Abstract: Communications between a base station and a transponder that is powered by the base station are effected using a signal differentiation approach. A first radio frequency signal is communicated between the base station and the transponder to power the transponder, with the first radio frequency signal including noise and data for authenticating communications between the base station and the transponder. A second radio frequency signal is communicated between the base station and the transponder, with the second radio frequency signal including data for authenticating communications between the base station and the transponder. The detection of noise presented via the first radio frequency signal is mitigated while detecting data in the second radio frequency signal, via signal differentiation.

Abstract: Communications between a base station and a transponder that is powered by the base station are effected using a signal differentiation approach. A first radio frequency signal is communicated between the base station and the transponder to power the transponder, with the first radio frequency signal including noise and data for authenticating communications between the base station and the transponder. A second radio frequency signal is communicated between the base station and the transponder, with the second radio frequency signal including data for authenticating communications between the base station and the transponder. The detection of noise presented via the first radio frequency signal is mitigated while detecting data in the second radio frequency signal, via signal differentiation.

Abstract: Variable gain amplifiers comprised of multiple variable gain stages, wherein the gain of the various stages is controlled by comparisons of a control voltage with various reference voltages, in the preferred embodiment generated by the use of a series connection of multiple resistors connected to a supply voltage. These relative comparisons control current ratios determining the gain of each variable gain amplifier stage. By staggering the changes in current ratios, an overall gain change with control voltage which is smooth in gain in dB versus control voltage in volts may be achieved, generally without requiring use of current sources which are proportional to absolute temperature. The sequence of control of the individual gain states as a function of the control voltage in the preferred embodiment is selected such that the best performance is obtained with respect to noise, signal handling capability and distortion at every setting of the total gain.