Straight Antenna Research Articles

BROADBAND MODIFIED RECTANGULAR MICROSTRIP PATCH ANTENNA USING STEPPED CUT AT FOUR CORNERS METHOD

In this paper, a new method that called the Stepped Cut at Four Corners is introduced to design a multi-mode/broadband modified rectangular microstrip patch antennas (MRMPAs). In order to become acquainted with the new method, the design process of a monopole broadband MRMPA suitable for multifunctional wireless communication bands is explained. The methodology of the proposed broadband MRMPA design is presented in six stages. The first stage is designing a single-mode RMPA. Subsequently, by creating a step at the corners using the proposed method a dual-mode antenna is obtained at the second stage, while the triple-mode and multi-mode antennas are designed, at the third and fourth stages respectively. Two types of broadband antennas are obtained, the stepped line and straight line antennas. By increasing the number of steps, the antenna's operating bandwidth (BW), with return loss less than -lOdB, covers the frequency range from 900 MHz to 2.6 GHZ, which is suitable for GSM (900 MHz and 1.5 GHz), WiFi (2.4 GHz) and LTE (2.6 GHz) applications. In addition, the antenna prototype has been fabricated and measured in the all stages, in order to validate the simulation results, and there is a close agreement between the simulated and measured results

Effect of Frequency on Hydrocarbon (HC) Detection Using 3D Finite Integral Modeling

Detection of hydrocarbon in sea bed logging (SBL) is still a very challenging task for deep target reservoirs. The response of electromagnetic (EM) field from marine environment is very low and it is very difficult to predict deep target reservoirs below 2500 m from the sea floor. Straight antennas at 0.125 Hz and 0.0625 Hz are used for the detection of deep target hydrocarbon reservoirs below the seafloor. The finite integration method (FIM) is applied on 3D geological seabed models. The proposed area of the seabed model (16 km ×16 km) was simulated by using CST (computer simulation technology) EM studio. The comparison of different frequencies for different target depths was done in our proposed model. Total electric and magnetic fields were applied instead of scattered electric and magnetic fields, due to its accurate and precise measurements of resistivity contrast at the target depth up to 3000 m. From the results, it was observed that straight antenna at 0.0625 Hz shows 50.11% resistivity contrast at target depth of 1000 m whereas straight antenna at 0.125 Hz showed 42.30% resistivity contrast at the same target depth for the E-field. It was found that the E-field response decreased as the target depth increased gradually by 500 m from 1000 m to 3000 m at different values of frequencies with constant current (1250 A). It was also investigated that at frequency of 0.0625 Hz, straight antenna gave 7.10% better delineation of hydrocarbon at 3000 m target depth. It was speculated that an antenna at 0.0625 Hz may be able to detect hydrocarbon reservoirs at 4000 m target depth below the seafloor. This EM antenna may open a new frontier for oil and gas industry for the detection of deep target hydrocarbon reservoirs below the seafloor.

Electromagnetic Response Studies of the Antenna for Deep Water Deep Target CSEM Environments

The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).

Modeling of Antenna for Deep Target Hydrocarbon Exploration

Nowadays control source electromagnetic method is used for offshore hydrocarbon exploration. Hydrocarbon detection in sea bed logging (SBL) is a very challenging task for deep target hydrocarbon reservoir. Response of electromagnetic (EM) field from marine environment is very low and it is very difficult to predict deep target reservoir below 2 km from the sea floor. This work premise deals with modeling of new antenna for deep water deep target hydrocarbon exploration. Conventional and new EM antennas at 0.125 Hz frequency are used in modeling for the detection of deep target hydrocarbon reservoir. The proposed area of the seabed model (40 km ′ 40 km) was simulated by using CST (computer simulation technology) EM studio based on Finite Integration Method (FIM). Electromagnetic field components were compared at 500 m target depth and it was concluded that Ex and Hz components shows better resistivity contrast. Comparison of conventional and new antenna for different target depths was done in our proposed model. From the results, it was observed that conventional antenna at 0.125 Hz shows 70%, 86% resistivity contrast at target depth of 1000 m where as new antenna showed 329%, 355% resistivity contrast at the same target depth for Ex and Hz field respectively. It was also investigated that at frequency of 0.125 Hz, new antenna gave 46% better delineation of hydrocarbon at 4000 m target depth. This is due to focusing of electromagnetic waves by using new antenna. New antenna design gave 125% more extra depth than straight antenna for deep target hydrocarbon detection. Numerical modeling for straight and new antenna was also done to know general equation for electromagnetic field behavior with target depth. From this numerical model it was speculated that this new antenna can detect up to 4.5 km target depth. This new EM antenna may open new frontiers for oil and gas industry for the detection of deep target hydrocarbon reservoir (HC).

Quadrature method for cylindrical wire antenna

The distributed current in the straight cylindrical antenna can be obtained by solving the Hallen equation with certain unknown constants. In this paper the Hallen equation is reduced to a Cauchy singular integral equation (CSIE). Quadrature method is then applied to the CSIE to obtain a linear system of equations. This approach enables to resolve the unknown constants with the condition that the current vanishes at the ends. This alternative approach is now well posed. A couple of examples are worked out and distributed current is computed.

On the Oscillations Appearing in Numerical Solutions of Solvable and Nonsolvable Integral Equations for Thin-Wire Antennas

Differences between certain solvable and nonsolvable ill-posed integral equations, with the same nonsingular kernel, are discussed. The main results come from constructing a solvable equation in the context of straight thin-wire antennas. The kernel of this equation is the usual approximate (also called reduced) kernel, while its exact solution is the familiar sinusoidal current. Numerical solutions to this solvable equation are compared to corresponding numerical solutions of the usual-Halle¿n and Pocklington-equations with the approximate kernel; it is known from previous publications that these last two equations are nonsolvable and that their numerical solutions present severe oscillations when the number of basis functions is sufficiently large. It is found that the difficulties encountered in the former (solvable) equation are much less important compared to those of the nonsolvable ones. The same conclusion is brought out from other integral equations, arising in different contexts (thin-wire circular-loop antenna, Method of Auxiliary Sources, and straight wire antenna of infinite length). We discuss the consistency of our results with Picard's theorem. The results in this paper supplement previous publications regarding the difficulties of numerically solving thin-wire integral equations with the approximate kernel.

FM 라디오 수신을 위한 차량용 다이버시티 안테나 설계

In this paper, we report on the channel capacity and diversity gain of the vehicle on-glass antenna for FM radio reception. The correlation coefficient and channel capacity were obtained using the simulated 3D radiation pattern of each antenna and the Rayleigh channel model for urban environment. To examine the channel capacity we used two antennas which are a simple straight antenna and L-type antenna. Then we observed the available channel capacity by varying the position of feeds and the shape of the L-type antenna. The sample antenna, which has a maximum feed distance with different polarizations, was built and the receiving performance was measured in the weak FM field area. From the results we confirmed that the distance between the feeds should be placed as far as possible for the high channel capacity. If the distance between the feeds are greater than a certain threshold value than the polarizations of the two antennas are getting more important for determining the channel capacity.

On the Use of Nonsingular Kernels in Certain Integral Equations for Thin-Wire Circular-Loop Antennas

Fundamental properties of certain popular integral equations for thin-wire circular-loop antennas with nonsingular kernels are studied. The cornerstone of our study is a large-asymptotic formula for the n'th Fourier coefficient of the nonsingular kernel. Four different methods of driving the circular loop are considered; namely, the delta-function generator, the finite-gap generator, a certain type of frill generator, and the case of plane-wave incidence. The excitation model is crucial to our discussions, since it determines the behavior of the solution convergence. Also discussed are associated difficulties that may arise when moment methods are applied to the aforementioned equations, as well as a simple improvement to the Fourier-series method for determining the current in the case of the frill generator. The main results herein closely parallel recent results for the case of the straight antenna, and similarities and differences between the straight and circular cases are discussed.

Conformal metal thin-film coatings in high-aspect-ratio trenches using a self-sputtered rf-driven plasma source

A thin-film coating system has been developed for the deposition of both conductive and insulating materials. The system employs a radio-frequency (rf)-discharge plasma source with four straight rf antennas, which is made of or covered with the deposition material, thus serving simultaneously as a sputtering target. The average deposition rate of the copper thin film can be as high as 500nm∕min when operated under continuous-wave mode. Film properties under different operating conditions (gas pressure and rf power) have been investigated experimentally. Three thin-film coating schemes have been developed, one of which has been demonstrated to be suitable for conformal deep-trench coating. Conformal coating over trenches of high-aspect ratio (>6:1) has been demonstrated at both micron and submicron scales.

Thin film passivation of organic light emitting diodes by inductively coupled plasma chemical vapor deposition

The characteristics of an SiN x passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of ∼ 10 11 electrons/cm 3 formed by nine straight antennas connected in parallel, a high-density SiN x passivation layer was deposited on a transparent Mg–Ag cathode at a substrate temperature of 40 °C. Even at a low substrate temperature, single SiN x passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 × 10 − 2 g/m 2/day and a transparency of ∼ 85% respectively. In addition, current–voltage–luminescence results of the TOLED passivated by the SiN x layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN x deposition process.

Size Reduction of Cavity-Backed Slot Antennas

A technique for reducing the dimensions of the cavity of a cavity-backed slot antenna (CBSA) is presented, which facilitates proper fabrication and integration of miniaturized slot antennas on multilayer substrates. This is accomplished by replacing the solid metal around the traditional slot antennas with a specific metallic pattern that can be viewed as a series of parallel strip lines placed around the slot antenna. This metallic pattern is then modified by designing the parallel strips in a compact fashion to reduce the overall antenna dimensions and obtain a reduced-size CBSA. It is shown that, for a simple straight slot antenna, the overall occupied volume of the modified cavity backing the slot antenna can be reduced by more than 65% without affecting the high radiation efficiency of the antenna. A number of traditional cavity backed slot antennas and the proposed modified CBSAs are designed, fabricated, and measured. The reduced-size CBSAs show a very low input VSWR, low cross-polarized radiation levels, and high radiation efficiency. Despite their small ground plane size, the proposed cavity backed slot antennas have front-to-back ratio (FTBR) values in the range of 6-7 dB

Hepatocellular Carcinoma: Microwave Ablation with Multiple Straight and Loop Antenna Clusters—Pilot Comparison with Pathologic Findings

The purpose of this study was to evaluate the clinical implementation of triangular and spherical designs for simultaneous multiple-antenna ablation of human hepatocellular carcinoma (HCC) with a recently engineered microwave coagulation system. Institutional review board approval and informed consent were obtained, and the study was compliant with HIPAA requirements. Nine patients (five men, four women; age range, 53-79 years; mean age, 66.2 years) with resectable HCC (diameter, 2.9-6.0 cm; mean, 4.2 cm) underwent intraoperative ultrasonography-guided tumor ablation followed by resection and pathologic examination. Standard single-straight (n = 2), triangular triple-straight (n = 4), and spherical triple-loop (n = 3) antenna configurations produced mean estimated coagulation volumes of 16.7, 51.7, and 54.3 cm(3), respectively, during a single concurrent 5-10-minute ablation cycle. The triple-loop configuration yielded the most uniformly round ablation shape. Simultaneous activation of multiple straight or loop antennae is a potentially promising technique for rapid and effective treatment of large HCCs.

Radiation Impedance of a Thin Straight Antenna Derived from Hallen's Equation by the Circuit-Theoretical Method

Extending the domain of the vector potential in the so-called Hallen's equation, four unknown constants are determined to satisfy the boundary conditions in the same way as the circuit theory, where the vector potential plays the leading role, from which the current density and the current itself are derived. Vanishing of the current density just outside the ends of the antenna is required. For a tube-shaped antenna with walls of infinitesimal thickness, further the current just inside the ends of the antenna should vanish, as a result, the current distribution becomes sinusoidal. Adoption of either the surface current distribution or axial current distribution incurs a crucial effect on the value of the currents calculated from the vector potential. The numerical results of the radiation impedance of a hslf-wave antenna show a tendency of consistency with that relatively newly obtained by employing the exact kernel. The problem on the non-solvability of Hallen's equation is cleared up. Comments are given on the moment method in relation to the boundary value problems to recommend to add two more undecided constants to Hallen's equation.

Microwave Ablation of Hepatic Tumors Using Dual-Loop Probes: Results of a Phase I Clinical Trial

Hepatic tumors are a common cause of death worldwide. However, few patients are candidates for resection at the time of presentation. Microwave ablation is a viable alternative available for these patients. To date, only straight antennas are used for microwave ablation. Recently, a prototype loop-shaped microwave antenna was developed that, in animal studies, more effectively kills tumors. For this study, the dual-probe lesions were created by placing the probes in both tumors and normal livers. Lesions were created with 60 watts applied power for 5-7 minutes. The livers were sectioned and stained for viability. The average ablation volume was 63.9 +/- 8.7 cm(3). Microwave ablation with the loop probes results in complete tumor kill at the ablation/tumor interface, and adjacent to surrounding blood vessels. In addition, vessels within the ablation/tumor interface failed to show viable cells. The shape of the lesions was not distorted by proximity to blood vessels. The advantages of this configuration over conventional straight probes include the ability to encircle a tumor, deliver large amounts of precisely targeted microwave energy to the tumor, and spare normal liver outside the loop.

Implement the Theory of Maxwellian Circuits to Spiral Antennas

The main idea of Maxwellian circuits is that any wire structure, such as a thin wire antenna or a microstrip structure, can be represented by equivalent distributed circuits, the solution of which is identical to the solution of Maxwell's equations of that structure. Such circuits are said to be Maxwellian . In this paper, the Maxwellian circuits are implemented into a curved structure, i.e., spiral antennas. Since a spiral antenna has much stronger dispersion and mutual couplings than a straight antenna, the most challenging thing for the spiral antenna is how to realize the broadband equivalent circuits. Numerical results for the two-arm Archimedian spiral antenna show that the solutions of its Maxwellian circuits over a quite wide frequency band are the same as those obtained by the conventional integral equations, but solving the circuits represented by the differential equations is much more efficient than solving the integral equations.

A network-analyser calibration method for accurate measurement of the reflection coefficients of monopolelike antennas

A calibration method able to subtract the response of the connector in the measurement of the reflection coefficient of monopolelike antennas is presented. The method uses a set of straight monopole antennas as reference loads for calibration using a vector network analyser. The experimental example of a double-iterated fractal Koch monopole confirms the effectiveness of the technique proposed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 330–332, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21161

新しいアンテナわん曲型マイクロ波電極と“包囲凝固”

We developed a new microwave electrode with curved antenna for the purpose to achieve “enveloping coagulation” on microwave coagulation therapy more easily. “Enveloping coagulation” means, we named, coagulation process that enveloping coagulation should be done around tumor first and center coagulation next.The property of new microwave electrode with curved antenna was almost as same as that of original electrode with straight antenna but coagulation area was curved.As the result, a new microwave electrode would be thought very useful to perform “enveloping coagulation” more easily.A case of liver cancer treated with a new microwave electrode was reported.

Linear internal inductively coupled plasma (ICP) source with magnetic fields for large area processing

A large-area (830×1020 mm) inductively coupled plasma source with internal straight antennas was developed for large area flat panel display (FPD) etch process applications and the effects of magnetic fields employing permanent magnets on the plasma characteristics were investigated. Using straight antennas connected in series without the magnetic field, high-density plasmas on the order of 10 11 cm −3 could be obtained by applying 1500 W of r.f. power to the antennas. By employing the magnetic fields perpendicular to the antenna currents using permanent magnets, improved plasma characteristics such as increase of ion density and decrease of both electron temperature and plasma potential could be achieved in addition to the stability of the plasma possibly due to the reduction of the electron loss. However, the application of the magnetic field decreased the plasma uniformity slightly even though the uniformity within 10% could be maintained in the 800 mm processing area.

An electromagnetic model of lightning return stroke channel using electric field integral equation in time domain

We use an electromagnetic approach based on antenna theory (AT) to evaluate the lightning return stroke current as a function of time and height. The lightning channel is modeled as a lossy, straight, and vertical monopole antenna above a perfectly conducting ground, which is excited by a source voltage at the base of the channel. This voltage source is a function of the current assumed at the ground level and the input impedance of the monopole antenna. An electric field integral equation (EFIE) is employed to describe the electromagnetic behavior of the antenna. The numerical solution of EFIE by the method of moments in time domain provides the time-space distribution of the current along the lightning channel. This AT model with specified current at the channel base requires only two adjustable parameters, namely the return-stroke propagation speed and the channel resistance per unit length. To demonstrate the accuracy of the proposed model, we compare it to the most commonly used models in terms of the temporal and spatial distributions of channel current and predicted electromagnetic fields. We also present results to show the effectiveness of the model in the analysis of lightning-related problems dealing with complex structures. In this regard, the lightning induced overvoltages on the neighboring overhead lines and the lightning strikes to tall structures are investigated.

Internal linear inductively coupled plasma (ICP) sources for large area FPD etch process applications

A large area (830 mm×1020 mm) inductively coupled plasma source with a six internal straight antennas was developed for large area FPD (Flat Panel Display) etch process applications and the effects of magnetic fields employing permanent magnets on the plasma characteristics were investigated. Using six straight antennas connected in series into plasma and though the induction of strong electric field into the plasma by the antennas, high-density plasma on the order of 10 11 cm −3 could be obtained by applying above 1500 W power to the antennas. By employing the magnetic fields perpendicular to the antenna currents using permanent magnets, improved plasma characteristics such as increase of the ion density and decrease of both electron temperature and plasma potential could be achieved in addition to the stability of the plasma possibly due to the reduction of the electron loss. However, the application of the magnetic field decreased the plasma uniformity slightly even though the uniformity within 10% could be maintained in the 800 mm processing area.