Abstract:

Generator that can generate the MRS（Magnetic Resonance Sounding) signal is design to develop JLMRS groundwater detection system. It is convenient to indoor testing of JLMRS groundwater detection system using simulate MRS（Magnetic Resonance Sounding） signal. Due to the low amplitude and highresolution frequency of MRS signal, the hardware of generator is based on the principle of DDS（Direct Digital Synthesizer）. The phase accumulator is programmed by CPLD(Complex Programble Logic Device), the MRS signal data is calculated by Matlab, and then stored in the nonvolatile RAM(Random Access Memory), which can save data after power down, so it is not necessary to repeat downloading. This generator can adjust the amplitude, frequency, delay time constant, and phase of the MRS signal, and it can be added in various noises of different SNR（Singnal to Noise Ratio）. It has been authorized the national utility model patent (200820072674.2), and was already used in the development of the JLMRS groundwater detection system. It is testified that the amplitude error is lower than 0.02 V, the frequency resolution is 1 Hz, the output is stabilization, can be used repeatedly, and meets the demands of the JLMRS water investigation instrument.

Key words: magnetic resonance sounding, groundwater, signal generator, direct digital synthesizer（DDS）