Abstract: A RFID transponder having a high quality factor antenna (LR), and a resonance capacitor (CR) coupled to the high quality factor antenna (LR) for providing a resonant circuit (LR, CR), wherein the RFID transponder is adapted to vary the quality factor of the resonant circuit (LR, CR) such that the quality factor is low during downlink data transmission when the RFID transponder receives data through the antenna (LR), and the quality factor is high during uplink data transmission, when the RFID transponder transmits data.

Abstract: For reading the data stored in a transponder by means of an interrogation device, the interrogation device at first receives the background noise for the purpose of detecting interference frequencies present in this background noise. On the basis of the interference frequencies acquired, coefficients for an adaptive filter are computed by means of which this filter may be tuned in such a way as to suppress the interference frequencies. The response signal from the transponder with the superimposed background noise is received by the interrogation device and routed through the adaptive filter which acts to suppress the interference frequencies. The signal available at the output of the filter can then be demodulated for the purpose of reading the data stored.

Abstract: A corrected digital response signal is generated from a corrupted transponder response signal by receiving the response signal an odd number of times, greater than one, and sampling each received response signal a predetermined number of times. Then, the sample values from each transponder response signal are compared to one another and a majority sample value is obtained. The majority sample value is the value ordained by the majority and therefore represents the corrected response signal value. Alternatively, if time does not permit reception of more than one transponder response signal, additional response signals may be generated from the originally received response signal by shifting the received response by a predetermined number of samples to the right and by shifting the received response by a predetermined number of samples to the left to generate second and third response signals.

Abstract: A novel addressing scheme for an RF-ID system or LAN network is presented in which an interrogator(reader) addresses a set of transponders, each transponder in this set having a common addressing scheme, and the addressed transponders respond only upon the matching of their own address with the received addressing scheme. The addressing scheme comprises a fixed size sub-address and a variable size mask. For example, assuming that the transponder address is 32 bits, the implementation of the addressing scheme can choose 4 bits for the size of the sub-address and 0, 4, 8, 12, 16, 20, 24, 28 bits for the size of the mask. By varying the addressing scheme according to the algorithm in FIG. 4, the reader will in time interrogate all the transponders individually, thus receiving their unique address and achieving the requested exhaustive inventory.

Abstract: Transponder signal collision avoidance system incudes a reader and wireless HDX or FDX type transponders (A, B) are disclosed, interrogated by the reader (R) by alternately powering and then reading through cycles corresponding to a number of possible transponders in the interrogation field. The cycles, which include reader power pulses, signify addresses of respective possible transponders, whether in or out of the field. The transponders for this purpose count reader power pulses by end-of-burst detection, increasing a stored count value with each reader power pulse. The transponder responds to the reader by transmission if and only if a stored count value in a read cycle matches a respective transponder address, preventing the transponders from transmitting telegrams interfering with each other.