UHF SATCOM broadband CP antenna: moxon type bent-dipoles over a ground plane

In this paper, we investigate and compare two different antenna types for UHF SATCOM applications; proposed Moxon type (bent dipole) and conventional egg beater (loop) antennas in terms of antenna performance and physical size. Bent dipole and egg beater antennas are simulated using HFSS software. Prototype antenna for Moxon type is also fabricated and measured for its return loss using Agilent network analyzer and compared to that of an egg beater antenna. Antenna gains are also simulated. Simulation results show that Moxon type antenna has more impedance bandwidth than egg beater antenna with smaller dimensions and hence can be used for broadband SATCOM applications

Novel small-size directional antenna for UWB WBAN/WPAN applications

This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna far field radiation pattern. The different structural antenna parameters were optimized via extensive numerical simulations. Results show that for frequencies above 3.5 GHz, where the power front-to-back ratio of the directional antenna is greater than 10 dB, its impedance is nearly the same as in the free space. It is not the case neither for the omnidirectional slot antenna nor the monopole antenna next to the body. Between 3 and 6 GHz performance of the novel directional antenna, in terms of radiation efficiency and SAR values, is significantly improved compared to omnidirectional antenna designs.This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna far field radiation pattern. The different structural antenna parameters were optimized via extensive numerical simulations. Results show that for frequencies above 3.5 GHz, where the power front-to-back ratio of the directional antenna is greater than 10 dB, its impedance is nearly the same as in the free space. It is not the case neither for the omnidirectional slot antenna nor the monopole antenna next to the body. Between 3 and 6 GHz performance of the novel directional antenna, in terms of radiation efficiency and SAR values, is significantly improved compared to omnidirectional antenna designs

RADOME ANALYSIS TECHNIQUES

Radar Dome, or usually called Radome, is usually placed over the antenna as an antenna protector from any physical thing that can break it. Ideally, radome does not degrade antenna performance. In fact, it may change antenna performance and cause several effects, such as boresight error, changing antenna side lobe level and depolarization. The antenna engineer must take stringent analysis to estimate the changes of performance due to placing radome. Methods in the analysis using fast receiving formulation based on Lorentz reciprocity and Geometrical Optics. The radome has been tilted for some angle combinations in azimuth and elevation with respect to the antenna under test in order to get the difference responses. From the results of measuring and analyzing the radome, it can be concluded that radome can change the antenna performance, including boresight shift, null fill-in and null shifting for difference signals, and changing antenna radiation pattern. In the CATR measurement with two reflectors, the extraneous signal which originates from feed is minimized by adding absorber at the side of the feed. Several things that affect to the accuracy of the simulation program are extraneous signal, loss tangent uncertainty, diffraction, and dielectric uncertainty and inhomogeneity. Key Words: Radome, CATR, Antenna, Boresight Erro

Conformal Antenna Array for Millimeter-Wave Communications: Performance Evaluation

In this paper, we study the influence of the radius of a cylindrical supporting structure on radiation properties of a conformal millimeter-wave antenna array. Bent antenna array structures on cylindrical surfaces may have important applications in future mobile devices. Small radii may be needed if the antenna is printed on the edges of mobile devices and in items which human beings are wearing, such as wrist watches, bracelets and rings. The antenna under study consists of four linear series-fed arrays of four patch elements and is operating at 58.8 GHz with linear polarization. The antenna array is fabricated on polytetrafluoroethylene substrate with thickness of 0.127 mm due to its good plasticity properties and low losses. Results for both planar and conformal antenna arrays show rather good agreement between simulation and measurements. The results show that conformal antenna structures allow achieving large angular coverage and may allow beam-steering implementations if switches are used to select between different arrays around a cylindrical supporting structure.Comment: Keywords: conformal antenna, millimeter-wave communications, patch antenna array. 11 pages, 10 figures, 1 tabl

School of Electrical Engineering.

The possibility of making the antenna of an MST radar too large is pointed out. It is not that the signal ceases to become stronger beyond some critical antenna size; the received scattered signal actually becomes weaker as the antenna size is increased whenever the target is in the near field, Fresnel region of the antenna. The Arecibo antenna is a case in point. It is supposed that MST work would benefit to use a feed which illuminated only a portion of the dish

Performance Limits of Fluid Antenna Systems

Fluid antenna represents a concept where a mechanically flexible antenna can switch its location freely within a given space. Recently, it has been reported that even with a tiny space, a single-antenna fluid antenna system (FAS) can outperform an L-antenna maximum ratio combining (MRC) system in terms of outage probability if the number of locations (or ports) the fluid antenna can be switched to, is large enough. This letter aims to study if extraordinary capacity can also be achieved by FAS with a small space. We do this by deriving the ergodic capacity, and a capacity lower bound. This letter also derives the level crossing rate (LCR) and average fade duration (AFD) for the FAS.Comment: 4 pages, 5 figure

An interferometer tracking radar system

Fine tuning acquisition and tracking interferometer radar system uses a first antenna array of at least three receiving antennas. Array includes a reference antenna, a coarse tuning antenna, and a fine tuning antenna aligned on a receiving axis. Short range rendezvous system provides increased position accuracy

Model-based Optimization of Compressive Antennas for High-Sensing-Capacity Applications

This paper presents a novel, model-based compressive antenna design method for high sensing capacity imaging applications. Given a set of design constraints, the method maximizes the sensing capacity of the compressive antenna by varying the constitutive properties of scatterers distributed along the antenna. Preliminary 2D design results demonstrate the new method's ability to produce antenna configurations with enhanced imaging capabilities