Directional and smart antennas can be useful in increasing the capacity of wireless ad hoc networks. A number of media access and routing protocols have been recently proposed for use with such antennas, and have shown significant performance improvements over the omni-directional case. However, it is important to explore if and how different directional and smart antenna designs affect the asy...

It is difficult to build directional antennas for borehole radar due to the limited space available in the borehole. Recently published results show, however, that it is possible to obtain directional information even from electrically small antennas. In this paper, we use Finite-Difference Time-Domain (FDTD) modelling to optimise the design of a four-element directional antenna array, so that ...

in this article, the linear array (with 20 elements in the horizontal orientation) of microstrip antenna is examined with horizontal polarization. the set includes three microstrip substrates. there is a power network in two lower substrates and microstrip patches in the upper substrate. excitation of patches has been done as coupled through the power network in two lower substrates. using the ...

The PDP(Partial Dominant Pruning) method is known as most practical method to reduce overlapped broadcasting messages by designating forward node as in-fly type when broadcasting occurs in the mobile wireless network with directional antenna. In this paper, we introduce DPDP(Directional PDP) that reduces not only number of nodes but number of used antenna elements simultaneously. By simulation,...

Biomedical applications necessitate some restrictions on the type of devices to be used. When Ultra-Wide Band signals are used, the antenna is better to be directional and small in size. This paper presents a modified directional patch antenna design and fabrication which was used in real breast cancer detection experiments using breast phantom. It shows optimistic results.

This paper presents an overview of retrodirective antenna systems developed for use in wireless communications. This multiple antenna system automatically reflects incident radiation in the direction of the source radiator by re-transmitting the phase conjugate of the received signal at each antenna. The overall system behaves as a directional antenna with omni-directional coverage and allows t...

In IEEE 802.11 based wireless networks adding more access points does not always guarantee an increase of network capacity. In some cases, additional access points may contribute to degrade the aggregated network throughput as more interference is introduced. This paper characterizes the power interference in CSMA/CA based networks consisting of nodes using directional antenna. The severity of ...

In this paper we address methods for characterizing small, low-gain antennas that are intended to be operated autonomously by a passive transponder chip. We present a way to perform accurate 3D gain measurements by means of a small, battery-powered, calibrated signal source and a two axis rotation apparatus. From the measurement results the directional pattern and the antenna efficiency are der...

In this paper, the issue of broadcasting in mobile ad hoc networks (MANETs) is considered. A node equipped with directional antenna can divide the Omni directional transmission range into several sectors and turn some of them “on” for transmission. In the proposed scheme using a directional antenna, forwarding nodes selected locally need to transmit broadcast messages, only to the restricted se...