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    Antipodal Vivaldi Antenna for Passive Imaging Technology in Ka Frequency Band
    (2018) Duman, Mehmet; Salman, Alp Oral
    Antenna is one of the most important part in Passive Millimeterwave Imaging (PMI) Technology which isused to view scene in foggy air conditions or to see concealed weapon under clothes that cannot be seenother technology because of the materials of weapon. There are some frequency windows to work withPMI Technology as 35, 96 and 220 GHz and it is near 35 GHz frequency window for this work. AntipodalVivaldi Antenna has 50.07 ohm input impedance, Z, for matching, and -39.23 dB input reflectioncoefficient, S11, and 6.82 dB gain, G, is designed for 35.18 GHz center frequency in Computer SimulationTechnology (CST) Program. The antenna has 110 MHz bandwidth and it can work between 35.23 GHz and35.12 GHz frequencies. After the antenna is connected to the amplifier or detector circuits, the createdsystem will be integrated into a scanner which is capable of scanning azimuth and elevation axes. As aresult, PMI System will be formed and ready to view the scene or the hidden things in haze air conditions.
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    High-resolution 96-GHz (3 mm) passive millimeter-wave imaging system and the effect of scanning resolution on images
    (Spie-Soc Photo-Optical Instrumentation Engineers, 2022) Salman, Alp Oral; Duman, Mehmet
    A high-resolution 96-GHz (3 mm) passive millimeter-wave imaging system is constructed. The system has a 96-GHz radiometric receiver, which is placed on the focal point of a 50-cm diameter parabolic reflector designed and created. A specially written program for the system controls the antenna via control hardware in desired steps by a 2-axis positioner motor. A balance weight has been calculated and mounted to the rear of this parabolic reflector antenna to prevent possible damage to the rotor of the positioner motor due to the antenna's weight. The maximum field of view of the system is 120 deg in azimuth and 90 deg in elevation. The angular scan step can be varied from 0.1 deg to 1 deg. Although the system can shoot 1190 x 890 samples (pixels) images, which is close to the HD quality (1280 x 720 pixels) in the full field of view, the actual resolution of the image is limited by the antenna's beamwidth (BW). Some measurements were performed to investigate the effect of scanning steps on PMMW image quality for different angular scan steps. It is observed that the PMMW image scan with the smallest step gives a detailed image that is the closest to the scene's optical image as expected. Even though the angular scan step angle is less than half of the antenna's BWat Nyquist sampling, it is observed that the image quality still improves due to averaging effect of the received signals giving a better estimated S/N. The resolution and scan step values of our system are compared with that of some systems found in the literature and it is shown that ours has the highest value among them. This system can be used to obtain high-resolution images in remote sensing and other applications. (c) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    LNA Design and Implementation for Passive Millimeter Wave Imaging System in Ka Band
    (Wydawnictwo Sigma-Not Sp Zoo, 2022) Duman, Mehmet; Salman, Alp Oral
    There are several methods of creating a Passive Millimeter Wave Imaging System (PMMWIS). One of these methods is to use tripod, 2-axis positioner, control unit, the parabolic reflector antenna (PRA) and the radiometric receiver located at the focal point of the PRA. The radiometric receiver, which is the most important part of the system can be divided into parts such as low noise amplifier (LNA), detector, mixer and video amplifier (VA). In this study; LNA will be explained. PMMWIS is an imaging method that emerged as a result of the weakening of the radiation in other systems due to atmospheric effects. In case of working in certain frequency windows (35 GHz, 96 GHz, 220 GHz, ...); the radiation will not be affected by weather events and can be measured. In this study, an LNA has been created for a radiometric receiver that can be operated at Ka-band. Hittite brand HMC1040LP3CE chip from Analog Devices Company, which can theoretically give 23 dB gain in Ka-band has been preferred. The discrete elements and the chip in the circuit are very precisely placed on the board with special solder mixtures using electronic magnifiers, and 2.92 mm connectors are included in the input and output (IO) of the RF line of the circuit. In the last case; the LNA circuit, which was prepared for measurement, was fed with the power supply. It was measured with the help of vector network analyzer (VNA). At last, the LNA working in the Ka-band produced for PMMWIS with a gain value of 19.32 dB at 26.2 GHz center frequency was obtained.
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    Pasif Milimetre Dalga Görüntüleme Sistemi için Radyometrik Alıcının Parabolik Yansıtıcı Antendeki Doğru Konumunun Belirlenmesi
    (2020) Salman, Alp Oral; Duman, Mehmet
    Savunma ve navigasyon gibi alanlarda, optik ve kızılötesi görüntüleme sistemlerinin sağlıklı çalışamadığı sis,yağmur ve toz gibi görüşü engelleyen çeşitli hava olaylarında, ortamı görüntülemek için, tamamlayıcı sensörolarak Pasif MiliMetre Dalga Görüntüleme Sistemi (PMMDGS) kullanılabilir. Sistem; radyometrik a lıcınınparabolik yansıtıcı anteninin odak noktasında bulunduğu ve bu antenin iki eksende (azimut ve kalkış) çalışan birkonumlandırıcı tarafından taranmasıyla görüntülemenin yapıldığı bir teknolojiye sahiptir. Bir PMMDGS’degörüntülenen ortamdan gelen sinyalin oldukça zayıf olmasından dolayı hem iyi bir kuvvetlendirmenin yapılmasıhem de alıcıdan optimal sinyalin elde edilebilmesi için radyometrik alıcının parabolik yansıtıcı antenin odaknoktasına doğru konumunda yerleştirilmesi büyük bir önem arz etmektedir. Bu çalışmada; PMMDGS’nin anteni,gökyüzü gibi sabit bir görüntüleme noktasına yönlendirilmiş iken radyometrik alıcı, parabolik yansıtıcı antendenbelli mesafelerde kaydırılmış ve optimal sinyalin elde edildiği konum bulunmuştur. Sonuçlar, algılamanınradyometrik alıcıya bağlı olan horn antenin açıklık ucundan değil, bağlantı kısmına yakın bir noktadan olduğunugöstermiştir.
  • Küçük Resim Yok
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    Providing the Moment of the Parabolic Reflector Antenna in the Passive Millimeter Wave Imaging System with the Equilibrium Weights
    (Springer International Publishing Ag, 2020) Duman, Mehmet; Salman, Alp Oral
    In foggy, cloudy and rainy weather; for the purpose of radiometric imaging; Passive MilliMeter Wave Imaging System (PMMWIS) was installed with a radiometric receiver operating at a frequency of 96 GHz which is one of the specific frequency windows for passive detection. After the installation of this system, while working, there were contractions in the motor part of the 2-axis positioner with which the parabolic reflector antenna of the PMMWIS. These contractions were mainly during upward system calibration or during normal scan of the system. Therefore, it had become necessary to make balance weights for more convenient operation. In this study; the equilibrium weights were integrated in order to synchronize the moment to the opposite direction of the parabolic reflector antenna. According to the weight and height of the parabolic reflector antenna to be mounted on the system, four different balance weights could be used. The sounds from the gears in the engine of the 2-axis positioner, indicating that the motor was contracted for every degree to be scanned (it could be 0.1 degrees to the resolution) was indicative of the deterioration of the gears in the 2-axis positioner. Consequently; the balance weights were produced and integrated into the system. As a result; the torque of the antenna was achieved and the 2-axis positioner was able to scan the view by means of PMMWIS without any contraction in the azimuth and elevation axes.
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    Theoretical Investigation of Blackbody Radiation for the Passive Millimeterwave Imaging System
    (Ieee, 2018) Duman, Mehmet; Salman, Alp Oral
    In a passive millimeter wave imaging (PMMWI), there is no outgoing wave from the antenna of PMMWI system unlike the RAdio Detection And Ranging (RADAR). Antenna is only used to measure incoming waves which are coming from the all things because of being more than 0 Kelvin temperature or being non-blackbody. Radiation of the wall and the glass are different in a building; as a result, the PMMWI system can image the building with a good resolution to distinct the wall and glass. It can also image the gun that is under the cloth thanks to radiation difference. These systems utilize Planck, Wien and Rayleigh-Jeans Theories to view the images which are scanned in azimuth and elevation axis by PMMWI system through its antenna. In this work, the Planck, Wien and Rayleigh-Jeans Theories are analyzed and their formulas are run on MatLab Program with different temperatures for frequency or wave length at x-axis and for spectral radiance at y-axis.