basic understanding bout antenna

friends, i have questions bout antenna, plz give me responses if u now d answer...

my final project is about microstrip bowtie antenna..

1. d thickness of the substrate is vary from 1.5mm, 1.6mm, and 3.2mm. When the substrate is thicker, the gain will also higher, the imaginary part of the impedance will lower, and bandwidth will be broader. can u tell me why?

2. in bowtie antena, there are two triangular antennas seperated by certain gap. at 1st the gap is 0.1mm, and when i raise this gap into 5mm, the antenna gives responses such as:lower gain, lower impedance, and narrower bandwidth. can you tell me why this happens?

thank you very much 4 any responses that u gave me...

1. If you understand how the microstrip antenna work then you also know the answers for your questions. So first try to understand how a microstrip antena radiate. ANd how is the electric field oriented inside and just outside the antenna? What happens with the electric field if you increase the height?

The electric field is normal to the surface inside the dielectric and at the patch ends there is some fringing effect. This fringing is the cause of radiation. If you increase the height, the fringing effect is larger. That is, you have more field lines with different lengths just outside the patch ends. So one can understand that this then gives a larger bandwidth. From this you can maybe now figure it out yourself what happends with the gain of the antenna. To understand what happends with the impedance, think about the antenna as a parallel plate capacitor.

2. The gap behave like a capacitor. Thus the size of the gap affect the impedance which in turn affect bandwidth and gain.

hi you can find your answer in MICROSTRIP ANTENNA by"BAHL".

refer microstrip antenna design handbook

do u have that book...please send me on my email id- pkgupta.nitdgp@gmail.com