Naval missile guidance thread - SAM systems

[Max Demian]

Lets go back to this again, in particular if the communication strip on the Type 346 is a C-band, which therefore, the HQ-9 communicates with the array via C-band.

By the time you get to the Type 346A, the array is now perfectly symmetrical, and there is no strip on the bottom. This means either two things:

Wait, now I am confused. Did we not establish that this is a photo of Type 346A on Type 052D?

What we are missing is a photo of the array on 052C.

I would look for answers by studying HQ-9, but the information there is equally scarce.

One issue with the communication taking place via the narrow strips is if the pings back are used for missile tracking, then the resolution in elevation would be poor.

If it is true that HHQ-9 had ARH from the start, then the same critique @Anlsvrthng had about "cheap" radars and expensive missiles could be applied to 052C/D?

 

[Max Demian]

I was editing my post, and ran out of time.

Couple of downsides to the theory that the narrow strips are used for HHQ-9 guidance:
1. Since a smaller portion of the array is used, the downlink from the missile will have a weaker SNR compared to the entire array being used.

2. The pings back could not be used for missile tracking due to poor resolution in elevation.

 

[Max Demian]

PESA with Yttrium shifters like SPY-1 have a dead time. During this period, antenna cannot receive or transmit. Dead time is when the shifters are reset to prepare for the next transmission. After transmit, a large part of the time between transmit and receive are placed into dead time.

SPY-1 needs to track the missile in AEGIS mode. It could modulate the control message in the same ping, no?

The Wikipedia article on SPY-1 indicates a larger number of receivers than transmitters. What do you make of that?

 

[Tam]

Wait, now I am confused. Did we not establish that this is a photo of Type 346A on Type 052D?
View attachment 57668
What we are missing is a photo of the array on 052C.

I would look for answers by studying HQ-9, but the information there is equally scarce.

One issue with the communication taking place via the narrow strips is if the pings back are used for missile tracking, then the resolution in elevation would be poor.

If it is true that HHQ-9 had ARH from the start, then the same critique @Anlsvrthng had about "cheap" radars and expensive missiles could be applied to 052C/D?

It lacks the IFF bar on top of the array. It has to be a 052C. Not to mention this photo also predated the 052D. I was wrong thinking this might be 052D.

Not pings and not radar reflections, you're still thinking of radar terms. This is more between two devices now talking to each other. Your update is a message telling the missile to go to these coordinates, and the missile responds back telling you its acknowledged the orders and tell you where I am with its own telemetry, with TVM telling you in addition, here is what I am seeing. At the very least the missile should acknowledge receipt of information. The radar and combat computer is giving instructions for the missile that is like a set of way points the missile has to follow, terminating in a point where the seeker would go live and there would be no more communication then.

 

[Max Demian]

Not pings and not radar reflections, you're still thinking of radar terms. This is more between two devices now talking to each other. Your update is a message telling the missile to go to these coordinates, and the missile responds back telling you its acknowledged the orders and tell you where I am with its own telemetry, with TVM telling you in addition, here is what I am seeing. At the very least the missile should acknowledge receipt of information. The radar and combat computer is giving instructions for the missile that is like a set of way points the missile has to follow, terminating in a point where the seeker would go live and there would be no more communication then.

I should've written downlink ping, sent from the missile.

What you just described is how the 2T mode works for SM-2, minus TVM. In AEGIS mode SM-2 is command guided, ie the flight control actuations are computed by the ship FCR and sent to the missile. To accomplish this, SPY-1 needs to actively track the missile. This results in a better intercept point and reduced on target time for SPG-62, but higher load on SPY-1.

 

[Tam]

SPY-1 needs to track the missile in AEGIS mode. It could modulate the control message in the same ping, no?

The Wikipedia article on SPY-1 indicates a larger number of receivers than transmitters. What do you make of that?

Some part of the array would have to send the update while "pinging" the missile and the target.

The receiver part on SPY-1 appears to be built partially more like an AESA, where the data is collected and processed downstream in the subarray, instead of a central unit for the entire array. Maybe the real question to that is where in the array the elements that are receive only and don't have transmitters. My guess is that its more on the edges, than on the center. The beam width of the SPY-1 is 1.7 instead of 1.3, so the larger beam width suggests the effective aparture is smaller than the array's physical size. As it turns out if a phase array has equal high power from edge to center, it creates a very narrow beam but also creates plenty of sidelobes. Due to the sidelobes, the narrow beam ends up having weak gain, and the sidelobes reflect on the environment giving you back echoes from the ground and other things, and it can be picked up by other sources that will reveal the location and waveform of the radar. But if the power is stronger on the center of the array, and weaker towards the edges, the center beam gets a wider beamwidth but stronger gain, and the sidelobes are reduced to a minimum. If you want to reduce the transmission power off the edges of the array, you might as well remove a few emitters. With this I am thinking the elements used for missile communication should be on the edges as well. Anyway, these are just my theories and guesswork on the matter.

 

[Anlsvrthng]

PESA with Yttrium shifters like SPY-1 have a dead time. During this period, antenna cannot receive or transmit. Dead time is when the shifters are reset to prepare for the next transmission. After transmit, a large part of the time between transmit and receive are placed into dead time. So the window of receive time during the pulse interval is small.

SPY-1B has a cycle time of 6.4, 12.7, 25 and 51 microseconds. If you transmit 10 microsecond packet within the receive time of the pulse interval, you are sending out when the echo is coming in. This results in interference in both the transmitted message and on the incoming echo. You would have to split aperture during receive, where for example, 90% of the elements are set in receive, and 10% of the elements or the number of elements equal to one subarray, would be transmitting the datalink signal.

It can skip say every 50 scan, and use the frame to communicate with missiles.

Or whatever, it is easy to assemble the timing for time shared search/tracking and communication.

And the main: the communication requiring the smallest amount of resources, it require way less power to transmit than normal radar pulse, and due to the high aperture the missile needs to burst data in continuously updated short highly compressed burst , and the radar can take care of them.
It is fully computer controlled, not analogue circuit, so it doesn't have to follow a pre-defined pattern.

If part of the array used as a small phased array antenna then the search /tracking area of radar proportionally decreased.

So, 10% lost aperture for other jobs will decrease the search area by 10%.

It is only a marketing ploy, the warfare importance of it is similar like a built in MP3 player function in the operator terminal.

The receiver part on SPY-1 appears to be built partially more like an AESA, where the data is collected and processed downstream in the subarray, instead of a central unit for the entire array.

The Intel failed to deliver the 8GHz P4 CPUs by 2008, and the 50GHz ones by 2015, so the only use of the (AESA like ) one CPU / antenna is the decreased signal loss.

 

[Max Demian]

A.) The HHQ-9 is now communicating with the Type 346A array directly, using the S-band. This means the new batch of HHQ-9 for the 052D destroyer uses an S-band datalink, or a dual S and C-band datalink, with the C-band for use with the 052C destroyers.

Assuming that the first versions of HQ-9 used C-band for midcourse guidance, the move to S-band may be a consequence of increased missile range or system simplification that allows them a larger S-band aperture for the radar at a cost of having to perform an additional function. I suspect it is the latter.

For reference, the early 2000s HQ-9s were credited with a 90km range. HQ-9B is reported to have a slant range of 200km, possibly more.

 

[Max Demian]

It can skip say every 50 scan, and use the frame to communicate with missiles.

Or whatever, it is easy to assemble the timing for time shared search/tracking and communication.

Is it possible to encode the control message in the pulses used to track the missile? Thereby, no extra work would need to be performed on the send side. Just a bit extra time to wait for the reply message from the missile.

 

[Anlsvrthng]

Is it possible to encode the control message in the pulses used to track the missile? Thereby, no extra work would need to be performed on the send side. Just a bit extra time to wait for the reply message from the missile.

I've had a "now I understand" moment . : )

Thanks for the discussion.

Ok, so the main thing is the phase shifter , that makes the things funny.

The phased array defined by the phase shift ,that in normal case works like you put an antenna onto your wall, and cut the cables from the transmitter to set the "transmitting angle" with the differently cut cable length.

So, it means the visible, and the electromagnetic direction of the antenna is different.
Now, the antenna business is about that to receive / transmit electromagnetic wave around the resonant frequency of the antenna. so the phased array will have a +/- MHz frequency that it collect - wider frequency bandwidth means wider main lobe.

Now, to emit with a PESA the same beam to multiple direction, like subarrays needs only different settings on the phase sifters - so if it has to command 20 missile it can generate 20 small aperture, and transmit a short, 40 kbyte pulse to all of them, and each individual missile decode its own part of it.


The most interesting part is the RECEIVING, if the radar has a dedicated Rx element for each dipole (like the irbis) then it can generate multiple electromagnetic phased array direction with the same radar.

All that it takes is to generate time shifted data streams after the amplification.

So, the radar most likely can receive the radar echo AND receive data from multiple source.


The Tx part can have higher data rate for multi missile command mode, but the missile command needs only negligible data anyway.