Dual-frequency RFID tag with isolated inputs

An Integrated Circuit (IC) for a Radio Frequency Identification (RFID) tag configured to communicate with an RFID reader, the IC comprising:

• a first antenna terminal and a second antenna terminal, wherein the first antenna terminal is coupled to a first input to a first rectifier through a first coupling capacitor and the second antenna terminal is coupled to a second input to the first rectifier through a second coupling capacitor;
• and
• a third antenna terminal and a fourth antenna terminal, wherein the third antenna terminal is coupled to a first input to a second rectifier through a third coupling capacitor and the fourth antenna terminal is coupled to a second input to the second rectifier through a fourth coupling capacitor, wherein
• the first rectifier is configured to operate at a first frequency range;
• the second rectifier is configured to operate at a second frequency range;
• and
• the first and second antenna-terminal pair and the third and fourth antenna-terminal pair are electrically isolated such that a first antenna coupled to the first and second antenna terminals and a second antenna coupled to the third and fourth antenna terminals operate independently from each other when electrically coupled to the IC, and the first rectifier and the second rectifier do not share a common reference potential on the IC prior to respective couplings of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair to the first and second rectifiers.

An Integrated Circuit (IC) for a Radio Frequency Identification (RFID) tag configured to communicate with an RFID reader, the IC comprising:

• a first antenna terminal and a second antenna terminal, wherein the first antenna terminal is coupled to a first input to a first demodulator through a first coupling capacitor and the second antenna terminal is coupled to a second input to the first demodulator through a second coupling capacitor;
• and
• a third antenna terminal and a fourth antenna terminal, wherein the third antenna terminal is coupled to a first input to a second demodulator through a third coupling capacitor and the fourth antenna terminal is coupled to a second input to the second demodulator through a fourth coupling capacitor, wherein
• the first demodulator is configured to demodulate symbols according to a first protocol;
• the second demodulator is configured to demodulate symbols according to a second protocol different from the first protocol;
• and
• the first and second antenna-terminal pair and the third and fourth antenna-terminal pair are electrically isolated such that a first antenna coupled to the first and second antenna terminals and a second antenna coupled to the third and fourth antenna terminals operate independently from each other when electrically coupled to the IC, and the first demodulator and the second demodulator do not share a common reference potential on the IC prior to respective couplings of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair to the first and second demodulators.