antijamming

Antijamming refers to techniques and systems designed to preserve the performance of communications and navigation links in the presence of interference that is accidental or deliberate. Jamming can be broadband or narrowband, continuous or intermittent, and can target the RF carrier, the data link, or the processing chain. Common forms include noise jamming, deceptive jamming, spot jamming, sweep jamming, and barrage jamming.

Anti-jamming approaches are categorized as resilience, mitigation, and deception. Resilience techniques aim to maintain signal detectability under interference, including increased transmit power, robust modulation and coding, interleaving, and forward error correction. Mitigation techniques reduce the interference impact at the receiver, such as spectrum shaping, adaptive filtering, power control, and interference cancellation. Spread-spectrum methods, notably direct sequence and frequency hopping, spread the signal over a wide bandwidth, reducing the jamming impact. Antenna techniques, including directional antennas, beamforming, and null steering, physically suppress jammers. Receiver design focuses on high dynamic range, jamming detection, and rapid mode switching between bands or codes. In navigation systems, anti-jamming includes multi-constellation receivers, joint processing of multiple signals, and time-domain or angle-domain interference excision.

Applications appear in military and civilian domains, including GPS and other GNSS, satellite and terrestrial wireless networks, and aviation. Performance is evaluated with metrics such as carrier-to-jammer ratio, jammer efficiency, and effective data rate under interference. Challenges include adaptive adversaries, realistic channel conditions, and regulatory limits on transmit power. Historical roots lie in early radio communications, with modern systems relying on spread spectrum and smart antennas to enhance resilience.