Import substitution of High Power Radar Transmitter Systems And Circuits

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Spaceborne RADAR satellites for Earth observation use Synthetic Aperture RADAR (SAR) technology for high resolution all weather imaging. Being an active RADAR system in Space, high power transmitters are a crucial and limiting technology. SAR being a coveted and critically important technology in National Resource Management and National Security, complex and critical technologies required for high resolution SAR payload development often suffer from export restrictions. Over the years SAC, Ahmedabad has indigenously developed several critical technologies for high power transmission in SAR payloads enabling India to be more and more self-reliant in developing SAR payloads.

X-Band 50 W MMIC PA assembled in test package

Ferrite based high power RF front-end duplexing systems are very critical for SAR payloads with a single transmit and receive antenna. This critical technology is niche and sparsely mastered and bears high cost. SAC has indigenously designed, developed and qualified high power front-end systems for SAR payloads. X-Band 2 kW ferrite based Front End Switching system is flown in several satellites. Ku-band Front End system is currently being developed as import substiturion for Scatterometer payloads of India.

X-band front-end Stack mounted in EOS-1 payload deck

High Power Front-End systems for SAR payloads

Example of state-of-the-art made-in-India RF high power Front-End System: The X-Band 2 kW Circulator-Switch Assembly (CSA) on-board the RISAT-2B, RISAT-2BR1 and EOS-01

  • 2 kW peak power & 440 W average power handling capability
  • Tx path loss:<0.2 dB; Tx-Rx isolation: 60 dB; Rx path loss:<0.6 dB; switching speed: <2 microns
  • 24 units flown on-board

X-Band 2 kw front-end switch assembly

High power SAR Transmitter Systems

Starting from the RISAT-1 and continuing through the Chandrayaan-2 SAR, RISAT-2B, RISAT-2BR1, EOS-1, EOS-4 and NISAR, SAC has indigenously designed and developed solid-state RF transmitter systems and TR modules for SAR payloads. High power SSPAs in X-Band as import substitution for TWTAs for strategic payloads are developed. These cover GaN based transmitter system. SAC is also developing TWTA based transmitter systems in partnership with Indian Industries as a high efficiency alternative to solid-state technology. For NISAR, SAC has designed 160 W S-Band TR module with in-built LTCC based RF receiver chain, High Power GaN based Transmit module, high power front-end duplexer module, calibration network, digital controller in one modular miniature module.

X-band front-end Stack mounted in EOS-1 payload deck

X-band front-end Stack mounted in EOS-1 payload deck

X-band front-end Stack mounted in EOS-1 payload deck

X-band front-end Stack mounted in EOS-1 payload deck