Browsing by Subject "X-band"

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    ItemOpen Access
    Design of an X-band GaN based microstrip MMIC power amplifier
    (2019-02) Özipek, Ulaş
    RF power amplifiers are crucial components of modern radar and communication systems. However, their design poses some challenges due to device limitations in high power and high frequency regime, as well as inherent difficulties of designing for nonlinear large-signal device operation. Gallium Nitride (GaN) based High Electron Mobility Transistors (HEMT) are promising candidates due to their superior material qualities, high power densities and ability to operate up to mm-wave frequencies. In this thesis, 0.25 μm GaN on SiC microfabrication process of Bilkent University Nanotechnology Research Center (NANOTAM) is presented. Transistor characterization procedure is demonstrated. Ideal transistor layout for design goals is selected and the transistor gate structure is optimized for X-band performance. A model library for microstrip passive circuit elements based on electromagnetic simulations has been developed. Finally, design and measurements of an X-band microstrip Class AB two-stage Monolithic Microwave Integrated Circuit (MMIC) PA, based on the same process are presented in detail. With die sizes smaller than 4.3 mm by 2.3 mm, fabricated MMICs operate at 8.5 - 11.5 GHz band with 24 dB small-signal gain. More than 13.5 W (41.3 dBm) output power (P6dB) and 31 - 38 % power-added efficiency are achieved throughout the 8.5 - 11 GHz band in pulsed mode on-wafer measurements.
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    ItemOpen Access
    GaN based LNA MMICs for X-band applications
    (Institute of Electrical and Electronics Engineers, 2020) Zafar, Salahuddin; Osmanoğlu, Sinan; Öztürk, Mustafa; Çankaya, Büşra; Yılmaz, Doğan; Kashif, A. U.; Özbay, Ekmel
    In this paper, we report two low noise broadband amplifiers based on ABMN's AlGaN/GaN on SiC HEMT technology for X-band applications. Two design topologies, a single-stage (LNA-1) and a two-stage (LNA-2), have been investigated. LNA-1 and the first stage of LNA-2 is based on common source (CS) with inductive source degeneration topology. LNA-1 has a flat gain response of ±1.4 dB gain variation with a gain greater than 8 dB for 9 V drain voltage and 100 mA/mm drain current. Input return loss better than 9.8 dB and output return loss better than 12.8 dB have been achieved. The simulated value of noise figure for this design is less than 1.4 dB. In LNA-2 design, a two-stage topology is implemented to enhance amplifier's gain. The simulated values for LNA-2 show a gain greater than 16.8 dB with ±2.9 dB gain variation. Input and output return loss values are better than 8.8 dB and 10 dB, respectively. The value of noise figure for this design is less than 1.7 dB in the desired frequency range. Both designs, having state-of-the art small dimensions, are suitable for their potential applications for space communications, Radar, satellite communications etc.
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    ItemOpen Access
    GaN-based single stage low noise amplifier for X-band applications
    (IEEE, 2022-07-18) Çağlar, Gizem Tendürüs; Aras, Yunus Erdem; Urfalı, Emirhan; Yılmaz, Doğan; Özbay, Ekmel; Nazlıbilek, Sedat
    Source degenerated HEMTs are used to achieve good noise matching and better input return loss without degrading the noise figure and reducing the stability. This work presents an MMIC design for the frequency band of 8–11 GHz by using HEMTs with source degeneration in 0.15 µm GaN on SiC technology. All design work is done in the Advanced Design System. The LNA delivers more than 6.9 dB gain with better than 8.5 dB and 9.5 dB input and output return losses, respectively. In addition, the gain ripple is around 2.7 dB. The noise figure of the amplifier is achieved below 1.1 dB with P1dB of 17.2 dBm and %12.7 drain efficiency within the operating bandwidth at the bias conditions of 9 V /20 mA.
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    ItemOpen Access
    A high gain and high efficiency 15 W X-Band GaN power amplifier MMIC
    (IEEE, 2019) Gürdal, Armağan; Özipek, Ulaş; Sütbaş, Batuhan; Özbay, Ekmel
    An X-band microstrip power amplifier MMIC based on our 0.25 μm AlGaN/GaN on SiC process technology is presented in this work. Fabrication steps, HEMT structure and typical device performance are demonstrated. Design procedure of the three-stage power amplifier MMIC with a compact size of 4.7 mm × 2.7 mm is described. Small-signal measurements of the fabricated MMICs typically show 36 dB gain with 5 dB ripple and input/output return losses better than 16 dB and 7 dB from 8.5 GHz to 12 GHz band, respectively. Typical output power of 15 W at 6 dB compression with 37%-44% power added efficiency is achieved under pulsed operation. MMIC power measurements performed at different base plate temperatures and bias conditions are also provided. This design exhibits significantly higher gain and much better input return loss compared to MMICs in the literature with similar size, efficiency and output power parameters.
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    ItemOpen Access
    Metamaterial Absorber Based Multifunctional Sensor Application
    (Institute of Physics Publishing, 2017) Ozer Z.; Mamedov, Amirullah; Özbay, Ekmel
    In this study metamaterial based (MA) absorber sensor, integrated with an X-band waveguide, is numerically and experimentally suggested for important application including pressure, density sensing and marble type detecting applications based on rectangular split ring resonator, sensor layer and absorber layer that measures of changing in the dielectric constant and/or the thickness of a sensor layer. Changing of physical, chemical or biological parameters in the sensor layer can be detected by measuring the resonant frequency shifting of metamaterial absorber based sensor. Suggested MA based absorber sensor can be used for medical, biological, agricultural and chemical detecting applications in microwave frequency band. We compare the simulation and experimentally obtained results from the fabricated sample which are good agreement. Simulation results show that the proposed structure can detect the changing of the refractive indexes of different materials via special resonance frequencies, thus it could be said that the MA-based sensors have high sensitivity. Additionally due to the simple and tiny structures it could be adapted to other electronic devices in different sizes. © Published under licence by IOP Publishing Ltd.
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    X-band cascode LNA with bias-invariant noise figure using 0.15 µm GaN-on-SiC technology
    (IEEE, 2022-07-18) Nawaz, Muhammad Imran; Aras, Yunus Erdem; Zafar, Salahuddin; Akoğlu, Büşra Çankaya; Tendürüs, Gizem; Özbay, Ekmel
    Cascode HEMTs exhibit better stability and broad bandwidths performance as compared with common source HEMTs. This paper presents the design of a single stage broadband low noise amplifier based upon 0.15 um GaN HEMT technology in the frequency range of 8 – 12 GHz. Cascode HEMT with inductive source degeneration is utilized. All the design work is done using PathWave Advanced Design System. The LNA provides 9.5 to 10.6 dB with input return loss better than 10 dB and output return loss better than 8 dB in the whole band. The noise figure of the amplifier is below 1.9 dB. The linearity parameters P1dB and OIP3 are greater than equal to 16 dBm and 28 dBm respectively within operating bandwidth. The noise figure of the amplifier is fairly constant over 30 mA to 60 mA bias currents and 9 V – 18 V operating bias voltage. This is a unique finding which is being reported for the first time to the best of authors' knowledge.