• 60 GHz Multi-Sector Antenna Array with Switchable Radiation-Beams for Small Cell 5G Networks

      Ojaroudi Parchin, Naser; Jahanbakhsh Basherlou, H.; Al-Yasir, Yasir; Abd-Alhameed, Raed A.; Excell, Peter S. (2020)
      A compact design of multi-sector patch antenna array for 60 GHz applications is presented and discussed in details. The proposed design combines five 1×8 linear patch antenna arrays, referred to as sectors, in a multi-sector configuration. The coaxial-fed radiation elements of the multi-sector array are designed on 0.2 mm Rogers RT5880 dielectrics. The array operates in the frequency range of 58-62 GHz and provides switchable directional/omnidirectional radiation beams with high gain and high directivity characteristics. The designed multi-sector array exhibits good performances and could be used in the fifth generation (5G) cellular networks.
    • A 70-W Asymmetrical Doherty Power Amplifier for 5G Base Stations

      Abdulkhaleq, Ahmed M.; Al-Yasir, Yasir; Ojaroudi Parchin, Naser; Brunning, J.; McEwan, N.; Rayit, A.; Abd-Alhameed, Raed A.; Noras, James M.; AbdulJabbar, N. (2018)
      Much attention has been paid to making 5G developments more en-ergy efficient, especially in view of the need for using high data rates with more complex modulation schemes within a limited bandwidth. The concept of the Doherty power amplifier for improving amplifier efficiency is explained in addi-tion to a case study of a 70W asymmetrical Doherty power Amplifier using two GaN HEMTs transistors with peak power ratings of 45W and 25W. The rationale for this choice of power ratio is discussed. The designed circuit works in the 3.4GHz frequency band with 200 MHz bandwidth. Rogers RO4350B substrate with dielectric constant εr=4.66 and thickness 0.035 mm is used. The perfor-mance analysis of the Doherty power amplifier is simulated using AWR MWO software. The simulated results showed that 54-64% drain efficiency has been achieved at 8 dB back-off within the specified bandwidth with an average gain of 10.7 dB.
    • 8-Port Semi-Circular Arc MIMO Antenna with an Inverted L-Strip Loaded Connected Ground for UWB Applications

      Addepalli, T.; Desai, A.; Elfergani, Issa T.; Anveshkumar, N.; Kulkarni, J.; Zebiri, C.; Rodriguez, J.; Abd-Alhameed, Raed A. (MDPI, 2021-06)
      Multiple-input multiple-output (MIMO) antennas with four and eight elements having connected grounds are designed for ultra-wideband applications. Careful optimization of the lines connecting the grounds leads to reduced mutual coupling amongst the radiating patches. The proposed antenna has a modified substrate geometry and comprises a circular arc-shaped conductive element on the top with the modified ground plane geometry. Polarization diversity and isolation are achieved by replicating the elements orthogonally forming a plus shape antenna structure. The modified ground plane consists of an inverted L strip and semi ellipse slot over the partial ground that helps the antenna in achieving effective wide bandwidth spanning from (117.91%) 2.84–11 GHz. Both 4/8-port antenna achieves a size of 0.61 λ × 0.61 λ mm2 (lowest frequency) where 4-port antenna is printed on FR4 substrate. The 4-port UWB MIMO antenna attains wide impedance bandwidth, Omni-directional pattern, isolation >15 dB, ECC 4.5 dB making the MIMO antenna suitable for portable UWB applications. Four element antenna structure is further extended to 8-element configuration with the connected ground where the decent value of IBW, isolation, and ECC is achieved.
    • A band-suppression UWB suspended planar antenna incorporating a slotted spiral resonator

      See, Chan H.; Abd-Alhameed, Raed A.; Hraga, Hmeda I.; Excell, Peter S.; Jones, Steven M.R.; Noras, James M. (2013-09)
      A novel miniaturized planar inverted F-L antenna assembly is considered for UWB radio operations. The antenna design utilizes the electromagnetic coupling between an air dielectric planar inverted-F antenna (PIFA) and a parasitic planar inverted-L (PIL) element, with broadband feeding from a rectangular plate. To improve the functionality of the channel, a simple notch filter has been introduced through a local modification to the broadband feed plate, this takes the form of a simple slotted rectangular spiral resonator which is etched directly onto the plate. This allows the proposed antenna to maintain its full band UWB coverage, with the HYPERLAN/2 band centered at 5.35 GHz to be effectively rejected over the sub-band 5.15–5.725 GHz, without the need for substantial re-optimization of its principal structure parameters. The impedance bandwidth operates over the full UWB band, with VSWR better than 2, this performance is not degraded by the presence of the band rejection. The observed gains, radiation patterns, and group delay confirm that the antenna has appropriate characteristics for short range wireless applications.
    • A comparison between vector algorithm and CRSS algorithm for indoor localization

      Dama, Yousef A.S.; Abd-Alhameed, Raed A.; Hammad, H.; Zaid, R.; Excell, Peter S. (2014)
      In this paper a comparison between two indoor localization algorithms using received signal strength is utilized the vector algorithm and the Comparative Received Signal Strength algorithm. The comparison considered the effect of the radio map resolution, the number of access points, and the operating frequency on the accuracy of the localization process. The experiments were carried out using ray tracing software, measured values and MATLAB.
    • A comprehensive study for indoor localization techniques using received signal strength

      Obeidat, Huthaifa A.N.; Abd-Alhameed, Raed A.; Elkhazmi, Elmahdi A.; Asif, Rameez; Usman, Muhammad; See, Chan H.; Elmegri, Fauzi; Ghazaany, Tahereh S.; Zhu, Shaozhen (Sharon); Noras, James M.; et al. (2013)
    • A Low-Profile Ultra-Wideband Modified Planar Inverted-F Antenna

      See, Chan H.; Hraga, Hmeda I.; Abd-Alhameed, Raed A.; McEwan, Neil J.; Noras, James M.; Excell, Peter S. (2013)
      A miniaturized modified planar inverted-F antenna (PIFA) is presented and experimentally studied. This antenna consists of a planar rectangular monopole top-loaded with a rectangular patch attached to two rectangular plates, one shorted to the ground and the other suspended, both placed at the optimum distance on each side of the planar monopole. The fabricated antenna prototype had a measured impedance bandwidth of 125%, covering 3 to 13GHz for reflection coefficient better than -10 dB. The radiator size was 20 x 10 x 7.5 mm(3), making it electrically small over most of the band and suitable for incorporation in mobile devices. The radiation patterns and gains of this antenna have been cross-validated numerically and experimentally and confirm that this antenna has adequate characteristics for short range ultra-wideband wireless applications.
    • A miniaturised monopole wideband antenna with reconfigurable band rejection for WLAN/WiMAX

      Elfergani, Issa T.; Hussaini, Abubakar S.; See, Chan H.; Rodriguez, Jonathan; Abd-Alhameed, Raed A.; Marques, P. (2015)
      This paper proposes a tuneable band-rejected miniaturised monopole antenna. The band-notching was achieved by printing an inner chorded crescent shape over the surface of the substrate. By placing a small varactor between the inner and outer arches, the centre frequency of each notch can be individually shifted downwards. The design of the proposed structure has a controllable rejection in the range from 2.38 to 3.87 GHz maintaining a wideband performance from 1.5 to 5 GHz based on VSWR ≤ 2. The antenna prototype was fabricated and tested. Simulated and measured results are performed and analysed. With a compact size, the proposed monopole antenna may well work as an internal antenna in a portable device.
    • A multi-service cluster-based decentralized group key management scheme for high mobility users

      Mapoka, Trust T.; AlSabbagh, Haider M.; Dama, Yousef A.S.; Shepherd, Simon J.; Abd-Alhameed, Raed A.; Bin-Melha, Mohammed S.; Anoh, Kelvin O.O. (2015)
      Previous cluster based group key management schemes for wireless mobile multicast communication lack efficiency in rekeying the group key if high mobility users concurrently subscribe to multiple multicast services that co-exist in the same network. This paper proposes an efficient multi-service group key management scheme suitable for high mobility users which perform frequent handoffs while participating seamlessly in multiple multicast services. The users are expected to drop subscriptions after multiple cluster visits hence inducing huge key management overhead due to rekeying the previously visited cluster keys. However we adopt our already proposed SMGKM system with completely decentralised authentication and key management functions to address demands for high mobility environment with same level of security and less overhead. Through comparisons with existing schemes and simulations, SMGKM shows resource economy in terms of rekeying communication overhead in high mobility environment with multi-leaves.
    • A new approach for implementing QO-STBC over OFDM

      Dama, Yousef A.S.; Migdadi, Hassan S.O.; Shuaieb, Wafa S.A.; Elkhazmi, Elmahdi A.; Abdulmula, E.A.; Abd-Alhameed, Raed A.; Hammoudeh, W.; Masri, A. (2015)
      A new approach for implementing QO-STBC and DHSTBC over OFDM for four, eight and sixteen transmitter antennas is presented, which eliminates interference from the detection matrix and improves performance by increasing the diversity order on the transmitter side. The proposed code promotes diversity gain in comparison with the STBC scheme, and also reduces Inter Symbol Interference.
    • A novel multi-standard dual-wide band polygon SLSIR filter

      Tu, Yuxiang X.; Ali, Ammar H.; Elmegri, Fauzi; Abousitta, M.; Abd-Alhameed, Raed A.; Hussaini, Abubakar S.; Elfergani, Issa T.; Rodriguez, Jonathan; Atiah, A.S. (2015)
      A novel multi-standard dual-wide band filter with a compact size of only 8.8 mm by 16.8mm is designed and developed for transceiver devices. The proposed filter has a fundamental bandwidth of 1.6GHz with fractional bandwidth (FBW) of 29.7% centered at the 5.4GHz band, and second bandwidth of 300.0MHz with FBW of 3.6% centered at the 8.15GHz band. The basic dual-wide bandwidth is attributed to the interaction of the novel modified polygon pair and upper stub loaded stepped impedance resonator. Moreover, the added down stub loaded stepped impedance resonator (SLSIR) further enhances the pass band performance by widening the bandwidth and optimizing reflection coefficient performance considerably. To validate the proposed ideas, the multi-standard filter is designed and simulated by Ansoft HFSS software. The simulated results agree well with the theory predictions. The featured broad bandwidths over two frequency bands and the miniaturized size of the proposed filter make it very promising for applications in future multi-standard wireless communication.
    • A printed wideband MIMO antenna for mobile and portable communication devices

      See, Chan H.; Elkhazmi, Elmahdi A.; Samarah, Khalid G.; Al Khambashi, Majid S.; Abd-Alhameed, Raed A.; McEwan, Neil J.; Excell, Peter S. (2015)
      A printed crescent-shaped monopole MIMO antenna is presented for handheld wireless communication devices. The mutual coupling between the two antenna elements can be minimised by implementing a I-shaped common radiator. Both the simulated and measured results agree that the antenna covers the operating frequency band from 1.6 to 2.8 GHz with the return loss and isolation better than 10 dB and 14 dB respectively. To further verifying the MIMO characteristic including far-field, gain, radiation efficiency, channel capacity loss and envelope correlation, the results confirm that the antenna can operate effectively in a rich multipath environment.
    • A review of location based services: current developments and trends

      Abd-Alhameed, Raed A.; Anoh, Kelvin O.O.; Ahmad, I.; Migdadi, Hassan S.O.; Asif, Rameez; Jan, Naeem A.; Ghazaany, Tahereh S.; Zhu, Shaozhen (Sharon); Elmegri, Fauzi; Bin-Melha, Mohammed S.; et al. (2013)
    • Absence of nonlinear responses in cells and tissues exposed to RF energy at mobile phone frequencies using a doubly resonant cavity

      Kowalczuk, C.; Yarwood, G.; Blackwell, R.; Priestner, M.; Sienkiewicz, Z.; Bouffler, S.; Ahmed, I.; Abd-Alhameed, Raed A.; Excell, Peter S.; Hodzic, V.; et al. (2010)
      A doubly resonant cavity was used to search for nonlinear radiofrequency (RF) energy conversion in a range of biological preparations, thereby testing the hypothesis that living tissue can demodulate RF carriers and generate baseband signals. The samples comprised high-density cell suspensions (human lymphocytes and mouse bone marrow cells); adherent cells (IMR-32 human neuroblastoma, G361 human melanoma, HF-19 human fibroblasts, N2a murine neuroblastoma (differentiated and non-differentiated) and Chinese hamster ovary (CHO) cells) and thin sections or slices of mouse tissues (brain, kidney, muscle, liver, spleen, testis, heart and diaphragm). Viable and non-viable (heat killed or metabolically impaired) samples were tested. Over 500 cell and tissue samples were placed within the cavity, exposed to continuous wave (CW) fields at the resonant frequency (f) of the loaded cavity (near 883 MHz) using input powers of 0.1 or 1 mW, and monitored for second harmonic generation by inspection of the output at 2f. Unwanted signals were minimised using low pass filters (</= 1 GHz) at the input to, and high pass filters (>/= 1 GHz) at the output from, the cavity. A tuned low noise amplifier allowed detection of second harmonic signals above a noise floor as low as -169 dBm. No consistent second harmonic of the incident CW signals was detected. Therefore, these results do not support the hypothesis that living cells can demodulate RF energy, since second harmonic generation is the necessary and sufficient condition for demodulation.
    • An Active Microwave Sensor for Near Field Imaging

      Mirza, Ahmed F.; See, Chan H.; Danjuma, Isah; Asif, Rameez; Abd-Alhameed, Raed A.; Noras, James M.; Clarke, Roger W.; Excell, Peter S. (2017)
      Near field imaging using microwaves in medical applications is of great current interest for its capability and accuracy in identifying features of interest, in comparison with other known screening tools. This paper documents microwave imaging experiments on breast cancer detection, using active antenna tuning to obtain matching over a wide bandwidth. A simple phantom consisting of a plastic container with a low dielectric material emulating fatty tissue and a high dielectric constant object emulating a tumor is scanned between 4 to 8 GHz with a UWB microstrip antenna. Measurements indicate that this prototype microwave sensor is a good candidate for such imaging applications.
    • Africa: cyber-security and its mutual impacts with computerisation, miniaturisation and location-based authentication

      Adeka, Muhammad I.; Anoh, Kelvin O.O.; Ngala, Mohammad J.; Shepherd, Simon J.; Ibrahim, Embarak M.; Elfergani, Issa T.; Hussaini, A.; Rodriguez, Jonathan; Abd-Alhameed, Raed A. (2017)
      The state of insecurity occasioned by fraudulent practices in Africa has been of concern economically, both at home and abroad. In this paper, we propose ways to mitigate this problem, using Nigeria as a case study. Based on surveys in West Africa, the paper examines the security situation in the continent and its mutual impacts with computerisation, miniaturisation and Location-Based Authentication (LBA). It was discovered that computerisation and miniaturisation had negative effects on cyber-security, as these were being exploited by fraudsters, using advance fee fraud; called 419. As a countermeasure, the paper examines the possibility of using LBA and digitisation of the GSM Mobile country codes down to city/area codes along with GSM/GPS authentications. These could also be combined with the use of a web-based Secret Sharing Scheme for services with very high security demands. The challenges of roaming were also examined and considered to be of negligible impact.
    • An evaluation of coded wavelet for multicarrier modulation with OFDM

      Anoh, Kelvin O.O.; Ghazaany, Tahereh S.; Hussaini, Abubakar S.; Abd-Alhameed, Raed A.; Jones, Steven M.R.; Rodriguez, Jonathan (2013)
      Orthogonal frequency division multiplexing (OFDM) is pronounced in wireless communication systems. Methods for improving the performance of the OFDM-based systems are mostly sought. A method of doing this involves error correction coding and another, a better multicarrier modulation kernel. In this work, convolutional error correction coding with interleaving is introduced in wavelet multicarrier modulation OFDM system (wavelet-OFDM) to improve the performance of multicarrier systems as the signal traverses the multipath and noisy transmission channels. This is compared with FFT-based multicarrier modulation (FFT-OFDM). Results show that coded wavelet-OFDM saves more than a half of the transmit power than the uncoded wavelet. Also it will be shown that, the interleaved and non-interleaved coded wavelet-OFDM well outperform interleaved coded and non-interleaved coded FFT-OFDM systems respectively.
    • An evaluation of spatial modulation for MIMO systems with QO-STBC

      Anoh, Kelvin O.O.; Dama, Yousef A.S.; AlSabbagh, Haider M.; Ibrahim, Embarak M.; Abd-Alhameed, Raed A.; Elmegri, Fauzi; Mapoka, Trust T.; Ngala, Mohammad J.; Jones, Steven M.R. (2015)
    • Analysis of Chiral and Achiral Medium Based Coplanar Waveguide Using Improved Full Generalized Exponential Matrix Technique

      Sayad, D.; Zebiri, C.; Elfergani, Issa T.; Rodriguez, Jonathan; Abd-Alhameed, Raed A.; Benabdelaziz, F. (RadioEngineering, 2020-12)
      In this work, an analytical study of the electromagnetic propagation in a complex medium-based suspended three-layer coplanar waveguide (CPW) is carried out. The study aims at a numerical calculation of the dominant hybrid mode complex propagation constant in the CPW printed on a bianisotropic substrate. The herein considered bianisotropy is characterized by full 3×3 tensors of permittivity, permeability and magnetoelectric parameters. The study is based on the numerical derivation of the Green's functions of such a complex medium in the spectral domain. The study is carried out using the Full Generalized Exponential Matrix Technique based on matrix- shaped compact mathematical formulations. The Spectral Method of Moments (SMoM) and the Galerkin's procedure are used to solve the resulting homogeneous system of equations. The effect of the chiral and achiral bianisotropy on the complex propagation constant is particularly investigated. Goo d agreements with available data for an anisotropic-medium-based suspended CPW structure are achieved. Various cases of chiral and achiral bianisotropy have been investigated, and particularly, the effect on the dispersion characteristics is presented and compared with cases of isotropic and bianisotropic Tellegen media.
    • Analysis of Improved µ-Law Companding Technique for OFDM Systems

      Ali, N.; Almahainy, R.; Al-Shabili, A.; Almoosa, N.; Abd-Alhameed, Raed A. (2017-08-21)
      High Peak-to-Average-Power Ratio (PAPR) of transmitted signals is a common problem in broadband telecommunication systems using an orthogonal frequency division multiplexing (OFDM) modulation scheme, as it increases transmitter power consumption. In consumer applications where it impacts mobile terminal battery life and infrastructure running costs, this is a major factor in customer satisfaction. Companding techniques have been recently used to alleviate this high PAPR. In this paper, a companding scheme with an offset, amidst two nonlinear companding levels, is proposed to achieve better PAPR reduction while maintaining an acceptable bit error rate (BER) level, resulting in electronic products of higher power efficiency. Study cases have included the effect of companding on the OFDM signal with and without an offset. A novel closed-form approximation for the BER of the proposed companding scheme is also presented, and its accuracy is compared against simulation results. A method for choosing best companding parameters is presented based on contour plots. Practical emulation of a real time OFDM-based system has been implemented and evaluated using a Field Programmable Gate Array (FPGA).