design and test of: wide band and highly polarized...

TVE 17007

Examensarbete 15 hpOktober 2017

Design and Test of: Wide Band and Highly Polarized Antenna for 60GHz

David Larsson

Institutionen för teknikvetenskaperDepartment of Engineering Sciences

Teknisk- naturvetenskaplig fakultet UTH-enheten Besöksadress: Ångströmlaboratoriet Lägerhyddsvägen 1 Hus 4, Plan 0 Postadress: Box 536 751 21 Uppsala Telefon: 018 – 471 30 03 Telefax: 018 – 471 30 00 Hemsida: http://www.teknat.uu.se/student

Abstract

Design and Test of: Wide Band and Highly PolarizedAntenna for 60GHz

David Larsson

In this work high gain antennas are investigated for the 60 GHz frequency. The goal isto produce a high bandwidth point-to-point wireless network that could enableimproved and new features in embedded systems used to detect particles in highenergy physics.

A literature study was performed aiming at simple, high gain, highly polarisedantennas. Complex designs were grouped into three different groups: flat antennadesign, build-up design and multi-antenna design. The multi-antenna design was foundto have the simplest design and manufacturing but also feature larger antenna area.

Three different designs were produced and tested, standard patch antenna, long patchantenna and a Vivaldi antenna. Manufacturing of a 4-patch antenna was also tested. Allthree demonstrated expected properties, the Vivaldi shows the best gain while thelong patch antenna is slightly below the standard patch antenna.

A forth design implementation was also tested using a 3D-printed lens. A lens canincrease gain and allow changing beam direction. A lens was design and tested, theresults showed an increased gain but with varying results at angels.

Antennas were designed and manufactured using simple etching technique showingthat further research can be done using simple and easily accessible techniques. Bothantenna and lens show good properties and should be further investigated andvalidated.

TVE 17007Examinator: Nora MassziÄmnesgranskare: Dragos DancilaHandledare: Richard Brenner

Sammanfattning

I det har arbetet har jag undersokt antenner med hog forstarkning vid frekvensen60 GHz. Malet ar att utveckla punkt-till-punkt natverk med hog bandbredd for detek-torer i partikelkolliderare. Idag anvands tradade natvark i detektorn, genom att bytatill tradlos dataoverforing kan onodig massa minskas och kvalitet forbattras.

En litteraturstudie genomfordes med inriktning mot enkla, starkt forstarkande ochkraftigt polariserad antenner. Tre olika typer defineras: platta designer, uppbygda de-signer och antenngrupper. Antenngrupper var de med enklaste design och tillverkningmen ocksa de med storst area relativt de andra.

Tre olika antenner tillverkades och testades: patchantenn, lang patchantenn ochVivaldiantenn. Aven en 4-patch antenn tillverkades. Produktionen av alla antennerholl hog kvalitet och de testade egenskaperna var forvantade. Vivaldiantennen hadestarkast forstarkning av de testade antennerna, den langa patchantennen presteradestrax under standard patchantennen.

Aven tester av en antenngrupp bestaende av en patch antenn oc hen antennlinsgjordes. Genom att anvanda en lins kan forstarkningen okas och riktningen andras. Enlins designades och tillverkades med en 3D-skrivare. Resultat fran tester visade pa enokad forstarkning men med varierande resultat vid vinklar.

Antenner designades och tillverkades med en enkel etsningsmetod, detta visar attforsatta undersokningar kan utnyttja enkel och lattilganlig teknik. Goda resultat upp-visades med bade antenner och lins. Framtida studier kan utforas for att vidarutvecklaoch validera konceptet.

Contents

1 Introduction 1

2 Theory 22.1 Antenna Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Antenna Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2.1 Patch antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2.2 Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.3 Horn Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 Antenna Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.5 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Production 63.1 Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.2 Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Antenna and Signal Measurements 7

5 Results 95.1 Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95.2 Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95.3 Simulated Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.3.1 Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.3.2 Modified Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . 105.3.3 Bowtie Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115.3.4 Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115.3.5 Simulated Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.4 Antenna Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.4.1 Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.4.2 Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5.5 Lens Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.6 Measurement Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6 Discussion 186.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.2 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.3 Point-to-point efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.4 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.5 Future Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

7 Conclusion 20

8 Appendix 218.1 Simulated Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8.1.1 Simulations for a simple square-patch antenna . . . . . . . . . . . . . 218.1.2 Simulations of Patch Antenna with Lens . . . . . . . . . . . . . . . . 248.1.3 4-Array Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . 278.1.4 Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308.1.5 Split Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

8.2 Screenshots from RTO 1024 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368.3 Table of article . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

List of Figures

1 The different unlicensed bands [1]. . . . . . . . . . . . . . . . . . . . . . . . . 22 E-fields going from left to right under antenna. . . . . . . . . . . . . . . . . . 33 A short dipole antenna with L proportional to wavelength (λ). . . . . . . . . 44 An advanced dipole antenna for LTE/WiMAX. . . . . . . . . . . . . . . . . . 55 Oscilloscope output of a square patch antenna. . . . . . . . . . . . . . . . . . 76 Picture of manufactured and mounted Vivaldi antenna. . . . . . . . . . . . . 97 Picture of manufactured Vivaldi antennas opening. . . . . . . . . . . . . . . 98 The polarisation ratio of a simple square patch antenna. . . . . . . . . . . . . 109 An experimental patch antenna with rounded corners. . . . . . . . . . . . . 1110 Radiation of an U-slot antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . 1111 The Radiation of 4-patch array antenna. . . . . . . . . . . . . . . . . . . . . . 1113 Bowtie Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1212 4-array square-patch antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1314 The effect of a lens on a square wave-port. . . . . . . . . . . . . . . . . . . . . 1415 The effect of a lens on a square wave-port. . . . . . . . . . . . . . . . . . . . . 1516 Unmounted Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1617 Measurement Short Patch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1618 Comparison Long and Short Patch . . . . . . . . . . . . . . . . . . . . . . . . 1719 Vivaldi Antenna Measurements with std . . . . . . . . . . . . . . . . . . . . . 1720 Angular Offset with Lens Measurement . . . . . . . . . . . . . . . . . . . . . 1821 Gain and std of Short, Long and Vivaldi Antenna . . . . . . . . . . . . . . . 1922 Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2123 Patch Antenna Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2224 Patch Antenna 3D Polar radiation . . . . . . . . . . . . . . . . . . . . . . . . . 2225 Patch Antenna Radiation rE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2326 Patch Antenna 3D Polar Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 2327 Patch Antenna with Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2428 Patch Antenna with Lens Frequency . . . . . . . . . . . . . . . . . . . . . . . 2529 Patch Antenna with Lens 3D Polar Radiation . . . . . . . . . . . . . . . . . . 2530 Patch Antenna with Lens Radiation rE . . . . . . . . . . . . . . . . . . . . . . 2631 Patch Antenna with Lens 3D Polar Ratio . . . . . . . . . . . . . . . . . . . . . 2632 4-Array Patch Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2733 4-Patch Antenna Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2834 4-Patch Antenna 3D Polar Radiation . . . . . . . . . . . . . . . . . . . . . . . 2835 4-Patch Antenna Radiation rE . . . . . . . . . . . . . . . . . . . . . . . . . . . 2936 4-Patch Antenna 3D Polar Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . 2937 Vivaldi Antenna on substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . 3038 Vivaldi Antenna Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3139 Vivaldi Antenna 3D Polar Radiation . . . . . . . . . . . . . . . . . . . . . . . 3140 Vivaldi Antenna Radiation rE . . . . . . . . . . . . . . . . . . . . . . . . . . . 3241 Vivaldi Antenna 3D Polar Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . 3242 Split Vivaldi Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3343 Split Vivaldi Antenna Frequency . . . . . . . . . . . . . . . . . . . . . . . . . 3444 Split Vivaldi Antenna 3D Polar Radiation . . . . . . . . . . . . . . . . . . . . 3445 Split Vivaldi Antenna Radiation rE . . . . . . . . . . . . . . . . . . . . . . . . 3546 Split Vivaldi Antenna 3D Polar Ratio . . . . . . . . . . . . . . . . . . . . . . . 3547 Patch antenna at 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3648 Patch antenna at 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3649 Patch antenna at 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

50 Patch antenna at 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

List of Tables

1 Design parameters of Lens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Antenna Simulations Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Table of antenna designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

1 Introduction

In large detectors at particle collision experiments there is a massive amount of data thatneed to be registers in a short time. Today this is done using cables, mostly fibre-optic,introducing a large amount of dead material in the detector. By switching to a wirelesssystem, there could be savings in mass and a improvement for flexibility in routing ofthe detectors. There is also a need to further increase the bandwidth of the data links,especially for future upgrades. The most researched wireless communications today arein the WiFi bands of 2.4 and 5 GHz. The 60 GHz have two main advantages over these,the increase in data transfer and the propagation of the signal. While 5 GHz penetratesmany materials to a large degree, 60 GHz is stopped. When working with dense systemssignal blocking means less interference. The shorter wavelength also means that antennasize decreases.

Systems based on 60 GHz technology are already commercially available and the tech-nology will continue to improve research in many areas. For the high density systems,research on high gain antennas and especially research for on-chip applications is stillneeded. There are many studies on patch antennas generally and in particular on-chipintegration.

On-chip antennas ,both single and double-sided structures, have a feed structure thatexcites the antenna in the planed. Antenna designs include square-patch, monopole, slot,notch and any combination of these as well as arrays of antennas. The ground plane ofthe antennas are also designed to match the antenna. Much of the focus is on bandwidthof antennas, sometimes exceeding an impedance bandwidth range of 1:10. This widebandwidth does often result in other undesired properties such as low polarisation orlow gain. Antenna arrays offer a simple solution by simply adding several units withslightly tuned properties to complement each other. Antenna arrays have the drawbackof increasing size and complexity as the array grows larger. An interesting design hasbeen developed by C. Karnfelt et al., a linear array that gives very high gain in one plane.These antennas become more and more complex as they are developed, which also makesmanufacturing more difficult. Another method to introduce high gain is by using a lens.A lens is made of a dielectric material and can be used to focus the electromagnetic signal.

There is currently research ongoing at Uppsala University to replace optical cableswith wireless communications utilising the 60 GHz band. Three main alternatives to pro-duce a broadband antenna are investigated: changing patch design, changing antennaconcept and planar arrays. The goal is to produce an antenna with high gain, large band-width and narrow polarisation. Antenna should be design to be produced on-chip as afuture step is to produce one printed circuit board (PCB) with both amplifier and antennato minimise complexity and size of installation.

1

Figure 1: The different unlicensed bands [1].

2 Theory

Extremely high frequency (EHF) antennas work in the range of 30-300 GHz and have awavelengths of 1 cm-1 mm as defined by International Telecommunication Union (ITU).Institute of Electrical and Electronics Engineers (IEEE) has the V band defined as 40-75GHz with corresponding wavelength of 7.5-4 mm. The 60 GHz frequency is unlicensedin most of the world. The current unlicensed band varies between countries as shownin figure 1. The European Union has decided on a wide band from 57-66 GHz witch isdesigned to cover both the low frequencies (not included in Korea) and high frequencies(not included in Japan). Taking into account the different bands from around the world,4 channels have been defined were channel two, centred at 60.48 GHz, is the globallyunlicensed channel.[1] High gain antennas with both wide and narrow frequency spanswill be developed and used in different applications.

The capacity in the 60 GHz band is roughly 10 times that of the 5 GHz network andanother two times that of 2.4 GHz, amounting close to 10 Gbps rate. This means thatstreaming uncompressed 4K movie (video and audio) is possible in this network. In ad-dition to the available data transfer rate there are other factors that helps increase data ca-pacity in a large 60 GHz network. The 60 GHz band is easily disrupted by solid materials,this means that only line of sight applications are possible which reduces the interferencebetween closely spaced links. This combined with high gain antennas and polarised sig-nals means that wireless transmissions can be densely packed and replace cables in someapplications. When comparing wireless and fibre-optic solutions a cable usually weightmore than 10 g/m and requires connectors while wireless solutions at 60 GHz uses micro-chips of a few mm2 integrated with an antenna giving a total weight of a few grams. Withthe possible weight reduction and consequential mass reduction it is beneficial for specialapplications. Replacing wires in small spaces could also mean easier maintenance. Re-search in passive and active signal bridges are another area which can be improved andwould make it possible to pass a signal round corners or past walls [20].

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2.1 Antenna Theory

There are two fundamental parameters to in antenna: radiation and signal matching.

Figure 2: E-fields going from left to right un-der antenna.

Antennas radiate when electrons areaccelerated. The same principle that pro-duce light from the heated hotplate pro-duce radio waves from oscillating cur-rents. In fact, when measuring the cos-mic background radiation of universe wemeasure the very first electromagnetic ra-diation visible in the universe. Originallyat about 3000K, corresponding to infra-redlight, it would have been observed usingan ir-detector(ir-camera). Today, becauseof the expansion and cooling of the uni-verse, we need microwave antennas to ob-serve it[15].

When a current is stimulating the antenna, a field will form between the conductingmaterials. This is shown in a simple square-patch antenna (figure 2).

Polarisation defines which direction, in the room dimension, the electromagnetic waveis oscillating. A wave moving in z-direction can either oscillate in x, y or any combinationby the two. In our application a linear polarisation is favourable as it allows a denserantenna packaging without interference. For a linearly polarised antenna with an signif-icant signal strength angle of π/6, 5 antennas could be used in concordance. Of course,the better the linear polarisation is, the more antennas can be used. Other polarisationscan be used and have their own advantages but will not be discussed further in this pa-per. The simple square-patch antenna is naturally linearly polarised as the e-field is inparallel(figure 8).

The feed structures investigated here are all based on an in-chip design, meaning a flatconnections. Feed lines for patch antennas are well researched and are generally a simplestrip with a length based on wavelength and thickness and width for impedance match-ing.For other antennas several different feed structures are possible. The feed structureis very important for optimising performance, especially to match the antenna with thesignal.

2.2 Antenna Design

In designing an antenna there are two optimisations, to direct the current into the antennaand to produce a current flow that gives the desired radiation properties. The simplestantenna is the dipole antenna which is an open circuit (Figure 3).

This antenna creates a field between its open ends and demonstrate a simple antennadesign that can be easily studied. The main parameters are length/wavelength and thick-ness. The current flow in the dipole antenna travels towards its open ends. By matchingthe impedance a signal leaving the signal generator is transported through the antennawithout loosing strength. This can be very difficult in some compact antenna designs andhence different methods for matching impedance can be used.

3

Figure 3: A short dipole antenna with L pro-portional to wavelength (λ).

For radio waves a coax cable can be used as antenna. While this simple design is veryefficient there are numerous ways to modify it to adapt to any properties needed. Thisis illustrated in a microchip dipole antenna design for advanced mobile net operation(Figure 4).

2.2.1 Patch antenna

The basic patch antenna, also refereed to as square- or microstrip antenna, is a flat metalpiece on a substrate with a ground beneath (it could easily be manufactures by usingpaper and kitchen foil). The feeding is traditionally in the middle of the patch. A coaxialcable would be connected from the backside and the feed line would be put through ahole and connected to the patch structure on the top. A feed can also be introduced fromthe side of the antenna (strip-line). By cutting into the patch it is possible to move the feedpoint into the patch as desired. The strip-line for the patch antenna is extensively studiedand has many design variations[19]. The line can be designed in segments to better matchimpedance between feed and antenna. Passive and grounded patches can be added to thedesign to increase the control of impedance. The feed line can also be put on the backsidetogether, or without, ground plane and feed the antenna passively or with a probe. Thereare also multi layer designs for feed structures with an aperture for the feed in the middleplane.

A patch antenna can be design with different shapes and profiles[10, 14, 7], there isalso plenty of development on square patch arrays. They show increased gain for 2x2arrays and even more gain for larger and more complex arrays[2, 12]. By combininglinearly polarised designs at different angles, a cross or multi-polarised antenna can bedesign quit easily.

2.2.2 Vivaldi Antenna

The Vivaldi antenna is a variation of the slot antenna where the circuit is closed in onedirection and with a width that is varied. Vivaldi antennas offer very distinct and goodproperties from a simple design. They are broadband, coplanar, linearly polarised and

4

have a high gain. The simplest form of an Vivaldi antenna is shown in Appendix 8.1.4 Acurrent is produced over a widening slot generating an electric field in between. Thereare several different ways to design the slot and the feed structure to further increaseperformance. There are also varying designs such as double sided antennas and out-of-plane radiation designs[4, 11].

2.3 Horn Antenna

Figure 4: An advanced dipole antenna forLTE/WiMAX.

A horn antenna uses an technique to con-centrate the radiation, it can be poweredby any kind of antenna structure, such asa dipole or patch. Radiation pattern is con-trolled using a reflective horn in the sameway as a megaphone. While they showvery good properties they require verticalor multi-layer constructions.[18, 13]

2.4 Antenna Lens

Previous studies have shown the possi-bility of using a dielectric material as a”lens” for gigahertz antennas. Good per-formance has been achieved with hemi-spherical lenses[5, 9]. These are done bysynthesising an ellipse using an extendedhemisphere. Calculations are presentedwith variable wavelength and dimensionsand can therefore easily be fitted for otherdesigns and frequencies. These calcula-tion uses the optical method of refractionindex to find the geometrical focus, forcalculations of propagation, a more com-plex method is used. The antenna radi-ation patterns are calculated assuming si-nusoidal magnetic current and using ray-tracing. Integration of fields produce theE- and H-plane for the antenna/lens con-figuration.Based on these calculations several differ-ent lens designs and sizes produced andtested several different lens designs andsizes[5]. A hyper-hemispherical lens showed best performance. These tests were doneat 140 GHz and a lens concept were developed and tested.

Other designs might be more efficient, especially when mass is an important param-eter. By using different inner and outer shell geometry it should be possible to increaseperformance and decrease total mass. Especially as 3D-printing is used for production,there is little limits to the design. While these lenses have a more general design concept,future lenses should have a design adapted to a specific antenna[6, 16, 3]. This shouldgive greater efficiency over a larger frequency span. A lens design should be adapted toprovide the best gain for a specific bandwidth and polarisation. One important feature ofa lens is making it possible to enhance antenna designs with undesired radiation proper-

5

ties (such as the linear array patch antenna[8]). This technique could also prove valuablein developing antennas for harsh environments, such as cars, were the lens would alsoact as protection for the conducting surfaces.

2.5 Simulations

Simulation was done using ANSYS HFSS which uses a multitude of techniques based onfinite element method (FEM). Along advanced tetrahedral meshing and iterative solvingit also features several analysis tools to control elements and calculations. HFSS solves”thinks” in magnetic and electric fields, this is important when you consider weak pointsof the solutions. Solving for field means that any wave-port is especially susceptibleto faults in the module. Simulations done in FEM programs can usually be analysedand optimised for various variables by using methods such as Monte-Carlo or NeuralNetwork Analysis. These methods are increasingly more efficient as models increase insize and complexity. For simple designs such as single antennas there is generally no needoff these methods. When doing frequency sweep simulations, by default, HFSS solves fora target frequency and then extend the same solution to the other frequencies, this meansthat wide-band solutions can become less accurate. Wide-band antennas should be solvedfor several frequencies to test reliability.

3 Production

Microwaves can be absorbed, reflected or interfered by a material. For 60 GHz, absorptionis particular high for water(including steam). For antenna components the attributes forthe materials are crucial for the antenna properties.

3.1 Antenna

Antennas were produced using double side copper etching on pretreated dielectric sheets.Lithography and etching were done in the lab while the material were coated off-site. Thematerial used were from two manufacturers, Rogers and DuPont and were available fordifferent thickness. No adaptation for eventual etching effects where done. Exposuretime was 60 seconds per side using: UV-Exposure Box 2 from Gie-TEc GmbH and etch-ing time was controlled by visual inspection, roughly around 200 seconds with sodiumpersulfate (CAS:7775-27-1) at 50 C. A tank with bubbles being injected evenly along thebottom was used. Some manual mechanical work on the copper where done to trim thestructure to achieve a good result. This can be avoided by redesigning stencils to accountfor the etching limitations. All work was visually inspected and compared to the stencilto evaluate the quality and detect any damage. Completed and approved antennas wherethen sent to Angstrom machine to be prepared for the SMC-connector.

3.2 Lens

The design for the 60 GHz application were based on the previous hyper-hemisphericallens developed by [5]. Adaptation is needed for a change of frequency. Three radius werechosen for modelling with a large span: 5, 10 and 15 cm. The lens was produced using3D-printing and the material were a Stratfaceasys ABS-polymer with an reported dielectricconstant of 2.7-2.9. This could warrant a further extension of the lens due to the lowerdielectric value. It should be noted the true dielectric constant of the 3D printed materialcould differ from the reported material properties. Both porosity and directivity from theprinting could affect properties.

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Table 1: Design parameters of Lens.Radius(cm) 5 10 15Offset(cm) 1 2 3

The hyper hemispherical lens was kept at athickness of 1.5 times radius. The lens was designwith a double radius bottom plate and a backplatewith a matching pin/hole for mounting. Whilemanufacturing using 3D-printing is readily avail-able a mismatch in available software between simulation and manufacturing meant thatany models had to be remade using alternative software. The lens produced and testedhas a radius of 10cm and an offset of 2cm.

4 Antenna and Signal Measurements

The physical dimensions of the antenna were measured using high sensitive measuringsystem with micrometer precision with Smartscope Flash.1. There were also measurementand inspection done using microscope and digital calliper. The set-up used to measureproperties of the antenna utilised a signal generator 2 capable of generating 0.5-1.3 GHzsignals at 50Ω. The signal is then passed to channel 2 of the oscilloscope, RTO 1024, andto a 90 degree split. The split then connects to the frequency converter 3 that connects tothe antenna through a SMC connector. On the opposing side of the setup a horn antenna

Figure 5: Oscilloscope output of a square patch antenna.

1Smartscope Flash. Optical Gaging Products, INC.2NI PXIe-1082 RF signal generator.3Siversima CO1211A/00,

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is attached to a second converter which connects to channel one on the oscilloscope. Theconverters are connected and controlled by the signal generator and can be set at differentfrequencies. One of the antennas is mounted on a horizontally rateable arm to allowfor angular changes up to 25 degrees. The signal is processed by an oscilloscope thatincludes live step-FT analysis which is especially useful when setting up antenna-lensmeasurements as it gives immediate response to any change in the setup. The live FT isalso good for controlling the quality of the setup in reference to internal disturbance as ashield around the receiving antenna will remove any external signals and reactions whenmoving or rotating the setup can be observed. This setup is limited in frequency range,hence most suitable for testing gain and comparing antennas. The second setup consistsof a full range GHz (≤75 GHz) signal generator and a 3D-setup. This allows for moreadvanced measurements for full 180 degree angles. Set-up use a known horn antennafor reception. Connecting antennas to the setup is a large challenge when comparingantennas with different sizes and geometry. When doing measurements with the lens thelens was mounted on top of the Horn-Antenna, meaning it stayed while antennas wereswapped.

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5 Results

5.1 Literature review

Several antennas have been researched, in appendix 8.3 the table shown some, with key-figures. Antennas design for 60 GHz as well as other millimetre-wave antennas wereused as basis for the design process.

5.2 Manufacturing

Figure 6: Picture of manufactured and mountedVivaldi antenna.

Manufacturing results were goodwith finished product matching sten-cils to a high degree. Narrow corri-dors were the most troublesome weregaps would be smaller than intended.After manual removing of excessivematerial a better match was achieved.In figure 6 the antenna and connectorfor a Vivaldi antenna is shown. Somesamples were dismissed, mainly be-cause of damaged coatings. Af-ter etching, antennas showed wavyedges as can be seen in figure 7, theseare caused by known etching phe-nomena and could be avoided with abetter setup. By using a more efficientetching more consistent results wouldbe possible. No further analysis was

done on the quality of manufactured antennas such as comparing double produced an-tennas.

5.3 Simulated Antennas

Figure 7: Picture of manufactured Vivaldi anten-nas opening.

Several antennas were design basedon previous development by thegroup and simulated in HFSS to in-vestigate the required properties. Animportant property is the polarisa-tion which is often overseen. In re-cent publications only frequency re-sponse and radiation pattern is in-vestigated. In appendix, 8.1, simula-tions results for antennas are shownwith: Model, Frequency Response(S11), 3D-Radiation (dB-rE), Radia-tion Pattern (dB-rE) and PolarisationPattern (Theta/Phi). The frequencyresponse shows the value at -10dBthat is set as the threshold for radia-tion. Radiation pattern is shown forthe main direction at vertical angels,

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Patch Patch+ 4-Patch Vivaldi Split-Lens Array Vivaldi

Bandwidth(GHz at -10dB) 1.21 1.67 1.21 19.91 widePeak Radiation(dB) 24.2 27.4 29.9 25.7 16.9

Table 2: Antenna Simulations Results.

because of different radiation directions and model constructions the angels and coordi-nates are not the same for different antennas. Polarisation Ratio was the only availablemeasurement for polarisation, it is useful to compare how disordered they are and themaximum value of ratio but lacks in that a cross-polarised antennas would show no am-plitude. A summarise is available in table 2 were bandwidth and signal strength is shown.

5.3.1 Patch Antenna

Figure 8: The polarisation ratio of a simple square patch antenna.

A patch antenna was made based on previous work[17] to be used as a reference fortest and development. The patch antenna have a very good polarisation (figure 8) and asimple manufacturing. Simulations are good and show a maximum S11 of -23 dB and asignal width of 1.21 GHz at -10 dB. Radiation is close to symmetric around vertical axisand have small side-lobes.

5.3.2 Modified Patch Antenna

The u-slot antenna(figure 10, antenna arrays (figure 32) and rounded square (9) antennaswere investigated. The U-slot antenna shows a wider polarisation pattern than squareantenna but is still applicable for a parallel-antenna setup. It is a very good candidatefor use in detectors at particle colliders but it requires more analysis to produce reliableresults when done with backplate.

10

Figure 9: An experimental patch antennawith rounded corners.

Rounded square as well as other slot-type show similar or worse polarisationswidths. The simulation of an antenna withstep size was tried but did not give rea-sonable results, this could be caused bythe large number of sharp edges, mak-ing the simulation fail. To counter this abetter design and adjusted simulation set-tings should be tried.

Figure 10: Radiation of an U-slot an-tenna.

Figure 11: The Radiation of 4-patch ar-ray antenna.

The radiation of a simulated 4-array patchantenna is shown in figure 35 and shows quita bad pattern compared to single patch. Whilethe radiation and polarisation(figure 36) resultfor a patch array is bad the gain increase is verygood as can be seen in figure 34 where it goesto 29.9db from 24.2dB.

5.3.3 Bowtie Antenna

The bow-tie antenna (figure 13 shows goodproperties but is hard to simulate with sharpinternal and external angels. It can be a fu-ture contestant, especially as it is smaller than astandard patch antenna at the same frequency.


A Vivaldi-antenna was modelled based on pre-vious work and stencils available for production of antenna. The properties are good andcomparable with other work. Bandwidth is close to 20 GHz and peak radiation is 25.7. Anewer design with a split design allows for the antenna to be fed through a simple patch.The design was tested with a 3-layer balanced and 2-layer unbalanced setup. The un-balanced antenna was unsuccessfully modelled as the fields went out through the sidesof the patch unless a shield was applied around the substrate. This might be caused bythe thin patch/air edge and could be prevented by using a surface element for the patch

11

instead of a solid element. The balanced antenna was produced and shows good proper-ties. The complexity of a 3-layered construction fail to meet the criteria for this project butit is still interesting, especially as a flexible alternative in construction with wired feeds.

5.3.5 Simulated Lens

(a) Radiation.

(b) Model.

Figure 13: Bowtie Antenna.

If the lens is simulated sus-pended above a square patchantenna the performed sim-ulation is limited by itssize. A new model using alumped port system as to al-low more flexible solutionswhere not successfully simu-lated. Simulation can be op-timised as other simulationshave showed much betterproperties.

In simulations the lensincreased bandwidth from1.21 to 1.67 and peak ra-diation with 3dB. There isa clear increase of antennagain with a lens but alsoan increased in side-lobs andwavelength properties thatare important to take into ac-count. The full-cover de-sign of the manufacturedlens could not be replicatedin simulations. The polarisa-tion is affected by the lens,but not to a large degree,change is mostly seen in thereflected directions.

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(a) S11

(b) Gain shown in 3D.

Figure 12: 4-array square-patch antenna.

13

(a) Max gain without lens.

(b) Max gain with lens.

Figure 14: The effect of a lens on a square wave-port.

14

(a) S11 without lens.

(b) S11 with lens.

Figure 15: The effect of a lens on a square wave-port.

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5.4 Antenna Measurement

Measurements from RTO 1024 were the primary resources. A comparison between thesignal recorded only with the SMA-connector and with a, short and long, patch antennamounted is shown in figure 16. The long patch antenna is designed in the same way asthe patch antenna (figure 22) but with twice the length of the feed strip,

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

x 109

−80

−60

−40

−20

0

20

40

60

80

100

120The Messurment when No Antenna is Mounted compared to Mounted

dB

Frequency(1GHz → 60GHz)

Only Mount

Short Patch

Long Patch

Maximum = 39

Maximum = 114

Maximum = 109

Mean

Gain = 39

Gain = 71

Gain = 70

Figure 16: Unmounted Antenna

A small peak can be observed at 1 GHz even when no antenna is mounted. The peakshows a height of ∼ 40 dB compared to the peak for the antenna at ∼ 70 dB. This peakoriginates from the connector acting as antenna or as a resonator in the system. There isalso a clear signal pattern for the antenna which is not visible without, this would indicatethat there is a low antenna affect from the connector.

5.4.1 Patch Antenna

Figure 17: Measurement Short Patch

Simulations for the patch antennas are available in Appendix 8.1.1 and 8.1.3.Ten mea-surements of S11 are shown with a mean of 107.54 dB and std of 1.1473 17. The measure-ments for the short and long patch antenna shows that they have similar properties but

16

that the short antenna performs better with a slightly better efficiency and a lower stdof 1.1473 compared to 2.2427 for the long patch (Figure 18). This effect will need to bevalidated with further investigation.

Figure 18: Comparison Long and Short Patch


The Vivaldi antenna shows good properties that matches literature as can be seen fromFigure 19. The drop at 20 degrees is larger than the simulation would suggest and shouldbe investigated. In Figure 21 the gain of the Vivaldi antenna is at 125 dB, which is 20 dBgreater than the short patch antenna.

Figure 19: Vivaldi Antenna Measurements with std

5.5 Lens Measurement

In Figure 20 the effect of the lens on the directivity can be seen. The measurements weredone on the simulated main direction and then turned 20 deg in the clockwise directionfor patch and horizontal(H) Vivaldi antenna and towards the topside vertical for the ver-tical(V) Vivaldi antenna. At 20 degrees with the Vivaldi antenna the peak is offset from

17

centre frequency which explains the very low result for the antenna measurement. In amajority of the measurements the lens increase the output slightly. The patch antennais performing better over 10 and 20 degrees with the lens. The results seems to indicatethat the lens is more efficient at angels. The result at a straight angle shows only a slightincrease.

Figure 20: Angular Offset with Lens Measurement

5.6 Measurement Comparison

In Figure 21 we can see that the long and short patch antenna shows similar results withthe short patch performing slightly better. The Vivaldi antenna performs much betterthan the patch antennas which is also seen for the simulated antennas.

6 Discussion

6.1 Methodology

The literature review for this thesis where performed for a large amount of antenna de-signs, but only a few antennas where easy to produce in the laboratory. Manufacturingresults were better than expected, especially for the small strips. With a higher qualityetching method, for example a running liquid set-up, better results could be expected.Lens manufacturing was successful but should be further studied to assess quality. Mea-surements of antennas are of varying quality and especially the changing of antennaswas problematic. More connection adaptors and holders should make it possible to accu-rately control the angels and placement of different shaped antennas. More investigationshould be made into the set-up with known antennas to investigate background and sys-tem noise.

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Figure 21: Gain and std of Short, Long and Vivaldi Antenna

6.2 Antennas

The antennas produced show comparable properties to expected results from the simu-lation studies with the limited data available. If a few antennas of each design pair hadbeen produced quality of production would have been assessed, different antennas canbe produced simultaneously and repeatedly to validate production.

6.3 Point-to-point efficiency

The gain varies greatly between antennas and with the use of a lens. The polarisation andpotency for parallel use is not known in this stage.

6.4 Limitations

This study was limited in scope and quantity. Only on production sample of each designwas tested and a limited number of variables were properly optimised in simulations.No absolute and comparable value were measured for any antenna, but the set-up wereconsistent during tests and is reproducible. No theoretical analysis of antennas was, onlyoptimisations through simulation on previous analysis and design was done.

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6.5 Future Studies

In future studies quality of antenna production should be analysed and also comparedto external production. Tolerances should be set for antenna pairs based on radiationmatching and stencil to etching result analysed to allow for more exact productions. Theimpedance matching should be investigated and impedance in on-chip application stud-ied. The properties of the printed lens should be properly investigated to allow a moreexact design of the combined system. Lens geometry should also be investigated in realmeasurements, ellipsoid design and the design of surface closest to antenna should be pri-oritized as well as the position of the lens. Antenna measurements should be increasedand greater focus on absolute and comparable values should be done. Any setup shouldbe done to allow for automated measurements and recording to increase continuity. Test-ing how antennas perform together with a reference antenna and in pairs should be doneto check viability for the reference-antenna setup

7 Conclusion

Five different antennas are simulated and presented. Three antennas were producedbased on previous designs, two patch antennas, with one having double feed length, andone Vivaldi antenna. Production was done using double sided etching of lithographicsheets in a bubble tank. Production was of good quality and matched the stencils to ahigh degree.

The three antennas was measured in an open setup at 60 GHz with the same hornantenna as receiver. The Vivaldi antenna showed the best signal, 20dB greater then thepatch antenna. The double length patch antenna was slightly weaker than the standardpatch antenna, showing a slight loss of performance as the feed structure increases.

An antenna lens was designed and produced using 3D-printing. The lens shows in-creased performance in general. A slight increase in performance at straight angle isshown but results are inconclusive for angular offsets. The results indicate a possibility todesign the lens for the specific angular beam, steering it in a point-to-point application.

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8 Appendix

8.1 Simulated Antennas

8.1.1 Simulations for a simple square-patch antenna

Figure 22: Patch Antenna

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Figure 23: Patch Antenna Frequency

Figure 24: Patch Antenna 3D Polar radiation

22

Figure 25: Patch Antenna Radiation rE

Figure 26: Patch Antenna 3D Polar Ratio

23

8.1.2 Simulations of Patch Antenna with Lens

Figure 27: Patch Antenna with Lens

24

Figure 28: Patch Antenna with Lens Frequency

Figure 29: Patch Antenna with Lens 3D Polar Radiation

25

Figure 30: Patch Antenna with Lens Radiation rE

Figure 31: Patch Antenna with Lens 3D Polar Ratio

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8.1.3 4-Array Patch Antenna

Figure 32: 4-Array Patch Antenna

27

Figure 33: 4-Patch Antenna Frequency

Figure 34: 4-Patch Antenna 3D Polar Radiation

28

Figure 35: 4-Patch Antenna Radiation rE

Figure 36: 4-Patch Antenna 3D Polar Ratio

29


Figure 37: Vivaldi Antenna on substrate

30

Figure 38: Vivaldi Antenna Frequency

Figure 39: Vivaldi Antenna 3D Polar Radiation

31

Figure 40: Vivaldi Antenna Radiation rE

Figure 41: Vivaldi Antenna 3D Polar Ratio

32

8.1.5 Split Vivaldi Antenna

Figure 42: Split Vivaldi Antenna

33

Figure 43: Split Vivaldi Antenna Frequency

Figure 44: Split Vivaldi Antenna 3D Polar Radiation

34

Figure 45: Split Vivaldi Antenna Radiation rE

Figure 46: Split Vivaldi Antenna 3D Polar Ratio

35

8.2 Screenshots from RTO 1024

Figure 47: Patch antenna at 0


36



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8.3 Table of article

Table 3: Table of antenna designs

Reference AntennaFrequency(GHz) )

Bandwidth(GHz)

Bandwidth(%)

Max gain(dB) Feed type

Aaron Zachary Hood Antipodal Vivaldi 6,5 7,5 115,38 5 Feed lineAbdul Muqeet Wideband microstrip 40 30 75 11,53 ProbeB.-K. Ang E-shaped microstrip 5,5 0,83 15,09 8,1 ProbeBehzad Biglarbegian 2x2 patch 60 3,5 5,83 13,25 ProbeC. Karnfelt 2x5 patch 60 0,8 1,33 14,6 Feed lineEMCoS Antipodal Vivaldi 15 15 100 4,75 Feed lineFlorian Ohnimus Center-fed slot 60 7 11,67 6,4 CPWGreg Brzezina Antipodal Vivaldi 60 13 21,67 6,5 Feed lineHussein Mahmoud Slotted overlapped patch 6 3,79 63,17 (empty) ProbeM. S. Alam Wideband Microstrip 60 15,4 25,67 9,52 ProbeM. S. R Mohd Shah Dual Polarised 2x2 2,5 0,09 3,61 3,57 Probe

Mohamed HayouniConvex corners circularslot patch 6 9 150 7,2 Feed line

T. Shanmuganantham CPW-Fed Slot 6 3,31 55,17 4,39 CPWWaleed Tariq Horn 60 7,14 11,9 11,65 Feed line

Bibliography

[1] Tuncer Baykas, Chin-Sean Sum, Zhou Lan, Junyi Wang, M. Rahman, Hiroshi Harada, and ShuzoKato. IEEE 802.15.3c: the first IEEE wireless standard for data rates over 1 gb/s. IEEE CommunicationsMagazine, 49(7):114–121, July 2011.

[2] Behzad Biglarbegian, Mohammad Fakharzadeh, Dan Busuioc, Mohammad-Reza Nezhad-Ahmadi,and Safieddin Safavi-Naeini. Optimized microstrip antenna arrays for emerging Millimeter-Wavewireless applications. IEEE Transactions on Antennas and Propagation, 59(5):1742–1747, May 2011.

[3] Marko Bosiljevac, Massimiliano Casaletti, Francesco Caminita, Zvonimir Sipus, and Stefano Maci.Non-Uniform metasurface luneburg lens antenna design. IEEE Transactions on Antennas and Propa-gation, 60(9):4065–4073, September 2012.

[4] Greg Brzezina, Rony E. Amaya, Aldo Petosa, and Langis Roy. Vivaldi antenna for MM-wave com-munications. Technical report, High Frequency Electronics, 2014.

[5] Alina-Cristina Bunea, Dan Neculoiu, Andrei Avram, and Christian Rusch. Investigation of a mem-brane supported D-Band antenna with a 3D printed polyamide lens, November 2014.

[6] Shi Cheng. Integrated antenna solutions for wireless sensor and millimeter-wave systems, 2009.

[7] Shi Cheng, P. Hallbjorner, and A. Rydberg. Printed slot planar inverted cone antenna for ultrawide-band applications. IEEE Antennas and Wireless Propagation Letters, 7:18–21, 2008.

[8] Henry A. Diawuo, Sung J. Lee, and Young-Bae Jung. Sidelobe-level reduction of a linear arrayusing two amplitude tapering techniques. IET Microwaves, Antennas & Propagation, 11(10):1432–1437,August 2017.

[9] DanielF Filipovic and GabrielM Rebeiz. Double-slot antennas on extended hemispherical and ellip-tical quartz dielectric lenses. 14(10):1905–1924, 1993.

[10] Mohamed Hayouni, Fethi Choubani, Tan H. Vuong, and Jacques David. Design and analysis ofa compact printed UWB antenna using non uniform matching and Half-Wavelength circular slot.International Journal of Electromagnetics and Applications, 2(6):145–150, 2012.

[11] A. Z. Hood, T. Karacolak, and E. Topsakal. A small antipodal vivaldi antenna for Ultrawide-Bandapplications. IEEE Antennas and Wireless Propagation Letters, 7:656–660, 2008.

[12] C. Karnfelt, P. Hallbjorner, H. Zirath, P. Ligander, K. Boustedt, and A. Alping. High gain activemicrostrip antenna for 60 GHz WLAN. In 2005 European Microwave Conference, pages 4 pp.+. IEEE,2005.

[13] Pramod Kumar, Deepak Batra, Shrivastav, and Vol. 4. high gain microstrip antenna capacitivelycoupled to a square ring with surface mounted conical horn. 2010.

38

[14] Xian Ling. Ultra-Wideband Antenna and Design, chapter 12. InTech, October 2012.

[15] Science Team NASA/WMAP. Wmap 9-year results released, August 2013.

[16] C. Schulz, C. Baer, N. Pohl, T. Musch, B. Will, and I. Rolfes. A multi directional dielectric lensapproach for antennas used in industrial RADAR applications. In 2013 International Workshop onAntenna Technology (iWAT), pages 328–331. IEEE, March 2013.

[17] Haekyo Seo, Wonbin Hong, and Dong Gun Kam. Gain variation of 60-GH z patch antennas due toground plane dimensions. Microwave and Optical Technology Letters, 58(4):745–747, April 2016.

[18] Waleed T. Sethi, Hamsakutty Vettikalladi, and Majeed A. Alkanhal. Millimeter wave antenna withmounted horn integrated on FR4 for 60 GHz gbps communication systems. International Journal ofAntennas and Propagation, 2013:1–5, 2013.

[19] T. Shanmuganantham, K. Balamanikandan, and S. Raghavan. CPW-fed slot antenna for widebandapplications. International Journal of Antennas and Propagation, 2008:1–4, 2008.

[20] Duo Wang, Raphael Gillard, and Renaud Loison. A 60GHz passive repeater with endfire radiationusing dielectric resonator antennas. In 2014 IEEE Radio and Wireless Symposium (RWS), pages 31–33.IEEE, January 2014.

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design and test of: wide band and highly polarized...

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