2.1. Coil design and fabrication

Each elongated transceive SCC loop coil (Figure ​(Figure1A),1A), with minor axis 60 mm and major axis 160 mm, was constructed from thin 50 Ohm coaxial cable (Huber+Suhner K 02252 D‐06, diameter 3.0 mm). Impedance matching used a balanced capacitive pi‐matching network: two 27‐pF high‐voltage‐rated (7200 V) capacitors (Dalicap, Dalian, China) were connected in series and one high‐voltage‐rated 33‐pF capacitor in parallel. The transceive array was constructed of five identical SCC loop coils spaced 5 mm apart (Figure ​(Figure1).1). The elements were attached to a flexible foam former, with a thickness of 10 mm. The cable length connecting the coil and the interface was 1000 mm long. The array elements were tuned on a volunteer whose neck circumference was 370 mm because this was approximately the median dimension of the measured neck circumferences of five volunteers (two females and three males). Measured S‐parameters on a workbench are shown in Figure ​Figure11.

Coil schematics, fabricated five‐channel array, measurement setup on volunteer, and measured S‐parameters on a workbench