Marport has announced a new software defined chirp echosounder for commercial fisheries and fisheries research applications. The first deliveries are scheduled for June 2008.
CHIRP ES is a broadband echosounder that utilises advanced frequency modulation (CHIRP FM) and digital signal processing to provide significantly improved range resolution and superior target discrimination when compared to fixed-frequency echosounders. A 'chirp' is a signal in which the frequency increases ('up-chirp') or decreases ('down-chirp') with time.
The unit’s software defined architecture enables digital signal processing to be performed in software which can be programmed 'on-the-fly' to utilise any frequency, bandwidth, or pulse length. It uses a non-linear FM (CHIRP) transmit pulse with correlation processing of the return signal. Instead of using a burst of a single carrier frequency, the frequency within the burst 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' techniques, it looks for its own unique signature being echoed back from targets.
The response from the 'pattern-matching' algorithms in the echosounder results in longer transmissions and operating ranges without a loss in range resolution. CHIRP modulation also achieves superior signal to noise gain over traditional fishery echosounders. This enables enhanced target detection and discrimination and is especially useful when trying to detect fish close to the bottom. A robust, bottom tracking algorithm maintains bottom lock and delivers accurate depth over even the most difficult seabed topographies. The echosounder also incorporates a digital seabed classification system using well-proven techniques to rapidly characterise the seabed.
The unit’s transceiver can be dynamically tuned from 1kHz-625kHz, and can be configured to operate with up to four different transducers. In addition to operating as a broadband single beam echosounder, the transceiver can be upgraded in the future to function as a multi-function split beam echosounder and doppler current profiler.
