composed of the CMSAs, we can reduce the re-radiation of the higher harmonic microwaves. We discuss parabolic type and hogline type reflectors in the following sections. We describe the former in detail. Parabolic Rectenna Figure 5 shows the rectenna with an offset parabolic reflector. Since the reflector is cylinder parabolic, the microwaves from the SPS are reflected in such a way that the microwaves concentrate on the focal line. For the sake of convenience, we consider the characteristics assuming that the reflector is composed of a metal sheet. Figure 6 shows a cross section of the rectenna using the cylinder parabolic reflector. The reflector is the offset parabola of focal length f. The focal line is shown by F. The elevation angle of the SPS is 0S. The rectifying diodes might be damaged if we place them on the focal line (F), because the microwave power density is too large. If we place the primary reflector of focus as shown in figure 6, we can lower the microwave power density below the damage level. Moreover, choosing an optimum Da, we can have a maximum value of RF to DC energy conversion efficiency of the diodes. Let us denote the length of arc primary radiator by Dj as shown in figure 6. Then we have the following equations: We can see that D/Dj indicates the concentration of the incident microwave power Figure 7 shows the power concentration (D/Dj) as a function of Da/f for several values of 9S. From figure 7, we can obtain the optimum Da which maximizes the energy conversion efficiency of the rectifying diode.
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