Gemini naturally expands the Microtelecom’s product line of sampling receivers towards higher frequencies.
The Gemini receiver features two RF inputs, each of them independently processed by a low-noise and high dynamic range RF front-end and sampled by a high speed, 14 bit, two channels A/D converter operating at 200 MSPS.
Each of the two RF front-ends of Gemini are equipped with a six bands pre-selection filters bank ranging from 28 to 170 MHz, a high IP3 LNA and a 0-30 dB, 1 dB steps variable attenuator.
Wideband Inputs for Direct Access to the A/D Converter
Gemini features two unconditioned wideband inputs (1-500 MHz, 3 dB bandwidth) which give a direct access to the A/D converter inputs for multiple channel operations with external RF signal conditioning. For the maximum flexibility the wideband inputs are equipped with independent variable attenuators.
Meeting the Need of Higher Speed Digital Signal Processing
The RF signals simultaneously sampled by the Gemini A/D converter are numerically processed at 200 MSPS/channel by a high speed multichannel digital down-converter implemented in a FPGA of Xilinx’s most recent Spartan6 family. The digital down-converter outputs are decimated down to 1 MSPS/channel or less and streamed to the PC processing plaftorm through a high-speed (480 Mbit/s) USB2.0 port.
Ultra Low Jitter Clock for the Highest Dynamic Range up to VHFs
As the frequency of the signals to be sampled increases, the quality of the A/D converter sampling clock needs to be higher and higher.
Gemini A/D converter is driven by a sampling clock derived from the industry best crystal oscillator, a ultra low noise 400 MHz voltage controlled oscillator locked to an internal 10 MHz, 1 ppm TCXO.
Optionally, when more than two inputs need to be simultaneously processed by more units, the receiver sampling clock can be locked to a 10 MHz external reference clock and the samples streams synchronized to an external trigger signal.
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