how to change the gain of antenna?

Folks,

I have designed a dipole antenna.
But I want to re-use the antenna resonating at the same frequency(866MHz) but with different gain.
What can be done to acquire the scenario using the same set-up?

Thanks!

If you have designed a dipole antenna with a gain of 6dB then it has tobe patented.Because nominally gain of an antenna is around 2dB.i dont know how you came up with that number.

Regards
ChachitoEL.

Sorry! I was wrong with my statement. I guess whatever Peak Gain shown in "Calculate Antenna parameters" is in dBi.
If I have restricted transmit power of 1W but if I need to achieve of EIRP of 4, what should I do?
The only thing within my hands is to design antenna with a Gain of 4 or 6dBi.
Please help me out.

Thanks!

To get any more gain than the 2.5dBi from a dipole is going to require a more complex antenna built around the dipole.
For omni directional you could use a colinear which is basically a set of stacked 1/4, 1/2 or 5/8 wave elements and for ~ 800MHz gains up to 10dBi would be relatively easy to achieve.

If you dont need omni directional and are happy with a directional system then you would use antennas like corner reflectors and Yagis.
A corner reflector with 1 wavelength sides will give ~ 10dBi gain
A 3 element Yagi will give ~ 6dBi gain

BUT I clarify to you again You are NOT going to get more than ~ 2.5dBi out of a single dipole,
in a famous quote, "ye canne break the laws of physics"

cheers
Dave

If presuming a λ/2 dipole. A 5λ/2 dipole has about 6 dBi gain, but there are better antennas of comparable size.

RFID regulations usually restrict the maximal e.r.p., are you sure that applicable regulations allow 4 W?

try by changing the material

What material do you suggest to improve the gain of a dipole?