i) how to excite diferent phase to antenna? ii) why my antenna gives -ve gain?
how can i make each antenna radiate different phase (or was it pointing angle? maybe i wrong in term) if its come from one input feed. thank you
i hope, it can be realizeable without phase shifter, but if its really need the phase shifter to produce diferent phase, then at which part should i put it? is it between power divider and antenna?
thanx
ii)
i simulate my antenna and it gives negative gain, and radiation eff. of -6dB
i know the result is wrong, can anyone suggest, what can i do so that my antenna really can gives positive gain, thanx again
i and ii using microstrip technology , and CST software
=]
One way to change the phase between elements is to feed them with transmission lines with different lengths. One scheme to move the array beam is to include switches and different line lengths to shift the array patten.
Negative gain isn't necessarily wrong (although in this case I would think it indicates an error). Gain is Directivity minus insertion loss. If you happen to have significant loss in your feed the gain would be reduced and could in fact be negative.
There is a wealth of information on the subject in the technical literature. Start with Antennas by John Kraus. Hansen has a number of antenna array books as well.
What is the gain of a single element? Now add some feed line, what do you see? How about the insertion loss, s21, of just the feedline, what do you see? Are the components working correctly before they are connected?
thx my friend =]