First I want to thank you a bout your work
I wish to know if there are any problem to put all the coponents inside the antenna area ?
Does the performance of the antenna be affected ?
It should be possible to place the components inside the antenna as long as there is a decent 'buffer area' between the antenna and the components. I placed them outside since I wasn't sure at first how this would effect performance and I wanted the best possible range, but also because of the 0.1" header pins. If the headers were in the middle you would have to attach cables to them in the middle of the antenna which will be a physical obstacle that might limit how close you can get with small tags, etc..
I've been discussing the idea of a small stand-alone battery-powered board with an MCU like the LPC1343, and would probably place all of the components in the middle of the antenna in this situation, though I don't like the idea of having to run signals or traces underneath the antenna to break out the USB connector, etc. I may still end up placing all of the components beside the antenna, but using a much smaller surface area than the current breakout board. It will take some trial and error to see what works well.