A novel H-shaped patch antenna

A novel H-shaped patch antenna suitable for wireless and satellite communications is presented. The new antenna has some advantages compared to conventional microstrip patch antennas, such as small size, a fewer number of modes, no harmonic resonance, and the provision of pure reactive impedances at its harmonics that can result in increasing the transmitter efficiency. The basic principles and design procedure are introduced. Two antennas at two different frequencies, 4 and 10 GHz, are designed, fabricated, and measured. The measured results show a good agreement with the predicted ones

Conformal FDTD analysis of an Octagonal Microstrip Patch antenna

The recent boom in wireless communication industry, especially in the area of cellular telephony and wireless data communication, has led to the increased demand for multi band antennas. In such applications the issues to be addressed are, wide bandwidth and gain, while striving for miniature geometry. A dual frequency configuration useful in GSM1800 and Blue tooth, is one that operates with similar properties, both in terms of reflection and radiation characteristics, in the two bands of interest. Dual frequency operations can be realized by exciting the Microstrip Patch Antenna (MPA) using a single feed [1] or dual feed [2]. In this paper, Conformal FDTD[3] method with Perfect Magnetic Conductor (PMC) applied along the plane of symmetry [4] is used to study the characteristics of an Octagonal MPA. The theoretical results are compared against the experimental and IE3D™ simulated results

A measurement system for determining radiation efficiency of a small antenna

The paper describes a system for measuring radiation efficiency of a small antenna operating alone or in the presence of objects similar to those as in an actual service. The system applies the direct approach to determining the antenna efficiency by measuring the radiated field over the entire sphere surrounding the tested antenna. In order to overcome problems associated with the conventional measuring equipment, the antenna under test is equipped with a miniature built-in VCO signal generator and supported by a low reflectivity dielectric positioner. The positioner is of sufficient size and strength to hold a human head phantom to investigate changes in radiation characteristics when the antenna operates in the presence of a human operator.

A beam-forming network for a circular switched-beam phased array antenna

This paper reports on the design and development of a dividing/phasing network for a compact switched-beam array antenna for Land-vehicle mobile satellite communications, The device is formed by a switched radial divider/combiner and 1-bit phase shifters and generates a sufficient number of beams for the proper satellite tracking.

Microstrip circular phased array design and development using microwave antenna CAD tools

The complex design and development of a planar multilayer phased array antenna in microstrip technology can be simplified using two commercially available design tools 1) Ansoft Ensemble and 2) HP-EEsof Touchstone. In the approach presented here, Touchstone is used to design RF switches and phase shifters whose scattering parameters are incorporated in Ensemble simulations using its black box tool. Using this approach, Ensemble is able to fully analyze the performance of radiating and beamforming layers of a phased array prior to its manufacturing. This strategy is demonstrated in a design example of a 12-element linearly-polarized circular phased array operating at L band. A comparison between theoretical and experimental results of the array is demonstrated.

Analysis of a circular patch antenna radiating in a parallel-plate radial guide

A field matching method is described to analyze a recessed circular cavity radiating into a radial waveguide. Using the wall impedance approach, the analysis is divided into two separate problems of the cavity and its external environment. Based on this analysis, a computer algorithm is developed for determining wall admittances as seen at the edge of the patch in the cavity, the radial admittance matrix for the two-probe feed arrangement, and the input impedance as observed from the coaxial line feeding the cavity. This algorithm is tested against the general-purpose Hewlett-Packard finite-element High Frequency Structure Simulator as well as against measured results. Good agreement in all considered cases is noted.

A microstrip Yagi antenna using EBG structure

[1] In this paper a detailed design, development and performances of a 5 GHz microstrip Yagi antenna, which uses a two-dimensional (2-D) electromagnetic band gap (EBG) structure in the ground plane, are presented. The results indicate that the use of the EBG structure improves the radiation pattern of the antenna. The cross polarization is suppressed by properly choosing the period and dimensions of EBGs. Also, the broadside gain is improved in comparison with the analogous antenna without the EBGs.

An electromagnetic-field method modeling of a radial line planar antenna with coupling probes

This communications describes an electromagnetic model of a radial line planar antenna consisting of a radial guide with one central probe and many peripheral probes arranged in concentric circles feeding an array of antenna elements such as patches or wire curls. The model takes into account interactions between the coupling probes while assuming isolation of radiating elements. Based on this model, computer programs are developed to determine equivalent circuit parameters of the feed network and the radiation pattern of the radial line planar antenna. Comparisons are made between the present model and the two-probe model developed earlier by other researchers.

Capacity Enhancement Using MIMO Antenna Arrays in Realistic Macro-Cellular Urban Environment

In MIMO systems the antenna array configuration in the BS and MS has a large influence on the available channel capacity. In this paper, we first introduce a new Frequency Selective (FS) MIMO framework for macro-cells in a realistic urban environment. The MIMO channel is built over a previously developed directional channel model, which considers the terrain and clutter information in the cluster, line-of-sight and link loss calculations. Next, MIMO configuration characteristics are investigated in order to maximize capacity, mainly the number of antennas, inter-antenna spacing and SNR impact. Channel and capacity simulation results are presented for the city of Lisbon, Portugal, using different antenna configurations. Two power allocations schemes are considered, uniform distribution and FS spatial water-filling. The results suggest optimized MIMO configurations, considering the antenna array size limitations, specially at the MS side.

SAR determination and influence of the human head in the radiation of a mobile antenna for two different frequencies

The big proliferation of mobile communication systems has caused an increased concern about the interaction between the human body and the antennas of mobile handsets. In order to study the problem, a multiband antenna was designed, fabricated and measured to operate over two frequency sub bands 900 and 1800 MHz. After that, we simulated the same antenna, but now, in the presence of a human head model to analyze the head's influence. First, the influence of the human head on the radiation efficiency of the antenna has been investigated as a function of the distance between the head and the antenna and with the inclination of the antenna. Furthermore, the relative amount of the electromagnetic power absorbed in the head has been obtained.

Influence of the Human Head in the Radiation of a Mobile Antenna

The big proliferation of mobile communication systems has caused an increased concern about the interaction between the human body and the antennas of mobile handsets. In order to study the problem, a multiband antenna was designed, fabricated and measured to operate over two frequency sub bands 900 and 1800 MHz. After that, we simulated the same antenna, but now, in the presence of a human head model to analyze the head's influence. First, the influence of the human head on the radiation efficiency of the antenna has been investigated as a function of the distance between the head and the antenna and with the inclination of the antenna. Furthermore, the relative amount of the electromagnetic power absorbed in the head has been obtained. In this study the electromagnetic analysis has been performed via FDTD (Finite Difference Time Domain).