Fig. 10. RF to DC conversion efficiency. INPUT FILTER A higher harmonic rejection filter (HHRF) between the receiving antenna and the DC blocking condenser is generally used in order that higher harmonics generated in the rectifier do not re-radiate into the free space and pollute the environment. A higher harmonic suppression filter built here is constituted by combination of two segments, that is, the HHRF and the CMSA with slits possessing a higher harmonics non-radiating characteristic. A photo of the HHRF is shown in Fig. 11. Table 1 shows the total insertion loss in dB which sums the power spectrum (dB) generated in the rectifier, the insertion loss of the HHRF, and the mismatch loss of the receiving antenna. The power spectrum was computed by a general purpose circuit simulation program. As shown in Table 1, the higher harmonics reradiation power in dB comparing with the 2.45 GHz input power is less than -50 dB for all of the higher harmonics. Therefore, the rectenna here has sufficient higher harmonic suppression characteristics.
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