India and Japan have signed an agreement for the co-development of a naval radio antenna based on Japan’s UNICORN system.

The announcement was made during the visit of Japanese Prime Minister Sanae Takaichi to India, marking a significant milestone in bilateral defence cooperation.

Prime Minister Narendra Modi revealed the development during a joint press briefing. He emphasised that this was the first-ever co-development project between the two nations in defence technology. He stated that the Naval Radio Antenna project would open a new chapter in their partnership and that both countries would jointly develop technologies to strengthen regional peace, maritime security, and the rules-based order.

This agreement represents one of the most tangible outcomes of India–Japan defence cooperation, which until now had been limited to joint exercises and exploratory activities.

For years, India had considered procuring the Shinmaywa US-2 seaplane, but the plan was eventually shelved. There had also been collaborative research between DRDO and ATLA on Visual SLAM-based GNSS Augmentation Technology for unmanned ground vehicles.

Discussions on UNICORN between India and Japan date back to 2022. In 2024, the foreign and defence ministers of both nations appreciated the progress made on the transfer of Unified Complex Radio Antenna technologies and the early signing of related arrangements. This laid the groundwork for the current agreement.

UNICORN is already in service with the Mogami-class frigates of the Japan Maritime Self-Defence Force. The Indian Navy is expected to equip its next-generation warships with a derivative of the system. In 2025, Mazagon Dock Shipbuilders Limited had indicated preliminary discussions regarding a common destroyer design between India and Japan, suggesting deeper collaboration in naval architecture.

The UNICORN antenna integrates multiple systems into a single mast to enhance stealth. From top to bottom, it incorporates an ES-R antenna, ES-C antenna, WiFi band antenna, LINK-16 antenna, UHF antenna, IFF antenna, U/VHF antenna, and TACAN antenna.

The system was jointly developed by NEC, Sampa Kogyo, and Yokohama Rubber. NEC acted as the prime contractor, providing hardware integration and TACAN systems. Sampa Kogyo contributed antenna technologies and maintenance expertise, while Yokohama Rubber developed the frequency selective Radome. Saab had also pitched its SLIM integrated mast solution, highlighting the competitive landscape in integrated mast technologies.

At DefExpo 2022, the Indian Navy’s Directorate of Electrical Engineering showcased a project for the two-phase development of an Indigenous Integrated Mast with Bharat Electronics Limited as the production partner. The current status of this project remains unclear, but it is likely to be progressed or merged with the localised adaptation of UNICORN.

The Indigenous Integrated Mast Phase-I was designed to have a height of 11 metres without a Radome. It involved integrating R-ESM, COMINT, V/UHF communication, and Data Link antennas on a single mast.

The final design envisaged placing the L Band Data Link antenna at the top, followed by COMINT and ELINT antennas, with the bottom-most antenna comprising a Rhode and Schwarz V/UHF communication system.

Phase-II envisaged a shorter mast between 8 and 11 metres, incorporating a frequency selective Radome and integrating R-ESM, COMINT, L Band Data Link, two sets of V/UHF communication antennas, and an optional WiFi antenna.

The co-development of UNICORN between India and Japan therefore represents not only a technological advancement but also a strategic deepening of defence ties. It builds upon earlier collaborative efforts and positions both nations to jointly shape the future of naval stealth and integrated communication systems in the Indo-Pacific.

Agencies