PROBLEM TO BE SOLVED: To generate a desired EPR image, without stting an additional gradient magnetic field coil, and to conduct high-amplitude magnetic field modulation higher than 2,000 micro tesla. SOLUTION: The output of an electromagnetic radiation source (13) is connected to one arm of a circulator or a hybrid T (14). The other arm of the circulator (14) is coupled to a resonator (15), and a third arm is connected to a microwave detector (17), the output of the microwave detector (17) is connected to one input of a phase detector (18), and one output of a high- amplitude modulator (16) is connected to the second input of the phase detector (18). The second output of the modulator (16) is connected to a modulation coil (22). The output of the phase detector (18) is connected to an analog/digital converter (19), and the output of the analog/digital converter (19) is connected to a computer (20). The resonator (15) is arranged at the center of the magnetic field, between the north pole and south pole of a magnet (21).
