Frequency hopping spread spectrum passive acoustic wave identification device

A method for interrogating a passive acoustic transponder, producing a transponder signal having characteristic set of signal perturbations in response to an interrogation signal, comprising:

• (a) producing an interrogation signal having a plurality of differing frequencies;
• (b) receiving the transponder signal from the passive acoustic transponder;
• (c) mixing the transponder signal with a signal corresponding to the interrogation signal, to produce a mixed output;
• (d) integrating the mixed output to define an integrated phase-amplitude response of the received transponder signal;
• and
• (e) analyzing a plurality of integrated phase-amplitude responses corresponding to the plurality of differing frequencies, to determine the characteristic set of signal perturbations of the passive acoustic transponder.

A method for identifying a passive acoustic transponder, having a set of characteristic signal perturbations selected from a signal perturbation space having a plurality of degrees of freedom, and producing a perturbed signal in response to an interrogation, comprising the steps of:

• (a) interrogating the passive acoustic transponder with a frequency hopping spread spectrum signal, having a psueodorandom sequence of a plurality of different frequencies, and a stationary frequency dwell period;
• (b) receiving and demodulating the perturbed signal based on a representation of the frequency hopping spread spectrum signal;
• (c) determining an average phase-amplitude response of the demodulated perturbed signal during a plurality of dwell periods;
• and
• (d) analyzing the average phase-amplitude response from the plurality of dwell periods to determine the values of the plurality of degrees of freedom.

A system for determining characteristics of an acoustic wave transponder, producing a transponder signal having characteristic set of signal perturbations in response to an interrogation signal and an internal reference, comprising:

• (a) an interrogation signal generator, producing a non-stationary interrogation signal hopping to a plurality of differing frequencies;
• (b) a receiver, for receiving the transponder signal;
• (c) a demodulator, for demodulating a signal dependent on characteristics of the transponder from said interrogation signal, to produce a demodulated output;
• (d) a phase-amplitude detector, detecting a phase-amplitude relationship of said demodulated output with respect to the reference;
• and
• (e) an analyzer, sequentially receiving a plurality of detected phase-amplitude relationships corresponding to said plurality of differing frequencies, for determining the characteristic set of signal perturbations of the acoustic wave transponder.

A method for analyzing a frequency hopping spread spectrum interrogated passive acoustic transponder comprising the steps of:

• receiving a transponder signal;
• demodulating the transponder signal with a representation of the interrogation signal;
• integrating the demodulated transponder signal from a frequency hop with an effective integration time constant smaller than a duration of the respective frequency hop;
• determining a relative phase-amplitude shift of the demodulated signal due to interrogation signal perturbations within the transponder, based on the integrated demodulated transponder signal, over a plurality of frequency hops;
• and
• analyzing the determined phase-amplitude shifts to determine a set of component delays within the transponder.

A method for analyzing a frequency hopping spread spectrum interrogated passive acoustic transponder comprising the steps of:

• exciting a transponder with a spread spectrum interrogation signal in a plurality of differing excitation states;
• receiving modified signals from the transponder under the plurality of differing excitation states;
• demodulating the received signals;
• filtering the demodulated received signals with a wide bandwidth filter;
• determining a characteristic perturbation of the demodulated received signals for each differing excitation state;
• and
• analyzing the determined characteristic perturbations to determine a set of component perturbation elements within the transponder.

A method for interrogating a passive acoustic transponder with a non-narrow band frequency interrogation signal having a plurality of differing excitation states, comprising the steps of:

• receiving modified signals from the transponder under the plurality of differing excitation states;
• demodulating the received signals;
• filtering the demodulated received signals with a wide bandwidth filter, having a time constant which is small with respect to the period between transitions of differing excitation states;
• determining a characteristic perturbation of the demodulated received signals for each differing excitation state;
• and
• analyzing the determined characteristic perturbations to determine a set of component perturbation elements within the transponder.

A passive radio frequency transponder method for reading information encoded into a passive device, having a maximum time constant, as a set of phase-amplitude variations of signals having respective variation time constants shorter than said maximum time constant, comprising the steps of:

• exciting the passive device with a set of signals having differing frequency components;
• receiving a modified set of signals from the passive device with phase-amplitude variations;
• and
• filtering the received signals with a filter having a time constant comparable in magnitude to the maximum time constant of the passive device.

A passive acoustic transponder interrogation system, comprising:

• a transponder, producing a transponder signal having characteristic set of signal perturbations in response to an interrogation signal;
• a signal generator, producing an interrogation signal having a plurality of differing frequencies;
• a receiver, for receiving the transponder signal;
• a mixer, for mixing the transponder signal with a signal corresponding to the interrogation signal, to produce a mixed output;
• an integrator, integrating the mixed output to define an integrated phase-amplitude response of the received transponder signal;
• and
• an analyzer, receiving a plurality of integrated phase-amplitude responses corresponding to the plurality of differing frequencies, for determining the characteristic set of signal perturbations of the passive acoustic transponder.

A method for identifying a passive acoustic transponder or an object associated therewith, comprising:

• placing a passive acoustic transponder in proximity to the object, the transponder having a set of characteristic signal perturbations selected from a signal perturbation space having a plurality of degrees of freedom, and producing a perturbed signal in response to an interrogation;
• interrogating the passive acoustic transponder with a pseudorandom order, frequency hopping spread spectrum signal, having a sequence of a plurality of different frequencies, and a dwell period;
• receiving and demodulating the perturbed signal based on a representation of the pseudorandom order, frequency hopping spread spectrum signal;
• determining an average phase-amplitude response of the demodulated perturbed signal during a plurality of dwell periods;
• and
• analyzing the average phase-amplitude response from the plurality of dwell periods to determine the values of the plurality of degrees of freedom.