Orthogonal-coil RF probe for implantable passive sensors.
A versatile orthogonal-coil radio frequency (RF) probe suitable for detecting the resonant frequency of miniature implantable passive sensors has been designed and tested. The probe sensitivity has been tested using printed-circuit spiral inductors of various sizes (3-15 mm) in series with discrete surface-mount capacitors designed to resonate over a range of frequencies (50-200 MHz). Close agreement between theoretical calculations and experimental results has been obtained. An equation is derived for transmit/receive (T/R) isolation that agrees with experimental measurements over the frequency range 1-500 MHz. The probe includes an additional coil to compensate for the effect of eddy currents in the human body on the probe. T/R isolation of at least 90 dB over the frequency range 1-100 MHz can be achieved when the probe is placed in close proximity to the human body.
SAF, Inc., the Naval Research Laboratory, Washington, DC 20375, USA. talman@obcm.nrl.navy.mil
James R
JR
Talman
Aaron J
AJ
Fleischman
Shuvo
S
Roy
D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D055590:Electromagnetic Phenomena / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D019736:Prostheses and Implants; D011474:Prosthesis Design; D011846:Radio Waves; D013686:Telemetry / Q000295:instrumentation* / Q000379:methods; D014159:Transducers