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One aspect of this paper is to describe the possibilities for reducing the overall size of a monopole so that they can be hidden within a system rather than protrude from it. Improved bandwidth results from the bow-tie monopole but there are instances where individual bands rather than a single band is preferable, for example for rejection of unwanted signals. One class of antenna to replace the monopole...
Time-domain simulation techniques such as "transmission-line modelling" (TLM) are found to be particularly suitable in broad-band electromagnetic modelling of vehicles for the analysis of electromagnetic compatibility (EMC). In addition, these same models could equally well be used to investigate and optimise the installed performance of vehicle mounted antennas. The results of a preliminary...
Single and stacked microstrip antennas were used in the past for the measurement of dielectric constants and thicknesses of lossy and lossless dielectrics at microwave frequencies. The two large slots at the two ends of the microstrip antenna produce a significant fringing field which couples to the material under test. One of the limitations of the microstrip antenna is its spatial resolution, which...
Today's mobile phones require proof of compliance to standard limits of the specific absorption rate (SAR), before they can be allowed onto the market. The SAR is a calculation of the power absorbed by tissue, averaged over a mass, resulting from the radiation of the handset. This requirement is set by standard committees worldwide making it a critical design consideration for the handset and antenna...
A useful and cost effective technique for performing RCS evaluation of targets is making use of scale model testing. As scale factors increase in magnitude, the required test facility size, and thus cost, decrease. Orbit/FR has designed and instrumented a test facility that is capable of performing high scale factor model testing as well as component and material segment testing. These capabilities...
A novel free-space method for the measurement of complex permittivity and thickness of materials has been developed. Antenna-medium coupling is taken into account. Thus, the antenna can be placed in close proximity to the sample material. Compared with conventional free-space techniques, the proposed method achieves a higher accuracy and it can be used in the UHF frequency range. An example is provided...
The design and characterisation of radar absorbing material (RAM) is usually carried out under the assumption that the latter is in the form of a sheet of constant electrical or physical thickness. There are occasions, however, when this is not so. Although there is some discussion in the literature on scattering from impedance wedges, this is mainly concerned with edge diffraction effects. In this...
A genetic algorithm-based tuning method for automatic antenna impedance matching is developed. A detailed tuning procedure is presented. A software package realizing the tuning method has been developed. Simulation results using the software package are also given for /spl pi/ impedance matching networks.
A planar monopole may be realised by replacing the wire element of a conventional monopole with a planar element. In this case, the planar element which is square, is located above a groundplane and fed using an SMA connector as illustrated. The square monopole has a simple geometry and a smaller bandwidth compared to the circular-disc monopole. However, it is still a broadband antenna with a typical...
We developed a volume surface integral equation (VSIE) based method of moments (MoM) employing transfinite elements which are a generalisation of all the elements appearing in the literature. Thanks to the transfinite elements it has been possible to study separately the influences of geometrical description and of the interpolation scheme in the MoM. This study has made now it possible to define...
The near field behaviour of two different types of retrodirective antenna arrays are presented. For each type it is shown that retrodirective properties can be preserved well into the antenna array near field. To our knowledge for the first time it is shown that distortions arising in the radiation pattern of each array type primarily occurs due to the effect of the individual radiation pattern characteristics...
This paper presents a method for increasing the isolation between transmit and receive ports of a dual polarised microstrip patch antenna in order to enhance its performance in single frequency simultaneous transmit/receive applications. A feedforward circuit signal cancellation scheme is demonstrated which is shown to improve the dual polarised antenna port isolation performance to be better than...
An approach to hybridisation of the method of moments and the finite difference time domain method is investigated. This hybrid method is capable of analysing a system of multiple physically-unconnected regions by employing the principle of equivalent sources. The case of multiple sources in the presence of scattering objects is discussed. Some examples are given for testing the validity of the approach...
Many organisations are investigating the incorporation of novel techniques within future 3G network components, in order to meet the goals of UMTS. One such technique is the use of "adaptive" or "smart" antennas at base sites. The benign influence of adaptive antennas on uplink and downlink spatio-temporal responses offers potential for interference reduction and capacity multiplication...
This paper deals with propagation over irregular terrain and its resolution using integral equations. We describe several kinds of integral equation models and we use three different softwares based on the following methods: Maclean and Wu (Wu et al. 1988), Ott (1970) and Hufford (1952). The results given by the three softwares are compared to analytical solutions on simple terrain irregularity in...
The background to, and current state of, the CEPHOS project is reviewed. This has the objective of producing uniform pan-European guidelines for numerical and experimental dosimetry procedures to evaluate the effect of mobile telephones on human users. Technical work packages within the project are focusing on test pieces (physical and software) to evaluate comparability of test procedures and electromagnetic...
Surface penetrating radar (SPR) is extensively used in military, civil, geophysical and archaeological applications. There has been an increasing emphasis on the use of SPR in the identification of buried unexploded ordnance, such as anti-tank mines, antipersonnel mines etc., which can be metallic or plastic in nature. Mine detection methods can be classified as destructive or non-destructive. Non-destructive...
The TSUNAMI (II) project has addressed an investigation into the application of adaptive antenna technology for use in future generation mobile communications systems. The key aims of the project were to investigate the complexity versus increase in system capacity and coverage extension that can be achieved over the existing, non-adaptive networks. May 1998 saw the completion of an 8 month field...
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