Before ending the discussion of rectifier configurations, attention is called to a pseudo full-wave rectifier using only two conductors. Figure 9-15 shows a two-terminal pair structure that is a low-pass filter element made up of the capacitance of the diodes themselves with an intervening inductance whose value is such that the filter operates at or near the upper cutoff frequency. This filter section then behaves as a full-wave rectifier in the sense that current flows into the dc busses on both halves of the rf cycle. * Such an element could have a considerable amount of energy storage, i. e. , a significant Q. If the device were fed from one side only, the symmetry of the rectification process would be affected, being less affected with the higher Q values. The symmetry could be restored, regardless of the Q value, by feeding the network from adjacent half-wave dipoles assumed to be excited in the same phase. In most of the experimental work to date, only a single dipole has been involved with the rectifier. This permits designing and testing a single element of the rectenna according to the procedure that has been used successfully. This procedure makes use of a section of expanded waveguide into which the complete element is matched. Accurate measurements of efficiency can be made, and the cross-section of the expanded waveguide has been correlated wi th the area taken up by the element in the finished rectenna, Figure 9-15. Pseudo Full-Wave Two-Conductor Rectifier
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