Abstract: A multi-tone multi-band tunable millimeter-wave synthesizer is provided. In some embodiments, the multi-tone multi-band tunable millimeter-wave synthesizer is configured to simultaneously generate multiple frequency tones for space-borne beacon transmitter for atmospheric radio wave propagation studies. The apparatus includes a comb generator, which puts out evenly spaced harmonic frequencies of the input signal, which are coherent, tunable, and the number of tones or combs is scalable over a wide range of frequencies. These harmonics or tones are amplified to the power level needed for radio wave propagation studies. The amplified signals are transmitted as beacon signals from a satellite to a ground receiving station.

Abstract: An antenna (10, 110, 210) comprising a ground layer (30, 130, 230), a feed layer (50, 150, 250), an antenna layer (40, 140, 240) and a transparent dielectric substrate (20, 120, 220) interposed between two of the layers (30 and 40, 140 and 150, 230 and 250). An electromagnetic field is produced between the ground layer (30, 130, 230) and the antenna layer (40, 140, 240) when the feed and ground layers (50 and 30, 150 and 130, 250 and 230) are exposed to a microwave frequency above 3,000 megahertz for transmission and when the antenna and ground layers (40 and 30, 140 and 130, 240 and 230) are exposed to a microwave frequency above 3,000 megahertz, for reception. The ground layer (30, 130, 230), feed layer (50, 150, 250) and antenna layer (40, 140, 240) are made of an optically transparent and electrically conductive material. About 30% of the visible light impinging on the antenna (10, 110, 210) passes through the antenna.