India Bets on L-Band, GaN and Cognitive Processing to See Through the Hypersonic Plasma Sheath

DRDO Developing L-Band AI Radar Tech to Penetrate Plasma Shields of Maneuvering Hypersonic Missiles | Defence News India

DRDO's Electronics and Radar Development Establishment is converging an indigenous AESA architecture, adaptive signal processing and reinforcement-learning waveform selection on a problem the U.S. and Russia have wrestled with since the 1960s — tracking a maneuvering target shrouded in its own ionized wake.

Aerospace & Defense — Sensors and Electronic Warfare

BLUF — 

India's Defence Research and Development Organisation (DRDO) is accelerating a multi-strand effort, led by its Electronics and Radar Development Establishment (LRDE) in Bengaluru, to give the country's Integrated Air Defence System a credible track-and-engage capability against hypersonic glide vehicles (HGVs) and maneuvering hypersonic cruise missiles. The program rests on four convergent technical bets: a shift to longer-wavelength L-band Active Electronically Scanned Array (AESA) radars to defeat plasma-induced attenuation; indigenous Gallium Nitride (GaN) transmit-receive modules to deliver the radiated power needed to "burn through" the residual sheath; Space-Time Adaptive Processing (STAP) to discriminate a missile body from its ionized wake; and reinforcement-learning-based "cognitive radar" waveform selection — work that DRDO has acknowledged funding in open-literature publications. The effort is being spun in parallel with Phase-II BMD interceptor fabrication (AD-1, AD-2) and conceptual work on Phase-III dedicated anti-hypersonic interceptors (AD-AH, AD-AM). The driver is unambiguous: People's Liberation Army Rocket Force (PLARF) operational deployment of the DF-17/DF-ZF and a growing family of Chinese hypersonic anti-ship systems (YJ-17/19/20/21), against the backdrop of reported negotiations to transfer DF-17 technology to Pakistan. Operational fielding of the new sensor architecture is unlikely before the end of this decade; the AD-AH/AD-AM interceptors are projected by DRDO to begin developmental trials no earlier than 2030.

The Physics: Why X- and S-Band Are Compromised

At sustained Mach 5-plus inside the atmosphere, the bow shock and viscous heating ahead of an aerodynamic vehicle dissociate and ionize the surrounding air, producing a plasma sheath whose electron number density routinely exceeds 10¹³ cm⁻³.¹ When the local plasma frequency exceeds the incident electromagnetic wave frequency, conventional cold-plasma theory predicts that the wave is reflected or strongly attenuated rather than transmitted — the "blackout" regime familiar from Mercury, Gemini and Apollo reentries and characterized in NASA's Radio Attenuation Measurement (RAM-C) flight tests beginning in 1960.²

For a hypersonic glide vehicle, plasma frequencies in the stagnation region can reach tens of GHz, which is squarely within the operating bands of conventional fire-control and tracking radars. A 2024 ScienceDirect study of HTV-2-class boost-glide aerodynamics computed plasma frequencies "up to tens of GHz" in regions close to the body, with markedly lower interference in the extended ionized wake.³ An open-literature 2025 paper in Physics of Plasmas on hypersonic communications confirmed that even when signals do penetrate the sheath, time-domain effects — sampling-time offset, envelope broadening, frequency-selective fading, and inter-symbol interference from delay spread — corrupt the returns enough to break tracking continuity.⁴ The University of Notre Dame's Hypersonic Systems Initiative summarizes the operational consequence cleanly: "Electromagnetic radiation under normal non-magnetized conditions cannot penetrate thick plasma layers where the plasma frequency is greater than the electromagnetic wave frequency. The signal is instead reflected."⁵

The relevant takeaway for an air-defense radar designer is asymmetric: lower-frequency interrogating waves are less attenuated by a given plasma density than higher-frequency ones, but they pay for that with reduced angular resolution and larger antenna apertures. That is the trade-space LRDE is now optimizing.

LRDE's Architecture: Four Convergent Technical Bets

Frequency selection — L-band as the floor. Indian Defence Research Wing (IDRW) and the trade outlet defence.in reported in late November 2025 that LRDE is structuring its anti-hypersonic radar program around a shift to L-band (1-2 GHz) AESA architectures, on the grounds that L-band's longer wavelengths are "significantly less vulnerable to plasma absorption" than the X- and S-band sensors that populate India's existing fire-control inventory.^6,7 This is not a clean-sheet design philosophy but a deliberate inheritance from India's two-decade-old Long Range Tracking Radar (LRTR / "Swordfish") program, an L-band AESA derivative of Israel Aerospace Industries' EL/M-2080 Green Pine that has formed the long-range sensor of India's BMD Phase-I shield since the late 2000s. The Swordfish operates at 1-2 GHz with a 600-800 km baseline range against a 0.25 m² target, upgradeable to 1,500 km in the LRTR-II "Super Swordfish" configuration.⁸

Power and efficiency — indigenous GaN T/R modules. The second leg is a hardware leap from Gallium Arsenide (GaAs) to Gallium Nitride (GaN) transmit-receive modules. DRDO confirmed in February 2026 that India had become only the seventh country with sovereign GaN MMIC fabrication capability, attributed to work led at the Solid State Physics Laboratory after France declined to transfer the technology under the Rafale offset clause.⁹ GaN's relevance to the hypersonic-tracking problem is that higher power density and better thermal handling allow an L-band aperture to project enough effective radiated power to overcome residual two-way attenuation through a thinned wake region — the "burn-through" approach. DRDO's Very Long Range Radar / Very Long Range Tracking Radar (VLRR/VLRTR), unveiled in August 2025 as a fully indigenous GaN-AESA system in L-band for BMD Phase-II, is the most direct production embodiment of this approach.¹⁰ A separate L-band Long Range Radar (LRR), with all subsystems integrated at a designated test site, was announced in November 2025 and is described by DRDO as designed for detection of "small radar cross-section (RCS) and high-speed aerial targets" with GaN T/R modules.¹¹

Signal processing — STAP for body-from-wake separation. The third leg, repeatedly cited in open-source coverage of the LRDE program, is Space-Time Adaptive Processing. STAP — long familiar to the GMTI/AEW community — is being adapted here to discriminate the coherent return from the metallic missile body against the turbulent, time-varying plasma wake trailing it. The wake itself is not silent: it produces a measurable, plasma-frequency-dependent return that conventional tracking algorithms can mis-resolve as multiple closely-spaced targets ("ghosts") or smear into an unresolvable centroid. STAP's role is to filter the wake clutter as a structured, partially predictable interference rather than as random noise.^6,7

Cognitive radar — adaptive waveform selection in the loop. The fourth leg is the most forward-leaning, and the most directly traceable to a DRDO funding line in the open literature. An October 2024 arXiv paper, "Online Waveform Selection for Cognitive Radar", explicitly acknowledges DRDO and the Indian Ministry of Defence as the funders, and applies reinforcement-learning techniques — bandwidth scaling, Q-learning, and Q-learning-with-lookahead — to the problem of tracking a ballistic trajectory across boost, mid-course, and terminal phases without losing track. The paper finds that bandwidth selection has a larger impact than pulse repetition frequency on the joint range-error / track-continuity trade-off, and that reinforcement-learning approaches generalize across trajectories without per-trajectory tuning.¹² The broader cognitive-radar literature — formalized in the NATO SET-227 task group and Haykin's 2006 IEEE Signal Processing Magazine framing — describes a perception-action cycle in which the radar transmitter actively varies frequency, waveform shape and dwell time on each look, learning from echoes how to interrogate the next look.¹³ Applied to a plasma-shrouded HGV, this allows the radar to "hunt" for the local frequency window where the sheath is thinnest, rather than transmitting a fixed waveform optimized for an average case.

Threat: Why Now

India's urgency tracks the maturation of regional adversary inventories. The CSIS Missile Threat Project assesses the DF-17 — first publicly paraded by the PLA Rocket Force on October 1, 2019 — as a 1,800-2,500 km solid-fueled medium-range system carrying the DF-ZF HGV at terminal speeds of Mach 5-10.¹⁴ The DF-ZF entered PLARF service in 2020, and per Wikipedia's December 2025 entry, "skips along the earth's atmosphere, allowing it to go undetected by radar for longer distances than a ballistic missile covering the same distance".¹⁵ A September 2025 Beijing Victory Day parade unveiled three additional anti-ship hypersonic types — the YJ-17 (boost-glide waverider), the YJ-19 (scramjet-powered air-breathing waverider) and the bi-conic boost-glide YJ-20 — joining the operational YJ-21.¹⁶

Of more immediate concern to South Block, an Insightful Geopolitics analysis published in June 2025 reported that Pakistan has entered "early stages of negotiations with China to acquire advanced hypersonic missile technology, specifically the DF-17 system integrated with the DF-ZF Hypersonic Glide Vehicle," reportedly bundled with J-35A fighter access in exchange for a Chinese military presence at Gwadar.¹⁷ Independent of the China track, India's own May 2025 Operation Sindoor exchange — in which the BEL-built AkashTeer automated air-defense control and reporting system was credited by the Indian government with intercepting a barrage of Pakistani drones and Fatah-series rockets — established the political baseline that the Integrated Air Defence Network is now treated as a tested, deployable capability rather than an aspiration.¹⁸ AkashTeer's role in the LRDE radar program is as the fusion layer: the new L-band sensor is being designed to feed the same Joint Air Defence Centre (JADC) that already aggregates Army (AkashTeer), IAF (IACCS) and Navy (Trigun) tracks.¹⁹

Program Architecture: Sensor Tied to Interceptor

The radar program is meaningless without a kinetic effector at the end of the kill chain, and DRDO has structured BMD Phase-II and a conceptual Phase-III to provide one. Phase-II rests on the AD-1 (in limited serial production since 2025, capable of Mach 6-7 endo- and low-exo-atmospheric intercept against targets in the 5,000 km class with a demonstrated, if limited, secondary capability against HGVs in the terminal phase) and the AD-2 exo-atmospheric interceptor, fabrication of which is reported to be advancing toward first developmental trials.^20,21 Phase-III, formally described in a January 2026 piece in The Defense Post, comprises two dedicated anti-hypersonic interceptors: the AD-AH (against HGVs) and the AD-AM (against hypersonic cruise missiles). Wind-tunnel models of the AD-AH were displayed at DRDO's Hyderabad hypersonic test facility in late 2024; developmental testing is projected to begin "from 2030 onwards".²²

India's parallel offensive hypersonic effort — relevant here because it generates the test-article corpus on which the new radar must train — passed a watershed on November 16, 2024, when DRDO conducted what the Press Information Bureau described as the country's first long-range hypersonic flight trial from Dr. APJ Abdul Kalam Island.²³ The vehicle, since identified as the Long Range Anti-Ship Missile (LRAShM, designation LR-02 in the November test), is a delta-wing boost-glide weapon credited by DRDO sources with reaching Mach 10 in flight test, and was publicly displayed for the first time at the January 26, 2026 Republic Day parade.^24,25 DRDO Chairman Samir V. Kamat told Indian media in mid-2025 that LRAShM trials would conclude within two-to-three years.²⁶

What Has Been Demonstrated, What Has Not

Open-source reporting on LRDE's hypersonic-tracking effort divides cleanly into three confidence tiers, and Aviation Week readers should weight them accordingly.

Hardware that has been publicly fielded or formally announced as integrated includes the Swordfish/LRTR L-band AESA (operational, BMD Phase-I), the indigenous GaN VLRR/VLRTR L-band AESA (announced August 2025, testing into 2026 with subsequent BMD Phase-II integration), and the LRR — also L-band, GaN-based, with all subsystems integrated at a test site as of November 2025 and described as designed for "small RCS and high-speed aerial targets".^10,11

Capabilities described in DRDO-funded research but not announced as fielded include the reinforcement-learning waveform-selection methods of the October 2024 arXiv paper.¹² These are, properly, algorithm research; their integration timeline into a deployable LRDE radar is not in the open record.

Capabilities asserted by Indian trade press but not independently corroborated by DRDO, the Press Information Bureau or the Ministry of Defence press release archive include the specific use of STAP for plasma-wake discrimination, the integration of "cognitive radar" mode-switching at microsecond timescales into a deployable hypersonic-tracking sensor, and the existence of a single dedicated "anti-hypersonic radar" program distinct from the broader VLRR/VLRTR/LRR family.^6,7 This distinction matters: the most plausible reading of the November 2025 LRDE announcements is that the same institution is pursuing several overlapping radar developments under the broader "see-through-the-plasma" objective, with the trade press treating the convergence as a single program. As of this writing, the DRDO and PIB official channels have not posted a release using the formulation "anti-hypersonic radar" as a distinct line item.

The Open Engineering Questions

Three engineering questions, each treated extensively in the international literature, remain unresolved in the public LRDE record.

First, the L-band-versus-resolution trade. Longer wavelengths buy plasma penetration at the cost of angular resolution; achieving the cross-range accuracy needed to hand off to a hit-to-kill interceptor at engagement ranges of several hundred kilometers will require either physically large apertures or coherent multi-radar fusion. The VLRTR's reported 3,000+ km class detection envelope implies an aperture and power budget consistent with the former.⁸

Second, the wake-versus-body discrimination problem. NASA Glenn's 2010 review of blackout-mitigation approaches notes that the densest plasma is in the stagnation region at the nose, with electron densities orders of magnitude lower along the aft body and in the trailing wake — meaning a properly geometrized illumination angle may see a substantially less obstructed body return than a head-on aspect.² STAP, properly applied, exploits exactly this geometry, but the public LRDE record contains no specifics on how the algorithm has been parameterized for the HGV case.

Third, the cognitive-radar adversarial loop. A 2018 Military Embedded Systems overview of cognitive radar/EW notes that adaptive systems face an adaptive adversary: a hypersonic vehicle equipped with a wideband-aware RF jammer, or simply with maneuver authority sufficient to vary its sheath thickness and ionization profile, can in principle outpace a learning radar's policy update.¹³ This is the unbounded version of the standard ECCM/ECM cycle, and it is genuinely unsolved at the doctrinal level — not just in India.

Outlook

The most important fact in the public record is not the radar itself but the timeline. AD-1 is in limited production. AD-2 is in pre-test fabrication. AD-AH/AD-AM testing is targeted for 2030. The L-band GaN sensor architecture is integrated and entering test. The reinforcement-learning waveform research is published in the open literature with DRDO acknowledgment. Each piece exists; the systems-engineering challenge — and India's window of relative vulnerability — is in fusing them into a closed kill chain before the DF-17 (or its potential Pakistani export variant) becomes a routine, fielded threat against Indian metropolitan areas. On current evidence, that fusion is underway, but the operational sensor is not yet a deployed capability. The plasma sheath remains, for now, a real obstacle. India's bet is that L-band power, GaN efficiency, STAP discrimination and cognitive-radar adaptivity, layered together, will reduce it to a manageable one.

References

1. Hypersonic Systems Initiative, University of Notre Dame, "Communication." https://hypersonics.nd.edu/research/communication/
2. Gillman, E. D., Foster, J. E., and Blankson, I. M., "Review of Leading Approaches for Mitigating Hypersonic Vehicle Communications Blackout and a Method of Ceramic Particulate Injection via Cathode Spot Arcs for Blackout Mitigation," NASA/TM-2010-216220, NASA Glenn Research Center, 2010. https://ntrs.nasa.gov/api/citations/20100008938/downloads/20100008938.pdf
3. "Hypersonic boost-glide systems: Flight mechanics and plasma parameters evaluation through aero-thermo-chemical computational fluid dynamics," Aerospace Science and Technology, ScienceDirect, March 2024. https://www.sciencedirect.com/science/article/abs/pii/S1270963824002256
4. "Effect of plasma sheath on high hypersonic vehicle communication systems," Physics of Plasmas, vol. 32, 073504, AIP Publishing, July 2025. https://pubs.aip.org/aip/pop/article/32/7/073504/3351797/Effect-of-plasma-sheath-on-high-hypersonic-vehicle
5. University of Notre Dame Hypersonic Systems Initiative, op. cit. (Note 1).
6. "India to Develop Radar to See Through Plasma Shield of Hypersonic Missiles," Indian Defence Research Wing (IDRW), November 2025. https://idrw.org/india-to-develop-radar-to-see-through-plasma-shield-of-hypersonic-missiles/
7. "DRDO Developing L-Band AI Radar Tech to Penetrate Plasma Shields of Maneuvering Hypersonic Missiles," defence.in, November 2025. https://defence.in/threads/drdo-developing-l-band-ai-radar-tech-to-penetrate-plasma-shields-of-maneuvering-hypersonic-missiles.17565/
8. "Swordfish Long Range Tracking Radar," Wikipedia (current revision November 25, 2025); see also GlobalSecurity.org, "Swordfish L-band Radar / Long Range Tracking Radar (LRTR)." https://en.wikipedia.org/wiki/Swordfish_Long_Range_Tracking_Radar ; https://www.globalsecurity.org/wmd/world/india/swordfish.htm
9. Pereira, N., "Aatmanirbhar Push: India Becomes 7th Nation to Crack Gallium Nitride Chip Technology," Sify, February 11, 2026. https://www.sify.com/technology/aatmanirbhar-push-india-becomes-7th-nation-to-crack-gallium-nitride-chip-technology/
10. "DRDO Unveils Indigenous VLRR/VLRTR Radar for BMD Phase-II, Matching Global Standards," IDRW, August 12, 2025. https://idrw.org/drdo-unveils-indigenous-vlrr-vlrtr-radar-for-bmd-phase-ii-matching-global-standards/
11. "DRDO Completes Integration of Long Range Radar With Indigenous GaN AESA Technology," Indian Defense News, November 2025. https://www.indiandefensenews.in/2025/11/drdo-completes-integration-of-long.html ; see also "Big Boost to Make in India: DRDO Integrates Next-Gen GaN AESA Long Range Radar System," Indian Masterminds, November 21, 2025. https://indianmasterminds.com/news/drdo-integrates-long-range-radar-gan-aesa-162047/
12. "Online Waveform Selection for Cognitive Radar," arXiv:2410.10591, October 14, 2024. (Acknowledgment: "This work was funded by DRDO, Ministry of Defense.") https://arxiv.org/abs/2410.10591 ; HTML version: https://arxiv.org/html/2410.10591
13. Fountain, T., "Improving the capabilities of cognitive radar and EW systems," Military Embedded Systems. https://militaryembedded.com/radar-ew/rf-and-microwave/improving-the-capabilities-of-cognitive-radar-and-ew-systems ; foundational work: Haykin, S., "Cognitive Radar: A Way of the Future," IEEE Signal Processing Magazine, vol. 23, no. 1, pp. 30-40, 2006.
14. "DF-17," CSIS Missile Threat Project. https://missilethreat.csis.org/missile/df-17/
15. "DF-17," Wikipedia (revision dated December 2025). https://en.wikipedia.org/wiki/DF-17 ; "DF-ZF," Wikipedia (revision dated December 2, 2025). https://en.wikipedia.org/wiki/DF-ZF
16. "China's Hypersonic Anti-Ship Missiles: Complete Inventory Analysis," The Defense Watch, November 30, 2025. https://thedefensewatch.com/military-ordnance/chinas-hypersonic-anti-ship-missiles-complete-inventory-analysis/
17. "Clear and Present Danger: Chinese Hypersonic Missiles in Pakistan," Insightful Geopolitics, June 14, 2025. https://insightful.co.in/2025/06/14/clear-and-present-danger-chinese-hypersonic-missiles-in-pakistan/
18. "Akashteer: The Unseen Force Behind India's New War Capability," Press Information Bureau, Government of India, May 16, 2025. https://www.pib.gov.in/PressReleasePage.aspx?PRID=2129132&reg=3&lang=2
19. "Akashteer," Wikipedia (current revision). https://en.wikipedia.org/wiki/Akashteer
20. "DRDO Initiates Limited Serial Production of Phase-II BMD Interceptor AD-1 Missile for Expanded Trials," IDRW, March 19, 2025. https://idrw.org/drdo-initiates-limited-serial-production-of-phase-ii-bmd-interceptor-ad-1-missile-for-expanded-trials/
21. "India's Phase-II BMD Push Gains Momentum With AD-2 Interceptor Closing in on Key Milestone," IDRW, February 19, 2026. https://idrw.org/indias-phase-ii-bmd-push-gains-momentum-with-ad-2-interceptor-closing-in-on-key-milestone/
22. Encarnacion, E. M., "India Targets Hypersonic Weapons With New Interceptors," The Defense Post, January 23, 2026. https://thedefensepost.com/2026/01/23/india-hypersonic-weapons-interceptors/ ; "Next-Gen BMD in Focus as DRDO Accelerates AD-AH and AD-AM Interceptor Development for Hypersonic and MIRV Threats," IDRW, January 21, 2026. https://idrw.org/next-gen-bmd-in-focus-as-drdo-accelerates-ad-ah-and-ad-am-interceptor-development-for-hypersonic-and-mirv-threats/
23. "DRDO carries out successful flight-trial of India's first long-range hypersonic missile off the Odisha coast," Press Information Bureau, Government of India, Release ID 2073994, November 17, 2024. https://www.pib.gov.in/PressReleasePage.aspx?PRID=2073994
24. "Long Range – Anti Ship Missile (India)," Wikipedia (current revision). https://en.wikipedia.org/wiki/Long_Range_–_Anti_Ship_Missile_(India)
25. "India's New Hypersonic Anti-Ship Missile Shown Off During Military Parade," The War Zone (TWZ), January 26, 2026. https://www.twz.com/land/indias-new-hypersonic-anti-ship-missile-shown-off-during-military-parade
26. "DRDO Chief Announces LRAShM Hypersonic Missile Trials to Conclude in 2-3 Years," IDRW, December 17, 2025. https://idrw.org/drdo-chief-announces-lrashm-hypersonic-missile-trials-to-conclude-in-2-3-years/

Editor's note: This article relies on a mix of primary sources (DRDO/PIB official releases, peer-reviewed plasma-physics literature, NASA technical reports, the cited DRDO-funded arXiv paper) and Indian trade press (IDRW, defence.in, The Defense Post, TWZ). Where specific technical claims — particularly regarding the integration of STAP and cognitive-radar modes into a deployable LRDE sensor — appear only in trade press without DRDO/PIB corroboration, that asymmetry is flagged in the body of the text. No DRDO press release using the formulation "anti-hypersonic radar" as a distinct program line has been published in the open record as of this writing. Aviation Week house style: program designations on first reference, parenthetical expansion, attribution by sentence rather than by paragraph for contested claims.