Help Identifying AESA Antenna Structure Type found in the F-35 aircraft

[ryaamaak]

This is the AN/APG-81 AESA Radar antenna by Northrop Grumman currently found in the F-35 (photo from wikipedia article).

It seems to have a very different structure than past AESA/PESA antennas. For example the APG-68 from the F-16 looks a lot like stacked, slotted wave guides to me.

So what is the name of the actual structural layout for the APG-81? One person I talked to suggested "honeycomb", but I couldn't find any reference to that antenna structure on google scholar. Better search terms would be appreciated. :)

Thanks!

 

[Paul Colby]

I can't see much detail from the picture but I was going to suggest a Vivaldi Slot Array. https://pdfs.semanticscholar.org/9fe2/60de5caeec3cdc36cbb2dbea50e7b5f2fc53.pdf

 

[davenn]

but I was going to suggest a Vivaldi Slot Array.

good thought, except Vivaldi slots are usually tapered, on closer inspection, these slots are a uniform width

...
It seems to have a very different structure than past AESA/PESA antennas. For example the APG-68 from the F-16 looks a lot like stacked, slotted wave guides to me...
Thanks!

Yes, that antenna definitely appears to be sets of slotted waveguides, a big giveaway is the offset of the slots along each guide
that is the norm. for slotted WG's

do you have a link to a larger pic of this antenna ?

youtube video from Northrop Grumman for the radar
other videos on the topic ...



Dave

 

[Paul Colby]

good thought, except Vivaldi slots are usually tapered, on closer inspection, these slots are a uniform width

The elements on the periphery may be parasitic elements. It's unclear to me if the metallization is seen. It may be on the side facing away in the picture. I'm happy for it not to be one though.

 

[ryaamaak]

Thanks everyone for the great input!

do you have a link to a larger pic of this antenna ?

Larger image may be found here. I wasn't able to embed it full size.

 

[davenn]

Thanks everyone for the great input!

Larger image may be found here. I wasn't able to embed it full size.

yeah, I eventually found that in the wiki article when I was looking through those other links I posted

here's a closeup of a section

This antenna is designed for around 10GHz plus/minus ~ 1GHz
I suspect each of those little bars at the top is a 1/4 or 1/2 wave at 10GHz (electrical 1/2 wave = ~ 1.4cm)
A tad difficult to tell the scale in that image
So basically you have masses of say 1/4 wave radiators and the rows of these radiators can be driven by the transmitter
in and out of phase to direct the beam as needed ... as shown in that 2nd or 3rd video I posted

a hint to how these radiators are grouped comes from a bit of that first video shortly in from the startDave

 

[davenn]

On a similar theme

I have a phased array from a terrestrial microwave link antenna that I have had a difficult time to
understand the technology and how the heck it radiates/receives
I may post a pic when I get home fort your interest

Dave

 

[ryaamaak]

Ok I think I'm getting the gist of it. One article mentioned a diameter of approximately 0.7m for the APG-81, so an individual measurement of ~1.4cm seems plausible. Forgive me if this question has a self-evident answer, but would this radiator shape have a specific name or descriptive terms attached to it? (I'm thinking along the lines of how "dipole antenna" shaped elements are frequently used as passive radiators in a yagi-uda antenna.)

For comparison/contrast, the APG-77 from the F22 (below) has a similar structure to the APG-81, but the individual radiators are slightly different: not as tapered at the top, no deep slit between radiators, and confirmed use of GaAs.

Thanks!

 

[davenn]

Ok I think I'm getting the gist of it. One article mentioned a diameter of approximately 0.7m for the APG-81, so an individual measurement of ~1.4cm seems plausible. Forgive me if this question has a self-evident answer, but would this radiator shape have a specific name or descriptive terms attached to it? (I'm thinking along the lines of how "dipole antenna" shaped elements are frequently used as passive radiators in a yagi-uda antenna.)

For comparison/contrast, the APG-77 from the F22 (below) has a similar structure to the APG-81, but the individual radiators are slightly different: not as tapered at the top, no deep slit between radiators, and confirmed use of GaAs.

View attachment 225104

Thanks!

that's a cool variation

For comparison/contrast, the APG-77 from the F22 (below) has a similar structure to the APG-81, but the individual radiators are slightly different: not as tapered at the top, no deep slit between radiators

not as deep as the other one but deeper than initially thought on first look see this ...

they have the same stepped arrangement

I'm a radio tech at heart, this sort of high tech fascinates the hell out of me haha

 

[davenn]

Now @Paul Colby earlier commented on Vivaldi antennas

I can't see much detail from the picture but I was going to suggest a Vivaldi Slot Array. https://pdfs.semanticscholar.org/9fe2/60de5caeec3cdc36cbb2dbea50e7b5f2fc53.pdf

just stumbled on this pic of a real Vivaldi phased array for a radar
Note how the slot changes from wide to narrow aperture ... this gives it wide bandwidth

going further

here's the block diag. of the feeding of the Vivaldi on the left and our other type on the right

Dave