Abstract: An RFID system and method for communicating between a host computer, one or more interrogators connected to the host computer, and a large body of transponders distributed within an area covered by the interrogators. Each transponder originally has a common identification code, and upon initialization by the host computer internally generates a unique identification code based upon an internally generated random number. The host, through the interrogators, reads each of the identification codes associated with each transponder by iteratively transmitting a read identification code command along with a controlled variable. Each transponder compares the received controlled variable to an internally generated random number, and selectively transmits its identification code based upon the outcome of this comparison. After the completion of each read identification code iteration, the host adjusts the controlled variable based upon the responses received in the previous iteration.

Abstract: An RFID system and method for communicating between a host computer, one or more interrogators connected to the host computer, and a large body of transponders distributed within an area covered by the interrogators. Each transponder originally has a common identification code, and upon initialization by the host computer internally generates a unique identification code based upon an internally generated random number. The host, through the interrogators, reads each of the identification codes associated with each transponder by iteratively transmitting a read identification code command along with a controlled variable. Each transponder compares the received controlled variable to an internally generated random number, and selectively transmits its identification code based upon the outcome of this comparison. After the completion of each read identification code iteration, the host adjusts the controlled variable based upon the responses received in the previous iteration.

Abstract: In a receiver, a system and method are disclosed for providing improved detection of data from a transmitted sequence of pulse width modulated (PWM) pulses. The disclosed system includes a pulse detector having an adjustable critical duty cycle for distinguishing between first and second pulses based upon their respective long and short duty cycles at which they are received. The disclosed system further includes an element which determines the duty cycle of the received pulses and an element which adjusts the critical duty cycle based on the duty cycle which is so determined. The duty cycle may be determined by determining the correspondence between information obtained from an initial pulse sequence and reference information at the receiver. In the disclosed method, the duty cycle of pulses in an initial sequence is first determined and then checked against a predetermined limit. If the duty cycle falls outside the limit, the critical duty cycle is adjusted prior to further pulses being detected.

Abstract: A frequency cancelling system is disclosed which improves reception of a communication signal which is transmitted at a communication frequency in the presence of an interference signal which occurs at the same communication frequency. The frequency cancelling system generates a reference signal at the communication frequency, and adjusts the reference signal to be opposite in phase and equal in amplitude to the interference signal. The reference signal and the communication signal are then combined to cancel the interference signal. In a preferred embodiment, the reference signal is generated from the same source as that from which the interference signal arises. Preferably, the interference signal is received during an interval in which the communication signal is not being transmitted, and the reference signal is adjusted to be opposite in phase and equal in amplitude to the interference signal during that interval.

Abstract: A transponder adapted to be used in a checkout or inventory control system is disclosed which transmits by modulating and re-radiating a transponder signal frequency derived from a carrier frequency received on a transmitting antenna. The transponder includes a dual mode antenna and circuitry which selectively operates the antenna to suppress undesired emission of the transponder signal frequency when the transponder is not transmitting. A terminating circuit is further disclosed which suppresses undesired emission of the transponder signal frequency by a demodulator portion of the transponder.

Abstract: An apparatus and method for measuring the real-time volumetric flow rate of grain in a field harvester, comprising: a transmitting acoustical transducer for transmitting acoustic signals at a selected frequency, the transmitting acoustical transducer being disposed in the harvester with respect to a flow path of an airborne stream of grain during operation of the harvester so as to transmit the acoustic signals through the airborne stream of grain, whereby the transmitted acoustic signals are attenuated or scattered when passing through the airborne stream of grain; a receiving acoustical transducer for receiving the attenuated or scattered acoustic signals after passing through the flow path of the airborne stream of grain; and a computer in communication with the transmitting acoustical transducer and the receiving acoustical transducer for measuring the real-time volumetric flow rate of the airborne stream of grain as a function of the attenuation or scattering of the transmitted acoustic signals and a flo

Abstract: A system and method for storage and communication of information between at least one first information containing terminal and a second terminal. The system and method includes generating a random number within the first terminal in response to receipt of a begin signal from the second terminal, and comparing the random number to a count incremented and maintained by a digital counter within the first terminal. When the random number is equal to the count, the first terminal transmits a request to transmit signal to the second terminal. If the second terminal responds with a first acknowledgment, the first terminal then sends an information containing signal to the second terminal. If the information containing signal is correctly received, the second terminal responds by transmitting a second acknowledgment which is received by the first terminal.