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![Polyrod antenna dimensions given in [21]](profile/Volkan-Akan/publication/346503987/figure/tbl1/AS:963883858677763@1606819228537/Polyrod-antenna-dimensions-given-in-21_Q320.jpg)
In satellite communication, link margin and therefore antenna radiation characteristics are key factors to ensure providing a robust communication link between space and ground segment. For telemetry/telecommand and payload data transfer, isoflux antennas are employed widely in satellite communication systems to direct electromagnetic wave efficien...
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... simple geometrical calculation can be given to define change of range with respect to the elevation angle of a satellite. As shown in Figure 1, slant range relation between satellite and ground station can be evaluated using earth radius R (equals to about 6378km), satellite altitude h, antenna elevation angle θ, and satellite elevation angle with respect to horizon α. ...
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... is evident that once beamwidth widens then the maximum directivity decreases as expected. In Figure 10, the variation of axial ratio with respect to θ at ϕ=0 0 cut is seen. Particularly, for θ values where maximum directivity is obtained, axial ratio values are lower than 1.5dB. ...
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... 9. Directivity of the designed antenna at ϕ=0 0 cut plane. Figure 10. Axial ratio of the designed antenna at ϕ=0 0 cut plane Besides, 3-D radiation pattern for directivity is seen in Figure 11. ...
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... 10. Axial ratio of the designed antenna at ϕ=0 0 cut plane Besides, 3-D radiation pattern for directivity is seen in Figure 11. According to this figure conical shaped beam is obvious. ...
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... to this figure conical shaped beam is obvious. The return loss of the antenna has also been obtained by the simulation and it is given in Figure 12. This result demonstrates 10dB return loss bandwidth of the antenna is at a good value range for the defined frequency band of 7-7.5GHz. ...
Citations
... There are many studies for antennas that have isoflux radiation characteristics in the literature [8][9][10][11][12][13][14][15]. Volkan Akan presented a polyrod antenna that has an isoflux radiation characteristic for satellite communication systems in [8]. ...
... There are many studies for antennas that have isoflux radiation characteristics in the literature [8][9][10][11][12][13][14][15]. Volkan Akan presented a polyrod antenna that has an isoflux radiation characteristic for satellite communication systems in [8]. In this study, the polyrod antenna was a single antenna with fixed isoflux coverage. ...
In this paper, we propose an innovative spaceborne isoflux scanning digital phased array (ISDPA) design with two-stage digital beamforming (DBF) for geostationary satellites. To achieve isoflux scanning, a novel technique is presented to obtain an isoflux beam for the ISDPA equivalent element using a DBF completely shared subarray architecture and the differential evolution (DE) algorithm. By reutilizing the radiating elements of adjacent subarrays, the radiation aperture and element number are augmented, enhancing the degrees of optimization freedom. To validate the proposed design, a linear ISDPA with 16 DBF completely shared subarrays is optimized and analyzed using two sets of excitation coefficients in different DBF stages. The numerical results demonstrate that the proposed ISDPA can adaptively compensate for space loss variations during beam scanning for geostationary communications with low sidelobes better than −20 dB.
... These are generally earth observation, non-optical remote sensing, meteorological missions for weather forecast, scientific and research missions, data broadcasting and, also Internet of Things (IoT). [1][2][3][4][5][6][7][8][9][10][11][12][13] Furthermore, to perform different duties on the satellite there are different types of communication systems. Those are telemetry/telecommand (TM/TC), payload data transmitter (PDT), inter satellite link (ISL) communication subsystems, etc. as highlighted in Reference 11. ...
In low earth orbiting satellite communication systems, antennas are key elements for radio frequency transmitters and receivers. There are different types of antennas used on satellite communication systems. One of them is the antenna used in payload data transfer communication subsystem. Payload data transmitters for space segment should utilize the radio frequency power efficiently due to the limited power budget of the spacecraft. For low elevation angles of a low earth orbiting satellite, the free space loss increases as expected and it should be compensated. One way of this compensation is to employ an antenna having isoflux pattern. Therefore, in this paper, a circularly polarized X‐Band choked ring horn antenna is designed, optimized and manufactured due to its isoflux radiation characteristic and medium power handling capability. Initially, an analytical approach from the literature is explained and then the physical dimensions of the proposed antenna are optimized, iteratively, employing a commercially available electromagnetic solver. Next, a prototype has been manufactured to verify the radiation, return loss and port isolation characteristics and they are presented in the related section. Moreover, the results of the presented antenna have been compared to the ones available in the literature. These comparisons show that gain of the designed antenna at ±64° elevation angle has higher gain with respect to the compared ones. In addition, its axial ratio value is smaller than 6.5 dB for different azimuth angles between 8025 and 8400 MHz. Unlike the other studies given in the literature that have gain higher than 2 dB at ±64° elevation angle, in this study all design parameters have been presented to utilize through the operating bandwidth.
... Bu görevler optik ya da mikrodalga enstrümanlarla yer gözlem, bilimsel araştırma, veri haberleşmesi, IoT için internet yayını sağlama vb. olarak sayılabilir (Akan ve Yazgan, 2010;Imbriale, 2012;Akan ve Dudak, 2014;Akan, 2015;Akan ve ark., 2017;Akan, 2020;Akan ve Yazgan, 2020). Bunun yanında yer sabit uydularda da haberleşme alt sistem ve donanımları oldukça önemli bir yere sahiptir. ...
Dalga kılavuzlarının kullanılma fikri ve ilk tasarımları on dokuzuncu yüzyılın ikinci yarısına kadar uzanmaktadır. Ayrıca İkinci Dünya Savaşı’nda özellikle radar teknolojisinin temellerinin atılmasıyla dalga kılavuzları ve bu iletim hatları üzerinde tasarlanarak üretilen RF/Mikrodalga bileşenler kablosuz haberleşme teknolojilerinin vazgeçilmez yapılarından birisi olmuştur. Günümüzde de özellikle yüksek güç ihtiyacı olan RF/Mikrodalga sistemlerde sıklıkla görev almaktadırlar. Ayrıca dairesel kutuplanmalı açıklık antenler ve bu antenlerin besleme bileşenleri özellikle uydu haberleşmesinde önemli bir yer teşkil etmektedir. Mobil haberleşme sistemlerinde kutuplanma kaybının azaltılması, veri hızının artırılması için kutuplanma çeşitliğinin kullanılması vb. uygulamalarda bu yapılara ihtiyaç duyulmaktadır. Özellikle dalga kılavuzu ile beslenen antenlerin dairesel kutuplanmalı elektromanyetik dalga yayması ya da alması için kutuplaştırıcı yapıları kullanılmaktadır. Bu yapılar antenin çevresine yerleştirilen özellikte olabileceği gibi anten girişinde ve dalga kılavuzu içinde de olabilmektedir. Bunlardan birisi de septum kutuplaştırıcıdır. Septum yapısı dalga kılavuzunun içinde yer aldığı için dış etkilere daha az maruz kalmakta ayrıca az hacimli ve hafifliği dolayısıyla da kullanım ve uygulama kolaylığı sağlamaktadır. Bu çalışmada hem uzay kesimi hem de yer kesimi S-Bant uydu haberleşme sistemlerinde dairesel kutuplanmalı anten beslemelerinde kullanılmak üzere dört adımlı septum kutuplaştırıcının analiz ve tasarımı gerçekleştirilerek ticari bir elektromanyetik çözümleyicide benzetimleri yapılmıştır. Belirlenen yalıtım hedefleri doğrultusunda tasarım geri dönüş kaybı, port yalıtımı ve eksenel oran değerleri bakımından iyileştirilmiştir. Elde edilen sonuçlar da belirtilen geri dönüş kaybı, port yalıtımı, eksenel oran ve ışıma örüntüsü olarak sunulmuştur. Bu sonuçlara göre tasarımı gerçekleştirilen dört adımlı septum kutuplaştırıcı yapısı özellikle S-Bant uydu haberleşme sistemlerinde dairesel kutuplanma elde etmek için anten girişlerinde kullanılabilir.
In this letter, we propose a novel spaceborne isoflux scanning phased array (ISPA) antenna at Ka-band for geostationary earth orbit (GEO) satellite communications. The ISPA can adaptively compensate for space loss variation during beam scanning. An innovative method for achieving the isoflux scanning characteristics of ISPA by using shared subarrays with an isoflux beam as equivalent elements has been proposed and verified. Taking the space loss variation law derived from the satellite-ground model as the isoflux beam optimization goal, the challenge associated with subarray beam shaping is mitigated greatly by utilizing a shared subarray architecture with a sharing ratio of 4:1, enhancing the subarray's radiation aperture and element number substantially. The optimization results of the shared subarray by using a weighted alternating reverse projection method are verified in full-wave simulation in ANSYS Electronics Desktop. Numerical results further demonstrate that the proposed ISPA can adaptively compensate for the inconsistency in satellite communication link variation during beam scanning and exhibits low sidelobes better than -20dB while effectively suppressing grating lobes.
