| 摘要 |
A half-duplex passive transponder including: a resonant circuit including an antenna and input capacitor and configured to allow an electrical signal to oscillate in the resonant circuit when periodically receiving across the antenna an activation signal from a reader; at least one switch between the input capacitor and a storage capacitor so the two capacitors are in parallel when the switch is turned on; a peak voltage detector configured to measure amplitude of the electrical signal oscillating in the resonant circuit; and a variable voltage threshold determination circuit configured to trigger each of plucking pulses when voltage of the oscillating electrical signal substantially attains a variable voltage threshold in a respective period before an extremum of the oscillating electrical signal and in a half-cycle of the extremum, to thus deliver plucking pulses during a transmission period in the resonant circuit to maintain a certain amplitude of the oscillating electrical signal. |
