A coupling loop or antenna is provided that can be used with a system that determines the resonant frequency of a sensor by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor. In one embodiment multiple energizing loops energize an implanted sensor and a sensor coupling loop connected to an input impedance that is at least two times greater than the inductance of the sensor coupling loop receives the sensor signal.
1. A coupling loop assembly used for wireless communication with an implanted sensor, comprising:
a sensor coupling loop having an inductance and connected to an input having an input impedance, wherein the input impedance is at least two times greater than an impedance of the sensor coupling loop and the sensor coupling loop is un-tuned; and
a plurality of energizing loops arranged in parallel, for energizing the implanted sensor, each energizing loop having a different resonant frequency,
wherein the sensor coupling loop is parallel to the energizing loops.
2. The loop assembly of claim 1 , wherein the resonant frequency for a first energizing loop is approximately 31 MHz and the resonant frequency for a second energizing loop is approximately 36.3 MHz.
3. The loop assembly of claim 1 , wherein there are two energizing loops and the resonant frequencies of the energizing loops are spaced geometrically.
4. The loop assembly of claim 1 , wherein there are more than two energizing loops and the resonant frequencies of the energizing loops are spaced logarithmically.
5. The loop assembly of claim 1 , wherein the input impedance is selected so that
Zin
Zin
+
jω
L
1
approaches 1, where Zin represents the input impedance, L 1 represents the inductance of the sensor coupling loop, and ω represents a frequency.
6. The loop assembly of claim 5 , wherein the frequency is within a frequency range of 30 MHz to 37.5 MHz.
7. A loop assembly used for wireless communication with an implanted sensor, comprising:
a sensor coupling loop; and
a plurality of energizing loops, for energizing the implanted sensor, each energizing loop having a different resonant frequency, wherein the resonant frequency of one of the energizing loops is determined by a first series capacitance and the resonant frequency of a second energizing loop is determined by a second series capacitance,
wherein the sensor coupling loop is electrically isolated from the energizing loops.
8. The loop assembly of claim 7 , wherein the sensor coupling loop and the energizing loops are parallel to each other.
9. The loop assembly of claim 7 , wherein there are two energizing loops and the resonant frequencies of the energizing loops are spaced geometrically.
10. The loop assembly of claim 7 , wherein there are more than two energizing loops and the resonant frequencies of the energizing loops are spaced logarithmically.
11. The loop assembly of claim 7 , further comprising:
a second sensor coupling loop, wherein the sensor coupling loop and the second sensor coupling loop have different resonant frequencies.
12. A method of wireless communication using a loop assembly, comprising:
providing an energizing signal to an implanted sensor using a plurality of tuned loops, wherein each tuned loop has a distinct resonant frequency; and
receiving a coupled signal using an un-tuned loop connected to an input impedance that is as least two times greater than an impedance of the un-tuned loop, wherein the coupled signal is generated in response to coupling the energizing signal to a signal generating circuit,
wherein the un-tuned loop is parallel to the tuned loops.
13. The method of claim 12 , wherein the resonant frequencies of the tuned loops are selected based on a mean frequency of a desired bandwidth.
14. The method of claim 12 , wherein the coupled signal is sampled less than 50 nanoseconds after the end of the energizing signal.
15. The method of claim 12 , wherein each tuned loop uses a distinct series capacitance to provide the distinct resonant frequency.