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Study and Implementation of the Log-Periodic Dipole Array Antenna for Electromagnetic CompatibilityLee, Chih-Chieh 02 July 2002 (has links)
Abstract.
The problem of Electromagnetic compatibility is a popular topic. It is divided into two categories, one is conducted electromagnetic interference, another is radiated interference. We can use LISN to measure the signal of conducted electromagnetic interference , and use antenna to measure the signal of radiated interference. This paper will focus on the antenna.
The frequency range of radiated Electromagnetic Interference measurement is so wide that using the halfwave dipole antenna will be very time-consuming, Therefore broadband antennas are often used in lieu of the halfwave dipole antennas. The design procedure of the log-periodic dipole array antenna is introduced in this article. Simulation data of such antenna using the NEC2 software, including the input impedance and the antenna pattern are also provided. Furthermore, based on the parameters obtained from the simulation, a log-periodic dipole array antenna can be fabricated. In doing so, the simulation results should be modified to take into considerations of the specification of the material used, such as diameters of the materials, and lengths of the transmission lines. Once the construction of the log-periodic dipole array antenna is completes, it can be compared with the simulation results, and the difference between them should be investigated to find out the optimal design parameters. Finally, the antenna factor can be calculated to compare it with the measurement data.
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A Study of the Effects of the Ground Plane and the Phase Center on the LPDA Antenna FactorChang, Chih-Hao 29 July 2004 (has links)
Abstract
Whether an Open Area Test Site (OATS) is qualified is based on the Normalized Site Attenuation (NSA). The purpose is to eliminate the influence of Antenna Factor (AF). Usually the AF provided by the manufacturer adopts the Standard Site Method (SSM) and is quoted from measurements at a 10-m range. In practice, the AF varies with the measurement conditions. This uncertainly will translate into error in NSA measurements. Currently radiated electromagnetic interference measurement mostly adopts the broadband antennas, and LPDA is one of the antennas used extensively. However, the AF provided by the manufacturer does not consider shifts in the phase center of LPDA with frequency. In the meantime the radiation pattern of LPDA is different from that of a short dipole. The investigation of this thesis will focus on these two parts.
In determining the phase center of LPDA antenna we adopt the average shift of phase center to improve the AF. The numerical simulation results show that such an arrangement can result in improvement. We also use the method of PCPM (Phase Center and Pattern Matching) to modify the AF under different conditions of measurement when a ground plane is present. Our study, by using the numerical simulation and measurement, shows that this indeed improves the variation of AF over that obtained by SSM. In addition, efforts are also made to have a detailed discussion in mutually coupling effects between the LPDA antenna and the ground plane, in order to distinguish the impact on AF due to the coupling of the LPDA antenna and its image. Our numerical simulation results indicate that it does not have a significant effect.
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A DIRECTION FINDING SYSTEM USING LOG PERIODIC DIPOLE ANTENNAS IN A SPARSELY SAMPLED LINEAR ARRAYWeldon, Jonathan Andrew 08 July 2010 (has links)
No description available.
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An artificial magnetic ground-plane for a log-periodic antennaVisser, Hugo Hendrik 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This paper presents the implementation of an artificial magnetic ground-plane with a low profile
Log-periodic Dipole Array (LPDA) antennas. After the properties of three typical Electromagnetic
Bandgap (EBG) structures are investigated and their bandwidth properties are studied, a
mechanism is presented to improve the band-width over which the EBG surface acts as a perfect
magnetic conductor (PMC). A low profile LPDA is modeled above this surface and the results
indicate an improved band-width region. Compared with a LPDA in free space the frequency
band is shifted higher by the EBG surface and the gain pattern is shifted from a horizontal
orientation to a vertical orientation. / AFRIKAANSE OPSOMMING: Hierdie dokument stel voor die implementering van kunsmatige magnetiese grondvlakke met
Logaritmiese Periodiese Dipool Samestelling (LPDS) antennas. Die eienskappe van drie tipiese
Elektromagnetiese Bandgaping (EBG) strukture word ondersoek en hul bandwydte eienskappe
word bestudeer. ’n Meganisme word voorgestel om die bandwydte te verbeter waar die EBG
oppervlakte soos n perfekte magnetiese geleier optree. ’n Lae profiel LPDS word bo hierdie
oppervlakte geplaas. Die resultate dui aan ’n verbetering in the bandwydte. In vergelyking met
’n LPDS in vrye ruimte skuif die frekwensie band ho¨er as gevolg van die EBG oppervlakte en
die aanwins patroon skuif van ’n horisontale orientasie na ’n vertikale orientasie.
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Characteristics of the log periodic dipole arrayOnwuegbuna, Leonard Ikemefuna 28 February 2007 (has links)
Student Number : 9713144D -
MSc Dissertation -
School of Electrical Engineering -
Faculty of Engineering and the Built Environment / The performance of the Log Periodic dipole array antenna has been characterized,
in the form of parametric curves available in most antenna design handbooks and
other relevant literature. These characteristic curves are often limiting in scope,
as for instance they do not contain parametric curves giving the relationship
between the boom-length 'L' and the number of dipole element 'N' for any given
bandwidth, even when it is known that these two parameters are the main cost
determinants of a LPDA Antenna. The concept of convergence is introduced to
aid cost optimization of the LPDA Antenna in terms of number of dipole element
'N'. Although 'N' is used as the minimization criterion, the criteria for establishing
convergence encompass all the main electrical characteristics of the LPDA
Antenna, such as VSWR, gain and radiation patterns. Lastly, the effects of boomimpedance
'Zo' and length to diameter ration 'Ln/Dn', on the performance
characteristics of the LPDA Antenna was investigated with the view to
determining if neglecting the effects of these two parameters were responsible for
the disparity in the directive gain values obtained by R. L Carrel compared to
those obtained by later researchers. The investigation indicates that if an LPDA
Antenna is converged, then the effects of Zo and Ln/Dn ratio though significant
can not alone account for the fairly large disparity in the gain values.
In other to perform these investigations, a modern scientific tool in the form of
numerical modeling by method of moments based, Super Numerical
electromagnetic code version2 was utilized. The numerical modeling tool was
first validated by agreement between measured values and the values as predicted
by the modeling tool. Next, simulation of the performance of LPDA antennas
under variations of their number of elements was done. Thereafter, the means and
standard deviations of the gain were extracted from the simulated numerical
models. Trends in the pattern of variation of the means and standard deviations of
the gain are used as the basis for deciding the value of number of element at
which the antenna can yield acceptable performance (convergence criteria). These
are presented as convergence curves, which gives for any given boom-length and operating bandwidth, the minimum number of elements required for the antenna
to yield acceptable performance.
Finally, the effect of length to diameter ratio and boom-impedance on the gain of
optimized LPDA antennas are presented as parametric curves.
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Full scale low-cost ultra wide band antenna for SKA low frequency arraySchoeman, Dewald Hermanus 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis is about the design, simulation and measuring of ultra wide band antennas
for use in the Square Kilometre Array (SKA).
The SKA is a radio astronomy project with one of the aims of detecting hydrogen particles
in deep space. Several thousand antennas over a wide band of frequencies are needed
to receive the radiation from these particles. This motivates the need for a low-cost ultra
wide band antenna with the focus on the low frequency part of the SKA.
In this thesis we present two design strategies:
The first design strategy is for a printed LPDA on a substrate and design curves are
generated. A scale model was built and measurements did not correlate with simulation
results. This is due to manufacturing tolerances and assembly of the pyramidal structure.
The second design strategy is for a full scale zig-zag antenna and design curves were also
generated. The aim here is to produce a low-cost prototype by using brazing rods for
the wire structure and mount it on a wooden frame. A full scale model was built and
measurements on the roof produced much interference for the radiation pattern, but the
reflection coefficient was good. We suggest doing measurements in an interference free
environment in order to achieve the needed results.
To conclude we suggest using the zig-zag antenna for the SKA. Some issues do however
need more attention as the transformer has some losses, the cross polarisation is probably
not good enough and the beamwidth does not reach the specification. We demonstrated
a low cost prototype and there is the possibility of low-cost large scale manufacturing but this needs to be addressed. This has however not been analysed as many factors for large
scale manufacturing are very difficult to predict beforehand and lies outside the scope of
this thesis. / AFRIKAANSE OPSOMMING: Hierdie tesis gaan oor die ontwerp, simulasie en opmeting van ultrawyebandantennas
vir gebruik in die SKA ("Square Kilometre Array").
Die SKA is ’n radioastronomie projek met die doel om waterstof partikels op te spoor
in die ruimte. Duisende antennas wat oor ’n wye band van frekwensies strek is nodig
om die energie van die partikels op te vang. Hieruit is daar ’n aanvraag vir lae-koste
ultrawyebandantennas met die fokus op die lae frekwensie deel van die SKA.
In hierdie tesis word twee ontwerpstrategieë voorgestel:
Die eerste ontwerpstrategie is vir ’n gedrukte logaritmies periodiese dipool reeks (LPDR)
op ’n substraat tesame met ontwerpskurwes wat gegenereer word. ’n Skaal model is gebou
en die gemete resultate stem nie ooreen met die simulasie nie. Dit kan toegeskryf
word aan vervaardigingstoleransies en die aanmekaar sit van die piramide struktuur.
Die tweede ontwerpstrategie is vir ’n vol skaal sigsag ("zig-zag") antenna met ontwerpskurwes
wat ook gegenereer word. Die doel is om ’n lae-koste prototipe te bou deur
sweissoldeerdraad te gebruik vir die draadstruktuur en dan op ’n hout raam te plaas. ’n
Vol skaal model is gebou en metings op die dak het baie interferensie veroorsaak vir die
stralingsveld, maar tog was die weerkaatskoëffisient goed. Ons stel voor om die metings
te herhaal in ’n steuringvrye omgewing om sodoende die korrekte resultate te verkry.
Om af te sluit stel ons voor om die sigsag antenna vir die SKA te gebruik. Sekere kwessies
soos die transformator wat verlieserig is, die kruispolarisasie wat moontlik nie goed genoeg is nie en die bundelwydte wat nie die spesifikasie haal nie moet nog aandag geniet.
Ons het ’n lae-koste prototipe gedemonstreer en daar is die moontlikheid om dit op
grootskaalse vervaardiging ook goedkoop te doen, maar dit moet nog uigesorteer word.
Dit was wel nie geanaliseer nie, siende dat vele faktore ’n rol speel by grootskaalse vervaardiging
wat uiters moeilik is om voor die tyd te voorspel en buite die omvang van
die tesis lê.
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