Design And Implementation Of DDC Based On FPGA In Magnetic Resonance

With the rapid development of the technology of magnetic resonance imaging, phased array coil and parallel imaging technology have been widely applied. In order to improve the sensitivity of the magnetic resonance signal, despite of more and more MRI receiving channel, resonance receiver is required to provide targeted and flexible multi-channel digital down conversion processing method. At present, the digital magnetic resonance receiver uses commercial digital down conversion chip to complete digital quadrature detection of magnetic resonance. However, the number of channel in the commercial digital chips is limited with low SNR, which can’t meet the needs of modern magnetic resonance imaging development. Therefore, according to the characteristics of magnetic resonance signal detection, it is really important to do some research in the multi-channel magnetic resonance digital down conversion technology whose design is practical.FPGA is a programmable and flexible chip which is widely used in the design of digital circuit. According to the characteristics of the narrow signal bandwidth in MRI, it is necessary to design the best algorithm for frequency conversion, which is to obtain better pass band characteristics and SNR. With the increase of the number of MRI receive channel, whose frequency conversion algorithm will be completed on one piece of FPGA. Under such circumstances, the difficulty in volume and the design complexity of multi-channel receiver will be reduced. The low cost and the great flexibility give the system convenience on function extension and upgradation.With the principle of digital down conversion, we use the DSP Builder, VHDL code, IP library calls and design several blocks such as NCO, mixer and filter in FPGA, which is to realize variable frequency with parameter control system of single channel and four-channel digital magnetic resonance. The system which can meet the parameter requirements from MRI detection has the strong characteristics of reconfigurable, high integration and SNR, because the filter coefficients and extraction factor can be changed simultaneously and flexibly. On account of above advantages, the system gives a high-performance solution to the design of NMR digital receiver.