Saudi Arabia F-15SA Deal Details Released

[umair86]

why not get some of these old F-15c/ds from KSA get them upgraded to have a great Air Superiority platform saudi F-15s doesn't have much flying time on them and even US plans to keep C/D beyond 2025.

 

[Chogy]

Guys, AESA isn't magic. Traditional radars like the APG-63 mechanically-scanned have blown a lot of airplanes out of the skies over the years, and will continue to do so for decades despite AESA technology.

 

[Kinetic]

Does it mentioned whether it is Silent Eagle or not? I can't see anything new or special on the list for those huge amount!!!

 

[500]

Guys, AESA isn't magic. Traditional radars like the APG-63 mechanically-scanned have blown a lot of airplanes out of the skies over the years, and will continue to do so for decades despite AESA technology.

AESA is not magic, its just more range, more jam resistant, faster scan, multitask, more reliability...

Does it mentioned whether it is Silent Eagle or not?

Not.

I can't see anything new or special on the list for those huge amount!!!

1. APG-63(v)3 + AIM-120C/7 - boosting BVR air-air capabilities.
2. JHMCS + AIM-9X + AAS-42 - boosting WVR air-air capabilities.
3. APG-63(v)3 + AAQ-33 + 3rd gen LANTIRN nav + various ground attack munition - boosting strike capabilities.

 

[Chogy]

I didn't say AESA wasn't better, I said it's not magic. There is an implication that any fleet of AESA-equipped fighters will somehow become invincible if the opposition only has a "lowly" mechanically-scanned system.

 

[gambit]

Guys, AESA isn't magic. Traditional radars like the APG-63 mechanically-scanned have blown a lot of airplanes out of the skies over the years, and will continue to do so for decades despite AESA technology.

AESA is not magic, its just more range, more jam resistant, faster scan, multitask, more reliability...

I didn't say AESA wasn't better, I said it's not magic. There is an implication that any fleet of AESA-equipped fighters will somehow become invincible if the opposition only has a "lowly" mechanically-scanned system.

The parallel importance and dependency between the transmitting mechanism (antenna) and the data processing capability (computer) cannot be understated. Currently, the technology bias is in favor of the computer, meaning there is -- and has been for decades -- an excess of data processing capability for every design, be it for air traffic control or airborne detection. The initial perception is that for airborne platform, resource limitations, from internal space to electrical, are the reasons why there is a great capability discrepancy between the AWACS class and the 'fighter' class. That said...In reality and in details, and the devil lives in details, the 'single-beam' limitation in the classical antenna, be it concave dish or planar array, is the primary determinant on how much data processing capability is installed into the entire design. If the need is great even the small F-16 has enough internal space to house a more capable computer and its electrical system is more than sufficient to power that computer.

The single-beam feature is a known structural limitation that rendered most 'multi-functions' radars sequential in those functions. Some designers even gone as far as categorizing them as 'pseudo' multi-functions systems. The more capable systems can alter beam characteristics, such as pulse repetition freq (PRF) or pulse widths, to adapt to new environments and to improve target resolutions. But the radar computer must still adapt in sequence in both beam characteristics and in the data processing that came from those diverse beam characteristics. Then the system must prioritize between functions and this mean making compromises between functions. For example, an air defense radar may have to ignore 'friendly' identifications in favor of the immediate high altitude threats but then leaves itself vulnerable to low altitude 'pop-up' inbound threats. The result is that an air defense radar system must have multiple transmitters at different freqs and all data processing must be centralized, creating an unwielding, clumsy, and not very mobile system.

An 'active electronic scanning array' (AESA) system is in principle the same as that multi-beams and multi-freqs air defense radar system. The array partitioning software create multiple beams and for the first time in these decades, there is a balance, or at least a near balance, between transmitting mechanism (antenna) and data processing (computer). It is now that the aircraft resource limitations argument is valid. However, because the main issue is still data processing, an ineptly designed and built AESA system, particularly its softwares, can be outclassed and defeated by a superior designed and built traditional single-beam system.

Enter 'God'...

Session 3B.1 Ubiquitous radar: an implementation concept

Contemporary signal processing combined with phased array technology using digital beamforming enables development of an important new radar system class that provides continuous and uninterrupted multifunction capability within a coverage volume. The central idea of Ubiquitous Radar is to “look everywhere all of the time.” The concept requires illuminating a wide coverage volume while continuously receiving signals from a “pincushion” of narrow beams filling the volume. There are no gaps either in coverage space or in time, so that all targets can be detected at the earliest time and tracks initiated. Conceptually this technology can combine surveillance, tracking and weapon control. Continuous coverage from close-in “pop-up” targets in clutter to long-range targets impacts selection of waveform parameters.

A 'single-beam' system can only 'look' in the direction of its antenna. With an AESA system, the theoretical beam quantity it can produce is of its total transmit-receive (TR) modules quantity installed, meaning if the array has 1000 TR modules, there can be 1000 beams. Realistically, because of other factors like interference between TR neighbors, beam widening over distance, and many others, the total effective beams that can be produced are far less than theoretical. Nevertheless, the accummulated engineering and operational skills from the traditional single-beam systems so far have been transferred to the current generation of AESA systems.

Active Electronically Scanned Array - Wikipedia, the free encyclopedia

The primary advantage of a AESA over a PESA is that the different modules can operate on different frequencies. Unlike the PESA, where the signal was generated at single frequencies by a small number of transmitters, in the AESA each module broadcasts its own independent signal. This allows the AESA to produce numerous "sub-beams" and actively "paint" a much larger number of targets. Additionally, the solid-state transmitters are able to broadcast effectively at a much wider range of frequencies, giving AESAs the ability to change their operating frequency with every pulse sent out. AESAs can also produce beams that consist of many different frequencies at once, using post-processing of the combined signal from a number of TRMs to re-create a display as if there was a single powerful beam being sent.

Ground stations or AWACS type radar platforms do not have the same physical limitations as the smaller fighter-type aircrafts. Advances in computing power moved the 'ubiquitous radar' out of the conceptual stage and into the financial stage. This level of observance and awareness, or 'omnipotence' in a manner of speaking, is possible only with an ESA system.

Session 3B.1 Ubiquitous radar: an implementation concept

The CPI (coherent processing interval) must be long enough to achieve a signal-to-noise ratio significantly above 0 dB in order to efficiently perform non-coherent integration. The approach, sometimes termed “track-before-detect” then accounts for range-walk and Doppler-slide to achieve a specified detection probability.

To date, the greatest threats to US 'stealth' class aircrafts are bi-static radars and this 'track-before-detect' feature made possible with an ESA system. Bi-static radars are proven concepts and systems but they are structurally demanding, requirements are multiple stations that should remain stationary for long periods of time, thereby making them vulnerable to attacks, and precise synchronization between stations down to the pico-seconds level, in order to be effective. This requirement renders most militaries out of the race in 'stealth' detection, ground or airborne. This leaves the 'track-before-detect' feature.

SkylondaWorks Scrapbook Coherent vs. Non-Coherent Integration

Coherent vs. Non-Coherent Integration

Coherent integration gain is the effect obtained by increasing the length of time during which a coherent signal is observed. An example is the 3 dB gain in SNR experienced by doubling the observation time of a CW signal (most easily viewed by looking at spectral estimates of increasing lengths -- 128 samples to 256 samples to 512 samples, etc). To obtain coherent integration gain, the signal must itself be coherent (i.e., occupy a small fraction of the analysis bandwidth).

Non-coherent integration gain is the effect obtained by averaging together signal estimates taken during successive time slices, each having the same, fixed length. An example is the averaging of spectral estimates by performing point-by-point summation of the power in identical frequency bins, which smooths out the noise variance, but does not actually increase the SNR itself. A similar effect is observed when averaging together successive radar power returns point-by-point in identical range bins.

Just about %99.999 of single-beam radar systems deployed, ground or airborne, are 'detect-before-track' systems. This means a body's radar reflectivity must rise above a certain signal strength -- clutter rejection threshold -- before the radar system will associate a data set identifier and assign a priority level to this body. This is a declaration that a target warrant focus of attention.

Track-before-detect - Wikipedia, the free encyclopedia

In radar technology and similar fields, track-before-detect (TBD) is a concept according to which a signal is tracked before declaring it a target. In this approach, the sensor data about a tentative target are integrated over time and may yield detection in cases when signals from any particular time instance are too weak against clutter (low signal-to-noise ratio) to register a detected target.

What 'track-before-detect' does is invert the conventional radar operations wisdom in that the clutter rejection threshold is lowered to either zero or near zero, then all objects that produces spatial-temporal dislocations, fancy words for movements, will be monitored without declarations until any of those dislocations crossed a threshold. Variations of track-before-detect schemes have been installed with some traditional single-beam radar systems but operational effectiveness remains limited precisely because of the single-beam versus search volume relationship. Other issues are that the lowered clutter rejection threshold produced false positives. Software based compensators alleviated some but not eliminated these false positives. The antenna's mechanical sweeping or rotating movements produces time delays in tracking these spatial-temporal dislocations. Because of these issues, track-before-detect detection schemes proved useful in meteorological observations where there is no need to focus on any individual body like a rain drop, other than the main body of the meteorological phenomenon under observation, and not widely deployed in military applications. Because track-before-detect is data processing related, other companion software based compensation methods were also created to deal with the limitations of the traditional single-beam radar system, such as order statistic constant false alarm rate processing (OS-CFAR)...

Performance analysis of order-statistic CFAR detectors in time diversity systems for partially correlated chi-square targets and multiple target situations

In radar systems, detection performance is always related to target models and background environments. In "time diversity systems", the assumed Swerling complete correlation (slow fluctuation) and complete decorrelation (fast fluctuation) target models may not predict the actual system performance when the target returns are partially correlated. The probability of detection is shown to be sensitive to the degree of correlation among the received pulses. In this paper, we derive exact expressions for the probability of false alarm (Pfa) and the probability of detection (Pd) of a pulse-to-pulse partially correlated target with 2K degrees of freedom in a pulse-to-pulse completely decorrelated thermal noise for the order statistics constant false alarm rate (OS-CFAR) detector and the censored mean level CFAR (CMLD-CFAR). The complete analysis is carried out for the "non-conventional time diversity system" (NCTDS) and multiple target situations. The obtained results are compared with the detection performance of the "conventional time diversity system" (CTDS).

The list of these software based compensators is considerable and a testament to the creative genius of working radar engineers but the flexibility of an AESA system is driving them towards these newer ESA-based radar designs. It is only because of manufacturing difficulties and therefore costs that the AESA type is not widely deployed.

Bottom line is this...Against US 'stealth' class bodies, the traditional single-beam mechanically motivated radar system known today will have statistically insignificant odds at effective detection, let alone track, of those 'stealth' aircrafts. A 'non-stealth' fighter equipped with an AESA radar system, assuming all the commensurate softwares are also installed, will have a grossly unfair advantage over its adversary in detection range and target resolutions. An AESA system is not magic, but with the right software engineering talents to support the hardware, to a defeated adversary it might as well be magic.

 

[Chogy]

Excellent and detailed description. With appropriate software, an AESA system will undoubtedly have an advantage, but mechanical scanning will be with us (and effective) for a long time, and the scan rate, PRF (pulse repetition frequency) and frequency agility continue to make it viable.