Naval missile guidance thread


nlalyst

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At least there is evidence to sufficiently debunked your view that it cannot possibly happen at the sub array level.
You got the wrong person. I just wanted to know if there is some evidence that AN/APG-81 does digital beamforming.
 

Anlsvrthng

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Do you seriously think that LM would disclose proprietary information on the F-35?

The following is the technical reference that configuration exist at the sub array level with the F-35.


At least there is evidence to sufficiently debunked your view that it cannot possibly happen at the sub array level.
So, it has subarays, and most likely the phase shifters controlled digitally not SDR Tx/Rx modules.

So, it has the same capability like the first German phased array radar in the 2nd WW, apart from not an analogue computer control the phase shifters, but a digital .
 

nlalyst

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The subdivision of MRAs or subarrays in the SPY-6 suggest to me that digital beamforming is in the subarray level.
What would you expect to see then on the backside? This video is closest yet I've seen of the RMA and TRM assembly and its interfacing:

The presenter claims the radar is fully digital.
 
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Anlsvrthng

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What would you expect to see then on the backside? This video is closest yet I've seen of the RMA and TRM assembly and its interfacing:

The presenter claims the radar is fully digital.
Question is how they define the "fully digital " ?

Doesn't matter how you do that there have to be a synchronise signal across all module, and that needs same coaxial , D-sub won't be enough.
 

Anlsvrthng

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This 2nd WW radar has a few interesting features.

Like it had two synchronised Tr/Rx module, so the operator had the capability to make two beam with it , like with the f-35 radar : )

Of course that dramatically reduced the range and jam resistance, so I am sure they never used it.

In the first place the reason of using module was to increase the range : D


So, nearly all features hyped as "advanced" is ....... not advanced at all
 

nlalyst

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Question is how they define the "fully digital " ?

Doesn't matter how you do that there have to be a synchronise signal across all module, and that needs same coaxial , D-sub won't be enough.
Good question.

I did spot one coaxial port (J4) on the lower left of the RMA. More interesting, there are fiber optic cables, one per TRM, going into the RMA both left and right (24 in total). That could be used for synchronization. Take a look at this:
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Why are they showing this much detail to the public?
 
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Anlsvrthng

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I did spot one coaxial port (J4) on the lower left of the RMA. More interesting, there are fiber optic cables, one per TRM, going into the RMA both left and right (24 in total). That could be used for synchronization. Take a look at this:
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Why are they showing this much detail to the public?
I think the synchronous connector is on the backplane of the radar.
The signal has to have fixed length cable, so the backplane is the ideal place for it.
 

Tetrach

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hey radar guys, I have a few basic questions that I would like to ask you. It's mainly about bandwidth.

-So radars, to get better resolution, change frequency during a single pulse. That's called Linear Frequency Modulated waveform. They eventually pass the echoe through a filter to compress the pulse, so they can "better distinguish targets". But how is this possible ? Why do you have to change your frequency ?

-->As far As I can hypothise, when two targets return a pulse from a radar, they will return two different pulses with different frequency, so the echoes won't overlap/ be received as a single unique pulse. Right ?

-How is it even possible to change your frequency on a radar ? Isn't frequency based on the lenght of your antenna ?

-How "much" can a radar changes its frequency in a pulse ? I heard around 1/10 of its based center frequency. It explains why an X band radar has better resolution because the bandwidth (how much it changes its frequency in a pulse) will be in the Ghz. But Why do you have to be in the Ghz to have better resolution ?
 
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