Antennas -- in 60 Minutes or Less! Cynthia Furse Department of Electrical and Computer Engineering University of Utah

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

Dipole Antenna From: Current distribution

Radiation Pattern Of an ISOTROPIC Radiator (that doesn’t Exist) Direction of Maximum Dipole Radiation Direction of Maximum IsotripicRadiation Directivity = Pmax dipole / Pmax Isotropic = 1.67 Gain = Directivity * Efficiency

Why do we care about Gain? Link Budget

Half Power Beam Width (HPBW) 3dB (1/2 Power Point) Half Power Beam Width (HPBW)

Monopole Antenna From: Capacitive Load Helix Monopole Ground

Specific Absorption Rate (SAR) FCC (ANSI/IEEE) Regulation SAR (1g average) <1.6 W/kg

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

SAR Distributions 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:

Monopole Antenna above Ground =Dipole Antenna Ground

MEANDER LINE ANTENNAS

RADIATION PATTERN OF MEANDER LINE ANTENNA

From: Microstrip Antenna (Slot of Same Size would give identical results

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

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 + jX Resonant Frequency R=50 ohms? X |Reflection Coefficient| = (Zo – ZL)/(Zo+ZL) Zo=50 ohms

½ Power Bandwidth |S11| = |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.

CAPACITIVELY LOADED PIFAs USUALLY LENGTH IS (L/4). USUALLY LENGTH IS (L/4). IT REDUCES IT TO (L/8). 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:

Reflector (Dish) Antenna From:

Arecibo Observatory -- Puerto Rico From:

Arecibo Observatory From:

GPS Antennas From:

Horn Antennas From: From:

Antenna Arrays Two Elements -- Pattern adds constructively or destructively Array interaction is necsessary. From:

Antenna Arrays More Elements: Higher Directivity Sidelobes From:

Scanning Antenna Array Changing the phases on the element feeds can make a scanning array. From:

Arrays From: From:

Polarization E E E

HAARP Observatory From: 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 DoD-owned site near Gakona, Alaska.

HAARP Antenna Array Crossed Dipoles From: 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.

HAARP -- Feed Sytem From: HAARP/images/ant/tpile.jpg

HAARP -- Matching Networks From:

Corner Reflector Antenna From: Reflector acts like A “mirror” and produces Virtual antennas.

Anything Radiates … Fan-tenna From:

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

Antenna References on the Web General: GPS Antennas Lowe Industries : Antenna Calibration: Ham: North Country Radio: Antenna Elmer: HAARP Observatory: Arecibo Obervatory: