Subharmonic Passive Tags for Long-Range Far-Field Identification

The patent replaces electromagnetic delay elements with acoustic delay elements. Acoustic waves travel much slower than electromagnetic waves, allowing the same physical dimension to provide a much longer delay time. This substitution enables both high encoding data capacity (through longer delay) and extended interrogation range (through passive far-field operation) to be achieved simultaneously.

The patent changes the fundamental parameter of wave propagation speed by transitioning from electromagnetic waves to acoustic waves for the delay mechanism. This parameter change allows the delay element to achieve nanosecond-to-microsecond scale delays using practical physical dimensions, thereby increasing encoding data capacity without proportionally increasing device size, while also enabling far-field passive operation.

The patent utilizes acoustic resonance phenomena where specific frequencies are selectively amplified by resonant structures. By designing the acoustic delay element to operate at resonant frequencies, the system achieves high encoding data capacity through frequency-selective response without requiring proportionally larger tag areas, thereby minimizing transduction and propagation losses.

The patent employs periodic acoustic waves at specific resonant frequencies to encode information. The periodic nature of acoustic vibrations allows for efficient energy transfer and minimal loss, as the resonant structures naturally amplify these periodic signals. This enables high encoding capacity through frequency modulation without requiring excessive tag area that would increase propagation losses.

The patent replaces electromagnetic sensing and communication components with acoustic-based components. The acoustic delay element provides both the timing function for encoding and the sensing function, eliminating the need for separate batteries or integrated circuits. This substitution maintains passive operation (no maintenance) while achieving reliable far-field performance through resonant acoustic amplification.

The acoustic delay element serves multiple functions simultaneously: it provides the time delay for encoding data, acts as the sensing element for detecting target presence, and functions as the communication transducer for far-field passive operation. This multi-functionality eliminates the need for separate battery-powered components while maintaining reliable sensing performance and extended range.