Johns Hopkins University

Arthur F Hogrefe

Jeffery C Lesho

Harry A Eaton

Wade E Radford

A multi-channel circuit for telemetering signals representing physiological values from a point in a human body to a receiver (24) outside of the body. The two signals (S.sub.1, S.sub.2) other than the temperature signal (27') are used to provide two frequency modulated signals (14, 16) summed by an amplifier (18) with the summed FM signal then being applied to amplitude modulate (21) a carrier (8) whose frequency varies as a function of temperature. The resulting FM/AM signal (22) is telemetered inductively outside of the body to an external receiver (24). Appropriate demodulation, filter, and shaping circuits within the external circuit detect the FM signals (14, 16) and thus produce three independent frequencies two of which are the original physiological variables and the third a function of local temperature. Real time plot of the two physiological variables can be obtained using FM discriminators while the temperature dependent frequency is best monitored by a counter.

AM/FM multi-channel implantable/ingestible biomedical monitoring

A 'pulse to zero' modulation scheme is taught to transmit binary information by modulating a bit mark onto a carrier at the start of each '0' in the bit stream. The 'pulse to zero' decoder produces an output that switches to '0' at the occurrence of the detected bit mark and resets to '1' if a second bit mark has not occurred within a preset time lapse from the previously detected bit mark.

Pulse to zero digital (PZ) modulation

The present invention is a universal interface allowing a main implant to supply power and receive data from remotely implanted sensor modules through a minimum number of interconnecting lines. The main module can supply a single DC voltage, two sequentially applied DC voltages or an AC voltage to the sensor module. A capacitor means in the sensor module supplies power while the sensor module is transmitting data.

Minimum interface biomedical monitoring system

A temperature responsive transmitter is disclosed. The transmitter utilizes a unique circuit design that allows encapsulation in an ingestible size capsule. The inventive circuit design uses a one transistor inverting amplifier with a tank circuit forming the link between the transistor's collector and the battery. The tank circuit is tuned to provide a lagging capacitive load which causes the inverting amplifier to oscillate. The tank circuit contains a coil inductor that emits a near field magnetic communications field containing temperature information. The ingestible size temperature pill can be configured in a rechargeable embodiment. In this embodiment the pill uses the inductive coil in the tank circuit as the magnetic pickup to charge a rechargeable nickel cadmium battery.

Ingestible size continuously transmitting temperature monitoring pill

A two-way coherent inductive communications link between an external transceiver and an internal transceiver located in a biologically implanted programmable medical device. Digitally formatted command data and programming data is transmitted to the implanted medical device by frequency shift keying the inductive communications link. Internal transceiver is powered by the inductive field between internal and external transceivers. Digitally formatted data is transmitted to external transceiver by internal transceiver amplitude modulating inductive field. Immediate verification of the establishment of a reliable communications link is provided by determining existence of frequency lock and bit phase lock between internal and external transceivers.

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Laurel, MD, United States of America

Arthur F Hogrefe