as a rectifier, but there are other arrangements which could incorporate several diodes in a function other than pure parallel operation. For the present discussion, however, attention will be focused on the filter. It will be noted first that the low-pass filter, shown in Figures 9-4 and 9-11, allows the top and bottom of the network to be at different dc potentials. It therefore follows that the conductors which form the top and bottom of the filter can be used as dc busses to transport the rectified power to the edges of the array. A second aspect of the filter that must be taken into consideration is that a physical space is required for the construction of the filter. The space required is roughly proportional to the number of filter sections required, and there are likely to be at least two. A convenient place to put these filters is in the space between two of the half-wave dipole antennas as shown. A second consideration is the other possible rectifier configurations that could be employed. If a full-wave rectifier is employed as in Figure 9-12, an additional bus will be required, and if it is kept in the same plane as the other conductors without intersecting them, it must pass through the center line of the capacitances. This is probably not practical. If a full-wave bridge-type rectifier is used as in Figure 9-13, the problem becomes even more acute, since two additional terminals are created. If the terminals of successive rectifiers are connected in parallel, two additional busses will be required. The early rectennas built internally at MSFC and at Raytheon used bridge-type rectifiers and the power was collected by a single dc bus, connecting the elements in series. But these rectennas contained no filters between the rectifiers and the dipole antennas. If filters were inserted, the schematic would then have to look like that of Figure 9-14 and there is no single-plane topological solution since the filter is a two-terminal pair device. There is also the problem of a strong second harmonic content at terminals B-B1 and the suppression of its radiation from the series bus. It would therefore appear that if a full-wave rectifier were to be used an additional plane would be required for bussing the power. This does not necessarily rule out these configurations but there is no doubt that it places them at a disadvantage with the half-wave rectifier configuration shown in Figure 9-11.
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