Caruso SF7

Broadband Multi-Function Sounder/Profiler

Next Generation Underwater Detection & Surveillance

Marport's CARUSO SF7 is the defence industry's first broadband, multi-function sounder/profiler designed for both surface warships and submarines. The radical design is based on Marport's award-winning Software Defined Sonar technology that's revolutionizing underwater acoustics.

Software Defined Sonar is a disruptive hardware and software platform that enables multi-function sonar applications for underwater sensing, positioning and communications. Unlike traditional fixed hardware designs, its software-centric FPGAs are dynamically programmed to reconfigure functions “on the fly”. The system is delivered with the following active functions:

• DEPTH SOUNDER
• DOPPLER CURRENT PROFILER
• OBSTACLE AVOIDANCE
• SPEED VELOCITY LOG
• SUB-BOTTOM PROFILER
• SEABED CLASSIFICATION

System Diagram

Advanced Signal Processing Techniques

The CARUSO SF7 transceiver can be dynamically tuned across a frequency spectrum from 1 kHz to 1 MHz. The 80 channel transceiver utilizes advanced modulation and digital signal processing techniques to provide significantly improved range resolution and superior target discrimination when compared to conventional fixed-frequency sounders. The software defined architecture enables signal processing to be performed in the transceiver’s FPGAs which can be reprogrammed “on-the-fly” for desired function, frequency, bandwidth and pulse length.

In addition to standard CW modulation, the CARUSO SF7 can utilize FM CHIRP transmit pulses with correlation processing of the return signal. Instead of using a burst of a single carrier frequency, the frequency within the FM CHIRP modulated signal is swept over a broad range throughout the duration of transmission pulse. This creates a unique signature pulse - the sounder knows what was transmitted and when. Using pattern-matching algorithms, it looks for its own unique signature being echoed back from targets. The response from the pattern-matching techniques in the sounder results in longer transmissions and operating ranges without a loss in range resolution. CHIRP modulation also achieves superior signal to noise gain over conventional sounders. This enhances target detection resolution and is especially useful when trying to detect targets close to the bottom.

A robust, bottom tracking algorithm maintains bottom lock and delivers accurate depth results in difficult seabed topographies. The system also incorporates a seabed classification system using well-proven techniques to rapidly characterize the seabed. Classification is accomplished using quantitative analysis of backscatter data in support of seafloor characterization and small object identification.

Superior Detection Zone Coverage

The CARUSO SF7 provides superior detection when compared to conventional products. This is due to the 80 elements used in the phased array transducer versus only a single element in competitive products. In addition, each sonar beam within CARUSO SF7 can be individually beam-formed and steered ±30° from boresight. This is ideal for obstacle avoidance and provides superior seabed coverage. As an example at a reference depth of 500 metres, the CARUSO SF7 sonar beams cover a seabed area of 250,000 m². Conventional units that transmit a single 7° beam cover a seabed area of less than 3,000 m².

Complete Beam Stabilization

The sparse array transducer used within the CARUSO SF7 incorporates an integrated motion sensor to reduce the loss of targets due to vessel motion. All beams are maintained at required tilt by compensating for ship’s pitch (± 20°), roll (± 20°) and heave (± 100m). The beam stabilizer significantly improves target presentation by compensating for echogram distortion caused by vessel motion. This provides an enhanced presentation of the echogram images even in rough seas, and improves measurement accuracy.

Doppler Current Profiler

The doppler current profiler measures water current velocities over a wide range of depths and can be easily interfaced to the vessel’s DGPS and INS systems. The multiple beam sparse array design of the transducer provides a redundant data source in the case of a blocked or damaged beam. This also improves data quality and accuracy. Advanced digital signal processing is used to deliver very low-noise data, resulting in unparalleled fine track resolution and accurate velocity profiles. The profiler continuously measures and displays full water column profile velocities to depths of up to 1,000m. Other displayed parameters include: current direction/speed, measured depth, vessel speed, and more.

Sub Bottom Profiler

The unit integrates a sub bottom profiler that transmits a 30 kHz to 38 kHz parametric pulse. This signal is capable of penetrating the seabed and highlighting seismic structural differences and layers that are hidden from conventional sounders. The system can also operate with various signal waveforms for optimum performance. FM CHIRP pulses are used for deep water, high penetration work and CW pulses are used for narrow band, frequency sensitive work. The transmitted beam is electronically stabilized to ensure that the ensonified area is accurately positioned. Sub bottom penetration performance depends on sediment characteristics, water depth, transmitted signature etc. Typical penetration of up to 30 metres can be achieved in water depths of 1000 metres. This feature is ideal to detect geohazards located close to the seafloor surface.

Control Display Unit / Remote Display Unit

Both display units are rugged, high performance MIL-SPEC colour panel PCs. The primary CDU has a 17” touch screen display while the smaller RDU has an 8” touch screen display. The units use Marport's CommandView software to process and display real time sounder data. The software uses extensive pixel shading technology which allows CommandView to produce superb graphics.

Sonar data is tessellated in real-time, allowing the operator to view data in a variety of modes – including the standard true depth display or a unique 3D “waterfall” display. The waterfall display shows a 3D visualization of the sonar data as it happens, allowing the operator to more easily identify difficult targets from background noise. The waterfall sonar display makes use of a vertex shader to tessellate the raw sonar data into stunning 3D animations. The waterfall display also supports a 3D A-Scope that displays historical echograms with amplitudes proportional to intensity. Different screens can be configured for different operational and technical service requirements. Alpha-transparency techniques allow gauges to be overlaid on top of other gauges while still being able to view the data beneath, allowing better use of the available display space.

The software also functions as a sensor multiplexer, data logger and server. In addition to sounder data, it can multiplex data from a variety of shipboard sensors such as DGPS, sound velocity profilers, etc. onto a TCP/IP network connection. All data is time logged and positioned referenced for future playback and analysis. Serial interfaces (RS232/RS422) and Ethernet topologies are supported for data input/output.