Palestrante
Descrição
Nuclear Magnetic Resonance experiments need very sensitive equipment to detect very weak signals among very intense ones. To achieve this, the transceiver must have a dynamic range greater than 80 dB. Also, the module providing the clock signals to the system must have ~10 ppb of stability and phase noise better than -80 dBc/Hz at 1 kHz offset. The first part of this work focused on the clock generating module for an 85 MHz (2.0 T magnet) spectrometer. This module has two output signals: a 50 MHz clock for the FPGA and A/D converters and a 90 MHz reference signal for the up/down converter mixers. The intermediate frequency in this system is 5 MHz and the transceiver operates on lower sideband modulation (L.S.B./U.S.B.). To avoid spurious oscillations in both outputs, the reference signals have the same source. The output of a 10 MHz OCXO is differentiated to generate all the harmonics of 10 MHz up to ~5 GHz. (1) Two high-Q filters select the desired frequencies before the amplifying stage: the 5th harmonic for 50 MHz and the 9th one for 90 Mhz. Both outputs are pure sine waves. To generate the FPGA clock, one output passes through a high speed clock driver to generate a differential clock signal. The other signal goes to a 1:16 power splitter to be distributed to all the spectrometer channels.
Referências
1 WYATT, K. Harmonic comb generators are useful tools. 2015. Disponível em:https://interferencetechnology.com/harmonic-comb-generators-are-useful-tools/.Acesso em: 28.08.2017.
| Subárea | Ressonância Magnética e Caos |
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