NEW COAXIAL COLINEAR ANTENNA FOR WIND PROFILERS

SSI PROPOSES TO TEST A NEW ANTENNA FOR WIND PROFILERS WHICH WILL REDUCE THE COST OF PRESENT ANTENNAS AND IMPROVE THE PERFORMANCE AS WELL. NOAA PLANS TO PROCURE ABOUT 200 PROFILERS IN THE NEXT FEW YEARS AT A COST BETWEEN 300 TO 400THOUSAND DOLLARS PER UNIT. THE ANTENNA ALONE ACCOUNTS FOR ABOUT ONE THIRD OF THE COST. SSI EXPECTS TO CUT THAT COST IN HALF OR BETTER. PRESENT ANTENNAS REQUIRE TWO COAXIAL COLINEAR (COCO) ARRAYS ORTHOGONAL TO EACH OTHER TO PROVIDE E-W AND N-S COMPONENTS OF THE WIND AS WELL AS A THIRD BEAM TO MEASURE ANY VERTICAL WINDS. OUR ANTENNA IS ALSO A COCO AND CAN PROVIDE FIVE BEAMS WITH ONLY ONE ARRAY. THERE ARE MANY ADVANTAGES TO USING FIVE BEAMS INSTEAD OF ONLY THREE. IN NOAA'S PRESENT ANTENNA, EACH ARRAY IS MADE UP OF APPROXIMATELY TWENTY-FOUR COCO STRINGS. THE BEAM IS TILTED IN A DIRECTION NORMAL TO THE STRINGS BY SHIFTING THE SIGNAL PHASE BETWEEN STRINGS. THE INNOVATIONS IN THE PROPOSED ANTENNA IS TO TILT THE BEAM IN EACH DIRECTION ALONG THE STRING AS WELL AS IN EACH DIRECTION NORMAL TO THE STRING ORIENTATION. THUS, WE HAVE FOUR BEAMS TILTED TOWARDS EACH CORNER OF ONE ARRAY. WHEN ALL STRINGS ARE EXCITED WITH THE SAME PHASE, A QUASI-VERTICAL FIFTH BEAM IS PRODUCED.