Excerpts from the video can be accessed (when noted) by clicking on the sample images. These highlights range from 1.5 MB to 2.4 MB and are 14 to 31 seconds long.
|An optically controlled phased array antenna can be used to generate remotely controlled steerable pencil-thin beams utilizing multiple-GHz RF frequencies. This video introduces a novel serially-fed architecture which we have implemented to broadcast video for indoor wireless applications. We also show the results of experiments which broadcast NTSC base-band video over such links. Also, as an example for an application of this antenna, we will show received images from our video broadcast experiments. Video broadcast was achieved using oversampling of an NTSC base ban video by placing mixers after the transmit gate. Our receiver used a second local oscillator to mix the received signal down to VHF frequencies. Television circuitry then demodulated and amplified the VHF back to the original NTSC base-band signal.|
The following shows the laboratory setup of the optical and electrical components (right), as well as the phased array transmit elements and receiver. Both video clips are actual video, broadcast through our antenna system as shown by blocking the radiated beam.
|To investigate degradation of image quality due to broadcast, we recorded an image directly onto a VHS videocassette and compared it to the received broadcast image. There is little perceivable difference between the quality of transmitted and received images. Color bars were also broadcast for a more direct color level comparison. A measured histogram of the subtracted image color levels between the direct and transmitted images indicates that the main degradation in signal quality is typically 5 color levels out of 256 color levels. This is less than two percent.|
Finally, to investigate beam directionality, we switched toward and away from a node of a radiated beam front. We show complete loss of signal and have a power discrimination of approximately -30 dB. As expected, we have a similar loss of signal when the fiber feed is disconnected (right), and when one element of the phased array is blocked.