• 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.
    • Design of very compact Combline Band-Pass Filter for 5G applications

      Al-Yasir, Yasir; Abd-Alhameed, Raed A.; Noras, James M.; Abdulkhaleq, Ahmed M.; Ojaroudi Parchin, Naser (2018-11-13)
      In this paper, a compact microstrip band-pass filter (BPF) covering the 3.4 to 3.8 GHz spectrum bandwidth for 5G wireless communications is presented. The planar filter uses three resonators, each terminated by a via to hole ground at one end and a capacitor at the other end with 50 Ω transmission line impedances for input and output terminals. The coupling between the lines is adjusted to resonate at the centre frequency with third-order band-pass Butterworth properties. The proposed combline filter is designed on an alumina substrate with a relative dielectric constant of 9.8 and a very small size of 9×5×1.2 mm3. The proposed filter is simulated and optimized using CST microwave studio software.
    • Evaluation of focused array configurations for near field applications

      Abdulkhaleq, Ahmed M.; Sayidmarie, Khalil H.; Elkhazmi, Elmahdi A.; Abd-Alhameed, Raed A.; Excell, Peter S. (2013)
    • Frequency Reconfigurable Antenna Array for MM-Wave 5G Mobile Handsets

      Ojaroudi Parchin, Naser; Al-Yasir, Yasir; Abdulkhaleq, Ahmed M.; Elfergani, Issa T.; Rayit, A.; Noras, James M.; Rodriguez, Jonathan; Abd-Alhameed, Raed A. (2018-09-20)
      This study proposes a compact design of frequency-reconfigurable antenna array for fifth generation (5G) cellular networks. Eight compact discrete- fed slot antennas are placed on the top portion of a mobile phone printedcircuit- board (PCB) to form a beam-steerable array. The frequency response of the antenna can be reconfigured to operate at either 28 GHz or 38 GHz, two of the candidate frequency bands for millimeter-wave (MM-Wave) 5G communications. The reconfigurability function of the proposed design can be achieved by implementing and biasing a pair of diodes across each T-shaped slot antenna element. Rogers RT 5880 with thickness of 0.508 mm and properties of ε = 2.2 and δ = 0.0009 has been used as the antenna substrate. The antenna element is very compact in size with a good end-fire radiation pattern in the frequency bands of interest. The proposed beam-steerable array provides very good 3D coverage. The simulation results show that the proposed design provides some good characteristics fitting the need of the 5G cellular communications.
    • Noise cancellation for compact MIMO systems

      Abdulkhaleq, Ahmed M.; Ali, N.T.; Abd-Alhameed, Raed A.; Sayidmarie, Khalil H.; See, Chan H.; Noras, James M.; Excell, Peter S. (2013)
      A proposed method for cancelling or reducing the effect of the transmitted power within the transceiver MIMO unit is investigated and discussed using a feedback signal process between the elements. Several parameters including the level of feedback power mismatch, the transmitted power and the received power are considered in this work to test the performance of the system in term of the bit error rate (BER) versus signal to noise ratio (SNR). A new software programme using MATLAB is implemented to evaluate the proposed method. The results showed that the performances of the system are heavily dependent on the amount of the transmitted power, the received power, and the mismatch in the feedback component.
    • The Performance of SLNR Beamformers in Multi-User MIMO Systems

      Hameed, Khalid W.H.; Abdulkhaleq, Ahmed M.; Al-Yasir, Yasir; Ojaroudi Parchin, Naser; Rayit, A.; Al Khambashi, M.; Abd-Alhameed, Raed A.; Noras, James M. (2018-09-20)
      Beamforming in multi-user MIMO (MU-MIMO) systems is a vital part of modern wireless communication systems. Researchers looking for best operational performance normally optimize the problem and then solve for best weight solutions. The weight optimization problem contains variables in numerator and dominator: this leads to so-called variable coupling, making the problem hard to solve. Formulating the optimization in terms of the signal to leakage and noise ratio (SLNR) helps in decoupling the problem variables. In this paper we study the performance of the SLNR with variable numbers of users and handset antennas. The results show that there is an optimum and the capacity curve is a concave over these two parameters. The performances of two further variations of this method are also considered.
    • Recent Progress in the Design of 4G/5G Reconfigurable Filters

      Al-Yasir, Yasir; Ojaroudi Parchin, Naser; Abd-Alhameed, Raed A.; Abdulkhaleq, Ahmed M.; Noras, James M. (2019-01-20)
      Currently, several microwave filter designs contend for use in wireless communications. Among various microstrip filter designs, the reconfigurable planar filter presents more advantages and better prospects for communication applications, being compact in size, light-weight and cost-effective. Tuneable microwave filters can reduce the number of switches between electronic components. This paper presents a review of recent reconfigurable microwave filter designs, specifically on current advances in tuneable filters that involve high-quality factor resonator filters to control frequency, bandwidth and selectivity. The most important materials required for this field are also highlighted and surveyed. In addition, the main references for several types of tuneable microstrip filters are reported, especially related to new design technologies. Topics surveyed include microwave and millimetre wave designs for 4G and 5G applications, which use varactors and MEMSs technologies.