Papers by Haythem Abdullah
2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall)
Recently, the implementation of a complete RF transceiver system at the mm-wave band is of main i... more Recently, the implementation of a complete RF transceiver system at the mm-wave band is of main interest as the recent technological trend is to build a complete system on chip (SOC). One of the main keys of the transceiver systems is the voltage-controlled oscillator (VCO) which is considered the main building block of the phase locked loop (PLL) frequency synthesizer. Realizing VCO with wider tuning range (TR) and low phase noise at the mm-wave frequency range is considered a challenging task. In this work, a cross coupled differential pair Class-C voltage controlled oscillator is employed to improve the phase noise across wider tuning range. The proposed design is based on the 0.13 µm SiGe BiCMOS process technology. A new varactor circuit is proposed to extend the tuning range. In order to extend the tuning range of the VCO more and more, a bank of fixed capacitors is added to the LC tank with a controlled MOS switches. Multiple tuning ranges are achieved using the proposed LC tank. The EM effects of the paths and interconnections through the layout are taken into considerations before fabrication. The proposed LC VCO achieved maximum post-layout phase noise of −97 (dBc/Hz) at 1 MHz offset from the carries. In addition, it achieves a wide tuning range between 18.2 GHz to 26 GHz. Moreover, the proposed VCO consumes only 12 mW from 1.2 voltage supply.
Trends in Research on Microstrip Antennas, 2017
Advances in wireless communications have paved the way for wide usage of mobile phones in modern ... more Advances in wireless communications have paved the way for wide usage of mobile phones in modern society, resulting in mounting concerns surrounding its harmful radiation. Energy absorption in human biological tissues can be characterized by specific absorption rate (SAR). This value refers to the actual amount of electromagnetic energy absorbed in the biological tissues, thus a lower value of SAR indicates a lower radiation exposure risk to the human body. So, our challenge is to introduce mobile handset antennas with low SAR and operating at all mobile and wireless applications. In this chapter, novel configurations of single-element antenna are designed, simulated, fabricated, and measured. The antennas operate for most cellular applications: global system for mobile (GSM)-850/900, digital cellular system (DCS)-1800, personal communication service (PCS)-1900, universal mobile telecommunication system (UMTS)-2100, and long-term evolution (LTE) bands. The antennas also support wireless applications. The proposed antennas have a compact size and low SAR at all bands. Also, this chapter presents a comprehensive study on the performance of the antenna in the different environments. Furthermore, the antenna performance is tested in the presence of head and hand in free space and in a car. The simulation and measurement results are in good agreement.
This paper presents a novel structure for ultra broadband 4:1 broadside-coupled PCB impedance tra... more This paper presents a novel structure for ultra broadband 4:1 broadside-coupled PCB impedance transformer. Analysis, simulations and measurements of the developed transformer are given and discussed. Three prototypes of the proposed structure are implemented (Trafo I, Trafo II and Trafo III) at resonant frequencies 2.3, 1.3 and 0.85 GHz, respectively with fractional bandwidth (FBW) of greater than 400 %. The implemented transformers show an ultra broadband performance with a transmission loss of less than – 1 dB and return loss of at least – 10 dB in the desired bandwidth. In a comparison, simulations and measurements are found very close to each other. To the knowledge of the authors, the achieved performance of the designed transformers has been never obtained in the literature. Index Terms — Broadband, impedance transformer, PCB, broadside-coupled.
2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2018
This paper introduces an antenna for Automotive Radar to operate at 77 GHz. The proposed antenna ... more This paper introduces an antenna for Automotive Radar to operate at 77 GHz. The proposed antenna consists of a hybrid radiator and dielectric resonator. The hybrid radiator is a circular patch that feed by aperture method and the dielectric resonator is ring that feed by the circular patch to operate at 77 GHz with high gain 12 dB for one element. The EBG structure is implemented on the top layer to widens the proposed band, gives high gain and to reduce surface waves. The compact size of one element 3.5mm×3.5mm×l.16mm to operate from 75.3 GHz to 80 GHz with gain 12.3 dB.
2018 35th National Radio Science Conference (NRSC), 2018
The most common chipless RFID tags depends on the existence of a set of resonators inserted betwe... more The most common chipless RFID tags depends on the existence of a set of resonators inserted between two orthogonal antennas in order to increase the response of the reader system. In this paper, an orientation independent tag without the two antennas but with a high response is proposed. The tag design is based on etching circular slots on one layer of a substrate without ground. The symmetry of the tag is the reason behind the orientation independent response. The circular set of resonators are repeated in different space distribution to increase the back scattered signal of the tag in order to reach the response of the two antennas of the conventional chipless tags. The proposed tag reveals high frequency response, compact size and at the same time orientation independent compared to other chipless RFID tags. The proposed tags are suitable for banknotes, credit card applications and similar applications.
The method of moment solution of the volume integral equation suffers from singular volume integr... more The method of moment solution of the volume integral equation suffers from singular volume integrals. When applying the gradient-gradient operator on the green’s function, it allows the choice of piecewise constant function for the expansion and testing functions. But it results in strong singularities of order . In this paper, robust and accurate technique based on the use of Raw, Wilton and Glisson, RWG, basis functions on tetrahedrons is applied. The RWG function is used both as a testing and as a basis functions. The proposed approach divides the integrals into two parts, one slowly varying nonsingular part which can be integrated numerically over the volume of the tetrahedrons and a singular part which will be converted into surface integrals of integrands R and that has analytical solutions. Also, a proposed fast and accurate numerical approach is presented to solve the nonsingular integral part. Validation of the proposed technique is presented. Very good results are obtained...
Progress In Electromagnetics Research B, 2020
In this paper, a new super-resolution and highly stable DOA estimation technique of coherent sour... more In this paper, a new super-resolution and highly stable DOA estimation technique of coherent sources is introduced. Furthermore, the proposed technique is applied to the data collected from the AWR1243 mm-wave 76–81 GHz frequency modulated continuous wave (FMCW) radar to estimate the DOAs of real targets. A virtual antenna array is proposed to increase the array aperture size and the dimension of the data covariance matrix which effectively helps in de-correlating the received signals and in increasing the number of detectable sources and hence improving the detection resolution. Moreover, a significant improvement in the DOA estimation capability is achieved by handling the frequency domain of the received signals instead of their time-domain representations. That is because the signal to noise ratio (SNR) is increased by a multiplication factor when it is transformed using FFT which acts as a filter for the noise. The simulation results proved the superiority of the proposed techn...
2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), 2018
With the vast spread of the RFID applications in most field of life's, most researchers pays ... more With the vast spread of the RFID applications in most field of life's, most researchers pays more attention to the most cheap but challenging technology in the RFID which is the chipless RFID. The challenges in such a technology stems from the need for a reader antenna that achieve an UWB operation, circular polarization, flat gain and a compact size. This is suitable for tags of either linear or circular orientations. This paper discusses the design, the simulation and the measurement of a quadrifilar spiral antenna with four-arms and six-turns that suits the RFID reader specifications. The antenna is fabricated over FR4 material of thickness 1.6 mm using the photolithographic process. The antenna arms are printed on one side of the substrate while the feeding coaxial connector is mounted on the other side without any ground planes. The radiation pattern and the polarization are controlled by adjusting the phase shift between the four arms. The four arms allow a total length le...
2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall), 2019
In this paper, a novel algorithm is presented for moving vehicles detection using 77 GHz automoti... more In this paper, a novel algorithm is presented for moving vehicles detection using 77 GHz automotive radars. Unlike previous methods, that use FFT estimators with CFAR based threshold detection to detect moving and fixed targets, we use the CFAR method combined with an adjustable coefficient based on the FFT algorithm output moments. It is found that, low false alarm rates are achieved using the proposed method. Furthermore, the proposed method is insensitive to the data window size in time domain as well as its low complexity relative to other methods.
IEEE Access, 2020
Cognitive radio (CR) is perceived as an intelligent solution to the incompetence of spectrum util... more Cognitive radio (CR) is perceived as an intelligent solution to the incompetence of spectrum utilization. The efficacy of any CR system depends on the accuracy of the spectrum sensing (SS) technology used. Therefore, the SS is considered as a substantial task of the CR systems. In this paper, the SS is handled by a different perspective as a goodness of fit hypothesis testing problem. Therefore, a T-Test based spectrum sensing (TTBSS) algorithm is proposed based on the statistical properties of the student's t-distribution. It does not require any prior knowledge of the primary user (PU) signal. It determines the PU absence/presence by calculating the dissimilarity between the two samples means of the received signal when the PU is present and when the PU is absent. Closed-form expressions for the probability of detection, probability of false alarm, and their associated thresholds are derived considering both single-input multi-output (SIMO) and multi-input multi-output (MIMO) systems configurations. The simulations revealed that the proposed algorithm is superior to the other state-of-the-art PU detection algorithms particularly at low signal-to-noise ratios (SNR) and few samples conditions. Moreover, the TTBSS addressed many problems that restrict the performance of the SS process such as noise uncertainty and interference. In addition, the numerical results are highly matched to the theoretical analyses.
Sensors, 2021
Collision avoidance and autonomous control of vehicles have become essential needs for providing ... more Collision avoidance and autonomous control of vehicles have become essential needs for providing a high-quality and safe life. This paper introduces a new generic scheme for a virtual antenna array (VAA) and its application in a train collision-avoidance system (TCAS). The proposed TCAS shall have the capability of identifying the range and angle of an object in front of a moving train and provide the required alerts. Thereby, a new virtual array distribution for both the transmitting and the receiving antenna arrays is introduced to get a long-range object detection and high-resolution multi-input multi-output (MIMO) system. This can be accomplished because the VAA radiation pattern is the multiplication of the radiation patterns for both the transmitting and receiving antenna arrays, which is different than each one of them alone. In this work, the VAA is utilized in radar systems in which the radar range depends on the multiplication of the gain of the transmitting and receiving ...
Journal of Infrared, Millimeter, and Terahertz Waves, 2021
In this paper, a novel design for a 5G base station (BS) antenna is proposed. The proposed antenn... more In this paper, a novel design for a 5G base station (BS) antenna is proposed. The proposed antenna consists of two orthogonally polarized antennas. The two antennas are modified compact Vivaldi antennas operating in the two recommended 5G operating bands; 28 and 38 GHz with measured impedance bandwidth of 26.5–40 GHz. The orthogonality of the two antennas allows the use of two antennas on the same substrate within one enclosure to serve two sectors separately. So, instead of using two enclosures to serve two sectors, only one enclosure is required. The two elements may be part of two separate MIMO distributions. To minimize the isolation between the MIMO antennas elements with low complexity and low cost, the antenna elements have been distributed along the z-direction with half-wavelength spacing between elements including Electromagnetic band-gap (EBG) structure in between them. The simulation results have been shown that the measured mutual coupling between the array elements is improved from − 32 to − 45 dB at 28 GHz and from − 22 to − 59 at 38 GHz. The envelope correlation coefficient (ECC) is enhanced and the diversity gain (DG) is improved simultaneously. The suggested structure has been designed on CST Microwave Studio 2019. The two orthogonal antennas’ overall size approaches 34 mm × 55.8 mm × 0.203 mm 3 . The measured gain of the suggested design is enhanced from 10.4 to 12.8 dB at 28 GHz whereas a minor change is noticed at 38 GHz. The maximum simulated radiation efficiency approaches 96%. The antenna is fabricated and tested where good experimental results are noticed compared to the simulation results.
Sensors, 2020
This paper introduces a novel antenna array synthesis for radar systems based on the concept of a... more This paper introduces a novel antenna array synthesis for radar systems based on the concept of a virtual antenna array (VAA) and the method of moments/genetic algorithm (MoM/GA) synthesis method. The VAA concept is applied to both scanning and fixed radiation pattern arrays. The proposed VAA is introduced to simultaneously support the medium-range radar (MRR) and the long-range radar (LRR) with beam width ±7° for LRR and ±37° for MRR. The proposed VAA is distinguished by its minimum number of antenna elements, simple feeding network, high efficiency, and gain, but all of these are at the expense of a large aperture antenna size compared to the planar antenna array (PAA). The VAA has the ability to have the feeding network and the radiating elements on the same layer, as compared to the multilayer PAA. The newly proposed concept is analyzed and verified analytically and experimentally. Two orthogonal (16 elements) VAAs are designed to operate in the frequency range from 23.55 to 24....
Progress In Electromagnetics Research C, 2019
Distributed beamforming (DBF) is an efficient technique for reliable communications in wireless s... more Distributed beamforming (DBF) is an efficient technique for reliable communications in wireless sensor networks (WSNs). In DBF based networks, the randomly distributed nodes cooperate to form a randomly distributed antenna array (RAA) which has a main beam directed towards the intended receiver. Due to the nodes randomness, the DBF results in poor pattern characteristics such as high side lobe level (SLL) and pattern asymmetry around the main beam sides. In this paper, a fast deterministic algorithm for SLL reduction of open loop distributed antenna arrays is introduced. Unlike the existing state of the art optimization techniques for SLL reduction, the proposed algorithm provides a fast deterministic solution for energy transmission or the weight of each node without changing its location. Consequently, the exhaustive search burden of the optimization based techniques for the optimum weights is avoided. The simulation results reveal that the proposed algorithm has superior performance to the optimization techniques in terms of execution time, synthesized SLL, and half power beamwidth (HPBW).
IEEE Antennas and Wireless Propagation Letters, 2019
In this letter, a new design for two-port transmit/receive (Tx/Rx) full-duplex microstrip patch a... more In this letter, a new design for two-port transmit/receive (Tx/Rx) full-duplex microstrip patch antenna for 4G and 4G advanced communication systems is introduced. The proposed duplex antenna consists of a single gear-shaped radiating patch for bidirectional radiation. The isolation between transmit and receive ports is achieved by using a frequency space filtering technique where two omega-shaped defected ground structure (DGS)-based bandpass filters (BPFs) are created at transmit and receive ports of the antenna. The antenna achieves a compact size of <inline-formula><tex-math notation="LaTeX">$\ ({{\text{70} \times \text{70}}})\text{ mm}^\text{2}$</tex-math></inline-formula>, high isolation larger than <inline-formula><tex-math notation="LaTeX">$ - \text{36}\;\text{dB}$</tex-math></inline-formula> at the transmit frequency <inline-formula><tex-math notation="LaTeX">${{f}_{t}} = \text{3.3}\;\text{GHz}$</tex-math></inline-formula> and larger than <inline-formula><tex-math notation="LaTeX">$ - \text{45}\;\text{dB}$</tex-math></inline-formula> at the receive frequency <inline-formula><tex-math notation="LaTeX">${{f}_{r}} = \text{3.215}\;\text{GHz},$</tex-math></inline-formula> and small Tx–Rx frequency space ratio <inline-formula><tex-math notation="LaTeX">${r} = \text{0.0245}$</tex-math></inline-formula>. Also, the proposed structure can cover the entire S-band from <inline-formula><tex-math notation="LaTeX">$\text{2}$</tex-math></inline-formula> to <inline-formula><tex-math notation="LaTeX">$\text{4}\;\text{GHz}$</tex-math></inline-formula> by scaling the sizes of the omega-shaped DGSs to control the resonance frequencies of the embedded BPFs before fabrication. Furthermore, the embedded BPFs have sharp cutoff characteristics, high selectivity, and channel bandwidth of about <inline-formula><tex-math notation="LaTeX">${BW} \leq \text{790}\;\text{MHz}$</tex-math></inline-formula> at<inline-formula><tex-math notation="LaTeX">$| {{{s}_{11}}} | = | {{{s}_{22}}} | = - \text{10}\;\text{dB}$</tex-math></inline-formula>. The simulation and measurement results highly coincide.
IET Microwaves, Antennas & Propagation, 2019
In most of the crowded cities and with the vast increase of capacity-hungry applications, operato... more In most of the crowded cities and with the vast increase of capacity-hungry applications, operators tend to use capacity enhancement techniques such as MIMO, OFDMA etc. Authors’ problem is completely different. In several rural areas, the needed capacity is very low and the single base station has a standard capacitance which is considered over sufficient with respect to the required spectrum in these rural areas. The solution to make the best use of such resources is to design a two-sector antenna with a single feed. The proposed antenna covers two areas simultaneously. Thus, the spectrum capability is distributed over two sectors that share the available frequency resources. If the total area is small enough, then the base station power will be saved to the half as well as the number of antennas also reduced to the half. Otherwise, the concept of frequency reuse can be applied with minimum base stations. Authors’ antenna is designed over FR-4 substrate with a noticeable reduction in the cost. A very good agreement between the simulated and measured results is noticed .
Engineering Science and Technology, an International Journal, 2017
Side lobe level (SLL) reduction has a great importance in recent communication systems. It is con... more Side lobe level (SLL) reduction has a great importance in recent communication systems. It is considered as one of the most important applications of digital beamforming since it reduces the effect of interference arriving outside the main lobe. This interference reduction increases the capacity of the communication systems. In this paper, the hardware implementation of an antenna array system for SLL reduction is introduced using microstrip technology. The proposed antenna array system consists of two main parts, the antenna array, and its feeding network. Power dividers play a vital role in various radio frequency and communication applications. A power divider can be utilized as a feeding network of an antenna array. For the synthesis of a radiation pattern, an unequal-split power divider is required. A new design for a four ports unequal circular sector power divider and its application to antenna array SLL reduction is introduced. The amplitude and phase of the signals emerging from each power divider branch are adjusted using stub and inset matching techniques. These matching techniques are used to adjust the branches impedances according to the desired power ratio. The design of the antenna array and the power divider are made using the software package CST MICROWAVE STUDIO. The power divider is realized on Rogers R03010 substrate with dielectric constant e r ¼ 10:2, loss tangent of 0.0035, and height h ¼ 1:28 mm. In addition, a design for ultra-wide band (UWB) antenna element and array are introduced. The antenna elements and the array are realized on the FR4 (lossy) substrate with dielectric constant e r ¼ 4:5, loss tangent of 0.025, and height h ¼ 1:5 mm. The fabrication is done using thin film technology and photolithographic technique. The experimental measurements are done using the vector network analyzer (VNA HP8719Es). Good agreement is found between the measurements and the simulation results.
Microwave and Optical Technology Letters, 2016
This article presents a comprehensive study on the performance of a compact multiband antenna ope... more This article presents a comprehensive study on the performance of a compact multiband antenna operating in LTE700, GSM850, GSM 900, DCS1800, PCS 1900, UMTS 2100, most of LTE bands (especially the low-frequency LTE 700 band), and wireless applications. The antenna consists of a monopole in conjunction with meander line antenna. An EBG structure is used to miniaturize the antenna size and to enhance the gain in the direction away from the antenna to lower the SAR within the human body. The EBG structure also contributes in open the operating bands. The proposed antenna is tested using the four recommended test positions of the CTIA association where the proposed antenna reveals good performance in all test cases. Return loss, radiation patterns, SAR, and efficiency of this antenna are computed in free space, in the presence of handset (keypad, battery, speaker camera, RF circuit, and LCD) in talking position, in standby position, in packaging, and as well as in the presence of head and hand in free space and in a car. The SAR values are taken into account not to exceed the standard safety levels. In addition, radiation efficiencies of these handset antennas are computed in the presence of head and hand. All simulation results are performed using the CST software. Simulation results are in good agreement with the measurement results. V
ABSTRACT In some applications, where, the scanning rate is not a critical factor, mechani-cally r... more ABSTRACT In some applications, where, the scanning rate is not a critical factor, mechani-cally rotating system is sufficient to do fixed beamwidth scanning. The electronic scanning is an optimum solution to the high scanning rate applications, but it suffers from the beamwidth broadeningand gain variations with steering angles. In this paper, a fixed beamwidth electronic scanning algorithm is proposed. The proposed algorithm is based on synthesizing sets of exci-tation coefficients to direct the main beam at some scanning angles. The synthesis takes into consideration the fixation of the beamwidth at these angles. The synthesis of the excitation coefficients will be done using a scheme based on the moment method due to its accuracy in solving such problems. The optimum spacing between elements will be determined using the genetic algorithm. One of the main advantages of the proposed algorithm is the applicability of synthesizing multibeam antenna array of fixed beamwidths using the superposition principle.
ABSTRACT Side lobe level (SLL) reduction has a great importance in recent communication systems. ... more ABSTRACT Side lobe level (SLL) reduction has a great importance in recent communication systems. It is considered as one of the most important applications of digital beamforming since it reduces the effect of interference arriving outside the main lobe. This interference reduction increases the capacity of the communication systems. In this paper, our home made synthesis scheme that is based on the Method of Moments and the Genetic Algorithm to synthesize linear antenna arrays is utilized. The algorithm accepts a desired radiation pattern and provides the excitation coefficients that realize the required pattern. If this pattern is applied to the synthesis scheme, it results in the optimum element spacing and the excitation coefficients that lead to maximum SLL reduction with a minimum number of array elements. The MoM/GA scheme provides SLL reduction with exactly the same half power beamwidth (HPBW) as the original array pattern.
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Papers by Haythem Abdullah