Multi-stage transponder wake-up, method and structure

A transponder in wireless electrical communication with an interrogator, said transponder comprising:

• a) an antenna, said antenna operable to receive an RF interrogation from said interrogator;
• b) a threshold detector in electrical communication with said antenna, said threshold detector operable to measure the power level of said RF interrogation, to compare said power level to a DC threshold, and to provide a threshold signal indicating whether said power level is greater than said DC threshold;
• c) a modulation detector in electrical communication with said antenna, said modulation detector for detecting modulation of said RF interrogation signal and for providing a modulation present signal, said modulation detector comprising a pulse generator for generating a series of pulses upon receipt of said threshold signal and a pulse counter for receiving said series of pulses and for providing said modulation present signal until the number of received pulses exceed a pre-determined number whereby said modulation present signal is enabled for a pre-determined duration of time during absences of RF energy:
• and
• d) a control circuit that upon reception of said threshold signal and said modulation present signal is enabled for receiving said RF interrogation from said antenna and for performing actions in response to data modulated upon said RF interrogation.

A method for receiving RF communications from an interrogator, comprising the steps of:

• a) receiving at an antenna of a transponder an RF interrogation from said interrogator;
• b) receiving by a threshold detector said RF interrogation;
• c) measuring by said threshold detector the power level of said RF interrogation;
• d) comparing by said threshold detector said power level to a DC threshold;
• e) providing a threshold signal from said threshold detector, said threshold signal indicating whether said power level is greater than said DC threshold;
• f) receiving by a modulation detector said RF interrogation;
• g) detecting in said modulation detector whether a pre-determined modulation signal is present;
• h) providing a modulation present signal from said modulation detector, said modulation present signal indicating whether said pre-determined modulation signal is present;
• i) receiving in a control circuit said threshold signal and said modulation present signal;
• and
• j) enabling said control circuit to receive said RF interrogation from said antenna and to perform actions in response to data modulated upon said RF interrogation.

A recognition system, said recognition system comprising:

• a) an interrogator that is selectively operable to transmit first signals;
• b) a transponder operable receive said first signals and operable to perform actions in response to said first signals, said transponder comprising:
• 1) a depletable energy source;
• 2) a first means for normally minimizing consumption of energy from the energy source by substantially inactivating the transponder;
• 3) a normally energized second means for determining if the magnitude of a signal received by the transponder exceeds a predetermined level, such level being the nominal minimum level of a first signal;
• 4) a normally de-energized third means, which is energized in response to the second means detecting that a transponder-received signal exceeds the predetermined level, for determining if the transponder-received signal is a first signal or a spurious signal and for activating the remainder of the transponder only if the received signal is a first signal.