© 2018 by Extreme Sonar LLC


Wideband, Low Noise Preamp-Digitizer Module

The Preamp-Digitizer Module is the heart of an acoustic receiver. The preamp must have a low noise floor and a high clipping level. For a wideband sensor working in the frequency range from 10 kHz to 625 kHz, the Preamp-Digitizer will be the dominant noise source on a quiet platform. Many sonar systems use preamps with RTI noise levels as high as 11 nV per root Hz. Extreme Sonar's RTI noise levels are below 0.7 nV per root Hz, over 20 dB quieter. The preamp output is low pass filtered and fed into a full differential 24-bit A/D converter which digitizes at a 1.25MHz rate, allowing detection of 600kHz DVL navigation systems commonly employed on UUVs.

FPGA-SoC Based Processing

Minimizing Size, Weight and Power (SWaP) is critical for many underwater sensor applications, along with minimizing cost. Extreme Sonar uses state of the art COTS FPGA-SoC boards such as the DE10 Nano from Terasic for rapid prototyping. These boards support the latest FPGA and SoC processors and are small, low power, and can interface to multiple Preamp-Digitizer and/or Power Amplifier Modules while also providing local storage and standard interfaces including Gb Ethernet, USB and RS 232/422/485.

Class-E Bipolar Power Amplifiers

Most sonar power amplifiers are designed in a voltage source configuration which is optimized for driving inductive loads, including motors, moving coil based speakers, and piezo-ceramic transducers between their resonance and anti-resonance frequencies.

For driving piezo-ceramic transducers over a wide band, the load is capacitive at most frequencies, and a current source configuration provides a much better match. In addition to providing higher transducer drive levels, this configuration also increases efficiency and reduces size by dispensing with the requirement for a high voltage power supply. Instead, the high voltage is only created across the transducer's C0 (bulk) capacitance, reducing the size and complexity of the power amplifier, while increasing reliability and safety.

Wideband Countermeasueres

Submerged platforms can sometimes escape detection from threatening sonars and acoustic homing weapons by deployment of loud acoustic noisemakers which blind the enemy's acoustic sensors. Because sonar projectors are normally only efficient over a narrow frequency band, a large number of transducers and associated power amplifiers and waveform generators are generally required to cover the relevant frequency band.

Extreme Sonar has developed a novel technique for using a Pulser type power amplifier to exploit high-order projector modalities, allowing efficient transduction over a wide frequency band using low cost flexural disc projectors.

Broadband Ultrasonic Antifouling System

Biofouling is a huge problem for ships and submarines, both at sea and at the pier. Extreme Sonar has developed a novel technique for exploiting broadband ultrasonic waveforms at high power levels to protect ships from biofouling without resorting to expensive chemicals and ablative paints. Unlike other ultrasonic antifouling approaches, Extreme Sonar's Ultrasonic Antifouling System projects the ultrasonic energy directly into the water rather than vibrating the ship's hull. This approach requires external projectors, but is much more energy efficient because it avoids large losses in the hull, and provides more uniform coverage, including coverage of surfaces acoustically isolated from the hull such as rudders and props.