403.5 MHz low profile antenna design and simulation

hi friends!
i am a research scholar , wants to learn the design and simulation of low profile antennas using ADS and Ansoft HFSS tools. presently i am working for 403.5 MHz monopole antenna design ....can u plz help me on this topic, how to proceed means :
substrate selection and thickness?
feed type?
can i proceed with loop antenna design?


Ashish[/b]

Hello,

Before you start with any simulator, first try to understand some of antenna theory and try to figure out what you want.

Some things to consider: required radiation pattern (omnidirectional [for land based communication], directional [point to point connection], hemispherical [satellite], polarization [vertical, horizontal, circular], operating bandwidth and acceptable Return Loss (|S11| or VSWR), Gain, etc.

You may know how to calculate a static magnetic field from a structure carrying a current. For radiation fields there is a similar formula for calculating the E or H- field from a small wire segment carrying AC current.

Knowing the "radiation pattern" from a small wire segments and that superposition is valid for fields, you can guess the radiation pattern for structures like monopoles, half wave resonating patch, small and large loops, etc.

As many antenna constructions behave like transmission line sections, familiarity with transmission line theory is very useful for guessing the current distribution and to know whether your antenna structure has low or high impedance. Many antennas are by nature narrow band devices where the current distribution follows a standing wave envelope pattern.

Ground planes behave many times as a mirrors and can be treated as a second antenna below the ground plane (but mostly fed with opposite current).

Horizontal structures (so ac current runs in horizontal plane) above a ground are not good radiators in the horizontal plane, A PIFA (planar inverted F antenna) has a vertical segment with high current in that vertical section. Therefore PIFA will radiate reasonably in the horizontal plane.

A quarter wave over a ground plane behaves like a quarter wave transmission line without termination with radiation loss.

Good luck exploring the antenna field.

http://www.ittc.ku.edu/research/thes...nni_thesis.pdf