Hammam Shakhtour

Circularly Polarized Antenna With Steerable Dipole-Like Radiation Pattern

An omnidirectional circularly polarized antenna with a rotatable dipole-shaped radiation pattern is proposed. The antenna is realized using a back-to-back coupled microstrip patch arrangement. The pattern is rotated by means of a phase shift, enabling reception (or transmission) of signals from all angles around a sphere. The method enables continuous pattern steering without the need for semiconductor or MEMS components integrated into the antenna. It also allows the use of more than one radiation pattern simultaneously, potentially providing coverage for any spherical angle. The theory is supported by simulation and measurement of four typical antenna configurations. The maximum gains are between 1.9 and 4 dBic and average axial-ratio varies between 2.5 and 3.65 dB at 2.47 GHz. The impedance bandwidth is from 2.4 to 2.51 GHz and the reconfigurable circular polarization is achieved from 2.464 to 2.484 GHz.

Frequency selective radome with enhanced transmissive and absorptive response

Design of frequency selective radome having enhanced transmissive and absorptive characteristics is presented. The planar radome consists of laminate absorber and frequency selective structures (FSS). Lower insertion loss is achieved by patterning the laminate absorber while wider passband and steeper slope are obtained by using two layers of FSSs. Based on this approach the structure has the following properties: at lower band (1 - 3 GHz) it is reflective, at mid-band (4.3 - 5.8 GHz) it is transmissive/ RF transparent and at higher band (8.5 - 11.7 GHz) it is absorptive.

Thin multilayer frequency selective surface absorber with wide absorption response

Design and characterization of a multilayer structure consisting of stacked frequency selective surfaces (FSS) combined with a patterned laminate absorber is presented. The FSS part is a higher order bandpass filter that operates in the C-band, namely from 5 GHz to 6 GHz. Its higher order response is achieved through the stacking of capacitive-inductive-capacitive layers to maintain the low-profile structure. The patterned absorber is glued on one side of the FSS so that the resulting structure is capable of absorbing signals in the X-band (receiving mode). The prototype has been fabricated using Taconic RF-35 substrates and Eccosorb SF for the FSS and absorber parts, respectively. It has a dimension of 24.5 cm × 24.5 cm with a thickness of 0.65 cm. The measurement has been done using free space method. The transmission loss in the passband is less than 1 dB and the roll-off slope is more than 65 dB/octave. The absorption band, characterized by its low reflection and transmission response (less than -10 dB), covers the range from 8.26 GHz to more than 12 GHz. These specifications make this prototype a promising candidate for a planar radome absorber application.

Three antenna gain determination method in compact antenna test ranges

In this paper the well-known three antenna method for determining the antenna gain will be discussed in relation to a compact antenna test range. It will be shown that the applicability of such a method is possible and delivers quite accurate results if one carefully considers the different parameters that play a role in compact antenna test ranges.

Antenna Array Characterization with Iterative Fourier Transformation Technique [Measurements Corner]

This article presents simulation results for characterizing an 11 × 11 antenna array using phaseless planar near-field technique. The outcomes of this analysis show that with the help of the well-known iterative Fourier transform and with minimal a priori information, the far-field pattern of the antenna, even with beam steering, can be reconstructed well.

Comparison of two generations of textile MIMO antennas at IHF

A wearable textile antenna is a field of big interest and is getting more market [2]. Despite the simple idea and structure of such technology, some chapters are still open for further research, e.g. substrates, feeding, washing ability... etc. In this paper a comparison of two dual-polarized wearable textile antenna generations is introduced. Other than simulation and experimental results comparison, materials and production technology used will be also discussed, showing the advantages and disadvantages of these technologies. Both antennas have been developed to operate in the industrial, scientific and medical (ISM i.e. 2.4 GHz - 2.5 GHz) band [1]. The experimental and simulation results will be shown and compared to those achieved with an old version of this antenna.

Effect of different truncation angles in spherical near-field measurements

In all antenna measurement scenarios the complete radiation pattern is not available or not measurable and this is mainly due to montage reasons, where the tower on which the antenna is mounted shadows the antennas back side; causing loss of information. Other scenarios might be that the operator is not interested in the complete radiation pattern of the antenna but in some specific solid angle or area. In this paper truncation effect will be investigated, in which the missing field range will simply be filled with zeros. It will be shown that the location at which one truncates has a direct effect on the accuracy of the reconstructed antenna pattern in the valid region.