Case Studies
Satellite Down Line Converter
A customer needs capture incoming satellite communication signals at a ground-based receiver. After analog demodulation and amplification, the signal is digitized by two 12 bit ADC chips clocked at a rate of 47.3 MHz. One ADC is used to scale a high-voltage input signal that has a mean value of 25.85 V. The second ADC chip is used to get better accuracy on the same signal, using a proprietary signal-scaling technique. The first ADC scales the full input voltage so that the second ADC only sees a small 50 mV signal around the mean 25.85 V. In this way, the combined system can achieve up to 22 bits of effective resolution. All ADC digital outputs are Transistor-Transistor-Logic (TTL).
The customer requires a high-speed digital input module with at least 24 input bits to capture data from both 12 bit ADCs. In order to achieve the combined 22 effective bits of resolution, it is paramount that all 24 bits be simultaneously sampled with the 47.3 MHz external clock. The signal must be captured in repetitive bursts that last 10 milliseconds each.
GAGE'S SOLUTION
The Gage CompuScope 3200-2M provides the ideal solution to the customer's requirement. With its 32 input bits and up to 100 MHz sampling capability, the CS3200 meets the main acquisition requirements. Furthermore, the CS3200 accepts TTL inputs and has 2 MB of on-board acquisition memory, which is more than sufficient for the 10 ms capture-time requirement. The external clock feature is standard on the CS3200 and the clock phase can be inverted, if necessary, so that its rising edge occurs when the digital data is stable.
Initially, the customer will capture data with the CS3200 using GageBit - Gage's standalone Windows-based digital input/output software, which provides a logic analyzer-like environment. GageBit allows the user to access all the functionality of the CS3200 without writing a single line of code. GageBit also provides digital data masking capability as well as several logical operators (NOT, OR, XOR, AND...), which can be used to separate data from the two ADCs. Using GageBit, the customer can immediately begin capturing and storing data on their prototype receiver system.
Down the line, the customer will develop their own integrated Windows-based application to control the final commercial receiver system. As a starting point for this application, they will use a sample program from Gage's powerful C/C++ Software Development Kit. Using the off-the-shelf CS3200 and C/C++ SDK, the customer will have a powerful system completely customized to the satellite receiver requirement.
PRODUCT RECOMMENDED
CS3200-2M (CMOS or TTL)
GageBit Digital Input/Output Software (included with CS3200)
CompuScope SDK for C/C++ for Windows
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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