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June 17, 2010
Dear Mr. Kumar: With interest I read your paper in the MWRF May issue, "Antenna Assists MW Power Transmission." I am not sure if I understand the arrangement of your rectenna in Fig. 1. In fact, the antenna is loaded with a Schottky diode; ...

Dear Mr. Kumar:
With interest I read your paper in the MWRF May issue, "Antenna Assists MW Power Transmission." I am not sure if I understand the arrangement of your rectenna in Fig. 1. In fact, the antenna is loaded with a Schottky diode; the capacitor and tuning stub seem to me to be on a wrong side of the antenna-detector combination. The "Load" is possibly the DC load.

On p. 73 you refer to the design by Bharj et al. who designed a rectenna with a Schottky quad bridge and achieved ~80% RF/DC efficiency. Therefore, I do not understand how could you achieve an even higher efficiency by using a single-phase, singlediode rectifier diode? Such a rectifier should in principle only achieve less than 50% efficiency.

Please advise.

I have followed many wonderful plans by celebrated names like NASA, JAXA, etc., with microwave power transmission over short as well as long distances. Those engineers and scientists seem to include the propagation loss known since Newton: that the electromagnetic- wave power decreases with an inverse square of distance. Radio amateurs utilize the Moon to reflect their signals from it, to communicate. We use satellite communications to transmit data and TV from geostationary orbit. We pay dearly for that loss to get the information, not the power. A typical propagation loss at 5.8 GHz from the Moon is ~166 dB, from a geostationary satellite, ~156 dB. Nowhere in the publications you referred to or anywhere else could I find how the authors hope to overcome such loss.

Mr. Criswell, a physicist once argued that "a huge antenna on the Moon will operate WITHOUT propagation loss by focusing the power to the Earth in the NEAR FIELD." I would like to see such an antenna , and see how to transmit power without the propagation loss. And with me I am sure thousands of satellite communication engineers would want to have such miraculous antennas like planned in those projectsup to now, not knowing such miracles, we only know how to transmit information by overcoming the huge propagation loss. How can they talk about POWER EFFICIENCY?
Best regards,
Jiri Polivka

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