TRANSPONDER EMPLOYING MICROSTRIP DOUBLE PATCH ANTENNA

摘要

A reader (114) interrogates a transponder (118) attached to a remote object. The transponder (118) includes a microstrip patch antenna having two segments (1, 2) connected together by a switch (3) each segment being one-half wavelength, the antenna being a full wavelength at the frequency of the interrogating signal. In response to a control signal, the switch (3) is opened and closed, thereby coupling and decoupling the two segments (1, 2) of the microstrip antenna. When the switch (3) is in the closed position, the two segments (1, 2) are out-of-phase with one another, the two producing a maximum reflected signal. When the switch (3) is in the open position, the two segments act in concert to produce a minimum backscattered signal. The backscatter signal is thus modulated in accordance with the control signal and is received at thereader where it is subsequently decoded to identify the remote object.