Our team has the experience and competence in using Silicon Lab chipset for one of the Projects by name ‘Directional Sonobuoy(DSB)’. Sonobuoys are part of anti-submarine warfare systems being used by the Navy across the world. Sonobuoys are Electro-mechanical devices dropped by aircraft into the sea for detection of enemy submarines in sea. The hydrophones attached to the Sonobuoy pick up acoustic signals from submarines and transmit the same to aircraft which are in combat mode. The signals received from Sonobuoys are analyzed and the presence of enemy submarines, if any, will be detected and attacked.

The electronics consists of two units, namely Underwater Electronics Unit and Surface Electronics Unit , separated by a distance of 300m (1000ft) and connected through a 300m 2-wire cable.

The underwater electronics unit is a water tight enclosure capable of operating at a depth of 300m consisting of the following functional components / modules. Thesensor front end module receives low level acoustic signals from hydrophones . In a similar manner, the omni sensor front end module receives acoustic signals from another hydrophone . The sensors are selected based on the control received through command function select (CFS) via UHF receiver (which uses a Silicon Lab chip) or according to the manual setting done prior to deployment through electronic function select (EFS) on the surface electronics unit. These signals are pre-amplified, filtered and digitized. This data is interleaved with the heading sensor and transmitted to the surface electronics unit through the 2 wire cable telemetry.

      The surface electronics unit is a water tight enclosure capable of operating at depths of 15m to 20m. The surface electronics unit will have a manual switch interface (EFS)for users to configure or update the settings manually, in addition to the remote command section through UHF command function select. The communication between the underwater electronics unit and the surface electronics unit is via2-wire telemetry through a 300 metre cable with 2 cores (parallel wires). The surface electronics unit will receive the data from the underwater electronics unit through the telemetry module, generate the composite signal and modulate to the FM channel in the VHF band through the VHF transmitter module. 

          The channel selection will be as per the setting from electronics function select (EFS) or command through command function select (CFS) received by means of the UHF receiver module. The position information obtained from the GNSS receiver along with Heading Sensor information is also modulated along with the composite signal on the same FM carrier to transmit the position information of the Sonobuoy. The antenna unit consisting of the VHF antenna (for data telemetry to remote station), UHF antenna (for receiving command from remote station) and GNSS antenna will be co-located within the floatation bag.

UHF Receiver based on Silicon Lab Chipset

         For a simple and cost effective design with minimum PCB area, the fully integrated transceiver EFR32FG solution of Silicon Labs has been adopted. The receiver portion is used in the Sonobuoy. The UHF transmitter onboard the aircraft platform is implemented by the transmit segment with appropriate transmit power amplifiers. The EFR32FG device is a fully integrated single-chip radio transceiver designed for high performance at very low-power and low-voltage operation in cost-effective wireless systems. The EFR32FG device provides extensive hardware support for packet handling, data buffering, burst transmissions, clear channel assessment, link quality indication, and Wake-On-Radio. The main operating parameters of the EFR32FG device can be controlled through an SPI interface. In a typical system like our’s, the EFR32FG device needs only a few external passive components.

The EFR based VHF receiver design and development has been successfully completed and tested successfully for the target application.