A moving military test vehicle is equipped with a radar system. From a fixed location, a user wants to record radar signals emitted by the vehicle during a motion sequence that lasts about one minute. This application note describes how Vitrek’s Gage RazorPlus CSE 16502 digitizer meets the requirements for this task.

The radar system emits narrowband signals within the X band (8 to 12 GHz). These signals are down-converted to a lower frequency range of 0 to 200 MHz using a down-converter. The down-converter generates two output signals – I and Q – which must be acquired simultaneously at a sampling rate of 500 MegaSamples per second (MS/s) throughout the one-minute motion sequence.

The Gage RazorPlus CSE 16502 digitizer is ideal for this application due to its following features:

• Analog Input Bandwidth: The 250 MHz analog input bandwidth accommodates the 0-200 MHz radar signals with minimal attenuation.
• Sampling Rate: With two input channels and a sampling rate of up to 500 MS/s, the RazorPlus meets the specified digitizer requirements.
• Resolution: The 16-bit resolution allows the user to probe signals with high dynamic range, capturing both large and small amplitude components.

• Inter-Channel Simultaneity: The RazorPlus digitizes the two signals (I and Q) with sufficient simultaneity. The skew jitter, which is the standard deviation of the skew over time, is only a few picoseconds. This corresponds to a fraction of a degree of signal phase angle at the highest signal frequency of 200 MHz, far exceeding the customer’s requirement.
• Continuous Acquisition Duration: The one-minute duration requires continuous acquisition at an aggregate data rate of 2 Gigabytes per second (GB/s). The 8 GB on-board acquisition memory of the RazorPlus can hold only a 4-second continuous acquisition. To overcome this limitation, the user operates in Streaming Mode, where waveform data are streamed through the RazorPlus’ onboard memory and transferred to a Streaming Target via the PCI Express (PCIe) bus. The RazorPlus, being a Gen 3 PCIe card, can sustain data transfer rates of over 5 GB/s, accommodating the 2 GB/s data stream.

During streaming operation, waveform data are streamed into a pair of dedicated toggling PC RAM memory buffers. One buffer is filled with new RazorPlus waveform data while the other buffer is emptied and its data transferred to the Streaming Target. This process ensures no data loss as long as the Target can empty one buffer before the other is refilled.

The user requires a modest total data volume of 120 GB, which fits within PC RAM. Vitrek provided a turn-key Gage Sig-Station PC with the RazorPlus hardware and all necessary software installed. The system was equipped with 256 MB of PC RAM, sufficient for the required 120 GB as a streaming Target. After acquisition, the 120 MB of data in PC RAM are stored to a conventional storage drive. The user reads the binary recorded waveform files within the MATLAB programming  environment to analyze the radar emission signals and extract key parameters.

Using Vitrek’s Gage RazorPlus digitizer, its streaming technology, and software installed within a Gage Sig-Station PC, the user developed a state-of-the-art recording system capable of recording and analyzing one-minute radar emission sessions. This solution ensures high precision, dynamic range, and seamless data acquisition for military test vehicle radar signals.