More rarely they are slanted (with an angle less than 90[degrees]); in the latter cases the bases of tubercles can be round, oval, angular, fan- or
halberd-shaped (Fig.
As the growing interest in multiband CP antennas, various designs of multiband circularly polarized antennas have also been proposed, including the dual-band CPW-fed circularly polarized antenna with two orthogonal slots [5], a dual-band CP antenna with two square slots in the opposite corner of the ground plane and two truncated corners of the main slot [6], and a dual-band circularly polarized antenna with slots loaded in the two opposite corners and the
halberd-shaped strip connected at the end of the signal line [7].
To increase the bandwidth performance, square-slot antennas with multiple monopole elements [15] or a
halberd-shaped feeder [16] were proposed; these allow for 3 dB AR bandwidths of 28.03% and 29.1%, respectively.
A printed square slot antenna (PSSA) excited by a
halberd-shaped CPW feed line for circular polarization in the S-band was proposed in [10].
This halberd-shaped feeding signal line will be seen later to account for the CP operation in the high-frequency portion of the designed CP band.
1(a)) of the y-directed strip of the proposed halberd-shaped feeding structure and the left and upper edges of the [L.sub.s]-wide square slot.
This can be achieved by adding an additional y-directed feeding strip section with width [w.sub.1] and length [l.sub.2] to the inverted-L feeding signal line of the type 2 antenna with [l.sub.p] = 18.5 mm to form a halberd-shaped feeding signal line.