Interesting technology there, this VEPSS stuff.
Fortunately that article gives a comprehensive description of their setup, including part numbers.
The digital synthesizer is a signal generator AD9958 (Analog Device Inc. Norwood, MA, USA). It supplies a sinusoidal current, Icos(ωt), of approximately 10 mA rms in the frequency range of 1–200 MHz. The current is supplied at 200 pre-programmed equally spaced frequencies, under PC control. The transceiver consists of two concentric coils with radii of R1 = 3.2 cm and R2 = 11 cm, separated by a distance of 10 cm. Both coils were built from ten turns of magnet wire AWG22 rolled on an ergonomic plastic harness specifically designed for an adult human head (Figure 2). The coil inductances, calculated from Faraday’s law, are approximately 67.4 and 796.4 µH for the inductor and sensor coils, respectively. The estimated mutual inductance coefficient is approximately M = 72.8 µH. To avoid inductive pickup the leads of the coils are twisted. A commercial device, AD8302 (Analog Devices Inc. Norwood, MA, USA) was used for phase detection. The AD8302 is a fully integrated RF IC for measuring differences in phase between two signals with a resolution of 10 mV/degree. The signals from the inductor and sensor coils are connected through a 5X preamplifier SR445 (Standford Research System Inc. Sunnyvale, CA, USA) to the digital synthesizer and phase detector module...
It seems like their choice of DAC can just output 10ma directly. Or at least that's the peak indicated in the datasheet. It's not an especially high power application.
