A Mobile NMR System with a Compact and Efficient Class-D RF Amplifier

A portable NMR system allows NMR technology to be used outdoors and in remote areas. A truly mobile system should be able to be carried by the user to any area and operated without much physical effort. The goal of a mobile NMR system is then to bring the system to the sample instead of bringing the sample to the system. A fully integrated mobile NMR system was developed and tested. The mobile system was made possible by the successful development of a compact and high efficiency 17MHz, 30 Watt Class-D RF amplifier. A prototype system was built using a SoC FPGA module and running a Linux OS to control the pulse generation and data processing and was integrated to work with a newly developed portable MOUSE sensor [1]. A 400 MSPS DDS device was used for RF pulse generation and to drive the Class-D RF amplifier. A duplexer was developed to enable sensor tuning and matching and a receiver amplifier was also included to provide 72 dB gain. Experiments showed successful T₂ measurements on polymer composites and rubber samples. The new mobile system was designed to be controlled remotely and the web based control program running on an iPad demonstrates the portability of the new system. The fully integrated system prototype fits in a case measuring 140x120x100 mm (LxWxH) and weighs 800 grams, figure 1.

Figure 1. The prototype mobile NMR system with new sensor [1].