Browsing by Author "Towfiq, Md. A."
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Item Open Access A 60 GHz beam-steering reconfigurable antenna(IEEE, 2016) Khalat, A.; Towfiq, Md. A.; Cetiner, B. A.; Ceylan, Ö.; Bıyıklı, NecmiWe present the design, microfabrication, and characterization of a multifunctional reconfigurable antenna (MRA) with beam steering capability operating at 60 GHz band (59-66 GHz). The MRA provides 3 different beam directions pertaining to: θ {-30°,0°,30°}; φ = 90° based on reconfigurable parasitic layer approach. The structure consists of three layers namely, feed, driven antenna and reconfigurable parasitic layers. The first two layers use RF and microfabrication process compatible quartz (ϵr = 3.9, tanδ = 0.0002) substrate while parasitic layer is formed on a low-cost pyrex (ϵr = 4.9, tanδ = 0.01) material with air cavities formed underneath. The upper surface of pyrex has 3×3 rectangular shaped metallic pixels, four of which are interconnected by means of switching. By judiciously controlling the switch status the beam-steering is accomplished. The simulated impedance and gain characteristics show ∼ 15% bandwidth over which the maximum realized gain remains relatively flat around ∼ 7.2 dB for all modes of operation. © 2016 IEEE.Item Open Access Broadband high-gain 60 GHz antenna array(IEEE, 2016) Towfiq, Md. A.; Khalat, A.; Cetiner, B. A.; Ceylan, Özlem; Bıyıklı, NecmiThe design, fabrication and characterization of a 2×8 patch antenna array operating in the IEEE 802.11ad frequency band (57-66 GHz) is presented. The design is based on two-layer structures, where the radiating patches placed on top substrate are fed by conductor backed coplanar waveguide (CPW)-fed loop slots, which are placed on the bottom substrate. The top layer is formed by using a low-cost pyrex (ϵr = 4.9, tani = 0.01) substrate of 500μm thickness. The pyrex is then etched away to a thickness of 100μm, where 400μm of air volume is formed underneath. This approach does not only benefit from the low-cost feature of pyrex but also exploits the low-loss nature of air. The thin layer of pyrex is solely used for mechanical support for the radiating patches while the air provides good RF-environment for the array. The bottom substrate housing the CPW feed network is an RF-compatible and microfabrication friendly quartz (ϵr = 3.9, tanδ = 0.0002) of 525μm thickness. The simulations indicate a good maximum realized gain of 19.3 dBi of which variation over ∼ 17% bandwidth is relatively constant changing from 17-19.3 dBi. © 2016 IEEE.Item Open Access Mode shift keying for reconfigurable MIMO antennas: performance analysis and antenna design(IEEE, 2019-01) Hasan, M.; Bahçeci, İsrafil; Towfiq, Md. A.; Duman, Tolga M.; Çetiner, B. A.Space-shift-keying (SSK) and spatial modulation (SM) enable multiple antenna transmission systems to convey information on antenna indices. While SSK/SM helps reduce the number of radio frequency (RF) chains, large numbers of antennas and low spatial correlations are required to achieve high data rates. This work investigates the use and design of multifunctional reconfigurable antennas (MRAs) for SSK/SM based transmission where a single-element MRA generates large numbers of modes. To enhance legacy SSK/SM performance while reducing RF hardware complexity, we propose single- and multi-carrier antenna mode-shift keying (MoSK) and mode modulation (MoM) schemes facilitated by MRAs. Based on an error probability analysis, we determine criteria for MRA design and mode set selection suitable for MoSK/MoM. We also develop two MRA designs and investigate their performances over Rayleigh fading channels. We argue that by creating MRA modes with low pattern correlations, channel correlations can be reduced to improve the detection performance. Extensive simulations demonstrate that MoSK/MoM performance exceeds that of SSK/SM along with significant complexity reduction. For instance, a single-carrier MoSK/MoM using a single MRA with 8 modes achieves about 2 dB gain compared to legacy SSK/SM requiring 8 antennas, and by multi-carrier MoSK/MoM using 4 subcarriers, an MRA with 32 modes can attain an error rate performance comparable to this single-carrier system.