RF Receiver: Receive Coils and the Limits of Sensitivity

RF Receiver · Electromagnetic

How much signal-to-noise ratio is physically available before any amplifier is chosen, and what coil geometry comes closest to it.

Receive coil array of small loops on a helmet over the head inside the magnet bore — A receive array: small loops over the head, each read out on its own channel. Illustration.

Acrylic cylinder carrying copper receive loops, with preamplifier boards mounted above it — A receive loop array on an acrylic former, with a low-noise preamplifier board on each element (October 2026).

Rectangular copper receive loop on a white curved former with a small circuit board — A single receive loop on a curved, 3D-printed former, with its matching board (October 2026).

The question

For a given body, field strength and region of interest there is an upper bound on the signal-to-noise ratio that no receive coil can exceed, set by the electromagnetic problem alone. That bound, the ultimate intrinsic SNR, is the yardstick against which a real array should be measured. A coil that reaches 70 per cent of it is good; one that reaches 30 per cent has room left, and the gap tells you where to look.

What we work on

Ultimate intrinsic SNR at low field. Computing the bound for realistic body models rather than uniform spheres, with full-wave and quasi-static formulations compared against each other.
Array coils and coupling. Mutual coupling between array elements, scattering matrix formulations, and what coupling costs in sensitivity.

Technical notes

The MR Signal in Units of the Square Root of Power → How much signal power a receive coil can deliver, derived with the reciprocity principle.