Abstract: A modulated retroreflection system for secure two-way communication and identification includes a transceiver at a first location and a transponder at a second location. The transponder receiving, modulating, and reflecting the signal back to the transceiver includes a retroreflector having a at least one reflective surface coated with an electro-responsive material. The electro-responsive material modulating the reflection coefficient of the reflective surface thereby modulating signals reflected by the surface. The transponder further includes a modulator electrically connected to the electro-responsive material for applying a modulated bias voltage thereby modulating the refractive index and consequently the electrical phase, and/or amplitude of the reflected signal.

Abstract: A status monitoring system for evaluating the condition of an electrode implanted in the body of a mammal. The system comprises a modulator for modulating interrogation signals on an electrode of an implanted device, and a monitor for analyzing modulated interrogation signals being reflected by the electrode. The monitor comprises a transmitter for transmitting interrogation signals, a receiver for receiving and processing the signals reflected by the electrode, and a microprocessor for controlling the transmitter and the receiver. The microprocessor producing electrode condition data from the signals processed by the receiver. The invention further comprises a communication system in communication with the monitoring device for transmitting the electrode condition data to a remote location. The interrogation signals are transmitted by the transmitter onto the electrode. The interrogation signals are modulated on the electrode by combining with a modulation signal generated by the modulator.

Abstract: A telemetry system includes a remote monitoring station, a repeater worn externally by a patient and a quasi-passive transponder attached to a device implanted in the patient. The remote monitoring station communicates to the repeater to initiate an interrogation routine between the repeater and the transponder to extract patient condition information from the implanted device. When the repeater receives the condition information, it relays it to the remote monitoring station. The transponder is specially designed to operate with an extremely low level of power, less than 1 nW/baud, and to be compatible for attachment to existing implanted devices. The transponder can operate at a very high data rate, including a rate of about 100 kbps.

Abstract: A high-temperature superconductor (HT.sub.c S) in a microstrip configurat which is electrically related to a superconducting coupler and which is controlled by a heater disposed over the superconducting microstrip line. This limiter configuration is used in a series configuration with other circuitry and utilizes the low loss characteristics of the HT.sub.c S material and the wide bandwidth characteristics of microstrip. The structure itself is a five layer microstrip geometry which includes a normal metal ground plane; a dielectric substrate disposed on the metal ground plane; a superconducting microstrip transmission disposed on the substrate; a dielectric film layer disposed on the superconducting microstrip; and a heating element disposed on the dielectric film layer and over the superconducting microstrip.