Slot antenna for in-body ISM-band communication
Examples of implantable devices having a hermetically-sealed, metal container are disclosed. In one example, the implantable device has a Bluetooth Low Energy (“BLE”) beacon inside the hermetically-sealed, metal container. The hermetically-sealed, metal container may have a micro-strip type transmission line on an internal side of the container such that the container acts as the ground plane of the micro-strip transmission line. A slot at a specific location and having specific characteristics (such as shape, length, and/or width) may be cut into the ground plane of the micro-strip to act as a radiator. Thus, the size of implantable devices can be reduced by using a slot antenna in the hermetically-sealed, metal container. Such a device implanted in a suitable location and at a suitable depth in a user can communicate with an external computing device, such as a smartphone held in the user's hand.
1. An implantable industrial, scientific, and medical (ISM)-band device comprising:
a hermetically-sealed container constructed of an electrically conductive material, the hermetically-sealed container defining a slot antenna;
an ISM-band transmitter disposed within the hermetically-sealed container;
a microwave dielectric substrate disposed on an interior surface of the hermetically-sealed container corresponding to the slot antenna; and
a micro-strip transmission line disposed on the microwave dielectric substrate and crossing the slot antenna.
2. The implantable ISM-band device of claim 1 , wherein the ISM-band transmitter is a Bluetooth Low Energy (BLE) transmitter.
3. The implantable ISM-band device of claim 2 , wherein the slot is configured to transmit a radio frequency (RF) signal from the BLE transmitter to an external computing device at a frequency between 2400 MHz and 2483.5 MHz.
4. The implantable ISM-band device of claim 1 , wherein the ISM-band transmitter is positioned near an end of the micro-strip transmission line.
5. The implantable ISM-band device of claim 1 , wherein the hermetically-sealed container is cylindrical and comprises a diameter between 10 millimeters and 40 millimeters.
6. The implantable ISM-band device of claim 5 , wherein the hermetically-sealed container comprises a height between 3 millimeters and 5 millimeters.
7. The implantable ISM-band device of claim 1 , wherein the micro-strip transmission line comprises copper deposited on the microwave dielectric substrate.
8. The implantable ISM-band device of claim 1 , wherein the microwave dielectric substrate comprises aluminum oxide.
9. The implantable ISM-band device of claim 1 , wherein the microwave dielectric substrate comprises a thickness between 0.11 millimeters and 0.15 millimeters.
10. The implantable ISM-band device of claim 9 , wherein the micro-strip transmission line comprises a thickness between 0.2 millimeters and 0.3 millimeters.
11. The implantable ISM-band device of claim 1 , wherein the slot comprises a width between 100 microns and 600 microns.
12. The implantable ISM-band device of claim 1 , wherein the slot comprises a width between 120 microns and 140 microns.
13. The implantable ISM-band device of claim 1 , wherein the slot comprises a length between 16 millimeters and 28 millimeters.
14. The implantable ISM-band device of claim 1 , wherein the slot is substantially perpendicular to the micro-strip transmission line.
15. The implantable ISM-band device of claim 14 , wherein the slot crosses the micro-strip transmission line at a middle of the micro-strip transmission line.
16. The implantable ISM-band device of claim 14 , wherein the slot crosses the micro-strip transmission line towards an end of the micro-strip transmission line.
17. The implantable ISM-band device of claim 1 , wherein the electrically conductive material comprises titanium.
18. The implantable ISM-band device of claim 1 , wherein the hermetically-sealed container provides a ground plane for the micro-strip transmission line, and wherein the slot provides a far-field radiator.
19. The implantable ISM-band device of claim 1 , wherein the implantable device does not comprise an inverted F antenna, does not comprise a monopole antenna, and does not comprise an electrically small dipole antenna.
20. A system comprising:
an implantable industrial, scientific, and medical (ISM)-band device comprising:
a hermetically-sealed container constructed of an electrically conductive material, the hermetically-sealed container defining a slot antenna;
an ISM-band transmitter disposed within the hermetically-sealed container;
a microwave dielectric substrate disposed on an interior surface of the hermetically-sealed container corresponding to the slot antenna;
a micro-strip transmission line disposed on the microwave dielectric substrate and crossing the slot antenna, wherein the hermetically-sealed container acts as a ground plane for the micro-strip transmission line;
and
a sensor.
21. The system of claim 20 , wherein the ISM-band transmitter is a Bluetooth Low Energy (BLE) transmitter and the RF signal comprises a frequency between 2400 MHz and 2483.5 MHz.
22. The system of claim 20 , wherein the hermetically-sealed container is cylindrical and comprises a diameter between 10 millimeters and 40 millimeters.
23. The system of claim 22 , wherein the hermetically-sealed container comprises a height between 3 millimeters and 5 millimeters.
24. The system of claim 20 , wherein the micro-strip transmission line comprises copper deposited on the microwave dielectric substrate.
25. The system of claim 20 , wherein the microwave dielectric substrate comprises aluminum oxide.
26. The system of claim 20 , wherein the microwave dielectric substrate comprises a thickness between 0.11 millimeters and 0.15 millimeters.
27. The system of claim 26 , wherein the micro-strip transmission line comprises a thickness between 0.2 millimeters and 0.3 millimeters.
28. The system of claim 20 , wherein the slot comprises a width between 100 microns and 600 microns.
29. The system of claim 20 , wherein the slot comprises a width between 120 microns and 140 microns.
30. The system of claim 20 , wherein the slot comprises a length between 16 millimeters and 28 millimeters.
31. The system of claim 20 , wherein the slot is substantially perpendicular to the micro-strip transmission line.
32. The system of claim 31 , wherein the slot crosses the micro-strip transmission line at a middle of the micro-strip transmission line.
33. The system of claim 31 , wherein the slot crosses the micro-strip transmission line towards an end of the micro-strip transmission line.
34. The system of claim 20 , wherein the electrically conductive material comprises titanium.
35. The system of claim 20 , wherein the sensor comprises at least one of a temperature sensor, a pressure sensor, an oxygen sensor, or a pH sensor.