Title: no more than 15 words.V ariable beamwidth corner reflector antennaList authors beneath title. references.A simple and successful design for a variable beamwidth corner reflector antenna is presented. The gain and the –3dB beamwidth of the antenna are predicted using the finite difference time domain (FDTD) method. Thepredicted results are comparedwith measured data and good agreement is reported.Please include headings. An Introduction must be clearly marked.Text: Please set text in double-spaced lines and in one column only. Font should be Arial 11pt. Margins should be set so that top and bottom are at 2.54, and left and right are at 3.17. Please number all pages.References: Please set references in squarebrackets and ensure they are included in the Reference section at the end of the paper.Acronyms & abbreviations: Must be clearly defined on their first occurrence in the text.Introduction:Thecorner reflectorantennaisasimpleantennaformediumgainapplications at UHF and low microwave frequencies. It consists of two flat platesintersecting at an apex angle and is usually fed by a half wave dipole placed alongthe plane which bisects the plates.The corner reflector antenna was invented in1938 by Kraus [1] who showed that the radiation characteristic of an infinitesizecorner reflector can be computed analytically using image theory if the apex angle is a sub-multiple of1954 by Wait [2]. The influence of the finite size reflector plates on the radiationpattern of the cornerreflector antenna was first investigated by Olver and Steif [3] using the finitedifference time domain (FDTD) method described byTaflove [4] and manyotherauthors. For some applications of the corner reflector antenna it is desirable to beable to adjust the beamwidth of the radiation characteristic. This Letter proposes that a variable beamwidth antenna can be achieved by making a corner reflector antenna with a hinge at the apex angle.names will be published in must be concise and must not include any the order submitted.Forename initial followed Abstract: Up to 200 by full surname must be words (approx.). This provided. Please note thatPrediction method: FDTD is an ideal method for predicting the radiationcharacteristics of corner reflector antennas because of its ability to model mediumsizeantennaswithconsiderableaccuracy[3].The3DcodeusedfortheFDTDsimulations was developed at Queen Mary and W estfield College (QMW). The cellEquationsEditors can be used as long as theyare in English was chosensuch that thestructure washalfa wavelengthfromthe absorbingboundary conditions (ABCs). The near field to far field transformation surface wastwo cells from the apex and the edges of the structure. The simulation frequency was 5GHz and the number of time steps was set such that the field settled down to aconstant value. The H-plane radiation pattern, D H , is defined as the ratio of radiatedpower in a specified direction in a plane to the total radiated power in this plane: Numbered equations or substantial where I(90,�) is the radiation intensity in direction (90,�). line from the text.Figures:Please clearly cite allfiguresprovidedwithin themain text. Test antenna: To verify the predictions, an experimental variable beamwidth cornerreflector antenna was built and measured. The reflector plates were made of brass.Fig. 1 shows the experimental antenna. The structure which allowed movement of the plates had to be designed so that the apex angle could be precisely changed whilst minimising the distortion to the radiation characteristics. The main difficulty for the design was to ensure that the two plates moved synchronously so that the dipole was always at the bisector. This synchronous movement of the plates was realisedthrough two struts on a sliding rail from the rear of the reflector to the front end of the plates. The location of the fixing point of the struts was partly chosen so that the force needed to change the angle of the plates was minimised, and partly so that a change in apex angle translated to less movement at the apex than at the front end of theplates. This mechanism gave precise control over the apex angle. Special care was��2� D = [2� I(90,�)] / [�I(90,�)d �] maths must be set on a separatetaken with the design of the hinge. A normal hinge would produce a slot between the plates when the apex angle was increased. To avoid this, a hinge was constructedwhere the point of rotation coincided with the apex. The antenna was designed for5GHz and was fed by a half wave dipole separated by 30mm (0.5measured in the compact antenna test range (CA TR) at QMW. Gain measurements All variables must be defined.Results: The H-plane radiation pattershown in Fig. 2. In both cases the side-lobe level is just below –20dB. The front-to-back ratio decreases from – –comparison of the measuredand predicted results shows good agreement in themainbeamdirection. The measured patternsinthebackdirectionare slightlydistorted by the mounting structure. The E-plane patterns showed the same level of agreement, but are of less interest since they are partly dependent on the height of the reflector plates. In Fig. 3, the measured and predicted gain and –3dB beamwidth forapex anglesin the range from 30 to 120low gain antennas in the CA TR of QMW at 5GHz. The measured gain excludes the input impedance.The agreement of the predicted and measured –3dB beamwidth is very good. For theimpedance of the corner reflector antenna falls, owing to the close proximity of theplates in respect to the dipole. This yields a reflection coefficient (S11 ) of > –3dB for which the gain-transfer method does not give good results since a high percentage of the incoming power is reflected.were conducted using the gain-transfer method.–3dB beamwidth can be doubled by changing the apex angle by an equivalent amount.thepredictions of image theory whichpostulates a null atboresight for adipoleiation was 4.2dB for aantenna.The variation of the –3dB beamwidth can be expanded by increasing the length of–3dB beamwidth varies from 20 toConclusion: must be clearly marked. Conclusion: The theory and experiment have demonstrated the ability to make a simple variable beamwidth corner reflector antenna.ReferencesReferences: Electronics Letters uses the V ancouver Reference System. Please give as much information as possible [all authors, title, publication/book/conference name, date, venue, vol. and issue (ifrelevant), page numbers, etc].All references must be referred to within the text (in numerical order). Please double-space all references.NOTE that references to submitted works cannot be included unless they have been accepted for publication.1 KRAUS, J. D. : ‘The square-corner reflector ’, Radio, 1939, 237, pp. 19–242 W AIT, J.R.: ‘On the theory of an antenna with an infinite corner reflector ’, Can. J.Phys., 1954, 32, (6), pp. 365–3713OL VER, A.D., and STERR, U.O. : ‘Study of corner reflector antenna using FDTD’.Proc. Int. Conf. on Antennas and Propagation, April 1997, Edinburgh, Vol. 1, pp. 334–3374TAFLOVE, A.: ‘Computational electrodynamics’(Artech House, Norwood, MA, 1995)Please give full affiliations of all authors.Note: We assume that the first author is thecorresponding author unless otherwise stated.Authors’ affiliations:U.O. Sterr, A.D. Olver and P.J.B. Clarricoats (Department of Electronic Engineering,Queen Mary and Westfield College, Mile End Road, London E1 4NS, United Kingdom)E-mail addresses: Please include the e-E-mail: theiet@org mail address of the corresponding authorfor editorial use. This address may also bepublished in the journal unless otherwisespecified.Figure captions:Captions must be provided for each Figure/Table in the paper. Please set Figure and Table captions separate from the rest of the text. Sub-captions, if necessary, should include brief additional information, such as a key, or details of different sections in the Figure, e.g. a, b, c, (i), (ii), (iii), etc.Fig. 1 Experimental variable beamwidth corner reflector antennaFig. 2 Measured and predicted H-plane radiation pattern for——— l – – – – +Fig. 3 –3dB beamwidth and gain against apex angle ——— predicted gain Imeasured gain— — predicted –3dB beamwidth – – – measured –3dB beamwidthLength of paper: The length of the text greatly depends on the number (and size) of Figures/Tables included. Please judge this from past issues of Electronics Letters and using the Guide to Authors which can be found at the URL:/journals/doc/IEEDRLhome/info/journals/el/submissions.jspFigures: Set separate from the captions. Please ensure that Figures are clearly labelled and are of good quality. All Figures are relettered, so inclusion of unlettered originals is welcomed.Note: if possible, please try to avoid setting line-drawings and photographs in the same Figure since photographs require differentprocessing in order to maintain quality.。