1420 MHZ RADYO TELESKOP UYGULAMALARI İÇİN MİKROŞERİT BASAMAK EMPEDANS REZONATÖRLÜ BANT GEÇİREN FİLTRE TASARIMI

Radyo teleskoplar, gökbilimcilere, görsel veya optik bölgenin çok ötesine uzanan erişilebilir elektromanyetik spektrumun tamamında gözlem yapma imkânı sunarlar. Her frekans aralığı kendi içgörülerini sağlar ve genellikle kendi teleskop ve dedektör çeşitlerini gerektirir. Radyo astronomlar, 13 MHz ile 2000 GHz aralığında frekanslarda enerji yayan veya emen nesneleri incelerler ve atmosferin şeffaf olduğu her frekans değerinde çalışmalar yapılır. 1420 MHz radyo astronomik ölçümlerin yapıldığı frekans değerlerinden birisidir. Yaklaşık 1420 MHz'de 21 cm'lik bir dalga boyuna sahip olan nötr hidrojen (HI) emisyonları, galaksideki uzak yerlerden ve yönlerden kaynaklanır, yıldızlararası bulutlardan geçer ve Doppler kaydırılmış frekanslarda yer tabanlı radyo teleskop gözlemlerinde ortaya çıkar. HI emisyonlarından yapılan haritalar, Samanyolu Galaksisi’nin sarmal yapısını ortaya çıkarır. Ölçümler radyo teleskop sistemlerinin RF bloğu ile gerçekleştirilir. Bant geçiren filtreler bu RF bloğun çok önemli bileşenlerindendir. Bu çalışmada 1420 MHz radyo teleskop uygulamaları için Basamak Empedans Rezonatör yapısı kullanılarak mikroşerit bant geçiren filtre tasarımı yapılmıştır. Tasarımda basamak empedans rezonatörü ile paralel kuplajlı hat yapısı beraber kullanılmıştır. Filtre Keysight ADS simülatörü ile tasarlanmış ve istenen tasarım kriterlerine ulaşmak için paralel kuplajlı hat uzunlukları optimize edilmiştir. Yapılan simülasyonlar neticesinde tasarlanan filtrenin 3dB bant genişliği 130 MHz, ekleme kaybı (S_{21}) -0.152 dB, giriş yansıma katsayısı (S_{11}) -38.018 dB olarak bulunmuştur. Çalışmada tasarlanan filtre 1420 MHZ radyo teleskoplarının RF alıcı bloğunda kullanılacak kriterlere sahiptir. Ayrıca filtre eğitim ve deney amaçlı radyo teleskop sistemlerinde kullanılabilecektir.

Anahtar Kelimeler:

Radyo Teleskop, 1420 MHz Nötr Hidrojen (HI) Emisyonu, Mikroşerit Bant Geçiren Filtre, Basamak Empedans Rezonatör.

SIR MICROSTRIP BAND-PASS FILTER DESIGN FOR 1420 MHZ RADIO TELESCOPE APPLICATIONS

Radio telescopes allow astronomers to observe across the entire accessible electromagnetic spectrum that extends far beyond the visual or "optical" region. Each frequency range provides its own insights and often requires its own variety of telescopes and detectors. Radio astronomers research objects which emit or absorb energy from 13 MHz to 2000 GHz and studies are carried out at every frequency where the atmosphere is transparent. 1420 MHz is one of the frequency values where radio astronomical measurements are carried out. Neutral hydrogen (HI) emissions, with a wavelength of 21 cm at about 1420 MHz, originate from distant places and directions in the galaxy, pass through interstellar clouds and occur in ground-based radio telescope observations at Doppler shifted frequencies. Maps made from HI emissions reveal the spiral structure of the Milky Way Galaxy. Measurements are carried out with the RF block of radio telescope systems. Bandpass filters are one of the most important components of this RF block. In this study, a microstrip bandpass filter was designed for 1420 MHz radio telescopes using the Stepped Impedance Resonator (SIR). In the design, parallel coupled lines are used together with the stepped impedance resonator. The filter was designed with the Keysight ADS and lengths of parallel coupled lines were optimized to achieve the desired design criteria. As a result of the simulations, the 3dB bandwidth of the designed filter was found to be 130 MHz, the insertion loss (S_{21}) was -0.152 dB, and the input reflection coefficient (S_{11}) was -38.018 dB. The designed filter has the criteria to be used in the RF receiver block of 1420 MHz radio telescopes. The filter designed in the study can be used in radio telescope systems for educational and experimental purposes

Keywords:

Radio Telescope, 1420 MHz Neutral Hydrogen (HI) Emission, Microstrip Bandpass Filter,

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