Posted at 11.29.2018
"Hide and Seek" in the wonderful world of Wave
Student name: Choi Ho Lam
Thank you for providing this valuable opportunity for me to investigate on this subject. As this issue consists of military technology, it offers a deeper knowledge of wave theory and utilization in daily life. However, in normal adjustments, such kind of subject matter is not included, as possible quite controversial. Thankfully, in this CCST course, I am permitted to choose this matter and enrich my engineering knowledge to a more deeply extend.
After watching the show "Hilter's Stealth Fighter", it gives me a clearer way on starting the study on this topic. It enriches my knowledge on the use of Memory in relationship with RF wave properties.
Teaching assistants of the course
The teaching assistants in the course are helpful. Their thoughts help me to thin my way in looking into to specific matters like radar and specific technology related to radar. Without their help, I would still wonder in the wild world of military and aimlessly looking for a suitable topic.
Radar diagnosis and stealth technology are such as a game of "disguise and seek" with the application of wave technology. They discuss the opposite seeks, either finding one or avoid from being found. In the wonderful world of military, this is a game that changes the fate of the world and burning off is not an option.
During the earth Conflict II, the deployment of radar in Uk had evolved the tide of struggle in the British Channel. Fighting with each other against 2550 German fighters and bombers, the Royal Air Force (RAF) could strike strategically and halted German invasion with just 1963 planes. After this battle, British dished up as the previous stand among European countries against Nazi Germany.
With such important background, the military value for radar as well as its counterpart, stealth technology were deeply looked into. Nazi Germany acquired suffered from a primary defeat out of this battle. Since then, Nazi Germany completed various studies on stealth aircrafts. Just one month near the end of WWII, the first prototype stealth bomber, Horten Ho 229 originated. Recent research from National Geographic show that such airplane decreases the detection range of English radar by 37%, which is already enough for wiping out the complete RAF. It was so fortunate that the airplane wasn't in mass development or the span of history would have been change completely.
This paper aims at studying the use of wave technology in the utilization of radar, as well as the principles in some of the counter-top radar measures. Since it is a CCST coursework, a few of the complicated mathematical strategies and modern approach to radar jamming would be omitted. Nevertheless, by learning such technology, we can establish a better knowledge of different wave phenomena and know how they change our life.
3. 1 Radar
Radar stands for Radio Detecting and Ranging. Generally, radar detects a way object by sending a pulse of EM wave and measures enough time and consistency for the mirrored pulse. By examining these factors, the velocity and the distance of the even object can be found.
In a macroscopic view, radar consists of 3 basic parts, a transmitter, a duplexer and a receiver.
The transmitter emits a short-duration high-power radio frequency (RF) pulse. The pulse will travel through the transmitter antenna and emit outwards. The antenna can provide appreciate space for productive distribution of RF pulse.
When the RF pulse struck an obstacle, the RF pulse is mirrored back to the receiver. The receiver antenna will have the signal and evaluation enough time of travel as well as the regularity of shown pulse.
Since the receiver antenna is very sensitive as it is assumed to be acquiring the small pulse reflected again from considerably distance, a duplexer is installed to change the between two antenna. This can ensure only 1 antenna is in use and prevent recipient antenna receiving transmission directly from the transmitter antenna, which could damage the receiver antenna.
In a microscopic view, an alternating electric current (AC) comes to the antenna. After that it produces a perpendicular alternating magnetic field surrounding the antenna.
By Lenz's Legislation, for a sealed loop carrying a current, it would produce a magnetic field perpendicular to current across the loop. In reverse, for a finished loop experience an alteration in magnetic field, a current perpendicular to magnetic field is produced to oppose the change.
The combo of alternating current and magnetic field produces the electromagnetic wave which used for recognition. The consistency of the EM influx can be transformed by modifying the AC rate of recurrence. The consistency of the electromagnetic influx is usually arranged to between 3 kHz to 300 GHz at radio regularity (RF). It varies depends upon the usage. With a higher frequency, using relationship with swiftness of light (C) and wavelength (О») C=FО», the wavelength of RF influx is shorten. This decreases the electrical amount of the antenna to and makes it easier to build.
In military use, the RF pulse would established to lower occurrence portion in the RF variety, usually between 7 to 11. 2 GHz, which is called the X strap. Being in RF variety, the high consistency radar pulse can create a radar cross-section of aircraft with an increased resolution, which helps identify plane more effectively. In more advance use, a much lower frequency is used to uncover stealth aeroplanes since it can give a much more sensitive signal. With a low regularity, the wavelength of radar pulse is comparable to size of stealth fighter and creates a scattering in resonance region rather than optical region, turning it more obvious on radar. However, the occurrence of the radar pulse cannot be less than 800 MHz, in any other case the EM pulse could have insufficient penetrating electric power and easily be assimilated by raindrops. Besides that, the quality of low regularity radar is relatively poor, and gives a poor screen. It is only effective against stealth aeroplanes of length much like wavelength.
When the radar pulse is bound back to the radar, the antenna experience an alternating change in magnetic field. This will produce an alternating electro-mechanical field and thus an AC current to flow in circuit. Since the returning signal is weak, it could go through an amplifying circuit to raise the amplitude.
In examining the signal, the occurrence and time of travel would be taken to find the speed and speed of detection focus on. When the radar pulse extends to an subject, it is shown and the occurrence is shifted by Doppler Impact.
Since the rate of RF wave is actually the acceleration of light (C), the distance (S) can be express as a period (t) function,
S = Ct/2.
It is divided by two since the radar pulse travel through the same distance twice.
To calculate acceleration of moving thing, we will get out the change in occurrence (Doppler rate of recurrence) of the returning wave. In case the far subject is moving, the object would create a Doppler change to the radar pulse. This Shifted rate of recurrence () can be portrayed by original frequency (), the moving rate (V) and quickness of light (C).
which provides us the Doppler occurrence ().
For convenience, one assume, such that, and simply the equation as
3. 2 Radar jamming and deception
Radar jamming and deception usually refer to the objective of saturating the radar with noise and phony information, reducing the detection selection of radar as well as the exactness of the radar. There mainly two types of jamming, either mechanical jamming or digital jamming.
Mechanical jamming usually refer to use of bodily been around thing to echo and re-reflect RF sign back again to radar, creating the radar to be saturated with phony return indication.
The commonly used mechanical jamming methods that take up wave rules are chaff and corner reflectors.
Chaff is bundles of reflective aluminium strip of various lengths. The aircraft drops these strips in air. When radar pulse reaches these strips, the radar pulse is mirrored and scattered in every direction, creating huge come back sign to the receiver. This may deceive the radar as "seeing" huge plane and deplete adversary resources like ammunition on firing down the wrong target.
Corner reflector reflects incoming radar pulse at other perspective. Corner reflector is composed of either several reflective planes, perpendicular to each other. This construction allows the inbound radar ray fully reflected back again to the source. Yet this also raises special profession of place reflector, making it harder to carry by aircraft. The tails of the stealth fighter are designed to be acute perspective, such that it avoids forming nook reflector, allowing radar to identify the aircraft.
Electronic jamming refers to the lively emission of RF pulse to the radar, saturating the radar with wrong return and noises. It includes place jamming, sweep jamming, barrage jamming, cover pulse jamming and digital radio consistency memory jamming.
Spot jamming, sweep jamming, barrage jamming uses the same basic principle, occupying the radar with high energy pulse and leading to destructive disturbance of the RF wave.
Spot jamming refers to jamming one specific frequency with high energy indication.
Sweep jamming refers to jamming one specific regularity with high energy sign when the radar is moving over from one rate of recurrence to another.
Barrage jamming identifies jamming all specific frequency with high energy transmission, however since it cover full selection of frequency, each regularity are partially jammed.
Cover pulse jamming refers to false return signal as noises. As radar will get certain amount of ambient sound, for example, like scanning through eagle and other styles of bird, so it could be utilized as disguise for fighter to cover up from radar. With pulse jamming system installed, the aeroplanes analysis the inbound radar signal and find suitable regularity for false sound return.
Digital radio consistency ram is a repeater approach that analysis the incoming radar pulse and changes the going back rate of recurrence as well as time of come back. The indication would be wait and diminish. Thus giving a false sign of very far distance between aeroplanes and radar. Moreover, the occurrence would also be shifted and produce a false Doppler transfer on radar indication. This dividends with bogus information about the speed of plane.
3. 3 Usage of RAM
Besides of active jamming and deceiving radar, the military services develop RAM to avoid radar detection from the foe.
RAM stands for the Radar-Absorbance Material. Based on the detecting radar occurrence, different types of RAM are being used to construct stealth aircrafts.
Iron ball paint absorber
Iron ball car paint is one of the generally used RAM. It contains tiny spheres coated with carbonyl flat iron and ferrite. As radar waves induce molecular oscillation in this color, the would dissipate as high temperature. This may absorb the radar and reduce the representation of radar wave.
The set ups of re-entrant triangles among the surface foam absorber covering help reduce representation of radar ray back to radar transceiver. In the foam absorber coating, the foam was lower into tiny square pyramid. This structure reflect incoming wave several times and decrease the energy of the radar wave.
In practice, the width and height would change based on the incoming radar wave. The main reason for adjusting height and width ratio is to achieve maximum internal reflection within the airplane surface as is feasible.
The wave process deployed by Jaumann absorber is harmful disturbance. Gerneally, Jaumann absorber contain two similarly spaced coating and a earth metal plate. It cancels out the inbound influx by producing detrimental interference.
When a radar sign strikes to the surface of Jaumann absorber, the wave split in to two waves, is reflected at glossy surface of the Jaumann absorber, while the other enters the part. The ray will reflect again by the metallic ground plate. The two layers having a complete spacing of О»/4 will allow the wave mirrored back to surface at anti-phrase compare to incoming ray, where the ray have travelled a total of О»/2 distance.
Radar principle utilize various influx property in tracing the adversary. In engineering, there's a sub-discipline for radar analysis, for a far more specific interpretation of radar sign. This paper includes only few example and it was simply a spot of iceberg. However, in simply a brief analysis, we can see improvement of technology as people know more about wave and by using this knowledge to build stealth airplane. This game of "hide and seek" can be damaging to world as it brings a higher casualties in battle, however this game has also shown to be saving life battle and pushing the improvement of technology.
Would this game be good for human? It would be an unanswered question waiting for the people to decide.
Radar. (n. d. ). Retrieved from http://en. wikipedia. org/wiki/Radar
O'Donnell, Robert. RES. LL-001 Release to Radar Systems, Springtime 2007. (MIT OpenCourseWare: Massachusetts Institute of Technology), http://ocw. mit. edu/resources/res-ll-001-introduction-to-radar-systems-spring-2007 (Accessed 28 Nov, 2014). License: Creative Commons BY-NC-SA
Wolff, C. (n. d. ). Radar Rule. Retrieved from http://www. radartutorial. eu/01. basics/Radar Principle. en. html
Toomay, J. , & Hannen, P. (2004). Radar Concept for the Non-Specialist (3rd ed. ). SciTech Posting.
Hitler's Stealth Fighter [Action picture]. (2009). United Express of America: Country wide Geographic.
Garcia, L. (n. d. ). How Waves Helped Win the Conflict: Radar and sonar in WWII. Retrieved from http://www. ww2sci-tech. org/lessons/lesson3. pdf
Deb, N. N. (2006). Telecommunication Engineering (1st ed. ). New Age International.
Bole, A. , Wall membrane, A. , & Norris, A. (2014). Radar and ARPA Manual Radar, AIS and Focus on Tracking for Sea Radar Users. Elsevier.
Varshney, L. (2002). Techie Report Radar Guidelines (3rd revision. ). NY: Syracuse Research Firm.
Lorell, M. (2003). The U. S. Fight Aeroplanes Industry, 1909-2000. National Security Research Institute.
Radar jamming and deception. (n. d. ). Retrieved from http://en. wikipedia. org/wiki/Radar_jamming_and_deception
Radar-absorbent material. (n. d. ). Retrieved from http://en. wikipedia. org/wiki/Radar-absorbent_material
Zikidis, K. , Skondras, A. , & Tokas, C. (2014). Low Observable Ideas, Stealth Airplane and Anti-Stealth Systems. Journal of Computations & Modelling, Vol. 4(No. 1, 2014), 129-165. Retrieved from http://www. scienpress. com/Upload/JCM/Vol 4_1_9. pdf
Stealth Technology. (n. d. ). Retrieved from http://www. slideshare. net/search/slideshow?searchfrom=header&q=stealth technology