In this article, a design of planar circularly polarized slot antenna is presented. The proposed antenna has a simple structure ABSTRACT: An indoor wireless millimeter wave system with an optical orthogonal frequency division multiplexing (OFDM) signal link was developed. Channel modeling for the multipath system was proposed, and the channels in a 60 GHz band were measured. Based on the model, system parameters were evaluated for various subcarrier modulations in OFDM systems. Link performance in a typical office environment under the line-of-sight channel condition and with a 30 km optical OFDM link was measured. V C 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:491-495, 2011; View this article online at wileyonlinelibrary.com.

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By adding a square wave of noise to the input of an ultra‐low‐noise receiver via a directional coupler, a radiometer with a sensitivity greater than a Dicke type can be achieved when the basic system temperature is less than 18°K. A noise‐adding radiometer is compatible with a communications receiver and has been used (i) to measure and monitor the absolute system temperature and (ii) to check the boresighting of a space communications antenna by detecting and tracking radio stars.

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