Scientists from ITMO University and Lebedev Physical Institute of the Russian Academy of Sciences have proposed a new microwave antenna that creates a uniform magnetic field in large volume. It is capable of uniform, coherent addressing of the electronic spins of an ensemble of nanodiamond structure defects. This can be used to create super-sensitive magnetic field detectors for magnetoencephalography in the study and diagnosis of epilepsy and other diseases. The results are published in JETP Letters.