Abstract: A reader of an RFID system has excitation circuitry for generating a higher voltage excitation signal, receiving circuitry for reading a lower voltage transponder signal and an antenna coupled with the excitation circuitry for transmitting the excitation signal and coupled with the receiving circuitry for receiving the transponder signal. The receiving circuitry includes a low voltage signal stripping circuit coupled with the antenna for isolating the transponder signal from the excitation signal preliminary to the receiving circuitry reading the transponder signal. The bulk of the components of the low voltage signal stripping circuit are low voltage components, which can be included in an application specific integrated circuit.
Abstract: A reader for an RFID system has an exciter circuit for generating an excitation signal and a feedback circuit coupled to the exciter circuit for automatically tuning the exciter circuit. The exciter circuit has at least one retunable component providing the exciter circuit with adjustable component values and a plurality of signal generating states. The exciter circuit is initially tuned to a first signal generating state, but is retunable to additional signal generating states by adjusting the component value of the retunable component. The feedback circuit includes a circuit evaluator coupled to the exciter circuit for determining a value of an operational parameter of the exciter circuit. A decision-making circuit is coupled to the circuit evaluator for formulating a decision in response to the value of the operational parameter.
Abstract: A reader unit for use in a radio frequency identification (RFID) system delays the initiation of an interrogation operation when potentially interfering radio frequency (RF) energy is detected within an operational frequency range of the system. The reader unit waits a quasi-random period of time after the detection and then senses the spectral environment again to determine whether the energy is still present. If the energy is still present, the reader unit waits another quasi-random period and the process repeats. If there is no energy present or the energy is below a threshold value, the reader unit immediately initiates the interrogation operation. By delaying the initiation of the interrogation operation until the operative frequency range is free of potential interferers, the likelihood of harmful interference effects is significantly reduced.
Abstract: A method is provided for operating an RF transponder system to detect the presence of an RFID device in the proximal space of an RF reader unit having an excitation signal generator circuit and an RFID device detection circuit. The excitation signal generator circuit unit initially operates in a reduced power state, generating ring signals in response to a reduced electrical current and transmitting the ring signals into the proximal space. The RFID device detection circuit evaluates the ring signals to determine variations in an RFID device detection parameter. When the variations pass a variation threshold level due to the presence of the RFID device, the ring signals are terminated and the excitation signal generator circuit switches to an increased power state, wherein the excitation signal generator circuit generates an RF excitation signal which is transmitted to the RFID device.
Abstract: A tilt sensor utilizes the “Wiegand Effect” to sense the occurrence of a tilting of the sensor from one inclined position to a horizontal position to another inclined position. The tilt sensor includes within a plastic or other non-magnetic body a non-magnetic elongated tube, a magnet that is contained and substantially freely slidable within the elongated tube, and a Wiegand wire that extends along and that is adjacent to the elongated tube. The tilt sensor also generally includes a coil wound on the Wiegand wire and a pole piece that extends along and that is adjacent to the elongated tube through which the Wiegand wire extends, and the pole piece is made of a material through which a magnetic flux path can be created. In operation, as the tilt sensor is moved from one inclined position to another inclined position, the magnet within the elongated tube slides from one end of the tube to the other.
Abstract: A Wiegand sensor is provided as a power source for an external circuit, wherein an alternating magnetic field changes the magnetic state of a Wiegand wire within the Wiegand sensor which, in turn, produces a substantial output pulse that is provided as a power source for the external circuit. The external circuit may be a transmitter that is powered by the output of the Wiegand sensor and upon being powered transmits an information signal to an appropriate receiver. The number of occurrences that the magnetic field alternates corresponds to and is ascertained from the number of information signals that are transmitted. The alternating magnetic field may be generated by magnets coupled to a rotating valve of a gas or water meter such that the occurrence of each transmission of the information signal represents the flow of a predetermined amount of gas or water through the meter.
September 24, 1998
Date of Patent:
February 20, 2001
David J. Dlugos, Don Small, David A. Siefer
Abstract: A Wiegand token essentially is comprised of a disk-like token body that has two substantially flat surfaces, one of the flat surface including a groove, for example, a circular groove, therein, and a Wiegand wire is embedded within the groove of the token body. The Wiegand token may have multiple concentric grooves with a Wiegand wire embedded within each groove. In general, the Wiegand token is for use in a device having a read head that responds to a magnetic field change generated from a switch in state of the Wiegand wire as the token passes by the read head. When the token includes plural Wiegand wires therein, the read head responds separately to each magnetic field change generated from a switch in state of each Wiegand wire as the respective Wiegand wire passes by the read head. Moreover, the read head separately responds to magnetic field changes that are generated from a switch in state of two different segments of the Wiegand wire as the respective segment passes by the read head.
Abstract: A read head for a Wiegand wire has two C-shaped ferro-magnetic yokes in lateral alignment with one another, two magnets sandwiched between respective first and second legs-of the yokes, and a pickup coil wound on one of the legs of the read head. One magnet has a first polarity adjacent to the first leg of the first yoke, the other magnet has the first polarity adjacent to the second leg of the second yoke, and the reluctances of the two yokes are equal. When used in combination with a processor that processes the output pulses, a Wiegand token having one or more Wiegand wires therein may be detected by counting the number of output pulses of the read head and ascertaining the duration of time between occurrences of those pulses. Wiegand tokens having different values may have different numbers of Wiegand wires therein and/or different spacings between the Wiegand wires within the Wiegand token and, thus, the read head in combination with a processor can identify Wiegand tokens of different values.
Abstract: A wireless modem employs a radio frequency (RF) transponder system components to remotely access the memory of an electrical or electro-mechanical device by providing an exciter/reader/writer (ERW) circuit free of electrical contact with the electrical or electro-mechanical device and a transponder including a transmit/receive antenna, a reading circuit, a programming circuit, and a transponder memory. The transponder memory is directly connected to the device memory. The ERW circuit initially generates an RF excitation signal powering the transponder. In response to the RF excitation signal, the transponder generates a RF response signal using the reading circuit that is transmitted back to the EWR circuit. The RF response signal includes data from the device memory. The RF response signal is received by the ERW circuit, which in turn generates an RF write signal that is transmitted to the transponder.
Abstract: An encryption method and stored value system comprising a host computer, a reader/writer that communicates with the host computer, and an RF transponder that communicates with the reader/writer. The transponder comprises a transponder chip having a memory with a plurality of memory sections, which encryption method protects data stored in the memory. The method provides a secure way to increase and decrease the value stored the transponder and to selectively write and data to and from the transponder.
Abstract: An RF identification system for generating data indicative of an item that is tagged, and one bit of variable data representative of an external stimulus. An ID code reader is provided and an RF identification tag is coupled to the item that is to be monitored and the ID code reader queries the tag. The tag comprises two RF transponder chips that store a data relating to the item, and an excitation coil coupled thereto. A switch is coupled to the chips and excitation coil, and a capacitor is coupled across the switch. A sensor is coupled to the switch for generating one bit of variable data representative of an external stimulus, such as the pressure in a tire. The ID code reader comprises an exciter and RF excitation coil, and a receiver and an RF receiver coil. The receiver includes phase detection circuitry for detecting a state of the switch by detecting the phase shift between signals received from each of the transponder chips. When the switch is shorted, the effect of the capacitor is nullified.