900mhz dipole
I think your question how to you calculate the length of a standard half-wave dipole and its wire radius for it to cover the frequency range of 850 MHz to 950 MHz. Is this correct?
Given the frequency in MHz, the length in meters is
L (meters) = 143 / f(MHz)
The radius I would have to dig a bit to find, but in general, the thicker the wire the broader the frequency response.
-tip
YA but If V want to cover a wide range of frequencies then what be the lenght,,and radius?i didn't understand the formula,will u explain it more clearly. If U have any document about dipole antenna design so plz share wid me.
So if you want a dipole antenna to operate with a center frequency of 900 MHz, the length needs to be
L = 143/900 = 0.1589 meters
Here is a picture...
| <------------------- L -------------------> |
=============*=============
center feed
Does this make sense?
Was 'V' in your last message a typo or are you interested in a V-dipole?
-Tip
V was we,ok.
Now how can i develop it in matlab.its radiation pattern,rasiation resistance etc.
Try to find the book "Antenna and EM modeling with MATLAB" and write your code.
However, I guess, first you need to know a little bit more about antenna theory.
If you search the forums, I uploaded the CD for this book to one of them.
-Tip
As for pattern and other parameters, there is a great piece of software that is free. It is called 4NEC2 and it runs on Windows. It is based on the method of moments which is perhaps the most efficient way to model thin wire antennas.
-Tip
Can we use dipole antenna for mobile communiation,i.e:for 900MHz and 1800MHz frequency bands?
You are asking about a dual-band antenna. For the frequencies you just mentioned, 1800MHz is a harmonic of 900MHz so the same antenna would work for both, but performance would be degraded a bit at the higher frequency.
There are simple ways to get much better performance out of a dual band dipole and it involves loading it somewhere in the middle. A simple qualitative explanation is this. If you add an inductor (RF choke) at the center of each arm of your dipole, the high frequency would be confined to the shorter dipole, but the longer wavelength would see the full dipole. In this way, each wavelength sees a perfect half wave dipole. You can this driving on the road. Hams, police, and emergency vehicles will use this technique on their UHF/VHF radio antennas. You will see long whips with "black blobs" in the middle of whip.
-Tip
If I design two separate dipole antennas for each band,then I think performance would not be degraded. Is it right?what do you say?