Agile Beams: Active Electronically Scanned Array Radars

AESAs aim their "beam" by broadcasting radio energy that interfere constructively at certain angles in front of the antenna. They improve on the older passive electronically scanned radars by spreading their broadcasts out across a band of frequencies, which makes it very difficult to detect over background noise. AESAs allow ships and aircraft to broadcast powerful radar signals while still remaining stealthy. Above is AESA on F22

The AN/APG-77 is a multifunction radar installed on the F-22 Raptor fighter aircraft. It is one of the most advanced radar today. More than 100 APG-77 AESA radars have been produced to date by Northrop Grumman, and much of the technology developed for the APG-77 is being used in the APG-81 radar for the F-35 Lightning II. The APG-77v1 was installed on F-22 Raptors from Lot 5 and on. This provided full air-to-ground functionality (high-resolution synthetic aperture radar mapping, ground moving target indication and track (GMTI/GMTT), automatic cueing and recognition, combat identification, and many other advanced features).

APG-77 is based on Active Electronically Steered Array (AESA) technology. 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. The fact that the transmitter elements reside in the antenna itself means there is no standalone transmitter – there is an exciter but that is all. As before, there is clearly a need for a receiver as well as an RDP and signal processor. The active T/R elements are controlled in the same way as the phase shifters on the passive ESA, either by using a beam-steering computer (BSC) or by embedding the beam-steering function in the RDP.

The ability to control many individual T/R modules by software means confers the AESA with immense flexibility of which only a few examples are: First each radiating element may be controlled in terms of amplitude and phase, and this provides superior beam-shaping capabilities for advanced radar modes such as terrainfollowing, synthetic aperture radar (SAR) and inverse SAR (ISAR) modes. Secondly Multiple independently steered beams may be configured using partitioned parts of the multidevice array. Thirdly If suitable care is taken in the design of the T/R module, independent steerable beams operating on different frequencies may be accommodated and Finally The signal losses experienced by the individual T/R cell approach used in the AESA also bring considerable advantages in noise reduction, and this is reflected in improved radar performance.

The AN/APG-80 system is described as "agile beam", and can perform air-to-air, search-and-track, air-to-ground targeting and aircraft terrain-following functions simultaneously and for multiple targets. As a SAR system utilizing NG's fourth-generation transmitter/receiver technologies, it has a higher reliability and twice the range of older, mechanically-scanned AN/APG-68 radar systems. Above is F-16 APG-80 Radar

One dramatic improvement is the noise figure; it is especially significant achieving such an improvement so early in the RF front end. This results in a remarkable range improvement for the AESA radar. A number of US fighter aircraft are being fitted or retrofitted with AESA radars, these are F-22 Raptor, F-18E/F (Upgrade version) fitted with AN/APG-79, F-16E/F (Block 60) fitted with AN/APG-80, F-15 and F-35 fitted with AN/APG-81. Taking for example F-16, it is interesting to see a dofference in performance between two batches (Block 50) and Block 60. Former had target detection radar range of 50 miles, which was improved to 70 miles with AESA radards (for reference F-22 covers 125miles range). The F-16 Block 60 (now the F-16E/F) shows an improvement from 45 to 70 nm (þ55%), while the F-15C range has increased from 60 to 90 nm (þ50%). Apart from the obvious improvement in range, it has been stated by a highly authentic source that AESA radar confers 10–30 times more in radar operational capability compared with a conventional radar (Report of the Defense Science Board Task Force, 2001).

The F-16E (single seat) and F-16F (two seat) are newer F-16 variants. The Block 60 version is based on the F-16C/D Block 50/52 and has been developed especially for the United Arab Emirates (UAE). It features improved AN/APG-80 Active Electronically Scanned Array (AESA) radar, avionics, conformal fuel tanks (CFTs), and the more powerful GE F110-132 engine. However the batch bought by Pakistan Air Force (F-16C/D) is equipped with AN/APG-68 (V)9 Radar Systems. Only the Block 60 aircraft, destined for the UAE, are to be equipped with a more advanced version – the Active Electronically Scanned Array (AESA) radar. The APG-68(V)9 offers 30 percent increase in detection range, improved search-while-track mode (four vs. two tracked targets) and larger search volume and improved track while scan performance. Its single target track performance has also been improved. On air/ground missions, the new radar becomes an effective sensor, utilizing its high-resolution synthetic aperture radar mode, which allows the pilot to locate and recognize tactical ground targets from considerable distances. Although previous radars had some Synthetic Aperture Radar (SAR) capabilities, the new version generates imagery-class (2 feet resolution) high resolutions pictures, comparable to pictures delivered by the most modern commercial satellites. These pictures can be acquired from very long range, at all weather conditions and provide an effective, real-time source for the targeting of long range, precision guided weapons. The radar also has increased detection range in sea surveillance mode, and enhanced ground moving target identification and mappinc capability. The radar features an inertial measurement unit that improves dynamic tracking performance and provides an auto-boresight capability, which increases accuracy.

E-Bomb – Direct Energy Warfare

6th Generation Aircraft - Airforces to End the Desire for Pilots

The rules of battle have changed over the entirety of military history. Tools such as technology, strategy, tactics and weapons have been the principal elements determining what kind of rules apply to the battlefield. What can consititute to a sixth generation fighter jets – Thats the question I am asking myself since past week. Although it might be too early to think of these questions, when even planes like JSf, PAK-FA or F-22 are not even fully opertional. The contemporary military rivalry is driven mostly by the ongoing military technical revolution. In particular, the weapons used on the future battlefield will play an important role in military affairs. Which weapons can play a key role in the future? I will try not to be too technical, such that the article is applicable to general public as well, however, I have included the research papers and appropriate links for those intending to explore more about E-Bombs or Electromagnetic Weapon Systems.

Sixth generation jet fighters are currently conceptual and expected to enter service in the United States Air Force and United States Navy in 2025-2030 timeframe. The technological characteristics may include the combination of fifth generation aircraft capabilities with unmanned capibility, unrefueled combat radius greater than 1000 nm and Direct Energy Weapon. It is latter which is a subject of this article. One form of this energy is Electronic Bomb (E-Bomb). This article aim to explore the technical aspects and potential capabilities of this type of bomb, target measurements and its comparison with other form of electromagnectic weaponry.

Research has shown that it is possible to develop such kind of device. Directed Energy research originated with research work done to determine the impact to important military systems operating in harsh electromagnetic environments. One of the most threatening and pervasive of all electromagnetic threats is that due to electromagnetic pulse.

These pulses can burst of electromagnetic radiation that results from an explosion (usually from the detonation of a nuclear weapon) and/or a suddenly fluctuating magnetic field. However, its not only the nuclear weapon who generates these pulses, Non-nuclear electromagnetic pulse (NNEMP) is an electromagnetic pulse generated without use of nuclear weapons. There are a number of devices that can achieve this objective, ranging from a large low-inductance capacitor bank discharged into a single-loop antenna or a microwave generator to an explosively pumped flux compression generator. To achieve the frequency characteristics of the pulse needed for optimal coupling into the target, wave-shaping circuits and/or microwave generators are added between the pulse source and the antenna. A vacuum tube particularly suitable for microwave conversion of high energy pulses is the vircator. These HEMP induced stresses can damage or severely disrupt some electronic systems, which are sensitive to transient disturbance. Significant potential damaging effects can occur at long ranges to virtually all systems located within line-of-sight of the detonation point. Thus it is feasible to say, that NNEMP generators can be carried as a payload of bombs and cruise missiles, allowing construction of electromagnetic bombs with diminished mechanical, thermal and ionizing radiation effects and without the political consequences of deploying nuclear weapons.

The fact that an electromagnetic pulse is produced by a nuclear explosion was known since the earliest days of nuclear weapons testing, but the magnitude of the EMP and the significance of its effects were not realized for some time. As a result of the test, a very short but extremely intense electromagnetic pulse was observed. This pulse propagated away from its source with a decreasing intensity, which is also to be expected according to the theory of electromagnetism.

According to the CBS reports dated March 2003 stated the application of experimental EM Pulse:

The U.S. Air Force hit Iraqi TV with an experimental electromagnetic pulse device called the “E-Bomb” in an attempt to knock it off the air and shut down Saddam Hussein’s propaganda machine. The highly classified bomb created a brief pulse of microwaves powerful enough to fry computers, blind radar, silence radios, trigger crippling power outages and disable the electronic ignitions in vehicles and aircraft. Officially, the Pentagon does not acknowledge the weapon’s existence.

Direct Energy Warfare

Military action involving the use of directed-energy weapons, devices, and countermeasures to either cause direct damage or destruction of enemy equipment, facilities, and personnel, or to determine, exploit, reduce, or prevent hostile use of the electromagnetic spectrum through damage, destruction, and disruption. The defensive part of Electronic Warfare includes the offensive actions such as preventing the enemy’s use of the electromagnetic spectrum through counter measures such as damaging, disrupting, or destructing the enemy’s electromagnetic capability. Such weaponry (DEW) is an evolving addition to the EW.

Characteristics of Direct Energy Weapons

The most common characteristics of the direct energy weapons is that they attack at the Speed of Light. This pose some advantage over conventional weaponry, This helps in defeating targets
such as theater and ballistic missiles before they can deploy defense-saturating sub-munitions. Another advantage of such weapons is that they can be used against multiple targets at the same time. The direct energy weapons are classified into four catagories; High Power Microwave (HPM), Charged Particle Beams (CPB), Neutral Particle Beams (NPB) and High Energy Laser (HEL). It is the latter which is highly potential for military applications (both stratagic and tactical missions). However, for E-Bomb it is HPM is a base. But offcourse when compared to Laser technology, the microwave technology lags in terms of research. HPM – use electromagnetic radiation to deliver heat, mechanical, or electrical energy to a target to cause various, sometimes very subtle, effects. When used against equipment, directed electromagnetic energy weapons can operate similarly to omnidirectional electromagnetic pulse (EMP) devices, by inducing destructive voltage within electronic wiring. The difference is that they are directional and can be focused on a specific target using a parabolic reflector. High-energy radio frequency weapons (HERF) or high-power radio frequency weapons (HPRF) use high intensity radio waves to disrupt electronics. However, High and low power, Pulsed Microwave devices use low-frequency microwave radiation which can be made to closely mimic and interact with normal human brain waves having similar frequencies. Although belong to the same family of technology, the E-Bomb deployment differes from that of HPM.

Potential for Aircraft Operations

Scleher, D. Curtis in Electronic warfare in the information age, has defined the potential of these kind of weapons for Aircraft Operations. DEWs have great potential for aircraft operations since crews can enhance their own survivability in the battlefield, where the aircrafts are susceptible and vulnerable to missile threats, by protecting themselves with electromagnetic shields. In such environment, DEW systems may prevent the aircraft from threats by decreasing the detection and targeting capability of enemy. They may also aid in hit avoidance by deflecting, blinding, or causing the incoming missile to break lock and finally, where necessary, to destroy the missile itself before it reaches its target. An additional approach might be to defeat the fusing system of the incoming missile. However, when deploying these bombs, getting the projectile successfully right is the key, such that useful damage can be produced. Further information about the deployment of these DEWs can be accessed from Electronic warfare in the information age. By this stage one difference between HPM and E-bomb is apparanet, despite belonging to same technological family, and this difference is their deployment. HEMP – High Altitude Electromagnetic Pulse is not a directed energy weapon. The reason why HEMP is defined as an electromagnetic weapon is that it produces similar effects in electromagnetic spectrum and can cause similar impacts on electronic devices. The potential effects of a designed HPM weapon strongly depends on the electromagnetic properties of the target. Since it is difficult to get the required intelligence, the complexity of real systems poses technical difficulties. A typical HPM weapon system basically includes a prime source that generates the intended power, an RF generator, a system that shapes and forms the wave into the intended form, a waveguide through which the generated wave travel, an antenna that propagated the wave, and the control unit that manages all the steps.

AGM-154 Joint Standoff Weapon l

Delivery system considerations for E-bombs are very important. The massed application of such electromagnetic weapons in the opening phase of an electronic battle delivered at the proper instant or location can quickly lead the superiority in the electromagnetic spectrum. This package might mean a major shift from physically lethal weaponry to electronically lethal attacks (via e-bombs) as a preferred mode of operation. Potential platforms for such weapons delivery systems are AGM-154 JSOW (Joint Stand Off Weapon) glidebomb (shown above) and the B-2 bomber (shown below). The attractiveness of glidebombs delivering HPM warheads is that the weapon can be released from outside the effective radius of target air defenses, minimizing the risk to the launch aircraft, which can stay clear of the bomb’s electromagnetic effects.

B2-Bomber refueling

Another delivery method of e-bomb may be the use of UAVs. The technology of UAVs is still developing and partly immature; however, improvements can be expected in the next decade.

The e-bomb targets mission essential electronic systems such as the computers used in data processing systems, communications systems, displays, industrial control applications, including road and rail signaling, and those embedded in military equipment, such as signal processors, electronic flight controls and digital engine control systems. I must point out that when e-bomb outputs are too weak to destroy these systems but strong enough to disrupt their operations, system performance can be degraded. The relation between the altitude (shown below) where the e-bomb is detonated and a representation of the lethality range. Target information (to include location and vulnerability) becomes an important issue.

E-Bomb Footprint: Source <a href="http://cryptome.org/ebomb.htm/">Carlo Kopp</a>

E-Bomb – Science Fiction or a Fact?

Sor, can this hypothetical e-bomb be a significant weapon for the future battlefield? Theoratically, the military advantage obtainable with e-bombs is related mostly to their operational significance. Will future battlefields will be won by the countries that best manage the revolution in military affairs or technological revolution? If latter is the case, then one has to remind himself that technology is not a winner on its own, but it has been, and it will continue to be, a critical enabler. If everything else is equal, the side with better technology will win. Finally, can the country that first develops this new weapon have a significant and exploitable military advantage against other powers? Is is feasible for a nation to invest in this kind of bomb ? – The Debate Continues

As I have mentioned earlier, this piece is not research but infact just collection of some work, to explore the potential of EM technology in modern warfare as well as extending our previous discussion of Electronic Warfare For further reading about the subject I strongly suggest to read the following researches

References
Kopp, C. 1993. A doctrine for the use of electromagnetic pulse bombs. Air Power Studies Centre. Paper No. 15.
Kopp, C. 1996. An introduction to the technical and operational aspects of the electromagnetic bomb. Air Power Studies Centre. Paper No. 50.
Kopp, C. 2006. Directed Energy Weapons-Part 1. Defense Today May/June Publication.
Mazarr, Michael J. 1993. Military Technical Revolution-A Structural Framework. Center for Strategic and International Studies. Washington, D.C.
Scleher, D. Curtis. 1999. Electronic warfare in the information age. Boston: Artech House.