LIST OF FIGURES





   Figure                                                  Page



     1.  Physical parameters of zigzag cells  . . . . . . . 4

     

     2.  k-diagram for a periodic show-wave structure . . . 6

     

     3.  Uniform zigzag model . . . . . . . . . . . . . . . 8

     

     4.  Uniform helical zigzag model . . . . . . . . . . . 8

     

     5.  Azimuthal radiation patterns of UZZ-1  . . . . . . 9

     

     6.  Azimuthal radiation patterns of UHZZ-1 . . . . . .10

     

     7.  Azimuthal radiation patterns of UHZZ-2 . . . . . .11

     

     8.  k-diagram of the zigzag structures . . . . . . . .12

     

     9.  Impedance locus of UZZ-1  . . . . . . . . . . . . 14

     

    10.  Impedance locus of UHZZ-1 . . . . . . . . . . . . 15

    

    11.  Parameters of a log-periodic helical zigzag . . . 18



12.  A photograph of a log-periodic zigzag antenna   

            over the ground plane . . . . . . . . . . . . .19

            

    13.  H-plane radiation patterns of LPHZZ-1  . . . . . .21

    

    14.  H-plane radiation patterns of LPHZZ-2  . . . . . .22

    

    15.  H-plane radiation patterns of LPHZZ-3  . . . . . .23

    

    16.  Input impedance referred to 50 ohms of LPHZZ-1 . .24

    

    17.  Input impedance referred to 50 ohms of LPHZZ-2 . .25

    

    18.  Far-field radiation patterns of LPHZZ-3A . . . . .28

    

    19.  Far-field radiation patterns of LPHZZ-3B . . . . .29

    

    20.  Far-field radiation patterns of LPHZZ-3C . . . . .30

    

    21.  Far-field radiation patterns of LPHZZ-3D . . . . .31

    

     

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