DESIGN AND ANALYSIS OF A MICROSTRIP PATCH ANTENNA AT 7.5 GHz FOR X-BAND VSAT APPLICATION

In this paper, a microstrip patch antenna is designed to be used for X-band VSAT application at 7.5 GHz. The antenna is proposed to replace the massive and commonly used parabolic reflector antennas (46.0 inch × 29.3 inch × 13.5 inch (116.84 cm × 74.42 cm × 34.29 cm) with weight of 66.2 kg) in terms of portability due to its compact and lightweight features, with overall dimensions of 19.00 mm × 30.55 mm. The 7.5 GHz frequency is chosen based on the X-band frequency used in Malaysia, as reported by STRIDE. The microstrip patch antenna is first designed and simulated using CST Microwave Studio (CST MWS) and exhibits a good return loss (S11) of -42.09 dB, a bandwidth of 399 MHz, directivity of 7.63 dB and gain of 7.18 dB. The antenna is then fabricated using RT/duroid ® High Frequency 5880 substrate with a dielectric constant of ?r = 2.2, loss tangent of ? = 0.0009 and thickness of t = 1.574 mm. Next, the return loss and radiation pattern measurements are carried out to confirm the simulated results. The measurement of the antenna prototype provides a return loss S11 of -30.53 dB, bandwidth of 455 MHz, directivity of 5.51 dB and gain of 3.88 dB. ABSTRAK: Di dalam kajian ini, antena jalurmikro dicadangkan untuk tujuan aplikasi jalur-X VSAT pada 7.5 GHz. Antena jalurmikro ini dicadangkan untuk menggantikan antena reflektor parabola yang besar dan biasa digunakan (46.0 inci × 29.3 inci × 13.5 inci (116.84cm × 74.42cm × 34.29cm) dengan berat 66.2kg), kerana cirinya yang mudah alih dengan fizikalnya yang kecil dan ringan, dan dimensi keseluruhan 19.00 mm × 30.55 mm. Frekuensi 7.5 GHz dipilih berdasarkan frekuensi jalur-X yang digunakan di Malaysia, seperti yang dilaporkan oleh STRIDE. Antena jalurmikro ini direka dan disimulasi menggunakan perisian CST Studio Gelombang Mikro (CST MWS) dan menghasilkan kehilangan pulangan yang baik S11 -42.09 dB, lebar jalur 399 MHz, keterarahan 7.63 dB dan gandaan 7.18 dB. Antena jalurmikro ini kemudiannya direalisasikan dengan menggunakan substrat RT / duroid ® Frekuensi Tinggi 5880 dengan pemalar dielektrik ?r = 2.2, tangen kehilangan ? = 0.0009 dan ketebalan t = 1.574 mm. Seterusnya, pengukuran kehilangan pulangan dan corak radiasi dilakukan untuk mengesahkan keputusan simulasi. Pengukuran prototaip antena jalurmikro menunjukkan kehilangan pulangan S11 -30.53 dB, lebar jalur 455 MHz, keterarahan 5.51 dB dan gandaan 3.88 dB.

Methods of Electrodynamic Modelling for Reflector Antennas

The article discusses methods for calculating the electromagnetic characteristics of reflector antennas based on the finite integration method, the method of moments, and the hybrid method. In the course of the study, a performance comparison of these methods in the process of calculating the reflector antenna characteristics was made. Comparison of the calculation efficiency was carried out using four computing devices. On the basis of the calculations, the graphs of the scattering matrix and the directional diagrams of the antenna under study were obtained

Cross-Pol Pattern Effects of Parabolic Reflector Antennas on the Performance of Spaceborne Quad-Pol SAR Systems

The ambiguity performance related to the image quality of a synthetic aperture radar (SAR) system can be categorized into range ambiguity, azimuth ambiguity, and cross ambiguity depending on the cause of the ambiguity signals. The ambiguity performance is affected by the operational method and antenna radiation patterns of an SAR system. In this paper, the effect of the antenna cross-polarization (cross-pol) pattern on the ambiguity performance of a spaceborne quadrature polarimetric (quad-pol) SAR system using an X-band reflector antenna was analyzed. Two methods, conventional quad-pol SAR and hybrid quad-pol SAR systems, have been proposed as quad-pol SAR operational concepts for system performance analysis. We proposed a process to effectively analyze the effect of the antenna cross-pol pattern and showed this through a comparison of several analysis methods. In addition, the difference in antenna radiation patterns according to the size and structure of reflector antennas was compared, and the effects were described in detail. In conclusion, the larger the antenna and the more complex the structure, the greater the effect of the antenna cross-pol pattern, leading to a similar phenomenon as the two quad-pol SAR systems.