Abstract: A Colpitts-type oscillator circuit suitable for use with electronic identification systems is disclosed. The oscillator circuit utilizes a pair of transistors coupled together with a feedback loop that includes a parallel LC circuit such that the output amplitude can be as high as a factor of 20 times the supply voltage or more while maintaining a high Q, low distortion output. The oscillator circuit is a modified Colpitts oscillator that includes a NPN transistor and a PNP transistor coupled together and a Colpitts type feedback loop containing a parallel LC circuit. The capacitance of the parallel LC circuit consists of at least two capacitors in series forming a capacitive divider which provides a low impedance feedback via the base of the NPN transistor into the emitter of the PNP transistor. The collector of the PNP transistor taps into the inductor of the parallel LC circuit such that the inductor is driven to resonance.

Abstract: An enhanced peak detector circuit for the amplitude demodulation of an incoming amplitude modulated signal is provided. In its simplest form, the enhanced peak detector circuit includes a forward biased NPN transistor, a peak detecting segment coupled to the base-emitter junction of the transistor; and a peak holding capacitor leading from the collector of the transistor and connected in parallel to the peak detecting segment. The peak detecting segment includes a parallel connected peak detecting capacitor and a resistor. When the base-emitter junction of the transistor is conducting, both the peak detecting capacitor and the peak holding capacitor are charging. Conversely, when the base-emitter junction of the transistor is back biased, the peak detecting capacitor discharges through the resistor and the collector remains open such that the peak holding capacitor remains charged.

Abstract: An FSK detector circuit and method which may be utilized for the demodulation of a digital data signal from a modulated sine wave carrier signal. A simple, low parts count FSK detector is disclosed which is readily implemented as an integrated circuit for the detection of a digital data signal in wireless applications without the use of an associated phase locked loop or other frequency detection circuitry.

Abstract: An integrated FSK detector circuit includes a first counter that receives a carrier signal and provides a multiple-bit output for reducing the frequency of the carrier signal into a plurality of weighted sub-multiples. An oscillator enable decoder circuit provides predetermined calibrate and measure pulses in response to the first counter output. A gated oscillator receives the calibrate and measure pulses and provides a burst of oscillator pulses during these time intervals. A second counter has an input coupled to the output of the gated oscillator and an up/down control terminal coupled to the output of the first counter. The output of the second counter also provides a multiple-bit output for reducing the frequency of the gated oscillator pulses. An FSK decoder logic circuit decodes the multiple-bit output of the second counter into a single bit FSK detect signal. The FSK detector circuit also includes a reset circuit coupled to the first counter for resetting between FSK detections.

Abstract: A passive transponder incorporating non-volatile ferroelectric memory is powered by inductive coupling to a proximately located controller. A communication system and method utilizes the controller to send data and commands to the transponder by an FSK modulated RF signal in order to cause the transponder to either read selected data from, or write selected data to, the non-volatile memory and transmit the same back to the controller utilizing PSK RF modulation. The communication system and method operates either full duplex or half duplex with the controller causing the transponder to simultaneously write data to its non-volatile memory as the memory is read out and transmitted to the controller thereof. Features of the invention include, signal transmission between the controller and transponder occur concurrently; the controller's FSK signal is modulated between 125 KHz and 116.3 KHz; the transponder's PSK signal is 62.

Abstract: A passive RF transponder incorporating a non-volatile memory element is powered by inductive coupling to a proximately located RF controller. A communication system and method is disclosed which utilizes the controller to send data and commands to the transponder by means of an FSK modulated RF signal in order to cause the transponder to either read selected data from, or write selected data to, the non-volatile memory and transmit the same back to the controller utilizing PSK modulation. The communication system and method may be operated in either full duplex or half duplex modes of operation with the controller causing the transponder to simultaneously write data to its non-volatile memory array as the contents are read out and transmitted to the controller by complementing selected bits thereof.

Abstract: A programmable identification apparatus, and associated method, includes a transceiver and a transponder. The transponder is powered by the energy of a transceiver transmit signal generated by the transceiver and includes a programmable memory element. A coded sequence which uniquely identifies the transponder is stored in the programmable memory element and, when the transponder is powered, the transponder generates a transponder signal which includes the coded sequence stored in the programmable memory element, once modulated by circuitry of the transponder. When the transceiver transmit signal generated by the transceiver circuitry is of certain signal characteristics, the coded sequence stored in the programmable element is erased, and a substitute coded sequence, which also forms a portion of the transceiver transmit signal, is stored in the programmable memory element.

Abstract: A power supply self-contained within a portable RF/ID transponder includes a full wave rectifier having an input for receiving an antenna signal and outputs for providing power supply and ground voltages, wherein the power supply voltage has a time varying voltage waveform corresponding to the electric field generated by a reader/controller. The power supply further includes a clamping circuit for regulating the power supply voltage and a ferroelectric filter/storage capacitor coupled between the power supply and ground outputs of the full wave rectifier. The power supply further includes a power enable circuit for constantly monitoring the supply voltage waveform and for providing a power enable indication after an initial portion of the supply voltage waveform rises above a predetermined power-up threshold level and for removing the power enable indication when a terminal portion of the supply voltage waveform falls below a predetermined power-down level.

Abstract: An oscillator circuit includes a multiple output transconductance amplifier having a positive voltage input, a negative voltage input, and three current outputs. A first current output is coupled to the positive input, a second current output is coupled to the negative input, and a third current output provides the full logic voltage oscillator output signal. A resistor network is coupled to the positive voltage input of the transconductance amplifier. The first current output is used to generate a square wave signal at the positive voltage input. A capacitor is coupled to the negative voltage input of the transconductance amplifier. The second current output is used to generate a triangle wave signal at the negative voltage input. Both the square wave and triangle wave have a mean DC level centered halfway between the power supply rails of the transconductance amplifier.

Abstract: Low cost, compact electronic identifier apparatus interrogates a passive (no external power) or active (external power) transponder. Such identifier apparatus and transponder(s) may be used, e.g., for: (1) access control, (2) animal feeding and animal health, (3) inventory control, (4) process control, and/or (5) theft/security applications. The identifier apparatus further powers the transponder if it is passive. A power carrier signal broadcast by the identifier apparatus clocks and/or synchronizes the transponder operation. In response to being interrogated, the transponder sends back identification (ID) data. The ID data is received and extracted by the identifier apparatus in the presence of the power carrier "noise", and is then demodulated and decoded to recover the ID data. The electronic identifier apparatus uses a low cost, high speed, single chip microcontroller configured to operate so as to eliminate the use of decoders, drivers and other external circuitry.

Abstract: A device and method for precise placement of a medical instrument for fluid delivery at, or withdrawal of fluid from, a predetermined location in a body is disclosed. A sensor, such as a proximity detector or electrically conductible circuitry, is implanted into the body adjacent to a predetermined location, which location preferably has an implanted reservoir thereat, for sensing the position of a medical instrument having an open end portion inserted into the reservoir to enable delivery of medicament into the reservoir or, in the alternative, to remove fluid from the reservoir. A signal indicative at least of a sensed desired positioning of the instrument is generated and used to assure that the instrument has been properly positioned, with additional circuitry also being provided to enable location of the implanted reservoir for positioning of the instrument prior to insertion into the body.