What are the type of antennas ?

[tarakapraveen]

Hi friends,

I have observed different types of antennas on the cell phone towers .

Some of them are like 4 feet length i though that those are Dipole antenna.Is it correct?

second type is like paraboloid.

Please clear me what are the different types of antennas used on cell phone towers and what is the range of coverage and the impedance and the power .


Thanks in advance
Taraka

 

[mindrover]

Taraka,

Those 4' antennas you are seeing are normally what is refered to as a "panel antenna" with a specific Horizontal Beam Width" ... usually (65-90)deg. These are also refered to as "Directed DiPoles" in certain models. The size of each is proportional to the frequency used and the gain needed. They can range from 1' to 8'+ depending on how many elements are stacked inside for gain and direction. Most can handle total input powers approaching 500+watts. The range for coverage for any system is going to be unique for each tower per the actual need. I pulled the info below from h**p://www.fcafe.com to help explain free space loss as it relates to the antenna gian /height of the antenna/ and power.

As the transmitted signal traverses the atmosphere its power level decreases at a rate inversely proportional to the distance traveled and proportional to the wavelength of the signal. The formula used by RF Workbench accounts for only the diminishing voltage without accounting for absorption or dispersion by the atmosphere. Click here for a 1-way calculator and here for a 2-way (radar) calculator.


Path loss equation formula for free space:

Free space loss = 36.56 + 20Log10(Frequency) + 20Log10(Distance in miles)


The Friis Equation (H.T. Friis, 1946) gives a more complete accounting
for all the factors from the transmitter to the receiver:

Path loss equation formula
where: GTx = transmitter antenna gain
GRx = receiver antenna gain
λ = wavelength (same units as d)
d = distance separating Tx and Rx antennas
L = system loss factor (≥ 1)

Information in the transmitted signal is seldom concentrated at a single frequency, so the path loss will actually be different for every frequency component in the signal. Fortunately, the ratio of the bandwidth to center frequency is usually small enough to not matter. Still, a signal that is transmitted with a constant power across some bandwidth will appear at the receiver with a power slope that decreases at the upper end of the band.

The parabolic antennas you are seeing are highly directional / high gain used for several tasks. One being microwve backhaul.

Try this link as well from Terrabeam:
**broken link removed**



Hope this helps,
mindrover

 

[solidsnike]

take this files

h**p://

 

[fahadmunir]

for more details about antenna, u may take help fromthe following book.

Antenna Theory by ballanais. 2nd edition. easily available in libraries and universities.


or can download latest papers from
www.portal.acm.org.
this link is working