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 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.