Re: NEC-LIST: Plane wave excitation and far field patterns of large arrays (4nec2x)

At 06:10 PM 9/23/2005, David Phillips wrote:
>We have large dipole arrays that we are trying to get the far-field
>patterns of the reflected energy to calculate RCS. When we use a single
>plane-wave exciation source, we get very large gains (~40dBi).

What lambda? your 40dBi is scaled in square wavelengths. If lambda is,
say, 10 cm, (so your dipoles are 5cm long), then your RCS will be only 100
square meters.

> When we
>convert this to RCS, we get >15000 m2, which is not a reasonable answer.
>Also, when we use either discrete current or discrete plane wave
>excitation sources in the center of each dipole, we get a different, more
>reasonable, answer than when we use a single plane wave source.
>Should these answers be the same, and if so, how should we be
>configuring 4nec? If the answers are not supposed to be the same, which
>answer represents the reflected energy from our array?
>
>Thanks
>David
>
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James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

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