Simple/basic Question on antenna feeding methods

[gbaerf]

microstrip antenna feeding methods

Hi all,

I am beginning with antenna designs.
I have a simple doubts on antenna feeding .

means
what are the different feeding methods...??? what are the advantages one over another.??? whats the criteria for choosing specific feeding method.??

I know some ...but steel need explanation ...

will be very much thank full if some body gives a breif explanation on antenna feeding....

a feeder couples the signal from active part to antenna right ....!!!

can any body give me a 3D picture of actual implementation where the TX or RX is connected to antenna through feeder :|

Thanks in advance
gbaerf

 

[aboozar.hamidipoor]

influence on feed impedance from parabolic dish

hello gbaerf,

many parameters could influence on choosing of antenna feeding method, but two of the most important parameters are these:
1-impedance matching for getting the best SWR
2-being balanced or unbalanced

suppose you have an antenna with an input impedance about 75Ω (e.g. dipole antenna) it is clear that the best feeding method is feeding by a 75Ω transmision line(such as coaxial cable) but you should pay attention also to this point that the coaxial cable is unbalanced line so you shoul use a balun befor antenna or in fact you need a parallel two wire line.

some of antenna such as helical antenna, horn antenna or microstrip antenna do not need balanced line but designing a balun for many of two parts antenna such as dipole is crocial.
for more information you could refer to antenna analysis and design books such as balanis books.
regards.

 

[koushikr_in]

feeding method of helical antenna

Hi,
in the case of parabolic dish antennas there is a parabolic reflector. the feed is placed at the focus of the parabolic reflector. the feed generally used is an horn.

Another popular feeding technique in the case of parabolic antennas is cassegrain geometry. here in addition to paraboloc reflector (main reflector) there is a hyperbolic sub reflector. the arrangement is such that the one focus of the hyperbola coincides with the focus of the parabola. the feed is placed at the other focus of the hyperbola.

other configurations are gregoian geometry (ellipsoid as sub reflector) and offset reflector antennas

 

[snkhan]

antenna feeding methods

Please see the Attached Thesis a very good one.