A transponder (14) for communicating with an interrogator (12) has a high Q-factor resonant circuit (34) of frequency f.sub.1 for receiving RF powering signals. The transponder also has a tuning circuit (56,58) which when in electrical communication with the resonant circuit (34) is operable to form a lower Q-factor resonant circuit (60) of frequency f.sub.3 for receiving RF communications from the interrogator unit. The transponder also includes a demodulator (66) which is in electrical communication with said resonant circuit (34). Additionally, the transponder (14) also included a control circuit (40) which receives a demodulated data signal from the demodulator (66). The control circuit (40) is further connected to the tuning circuit (56,58) and is operable to connect the tuning circuit (56,58) to the high Q-factor resonant circuit (34) in order to form the lower Q-factor resonant circuit (60). Control circuit (40) also converts the RF powering signals to a DC current for storing energy. The energy is stored in an energy storage device such as a storage capacitor (46). Other devices, methods and systems are disclosed.
A self-tuning receiver/decoder for reception of FSK data transmission. An RF stage with resonant circuit (10) is tuned to a first of four possible transmitted frequencies for reception of such frequencies according to interrogation at such frequencies in sequence. Threshold (18) and counter circuits (12, 16) detect each frequency shift change of transmitted frequency and accordingly retune the resonant circuit to a subsequent unknown frequency by counting through a predetermined sequence for possible reception of each of such frequencies. Provision (24) is made for latching frequency shift data bit signals accordingly as output in a format identical to the frequency shift-keying RF format received. The receiver/decoder is especially useful for miniaturized transponder operation in which it alternates between receiving and transmitting modes, and is powered by capacitively stored charge in response to continuous transmission of the first frequency over a period.
A storage device and method stores tuning-frequency data, and extracts a tuning frequency from a received signal. Based on the stored tuning-frequency data, the tuning frequency extracted by the first extracting unit is adjusted. The storage device is accessed by an information processing apparatus, and data from the storage device are processed by an information processing method.
A transmitter or a method for transmitting data from a first antenna imposes a low level phase modulation, for example of less than 90.degree., on a carrier signal in accordance with a data signal to create a modulated signal, preferably having a carrier frequency and sidebands, and the sidebands may be substantially lower in amplitude than the carrier frequency. The method may be used in an identification system, for example for identifying luggage or other items. In another aspect of an apparatus or method for transmitting data, a phase modulation may be imposed on a carrier signal in accordance with a data signal to create a modulated signal having a carrier and sidebands, where the amount of phase modulation being selected is such that the amplitude of the sidebands is substantially lower than that of the carrier. Phase modulation may be imposed by a mixer.
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.
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 62.5 KHz; the controller formulates a digital message that includes the address of information stored in the transponder, synchronization bits, and command bits; the controller's digital message is detected by the transponder and causes the transponder to read its data information and then transmit a signal back to the controller that is modulated with the data information; the controller's digital message includes a complement signal that is transmitted coincident with each bit of the transponder's data information to be changed; and the controller's digital message includes a memory address whereby blocks of transponder data information are read, beginning with this address.
