DOWNLOAD PDF RADAR AND ANTENNA ENGINEERING

Transcription

1 Chapter 1 : Radar - Wikipedia Radar Antenna Engineering. Antenna is a structure which serves as a transition between wave propagating in free space, and the fluctuating voltages in the circuit to which it is connected. A constant phase shift over frequency has important applications as well, albeit in wideband pattern synthesis. An electronically scanned array is a brick, stick, tile, or tray construction. Brick and tray refers to a construction approach in which the RF circuitry is integrated perpendicular to the array plane. Tile, on the other hand, refers to a construction approach in which the RF circuitry is integrated on substrates parallel to the array plane. Stick refers to a construction approach in which the RF circuitry is connected to a line array in the array plane. The feed network is constrained corporate, series or space-fed. The grid is periodic rectangular, triangular or aperiodic thinned. The polarization of ground-based radar sensors is vertical, in order to reduce multipath Brewster angle. Radar sensors can also be polarimetric for all-weather applications. FMCW versus pulse-doppler[ edit ] The range and velocity of a target are detected through pulse delay ranging and the Doppler effect pulse-doppler, or through the frequency modulation FM ranging and range differentiation. The range resolution is limited by the instantaneous signal bandwidth of the radar sensor in both pulse-doppler and frequency modulated continuous wave FMCW radars. A drawback of half-duplex operation is the existence of a blind zone in the immediate vicinity of the radar sensor. Pulse-Doppler radar sensors are therefore more suited for long-range detection, while FMCW radar sensors are more suited for short-range detection. A monopulse feed network, as shown in Fig. Pulse compression derelates the pulse width and the instantaneous signal bandwidth, which are otherwise inversely related. The pulse width is related to the time-on-target, the signal to noise ratio SNR and the maximum range. The instantaneous signal bandwidth is related to the range resolution. Echoes originating from a radiated burst are transformed to the spectral domain using a discrete Fourier transform DFT. In the spectral domain, stationary clutter can be removed because it has a Doppler frequency shift which is different from the Doppler frequency shift of the moving target. The range and velocity of a target can be estimated with increased SNR due to coherent integration of echoes. In this case sensor in the transmitting antenna report back to the system the angular position of the scanning beam while the energy detecting ones are with the other antenna. A time synchronisation is crucial in interpreting the data as the receiver antenna is not moving. Monostatic radars have a spatially co-located transmitter and receiver. It this case, the emission has to be insulated from the reception sensors as the energy emitted is far greater than the returned one. Page 1

2 Chapter 2 : ROC RADAR ENGINEERING This course is designed for engineers, scientists, antenna engineering managers, project planners, and practicing antenna technicians. This course will be beneficial for those who need to know how the antenna affects the performance of a radar or communications system, how to select the materials used for antenna construction, how to analyze and design the electromagnetic performance of an. First experiments[ edit ] As early as, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In, Alexander Popov, a physics instructor at the Imperial Russian Navy school in Kronstadt, developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter. In, while testing this equipment for communicating between two ships in the Baltic Sea, he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. In, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He also got a British patent on September 23, [10] for a full radar system, that he called a telemobiloscope. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told the "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Across the Atlantic in, after placing a transmitter and receiver on opposite sides of the Potomac River, U. Hoyt Taylor and Leo C. Young discovered that ships passing through the beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory NRL observed similar fading effects from passing aircraft; this revelation led to a patent application [13] as well as a proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on the ocean liner Normandie in In total, only Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2, entered into service in June on Pe-2 fighters. More than Gneiss-2 stations were produced by the end of Full radar evolved as a pulsed system, and the first such elementary apparatus was demonstrated in December by the American Robert M. Page, working at the Naval Research Laboratory. Watson-Watt in Great Britain. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such a system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for the outbreak of World War II in This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft would always need to be in the air to respond quickly enough if enemy aircraft detection relied solely on the observations of ground-based individuals. Also vital was the " Dowding system " of reporting and coordination to make best use of the radar information during tests of early deployment of radar in and Given all required funding and development support, the team produced working radar systems in and began deployment. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. Radar in World War II A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared the technology with the U. Later, in, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. Applications[ edit ] Commercial marine radar antenna. The rotating antenna radiates a vertical fan-shaped Page 2

3 beam. The information provided by radar includes the bearing and range and therefore position of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: This evolved in the civilian field into applications for aircraft, ships, and roads. The first commercial device fitted to aircraft was a Bell Lab unit on some United Air Lines aircraft. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over a wide region and direct fighter aircraft towards targets. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. It has become the primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms, tornadoes, winter storms, precipitation types, etc. Police forces use radar guns to monitor vehicle speeds on the roads. Smaller radar systems are used to detect human movement. Examples are breathing pattern detection for sleep monitoring [32] and hand and finger gesture detection for computer interaction. Page 3

4 Chapter 3 : Wimpy Radar Antenna: Reinforced Tower Test, Analyze & Improve - Activity - TeachEngineerin Radar Systems Course 3 Antennas Part 2 1/1/ IEEE New Hampshire Section IEEE AES Society Antenna Functions and the Radar Equation â "Means for radiating or receiving radio waves"*. The model radar antenna must be attached to the tower for torsion tests only; it serves as both the means of applying the twisting moment, and it also has the pointer that is used to measure the angular deflection of the tower see Figure 3. Making the antenna model. Place the two foam insulation blocks end-to-end. Place the two wooden or metal rulers flat against the sides of the blocks. Slide the two foam insulation blocks apart so that each one lines up with the ends of the rulers; there should be exactly a 1-inch square hole between the two blocks at the center of the ruler. Holding everything in place, duct tape the rulers together on each side of this center hole but do not cover the hole. Then slide the top of a model tower into this square hole, making sure that it fits fairly snugly. If not, untape the rulers and readjust the position of the foam blocks. When you conduct the torsion test, you will use the c-clamp to firmly secure the antenna to the tower; the clamp will be placed right across the square hole in the middle of the antenna see torsion test procedure. The antenna tower to be tested will be placed in the square cut-out in the angle measuring plate and then clamped in the table top vise see Figure 4. Making the angle measuring plate. Find the center of the inch square foam core board plate using diagonal lines. Draw a line through the center, parallel to a side, running the entire length of the board. Align the protractor at the center of the line center of the board. Mark 5-degree increments around the protractor on the board. Draw straight lines that radiate from the center through the 5-degree marks, out to the edge of the board; label each line with its degree measure. Next draw and cut out a 1-inch square that is at the center of the board, and has its sides parallel with the outside edges of the foam core board. No materials may extend from the tower more than 2-inches in any direction. Build 4 models of Raytheoff radar antenna tower: Measure and cut 8 pieces of foam core board, 5 x 5-inches Cut a 1-inch square out of the middle of each foam core board square. Make a template on graph paper, like the one shown in Figure 5, and use it to mark the location of the cutout on each piece. Template for making foam core board foundation squares. Cut out 4 extruded foam insulation blocks, 1 x 1 x inch the teacher may provide 1 x 1 x 4-ft blocks that can be cut in fourths. To assemble the model, see Figure 6: Assembly of radar antenna tower models. Brainstorm ideas for redesigning the tower. In your teams, talk about and sketch several different ideas at least five for bracing and reinforcing the wimpy antenna tower before you are allowed to get your materials and build your designs. You may only use the materials provided to solve the problem. Plan to spend at least 20 minutes generating possible solutions. Select and build models of the two ideas that you believe to be the best tower designs. Using the wimpy models you assembled and the materials provided, build two identical models of each of your two best tower designs. One will be used for the bending test and the other one for the torsion test. Bending Test Procedure See Figure 7: Experimental setup for bending test. Stack a pile of books on each side of the antenna tower, and lay a strip of foam core board across the books so that it touches the tower exactly where the string loop is tied on. Use masking tape to attach the foam core board to the books and keep it from moving. This piece of foam board becomes the zero mark from which you measure the deflection of the tower when it bends. Three students are needed to run the test: Bending test data for design 1. Repeat the bending test for your other tower design, and record your results in Table 2. Then graph the results of both tests on Graph 1. Torsion Test Procedure See Figure 8: Experimental setup for torsion test top view. Place tower model into the angle measuring plate, and then into the table top vise so it sits flat against the vise. Clamp with just enough pressure to hold the tower from moving. Place the antenna two wooden rulers onto the top of the tower, and clamp it firmly in place using the small c-clamp. Take two 8-inch pieces of string and tie them into loops. Place one loop of string over each side of the antenna and tape them in place exactly 14 cm from the center of the tower; 14 cm is the moment arm for the twisting moment because these loops are where the spring scales will be inserted to apply the load. Use this pointer to measure the angular deflection of the tower when it is twisted. Make sure the pointer starts out pointing to zero degrees You need 4 students to run this test: Torsion test data for design 1. Two students load the tower together, trying to keep exactly the same force Page 4

5 on both sides of the antenna at all times. Stop every 2N 1N on each scale to record the angular deflection. Repeat the torsion test for your other tower design, and record your results in Table 4. Then graph the results from both tests on one graph on Graph 2. Now that torsion and bending tests have been completed for two designs, discuss with your group which features of each design helped give the tower stability. Which features could have been improved? Using what you learned, generate a third design. Build two identical models of this third design. Perform bending and torsion tests on this new design and complete Table 5 and Table 6. Graph the results of this test versus the first two designs on Graph 3 and Graph 4. Do you see an improvement over your first designs? Chapter 4 : Radar Engineering - G. S. N. Raju - Google Books Radar engineering details are technical details pertaining to the components of a radar and their ability to detect the return energy from moving scatterers â determining an object's position or obstruction in the environment. Chapter 5 : Radar Systems and Antennas â Communications Engineering The MIT Radiation Lab Series book on Radar Systems Engineering. Chapter 6 : Radar engineering details - Wikipedia As wireless technology continues to expand into nearly every area of our lives, gaining in-depth knowledge of antenna technologies such as radar, near-field, phased-array, far-field, and more will put you in high demand. Chapter 7 : blog.quintoapp.com: Antennas & Radar: Kindle Store Electronic Warfare and Radar Systems Engineering Handbook A Comprehensive Handbook for Electronic Warfare and Radar Systems Engineers Naval Air Warfare Center Weapons Division, Point Mugu, California. Chapter 8 : Radar Basics - Parabolic Antenna The radar mile is the time it takes for a radar pulse to travel one nautical mile, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1, m, then dividing this distance by the speed of light (,, m/s), and then multiplying the result by 2 yields a result of μs in duration. Chapter 9 : Welcome to ERS Antenna 65 Responses to Ground Penetrating Radar Surveys for Engineering Geophysics and Subsurface Utility Engineering 15 MHz GPR Antenna August 9, at am # What will be the penetration depth by 15 MHz Antenna. Page 5