The problem of locating and identifying objects (or persons) requires the system that has been designed using a small card carried by the object. When the object crosses the region of the high-frequency electromagnetic field created by a signal emitter, the card sends back a signal carrying a code characterising the object. The card is expected to be passive, and the code generator circuit is supplied by the microwave signal rectified on the card. In the paper the microwave rectifier realised by microstrip technology will be introduced. The nonlinear methodology studied here has given good agreement with the rectifiers using the Schottkybarrier diode at the frequency of 1.25 GHz. This methodology allows rectifiers to be created which give a direct voltage of more than two volts with input power of about ten milliwatts, and power efficiency of more than 85%.