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Browsing by Institution Author "AKGİRAY, Ahmed Halid"

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    Broadband high power amplifier design using GaN HEMT technology
    (IEEE, 2021) Turt, Doğancan; Akgiray, Ahmed Halid; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid
    This paper presents the design and measurements of a broadband GaN HEMT power amplifier intended for point-to-point radios, electronic warfare systems, and test and measurement applications. The proposed power amplifier is fabricated, and small/large-signal measurements are collected. Fabricated design is conducted for an input power of 26 dBm and obtained between 39.6 - 40.9 dBm output power. Power added efficiency (PAE) of 45.9 % to 61.4 % is reached over the band (0.5 - 2.5 GHz). In this study, Wolfspeed's CGH40010F transistor is used in CW mode. In order to decide optimum source and load impedances of the transistor, load- source-pull simulations are conducted. After load- source-pull simulations, proper source and load matching networks are established to obtain optimum output power and efficiency values over the band.
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    Cryogenic 1.2 to 116 GHz receiver for large arrays
    (IEEE, 2018) Weinreb, S.; Mani, H.; Zhong, W.; Flygare, J.; Billade, B.; Akgiray, Ahmed Halid; Dong, L.; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid
    Current and future large arrays for radio astronomy are compared and the Next Generation Very Large Array, ngVLA, is introduced. Receiver requirements are described and a 4-feed system covering 1.2 to 116 GHz, in a single vacuum cryogenic enclosure is presented followed by description of the reflector optics, the wide-band feeds, and the expected system performance
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    Design of compact monopulse standing wave slotted array in ku-band
    (IEEE, 2019) Akgiray, Ahmed Halid; Nawaz, Wasim; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid; Nawaz, Wasim
    In modern radar and communication systems, high gain, high power capability and low-profile front-end antenna systems are frequently utilized. In this paper, a compact, lightweight, high reflection bandwidth and high gain slotted wave guide array antenna with monopulse capability operating in Ku- band is presented. Target application of this antenna is radio links with built-in tracking capability on airborne platforms. The presented system is simulated using ANSYS HFSS and has two key components: monopulse comparator/feed network and antenna section. The antenna is designed at 15 GHz and it is a planar array of 4×8 radiating slots with a gain greater than 21 dB at 15 GHz, side-lobe level (SLL) ≤ -13 dB, reflection bandwidth of 1062 MHz. Monopulse comparator network is planar Magic Tee based waveguide structure. The complete integrated system has maximum dimension of 12cm x 7.2cm x 4cm that makes it easy to house on an aircraft.
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    An MMIC low-noise amplifier design technique
    (IEEE, 2016-03) Varonen, M.; Reeves, R.; Kangaslahti, P.; Samoska, L.; Kooi, J. W.; Cleary, K.; Gawande, R. S.; Akgiray, Ahmed Halid; Fung, A.; Gaier, T.; Weinreb, S.; Readhead, A. C. S.; Lawrence, C.; Sarkozy, S.; Lai, R.; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid
    In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26-33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K.
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    ArticlePublicationOpen Access
    A multioctave 8 GHz-40 GHz receiver for radio astronomy
    (IEEE, 2023-04) Kooi, J. W.; Soriano, M.; Bowen, j.; Abdulla, Z.; Samoska, L.; Fung, A. K.; Manthena, R.; Hoppe, D.; Javadi, H.; Crawford, T.; Hayton, D. J.; Malo-Gómez, I.; Gallego-Puyol, J. D.; Akgiray, Ahmed Halid; Gabritchidze, B.; Cleary, K. A.; Jacobs, C.; Lazio, J.; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid
    Accurate measurement of angular positions on the sky requires a well-defined system of reference, something that in practice is realized by the International Celestial Reference Frame (ICRF) with observations of distant (typical redshift similar to 1) Active Galactic Nuclei (AGN). At such great distances a subset of these objects exhibit as little as 10-50 mu as/year observed parallax or proper motion, thus giving the frame excellent spatial and temporal stability. Until fairly recently the majority of AGN centered imaging was accomplished in the S (2.3 GHz) and X (8.4 GHz) radio frequency bands, however S-band observations for reasons such as sensitivity "plateauing", increased source structure (jets), and radio frequency interference (RFI) have become less productive. Following spacecraft telemetry moves to higher frequencies and a desire to strengthen JPL's leadership in defining the next-generation of celestial reference frames has motivated the development of a "Quad-band" prototype receiver that operates in X, Ku, K, and Ka band in both right hand (RCP) and left hand (LCP) circular polarization. The goal of this receiver is to achieve less than a 20 % increase in noise over the Jansky Very Large Array (JVLA, NRAO) performance specification, which in such a wide bandwidth represents a revolutionary capability. To evaluate the various technical developments of the 8 GHz-40 GHz receiver the feedhorn optical beam was designed to interface to the US based Very Long Baseline Array (VLBA). The receiver's intermediate frequency (IF) spans 4 GHz-8 GHz, giving rise to up to eight 4 GHz IF channels for a fully populated instrument. This paper outlines the technical development of a 21/2 octave wide (8 GHz-40 GHz) X-Ka band prototype receiver, fulfilling a need for super broadband technology within the VLBI network. An important additional benefit of the wideband receiver approach is its simplicity and low cost of operation.
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    X- To Ka- Band cryogenic LNA module for very long baseline interferometry
    (IEEE, 2020) Fung, A.; Samoska, L.; Bowen, J.; Montanez, S.; Kooi, J.; Soriano, M.; Jacobs, C.; Manthena, R.; Hoppe, D.; Akgiray, Ahmed Halid; Lai, R.; Mei, X.; Barsky, M.; Electrical & Electronics Engineering; AKGİRAY, Ahmed Halid
    We report a new result of a packaged low noise amplifier (LNA) module with wide bandwidth of 5 to 35 GHz and low noise temperature performance of 10 -18 K, while operated at 10 K ambient. The LNA used 3-stages of sub-50 nm gate length, 100% indium channel content indium phosphide (InP) high electron mobility transistors (HEMTs). Wideband cryogenic LNAs are important for future radio astronomy observatories. To our knowledge these results represent the lowest noise achieved in a wideband amplifier from 5-35 GHz.