Hybrid ultrasonic and radio frequency identification system and method

A radio frequency identification tag, comprising:

• two or more combination resonator/reflectors, wherein each of said combination resonator/reflector includes:
• a radio reflector;
• and
• an ultrasonic resonator coupled to said radio reflector to modulate a reflection of said radio reflector with a resonance of said ultrasonic resonator for detection by a reader, wherein each of said combination resonator/reflectors is tuned to a unique pair of selected ultrasonic frequencies and selected radio frequencies.

A method of identifying an article, comprising:

• associating with said article a radio frequency identification tag, said radio frequency identification tag including two or more combination resonator/reflector, each of said combination resonator/reflector including an ultrasonic resonator coupled to a radio reflector to modulate a reflection of the radio reflector with a resonance of the ultrasonic resonator, wherein each of said resonator/reflector is tuned to a unique pair of selected ultrasonic frequencies and selected radio frequencies;
• transmitting, from a tag reader, a tone having a first ultrasonic frequency to said radio frequency identification tag;
• transmitting, from said tag reader, a radio signal having a first radio frequency to said radio frequency identification tag;
• and
• determining, using said tag reader, if a radio signal having said first radio frequency is reflected from said radio frequency identification tag and if said reflected signal is modulated at said first ultrasonic frequency.