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In the lower millimetre-wave frequency range, Substrate Integrated Waveguide (SIW) circuits have emerged as a reasonable compromise between rectangular waveguide and standard microstrip technologies. They are formed by a top- and bottom-metalized substrate and two arrays of plated or riveted holes (via holes) to replace the vertical metallic walls in conventional rectangular waveguide. Although many passive components known from traditional waveguide technology have been fabricated in SIW, one of the main challenges is to integrate active components with typical coaxial-type interfaces within the SIW environment. Therefore, the work presented in this dissertation focuses on new broadband transitions from SIW to other planar transmission-line technologies such as microstrip coplanar waveguide, coplanar strip line, slot line and coupled microstrips. Several of the new transitions are prototyped and experimentally verified. Two of these transitions are then used to integrate a low noise amplifier within SIW input and output ports. The measurements of fabricated SIW amplifier prototypes show very promising performance and clearly demonstrate successful integrations of active components within SIW. Finally, one of the new SIW-to-coplanar-waveguide transitions is employed as an interface to an SIW-based antenna, thus demonstrating the principle of connectivity of SIW to all currently used planar circuit technologies. / Graduate

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Traditional radio astronomy imaging techniques assume that the interferometric array is coplanar, with a small field of view, and that the two-dimensional Fourier relationship between brightness and visibility remains valid, allowing the Fast Fourier Transform to be used. In practice, to acquire more accurate data, the non-coplanar baseline effects need to be incorporated, as small height variations in the array plane introduces the w spatial frequency component. This component adds an additional phase shift to the incoming signals. There are two approaches to account for the non-coplanar baseline effects: either the full three-dimensional brightness and visibility model can be used to reconstruct an image, or the non-coplanar effects can be removed, reducing the three dimensional relationship to that of the two-dimensional one. This thesis describes and implements the w-projection and w-stacking algorithms. The aim of these algorithms is to account for the phase error introduced by non-coplanar synthesis arrays configurations, making the recovered visibilities more true to the actual brightness distribution model. This is done by reducing the 3D visibilities to a 2D visibility model. The algorithms also have the added benefit of wide-field imaging, although w-stacking supports a wider field of view at the cost of more FFT bin support. For w-projection, the w-term is accounted for in the visibility domain by convolving it out of the problem with a convolution kernel, allowing the use of the two-dimensional Fast Fourier Transform. Similarly, the w-Stacking algorithm applies a phase correction in the image domain to image layers to produce an intensity model that accounts for the non-coplanar baseline effects. This project considers the KAT7 array for simulation and analysis of the limitations and advantages of both the algorithms. Additionally, a variant of the Högbom CLEAN algorithm was used which employs contour trimming for extended source emission flagging. The CLEAN algorithm is an iterative two-dimensional deconvolution method that can further improve image fidelity by removing the effects of the point spread function which can obscure source data. / AFRIKAANSE OPSOMMING: Tradisionele beeldvormingstegnieke in radio-astronomie aanvaar dat die interferometriese skikking samevlakkig is. Dit beteken dat die twee-dimensionele Fourier verhouding tussen helderheid en sigbaarheid geldig bly en dat die Vinnige Fourier Transform aangewend kan word. Klein hoogtevariasies in die skikkingsvlak bring die w-ruimtelike frekwensiekomponent mee, wat ’n faseverskuiwing in die inkomende seine tot gevolg het. Dus, in praktyk, moet die bydrae van die nie-samevlakkige basislyneffekte in ag geneem word om sodoende die akkuraatheid van die data te verhoog. Twee benaderings kan gevolg word om die nie-samevlakkige basislyneffekte in ag te neem: Metodes wat die volle drie dimensionele helderheid en sigbaarheidsmodel gebruik kan toegepas word om ’n beeld te herbou, andersins kan die nie-samevlakkige effekte verwyder word om sodoende die drie-dimensionele verhouding te verminder tot ’n twee-dimensionele verhouding. Hierdie tesis beskryf en implementeer die ‘w-projeksie’ en ‘w-stapel’ algoritmes. Die doel van hierdie algoritmes is om die fasefout wat deur nie-samevlakkige sinteseskikkingskonfigurasies veroorsaak word, reg te stel. Hierdie regstelling maak die herwinde sigbaarheid van die beeld meer getrou aan die werklike helderheidsverspreidingsmodel. ’n Bykomende voordeel van die algoritmes is beeldvorming van wye-veld ruimtewaarnemings. In ‘w-projection’ word die w-term in die sigbaarheidsdomein in ag geneem deur die ruimtelike frekwensiekomponent met behulp van ’n konvolusiekern vanuit die probleem te verwyder. Die twee-dimensionele Vinnige Fourier Transform kan gevolglik toegepas word. Soortgelyk hieraan, wend die ‘w-Stacking’ algoritme ’n fasekorreksie aan tot ’n reeks beeldlae, om sodoende ’n beeld te verkry wat die nie-samevlakkige basislyneffekte in ag neem. Die KAT7 teleskoop is gebruik in die simulasie en analiese van die tekortkominge en voordele van beide algoritmes. ’n Hibriede weergawe van die Högbom CLEAN algoritme is bykomend oorweeg. Hierdie algoritme is ’n iteratiewe twee-dimensionele dekonvolusiemetode wat die betroubaarheid van beelde verbeter deur die verskansingseffek van puntverspreidingsfunksies te verwyder. Verder gebruik die Högbom CLEAN algoritme kontoersnoeiing om uitgebreide bron-emisies te identifiseer.

A guided-wave THz System-on-Chip (TSoC) is emerging as an attractive alternative to the routine free-space THz systems to reduce physical bulk, propagation loss, pulse dispersion and cost of free-space THz systems. Recently, our research group succeeded in demonstrating a novel waveguided TSoC based on the coplanar stripline (CPS) transmission lines on a 1 µm-thin Silicon Nitride membrane. The novelty of this membrane-based platform was bonding the transmitter and receiver directly on the transmission line to eliminate the radiation loss by the routine THz optics. Besides, the delicate thin-membrane dramatically reduces the dielectric loss of the platform which results in low-loss and low-dispersion THz-bandwidth pulses. This Ph.D. dissertation presents the first end-to-end TSoC components that were designed and fabricated using the CPS transmission lines on 1 µm-thin Si3N4 membranes. These components are integrated into a TSoC by bending or connecting different impedance CPS transmission-line sections. We demonstrate four passive TSoC components: THz low-pass filter (TLPF), THz power divider (TPD), THz apodized Bragg grating (TABG) and THz branch-line coupler (TBLC). One of the most significant gains from this work is the assurance that more complex TSoCs can be designed and fabricated using this membrane-platform based on the strong agreement between simulation and experimental results. / Graduate / 2021-12-01

Investigation of the Double-Y Balun for Feeding Pulsed Antennas Jaikrishna Venkatesan 232 Pages Directed by Dr. Waymond Scott, Jr. In this research, a double-y balun implemented with coplanar waveguide (CPW) and coplanar strip (CPS) was investigated for use with pulsed antennas. The balun was modeled using two commercial electromagnetic simulators: Momentum and HFSS. Using these numerical solvers, design information such as the design of CPW bridges, aspect ratio of the double-y balun, and stub lengths of the CPW and CPS open and short stubs were studied. A dipole, along with the outer conductor of a coaxial line was modeled in NEC. The model was used to study the currents along the arms and feedline of balanced and unbalanced dipoles. Normalized amplitude patterns were generated along the azimuth and elevation planes for balanced and unbalanced dipoles. These patterns were used later for comparison with measured patterns. Experimental work was conducted to measure the performance of a double-y balun designed to feed a resistively loaded V-dipole. The performance of the balun was investigated via VSWR, insertion loss, and antenna pattern measurements. Antenna pattern measurements along the azimuth plane were conducted for a 5 cm dipole fed without a balun, a 5 cm dipole fed with the double-y balun, a 5 cm dipole fed with the sleeve balun, a 12 cm dipole fed without a balun, and a 12 cm dipole fed with the double-y balun. The dipoles fed without a balun were fed directly with a 50 W coaxial line. An optical link, consisting of a laser modulator (LM) unit and a laser receiver (LR) unit, was constructed to measure the patterns along the elevation plane of the above dipoles. Resulting patterns agreed closely with patterns generated with NEC models. In addition, the patterns of a resistively loaded V-dipole were measured along the E-plane using the optical link. The measured patterns for the V-dipole were compared with numerical results obtained from literature. The experimental work conducted in this research illustrates the improvement obtained in the patterns of a dipole and a resistively loaded V-dipole with the use of the double-y balun.

This thesis deals with coplanar directional and hybrid couplers. Firstly, the thesis describes the theory of hybrid microwave integrated circuits with their advantages and disadvantages in comparison with other types of microwave circuits. Next, the thesis deals with basic microstrips and individual types of coplanar strips and waveguides are also more closely analyzed. The thesis also explains a theory of directional and hybrid couplers and analyses particular kinds of directionality and attributes of the real directional couplers. The following chapter shows a method of design of a few coplanar directional coupler types. Attributes of the types are then verified in CST Microwave Studio. The last chapter includes measured parameters of the couplers and their comparison with the theoretical values from the previous part. The next aim of the thesis is to create laboratory tasks which deals with coplanar directional couplers. The laboratory task is found in the appendix.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / In this article we present a design of an L-band slot loop antenna with a dielectric loaded conductor backed coplanar waveguide (CBCPW) feed. The coplanar slot loop antenna has a transmission line resonator in series. We used full wave electromagnetic simulations with Ansoft's high frequency structure simulator (HFSS) software in the design of the coplanar slot loop antenna. The series transmission line resonator helps to tune the coplanar slot loop antenna and reduce its size. We present here results on return loss and radiations patterns of coplanar slot loop antenna obtained from HFSS simulations.

<p>The objective of this thesis is to evaluate a generic process for fabrication and characterization of the Superconductive coplanar waveguide (CPW) resonators. Superconductive CPW resonators with various lengths and shapes are designed to investigate their electrical and magnetic properties as well as resonance properties and sensitivities. In the first part of thesis, two different models are introduced in order to estimate the nonlinear kinetic inductance of a superconducting CPW resonator. The first model is based on Bean critical-state model and the second one is based on current dependence of London penetration depth. The existence of a shift in resonant frequency  of Superconductive CPW resonator caused by a non-linear kinetic inductance is also shown experimentally. Simulations were carried out to estimate the nonlinear kinetic inductance due to the self- induced magnetic field penetration.</p><p>The rest of the thesis is concerned with development of very smooth Aluminum (Al) thin films with RMS (Root Mean Square) roughness 1~nm and CAD (Computer Aid Design) of superconductive CPW resonators. Experimental investigation of a generic fabrication technique for superconductive CPW resonator is carried out. Many resonators are fabricated with different design parameters, such as centerline or gap width, film thickness and gap capacitors length. The fabrication process is described in detail. Electron Beam Lithography is used to fabricate Nb and Al CPW resonators which are coupled to outer conductors via gap capacitors. We have fabricated GHz frequency CPW resonators with quality factors, Q up 5X10^5.</p>

Approved for public release; distribution is unlimited / A general study of conductor backed coplanar waveguide is presented. The impedance (Z(0)) and effective dielectric constant (ɛ(reff)) of conductor-backed coplanar waveguide (CBCPW) have been calculated by using a variational method and the boundary point matching method. In this present work only the TEM dominant low frequency propagation mode of coplanar line has been considered. Experimental facilities are vector network analyzer (HP8409) and bench-instrument measurements. / http://archive.org/details/evaluationofcopl00jeon / Captain, Korean Air Force

With a rapid increase in information capacity of Internet access, high-speed, highly-efficiency, and cost-effectiveness laser source for optical fiber communication is required. High-speed 25Gb/s directly modulated laser is essential of this communication range, because of its simple structure, direct-modulation characteristics, low cost, and integration capability for wavelength division multiplexing (WDM) system, and moreover, it can achieved 100Gb/s data transmission by four channel module system. In this work, data modulation speed of 25Gb/s direct modulation DFB laser has been achieved. By employing high-speed coplanar waveguide structure with semi-insulating substrate, high-speed with f3dB > 20GHz has been demonstrated. By the electrical reflection measurement, it confirmed that the high-speed direction modulation can be realized through reduction of electrical parasitics. The laser chips is measured under continuous-wave mode at room temperature. In 1300nm and 1550nm wavelength device, slope efficiency obtained by taper fiber coupled of 0.045 and 0.07mW/mA respectively, output power up to 2.73 and 3.96mW/facet at 60mA. The Side Mode Suppression Ratio was greater than 35dB. 3dB bandwidth of greater than 16GHz and 20.5GHz, relaxation oscillation frequency of 12GHz and 16.6GHz. Finally, clearly back-to-back 25Gb/s eye diagram and error-floor-free performance were obtained.