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Table 2: Comparison of five different antennas designed for medical implants. The size of our antenna is governed by the dimensions of the ground plane.

Antenna type True antenna size Characteristics Spiral [1] 402 MHz Return loss 25 dB Frequency detuning ~15% −21 dBW at 1 m (7 mm deep in 2/3 muscle, 1.6 W/kg) Serpentine [1] 475 MHz Return loss 10 dB Frequency detuning ~20% −25 dBW at 1 m (7 mm deep in 2/3 muscle, 1.6 W/kg) Higher resonant frequency than a spiral with the same physical length Spiral [2] 402 MHz Return loss 18 dB Return loss 5 dB (measurement) Frequency detuning ~5% (measurement) Front to back ratio ~5 dB Radiation efficiency ~0.16% PIFA [2] 402 MHz Return loss 16 dB Return loss 6 dB (measurement) Frequency detuning ~10% (measurement) Front to back ratio ~5 dB Radiation efficiency ~0.25% Higher efficiency than the spiral New design 31.5 GHz Return loss 30 dB Frequency detuning ~1%  dBW/m2 at 1 m (8 mm deep in skin and fat) Front to back ratio ~15 dB