Circuit frequency following technique transponder resonant

摘要

A transponder system (10) includes an interrogation unit (12) that transmits a first frequency F1 representing a binary zero, and a second frequency F2, representing a binary one. These signals are transmitted from an interrogator resonant circuit (22) within a radio frequency module (16). The transponder system (10) also includes a transponder unit (14) that receives a transmit frequency signal (51) from the interrogation unit (12) at a transponder resonant circuit (42). The transponder resonant circuit (42) is tuned to the first frequency F1 and the second frequency F2. A transponder control module (44) detects a change in the transmit frequency signal (51) from the interrogation unit (12) by a decrease in the voltage amplitude with the transponder resonant circuit (42). The transponder control module (44) repositions a switch circuit (48) that connects and disconnects capacitors within the transponder resonant circuit (42) to match the frequency of the transponder resonant circuit (42) with the new transmit frequency signal (51).