Progress Report 9/27/13

Yagi Uda AntennaMark AsmuthKenneth MorganChristopher PayneOutlineDescriptionHistoryTheory of OperationDesign / Optimization / ResultsRecent DevelopmentsClosing RemarksBackgroundDirectional antenna (beam antenna)Linear array of parallel dipoleOne reflector in rear (longer than feed)One driven elementOne of more directors in Tx / Rx directionLow Impedance and narrow BWReconfigurable operationElectrical breaks on elementsExtends functionalityCommon UsesDirectional communicationAmateur radio on HF / VHF / UHF bandsRadio and television broadcasts

Reflector elementDriven elementDirectorsMain Lobe DirectionReflector typically 5% longer than feed3History - InventorsHidetsugu YagiJan. 1886 Jan. 1976Studied in Japan, England, America, and GermanyProfessor at Tohoku Imperial Univ.Published first English reference on antenna in 1928Awarded Japans Order of Cultural Merit in 1956

Shintaro UdaJun. 1896 Aug. 1976Studied in Japan and AmericaAssistant of Yagi (graduate student at time of publication)Invented Yagi - Uda antenna in 1926Published report with Yagi on wave projector antenna in Japanese publication

History Yagi Uda AntennaMotivated by need for better communication between islands and shipsPoint-to-point radio communication benefit from directive antennasFocus on short wave communication with directive antennasPatented by Yagi and Uda in 1926US patent issued in 1932 assigned to Radio Corporation of AmericaUda visits US in 1951 and astonished at ubiquity of Yagi-Uda antennas for home television receptionPoint-to-point commslower tx powerless interference from other stationsshort wavelengthonset of high freq sources (maganetrons)low cost, rugged5History World War IIExtensively used for airborne radarJapanese radar engineers unaware of design until late in warJapanese military officials aware of design after Battle of SingaporeCaptured notes from British radar technicianIntelligence officers did not recognize Yagi as Japanese nameBritish technician acknowledge Yagi as Japanese professorYagi express frustration over poor cooperation between military services and civilian expertsGento Sato noted irony of America use of Yagi antennas on atomic bombs to determine height of explosionHistory Military PlatformsVertically polarized antennas on Lichtenstein radar-equipped German Ju 88R-1 fighter-bomberBritish Short Sunderland (Flying Porcupine)

Arrays also seen on Grumman F4F, F6F, TBF Avenger, P-61 and many other aircraft

Theory of Operation Driven ElementDriven element is the only dipole excited by source currentLength of dipole antenna slightly less than half-wavelength (0.48-0.50 wavelengths)Near-field equation used to calculate induced current from driven element to parasitic elementsDriven element no longer point sourceAlternate shapes of basic elementsCircular loopsFolded dipoleTypical dipole gain: 2.2 dBTheory of Operation Parasitic ElementParasitic elements re-radiate power received from driven element through mutual couplingParasitic element slightly larger or smaller length than driven elementReflector elements larger than half-wavelength have inductive reactancesLags in phase from driven currentDriven element smaller than half-wavelength have capacitive reactancesLeads in phase from driven currentParasitic element acts as dipole short circuited at feed pointReflects all incident power 180 degrees out of phaseTotal phase shift = 180 degrees reflection + reactance phase shift (lag/lead) + finite distance delay between driven element and directorTypical Yagi antenna gain: 10-20 dBForward shift = 180 reflection 70 reactance = 110 degree shiftBackward shift = 110 degree shift + (35 degree time delay)*2 = 180 degree shift

Theory of Operation 2 Element ArrayCase 1: Driven Element +Larger AntennaLarger antenna is reflectorLength usually between 0.52-0.48 wavelengthsMore reflectors minimally increases performanceAverage number of reflectors: 1Case 2: Driven element+Shorter AntennaShorter antenna is directorDirector length usually 0.4-0.48 wavelengthsLength not necessarily same for each directorMore directors considerably increases performanceAverage number of directors: 6-12

Theory of Operation Element SpacingSeparation of directors usually 0.3-0.4 wavelengthsNot necessarily uniform for optimal designsSeparation of reflector usually 0.2-0.3 wavelengths

Theory of Operation - OptimizationCharacteristics of interestForward and backward gainInput impedanceBandwidthFront/Back RatioMagnitude of minor lobesYagi-Uda parameters computer-generatedIntegral equation-moment method used to find electric field and current distributionsOptimization procedure determined by adjusting geometrical parameters of arraySpacing between elementsLength and radius of elementsNumber of directorsTypical gain of Yagi-Uda antennas3 element: 7 dBi4 element: 9 dBi6 element: 10.5 dBi8 element: 12.5 dBi12 element: 14.5 dBi15 element: 15.5 dBi18 element: 16.5 dBi

Source: Antenna Engineering Handbook (Johnson)Optimization

Table from Yagi Antenna Design by P. Viezbicke from the National Bureau of Standards, 1968

Yagi Uda FEKO ModelYagi antennaOne reflector elementOne driven elementTwo director elementsSimulated as wire elementsCenter frequency 1 GHzCenter frequency irrelevant20 MHz bandwidth (arbitrary)OptFEKOParametersDipole lengthSpacingOptimization goalsMain lobe minimumBack lobe maximumVSWR maximumDesign / Optimization

Original

OptimumRadiation Pattern

Original Design - Gain (dB)Optimum Design Gain (dB)Far Field Gain Polar Plot

Far Field Gain Linear Plot

Yagi Antenna Voltage Standing Wave Ratio (VSWR)

Recent DevelopmentsWideband microstrip Yagi Uda AntennaDeveloped by J. Juang from C.I.T. Jet Propoulsion LaboratoryYagi Uda directionality implemented as a patch antennaPrimary use in vehicle mounted systems and SHF systems (WLAN)Low profile, lightweight, inexpensive, simple fabricationElectronically-steerable Yagi smart antenna arraysBeam can be steered from 0 to 360 degrees in horizontal planeLow power consumption and cost

Recent DevelopmentsVertically stacked Yagi Uda antennaReduces side lobesWide illuminating areas with high gainDeveloped for long range meteor burst communicationK3CR (PSU amateur radio club)

Closing RemarksMulti-element directional antennaExtensive use in WWII for communication and radar systemsUse in commercial communication (radio and television)Basic operation mechanismsPotential for optimization of desired parametersRecent developments and continuing usageSources[1]D. M. Pozar, Beam Transmission Of Ultra Short Waves: An Introduction To The Classic Paper By H. Yagi, Proc. IEEE, vol. 85, no. 11, pp. 18571863, 1997.[2]H. Yagi, Beam Transmission of Ultra Short Waves, Proc. Inst. Radio Eng., vol. 16, no. 6, pp. 715740, 1928.[3]D. K. Cheng, Gain optimization for Yagi-Uda arrays, IEEE Antennas Propag. Mag., vol. 33, no. 3, pp. 4246, 1991.[4]Y. Kuwahara, Multiobjective optimization design of Yagi-Uda antenna, IEEE Trans. Antennas Propag., vol. 53, no. 6, pp. 19841992, 2005.[5]J. Lei, G. Fu, L. Yang, and D. -m. Fu, Optimization of a wideband vertically stacked Yagi-Uda antenna array, in International Conference on Microwave and Millimeter Wave Technology, 2008. ICMMT 2008, 2008, vol. 3, pp. 11101113.[6]J. Huang, Planar microstrip Yagi array antenna, in Antennas and Propagation Society International Symposium, 1989. AP-S. Digest, 1989, pp. 894897 vol.2.[7]H. Liu, S. Gao, and T.-H. Loh, Small Director Array for Low-Profile Smart Antennas Achieving Higher Gain, IEEE Trans. Antennas Propag., vol. 61, no. 1, pp. 162168, 2013.