Hierarchical Classification Method for Radio Frequency Interference Recognition and Characterization in Satcom

The Quality of Service (QoS) and security of Satellite Communication (Satcom) are crucial as Satcom plays a significant role in a wide range of applications, such as direct broadcast satellite, earth observation, navigation, and government/military systems. Therefore, it is necessary to ensure that transmissions are incorruptible, particularly in the presence of challenges such as Radio Frequency Interference (RFI), which is of primary concern for the efficiency of communications. The security of a wireless communication system can be improved using a robust RFI detection method, which could, in turn, lead to an effective mitigation process. This paper presents a new method to recognize received signal characteristics using a hierarchical classification in a multi-layer perceptron (MLP) neural network. The considered characteristics are signal modulation and the type of RFI. In the experiments, a real-time video stream transmitted in the direct broadcast satellite is utilized with four modulation types, namely, QPSK, 8APSK, 16APSK, and 32APSK. Moreover, it is assumed that the communication signal can be combined with one of the three significant types of interference, namely, Continuous Wave Interference (CWI), Multiple CWI (MCWI), and Chirp Interference (CI). In addition, two robust feature selection techniques have been developed to select more informative features, which leads to improving the classification precision. Furthermore, the robustness of the trained techniques is assessed to predict unknown signals at different Signal to Noise Ratios (SNRs).

Design of a compact high gain printed octagonal array of spiral-based fractal antennas for DBS application

This paper presents a compact octagonal array of microstrip patch antennas for direct broadcast satellite (DBS) (12.2–12.7 GHz) services. The proposed single element of this array is a new fractal antenna, having considerably high gain and can heavily suppress cross polarization along the main beam direction. The single element is derived from a 2D spiral geometry. The corporate feed network of the array is designed in such a manner to make the structure very compact. The fabricated single element resonates at 12.51 GHz and gives a gain and bandwidth of 9.32 dBi and 280 MHz, respectively. The array resonates at 12.46 GHz and gives gain of 17.67 dBi and a bandwidth of 506 MHz, which ensures a 100% coverage of the entire DBS service band. The measured cross polarization of single element and array along the direction of main beam are −45.50 and −43.35 dB, respectively. Both the single element as well as the array maintains a reasonably good radiation efficiency of 86.70 and 82.20%, respectively.

Multi-Beam Circular Polarized Reflectarray on Parabolic Reflector by Variable Rotation Technique

Multi-beams antennas are currently being used for direct broadcast satellite, personal communication satellite, military communication satellite, and high-speed internet applications. In this work, a circularly polarized (CP) multi-spot beam satellite parabolic reflectarray antenna is designed to provide six spot beams at 19.7 GHz. For this purpose, an easy technique to compute the required phase shifts to produce two focused beams in specular directions for a CP parabolic reflectarray is proposed. These required phase shifts are added to the reflected fields by the variable rotation of the reflectarray elements printed on the surface of a parabolic antenna which are fed by a dual-CP feed-horn. For this purpose, a reflectarray cell made of a conductive cross embedded in a grounded multilayered substrate is optimized to produce very linear phase-shift and low cross-polarization level. To demonstrate the multibeam capacity, a 1.8-meter offset parabolic reflectarray made of the optimized reflectarray element was designed to generate six focused beams in dual-CP with three dual-CP feed-horns. The six main spots fulfill the typical multi spot satellite requirement with angular separation less than 0.56°, 0.4 dB loss in the gain, and cross-polarization level below 35 dB with respect to the maximum of radiation.

The Prototype of a Wideband Ku-Band Conical Corrugated Horn Antenna with 3-D Printing Technology

This study is about the design and production of a conical corrugated horn antenna used to feed reflector antennas in satellite communication (direct broadcast satellite-DBS) systems. The antenna designed with CST Microwave Studio program operates within wideband of 10.5-18.5 GHz at Ku-band. The prototype is realized with new generation 3D printing technology and conductive paint coating method, which makes the antenna lightweight and provides low cost and faster production. According to measurement results, the antenna has return loss almost better than 20 dB, gain value of minimum 14.5 dBi and sidelobe level of -18 dB at most within 1.76:1 frequency bandwidth. Antenna is observed to have a gain loss of at most 1.5-2 dB within the band as compared to the same antenna with high conductivity metal, which needs higher cost and production time for the manufacturing.