Edgetech Model 3100P Sub-bottom Sonar System, Руководство по оборудованию

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SECTION 1: OVERVIEW 1-2
3100-P PORTABLE SUB-BOTTOM 0004802_REV_F
1.1.2 High Repeatability
The FM pulses are generated by a digital-to-analog (D/A) converter with a wide dynamic range and a
transmitter with linear components. This allows the energy, amplitude, and phase characteristics of the
acoustic pulses to be precisely controlled. This precision produces high repeatability and signal definition
required for sediment classification.
The frequency range of operation is determined by the acoustic characteristics of the transmitter
transducers and receiving hydrophone arrays mounted on the tow vehicle. Each tow vehicle can transmit
acoustic pulses with different center frequencies and bandwidths.
The selection of this frequency is made by the operator while profiling to achieve the best imagery, and
the tow vehicle is selected based on the sub-bottom conditions at the survey site, along with the type of
sub-bottom features that need to be imaged. EdgeTech technical support can provide assistance in
selecting the best tow vehicle for your application.
1.1.3 High Signal-to-Noise Ratio
Full Spectrum chirp technology does not use a conventional matched filter (the correlation filter that is
widely used to compress FM signals) to process wide band signals. Rather it uses proprietary amplitude
and phase weighting functions for the transmitted pulse and a pulse compression filter that maximizes
the SNR of the acoustic images over a wide band of operating frequencies. These functions provide a
significant SNR improvement in the acoustic image over other pulse and chirp sonars with band limited
components that are limited in dynamic range.
1.1.4 High Resolution
Signals received at the surface from the hydrophone arrays in the tow vehicle pass through a software-
controlled, programmable, gain amplifier before being digitized with a 16-bit analog-to-digital (A/D)
converter at a sampling rate of 20, 25, 40, or 50 kHz The FM pulse is then compressed using a digital
compression filter. This correlation process is implemented in real time with forward and inverse Fast
Fourier Transforms.
The compressed pulse has a time duration approximately equal to the inverse of the bandwidth of the FM
pulse which results in a high temporal resolution. This high resolution enables the measurement of fine
layering in the sediment, an important factor in sediment classification, as it provides a more realistic
picture of the true geologic variability of the sea floor and an accurate determination of the depositional
processes.
1.1.5 Additional Processing Gain
In addition to the resolution improvement, correlation processing achieves a signal processing gain over
the background noise. This gain is approximately ten times the log of the time-bandwidth product.