How can I improve the range of my antenna?

How can I improve the range of the antenna, which is operated at ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10cm? This circuit is for detecting gigahertz signals that are used for a mobile bug.
Here the circuit uses a 0.22µF disk capacitor (C3) to capture the RF signals from the mobile phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone

If you are using the lead of a capacitor as your antenna I am not surprised that you would like to increase the range. I would consider making a small dipole or patch antenna. Are there any size constraints for the antenna?

If you know where the other unit is, then a directional antenna will also help. Probably the easiest way to do that is to add a reflector. At 300mm wavelength something roughly parabolic covered with aluminum foil will work. I've seen even just a coffee can with one end open increase range significantly, although at somewhat shorter wavelengths.

thank you sir
for your valuable information
i am b-tech student i have the interest to do something new but i have no more ideas
so i gust do the small projects which comes on
electronics for you max-zine
so,please suggest me what can i do to improve my skills i this area

finally
i fell that u r the my first guide please help me

I learned most everything I know related to antennas in building and characterizing them. If you have a access to a spectrum analyzer look up antenna designs and start building them. The web is a great resource.

Your input capacitors are very large in relation to the frequencies you are detecting. In fact, they are probably inductive in your frequency range. So your loop antenna arrangement is probably not resonating where you expect. I suggest much smaller values, and making them NPO / COG dielectric.

I'd just go with a length of wire directly into your amp - the closer you can cut the wire to 1/4 wavelength - adjusted for the propagation of light in the wire - as you can.

what is the actual meaning of disk capacitor... & why it should be 18 mm with a spacing of 8 mm between the leads ..sir pls clear my doubt

Install aTV Antenna Booster. A digitalantenna booster can be installed to extend the range of yourTV antenna.Adjust the Location and Direction of theAntenna. The position of yourantenna makes a big difference.Avoid Wireless Gear. Wireless gear is all around us.Add More Coaxial Cable.

Usually the simplest way to improve reception is with a pre-amplifier. So, buy one mybkexperience