A Study Of Direct Rf Sampling Receiver In Magnetic Resonance Imaging System

Magnetic Resonance Imaging is an important part of modern medical imaging. With the development of MRI technology, there're new requirements for MR spectrometer. The commercial MR spectrometer has high performance and powerful functionality. However, the price is an important factor that limits the universalization of the MRI system. Therefore, the research of low cost MRI system means a lot to the healthcare business in our country.MRI receiver plays an important role in MRI system. The performance of receiver may be decisive in the imaging quality. Different from receiver application in other fields, MRI system requires that MRI receiver has very high dynamic range, low noise and good linearity. To achieve the specification of MRI receiver, many devices with high performance but also high price are applied, which pushes up the cost of MRI receiver.Direct radio frequency sampling receiver is applied in software define radio. There're benefits with application of direct radio frequency sampling receiver in MRI system. First, the part of analog circuit can be simplified which helps cost down. Second, with the development of DSP and FPGA technologies, the signal processing such as filtering and frequency mixing can be done in digital field. The digital way of signal processing is more flexible and its performance is much better than the analog way. In conclusion, the application of direct RF sampling receiver in MRI system will simplify the structure of system and reduce the cost.The direct RF sampling receiver is researched in this article. The influence of clock stability to the performance of receiver is analyzed. An improved method of phase noise measurement is introduced. Several ADCs are analyzed and tested. The issue of dynamic range in MRI system is discussed. A method that combines automatic gain control technology with pilot signal in MRI receiver is introduced to improving the dynamic range of MRI receiver.