Case Studies
Modernizing a Passive Sonar which has a Beam-Former with Digital Output
The customer's requirement is to capture 10 signals, lasting 0.6 milliseconds each. 120 such signals arrive sequentially from a multiplexer within a beam-former. The clock rate is 2 MHz. The beam-former creates 120 beams and the raw digital data (underwater acoustic signal) from each beam is present at the output port of beam-former with a clock rate of 2Mhz. At a certain time, we get the digital raw data of one beam. We plan to get 120x10 12 bit data records. That is, we plan to get 10, 120 beam data records. After acquisition, the data are processed in order to determine the BTR (bearing time record), the DEMON, the Lofar spectrum etc. The digital signal is a +/-5 volt TTL signal. The software driver should support windows messaging system.(The card should send buffer full message when the buffer is filled).
GAGE'S SOLUTION
For one channel the client will need one card. The required amount of on-board memory is as follows:
Number of samples from one beam-former:
120x0.0006 sec. X 2 Ms/s = 144,000 samples of 12 bits.
Total samples from 10 captures: 10 x 144,000 = 1.44 Ms 12 bits.
Since the digital data resolution is 12 bits, we must use the 16 bit (2 bytes) input width. Therefore the number of on-board bytes required is 1.44Ms x 2 = 2.88 Mbytes.
Gage recommended the CompuScope 3200 with 8 MB of on-board memory. This will be sufficient for 27 beam-former runs. Gage also recommended the CMOS Buffer Board, which will provide the customer's digital signals with sufficient strength to drive the 50 Ohm load presented by each input of the CS3200.
PRODUCT RECOMMENDED
CS3200-8M with buffer board
This application note is provided "as is" without any warranties of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. Gage Applied Technologies further does not warrant the accuracy and completeness of the material contained herein. Gage Applied Technologies may make changes to this material, or to the products described in it, at any time without notice.
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