Browsing by Author "Gürdal, Armağan"

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    ItemOpen Access
    60W stacked-HEMT based asymmetric X-band GaN SPDT switch for single chip T/R modules
    (IEEE - Institute of Electrical and Electronics Engineers, 2023-10-25) Ertürk, Volkan; Gürdal, Armağan; Çankaya Akoğlu, Büşra; Özbay, Ekmel
    This paper presents a high-power, asymmetric single-pole double-throw (SPDT) monolithic microwave integrated circuit (MMIC) switch using high electron mobility transistors (HEMT) with AlGaN/GaN technology for single chip X-band T/R modules. The SPDT switch is designed in series-shunt topology for high-power handling and low-loss performance. For high-power handling, shunt-stacked HEMTs on the transmit (Tx) path and series-stacked HEMTs on the receive (Rx) path are used. In its Tx mode, the switch has achieved an insertion loss better than 0.75 dB throughout the 6-13 GHz bandwidth with a return loss of 14 dB and an isolation of 28 dB. It can handle more than 60 W RF input power at 0.1 dB compression. In its Rx mode, the switch can receive signals with an insertion loss lower than 1.15 dB with 14 dB return loss and 19 dB isolation. With its low insertion and high-power handling capacity from C-band to Ku-band, this switch shows state-of-the-art performance for communication systems.
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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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    Robustness of GaN on SiC low-noise amplifiers in common source and cascode configurations for X-band applications
    (John Wiley & Sons Ltd., 2024-08) Nawaz, Muhammad Imran; Zafar, Salahuddin; Gürdal, Armağan; Akoğlu, Büşra Çankaya
    Cascode HEMTs exhibit high gain and broadband performance. Promising reverse transmission makes matching networks simpler and insensitive to impedance on either side of the HEMT. On the other hand, common source (CS) HEMTs with intentional small inductance at the source provide simultaneous match for optimum noise and input impedance. This paper provides a performance comparison of 4 x 50 mu m cascode HEMTs-based low -noise amplifier and 4 x 50 mu m CS HEMTs-based low -noise amplifiers with specific emphasis on robustness, including survivability and reverse recovery time (RRT). Cascode LNA survives an input power of 33 dBm while CS LNA handles 30 dBm power, each having a 1 k Omega passive limiting resistor on the gate bias line. RRT of cascode LNA is also better. Better survivability and RRT for cascode LNA are attributed to its HEMT's stacked configuration. The designs of LNAs are described, along with their small -signal, noise, and large -signal characteristics in the X -band. Cascode LNA has a better input match, while CS LNA has a better output match. Gains are comparable, while CS LNA has better P1dB at higher band edge frequency. The noise figure for both LNAs is less than 1.9 dB, with CS LNA having a slight edge over cascode. This study benefits RF designers in choosing appropriate HEMT topology as per application for designing robust low -noise amplifiers.
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    X band GaN based MMIC power amplifier with 36.5dBm P1-dB for space applications
    (IEEE, 2018) Gürdal, Armağan; Yılmaz, Burak Alptuğ; Cengiz, Ömer; Sen, Özlem; Özbay, Ekmel
    An X-Band Monolithic Microwave Integrated Circuit (MMIC) High Power Amplifier (HPA) with coplanar waveguide (CPW) based on AlGaN/GaN on SiC technology is presented in this paper. Coplanar waveguide technology (CPW) is chosen for the simplicity and reduced cost of fabrication since CPW process has no via. High Electron Mobility Transistors (HEMTs) are matched for the 8 GHz-8.4GHz frequency band for maximum output power. The Amplifier has a small signal gain over 10 dB, output power of 36.5dBm at 1 dB gain compression point (P1dB) and 40% power added efficiency (PAE) at (PldB) in the desired frequency band (8 GHz-8.4 GHz) with Vds = 30V.
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    X Band GaN Based MMIC power amplifier with 36.5dBm P1-dB for space applications
    (IEEE, 2018) Gürdal, Armağan; Yilmaz, Burak Alptug; Cengiz, Ömer; Şen, Özlem; Özbay, Ekmel
    An X-Band Monolithic Microwave Integrated Circuit (MMIC) High Power Amplifier (HPA) with coplanar waveguide (CPW) based on AIGaN/GaN on SiC technology is presented in this paper. Coplanar waveguide technology (CPW) is chosen for the simplicity and reduced cost of fabrication since CPW process has no via. High Electron Mobility Transistors (HEMTs) are matched for the 8 GHz-8.4GHz frequency band for maximum output power. The Amplifier has a small signal gain over 10 dB, output power of 36.5dBm at 1 dB gain compression point (P1dB) and 40% power added efficiency (P AE) at (PldB) in the desired frequency band (8 GHz-8.4 GHz) with Vds = 30V.