tiny portion of the received signal (slice). Only a limited amount of time will be allowed to be received and delivered before the end of the received pulse: only one RX and TX switch will be conducted within the pulse.

This technology enables coherent acquisition and replays operations to generate copies with high phase and frequency coherence, ensuring that the radar receiver has adequate correlation (in the case of radar-matched filtering).

Ⅳ. Usage of Misleading Jammers

The DRFM jammer has evolved into an important component of a complex electronic attack (EA) package. It has progressed from a simple forwarding system with limited attenuation to a powerful electronic attack weapon.

DRFM can be used to verify the system-level spoofing technology's accurate operation and timing, to test various components, sub-modules, and modules at the RF/IF level, and to guarantee that clock jitter and power integrity issues are rectified early on.