Development of triangular array eight patches antennas for circularly-polarized synthetic aperture radar sensor

In this paper, we obtain the left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) of triangular array eight patches antennas using corporate feeding-line for circularly polarized-synthetic aperture radar (CP-SAR) sensor embedded on unmanned aerial vehicle (UAV) with compact, simple, and efficient configuration. Although the corporate feeding-line design has already been developed, its design was for the side antenna view of 0° and only produced one of LHCP or RHCP instead of both. Here, the design for LHCP and RHCP eight patches array fed by corporate feeding-line having the side antenna view of 36° at f=1.25 GHz for CP-SAR are discussed. We use the 2016 version of computer simulation technology (CST) to realize the method of moments (MoM) for analyzing. The performance results, especially for gain and axial ratio (Ar) at resonant frequency are consecutively 13.46 dBic and 1.99 dB both of LHCP and RHCP. Moreover, the 12-dBic gain-bandwidth and the 3-dB Ar-bandwidth of them are consecutively around 38 MHz (3.04%) and 6 MHz (0.48%). Furthermore, the two-beams appeared at boresight in elevation plane for average beamwidth of 12 dBic-gain and the 3 dB-Ar LHCP and RHCP have similar values of around 12° and 46°, respectively

ESTIMATION OF DATA MEMORY CAPACITY FOR CIRCULARLY POLARIZED SYNTHETIC APERTURE RADAR ONBOARD UNMANNED AERIAL VEHICLE PLATFORM (CP-SAR UAV)

Previously only linear polarization is widely used in the Synthetic Aperture Radar(SAR) system onboard spaceborne and airborne platforms. In such linearly polarized SAR(LP-SAR) systems, Faraday rotation in the ionosphere and platform posture will contribute tothe system noise. Therefore to improve this situation, currently a novel Circularly PolarizedSynthetic Aperture Radar (CP-SAR) sensor is developed in Microwave Remote SensingLaboratory, Chiba University. Moreover, from this research, a new backscattering data basedon circularly polarized wave in the remote sensing field can be obtained. As an early stage ofthe development of this CP-SAR sensor, we built an Unmanned Aerial Vehicle (UAV)platform for testing CP-SAR sensor capabilities. In this paper, we describe the novel CP-SARsensor and the method to design CP-SAR UAV especially in estimating the requirement ofdata memory capacity. Also a smaller antenna is possible to be implemented since the 3-dBaxial ratio on antenna characteristic becomes the main parameter in this new CP-SARtechnique. Hence, a compact CP-SAR sensor onboard a small and low cost spaceborneplatform yielding a high accuracy SAR image data can be realized in the near future

ANTENA HELIX MODE AXIAL UNTUK SENSOR CIRCULARLY POLARIZED SYNTHETIC APERTURE RADAR (CP-SAR) PADA PESAWAT TANPA AWAK

Synthetic Aperture Radar (SAR) merupakan salah satu bentuk perkembangan teknologi radar yang digunakan untuk membuat gambar dua atau tiga dimensi suatu objek. SAR menggunakan sensor berupa antena yang polarisasi gelombang yang dipancarkan berbentuk sirkular atau bisa disebut dengan Circularly Polarized Synthetic Aperture Radar (CP-SAR). CP-SAR dapat meminimalisir pergeseran fasa ketika gelombang melewati lapisan ionosfer, sehingga meningkatkan kualitas data citra yang dihasikan. Sistem CP-SAR akan digunakan pada Unmanned Aerial Vehicle (UAV) JX-1 sebagai ground testing. Pada penelitian ini dirancang antena helix untuk sistem CP-SAR pada UAV dengan menggunakan mode axial untuk menghasilkan polaradiasi unidirectional, Right Hand Circular Polarized (RHCP) terhadap sumbu catuan. Teknik pencatuan yang digunakan teknik pheriperal. Untuk teknik matching impedance mengunakan penambahan ¼ lilitan. Proses desain dan simulasi menggunakan software simulator antena. Proses realisasi menggunakan kabel tembaga dengan nilai konduktivas 5,7 x 107 mho/m. dan memiliki ketebalan 4 mm. Antena helix mode axial menghasilkan gain 9,61 dB , axial ratio 1,03 dB, VSWR 1,46 , return loss -14,97 dB, pola radiasi unidirectional dan bandwidth 568 MHz. Di desain 4 lilitan dengan total panjang antena adalah 29 cm dan memiliki berat 1,5 kg. Kata Kunci: Antena Helix, Polarisasi Sirkular, CP-SAR, RHC

LHCP four patches stack triangular truncated antenna using corporate feed microstrip-line for CP-SAR sensor

In this paper, we acquire the configuration of the left-hand circular polarization (LHCP) array four patches stack triangular truncated microstrip antenna. This construction use the basic corporate feed microstrip-line with modified lossless T-junction power divider on radiating patch for circularly polarized-synthetic aperture radar (CP-SAR) sensor embedded on unmanned aerial vehicle (UAV) with compact, small, and simple configuration. The design of circular polarization (CP) is realized by truncating the whole three tips and adjusting the parameters of antenna at the target frequency, f = 5.2 GHz. The results of characteristic performance and S-parameter for the LHCP array four patches stack antenna at the target frequency show successively about 9.74 dBic of gain, 2.89 dB of axial ratio (Ar), and -10.91 dB of S-parameter. Moreover, the impedance bandwidth and the 3 dB-Ar bandwidth of this antenna are around 410 MHz (7.89%) and 100 MHz (1.92%), respectively

PERBANDINGAN ANTENA MIKROSTRIP PATCH LINGKARAN DAN PERSEGI POLARISASI SIRKULAR UNTUK SYNTHETIC APERTURE RADAR FREKUENSI 1.27 GHZ

Hingga saat ini, beberapa sensor SAR yang telah mengudara merupakan sistem polarisasi linier pada antena. Secara umum polarisasi linier sangat sensitif terhadap rotasi Faraday di ionosfer yang disebabkan interaksi antara gelombang elektromagnetik yang merambat dan medan magnet bumi. Untuk mengatasi hal tersebut dapat diterapkan CP-SAR (Circularly Polarization-Synthetic Aperture Radar). Tujuan utama dari sensor ini adalah untuk mengurangi efek rotasi Faraday ketika radiasi gelombang elektromagnetik merambat melalui ionosfer. Untuk mengatasi hal tersebut dibuatlah antena spesifikasi frekunsi 1.27 GHz, impedansi 50 ohm, vswr ?1.5, pola radiasi unidirectional, polarisasi sirkular putar kanan (RHCP), axial ratio kurang dari 3 dB dengan bahan substrat FR-4 Epoxy memiliki konstanta dielektrik 4.3, dan teknik catuan proximity coupled microstrip feed. Pada penelitian kali ini dibandingkan dua buah bentuk patch yaitu lingkaran dan persegi. Lalu dipilih salah satu dengan performansi paling baik dan memenuhi spesifikasi yang dibutuhkan. Kemudian didapatkan hasil antena dengan bentuk patch lingkaran memiliki performansi paling baik dan memenuhi spesifikasi yang dibutuhkan. Antena patch lingkaran memiliki bandwidth 27 MHz, polaradiasi unidirectional, axial ratio ?3 dB serta polarisasi sirkular putar kanan

China’s Antiship Ballistic Missile—Developments and Missing Links

That China is interested in an antiship ballistic missile seems a logical and natural outgrowth of its history of robust missile development. At what stage is its development? How near to operational readiness are its key components and technologies? What would be its implications for the U.S. Navy and the naval strategic balance between the United States and China

Design Options For Low Cost, Low Power Microsatellite Based SAR.

This research aims at providing a system design that reduces the mass and cost of spaceborne Synthetic Aperture Radar (SAR) missions by a factor of two compared to current (TecSAR - 300 kg, ~ £ 127 M) or planned (NovaSAR-S — 400 kg, ~ £ 50 M) mission. This would enable the cost of a SAR constellation to approach that of the current optical constellation such as Disaster Monitoring Constellation (DMC). This research has identified that the mission cost can be reduced significantly by: focusing on a narrow range of applications (forestry and disasters monitoring); ensuring the final design has a compact stowage volume, which facilitates a shared launch; and building the payload around available platforms, rather than the platform around the payload. The central idea of the research has been to operate the SAR at a low instantaneous power level—a practical proposition for a micro-satellite based SAR. The use of a simple parabolic reflector with a single horn at L-band means that a single, reliable and efficient Solid State Power Amplifier (SSPA) can be used to lower the overall system cost, and to minimise the impact on the spacecraft power system. A detailed analysis of basic pulsed (~ 5 - 10 % duty cycle) and Continuous Wave (CW) SAR (100 % duty cycle) payloads has shown their inability to fit directly into existing microsatellite buses without involving major changes, or employing more than one platform. To circumvent the problems of pulsed and CW techniques, two approaches have been formulated. The first shows that a CW SAR can be implemented in a mono-static way with a single antenna on a single platform. In this technique, the SAR works in an Interrupted CW (ICW) mode, but these interruptions introduce periodic gaps in the raw data. On processing, these gapped data result in artefacts in the reconstructed images. By applying data based statistical estimation techniques to “fill in the gaps” in the simulated raw SAR data, this research has shown the possibility of minimising the effects of these artefacts. However, once the same techniques are applied to the real SAR data (in this case derived from RADARSAT-1), the artefacts are shown to be problematic. Because of this the ICW SAR design technique it is—set aside. The second shows that an extended chirp mode pulsed (ECMP) SAR (~ 20 - 54 % duty cycle) can be designed with a lowered peak power level which enables a single SSPA to feed a parabolic Cassegrain antenna. The detailed analysis shows the feasibility of developing a microsatellite based SAR design at a comparable price to those of optical missions

Commercial Space

This chapter assesses trends and developments in the commercial space sector, which includes manufacturers of space hardware such as rockets and satellite components, providers of space-based information such as telecommunications and remote sensing, and service operators for space launches. Also covered in this chapter are the developments related to the nascent space tourism industry, as well as the relationship between commercial operators and the public sector

Space Security 2008

Provides data and analysis on space activities in 2007 and their cumulative impact on security issues, including space laws, policies, and doctrines; civil space programs and global utilities; commercial uses; and environmental and military issues