A 31.5 GHz Patch Antenna Design for Medical Implants

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%
		−57.49 dBW/m^2 at 1 m
		(8 mm deep in skin and fat)
		Front to back ratio ~15 dB