| Arbitrary Waveform Generator (AWG) is playing an important role in general purpose signal generator. It is widely used in physics, electronics and computer area. Nowadays the mainstream AWGs are still foreign commercial products. Although they have high frequency stability, wide frequency output range, abundant modulation function and friendly user interface, they are expensive and the main technology is in foreign company's hand.In this asset, a self made general purpose AWG is proposed. It is composed of a Universal Serial Bus (USB) interface, a Direct Digital Synthesis (DDS) and a Field Programmable Gate Array (FPGA). It is proved to be low cost while its performance remains competitive compared to commercial ones.In this paper, points listed below will be covered:First, the basic theory of Nuclear Magnetic Resonance (NMR) and the hardware structure of a NMR spectrometer are introduced.Second, the principle of waveform generating is introduced. Conventional waveform generating means and their advantages and disadvantages are also discussed.Third, the design procedure of the AWG is described in detail. The hardware and software designing are talked respectively.Last, the characteristics of the AWG are tested. And the Magnetic Resonance Imaging (MRI) experiment results are obtained by implementing it into a home-built 0.3T MRI system, replacing the original radio frequency transmitting unit. Problems within the designing and experimenting are discussed. |
