Phased array radars

I have seen phased array aircraft radars that look as if they still
mechanically sweep the dish. I thought the entire reason for phased arrays was
so they wouldn't need to mechanically move. I know how phased arrays work in
principle, but that's as far as I go. What am I missing here?

Dan, U.S. Air Force, retired

(B2431) wrote in message ...
I have seen phased array aircraft radars that look as if they still
mechanically sweep the dish. I thought the entire reason for phased arrays was
so they wouldn't need to mechanically move. I know how phased arrays work in
principle, but that's as far as I go. What am I missing here?

Phased arrays might buy you 60 degrees of beam steering each way. If
you want 360 degree coverage you need multiple arrays like on the
TICOs and BURKEs, or you can rotate one array. In the latter case, a
phased array buys you scanning in elevation to determine target
altitude, and if you're sneaky you can scan side to side independently
of the antenna rotation as an ECCM technique.

-jake

On 21 May 2004 19:14:11 GMT, (B2431) wrote:

I have seen phased array aircraft radars that look as if they still
mechanically sweep the dish. I thought the entire reason for phased arrays was
so they wouldn't need to mechanically move. I know how phased arrays work in
principle, but that's as far as I go. What am I missing here?

The basic reason is that the apparent size (area) of the array goes down by the
cosine of the angle off center. That means resolution and the amount of
reflected energy it can "see" degrades unless you can point the plane of the
array at the object of interest. Uhm, cosine of 45 degrees is .707 (something
from high school about holding your arms like swept wings and thinking Boeing
707 : ) so that isn't too bad but by 60 degrees you have cut the apparent size
in half.

There is also today some rather advanced processing in small packages
(naturally) that used to be on big platforms and sats. The example that comes
to mind is "spotlighting", which uses synthetic aperture type processing and
tracks an object or ground target getting more information with each ping.
Ultimately, image reconstruction methods similar to tomography can be used to
build a picture of the target. In spotlighting the ground you can get a great
picture. If an air target stays on heading there can be a pretty good picture
of that too.

Anyway, for these to work well the plane of the array needs to be normal to the
target. I'm just amazed the darn things work so well, and when will I be able
to get one surplus?

-- Charlie Springer

From: (Regnirps)

snip

Anyway, for these to work well the plane of the array needs to be normal to
the
target. I'm just amazed the darn things work so well, and when will I be able
to get one surplus?

-- Charlie Springer

Civilian colour weather radar sets show up occasionally on e-bay. As a matter
of fact that's what got me to finally break down and ask the question.

Dan, U.S. Air Force, retired

(B2431) wrote in
:

From: (Regnirps)

snip

Anyway, for these to work well the plane of the array needs to be
normal to the
target. I'm just amazed the darn things work so well, and when will I
be able to get one surplus?

-- Charlie Springer

Civilian colour weather radar sets show up occasionally on e-bay. As a
matter of fact that's what got me to finally break down and ask the
question.

Dan, U.S. Air Force, retired

Uh,I don't believe weather radars are phased arrays. It would be
overkill,and an unnecessary expense.

The color part come from computer processing of the radar return

--
Jim Yanik
jyanik-at-kua.net

"Jim Yanik" wrote in message
.. .
(B2431) wrote in
:

Uh,I don't believe weather radars are phased arrays. It would be
overkill,and an unnecessary expense.


http://www.oudaily.com/vnews/display...2?in_archive=1

Keith

"Keith Willshaw" wrote in
:

http://www.oudaily.com/vnews/display...ca4e76e2d2?in_
archive=1


This article says that the phased array radar is NEW in this
application(weather radar),and was just introduced at a first site.

I may have ASSumed that he was referring to weather radar used by TV
stations and metrological stations,not airborne civilian aircraft
instrumentation.

Apologies.


--
Jim Yanik
jyanik-at-kua.net

From: Jim Yanik


(B2431) wrote in
:

From: (Regnirps)

snip

Anyway, for these to work well the plane of the array needs to be
normal to the
target. I'm just amazed the darn things work so well, and when will I
be able to get one surplus?

-- Charlie Springer

Civilian colour weather radar sets show up occasionally on e-bay. As a
matter of fact that's what got me to finally break down and ask the
question.

Dan, U.S. Air Force, retired

Uh,I don't believe weather radars are phased arrays. It would be
overkill,and an unnecessary expense.

The color part come from computer processing of the radar return

--
Jim Yanik
jyanik-at-kua.net

I could be wrong about its function, but there was a phased array system for
civil aircraft on e-bay a week or so ago.

Dan, U.S. Air Force, retired

"B2431" wrote in message
...
I have seen phased array aircraft radars that look as if they still
mechanically sweep the dish. I thought the entire reason for phased
arrays was
so they wouldn't need to mechanically move. I know how phased arrays
work in
principle, but that's as far as I go. What am I missing here?

Dan, U.S. Air Force, retired

Some phased arrays rotate but and are only phase steered in the
vertical for height finding purposes. For instance the antenna on
US AWACS aircraft use this technique, though the Israeli AWACS use
fixed antena inside the dome.

This technique goes back to the 2nd world war. (I think the German
radars Wassermann and Jagdschloss used it as did the radars for the
Soviet missiles SA1 and SA2)

Alternatively and cluster of 4 antena as seen on the USN Aegis system
can be used. There must be great difficulty in integrating the 4
antena to work together.

Having a phased array is pretty important these days. Modern fighter
tactics involve splitting in such a way that the enemy can not track
the multiple targets with a mechanical antenna anymore and using this
as an opportunity to attack.

In article , "The
Enlightenment" wrote:

Some phased arrays rotate but and are only phase steered in the
vertical for height finding purposes. For instance the antenna on
US AWACS aircraft use this technique, though the Israeli AWACS use
fixed antena inside the dome.

This technique goes back to the 2nd world war. (I think the German
radars Wassermann and Jagdschloss used it as did the radars for the
Soviet missiles SA1 and SA2)

Alternatively and cluster of 4 antena as seen on the USN Aegis system
can be used. There must be great difficulty in integrating the 4
antena to work together.

Having a phased array is pretty important these days. Modern fighter
tactics involve splitting in such a way that the enemy can not track
the multiple targets with a mechanical antenna anymore and using this
as an opportunity to attack.

As with most things, there are pro's and con's.
AESAs let you track more targets effectively instantly, when the nose is
pointed in the right direction.
But a mechanically scanned array has a larger off-boresite look angle.
Above statements for fighter aircraft, not surveillance types.

--
Harry Andreas
Engineering raconteur