NEC-LIST: Adaptive Antennas and Mutual Coupling

Good-day Folks and fellow NEC-listers:

As University of Kansas we are working on the development of an
adaptive antenna for wireless comm. The antenna has been designed,
meaning given some nominal specs. we can design the geometry. Now once
the antenna has been designed, we will do some signal processing with
it, and there is this problem which is a source of worry. Please let
me explain the situation.

The basic array problem is to determine the weights for either
adaptive or non-adaptive (meaning regular) array. To do that one needs
the element patterns of the individual radiators.

Now the element patterns can be computed with or without the effects
of mutual coupling considered. In the latter case, it is the
`active-element' pattern. Computation of active element pattern is
substantially difficult than the free-space pattern of the elements.
Thus, it appears that computation of the active element pattern should
be avoided if possible. But, when an array is radiating there *WILL
BE* some degree of mutual coupling no matter what.

An alternative is to measure the active element pattern. That is,
terminate all other elements in matched loads and measure the pattern
of the excited element when it is transmitting. The objective then is
to store these patterns on a computer and download them for use in
determining the excitation weights. The problem is that one can
measure the power pattern, i.e., 20.0*Log | E | in dB. But, how about
the phase ?

The alternate proposal looks quite OK, except I am not sure as to how
practical such would be in real life ? That means we are now
interested in determining the trade-offs between computation vs.
measurement.

Could you folks out there please provide me with some input as to
what is the best route ?

Please help !!!

- regards,
=================================================================
Deb Chatterjee

Radar Systems and Remote Sensing Laboratory
Department of Electrical Engineering and Computer Science
Room 322, Nichols Hall
2291 Irving Hill Road
Lawrence, KS 66045-2969

tel: (913)864-7742
fax: (913)864-7789
e-mail: dchatterjee_at_kuhub.cc.ukans.edu
Received on Wed Nov 05 1997 - 14:46:17 EST