Review Article
Comparative Study of Antenna Designs for RF Energy Harvesting
Table 2
Various antenna shapes and the associated harmonic rejection
| Figure | Shape | Freq. | Harmonic rejection | Gain | Conversion efficiency |
| 4(a) | Circular patch with slots on the diameter | 2.45 GHz | Unbalanced slots achieve second harmonic rejection | 3.36 dBic CP gain | Efficiency would reach 53% and 75% with 1 K resistor load under ANSI/IEEE uncontrolled and controlled RF human exposure limit, respectively. | 4(b) | Microstrip circular sector antenna | 2.4 GHz | Circular sector antenna with sector angle of 240° and inset feeding point at 30° from the edge avoids harmonic radiation | 4.677 dBi | Maximum efficiency of 77.8% is achieved with a load resistor of 150 Ω and input power of 10 dBm | 4(c) | Rectangular patch with DGS | 2.45 GHz | An optimized length of the feeding line and DGS are used to reject the second and third harmonics | 6.4 dB | Conversion efficiency is 74% using a 1300 load resistor at a power density of 0.3 mW/cm2 | 4(d) | U-shaped slot in middle surface of inset-fed rectangular patch antenna | 2.4 GHz | U-slot antenna with inset feeding suppresses the harmonics | 6.96 dBi | Not specified |
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