that appears to be attractive is the use of staked-in alumina pins which supply the needed capacitance as well as the means of holding the structure together and spacing the core structure from the metal shield. A preliminary assembly that has withstood some initial thermal shock testing is shown in Figure 5-7. 5. 3 Interrelationships Between the Losses in DC Bussing, the Cross Section of the DC Busses, the DC Power Collected by Each Element, the Density of the Rectenna Elements, and the Required DC Output Voltage Level It has been recognized that the rectenna DC power must be collected locally at a significantly high voltage for two reasons. The first of these is to avoid excessive expense for collecting busses and the second is that the devices used for inverting de into 60 cycle power become highly efficient only at voltage levels of 1000 volts or more. How does this requirement tie in with the proposed fabrication technology? In order to get the required voltage it will be necessary to connect in series sections of rectenna line in each of which the individual diodes are operated in parallel. Also, it will be necessary to have an outbound section as well as an inbound section because of the series connection. This results in the circuit as shown in Figure 5-8. It is noted that the series connection of the sections can be accomplished without any additional expense as part of the fabrication procedure shown in Figure 5-4. The only requirements are that one side of the line be cut between successive sections* and that the direction of the diodes be reversed in successive sections. With this material as a background we are now in a position to derive a useful formula which relates the length of the structure to (1) the ratio of I^r loss to the collected de power, (2) the number of rectenna elements per unit length, (3) the de power level collected per unit element, and (4) the de resistance provided by the side rails of a single rectenna element. The formula follows : * Cutting the sections in this fashion would perturb the performance of the X/4 isolating section and needs to be looked at in more detail.
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