Daily Image
27-11-2007
The PHAD Comes to Life!
| Submitter: | Tom Burgess and Tony Willis |
| Description: | Some pundits believe that phased-array systems consisting of Vivaldi antennas may be the Next Big Thing in radio astronomy instrumentation. ASTRON is of course the acknowledged world leader in this area, but DRAO in Penticton (Canada) is also not doing too badly. Here we show the DRAO PHAD (Phased Array Demonstrator) undergoing a near field laboratory test. The PHAD has 90 antenna elements in each of the horizontal and vertical planes. The 3 images show the PHAD array element responses for 3 different near-field sources: horizontally polarized, vertically polarized, and with a 1/4 wave rotator inserted. On the mid-left side, clamped in a vise, a single Vivaldi element driven by the 1.7 GHz signal generator (mid bottom) illuminates the array front face from a distance of about 30 cm. The inset in the top right is a screenshot of the (linear grayscale) element power display seen on the PC display below. The circular object inserted between the source and array in the last shot is a "meander line polarizer" which acts like a radio version of an optical quarter-wave plate to rotate polarization 90 degrees. In this case you can see that while the radiating antenna is in the vertical position, the strongest PHAD responses are in the horizontal plane. |
| Copyright: | Herzberg Institute of Astrophysics |
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