7单元长城WIFI天线.pdf

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Inverted Amos Se3, 5, 7, and 9 dipoles.

Inverted Amos antenna

After successful construction of the Amos antenna, I was curios to see what would happen if I
tried to take advantage of the short circuits at the end of the phasing lines radiation and get
higher gain from the antenna. Instead of suppressing this parasitic radiation by converting the
short circuit wires at the end of phasing lines in transmission line with help of reflector vicinity, I
decided to try to take advantage of this parasitic radiation as a constructive part of my new
antenna.

By rotating radiator 180 deg. and with additional optimization of dipoles and phasing lines
dimensions I got an antenna with higher gain and a little narrower horizontal diagram. It is
obvious that this undesired parasitic radiation now became a constructive part of the antenna’s
overall radiation and with its properly phased currents and fields improved Amos antenna in a
way that increases gain and narrows the horizontal diagram. In fact, the horizontal diagram
became narrower but not too much and the antenna preserves all good characteristics of the
Amos antenna. The Inverted Amos antenna is very useful as a sector antenna if you need a
narrower horizontal angle of coverage than Amos antenna has. It is interesting to see
comparative diagrams of Amos and Inverted Amos antenna each with seven dipoles. It is
obvious that the vertical radiation angle stayed almost unchanged as expected, but the horizontal
diagram became narrower and gain increased. See Fig. 3 and 4.

antenneX Issue No. 130 – February 2008 Page 2Fig. 3. Horizontal radiation diagram of Amos and Inverted Amos antenna with 7 dipoles.



Fig. 4. Vertical radiation diag