Antennas -in 60 Minutes or Less Cynthia Furse

Antennas -in 60 Minutes or Less! Cynthia Furse Department of Electrical and Computer Engineering University of Utah cfurse@ece. utah. edu

Antennas 101 l l Size / current distribution Radiation Pattern (“far”fields) l l l Near Fields l l Directivity Gain Side Lobes Polarization Mutual Coupling Specific Absorption Rate (SAR) Input Impedance (matching) Link Budget

Dipole Antenna Current distribution From: http: //www. qth. com/antenna/dipole. gif, plot. gif

Radiation Pattern Direction of Maximum Dipole Radiation Direction of Maximum Isotripic. Radiation Pattern Of an ISOTROPIC Radiator (that doesn’t Exist) Directivity = Pmax dipole / Pmax Isotropic = 1. 67 Gain = Directivity * Efficiency

Why do we care about Gain? Link Budget

Half Power Beam Width (HPBW) 3 d. B (1/2 Power Point) Half Power Beam Width (HPBW)

Monopole Antenna Capacitive Load Monopole Helix Ground From: http: //www. letstalk. com//Images/5 -a. gif

Specific Absorption Rate (SAR) FCC (ANSI/IEEE) Regulation SAR (1 g average) <1. 6 W/kg

Cellular Telephones SAR Distribution in Adult - 835 MHz - Simplified Phone Model - l /4 antenna Pandit, Mc. Dermott, Lazzi, Furse, Gandhi, “Electrical Energy Absorption in the Human Head, ” presented at IEEE Visualization ‘ 96, S. F. , CA 1996

SAR Distributions - 835 MHz (adult, 10 year old, 5 year old) Adult 5 year old 10 year old From: Gandhi, Lazzi, Furse, IEEE Trans. MTT 44(10) 1996

Folded Dipole From: http: //www. qth. com/antenna/fdipole. gif

Monopole Antenna above Ground =Dipole Antenna Ground

MEANDER LINE ANTENNAS

RADIATION PATTERN OF MEANDER LINE ANTENNA

Microstrip Antenna (Slot of Same Size would give identical results From: http: // www. centurion. com

Genetic Algorithm l l N l l l Choose “Gene” Parameters Randomly create population “Survival of the Fittest” Gene “Crossover” and “Mutation” Statistically Optimal

Planar Inverted “F” Antenna (PIFA) From: “FDTD Analysis of PIFA diversity antennas on a hand-held transreceiver unit” by Michael A. Jensen and Yahya Rahmat-Samii

From: “Integrated Antennas for Hand-held Telephones with low Absorption’’ by Gert Frolund Rendersen, Jorgen Bach Andersen

PIFA Impedance Z = R + j. X |Reflection Coefficient| = (Zo – ZL)/(Zo+ZL) Zo=50 ohms R=50 ohms? Resonant Frequency X

|S 11| = |Reflection Coefficient Γ| (Less than half of the power is Reflected within this bandwidth) There will ALWAYS Be a higher harmonic Band. Must filter if unwanted. ½ Power Bandwidth

CAPACITIVELY LOADED PIFAs l l USUALLY LENGTH IS (L/4). IT REDUCES IT TO (L/8). From: “A capacitively loaded PIFA for compact mobile telephone Handsets’’ by Corbett R. Powell, Student Member IEEE, and R. D. Murch, Member IEEE

DUAL BAND PIFA 1

TRIPLE BAND PIFA

PIFA WITH MEANDER LINES

DIVERSITY ANTENNAS (ie. MIMO)

BPFA

BPFA RADIATION PATTERN

COMPARISON of DTSA and MONOPOLE SAR Distribution

Loop Antenna From: http: //www. downeastmicrowave. com/graphics/kbloop. gif

Reflector (Dish) Antenna From: http: //www. dssdirectv. com/chanmas 1. jpg

Arecibo Observatory -Puerto Rico From: http: //www. naic. edu/about/photos/aoviews/tescop. jpg

Arecibo Observatory From: http: //www. naic. edu/about/photos/aoviews/wideao. jpg

GPS Antennas From: http: //www. lowe. co. uk/gpsant. jpg

Horn Antennas From: http: //www. tmo. hp. com/tmo/datasheets/Images/img-HP 11966 J-1 lg. gif From: http: //www. afcsat. com/CH 14_MOT 2. jpg

Antenna Arrays Two Elements -- Pattern adds constructively or destructively Array interaction is necsessary. From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/ant/pat 1. gif

Antenna Arrays More Elements: Higher Directivity Sidelobes From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/ant/pat 2. gif

Scanning Antenna Array Changing the phases on the element feeds can make a scanning array. From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/ant/pat 3. gif

Arrays From: http: //www. qth. com/antenna/tiny 2 rl. gif From: http: //cust. iamerica. net/dwhowell/yagimax. jpg

Polarization E E E

HAARP Observatory HAARP (High frequency Active Auroral Research Program) is to be a major Arctic facility for upper atmospheric and solar-terrestrial research. HAARP is being built on a Do. D-owned site near Gakona, Alaska. From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/ohd. jpg

HAARP Antenna Array Crossed Dipoles The HF antenna system to be used for Active Ionospheric Research at the HAARP site will assist other facility instruments in the study the overhead ionosphere. As a result, it too has been designed to optimize or restrict the transmission pattern to lie within a narrow overhead region. To achieve this desirable antenna pattern, the HAARP system uses an "array" of individual antenna elements. The HAARP antenna array is similar or identical to many other types of directive antenna types in use for both military and civilian applications including air traffic control radar systems, long range surveillance systems, steerable communication systems and navigation systems. From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/twr/pan 2. jpg

HAARP -- Feed Sytem From: http: //server 5550. itd. nrl. navy. mil/projects/ HAARP/images/ant/tpile. jpg

HAARP -- Matching Networks From: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/images/ant/amu. jpg

Corner Reflector Antenna Reflector acts like A “mirror” and produces Virtual antennas. From: http: //www. northcountryradio. com/crfigs. htm

Anything Radiates … Fan-tenna From: http: //www. qth. com/antenna/fanfull. gif

So. . Where do we go from here with MIMO? l Define Specifications (easier said than done) l l l l Maximum size Frequency and bandwidth What does the “output” of the antenna set need to be to achieve optimal communication? What antenna parameters affect that? What antenna is optimal? Parametric Studies GA or direct optimization

Antenna References on the Web General: http: //www. ee. surrey. ac. uk/Personal/D. Jefferies/antennas. html GPS Antennas Lowe Industries : http: //www. lowe. co. uk/antrev 2. html Antenna Calibration: http: //gracie. grdl. noaa. gov/GRD/GPS/Projects/ANTCAL/index. shtml Ham: North Country Radio: http: //www. northcountryradio. com/techtips. htm Antenna Elmer: http: //www. qth. com/antenna. htm HAARP Observatory: http: //server 5550. itd. nrl. navy. mil/projects/HAARP/ant 3. html Arecibo Obervatory: http: //www. naic. edu/aboutao. htm