Modulated retroreflection system for secure communication and identification

A modulated retroflection system for secure communication and identification between two locations using only a single transmitter, comprising:

• (a) an interrogator at a first location, the interrogator including a transceiver for transmitting an interrogation signal to a second location and for receiving a modulated reflected interrogation signal from the second location, and
• (b) a semi-passive transponder at the second location for receiving, modulating, and reflecting the interrogation signal back to the interrogator, the semi-passive transponder including
• (i) a retroreflector having a dynamically controllable reflecting surface comprising
• a front modulating layer of material having a electro-responsive refractive index, said refractive index being controlled by a first modulated bias voltage for shifting the electrical phase of the interrogation signal passing through said front layer,
• an inner modulating and variably reflecting layer of material having an electro-responsive reflection coefficient, said reflection coefficient being controlled by a second modulated bias voltage for modulating the amplitude of the interrogation signal passing through said inner layer, and
• a back layer of electro-magnetic absorbing for absorbing residual electro-magnetic energy passing through the front modulating layer and the inner modulating and variably reflecting layer,
• the electro-responsive material comprising a mixture of barium, strontium, and titanium oxides, and
• (ii) a modulator electrically connected to said dynamically controllable reflecting surface for applying the first modulate electro-response to the front modulating layer and for applying the second modulated electro-response to said inner modulating and variably reflecting layer, the first and the second modulated electro-response being used to modulate phase angle, refractive index, and dielectric constant of the electro-responsive material and thereby shift electrical phase of the reflected signal and for encoding communication and identification information onto the interrogation signal prior to it being reflected by the reflecting surface.

A modulated retroflection system for secure two-way communication and identification, comprising:

• (a) a transceiver at a first location for transmitting a signal to a second location and for receiving a modulated reflected signal from the second location, the transceiver encoding communication and identification information onto the signal, and
• (b) a transponder at the second location for reflecting the signal, the transponder encoding additional communication and identification information onto signal being reflected, the transponder comprising
• a retroreflector having a first layer and a second layer composed of an electro-responsive material having a electro-responsive refractive index and a electro-responsive reflection coefficient,
• said first layer for substantially modulating the electrical phase of the received signal, and said second layer for substantially modulating the amplitude and reflecting the received signal, said retroreflector further comprising a third surface for absorbing residual signal passing through the first and second layers, and
• a modulator electrically connected to the first layer and the second layer for applying a first and a second modulated bias voltage respectively on the electro-responsive layers to modulate phase angle, refractive index, and dielectric constant of the electro-responsive material and thereby shift electrical phase of the reflected signal.

A modulated retroflection system for secure communication and identification, comprising:

• (a) a transceiver at a first location for transmitting a signal to a second location, and for receiving a modulated reflected signal from the second location, and
• (b) a transponder at the second location, the transponder phase shifting, amplitude modulating, and reflecting the signal back to the transceiver, the transponder comprising
• a retroreflector having a first layer composed of an electro-responsive material having a electro-responsive refractive index, said first layer for modulating the electrical phase of the received signal, said retroreflector further comprising a second surface for reflecting the signal passing through the first and layer, and
• a modulator electrically connected to the first layer for applying a modulated bias voltage to modulate phase angle, refractive index, and dielectric constant of the electro-responsive material and thereby shift electrical phase of the reflected signal.

A modulated retroflection system for secure communication and identification, the modulated retroflection system comprising:

• (a) a transceiver at a first location for transmitting a signal to a second location, and for receiving a modulated reflected signal from the second location, and
• (b) a transponder at the second location, the transponder phase shifting, amplitude modulating, and reflective the signal back to the transceiver, the transponder comprising
• a retroreflector having a first layer composed of an electro-responsive material having an electro-responsive reflection coefficient,
• said first layer for modulating the electrical phase of the received signal, and a second layer for modulating the amplitude and reflecting the received signal, said retroreflector further comprising a third surface for absorbing residual signal passing through the first and second layers, and
• a modulator electrically connected to the first layer and the second layer for applying a first, and a second independent modulated bias voltage respectively to modulate phase angle, refractive index, and dielectric constant of the electro-responsive material and thereby shift electrical phase of the reflected signal.