The AIM-120 'AMRAAM' - History, Design, Performance & Discussion

Yes, it is. The command link is the receiver on the rear of the missile that allows it to receive updated inertial coordinates for target so that it can adjust it’s trajectory to better meet it. This is necessary until the missile is in the autonomous region (the point where it can provide it’s own updates and guide itself).

This is why the initial portion of the flight is called “command-inertial” phase.

That is a fundamental part of AMRAAM:

  1. You provide AMRAAM with the target information (speed, heading, distance, etc.)
  2. You fire the AMRAAM
  3. AMRAAM uses inertial navigation to fly towards the predicted intercept point
  4. As the target maneuvers you send AMRAAM command guidance signals which tell it the new speed / range / heading of the target.
  5. AMRAAM uses the command link information to update it’s predicted intercept point
  6. Repeat steps 3 - 5 a bunch of times
  7. Once it is a certain (classified) distance from the target AMRAAM activates its MPRF active radar seeker and starts searching for the target
  8. AMRAAM finds and locks onto the target
  9. AMRAAM now knows exactly where the target is and guides towards it
  10. BOOM (hopefully)
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You want to say I’m keeping you here but decide to tack that on after making up a bunch of ridiculous claims you know I’ll feel the need or obligation to defend myself from.

Please refrain from taking part in the thread going forward unless you are quoting directly from a proper source when discussing the topics of pulse repetition frequency, continuous wave emitters, or the AMRAAM’s guidance. Thanks.

The full sources I’ve been using have been sourced at the bottom of the OP. I’ve been directly quoting them and the verbiage is quite clear. The smaller paragraphs screen grabbed were for ease of reading. I’m not hiding anything.

Things are getting too heated in here. Please remain civil.

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The incorrect flight performance of Red Top was reported over 3 years ago though, it’s not like they haven’t had time.

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Finally got the chance follow up with you on this subject. I do make effort to follow up with the Indvidual’s who are actually looking to determine the truth of the matter by comparing research with an unbiased interpretation.

7alrc4xk

Yes, that is established thanks to you.
However, in almost every circumstance I can find (unless at WVR and of course, HPRF from start) Med PRF is initiated first to maximize search range and to acquire selected targets that may be found at the maximum distances within the Aim-120s active radar range. Though CW and ICW (HPRF) is the best for fire control radar precision & active homing precision to guide missile to proxy/impact. it is limited to range especially on these very small, weak signals producing active radar transmitters.

That is why Fighters of the fourth generation are starting to arrive High PRF mode focused like the Tomcat. The difference between them is that the AWG-9 is a CW radar which offers a wider array of very Low PRFS and ultra-high PRFs at further distances critical for precision accuracy far beyond visual range. Newer fighters coming like the F-16C, F-15 & F-18 etc. are High PRF, but seem to be only ICW with no CW capability. Reason seems obvious. No need and they are not true BVR platforms. ICW capable is continuous wave transmissions, still having pulses at such a high frequency that it will not disrupt guidance of the sparrow as previous generation. Now able to pulse, the radar has opportunity in which data can be processed and even allowing new capability that were not possible with CW. However, you need very powerful digital signal processors to translate that data in a combat scenario.
It is very hard to transmit continuous wave large distances without any disruption whatsoever. Need a very powerful radar like the AWG9. Additionally, That is also why the Aim7M has a digital computer (with software in EEPROM modules reprogrammable on the ground), an autopilot, and an active fuze. The autopilot enables the AIM-7M to fly optimized trajectories, with target illumination necessary only for mid-course and terminal guidance.

GJ refuses to give the ANY course guidance whatsoever to the Aim7M when they have clearly done it for the fake overperforming R27. The missile just blows up the second illumination cuts out lol.

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This has nothing to do with quality of radar targeting.

Adding Med PRF capability in the terminal phase was required for the Aim-120 for a couple reasons.
One was an effort to maximize search ranges (its medium range missile) and make up for its weaker signal. It does not have the broadcast power & range to utilize High PRF alone like Aim-54 or AWG9 that supports it. The Aim-120 needs Med PRF to extend its range. Aim-120 must switch to a Med PRF at time of reaching terminal simply to search for a target to acquire at range.

Most importantly Med PRF is critical in the several modes that come standard with the aim-120 along with several variants of those modes depending on the platform using it. The AMRAAM is designed to be a totally versatile, highly programmable missile.
For example, if the AMRAAM is operating in a clustered target assignment. Yes, it much more common operating in modes such as this, that the Aim-120 will use MED PRF first and look for targets before it switches to High PRF to target them.

What? High PRF is not the best at targeting for Active missiles and fire control radars like the F14?? The Aim-120 merely uses both PRFs in the terminal which is uncommon amongst Active homing missiles.
Screenshot 2023-09-14 221518

You guys keep reading what the AMRAAM does for the Tornado and keep applying it to the missile as a whole. That is a mistake in regard to this unique missile.

Just because the British say the missile operates the way it does for them. Does not mean the missile is programmed the same as all other fighters.

yerey4

I have more relevant data. Just have to find it. But the AMRAAM on some British Tornado will be programmed differently from other fighters. The missile is HYPER DEPENDENT on the firing aircrafts radar and data link. Even the US navy developed program to tackle and develop a AMRAAM/F18 link to maximize it use.

It absolutely is. It is a MEDIUM ranged missile. The aircraft tells the missile what to do and how to do it.

Its an amazing missile. reprogrammable to fit the firing aircrafts limitations. However, I can see why some do not regard it as true “active homing.”

There is no way in hell, GJ is going to model such a highly versatile Western missile along with any of its standard modes in WT. It is probably just going to be an Aim7M with actual midcourse at best.

Make sure you cite your sources so no one flags random clips of what you posted. You have to prove it’s available for public distribution. In this case, I know the document you’re citing.

You’ve said this, but your post suggests you’re still desperately hanging onto the interpretation of what “HPRF” is from last week. This is in spite of clearly just initially reading the Wikipedia page and then later delving into more thorough sources and twisting what they said to try and fit your initial understanding better. All in a vain attempt to dig yourself out of the hole instead of admitting you were wrong in the first place. More on this to follow…

This source is from DTIC

It mentions the use of both high and medium PRF and nothing more. Nothing else in the document makes inference to it, and your deduction afterwards is based on nothing more than your internal opinion and need / want to prove yourself right in face of all the other points made thus far.

This is the first unsubstantiated thing that I can see from your reply…
Can you show from any source that MPRF is used first or that MPRF active range is initiated first (further away) than HPRF active range?

It was my understanding that HPRF offered the AMRAAM an early ability to track targets as long as they were traveling fast enough and with good closure rate to track in HPRF. It’s possible it also does HPRF interleaved of some sort for better track data.

We already went over this. In fact, @MaMoran20 covered it quite well…

And since we don’t know the specifics about the AMRAAM’s performance to ascertain which scenarios it might use HPRF as opposed to MPRF, we can’t really make such “uneducated” guesses as to which is more useful for what. The fact it uses both suggests to me that maybe HPRF and MPRF are used for the aforementioned scenarios and if I understand this as well as I think I do… just offers a higher pK against a larger variety of targets both unaware or defensive by having various radar modes… including home on jam.

CW is not a PRF it is a continuous wave. ICW is sometimes used to refer to HPRF, other times it could be considered a MPRF as MaMoran said. I understand you are just saying that the F-16C, F-15, and F/A-18 use HPRF (ICW) solely with no dedicated continuous wave illumination device which should be explicitly stated rather than implied to avoid confusion going forward.

What capabilities were previously not possible with a continuous wave illumination device?

The AIM-7 series requires a STT before launch, but acquires the signal after launch. The missile requires this continuous guidance for the duration of flight all the way until it hits the target.

The R-27R/ER is not overperforming, in fact it is underperforming at higher altitudes because Gaijin has not optimized the trajectories for high altitude but instead they focused on matching the range and time to target charts for ~5km altitude. As a result the missile is missing nearly 10-15% of it’s range at altitudes of 10km+. The R-27R/ER explicitly has a datalink antenna and gets mid-course from the Russian radars, the AIM-7 series does not receive this until the AIM-7P Block 2. You’re just misunderstanding the technical terms stated here.

The only thing they need to do for AIM-7M is improve the time to hit gains and potentially give it a modest loft trajectory / improved guidance duration. This was something not explicitly stated and thus you have to look at a couple of sources and put two and two together. I did so, and compiled a report. Previously, the AIM-7M was believed to just be a AIM-7F that had moved to solid state electronics and a monopulse guidance seeker.

Correct, it’s just a quick description of the brevity code that does not indicate whether Husky or Pitbull comes first or second. In fact, it adds to my argument that the HPRF mode may just be a way of extending the terminal homing range of the missile against high and fast targets.

Can you explain further how MPRF extends the search range of the missiles onboard active radar? Seems to me, every other radar with HPRF and MPRF modes has worse range in MPRF but better tracking against targets from beam aspect.

Do you have a source for this presumption?

What are those modes? Are you trying to say that you know something we don’t already? If so, is it available for public distribution (and discussion?)… if not, why make such wild presumptions? What are you basing this information on?

Yes, because the missile guides the same way with the same modes on both British and US aircraft. No unusual modifications to the guidance system have ever been stated between export and domestic AIM-120B through AIM-120C-5 missiles.

Except the AIM-120 was designed to essentially be NATO’s BVR missile from the get-go. You say that the AMRAAM on “some British Tornado” will be programmed differently from other fighters, but this is not substantiated by any of the sources you’ve shared thus far. All it states is that the missile relies heavily on the mid-course updates from the host aircraft for accurate target information. This is called “painting a track”. Using flashy words like “hyper dependent” when they weren’t used in the source doesn’t make what you say any more credible.

This is the full block quote from Flame2512 that you just pulled from context.

Medium range means absolutely nothing in this context. We literally have primary sources showing you exactly what he is stating is true and you’re trying to play mental gymnastics with the sources wording. All the Tornado FCS is doing is calculating when the pilot will be able to turn away (when the missile will go active).

Reprogrammable almost solely to improve ECCM or performance against specific types of targets and to allow for re-upload and re-flashing of software for the purpose of maintenance and testing.

I’ve never seen the reprogrammable memory stated as being used to “fit the firing aircrafts limitations”.

No, they’ll likely just model it to track in MPRF and give it a small notch sector. This would be the most accurate way of bringing it to the game. The AIM-7M already does get mid-course, it’s actively tracking the launch aircraft radar emission reflections from target. The AIM-120 gets command-inertial mid-course updates instead of active STT SARH guidance.

In conclusion, no. You did not do this in an unbiased manner at all. Instead, you incorrectly cited a couple of sources and then stated a bunch of your own unfounded opinions on the missile as if the sources helped to prove your point when they had nothing in relation.

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Hey genius the AMRAAM goes High PRF under conditions. What are those conditions right now.
You don’t have a clue!

Still has not an idea how pulse repetitions work with radar receivers!

Are you seriously asking me why lower pulse repetitions are better for target detection at range?

You are not worth responding to. Go away.

I do have a clue, the clues are in all of the sources we’ve thus discussed. They all indicate that HPRF would be used against optimal targets (unaware, head-on conditions generally are favorable for this). It extends the range at which the missile can go active. Once the missile is within this range, and mid-course updates stop… it can choose to go active and will guide itself.

Once within the closer MPRF active (Pitbull) range, the missile simply goes active on it’s own regardless.

Can you explain again, this time without copy pasting the Wikipedia article on HPRF?

No, that’s not what I asked. You literally quoted my question in full. Let me rephrase;
How does MPRF extend the search range of a radar over HPRF?

lol, so instead of a good debate, you’re gonna result to insults and ignoring all of the very good and valid points made in my post.

Also, this is my thread… you’re gonna get my opinion here.

You don’t have a source that states. I can go back and reference all the prior sources shared so far and all of the stuff that MaMoran has said. It is corroborated with any well founded study on how HPRF / MPRF’s work. You’ve been wrong about this stuff the entire time this discussion has been going on. Any time you were shown to be wrong you just ignored it and carried on with something else.

What’s with the weird commentary? Is it possible for you to partake in this discussion without the out-of-pocket comments?

No, you misquoted what I said and once again are refusing to answer the question. This is because it shows you how wrong you are right now.

It was more or less rhetorical and the answer to my original question was “it doesn’t.” This was evident to you at least since MaMoran shared and explained what MPRF is useful for previously. I even quoted his entire explanation in my post for you.

When was I not?
Why?

Well, seeing as you can’t directly copy paste a block of text from youtube (and still fail to understand what was said)… I guess it’s not.

I’m not certain what you mean by “rats”? It has nothing to do with whether people agree with me or not, I frankly don’t care. The best part of this conversation is the fact that the devs fully understand how the radars and missiles work and they’ll model it correctly regardless of how hard you try to avoid understanding it.

This was a developing issue prior to anything I did. The media and previous leaks started that landslide issue. What I did afterwards was simply point out when someone was using a restricted source to make false statements. They knew what the source said, and shared portions of it that suited their argument.

I don’t think you do know me at all, not even in the slightest. I wasn’t upset with Spacenavy being right… I was upset with his flagrant use of access to restricted sites to share information on a public video game forum… and in an attempt to overstate the capabilities of a highly classified weapon system.

I don’t agree with this at all… in fact, had Gaijin used such sources knowingly it would have damaged the development more. And again, these policies were already in place at the time that I made it clear the source he was using was restricted. I regret the fashion that I did so, and I made a bigger deal of it than it ever should have been… A quick PM to Smin or someone else to have it removed quietly would have been the better route and that’s the route I’ve taken since.

This seems more personal to you than anything else at this point. I’m not even sure you care to learn about how HPRF / MPRF or the AMRAAM works. Maybe you can go back to my “12 page wall of text” comment and start reading into some of those replies instead.

This is the AIM-120 thread, I don’t know what the personal attacks and insults are for but certainly they aren’t in support of your original points on HPRF radars.

And no, you weren’t there.

Yes I did, and I was reprimanded. We’re on much smoother terms now. If I’m “proved wrong” it is what it is. I was wrong. Regarding that specific situation, I wasn’t. I just shared the citation showing it was restricted and as I said, primarily because the person was claiming a bunch of stuff the citation didn’t say… thinking no one else would check their source.

You said I’d go to great lengths because someone proved me wrong, which is precisely what you’re doing right now. You’re making this overly personal and derailing my thread. Let’s get back to the subject of the AMRAAM and it’s guidance.

You made the following claims so far;
The AMRAAM solely guides in HPRF (admitted you were wrong after repeated primary sources showed you were wrong).
The AMRAAM primarily locks in HPRF (this isn’t the case, and you fail to admit as much so far).
MPRF’s are used for longer range, and HPRF up close (this is just… wrong as it can be).

These three claims are the most concerning to me, which indicate a failure to understand how pulse repetition frequency works or why these rates are used.

Firstly, MaMoran has made a fantastic statement I previously quoted that serves to help understand why the AMRAAM has to have both high and medium PRF’s. This is because there are certain conditions that can cause the missile to lose track of the target that are easily exploitable. Having a MPRF frequency lock is more optimal for defensive targets… and it is expected that targets will have strong clutter since they’ll be defensive using CM’s or diving low to the ground.

The advantages of MPRF acquisition for terminal homing of an active radar homing missile are highlighted in patents such as this; US6518917B1 - MPRF interpulse phase modulation for maximizing doppler clear space - Google Patents

In fact, if you wish to better understand how radars work this is a fantastic read, has all the information you need to understand HPRF and MPRF.
https://ftp.idu.ac.id/wp-content/uploads/ebook/tdg/ADNVANCED%20MILITARY%20PLATFORM%20DESIGN/Principles%20of%20Modern%20Radar.%20Volume%20%203.pdf

Here is a section from the book, wherein you can see HPRF is better for long range detection and MPRF is better for off-nose (maneuvering / cranking targets detection).
https://cdn.discordapp.com/attachments/955829235493273680/1153205959229980722/image.png

MPRF is used for Pitbull because it provides simultaneous range and velocity measurements, has better tracking of beam aspect targets, better track of slow targets… and doesn’t suffer many of the limitations of HPRF such as range eclipsing, poor detection of low and medium speed targets.

As you can see however, HPRF is most optimal for illumination. This is why it is necessary for SARH missiles which do not have their own radar to provide a strong signal against targets at very long ranges.

Am I filing report with the DoD Lol.

I already see your terrible articulation in what you posted right now. High PRF is for close in performance. Closure Rate is the key word. A radar signal cannot differentiate where the nose of a target is. Hight PRF excels at targets with high closure rate. That is why most missile are High PRF.
Screenshot 2023-09-14 221518

I am sure your book is a fantastic read I will check it out. Again, the issue is you. Your interpretations miss a great deal of the time. Again, like literally two patches ago you swore Radars use light emissions. I am sorry, outside of the forum its more apparent you do not know much on this subject.

Are you saying the Aim54 uses Med PRF? When it goes active? Yes or No?
I want to know. I do not know

Obviously the radar is not articulating where the nose is. What it’s saying is that the closure rate is reduced in comparison to a head-on and high speed target.

I’ve never stated radars use light emissions. (Though, light is a frequency of EM spectrum)

The AIM-54A doesn’t as far as I am aware, but the AIM-54C does. Ignoring the rest of the argument and focusing solely on my use of the word “Pitbull” in the AMRAAM thread knowing it also means the AIM-54 has gone active (MPRF or not) is… not very genuine.

Please read the source, the one you shared is also clearly not referencing the AMRAAM’s radar as a “typical active radar seeker”. We know it uses a combination of HPRF and MPRF (5 kHz to 300 kHz frequencies).

I got work I will read it tomorrow and change my conclusions if there is sufficient evidence.

All you needed to read was in the image I shared.
If you read MaMoran’s post, sums it up very well.

this post is quite a read, thank you to @MiG_23M for your time and details in this post, lots to learn about one air to air ordinance the AIM-120 :D

is there anything about the missile that hasn’t been discussed yet that you want to bring into discussion?

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I’ve enjoyed the subject matter being discussed but please @Ziggy1989 dial back the confrontational language. It’s not productive. I will summon the forum mods if it continues.

A lively debate is great but it doesn’t need to be confrontational.

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We’ve been trying to find information on the battery life / guidance time of the missile but so far I’ve been unsuccessful.

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Without knowing the credibility of this, I’m thinking this thread may be an interesting skim read:

https://www.key.aero/forum/modern-military-aviation/missiles-and-munitions/100370-aim-120-range-questions?page=1