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Home , Adcock antenna, Antenna array, Phased array, Slot antenna, Wullenweber

Array Developments: A Perspective on the Past, Present and Future

Randy L. Haupt1 and Yahya Rahmat-Samii2

1Department of Electrical Engineering and Computer Science, Colorado School of Mines, Golden, CO 80401 USA E-mail: [email protected]

2Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, CA 90095 USA E-mail: [email protected]

Abstract

This paper presents a historical development of phased-array antennas as viewed by the authors. Arrays are another approach to high-gain antennas as contrasted with reflector antennas. They originated a little over 100 years ago and received little attention at first. WWII elevated their importance through use in air defense. Since then, the development of computers and solid-state devices has made arrays a very valuable tool in - systems. and defense applications will continue to push the state of the art for many years.

Keywords: Antenna; arrays; ; history; phased arrays;

1. Introduction Moreover, mechanical steering might be too slow to meet some of the demands on fast-moving platforms such as airplanes. arge antennas collect relatively large amounts of elec- The array, particularly the , makes many per- tromagnetic energy much as large buckets collect large L formance promises but for a price. Some of the unique features amounts of rain. In our companion paper, we described reflec- of a phased-array antenna include: tor antennas (large buckets). Using many small buckets to collect rain corresponds to using small antennas in an array to collect a large amount of electromagnetic energy. As with an- 1. fast wide-angle scanning without moving the antenna; tennas, a large bucket has the advantage of collecting lots of 2. adaptive beamforming; water in one location, whereas using many small buckets has the advantage of being easy to rearrange and move the small 3. graceful degradation in performance over time; buckets in order to better collect the rain. This analogy be- tween buckets and antennas is interesting but limited, because 4. distributed aperture; electromagnetic waves have whereas rain does not. 5. multiple beams; Large antennas create the high gain needed to boost the received/transmitted signal for a communications or radar sys- 6. potential for low radar cross section. tem. Today, reflectors and arrays compete for large aperture jobs in many types of systems. In general, the reflector is rela- Comparatively, reflectors are blessed with these advantages: tively inexpensive, that is why it is the antenna of choice for commercial activities, such as satellite TV. If the reflector must 1. high G/T; be moved in order to locate or track a signal, then the gimbals, servomotors, and other mechanical parts become a reliability 2. wide bandwidth; and maintenance issue that significantly increases lifecycle cost. 3. relatively low cost.

Digital Object Identifier 10.1109/MAP.2015.2397154 The competition between the better antennas for the job will con- Date of publication: 26 February 2015 tinue with the cost/performance issues decided by the mission

86 1045-9243/15/$26.00 © 2015 IEEE IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 and budget. Clearly, hybridization of reflectors and arrays pro- of the 0 phase signals at A and B. They discovered that the vides enhanced opportunity for more sophisticated and high- array radiated a cardioid pattern. Braun was the first to use phase performance antenna systems. to collimate (steer) the main beam. Maybe we can say that he is the inventor of the phased array. This paper presents the historical development of array antennas. Reflectors have a rich history in optics that started The early arrays were physically large but electrically thousands of years ago. Arrays, on the other hand, are only a small. Thus, an array of only a few elements required extensive little more than 100 years old, whereas phased arrays are only real estate. In 1917, Frank Adcock designed a direction-finding a little more than 70 years old. The next section starts around array (see Figure 2) that consists of four uniformly weighted el- the turn of the 20th century and continues up to WWII. WWII ements placed at the four corners of a square whose sides are (see Section 3) motivated the development of high-gain anten- much less than half of a wavelength [6]. The antennas on one nas for defensive reasons. Section 3 continues with develop- diagonal are out of phase with the antennas on the other diag- ments after WWII up to the computer age. Section 4 describes onal. Sir Watson-Watt developed the mathematics to find the the impact of computers on array design and control. Semicon- elevation and azimuth of a source incident on an Adcock array ductor technology led to the development of very sophisticated [7]. Adcock arrays are still popular today. The main purpose of solid-state arrays described in Section 5. Finally, Section 6 looks the first arrays was direction finding. to the future. Our account of history is what we have learned through research and experience. The authors decided to collabo- The magnetron was first developed in 1920 [8]. At first, it rate on two historical papers based on presentations they made only worked at low . By 1940, however, the British at the IEEE CLASTECH Symposium and Exhibition on Anten- had it working at high power above 1 GHz. This development nas and Technology, October 2011, Los Angeles, CA. led to higher resolution antennas and on aircraft, hence This paper summarizes the presentation made by Randy Haupt: electrically larger antenna arrays. “Phased array antenna design yesterday and today.” A compan- ion paper covers the history of reflector antennas. Due to lim- Harold Friis was the dominant array researcher from the ited space and our limited knowledge, we apologize to those mid-1920s to the mid-1930s. Friis presented the theory behind whose important work has been omitted. the antenna pattern for a two-element array of loop antennas and experimental results that validated his theory [9]. Friis sub- sequently designed a multiple-unit steerable antenna (MUSA) [10], which employed an array of rhombics and was altered for 2. Early Array Developments: 1899–1937 optimum reception of shortwave signals (see Figure 3). In 1927, J. S. Stone received a patent for the binomial amplitude taper, The first was built over 100 years ago [1]. In which theoretically eliminates array sidelobes [11]. Mutual cou- order to increase the of a single monopole, Brown pling between elements in an array was recognized to be very used two vertical antennas separated by half a wavelength and important in array design at a very early date [12]. fed them out of phase [2]. He found that the directivity was greatest in the plane of the antennas. The first array radiated at endfire. De Forest also noted an increase in gain due to ar- raying two vertical antennas [3]. He and several others used 3. Arrays in WWII: 1937–1945 an array to locate the source of a transmitting station. Shortly after the turn of the century, Marconi performed several ex- WWII motivated countries to tremendously accelerate the periments involving multiple antennas to enhance the gain in development of radars that detect aircraft and ships at a great certain directions [4]. Some even credit him with the invention distance. The radars needed to operate at a in of the antenna array, even though other lesser known experi- order to resolve targets, but the upper frequency was limited, menters preceded him. Nobel Prize winner Ferdinand Braun because at that time had insufficient power. The (also given credit as the inventor of the antenna array) placed available frequencies required huge antennas that could not be three monopoles in a triangle, as shown in Figure 1 [5]. The moved. Britain developed the bistatic (CH) radar signal at antenna C has a 100 phase and twice the amplitude for air defense in the late 1930s [13]. The 23.1-MHz transmit

Figure 1. Braun’s three-element array [5].

IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 87 Figure 2. Four-element direction-finding array from Adcock’s patent [6]. Figure 5. SCR-270 antenna array (photo taken by R. Haupt at the National Electronics Museum).

As the war progressed in Europe, better radars were needed. A new US-developed long-range radar called the SCR-270 (Figure 5) was available in Hawaii and detected the Japanese for- mation attacking Pearl Harbor. Unlike CH, it could be mechani- cally rotated in azimuth 360 in order to steer the beam and operated at a much higher frequency. The SCR-270 had four rows of eight horizontal dipoles and operates at 110 MHz [15]. This frequency is much higher than CH and allowed for much higher gain and resolution for detecting aircraft as well as the ability to mechanically rotate the much smaller higher frequency antenna.

In 1942, Bell Labs built the X-band Mark 8 surface fire control radar that had an array of 14 3 polyrod antennas (see Figure 6) [16]. It used mechanically switched rotary phase shifters attached to the columns for azimuth scanning. Figure 3. MUSA, a six-element rhombic array, with one of This was the first use of the polyrod antenna in an array and the phase-shifting condensers in the lower left [10] Ó1937. the first microwave phased array. array had towers that were about 107 m tall and spaced about Schelkunoff developed a general approach to the analysis 55 m apart (see Figure 4). These towers held eight horizontal and synthesis of linear arrays in 1943 [18]. His array polynomial dipoles for the main array and a four-dipole array that covered and associated unit circle forms the basis of array analysis and low angles for close targets. In April 1937, CH was able to synthesis in the years to come. detect aircraft at a distance of 160 km. Wooden towers for the receiving arrays were about 76 m tall and initially had three In 1944, the Germans built the Mammut 1 radar to detect receiving antennas in the form of two dipoles arranged in a aircraft. The 10 m 25 m eight-element array (see Figure 7) cross configuration. scanned 50 in azimuth using helical phase shifters [19]. In the same year, Dr. Hans Rindfleisch of Germany built the first array in Skisby, Denmark [20]. It had 40 verti- cal radiator elements, placed on a 120-m-diameter circle with 40 reflecting elements installed behind the radiator elements

Figure 4. CH array [14] (imperial war museums non- Figure 6. Mark 8 planar phased array with polyrod elements commercial license). [17] Ó2010 (courtesy of National Electronics Museum).

88 IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 a Chebyshev polynomial in order to get peak sidelobe levels that were equal and at a specified level below the peak of the main beam. A few years later, Taylor developed sidelobe ta- pers with predetermined sidelobes for linear [24] and circular planar arrays [25].

In the mid 1950s, digital computers became powerful en- ough to control a phased-array radar and analyze the returns. In the late 1950s, Hughes Aircraft Company developed a de- sign for a planar array that scans in azimuth and elevation [26]. Their resulting design had two stationary planar arrays on each of the four sides of a ship’s superstructure (see Figure 9) [27]. The first radar (AN/SPS-32) was a 2-D long-range air search Figure 7. Mammut 1 array (courtesy of U.S. National Archives radar that displayed the location of airplanes on a scope read by and Records Administration). a radar operator. The operator fed these targets to a computer that controlled the beam of a 3-D search radar (AN/SPS-33) around a circle having a diameter of 112.5 m (see Figure 8). that was frequency scanned in elevation and phase scanned in Wullenwever was the WWII German cover name for the an- bearing. The two arrays were called billboard radars due to tenna: The Germans actually called it Wullenwever. Americans the large size of the arrays (250 200 and 400 200). could not pronounce it, so they changed the name. After the war, the Soviets built many of these arrays and even tracked In late 1956, GE’s Advanced Electronics Center invented Sputnik with them. The United States got interested later and the sidelobe canceler [28]. They transmitted a strong jamming ended up building many of them for the US Navy. An example signal in the direction of a sidelobe of the large main antenna can be seen on Google Maps by entering the coordinates 48.951, A small auxiliary omniantenna with a gain about the same as 54.525 for Gander, Newfoundland, Canada. the gain of the main antenna sidelobes sat beside and pointed in the same direction as the main antenna. At video frequen- Louis Alvarez developed a -fed linear dipole cies, they subtracted the output of the omniantenna from the array for three radar applications at the MIT Radiation Lab jamming in the main antenna using automatic gain control to from 1940 to 1943: 1) ground-controlled approach; 2) micro- minimize the canceled residue. Since the auxiliary gain was about wave early warning; and 3) Eagle precision bombing [22]. The 30 dB less than the gain of the main antenna, the first two were ground based, so the array fed a parabolic re- desired target signal was not canceled. Howells and Applebaum flector to increase the gain. Alvarez wanted to use a slotted recognized the potential of this technique if it could be made to waveguide, but his idea was discarded due to the difficulty of work at RF frequencies. They invented the correlation loop and machining the slots. Instead, dipoles were placed at equally applied it to antenna arrays. This was the first adaptive antenna spaced holes in the waveguide. The fields were coupled using and used the Howells–Applebaum adaptive loop. These results probes. Placing the holes so that the elements were fed in phase were not published until the 1970s. Later in the 1960s, Widrow resulted in unacceptable grating lobes due to the large element developed a very similar approach using the least mean squares spacing. Alvarez cleverly halved the element spacing, so the (LMS) algorithm [29]. The two approaches differ in that the signals at adjacent elements were 180 out of phase. He then Howells–Applebaum algorithm needs to know the beam steer- twisted the probes of every other dipole by 180, so all the el- ing vector, whereas the LMS algorithm needs a facsimile of the ements have the same phase. No wonder he won the Nobel received signal. Consequently, the Howells–Applebaum approach Prize! Beam scanning resulted from changing the frequency. The resonant frequency of the waveguide was changed by in- creasing/decreasing the width of the waveguide.

4. Arrays in the Computer Age: 1946–1964

After the war, Dolph published his important paper on controlling the sidelobes/beamwidth of an array by amplitude tapering [23]. He mapped the array factor of a linear array to

Figure 9. Long Beach launched in 1961 with the AN/SPS-32 Figure 8. Wullenweber array in Skisby, Denmark [21]. and AN/SPS-33 radar antennas (courtesy of US Navy).

IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 89 points that forms simultaneous multiple beams (see Figure 11). The is a hardware version of the fast Fourier transform that has 2M inputs and 2M orthogonal beams [32].

A very important development in 1960 was the Wilkinson power divider/combiner (see Figure 12) [33]. These combiners/ dividers are widely used in arrays, because they are reciprocal, have all ports matched, and have good isolation between ports.

The following year, Sharp found that triangular spacing in a planar array (see Figure 13) not only delays the appear- ance of grating lobes but allows larger elements in the array [34]. An array with triangular spacing has 86.6% fewer ele- Figure 10. Nike AJAX MPA-4 zoned waveguide lens (Photo ments than the same-sized array with a square lattice. taken by R. Haupt at the National Electronics Museum).

5. Solid-State Arrays: 1964–Present

The development of semiconductor electronics in the 1960s had a huge impact on phased-array technology. The Molecular Electronics for Radar Applications (MERA) Program launched the development of the monolithic microwave integrated circuit (MMIC) T/R module in 1964 [35]. The module was fabricated on high-density alumina and high-resistivity silicon, using thin- film techniques (see Figure 14). Circuits are located on both sides of the module. Each module in the array transmitted a peak power of 0.6 W at 9.0 GHz and had a four-bit phase shifter. The module was 7.1 2.5 0.8 cm, and it weighed 27 g. During this same period, the AN/FPS-85 UHF (450 MHz) radar (see Figure 15) was built to detect space objects [36]. Separate transmit and receive arrays were built rather than use diplexers and a single aperture. A unique idea for this array was to place vacuum tube transmitters at each element rather thanuseonelargesourceandadividing network. An engineer Figure 11. Original Rotman lens concept [31] Ó1963. noticed that the radiating elements looked like a toilet bowl float, and subsequently, significant savings resulted by hiring a toilet bowl manufacturer to build the elements! Construction works best for radar, whereas the LMS approach works best ended in 1965, but it burned down because the power for communications systems. ignited the plastic insulation in the coaxial cables. The prefire radar used analog phase shifters and vacuum tube receivers. In the 1950s, lens antennas became popular for applications The postfire radar used diode phase shifters and transistor requiring multiple beams. The antenna for the Nike AJAX MPA-4 receiversVquite a change in a short time! radar was a zoned waveguide lens (see Figure 10) [30]. This was the first implementation of monopulse. In 1963, the Rotman In 1969, the AN/APQ-140 radar used the Reflected Array lens [31] debuted. It is a type of bootlace lens with three focal (RARF) manufactured by Raytheon [37].

Figure 12. Wilkinson power divider/combiner [33] Ó1960.

90 IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 Figure 13. Example of triangular spacing [17] Ó2010 (courtesy of Ball Aerospace & Technologies Corporation).

Ó Figure 16 shows the reflectarray surface with 3500 passive phase- Figure 16. RARF [17] 2010 (courtesy of National Elec- shifting modules that scan 60 in elevation and azimuth. This tronics Museum). array replaced the reflector antenna in the nose of airplanes. In the 1970s, two very important array elements opened up many new avenues for phased arrays. The microstrip patch was a narrowband element first proposed by Deschamps in 1953 [38]. The patch did not revolutionize array design until Munson figured out how to make practical use of them in 1972 [39].

Figure 14. MERA array with module and close-up of elements [17] Ó2010 (courtesy of National Electronics Museum). Figure 17. Large planar microstrip arrays can be made from self-similar parts [17] Ó2010.

Figure 18. Conformal Airlink antenna for satellite com- Figure 15. AN/FPS-85 UHF (450 MHz) radar (courtesy of munications from an airplane [17] Ó2010 (courtesy of Ball USAF). Aerospace & Technologies Corporation).

IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 91 Figure 19. First and array [40] Ó1979.

Figure 20. AWACS array [17] Ó2010 (courtesy of USAF and National Electronics Museum).

Patches are very thin and readily conform to a curved surface. In addition, the patches can be mass produced using relatively cheap circuit board technology, and large arrays can be as- sembled (see Figure 17). Patches inspired the idea of making arrays conform to the shape of a curved surface rather than being limited to a planar surface. AIRLINK is an airborne sat- ellite conformal array system (Figure 18) for in-flight telephone, fax, and data transmission that operates at 1530–1559 MHz on receive and 1626.5–1660.5 MHz on transmit. This conformal array is thin and is a panel on the body of an airplane. The second important array element is the tapered or Vivaldi antenna [40]. It is a flared slot line that is a very broad band and has a fairly constant beamwidth over the bandwidth (see Figure 19).

The Airborne Warning and Control System (AWACS) S-band planar array appeared on the scene in 1976 with 4000 Figure 21. EAR [17] Ó2010 (courtesy of National Elec- slots (see Figure 20) [41]. This array rotates in azimuth and is tronics Museum).

92 IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 operates from 1215 to 1400 MHz and has a 29-m phased-array antenna with 136 azimuth coverage.

So far, we have only described how military needs have driven the development of phased arrays. Radio astronomy has pushed the frontiers of arrays as well. The is a Y-shaped that has 27, 25-m reflector antennas [43]. The elements can be configured in four ways with a maxi- mum width of 36 km. This array came online in 1980. It com- bines both large reflector antennas as elements with the array concept in order to meet the huge resolution requirements in radio astronomy.

Figure 22. (courtesy of DefenseImagery.mil). The AN/APG-77 Advanced Tactical Fighter (ATF) ra- dar used a GaAs MMIC T/R module. Its 1500 elements fit in- side the nose cone of a USAF F-22A [17]. The module in Figure 23 shows a dramatic increase in complexity from the MERA module in 1964 to this module in 1987.

The sea-based X-band (SBX) radar began operation in 2006, having 22 000 T/R modules, radiates 12 MW, and tracks and identifies long-range missiles (see Figure 24) [44]. The radar is mounted on a modified, self-propelled, and semisubmersible oil platform. Its 284 m2 active aperture covers 360 in azimuth and almost 90 in elevation.

6. Arrays of the Future

One of the holy grails of antenna arrays is digital beam- Ó Figure 23. AN/APG-77 ATF radar [17] 2010 (courtesy forming (DBF) [45]. DBF places analog-to-digital converters at of Northrop Grumman and available at the National the elements of an array (Figure 25). Because the signals be- Electronics Museum). come computer data at the elements, all the beamforming is done in software instead of hardware. As a result, adaptive nul- electronically scanned in elevation using 28 ferrite phase shifters. ling, generating multiple beams, lowering sidelobes, and many The amazing achievement of the designers is the sidelobe other signal processing type techniques can be implemented. This level: average sidelobe level was 45 dB (bottom of Figure 20). approach is very expensive and requires real-time calibration; hence, it has been limited to relatively small arrays. A transmit ap- Electronically Agile Radar (EAR) was developed in the proach starts with a signal generator that sends signals to each ele- 1970s for airborne radar systems. It had 1818 circular wave- ment through a digital-to-analog converter and transmitter. guide elements connected to phase shifters that scanned the beam (see Figure 21). Moreover, in the 1970s, Raytheon built a Radio astronomy is pushing the state of the art of phased series of very large phased arrays for tracking missiles. The first arrays with the Atacama Large Millimeter/submillimeter Array was the AN/FPS-108 COBRA DANE (see Figure 22). It (ALMA) [46]. It consists of 80 antennas in the Chilean Andes

Figure 24. SBX radar [17] Ó2010 (Courtesy of Missile Defense Agency History Office).

IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 93 Figure 25. Transmit and receive digital beamforming.

at 5000 m above sea level [18]. This radio telescope has 66 12- and 7-m parabolic dishes that operate from 31.25 to 950 GHz. Figure 27. Portion of 10-m-diameter spherical array ap- fi Array con gurations from 250 m to 15 km will be possible. proximated by planar subarrays [17] Ó2010 (courtesy of The ALMA antennas are movable between prebuilt stationary Ball Aerospace & Technologies Corporation). flat concrete slabs (see Figure 26), and the beams are formed in real time using optical fiber feeds.

Although linear and planar array technology is well estab- side of a multilayer printed circuit board (PCB) and the com- lished, the need for conformal arrays pushes the boundaries of ponents on the other side. Affordable manufacturing of arrays fi array technology. Spherical arrays are dif cult to build but are on single PCBs is vital to their future. far superior to planar arrays for hemispherical coverage. Spheri- cal arrays have lower , mismatch, and gain losses Advances in semiconductor technology is critical to fi with scan than planar arrays. Figure 27 shows a ve-panel por- making T/R modules more efficient, smaller, and of higher fl tion of a 10-m diameter spherical array approximated by at power. Gallium nitride is making important inroads into new panels. The center pentagonal panel has ten hexagonal sub- T/R module technology. New ideas in cooling techniques are fi arrays, whereas the surrounding ve hexagonal panels have important for high-power transmit arrays. Current research in 21 hexagonal subarrays [17]. phased arrays also include topics such as broadband arrays, cheaper T/R modules, multiple-input–multiple-output arrays, One of the approaches to reducing the cost of phased terahertz arrays, reconfigurable arrays, distributed arrays, and arrays is to place the entire array on a single multilayer cir- much more. Large wide-scanning wide-bandwidth arrays re- cuit board. Current technology allows planar arrays through quire time delay units, which means “phased arrays” become the X-band. Figure 28 shows that typical components of an active phased array easily fit within the unit cell at the X-band. The size of these components does not dramatically change with frequency due to packaging, so they do not fit within the unit cell of the array at Ku, K, Ka, and Q bands (see Figure 28). Figure 29 is an example of an array with the elements on one

Figure 28. Components (yellow square blocks) relative to the unit cell (red solid square box) at different frequency bands. The components have the same size, but the unit cell Figure 26. ALMA [47] Ó2013. decreases as the frequency increases.

94 IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 Figure 29. Front (antenna elements) and back (components) of a pla- nar antenna array Ó2010 (courtesy of Ball Aerospace & Technolo- gies Corporation).

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IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015 95 Randy L. Haupt received the B.S.E.E. degree several national and international symposia. He was a member of the UCLA from the United StatesAirForceAcademy Graduate council for three years. He was the Chair of USNC-URSI during (USAF Academy), Colorado Springs, CO, USA, 2009–2011. For his contributions, he has received numerous NASA and JPL in 1978; the M.S. degree in engineering man- Certificates of Recognition. In 1984, he received the Henry Booker Award from agement from Western New England College, URSI, which is given triennially to the most outstanding young radio scientist Springfield, MA, USA, in 1982; the M.S.E.E. in North America. Since 1987, he has been designated every three years as one degree from Northeastern University, Boston, of the Academy of Science’s Research Council Representatives to the URSI MA, in 1983; and the Ph.D. degree in electrical General Assemblies held in various parts of the world. He was also an invited engineering from The University of Michigan, speaker to address the URSI 75th anniversary in Belgium. In 1992 and 1995, he Ann Arbor, MI, USA, in 1987. received the Best Application Paper Prize Award (Wheeler Award) for papers He is a Professor and the Head of the Depart- published in 1991 and 1993 IEEE TRANSACTIONS ON ANTENNAS AND PROPA- ment of Electrical Engineering and Computer GATION. In 1999, he received the University of Illinois ECE Distinguished Science, Colorado School of Mines, Golden, Alumni Award. In 2000, he received the IEEE Third Millennium Medal and the CO. He was an RF Staff Consultant with Ball Aerospace & Technologies Cor- AMTA Distinguished Achievement Award. In 2001, he received an Honorary poration; a Senior Scientist and the Department Head with the Pennsylvania Doctorate in applied physics from the University of Santiago de Compostela, State University Applied Research Laboratory, College Park, PA, USA; a Pro- Santiago de Compostela, Spain. In 2001, he became a Foreign Member of the fessor and the Department Head of Electrical and Computer Engineering with Royal Flemish Academy of Belgium for Science and the Arts. In 2002, he re- Utah State University, Logan, UT, USA; a Professor and Chair of Electrical ceived the Technical Excellence Award from JPL. He received the 2005 URSI Engineering with the University of Nevada Reno, Reno, NV, USA; and a Pro- Booker Gold Medal presented at the URSI General Assembly. He was a recipi- fessor of electrical engineering with the USAF Academy. He was a Project Engi- ent of the 2007 Chen-To Tai Distinguished Educator Award of the IEEE Anten- neer for the OTH-B radar and a Research Antenna Engineer for the Rome Air nas and Propagation Society. In 2008, he was elected to membership in the US Development Center early in his career. He is a coauthor of the books Practical NAE. In 2009, he was selected to receive the IEEE Antennas and Propagation Genetic Algorithms (2nd edition, John Wiley & Sons, 2004), Genetic Algo- Society highest award, Distinguished Achievement Award, for his outstanding rithms in Electromagnetics (John Wiley & Sons, 2007), and Introduction to career contributions. He was a recipient of the 2010 UCLA School of Engineer- Adaptive Antennas (SciTech, 2010) and an author of Antenna Arrays a Compu- ing Lockheed Martin Excellence in Teaching Award and the 2011 UCLA Dis- tation Approach (John Wiley & Sons, 2010) and Timed Arrays (John Wiley & tinguished Teaching Award. In 2012, he was elected as a Fellow of the Applied Sons, 2015). Computational Electromagnetics Society. He is the designer of the IEEE AP-S Dr. Haupt is a Fellow of the IEEE and Applied Computational Electromag- logo, which is displayed on all IEEE AP-S publications. netics Society.

Yahya Rahmat-Samii (S’73–M’75–SM’79– F’85) is a Distinguished Professor, holder of the Northrop Grumman Chair in Electro- magnetics, and past Chairman of the Elec- trical Engineering Department, University of California, Los Angeles (UCLA), Los Angeles, CA, USA. He was a Senior Research Scientist with the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL), California Institute of Tech- nology, Pasadena, CA, prior to joining UCLA in 1989. In the summer of 1986, he was a Guest Professor with the Technical University of Denmark, Copenhagen, Denmark. He has also been a consultant to numer- ous aerospace and wireless companies. He has been an Editor and a Guest Edi- tor of numerous technical journals and books. He has authored and coauthored over 950 technical journal and conference papers and has written 35 book chapters. He is a coauthor of “Electromagnetic Band Gap Structures in Antenna Engineering” (New York: Cambridge, 2009), “Implanted Antennas in Medical Wireless Communications” (Morgan & Claypool Publishers, 2006), “Elec- tromagnetic Optimization by Genetic Algorithms” (New York: Wiley, 1999), and “Impedance Boundary Conditions in Electromagnetics” (New York: Taylor & Francis, 1995). He has received several patents. He has had pioneering research contributions in diverse areas of electromagnetics, antennas, measurement and diagnostics techniques, numerical and asymptotic methods, satellite and per- sonal communications, human/antenna interactions, radio frequency identifica- tion and implanted antennas in medical applications, frequency-selective surfaces, electromagnetic bandgap structures, applications of the genetic algo- rithms, and particle swarm optimization (http://www. antlab.ee.ucla.edu/). Dr. Rahmat-Samii is a member of the US National Academy of Engineering (NAE) and a winner of the 2011 IEEE Electromagnetics Award. He is a Fellow of the Institute of Advances in Engineering and a member of Commissions A, B, J, and K of USNC-URSI, the Techniques Association (AMTA), Sigma Xi, Eta Kappa Nu, and the Electromagnetics Academy. He was the Vice President and President of the IEEE Antennas and Propagation Society in 1994 and 1995, respectively. He was appointed an IEEE AP-S Dis- tinguished Lecturer and presented lectures internationally. He was a member of the Strategic Planning and Review Committee of the IEEE. He was the IEEE AP-S Los Angeles Chapter Chairman (1987–1989); his Chapter won the Best Chapter Award in two consecutive years. He is listed in Who’s Who in America, Who’s Who in Frontiers of Science and Technology, and Who’s Who in Engi- neering. He has been the plenary and millennium session speaker at numerous national and international symposia. He has been the organizer and presenter of many successful short courses worldwide. He was the Director and Vice Presi- dent of AMTA for three years. He has been a Chairman and Cochairman of

96 IEEE Antennas and Propagation Magazine, Vol. 57, No. 1, February 2015