Optimization of aperture coupled microstrip patch antennas

Aperture coupled microstrip patch antennas (ACMPA) are special class of microstrip antennas with high gain and wide impedance bandwidth. These antennas differ from other microstrip antennas with their feeding structure of the radiating patch element. Input signal couples to the radiating patch through the aperture that exists on the ground plane of the microstrip feedline. These special antennas are multilayer stacked type of antennas with so many design variables that will affect the antenna performance. This paper presents the design and optimization procedure of ACMPA while taking care of all possible design variables and parameters to get the highest possible antenna gain and minimum VSWR

Dielectric measurement based microstrip transmission line

The measurement of complex dielectric properties of materials at radio frequency is very important especially in the research fields, such as material science, microwave circuit design, absorber development, biological research, etc. Dielectric measurement is important because it can provide the electrical and magnetic characteristics of the materials, which proved useful in many research and development fields.The proposed technique present a simple microstrip transmission line method for the broadband radio frequency characterization of dielectric constant of non-dispersive materials. A microstrip line having impedance other than 50 Ω is designed and material under test is used as the substrate. The impedance mismatch between a non-50 Ω characteristic impedance of the microstrip line and 50 Ω coaxial to microstrip connectors generates significant reflection/transmission at the input ports. The mismatch between the input impedance and port is used to extract the dielectric constant of the substrate. For experimental validation, the microstrip trace is sticked on the test substrate which are FR4, Teflon and Roger 5880. During the measurement, the microstrip line is connected to vector network analyser through SMA connectors. It is found that this technique introduce error of 10.83%, 7.53% and 21.32% for FR4, Teflon and Roger 5880 respectively. On the other hand, the comparison with the experimental measurement shows 13.5%, 52.95% and 31.40% of error for FR4, Teflon and Roger 5880 respectively. The future research, can focus on measuring the dielectric properties of dispersive material including its loss factor material based on Kramers-kronig relationship

An efficient 1-D periodic boundary integral equation technique to analyze radiation onto straight and meandering microstrip lines

A modeling technique to analyze the radiation onto arbitrary 1-D periodic metallizations residing on a microstrip substrate is presented. In particular, straight and meandering lines are being studied. The method is based on a boundary integral equation, more specifically on a mixed potential integral equation (MPIE), that is solved by means of the method of moments. A plane wave excites the microstrip structure, and according to the Floquet-Bloch theorem, the analysis can be restricted to one single unit cell. Thereto, the MPIE must be constructed using the pertinent 1-D periodic layered medium Green's functions. Here, these Green's functions are obtained in closed form by invoking the perfectly matched layer paradigm. The proposed method is applied to assess the radiation onto 1) a semi-infinite plate, 2) a straight microstrip line, and 3) a serpentine delay line. These three types of examples clearly illustrate and validate the method. Also, its efficiency, compared to a previously developed fast microstrip analysis technique, is demonstrated

Thin conformal antenna array for microwave power conversions

A structure of a circularly polarized, thin conformal, antenna array which may be mounted integrally with the skin of an aircraft employs microstrip elliptical elements and interconnecting feed lines spaced from a circuit ground plane by a thin dielectric layer. The feed lines are impedance matched to the elliptical antenna elements by selecting a proper feedpoint inside the periphery of the elliptical antenna elements. Diodes connected between the feed lines and the ground plane rectify the microwave power, and microstrip filters (low pass) connected in series with the feed lines provide dc current to a microstrip bus. Low impedance matching strips are included between the elliptical elements and the rectifying and filtering elements

Microstrip Patch Antennas Fed by Substrate Integrated Waveguide

Dizertační práce je zaměřena na výzkum mikropáskových flíčkových antén a anténních řad napájených vlnovodem integrovaným do substrátu (SIW). Využitím vlnovodu integrovaného do substrátu pro napájení mikropáskové flíčkové antény dochází ke kombinaci výhodných vlastností obou struktur. Výsledkem je kompaktní anténní struktura, jejíž napájecí vedení neprodukuje parazitní záření a neovlivňuje tak vyzařovací charakteristiku antény. Práci lze z věcného hlediska rozdělit do dvou částí. První část práce (kapitola 2) je zaměřena na návrh flíčkových antén a jejich navázání na vlnovod integrovaný do substrátu. První dvě navržené flíčkové antény využívají vlnovod integrovaný do substrátu a štěrbinu nebo koaxiální sondu pro buzení lineárně polarizované vlny. Napájení koaxiální sondou je dále použito pro buzení kruhově polarizované flíčkové antény. Za účelem získání širšího pásma osového poměru je navrženo napájení flíčkové antény ve dvou bodech. Funkčnost všech anténních struktur je popsána pomocí parametrických simulací a ověřena realizací a měřením vyrobených prototypů antén. Prezentované napájecí metody představují nový způsob napájení pro mikropáskové antény využívající technologii SIW. Ve druhé části práce (kapitola 3) je pojednáno o implementaci štěrbinou napájené mikropáskové anténní struktury do malých anténních polí o velikosti 2x2 a 1x4. V případě lineární řady je uvažováno amplitudové rozložení pro optimální potlačení postranních laloků. Obě navržené anténní řady jsou ověřeny měřením a v porovnání s podobnými anténními řadami dostupnými v literatuře dosahují širšího pracovního pásma kmitočtů a vyššího zisku.The thesis deals with the research of microstrip patch antennas and antenna arrays fed by a substrate integrated waveguide (SIW). Exploiting an SIW structure for microstrip patch antenna feeding combines the benefits of both structures. The result is a compact antenna structure retaining advantageous properties of microstrip patch antennas and having a radiation characteristic non-effected by spurious radiation which is usually produced by a conventional feeding line. The thesis consists of two factual parts. The first one (Chapter 2) deals with the design of microstrip patch antennas and exploiting a substrate integrated waveguide for their feeding. The first two microstrip patch antennas exploit an SIW and a slot or a coaxial probe in order to excite a linearly-polarized wave. SIW-based probe feeding is further utilized for exciting a single- and dual-fed circularly-polarized microstrip patch. The functionality of the proposed antenna structures is described using parametric analyses and verified by measuring of fabricated prototypes. The proposed feeding methods represent a novel feeding approach for microstrip patch antennas exploiting SIW technology. The second part of the thesis (Chapter 3) deals with implementing the linearly-polarized aperture-coupled microstrip patch antenna structure fed by SIW into two small antenna arrays consisting of 2x2 and 1x4 radiators. An amplitude distribution is considered in the case of the linear antenna array for optimum suppression of side lobes. Both proposed antenna arrays are verified by measurements. Compared to similar antenna arrays available in the literature, they reach a wider operating frequency band and a higher gain.

Modeling of the excited modes in inverted embedded microstrip lines using the finite-difference time-domain (FDTD) technique

This thesis investigates the presence of multiple (quasi-TEM) modes in inverted embedded microstrip lines. It has already been shown that parasitic modes do exist in inverted embedded microstrips due to field leakage inside the dielectric substrate, especially for high dielectric constants (like Silicon). This thesis expands upon that work and characterizes those modes for a variety of geometrical dimensions. Chapter 1 focuses on the theory behind the different transmission line modes, which may be present in inverted embedded microstrips. Based on the structure of the inverted embedded microstrip, the conventional microstrip mode, the quasi-conventional microstrip mode, and the stripline mode are expected. Chapter 2 discusses in detail the techniques used to decompose the total probed field into the various modes present in the inverted embedded microstrip lines. Firstly, a short explanation of the finite-difference time-domain method, that is used for the simulation and modeling of inverted microstrips up to 50 GHz is provided. Next, a flowchart of the process involved in decomposing the modes is laid out. Lastly, the challenges of this approach are also highlighted to give an appreciation of the difficulty in obtaining accurate results. Chapter 3 shows the results (dispersion diagrams, values/percentage of the individual mode energies ) obtained after running time-domain simulations for a variety of geometrical dimensions. Chapter 4 concludes the thesis by explaining the results in terms of the transmission line theory presented in Chapter 1. Next, possible future work is mentioned.M.S.Committee Chair: Tentzeris, Emmanouil; Committee Member: Andrew Peterson; Committee Member: Laskar, Joy; Committee Member: Papapolymerou, Ioanni

A study of water-mist recirculation system for filtration and cooling effect in the kitchen hood ventilation system

Water-mist spray system in several heavy-duty kitchen hood canopies are installed to efficiently control the high heat loads and grease emissions produced from the cooking process and for safety purposes. Cold water is used in the water�mist system and work as a mist curtain inside the exhaust plenum of the canopy. The main purpose of this study is to reduce the water consumption by introducing the water-mist recirculation system to replace the current method water-mist system since it is working as water loss. A standard ASTM 2519 and UL 1046 full-scaled experiment was developed in the laboratory. An existing Halton Europe/Asian water�mist operating system was adopted in this study. Twelve (12) cycles (at 24 hours water-mist activation) has been studied to determine the maximum water-mist activation cycle. The data was collected at two (2) hours water-mist activation at every water-mist recirculation cycle. The water-mist spray fluids viscosity is 0.7 cP from fresh water until the 4th cycle (8 hours water-mist spray) and increase 14.29% (0.8 cP) at 5th cycle to 12th cycle. On average, the difference in gas emissions percentage for CO concentration between fresh water until 4th cycle is 10.81 – 18.92% while the CO2 concentration is 12.33 – 18.22%. On average, the difference in cooling effects percentage for ducting temperature between fresh water until 4th cycle was 5.55% while the hood temperature was 2.33%. From the study, the water-mist recirculation system could save up to 611,667 liter per year and 466,798.5 liter per year water for all U.S, European, and Asian kitchen hood designs per hood length. By adopting the new water-mist recirculation system to the current water-mist kitchen hood, the water operational cost for water successfully reduced to RM 4,889.63 per year and RM 6,977.86 per year for U.S design and European or Asian design per hood length respectively. The water-mist recirculation system has great potential to improve the current water-mist system for the commercial kitchen hoo

Structural behaviour of beam with HDPE plastic balls subjected to flexure load

This paper presents the structural behavior of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results are analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failur