Ramtron International Corporation

Racom Systems, Inc.

Gregory M Smith

Gary T Carroll

J Donald Pauley

Michael W Yeager

Donald J Verhaeghe

Jeffery E Downs

A single integrated circuit for an RF/ID transponder includes a nonvolatile memory portion, which is ideally a ferroelectric memory, digital logic, digital interface circuitry, and differential analog driver circuitry for driving an antenna that is contained within the RF/ID transponder, but external to the integrated circuit. In series with each leg of the differential analog driver circuitry, and also fabricated on the single integrated circuit, are two groups of serially connected resistors. All circuit nodes associated with the resistors are connected to a signal level control logic block that is in communication with the on-chip digital logic block. The signal level control logic block is used to selectively control the output resistance of the driver circuitry such that a proper balance between incoming and outgoing signal levels is achieved. The output resistance can be programmed to several different levels, the granularity of the levels being determined by the number of serially connected resistors used. An optimum code corresponding to the optimum output resistance is stored in a small portion of the on-chip nonvolatile memory. The code can be externally programmed and updated as required by new applications. The code can also be externally programmed to permanently disable the RF/ID transponder by setting the output resistance to an extremely high level or by open circuiting the output resistance altogether.

Programmable output devices for controlling signal levels in an RF/ID

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.

Method and apparatus for detecting an FSK encoded carrier signal

A filter circuit includes an input node for receiving an unfiltered input signal, an output node for providing a filtered output signal, and an intermediate node. An integrator has an input coupled to the input node and an output coupled to the intermediate node. A Schmitt trigger has an input coupled to the intermediate node and an output coupled to the output node. A reset circuit has a first input coupled to the input node, a second input coupled to the output node, and an output coupled to the intermediate node. The signal on the intermediate node is generated by integrating the unfiltered logic input signal if the input signal and the output signal are at opposite logic states. A filtered output logic signal is generated by conditioning the intermediate signal with the Schmitt trigger. The reset circuit resets the intermediate signal if the input signal and the output signal are each at a zero logic state or if the input signal and the output signal are each at a one logic state.

Noise and glitch suppressing filter with feedback

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. The power-up and power-down thresholds describe a proper voltage range of operation for the ferroelectric memory in the transponder. The power enable indication is provided to the ferroelectric memory so that the memory is only operated when the power supply voltage is within the proper range so that data is valid during read and write operations.

Power supply and power enable circuit for an RF/ID transponder

A system and method for initiating communication between a controller and a selected one or other subset of multiple transponders in a common RF field in which each transponder has a unique, (or commonly unique) preprogrammed ID number. The controller transmits a series of commands/questions to the transponders and they either respond, or do not respond, to the controller based on their ID number, with the non-responding transponders entering a reset state. The transponders respond to the controller in such a way that, if multiple transponders respond, the controller can recognize that at least one transponder has responded and, for individual responses, the controller is not required to determine how many transponders have responded. Through use of the communications system and method disclosed, a sequence of controller commands and transponder responses single out a selected individual transponder or group of transponders based upon its particular ID number.

Growing community of inventors

Colorado Springs, CO, United States of America

Gregory M Smith