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Wire Guided Torpedo-ModemWire Guided Torpedo-Modem

The Defence Electronics Applications Laboratory (DEAL), Dehradun, has designed and developed a Wire Guided Torpedo-Modem (WGT-Modem) for wire guided torpedo which provides a full-duplex telemetry data link between firing control system (FCS) and wire guided torpedo, through a 2-core guidance wire. The firing control system onboard the mother ship/submarine provides command and guidance to the torpedo through this data link. Modem design employs state-of-the-art signal processing techniques to circumvent the problem posed by the transmission media. The fully ruggedized WGT-modem allows data rate of 206 baud with maximum line length of 26 km.

The WGT-Modem provides:

Feher non-linear filtering for CPFSK signal spectrum shaping to meet the desired out of the band energy rejection. This is implemented using programmable logic devices, microprocessor, EPROM look-up table etc;

Self-adaptive technique for 2-4 W conversion to meet requisite isolation and self-balancing of the hybrid during unreeling of guidance wire when a torpedo is fired; and

Digital symbol timing recovery technique for data clock synchronisation, realized using PLDs and microcontroller.

DEAL has also developed a set of dedicated test equipment, comprising FCS-end compatible modem, data generator/error detector and guidance wire simulator to facilitate the bench testing/performance evaluation of WGT-Modem.

The WGT-Modem was integrated with torpedo signal processing unit and the data link was established successfully with FCS onboard the submarine, during the torpedo system technical trials. Indigenously fabricated multiple units of WGT-Modem and associated test equipment have been delivered to the Naval Science & Technological Laboratory (NSTL), Visakhapatnam, for torpedo sea-trials.