Behind the times...
 

Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

Behind the times...
 

"Ed" == Ed Cregger writes:

Ed Perhaps someone can answer a question or two about synthetic
Ed aperture radar systems. I'm interested in whether or not the
Ed flat plate we see as the receiver antenna actually radiates

yes it does. Some old design had slotted waveguides and a common
transmitter, more modern units have separate transmitters for each
dipole, or for a row of dipoles.

Ed power, or is a separate transmitter antenna used? TIA

no, a separate antenna is not necessary, not at least for "normal" air
traffic control/air surveillance radars. Those huge OTH monsters are a
different beast of course... The separate thing you see on most radars
is the IFF antenna, recognizable because it is turned a few degrees
ahead of the main beam.


Pf, ik5pvx



--
Pierfrancesco Caci

Behind the times...
 

Ed Cregger wrote:
Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K


You mean on something like this?

http://www.raytheon.com/capabilities..._tpq37_pdf.pdf

It would depend on the design, but in general, yes, the flat plate does
both.


--
Jim Pennino

Remove .spam.sux to reply.

Behind the times...
 

On Oct 31, 1:27 pm, "Ed Cregger" wrote:
Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

Synthetic Aperture Radar (SAR) isn't usually the rotating antenna
thing. SAR would be on some sort of moving platform (a plane or
satellite, for instance, although SARs have been done on cars and
boats and balloons)

Perhaps what you're thinking about is a phased array antenna? The flat
plate thing is the antenna, and might be either totally passive (and
can work for both transmit and receive) or active, with lots of T/R
modules.

Behind the times...
 

On Fri, 31 Oct 2008 16:27:47 -0400, "Ed Cregger"
wrote:

Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

As others have mentioned, that's not synthetic aperture radar. See
the article at:
http://en.wikipedia.org/wiki/Synthetic_aperture_radar
for explanations and references. Note that either the target or the
radar has to be moving for SAR to work. A mess of small transmitters,
scattered over a wide area, will also work. A rotating radar antenna
(phased array, bedspring, or dish) will not work.

One example is the SRTM (Shuttle Radar Topography Mission), which used
interferometry and a synthetic aperture radar to map the planet. In
this case, the shuttle was moving and the ground was relatively
motionless.
http://fas.org/irp/program/collect/ifsar.htm
http://www2.jpl.nasa.gov/srtm/
Since there was only one space shuttle in orbit, the antenna must both
xmit and receive.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

Behind the times...
 

wrote in message
...
On Oct 31, 1:27 pm, "Ed Cregger" wrote:
Perhaps someone can answer a question or two about synthetic aperture
radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

Synthetic Aperture Radar (SAR) isn't usually the rotating antenna
thing. SAR would be on some sort of moving platform (a plane or
satellite, for instance, although SARs have been done on cars and
boats and balloons)

Perhaps what you're thinking about is a phased array antenna? The flat
plate thing is the antenna, and might be either totally passive (and
can work for both transmit and receive) or active, with lots of T/R
modules.


------------

I was thinking of the Aegis class warships.

Ed Cregger

Behind the times...
 

"Jeff Liebermann" wrote in message
...
On Fri, 31 Oct 2008 16:27:47 -0400, "Ed Cregger"
wrote:

Perhaps someone can answer a question or two about synthetic aperture
radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

As others have mentioned, that's not synthetic aperture radar. See
the article at:
http://en.wikipedia.org/wiki/Synthetic_aperture_radar
for explanations and references. Note that either the target or the
radar has to be moving for SAR to work. A mess of small transmitters,
scattered over a wide area, will also work. A rotating radar antenna
(phased array, bedspring, or dish) will not work.

One example is the SRTM (Shuttle Radar Topography Mission), which used
interferometry and a synthetic aperture radar to map the planet. In
this case, the shuttle was moving and the ground was relatively
motionless.
http://fas.org/irp/program/collect/ifsar.htm
http://www2.jpl.nasa.gov/srtm/
Since there was only one space shuttle in orbit, the antenna must both
xmit and receive.

-----------

Thanks for the explanations, all. Much appreciated.

Ed, NM2K

Behind the times...
 

In article ,
Ed Cregger wrote:

I was thinking of the Aegis class warships.

I believe that the Aegis warship radar is a phased-array system, akin
to the PAVE PAWS radars that have been in the ham press lately due to
QRM issues on both the east and west coasts of the US (some ham 440
repeater systems have been required to mitigate interference to PAVE
PAWS and some have gone off the air as a result).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Behind the times...
 

On Sat, 1 Nov 2008 11:11:32 -0400, "Ed Cregger"
wrote:

systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

I was thinking of the Aegis class warships.

Hi Ed,

The "flat plate" is acually a mosaic of 4100 phased elements driven by
a single RF source.

73's
Richard Clark, KB7QHC

Behind the times...
 

On Sat, 1 Nov 2008 11:11:32 -0400, "Ed Cregger"
wrote:

I was thinking of the Aegis class warships.

See: AN/SPY-1. 4 panels with 4 megawatts in S-band.
http://en.wikipedia.org/wiki/AN/SPY-1
http://www.globalsecurity.org/military/systems/ship/systems/an-spy-1.htm
https://wrc.navair-rdte.navy.mil/warfighter_enc/weapons/SensElec/RADAR/anspy1.htm

Lots of fun when the beam hits an adjacent vessels antenna farm and
toasts everything connected to it.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Behind the times...
 

"Jeff Liebermann" wrote in message
...
On Sat, 1 Nov 2008 11:11:32 -0400, "Ed Cregger"
wrote:

I was thinking of the Aegis class warships.

See: AN/SPY-1. 4 panels with 4 megawatts in S-band.
http://en.wikipedia.org/wiki/AN/SPY-1
http://www.globalsecurity.org/military/systems/ship/systems/an-spy-1.htm

https://wrc.navair-rdte.navy.mil/war...lec/RADAR/ansp
y1.htm

Lots of fun when the beam hits an adjacent vessels antenna farm and
toasts everything connected to it.


It happens but it's not supposed to. A standard rule is that an Aegis ship
needs to "sector out" other vessels in company when they are within a
specified distance -- I forget the number. Among the more vulnerable
equipments are the EW receivers.

The AN/SPY-1 sends a pseudo-random pulse train. When you hear one on a
suitable receiver, it sounds like corn popping. No joke.

"Sal"

Behind the times...
 

Jeff Liebermann wrote:
On Fri, 31 Oct 2008 16:27:47 -0400, "Ed Cregger"
wrote:

Perhaps someone can answer a question or two about synthetic aperture radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K

As others have mentioned, that's not synthetic aperture radar. See
the article at:
http://en.wikipedia.org/wiki/Synthetic_aperture_radar
for explanations and references. Note that either the target or the
radar has to be moving for SAR to work. A mess of small transmitters,
scattered over a wide area, will also work. A rotating radar antenna
(phased array, bedspring, or dish) will not work.

One example is the SRTM (Shuttle Radar Topography Mission), which used
interferometry and a synthetic aperture radar to map the planet. In
this case, the shuttle was moving and the ground was relatively
motionless.
http://fas.org/irp/program/collect/ifsar.htm
http://www2.jpl.nasa.gov/srtm/
Since there was only one space shuttle in orbit, the antenna must both
xmit and receive.


Not precisely true in the case of InSAR.. One transmitter, two
receivers. A Tx and Rx can share, but the second receiver needs its own
antenna. (Modern phased arrays can segment a long array into two receive
arrays to do InSAR, as well).

Behind the times...
 

Ed Cregger wrote:
wrote in message
...
On Oct 31, 1:27 pm, "Ed Cregger" wrote:
Perhaps someone can answer a question or two about synthetic aperture
radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K
Synthetic Aperture Radar (SAR) isn't usually the rotating antenna
thing. SAR would be on some sort of moving platform (a plane or
satellite, for instance, although SARs have been done on cars and
boats and balloons)

Perhaps what you're thinking about is a phased array antenna? The flat
plate thing is the antenna, and might be either totally passive (and
can work for both transmit and receive) or active, with lots of T/R
modules.


------------

I was thinking of the Aegis class warships.

the SPY-1 isn't a SAR (well.. it might be able to do ISAR if the target
is moving or rotating) but it does use the same aperture for Tx and Rx.
(Racks and Racks of L band T/R modules)

Behind the times...
 

Sal M. Onella wrote:
"Jeff Liebermann" wrote in message
...
On Sat, 1 Nov 2008 11:11:32 -0400, "Ed Cregger"
wrote:

I was thinking of the Aegis class warships.
See: AN/SPY-1. 4 panels with 4 megawatts in S-band.
http://en.wikipedia.org/wiki/AN/SPY-1
http://www.globalsecurity.org/military/systems/ship/systems/an-spy-1.htm

https://wrc.navair-rdte.navy.mil/war...lec/RADAR/ansp
y1.htm
Lots of fun when the beam hits an adjacent vessels antenna farm and
toasts everything connected to it.


It happens but it's not supposed to. A standard rule is that an Aegis ship
needs to "sector out" other vessels in company when they are within a
specified distance -- I forget the number. Among the more vulnerable
equipments are the EW receivers.

The AN/SPY-1 sends a pseudo-random pulse train. When you hear one on a
suitable receiver, it sounds like corn popping. No joke.


Almost all modern radars send some sort of PN coded pulse (e.g. a Barker
code) to be used in pulse compression so the peak/average power ratio is
limited. A few radars use linear FM chirps.

Behind the times...
 

"Jim Lux" wrote in message
...
Ed Cregger wrote:
wrote in message
...
On Oct 31, 1:27 pm, "Ed Cregger" wrote:
Perhaps someone can answer a question or two about synthetic aperture
radar
systems. I'm interested in whether or not the flat plate we see as the
receiver antenna actually radiates power, or is a separate transmitter
antenna used? TIA

Ed, NM2K
Synthetic Aperture Radar (SAR) isn't usually the rotating antenna
thing. SAR would be on some sort of moving platform (a plane or
satellite, for instance, although SARs have been done on cars and
boats and balloons)

Perhaps what you're thinking about is a phased array antenna? The flat
plate thing is the antenna, and might be either totally passive (and
can work for both transmit and receive) or active, with lots of T/R
modules.


------------

I was thinking of the Aegis class warships.

the SPY-1 isn't a SAR (well.. it might be able to do ISAR if the target
is moving or rotating) but it does use the same aperture for Tx and Rx.
(Racks and Racks of L band T/R modules)

-----------

Well, I said I was behind the times. G

Thanks to everyone for their help on getting me up to date. At least I have
somewhere to begin studying now.

Ed, NM2K