Broadband antennas

I want to know, why is so important these kind of antennas?, also, I′M LOOking for their application. Thanks.

They are used in two different situations. For monitoring, they should cover the frequency range monitored. For transmitting, they should cover the frequency range that government licenses are issued for frequencies to use. The military is one example of the need for both of these uses.

Nowadays, the standards for different communications systems (GSM,DCS,UMTS and WIFI) require antennas to cover broad frequency bands. For DCS for example the antenna should cover from 1710MHz to 1880MHz (170MHz bandwidth). If you go to more advanced systems, like UMTS the coverage should be from 1920 to 2170MHz (250MHz).

Another situation you need a broadband antenna is in commercial FM broadcasting.
Here in Italy trasmitting frequencies are assigned by government and rules are different between two different city, so you need to buy a TX and antenna for covering all FM radio band (88-108 MHz), to be able to transmit on a particular assigned channel.

Angelo.

two more cents, for UWB implementation:
for multiband-OFDM scheme, each transmitting/receiving antenna need 500MHz frequency bandwidth.
for radio pules shceme, FCC allocated unlicensed radio spectrum 3.1~10.6GHz.

for wireless communication, what we are fighting for is the available bandwidth, wider bandwidth, higher bit rates. The hugh market of mobile wireless communication made us struggling with wider frequency bandwidth.

Regards,