Fig. 4. Power spectrum of full-wave rectification. shown in Fig. 8 where directions of the slits coincide with the ones of current flow fot TM110 (dominant) mode so that the current of TM110 is not disturbed. The return loss and power obtained by this CMSA with slits are shown by solid lines in Figs. 5 and 6, respectively. TM010 and TM120 modes in vicinity to 2 f0 and 3 f„, respectively, are fully suppressed as shown in the figures. RF TO DC CONVERSION EFFICIENCY OF BRIDGE TYPE RECTIFYING CIRCUIT A bridge type rectifying circuit of the rectenna element is shown in Fig. 9 where 1SS154 (Toshiba Si Schottky) diodes are used. The rectifying circuit includes a DC-blocking condenser for the RF side and a bypass condenser for the DC side. The experimental result of the RF to DC conversion efficiency is shown in Fig. 10. The max efficiency of 63% is obtained when the load resistance is 200 ohms and RF inpul power 760 mW. Squares in Fig. 10 are the results obtained by computer simulation. Fig. 3. Radiation characteristic of CMSA.
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