Improved low-height antifading medium-wave antenna

A quarter-wave dipole antenna is typically used in portable transceivers of cellular personal communications systems. As a result of an omnidirectional radiation pattern of such an antenna a considerable part of the emitted power is absorbed by a user's body, especially by the head. Small handset antennas with a relatively wide bandwidth and minimized radiation pattern towards the user's head are presented in this paper. Two types of microstrip antennas i.e. dipole and patch antennas are considered. The results of experiments confirm that compromise between the requirements for radiation pattern and human head protection is possible and consequently, such types of antennas can be used effectively for mobile communications.

A number of loop antennas designed to operate at UHF ISM band 2.4-2.5 GHz have been investigated. Four types of loop antennas were designed and fabricated including the circular wire loop, square loop, circular plate loop, and disk loop. The circular plate loop has been incorporated into the RF sensing and detection peripheral due to its excellent practical performance. It was examined in various types of wireless environments where the complex object/ material both conductive and non conductive existed. In this paper, each type of antennas was also tested, numerically and experimentally, to obtain its individual electrical properties such as S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , VSWR, and radiation pattern.

Highly energetic protons trapped in the inner Van Allen belt can disturb spacecraft operations, contaminate scientific measurements, and even cause early termination of missions. Earlier papers proposed that space-based coil antennas in the Electromagnetic Ion Cyclotron (EMIC) wave regime could potentially remove these particles by precipitating them into the atmosphere. Specifically, the designs involve a coil antenna driven in DC but rotating at the desired EMIC frequency (that is, below the proton gyro-frequency), which is capable of generating these waves and could serve as a payload on a scientific mission with the purpose of testing the ideas behind the concept of controlled removal of energetic trapped protons. This paper focuses on the radiation characteristics of this potential payload. We calculate the radiation pattern and radiation resistance of this transmitter operating in the EMIC band, taking into account the response of the plasma. We present a full-wave linear model capable of calculating the radiation pattern and radiation resistance in the far-field region of the rotating coil configuration immersed in a cold magnetized plasma consisting of protons and electrons. The stationary phase method is used to find a solution to the inverse Fourier transform of the radiated fields. The model shows that the power flux is fairly confined within a very small cone around the geomagnetic field lines, which corresponds to the waves' resonance cone; the corresponding wave number vectors, however, are close to perpendicular to the Poynting flux direction. The radiation resistance is at a maximum for coil axis perpendicular to the geomagnetic field lines, which defines a preferred axis of rotation for the coil constituting the transmitter. Additionally, we show that the radiated power increases with increasing rotation frequency. We present at the end of the paper a brief discussion on thermal effects and other assumptions which should be carefully reconsidered in future efforts.

This paper discusses the experiment of measuring antenna radiation patterns using hardware and software that has been made previously. The antenna measured is the Half Wave Open Dipole antenna that works at VHF frequencies as Antenna Under Testing (AUT). The hardware used is Module-1 and Module-2 which have previously been tested for functionality, and the software is the Antenna Radiation Pattern application that is created using the Visual Basic programming language in the Microsoft Visual Studio package. Radiation pattern measurement experiments were carried out under various conditions, namely (1) without RF signals; (2) with RF signal and the position of the transmitting antenna is 0o with AUT; (3) with the RF signal and the position of the transmitting antenna at an angle of 90o to AUT; and (4) simulation of electromagnetic wave interference when making measurements. Based on the results of experiments conducted, it can be concluded that the Antenna Radiation Pattern application has functioned well and can describe the AUT radiation pattern. Future work of this research is the measurement of radiation patterns for other types of antennas and refinement of applications for the measurement of various antenna parameters.

Lens antennas are a promising device for realizing the anti-collision radars needed in intelligent transport systems (ITS) and multibeam antennas for satellite communication. They have simple structure, high gain and no feed blockage. Especially if the operating frequencies are above the microwave band, the resulting apertures with several tens of wavelengths, become practical. In advance ITS application, the antenna is expected to resolve several objects in azimuth plane. In satellite application, the terrestrial station should catch multiple satellites at various directions. These applications demand multibeam antennas. Typical antennas with multibeam attributes include the dual-reflector bifocal antenna (Rao, 1974). Another proposal is the bifocal lens (Brown, 1956), its multibeam characteristics has been evaluated (Peebles, 1988). Multibeam antennas have to form high gain and low sidelobe radiation patterns at different directions. The bifocal lens is guaranteed to equalize the aperture phase distribution on the specified design directions in the scanning plane. However, it is not guaranteed on the transverse plane due to its astigmatism, and no previous report has adequately addressed the design issues, especially the resulting degradation of the radiation pattern. Another multibeam lens antenna is the Luneburg lens (Luneburg, 1964). Though it offers many focal points at arbitrary directions, it has manufacturing problems, tapered dielectric constant, and heavy weight. Our solution is to propose an effective method that optimizes multibeam lens antennas by gain, beamwidth, and sidelobe level. Antenna designs based on GA are very attractive and various methods have been proposed (Altshuler & Linden, 1997; Jones & Joines, 1997); we have already proposed a Yagi-Uda antenna design based on the pareto-GA (Kuwahara, 2005). This chapter presents the design of a multibeam lens antenna based on the pareto-GA. The coordinates of the lens shape and the feed position are given as variables and are associated with GA chromosomes. From the variables, the radiation patterns are calculated. The values of the objective functions are evaluated from the radiation pattern. The objective functions are given as the gain and the sidelobe level on the scanning plane and the transverse plane. To balance these objective functions, we adopt the pareto-GA (Fonseca & Fleming, 1993). In the pareto-GA, individuals are ranked through multiple objective functions and selection 18

This paper introduces a new low cost, robust miniaturized microstrip antenna inspired with metamaterial split ring resonator structure (SRR). Because of metamaterials property there has been considerable reduction in size. The overall antenna structure is phi shaped, which is the same as having two SRRs back to back. The scattering matrix characteristics of this phi shaped antenna (PSA) have been investigated using the EM solver Ansoft HFSS. Excellent performance in terms of size and radiation pattern is achieved. These types of antennas are very useful for applications where space of equipment is a constraint. Radiation pattern of the antenna is dough nut shaped, nearly omni-directional. This type of antenna is useful for the applications like sensors for ground penetration radar, sensors for detection of malignant tissues in skin cancer patients and other handheld portable wireless equipments.

Partial discharge (PD) is the causes of the fault to occur in high voltage equipment due to the breakdown of the insulation system happen on equipment, even old equipment or new equipment. The PD in transformer oil is one of the significant causes of insulation failure and a breakdown. Hence, a sensor is needed to continuously monitor and detect the PD at an early stage on the power transformer. An antenna is one of the sensors that can be used to detect PD based on ultra-high frequency (UHF) method. However, the size of the antenna is the main problem to be installed in the transformer tank. Thus, three types of antenna which are Moore, Hilbert and Peano fractal with the dimension of 10 × 10 cm is designed to operate in UHF range 0.3 GHz to 3 GHz to be able to detect the frequency of partial discharge signal generated by electromagnetic waves. The performance of the proposed antennas in terms of return loss, Voltage Standing Wave Ratio (VSWR) and radiation pattern are analysed and compared for PD detection on the power transformer. Based on the result, the fourth-order of Hilbert fractal antenna was found to be the best antenna for PD detection in power transformer at working frequency range from 0.72 GHz to 2.77 GHz. This antenna also has low threshold of return loss at -36.2 dB for the resonant frequency at 1.67 GHz and the value of VSWR is near to one which is 1.03. Lastly, the radiation pattern of this antenna is almost in hemisphere shape and the gain variation of all frequencies are nearly stable compared to the other types of antenna.

This paper presents novel compact dipole antennas based on forward-coupling configuration of multilayer ring resonators (MRR) structure. The antenna consists of two conductive square open loops. The frequency of operation can be varied through the coupling between the two rings. This is achieved by changing the distance between the two radiating elements. Hence, these types of antennas are simply tunable. The structure is so versatile that a class of new antennas can be developed using this technique. The radiation pattern is bidirectional with a peak gain of 2.8 dBi. A good impedance matching and return loss better than 35 dB are obtained. Simulations have been carried out and the S-parameters, VSWR and radiation patterns are presented.

Subject and Purpose. The directivity characteristics of a dipole antenna when it is placed above and parallel to a perfectly conducting screen of rectangular shape are considered, aiming to theoretically study dipole antennas with sector-shaped radiation patterns (RP) formed by choosing the optimal electrical dimensions of the screen and the distance between the dipole and the screen. Methods and Methodology. The problem of the dipole radiation field diffraction by the edges of a rectangular screen is solved by the method of the uniform geometric theory of diffraction. The diffracted fields developed at the screen edges are calculated using the uniform asymptotics obtained from the rigorous solution of the model problem of the dipole field diffraction by the edge of a perfectly conducting half-plane. Results. The algorithms and calculation programs developed allow studying the electrodynamic characteristics of the antenna over a wide range of screen electrical dimensions and distances between the dipole and the screen. Radiation patterns, directivity in a path normal to the screen and in directions of maximum radiation, radiation resistance, and protective ratio have been calculated across a broad range of screen dimensions and distances between the dipole and the screen. It has been observed that the antenna of the kind forms sector-shaped radiation patterns when the distance between the dipole and the screen is 0.30 to 0.45 of the resonant wavelength of the dipole. The obtained results have been confirmed by the calculations using the FEKO program. Conclusions. It has been shown that the considered dipole antenna forms sector-shaped radiation patterns when the distance between the dipole and the screen is 0.30 to 0.45 of the dipole resonant wavelength depending on the screen dimensions. The obtained calculation results for the maximum achievable electrodynamic characteristics allow us to find optimal geometric parameters of the antenna with a sector-shaped pattern for a particular application.

: The relativistically correct potentials and fields are calculated for a basic electromagnetic source-model in which the electric charge at a fixed point suddenly starts increasing linearly with time, while the equal but opposite charge flows away from the point with constant velocity in a straight line. A numerical example of a field calculation is given. Limiting forms of the solution appropriate at great distances are found, and radiated power, radiation resistance, and radiation patterns are derived. Using the solution for ths basic model, solutions for other source-models are developed by linear superposition. These include fields from a current being generated at one point and stopped (absorbed) at another, and the fields from current impulses. (Author)

A annular slot antenna with cross-shaped feedline has been investigated experimentally to obtain a large bandwidth enhancement. The voltage standing wave ratio (VSWR), radiation pattern, and antenna gain of this configuration are presented. Although the use of a high relative permittivity (ɛr=4.3) substrate usually restricts the operation bandwidth, the radiation resistance also was a low value. The measured bandwidth is ∼108.4% (2.0≥VSWR).

We assess the potential error in measurements of the power transfer function corresponding to a reverberation chamber set-up when different antenna types are used for the reference and device-under-test measurements. We derive a mathematical description of the transfer function that accounts for differences in the amount of unstirred energy, represented by the spatially averaged K factor, arising from various antenna types. Our results show that loaded chamber configurations, combined with reference/device antenna pairs having significantly different radiation patterns, can result in statistically significant errors in the prediction of the transfer function. If it is possible to obtain an estimate of the K factor associated with the device antenna, this correction can improve the estimate of the transfer function that would be experienced by the device under test. Finally, we develop a method that could be used in standardized test methods to bound the uncertainty associated with the unknown K factor for common antenna types.

Objective To establish radiation-resistant lung carcinoma cell lines, and to investigate the changes in morphology, apoptosis, invasive migration, and epithelial-mesenchymal transition (EMT) in cells. Methods The radiation-resistant lung carcinoma cell lines were obtained by exposure of lung carcinoma cell lines, A549 and H1299, to radiation with a low dose in fractions, a sublethal dose, or a gradually increasing dose. The morphological changes in cells, radiosensitivity, survival rates after exposure, apoptosis rates, changes in invasive migration, and expression of EMT marker proteins were evaluated using microscopy, colony formation assay, CCK-8 assay, flow cytometry, transwell migration assay, and Western blot, respectively. Results Radiation with a gradually increasing dose successfully induced the radiation-resistant cell lines, A549R and H1299R. The morphological study showed that the morphology of radiation-resistant cells was converted to the morphology of mesenchymal cells. Compared with A549 and H1299 cells, the values of D0, Dq, and SF2 were significantly increased in A549R (P=0.017, P=0.001, P=0.000) and H1299R (P=0.033, P=0.000, P=0.008) cells, respectively; the values of α and α/β were significantly reduced in A549R (P=0.018; P=0.007) and H1299R (P=0.001; P=0.009) cells, respectively. The survival rates in A549R and H1299R cells after exposure to radiation with various doses were significantly higher than those in the control groups (all P<0.05). After exposure, the apoptosis rates were significantly reduced in A549R and H1299R cells (P=0.02, P=0.01); the invasion and migration rates were significantly increased in A549R (P=0.000; P=0.001) and H1299R (P=0.001, P=0.002) cells; the expression of E-cadherin was significantly down-regulated in A549R and H1299R cells (P=0.00, P=0.01), while the expression of vimentin was significantly elevated in A549R and H1299R cells (P=0.02, P=0.01). Conclusions The radiation-resistant lung carcinoma cell lines are successfully established. Both cell lines show enhanced invasion and migration, which may be associated with EMT. Key words: Lung carcinoma cell line, radioresistance; Colony formation assay; Transwell cell assay; Epithelial-mesenchymal transition

A summary on the last 5 years radiation testing of equipment for the LHC project in dedicated facilities outside CERN is presented. The proton irradiation facilities in CRC Louvain la Neuve and in the Paul Scherrer Institute have given an important contribution to the design of the LHC equipment. The intensive testing efforts from CERN groups in the last 5 years underline that radiation tolerance has become a design and operational constraint for the LHC. Radiation testing will most likely continue during the LHC commission phase when radiation induced equipment failures will start to appear.

A Microstrip Patch Antenna is a type of radio antenna with a low profile, which can be mounted on a low surface. It is a narrow band, wide-beam fed antenna fabricated by etching the antenna element pattern in metal trace bonded to the dielectric Substrate such as a printed circuit board with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. The main aim of this work is to design, develop and test the Printed Circuit antenna (Microstrip Patch antenna) suitable for use in L-band frequency range of 1-2GHz. This study also emphasizes on simulation of micro-strip patch antenna using IE3D software to simulate & study the radiation pattern & other radiation pattern parameters and comparison with specifications/requirements. Co-axial Feed technique was adopted and the location of the feed point was varied within the radiating patch to arrive at the point of minimum return loss. This work is also focused on characterization of fabricated antenna in view of parameters like VSWR, Antenna efficiency, Axial ratio, Gain and radiation pattern.