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Orthogonal-coil RF probe for implantable passive sensors
James R Talman1, Aaron J Fleischman, Shuvo Roy
1SAF, Inc., the Naval Research Laboratory, Washington, DC 20375, USA. talman@obcm.nrl.navy.mil
IEEE Transactions on Bio-Medical Engineering
|March 15, 2006
Summary
A novel radio frequency (RF) probe accurately detects resonant frequencies in miniature implantable sensors. This versatile probe achieves high transmit/receive isolation, even near the human body.
Area of Science:
- Biomedical Engineering
- Radio Frequency Engineering
Background:
- Miniature implantable passive sensors require precise resonant frequency detection.
- Existing radio frequency (RF) probes face challenges with sensitivity and isolation, especially in biological environments.
Purpose of the Study:
- To design and test a versatile orthogonal-coil RF probe for detecting resonant frequencies of miniature implantable passive sensors.
- To evaluate the probe's sensitivity, theoretical calculations, and transmit/receive (T/R) isolation.
Main Methods:
- Designed and tested an orthogonal-coil RF probe.
- Utilized printed-circuit spiral inductors (3-15 mm) and surface-mount capacitors (50-200 MHz) for sensitivity testing.
- Derived and experimentally validated an equation for T/R isolation (1-500 MHz).
- Incorporated an additional coil to mitigate eddy current effects from the human body.
Main Results:
- Achieved close agreement between theoretical calculations and experimental results for resonant frequency detection.
- Validated the derived T/R isolation equation against experimental measurements from 1-500 MHz.
- Demonstrated T/R isolation of at least 90 dB from 1-100 MHz in proximity to the human body.
Conclusions:
- The developed orthogonal-coil RF probe is a versatile tool for detecting resonant frequencies of miniature implantable passive sensors.
- The probe exhibits excellent sensitivity and high T/R isolation, even in the presence of the human body.
- The findings support the probe's utility in biomedical applications requiring non-invasive sensing.
