A multifunction digital receiver suitable for real-time frequency detection and compensation in fast magnetic resonance imaging.

We describe the development and implementation of a multifunction digital receiver suitable for magnetic resonance imaging with capability of real-time frequency detection and compensation. The digital receiver consists primarily of firmware modules that combine the functionalities of signal acquisition, frequency detection and compensation, and data correction and image reconstruction. The receiver was developed based on a single multiple-input multiple-output radio-frequency electronic board equipped with a reconfigurable Field Programmable Gate Array (FPGA) device. A simple and practical algorithm was developed and implemented on the FPGA to accelerate the data processing for frequency determination. The simplified frequency detection and the higher system integration enable the receiver to reduce dramatically the time for frequency detection and compensation. With this receiver, we are able to detect the frequency of short-duration signals in the bandwidth of 10 MHz centered at 400 MHz within 75 ns after the signal acquisition. We describe the designs of the key FPGA modules and how these modules integrate into a multifunction receiver. We also present testing data that validate the simplified algorithm for frequency determination, demonstrate frequency detection and compensation, and demonstrate how real-time data correction is performed during image acquisition and reconstruction.