Method for RFID Communication Using Inductive Orthogonal Coupling For Wireless Medical Implanted Sensors and Other Short-Range Communication Applications
The description provides a signal detection system employing a wireless, passive detection device that utilizes waveform shifting for reporting signals to a reader device. The system is useful for a variety of applications including as an implanted medical device for monitoring patient conditions.
1 . A passive transmitter tag device suitable for implantation into a subject, said device comprising:
(a) a non-linear impedance element or time-varying element for introducing harmonics or frequency-shifted signal components into a back-emf produced by a sinusoidal carrier signal;
(b) an energy harnessing element;
(c) sensor/transducer for monitoring a patient condition, wherein said sensor is operably connected to said non-linear impedance element or time-varying element.
2 . The device of claim 1 , wherein said sensor/transducer is a pressure monitor.
3 . The device of claim 1 , wherein said sensor/transducer is a pH monitor.
4 . The device of claim 1 , wherein said sensor/transducer is a temperature monitor.
5 . The device of claim 1 , wherein said sensor/transducer is a blood glucose monitor.
6 . The device of claim 1 , wherein the energy harvesting element is a rectifier and capacitor.
7 . The device of claim 1 , wherein the non-linear impedance element is a bipolar transistor, a field-effect transistor or a voltage controlled oscillator.
8 . The device of claim 1 , wherein the time-varying element is a switch.
9 . The device of claim 1 , wherein the time-varying element is a mixer.
10 . The device of claim 9 , wherein the mixer is operably connected to receive (i) an input from a voltage controlled oscillator, and (ii) an input driven by induced voltage from the carrier signal.
11 . A reader device comprising:
(a) a signal source;
(b) a wave signal generator;
(c) a wave signal detector; and
(d) a signal processing unit.
12 . The device of claim 11 , further comprising a filtering circuit.
13 . The device of claim 12 , wherein said said filtering circuit is a high pass filter, a notch filter or a resonant LC tank.
14 . The device of claim 11 , further comprising an analog to digital converter.
15 . The device of claim 11 , wherein the signal processing unit employs a finite impulse response-matched filter.
16 . The device of claim 11 , wherein the signal processing unit employs a frequency domain method.
17 . The device of claim 16 , wherein the frequency domain method is a short-time Fourier Transform, or a windowed fast Fourier Transform.
18 . The device of claim 16 , wherein the frequency domain method is a spectrogram.
19 . The device of claim 11 , wherein the signal processing unit employs a look-up table.
20 . A system for transmitting information from a sensor comprising (a) the transmitter tag device of claim 1 and (b) the reader device of claim 11 .
21 . A method for transmitting information from the transmitter tag to the reader in the system of claim 20 , the method comprising transmitting a carrier signal from the reader device; wherein the carrier signal:
(a) is received by the transmitter tag and energizes the tag;
(b) is altered by the tag to introduce out of band electromotive force (emf) orthogonal to the carrier signal;
(c) is then modified by the non-linear impedance element connected to the sensor that measures a condition in an environment in which the transmitter tag is located;
(d) is returned to the reader where the carrier signal is filtered from the out of band emf; and
(e) is analyzed by the signal processing device.