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. The coupling loop includes multiple loops. Preferably two tuned loops are used for transmitting the energizing signal to the sensor and an un-tuned loop is used for receiving the sensor signal from the sensor. Orientation features on the housing for the coupling loop and the sensor are provided to assist in positioning the coupling loop relative to the sensor to maximize the coupling between the sensor signal and the coupling loop.
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 the inductance 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 and the energizing loops surround the sensor coupling loop.
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. A loop assembly used for wireless communication with an implanted sensor, comprising:
a plurality of sensor coupling loops, each coupling loop having a different resonant frequency; 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 loops are electrically isolated from the energizing loops.
4. The loop assembly of claim 3 , wherein the sensor coupling loops and the energizing loops are parallel to each other and the energizing loops surround the coupling loops.
5. The loop assembly of claim 3 , wherein there are two energizing loops and the resonant frequencies of the energizing loops are spaced geometrically.
6. The loop assembly of claim 3 , wherein there are more than two energizing loops and the resonant frequencies of the energizing loops are spaced logarithmically.
7. 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 at 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, is at least 100 dB less than the energizing signal, and has a frequency similar to a frequency of the energizing signal,
wherein the un-tuned loop is parallel to the tuned loops and the tuned loops surround the un-tuned loop.
8. The method of claim 7 , wherein the resonant frequencies of the tuned loops are selected based on a mean frequency of a desired bandwidth.
9. The method of claim 7 , wherein the coupled signal is sampled less than 50 nanoseconds after the end of the energizing signal.
10. The method of claim 7 , wherein each tuned loop uses a distinct series capacitance to provide the distinct resonant frequency.
11. A method of wireless communication using a loop assembly, comprising:
providing an energizing signal to an implanted passive sensor using a plurality of tuned loops, wherein each tuned loop has a distinct resonant frequency; and
receiving a coupled signal from the passive sensor 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 a resonant frequency of the passive sensor varies and the communication frequency between the tuned loops and the passive sensor and the communication frequency between the passive sensor and the un-tuned loop track the resonant frequency of the passive sensor.
12. The method of claim 11 , wherein each tuned loop uses a distinct series capacitance to provide the distinct resonant frequency.
13. The method of claim 11 , wherein there are two tuned loops and the resonant frequencies of the tuned loops are spaced geometrically.
14. The method of claim 11 , wherein there are more than two tuned loops and the resonant frequencies of the tuned loops are spaced logarithmically.