Chengdu J-10 Multirole Fighter Air Craft News & Discussions

[wild peace]

1.0 Introduction
http://www.f-22raptor.com/pix/photos/radar/gal_146_b_1.jpg
The F/A-22's avionics and software system is the most advanced ever integrated into an aircraft. It is the first aircraft to use integrated avionics, where the weapons management system, electronic warfare system and the AN/APG-77 radar work as one, giving the pilot unprecedented situation awareness.

A joint venture of Northrop Grumman's Electronic Sensors and Systems Division (ESSD) and Raytheon is developing the advanced AN/APG-77 active-element electronically scanned array radar for the F/A-22.


2.0 Capabilities
The AN/APG-77 radar is designed for air-superiority and strike operations and features a low observable, active aperture, electronically-scanned array with multi-target, all-weather capability.

http://www.f-22raptor.com/pix/illustrations/af_radar_bvr.gif

The radar is key to the F/A-22's integrated avionics and sensor capabilities. It will provide pilots with detailed information about multiple threats before the adversary's radar ever detects
:: Beyond Visual Range attack, executed by 2 F/A-22's
the F/A-22. This is also called BVR, or Beyond Visual Range capability.

It will give an F/A-22 pilot the possibility in air-to-air combat, to track, target and shoot at multiple threat aircraft before the adversary's radar ever detects the F/A-22.


3.0 Technology
The F/A-22's AN/APG-77 radar is an active-element, electronically scanned (that is, it does not move) array of around 2000 finger-sized transmitter / receiver modules. Each module weights ca 15g and has a poweroutput of over 4W. The APG-77 is capable of changing the direction, power and shape of the radar beam very rapidly, so it can acquire target data, and in the meantime minimizing the chance that the radar signal is detected or tracked.
http://www.f-22raptor.com/pix/illustrations/af_radar_capabilities.gif

:: Multiple function performance of the AN/APG-77 radar system, varying from simple area sweeps to tracking and missile fire control, all at the same time.

Most of the mechanical parts common to other radars have been eliminated, thus making the radar more reliable.This type of antenna, which is integrated both physically and electromagnetically with the airframe, provides the frequency agility, low radar cross-section, and wide bandwidth necessary to support the F/A-22's air dominance mission.

One requirement that drove all of the ATF designs was a wide field of regard for sensors, enabling the Raptor to acquire and track multiple targets beyond visual range. The requirement called for a 120-degree radar field of regard on each side of the nose.

A forward-looking infrared search and track capability was also desired. Lockheed approached the field-of-regard requirement for the radar with three radar arrays placed in the nose of the aircraft (one facing forward and two facing sideways). Each wing root carried an infrared search and track system that operated through faceted windows.


4.0 Radar Software
The avionics software is to be integrated in three blocks, each building on the capability of the previous block. Block 1 is primarily radar capability, but Block 1 does contain more than 50 percent of the avionics suite's full functionality source lines of code (SLOC) and provides end-to-end capability for the sensor-to-pilot data flow

This Block 1 software enables the basic operation of the radar and its initial mode complement, including the simultaneous operation of search and track modes and systems health and maintenance or built-in-test modes. For more information on the F/A-22 software in general, click here.

At the Boeing Avionics Integration Laboratory the F/A-22 radar was integrated with the avionics mission software and other aircraft avionics sensors such as the electronic warfare system, and the communications, navigation and information systems.


5.0 Testing
By the first quarter of 1998, the radar was delivered to The Boeing Company's F/A-22 Avionics Integration Laboratory in Seattle, Wash., where engineers integrated the radar with other F/A-22 avionics.

Meanwhile, flight testing of a second F/A-22 radar continued aboard a modified Boeing 757 testbed aircraft at ESSD. The test bed consistsed of an F/A-22 forward fuselage installed on the 757's forward pressure bulkhead. Electronic warfare (EW) and communication, navigation and identification (CNI) sensors were mounted directly on the sensor wing, which was designed to simulate the sensor positioning found on the F/A-22's wings.

:: Clearly visible on the testbed are the F/A-22 nose-cone (radome), the wing on top and various sensors on the bottom of the plane.

The cabin had space for 30 software engineers and technicians who could evaluate avionics and identify anomalies, in real time. A simulated F/A-22 cockpit was installed in the cabin of the Flying Test Bed. It had all primary and secondary F/A-22 displays, as well as the throttle and stick.

The conducted flight tests successfully demonstrated the expected levels of performance of the F/A-22 radar, including basic search and track functions.

 

[Arsalan]

It carries a lot more weight then JF ....having 14 hard points then JF's 7 at the momment may be near future it is 9. and so ......

....I said we want few for our indigenous infant industry..

other About JF17 and Fc20 InshaAllah They are ours and no body except God has a power to change this.....

well i gues PakSaheen answered you perfectly.
ofcourse we woul love to see them in PAF colors, no objections!! but the thing is that can we get them. it is not only about getting two or three squadrons, the thing is can we handel them, yes, but what will the costs of doing so?
what will be the effect of using billions in getting them on our JF17 and FC20 programmes?
are the FC20 really so bad that we cannot get any good from them and so we are in desperate need of this multi million deal?
is the future of JF 17 so doomed that we must cancel future development of the project and immediately switch to new option?

well i agree the idea of getting them in small number and keep going with Jf17 and FC20 projects sounds facinating but you can not negelect its effects on future of these projects!!

i hope you understand!

regards!

 

[PakShaheen79]

@wild peace

Why you posted F-22 article here. What you want to say?

 

[gambit]

as what gambit told how RADAR sees A ship i want to share with u that its SAR and inverse SAR techniques through wigh we gets imagery of targets
A Sythetic Aperture Radar (SAR) is an airborne system which utilizes the flight path of the aircraft to simulate an extremely large antenna or aperture electronically. Over time, individual transmit/receive cycles (PRT's) are completed with the data from each cycle being stored electronically. After a given number of cycles, the stored data is recombined (taking into account the Doppler effects inherent in the different transmitter to target geometry in each succeeding cycle) to create a high resolution picture of the terrain being over flown.

Using such a technique, radar designers are able to achieve resolutions which would require real aperture antennas so large as to be impractical with arrays ranging in size up to 10 m.

An Synthetic Aperture Radar was used on board of an Space Shuttle during the Shuttle Radar Topography Mission (SRTM).

SAR radar is partnered by what is termed Inverse SAR (abbreviated to ISAR) technology which in the broadest terms, utilizes the movement of the target rather than the emitter to create the synthetic aperture. ISAR radars have a significant role aboard maritime patrol aircraft to provide them with radar image of sufficient quality to allow it to be used for target recognition purposes.

I will explain SAR in a perspective that us GUYS can understand...It worked in class before...

Suppose you are photographing a beautiful and NUDE woman, say for Playboy magazine. You have a special camera that does not capture images on chemical film but in an electronic format. This camera has a viewing aperature of 3 meters. After one shot, you take a sidestep, your span is also 3 meters, then you take another shot. At this point this special camera append the aperature of the second shot to the aperature of the first shot to create a virtual aperature of 6 meters. Physical aperature is 3 meters versus virtual aperature of 6 meters. You also have a new angle of the model which include new details about her body that usually interests us guys. As you continue to sidestep and take a shot with each pause, this special camera continue to append the new position's physical aperature to the virtual aperature that is still in memory. So after ten steps, you have a virtual aperature of 30 meters plus increasing details on the model, assuming you are circling the target, of course.

Obviously memory size of the SAR computer is extremely important as each position change increases target details. Ground targets produces the most as the Earth itself such as hills and rivers will return information along with the building that is the desired target. The target itself could be bland from one angle and all of a sudden produces complex echoes from many shapes and different surfaces. Sort of like the nude woman's back versus her much more interesting front side, natch? The high resolution image from a SAR system does not necessarily come from a 'per pulse' operation but from a composition of many pulses as the platform travels. So if you have short term memory issues, then what good are you? Limited memory capacity is the equivalent of having short term memory problem in humans as echoes from later pulses can force the system to erase any information from earlier pulses. Precisely because target information is unpredictable from point to point as the SAR system is in motion, many SAR systems will stop transmission after X distance traveled and proceed to process the returns from these many points. More sophisticated systems will have this procedure done faster than lesser capable systems.

Inverse SAR (iSAR) is like having you, the perving photographer, stand still while the nude woman model rotate or move in a way that would allow her different features to be photographed.

From pulse to pulse, that is from point to point as the SAR system travels, unexpected atmospheric phenomenon can interfere with the entire operation. The fancy phrase here is 'inhomogeneous medium' and anomalous propagation is the consequence...

WHAT ARE ANOMALOUS PROPAGATION AND FALSE ECHOS?

WHAT ARE ANOMALOUS PROPAGATION
AND FALSE ECHOS?

In cases where the index of refraction is unusual, AP is much more likely to show on radar. In extreme cases, the air near the ground may be so cold and dense that a radar beam that starts out moving upward is bent all the way down to the ground. This produces strong echoes at large distances from the radar.

Processing power and memory capacity in the SAR computer directly affect the quality of the final image so the more sophisticated SAR system will be abler to compensate for these unpredictable and uncontrollable events. The word 'compensate' here can be a bit misleading as the degraded or false echoes must be received as they are. They cannot be passed through filters as they are, in a manner of speaking, legitimate echoes that came from an atmospheric phenomenon. They are 'compensated' in the sense that hopefully subsequent transmissions will produce better target echos that the SAR computer can use to eliminate the degraded echoes.

What we have talked about so far is called 'spotlight' SAR...And there is 'stripmap' SAR...

Glossary of remote sensing terms

Compared to conventional SAR strip mapping mode, which assumes a fixed pointing direction of the radar antenna broadside to the platform track, Spotlight SAR is capable of extending the high-resolution SAR imaging capability significantly. This is achieved by keeping a target within the spotlight illumination of the radar beam for a longer time through electronic beam steering, resulting in a longer synthetic aperture which leads, in turn, to increased azimuth resolution (graphic 1).

Stripmap SAR basically just point the pulses at no target and process all returns, resulting in a band of electronic information. The beam is broad in stripmap and narrow in spotlight. This is just very basic information on SAR.

 

[urglyfly]

Maybe i can try to translate this sentense for you :
To me
This is so hard to read in english

 

[Arsalan]

Maybe i can try to translate this sentense for you :
To me
This is so hard to read in english

???
what are you taliking about??
have you posted it on this thread by mistake or have i missed somthing??

regards!

 

[PakShaheen79]

gambit
Excellent... Can you please clear difference working of AESA, PESA and MESA radars with little explanation in simplified English? Thanks in Advance,.

 

[wild peace]

@wild peace

Why you posted F-22 article here. What you want to say?

Sorry to answer so late because I was in faisalabad to spend eid holiday in my SUSRAL .

I am sorry this is a mistake but you know F22 is for sale......


Eid mubarak for all of you

 

[PakShaheen79]

^ Lol who told you that it is for sale...

 

[Arsalan]

Mr. wild peace i hopr it is not for sale near novelty pull Faisalabad,,,
BTW i am also from faisalabad,,,,

niec to know about you,

regards!

 

[gambit]

gambit
Excellent... Can you please clear difference working of AESA, PESA and MESA radars with little explanation in simplified English? Thanks in Advance,.

Sure. For now...Assume all transmit/receive (TR) modules to be the same in quality and quantity in an array for ease of discussion.

Superposition of Waves

Understanding of the wave superposition principle is crucial to understanding basic ESA operation. Remember that each module can transmit and receive, effectively making each module a miniature radar antenna, just so happen that we hobbled together a bunch of them to take advantage of the wave superposition principle.

A Passive ESA antenna will have all T/R modules under a unified controlled operation, meaning all modules will have the same phasing, just different power output for beam forming and steerage. Passive ESA operation is the simplest and first evolution of Elect. Scan Array system.

An Active ESA antenna will have all T/R modules under selective controlled operation, meaning if there is an appropriate hardware and software combination, the radar computer will be able to not only control power output but also phase changes per INDIVIDUAL module. So if there are 100 T/R modules in an array, theoretically it is possible to have 100 individual radar operations AT DIFFERENT TIMES if desired, but nothing useful would be gained from this since each module's individual power output is too small. A Passive ESA antenna cannot do this, either none or all 100 modules work together at the same time. So an Active ESA can act like a Passive ESA but not vice versa.

A very appropriate analogy is your typical shower head in your home's bathroom. Now imagine that it is possible to control the power (pressure) output of individual holes. Now imagine that it is possible to control each hole's direction. Now imagine that is is possible to group some holes to pulsate, some holes in another group for wide area spray, and finally each group can be independently steer to any direction desired.

There is a difference between an array and an antenna. An array is a group of T/R modules. An antenna is the physical structure that contain the array. Dimension wise, the antenna usually larger than the array. It must be so because there has to be a definitive spacing arrangement between individual T/R modules.

Multi-band wide-angle scan phased array antenna with novel grating lobe suppression - US Patent 7034753 Description

Array element spacing is related to the operating wavelength and it sets the scan performance of the array.

There is a process called 'subarray partitioning' and it is possible only with AESA system. This process can create multiple smaller arrays -- subarrays -- inside the main array just like the fantasy shower head with multiple independently controlled water holes.

The current American AESA installed in the F-22 and F-35 can turn from one large array into nine smaller arrays for multiple purposes. This is what is conveniently labeled as Multi-role ESA (MESA). Only an AESA system can be a true multi-role (mESA) radar system.

Non-AESA radars can perform different operations such Track-while-Scan (TwS). But what actually happened is that the radar in scan mode picked up an echo that is above clutter (junk) threshold, it record in memory the approximate (guess) location of the target, then it continue to scan past the target. On the next scan (sweep) cycle, as the antenna's movement approaches the supposedly location of the target that is in memory from the previous scan cycle, the radar computer command the main beam to switch from the current freq to a higher one, thereby increasing target details, and if the target is still there, its new location and details are updated. So while we call this Track-while-Scan, it is not true TwS as all we are doing is guesses where the target should be and hope that we will find it again on the next scan cycle based upon information from the previous scan cycle. Scan or sweep mean the same. If the target disappeared on the new scan cycle, less capable radar system will dismiss that target to be an anomaly. This is what Very Low Obserable, aka 'stealth', aircrafts are supposed to create -- ambiguities -- from one scan cycle to the next.

Keep in mind that every radar antenna, no matter what kind, has a main beam. Same for an array that it also has a main beam. So if we can create multiple arrays INSIDE a single antenna, then we have multiple main beams. Therefore it is only with an AESA system that can create subarrays that we can have a true mESA radar system. Upon detecting a target, we can divide the main array into two arrays, one array continue to do volume search and the other array to keep watch on the target with a 'spotlight' or 'boresight' main beam. Two main beams doing two different tasks AT THE SAME TIME. Not only that, the previously mentioned Track-while-Scan (TwS) action can be done by the AESA subarray. In other words, if the main array can pseudo-TwS ten targets, for example, so can a subarray perform that same pseudo-TwS action.

Try to imagine this...With the main array, we detected thirty targets with varying distances from us. We then partitioned the main array into nine subarrays. We keep one beam to continue volume search of the area. We focus another beam on the closest target, presumably the most imminent threat, and this would be a true Track-while-Scan (TwS) operation. We focus another beam to perform pseudo-TwS on ten targets, the next group of threats down the list. Further are ten more targets heading away from us at an angle so we focus another beam to perform pseudo-TwS operation on them. That is four out of nine beams used and we still have five more beams available. We decide to focus one beam on the ground to keep track of friendly forces. Five beams used and four more beams, or subarrays, to go. We then turn one of the remaining four subarrays into a data relay for all friendly forces int the area. That leave three subarrays remaining. We can turn one of these into an interrogator (IFF). Now we have two remaining subarrays. We can turn these two remaining subarrays into a larger array to perform volume search in another direction. This is a TRUE mESA system.

The caveat here is the software so even if the hardware is capable of turning the main array into several subarrays, if the choreography software is not there, we have not even the basic AESA system. Earlier I said to assume all T/R modules are of the same quality and quantity. Now if the quality of the T/R modules from one manufacturor is not as high as another manufacturor's, then there will be serious performance differences between systems that no softwares can compensate.

Clear as mud?

 

[zavis2003]

The AESA includes multiple individual active transmit/receive (T/R) elements within the
antenna. Depending upon the precise implementation, there may be anywhere between 1000
and 2000 of these individual T/R elements which, together with the RF feed, comprise the
AESA antenna. As for the passive ESA, these elements are highly redundant and the radar
can continue to operate with a sizeable percentage of the devices inoperative. This graceful
redundancy feature means that the radar antenna is extremely reliable; it has been claimed
that an AESA antenna will outlast the host aircraft.

 

[wild peace]

^ Lol who told you that it is for sale...

I quote this before in the different thread but for you I post it again.

Senate panel agrees to open door to possible F-22 exports

The Senate Appropriations Committee voted unanimously Thursday to approve an fiscal 2010 Defense spending bill that would allow the Defense Department to develop an export version of the radar-evading F-22 Raptor fighter jet.While the committee bill, if enacted, would not repeal a decade-old law prohibiting foreign sales of the stealthy fighter, it would mark a significant step forward in opening up the Lockheed Martin Corp. jet to U.S. allies just as the plane's domestic production lines are winding down."It's a good next step," a Senate aide said of the F-22 provision in the $636.3 billion spending bill.

For years, lawmakers in both chambers have thwarted any effort to sell the F-22 overseas, arguing that exporting the advanced technologies in the fighter jet would pose a significant security risk. But proponents of exporting the plane argue that selling an export model of the F-22, stripped of secret U.S. technologies, would eliminate that risk.House lawmakers approved a floor amendment to the fiscal 2007 Defense appropriations bill that would lift the ban. But export opponents in the House and Senate eliminated that provision during conference negotiations on the bill.

The Senate's language in the fiscal 2010 bill will likely meet stiff resistance from House appropriators -- especially Appropriations Committee Chairman David Obey, D-Wis., author of the 1998 ban on F-22 exports -- who continue to be concerned about the security implications of selling the F-22 abroad.While the Senate bill maintains the export ban, it says the Defense Department "may conduct or participate in studies, research, design and other activities to define and develop an export version of the F-22A." The committee report accompanying the bill encourages the Air Force to use F-22 research and development funds to begin work on an export version of the fighter.The House bill, which was approved in July, continues the ban and does not open the door to developing an exportable version of the fighter.

But the political landscape could be shifting a bit as domestic production of the F-22 comes to an end -- a development the program's supporters in Congress fear will lead to thousands of aerospace jobs lost in dozens of states.Both the House and Senate already have approved versions of the fiscal 2010 defense authorization bill with language demanding the Pentagon report to Congress on the costs of developing an exportable version of the F-22 and any potential strategic implications.Japan is considered the most likely customer for the F-22, particularly as North Korea continues its ballistic missile testing. South Korea, Australia and Israel have also have expressed interest in buying the plane despite a price tag that could top $150 million a jet.

The Senate is expected to take up the $636.3 billion Defense appropriations bill later this month.Senate Appropriations Committee ranking member Thad Cochran, R-Miss., said Thursday that his goal is to wrap up conference negotiations with the House and send the bill to the president's desk by Oct. 1,

 

[Arsalan]

well if the deal ever materialize it will be only for countries like Israel and perhaps japan. US wont have a problem giving it to australians but they are now going with F35 so very unlikely to see an F22 with them. however if it really happens, that is if the F22 is actually saled to anyother nation it would be a downgraded version for sure. US have a policy determining a certain degree of stealth that it wold sale to other countries!!

regards!

 

[wild peace]

AESA

An Active Electronically Steered Array (AESA) takes the concept of using an array antenna a step further. Instead of shifting the phase of signals from a single high power transmitter AESA employs a grid of hundreds of small "transmitter-receiver (TR)" modules that are linked together by high-speed processors.

Each TR module has its own transmitter, receiver, processing power, and a small spikelike radiator antenna on top. The TR module can be programmed to act as a transmitter, receiver, or radar. The TR modules in the AESA system can all work together to create a powerful radar, but they can do different tasks in parallel, with some operating together as a radar warning receiver, others operating together as a jammer, and the rest operating as a radar. TR modules can be reassigned to any role, with output power or receiver sensitivity of any one of the "subsystems" defined by such temporary associations proportional to the number of modules.

AESA provides 10-30 times more net radar capability plus significant advantages in the areas of range resolution, countermeasure resistance and flexibility. In addition, it supports high reliability / low maintenance goals, which translate into lower lifecycle costs. Since the power supplies, final power amplification and input receive amplification, are distributed, MTBF is significantly higher, 10-100 times, than that of a passive ESA or mechanical array. This results in higher system readiness and significant savings in terms of life cycle cost of a weapon system, especially a fighter.

The use of multiple TR modules also means failure of up to 10% of the TR modules in an AESA will not cause the loss of the antenna function, but merely degrade its performance. From a reliability and support perspective, this graceful degradation effect is invaluable. A radar which has lost several TR modules can continue to be operated until scheduled downtime is organized to swap the antenna.
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