Ka-band Satellite Communication Systems Research Articles

A low-cost wideband phase shifter for two-way mm-wave phased array antenna system

This paper presents a wideband, low-cost, high-performance, and continuous phase shifter for millimeter-wave (mm-wave) phased array systems. Its operational principle is based on modifying the propagation mode of a grounded coplanar waveguide (GCPW) line by placing a high dielectric constant slab over the GCPW line. The propagation constant and hence the phase shift is varied by changing the air gap height between the GCPW line and the dielectric slab. As a proof of concept, a piezoelectric transducer is used to precisely control this air gap height. A printed circuit board-based phase shifter prototype has been designed, fabricated, and tested at two different frequency bands (19–21 and 28.5–30.5 GHz), which are the downlink and uplink bands, respectively, of the Ka-band two-way satellite communication system. A continuous and almost linear phase–voltage characteristic has been achieved experimentally with average phase shift variations 170° and 260° over the two bands, respectively. The footprint of the proposed phase shifter is 2.1 mm×3 mm, which is quite small and suitable for low-profile mm-wave applications. The average insertion losses over the two bands are <0.53 and 2.35 dB with very low variations±0.22 and ±0.35 dB, respectively.

Ka-band antenna arrays with dual-frequency and dual-polarized patch elements

In this contribution a dual-band, dual-polarized microstrip antenna element for array applications is presented. The patch antenna is designed to operate simultaneously at around 30 and 20 GHz, the up- and downlink frequencies of modern Ka-band satellite communication systems. The antenna is smaller than half the freespace wavelength at 30 GHz to enable its utilization as array element of dual-band ground terminals. Integrating transmitter and receiver circuits allows, in turn, for a very compact active terminal solution. To minimize production cost, the design is carried out in standard multilayer printed circuit board technology. The antenna features two distinct polarization ports suitable for either dual linear or dual circular polarization if both ports are excited in quadrature. The single antenna design process is described in detail and simulation and measurement results are presented. Finally, different arrays based on this patch antenna are evaluated by simulation and measurements.

Research of Rain Attenuation of Ka-Band Satellite Communication System

Ka-band satellite communication system has some advantages including a large bandwidth, a huge capacity, a narrow beam, a small terminal size, which makes it a trend in future satellite communications. However, the system is now faced with great challenge-meteorological factors, which aroused suspicion among researchers about its realization. In this paper, the feature of rain fade is analyzed and several compensation methods are presented.

Ka 대역 위성 출력 전력 제어 기술 연구

Ka 대역 위성통신 시스템에서 강우 감쇠 보상을 위해서는 위성 탑재체에서 강우 지역의 출력 전력을 높일 수 있는 시스템이 요구된다. Ka 대역 출력 전력 제어 기술은 위성 탑재체에서 하향 링크(19.8 ~ 22.2 GHz)의 출력 전력 조정을 가능하게 한다. 본 논문에서는 다중 빔 안테나와 다중 입출력 증폭기를 이용한 Ka 대역 위성 출력전력 제어 기술에 대하여 소개한다. 한반도 상에 8개의 빔을 형성하기 위해 배열 급전 소자와 반사판으로 구성된 다중 빔 안테나가 설계되었다. 빔 당 목표 EIRP는 59 dBW 이상이며, 강우 감쇠 보상을 위한 전력 제어 기능은 강우 지역에 비 강우 지역 대비 최대 6 dB의 EIRP 상승이 가능하도록 설계하였다. 다중 입출력 증폭기는 다중 빔 안테나와 함께 구성될 때 위성 출력 전력 제어를 위해 효과적으로 사용될 수 있다. <TEX>$4{\times}4$</TEX> 다중 입출력 증폭기가 기술 검증을 위해 제작되었으며 Ka 대역 위성 송신 주파수 대역에서 24 dB 이상의 격리도 성능을 나타낸다. For Ka-band satellite communication system, a new flexible payload technologies which can compensate rain attenuation have to be developed. The Ka-band satellite output power control technology enables to adjust downlink output power of satellite payload in Ka-band (19.8 ~ 22.2 GHz). In this paper, we introduce multi-beam antenna with multi-port amplifiers for Ka-band flexible output power allocation system. We have designed multi-beam antenna with array-fed reflector to form 8 beams on the Korean Peninsula. The target EIRP per beam is more than 59 dBW. The system is designed to present 6 dB boost beams for rainfall areas. Individual beams were optimized by the excited amplitude and phase of feed elements of the feed cluster. The multi-port amplifier(MPA) is one of effective approaches for flexible power allocation in combination with multi-beam antenna. In case of using MPA in multi-beam system, the inter-port isolation characteristic of MPA is important parameter to avoid interference among the output ports. In this paper, we propose a new MPA structure that consists of two <TEX>$4{\times}4$</TEX> Buttler matrixes and phase/amplitude controllable power amplifier modules.

Performance evaluation of digital beamforming strategies for satellite communications

Smart antennas are becoming one of the promising technologies to meet the rapidly increasing demands for more capacity of satellite communication systems. A main component in a smart antenna system is beamforming. Because of the limitations of analog beamforming, digital beamforming will be employed in future satellite communication systems. We evaluate the performance of various digital beamforming strategies proposed in the literature for satellite communications: 1) single fixed beam/single user, 2) single fixed beam/multiple users, 3) single adaptive beam/single user, and 4) single Chebyshev dynamic beam/multiple users. Multiple criteria including coverage, system capacity, signal-to-interference-plus-noise ratio (SINR), and computation complexity are used to evaluate these satellite communication beamforming strategies. In particular, a Ka-band satellite communication system is used to address the various issues of these beamforming strategies. For the adaptive beamforming approach, subarray structure is used to obtain the weights of a large 2D antenna array, and a globally convergent recurrent neural network (RNN) is proposed to realize the adaptive beamforming algorithm in parallel. The new subarray-based neural beamforming algorithm can reduce the computation complexity greatly, and is more effective than the conventional least mean square (LMS) beamforming approach. It is shown that the single adaptive beam/single user approach has the highest system capacity.

Experimental Communication Payload Project of the ROCSAT-1 Satellite

In this paper, an experimental communication payload (ECP) project of the Republic of China's ROCSAT-1 satellite program is introduced. The objective of the project is to study implementation techniques of the low earth orbit Ka-band satellite communication systems and to conduct Ka-band satellite communication experiments to study the performance of the video/voice/data/fax transmission and Ka-band propagation effect. The ECP consists of three subsystems, termed the ECP space segment (ECPSS), ECP ground segment (ECPGS), and ECP Science Data Distribution Center (ESDDC). The ECPSS provides a Ka-band bent-pipe transponder and a downlink beacon. The ECPGS is comprised of a fixed ground station with both transmitting and receiving capabilities and a transportable receive-only ground station. The ESDDC is responsible for scheduling the execution of various experiments, setup of configuration parameters of ECP, and dissemination of the pre-/post-experiment data.

ACTS propagation experiment: experiment design, calibration, and data preparation and archival

The National Aeronautics and Space Administration Advanced Communications Technology Satellite (ACTS) propagation experiment was designed to obtain slant-path attenuation statistics for locations within the United States and Canada for use in the design of low-margin Ka-band satellite communication systems. Experimenters at seven different locations have collected propagation data for move than two years. The propagation terminals used for the experiment were identical. A single preprocessing program was used by the experimenters to provide for automatic calibration, generation of attenuation histograms, and data archival. In this paper, the calibration procedures are described mid estimates given for measurement accuracy. ACTS provided beacons at 20.2 and 27.5 GHz for use in making attenuation measurements. In addition to the beacon receivers, each ACTS propagation terminal has two total power radiometers with center frequencies at the beacon frequencies. The radiometers are used to establish the beacon signal reference levels needed for calculating beacon attenuation values. For the combined radiometer and beacon measurement system, the attenuation measurement error was less than a maximum of 1.0 dB and was generally less than 0.3 dB. The dynamic range for attenuation measurement varied from site to site depending on location relative to the peak of the satellite beacon antenna pattern. For locations within the continental United States, the dynamic range was better than 20 dB.

Channel characterization and modeling for Ka-band very small aperture terminals

An increasing number of commercial applications are being promoted for future Ka-band satellite communication systems. Many of these systems will involve low-margin very small aperture terminals (VSATs). These systems are subject to important atmospheric propagation degradations that affect the quality of transmission and the link availability. The objective of this paper is to characterize the Ka-band channel and evaluate the performance degradation in VSATs resulting from atmospheric propagation, impairments. In particular microwave propagation through a turbulent atmosphere is discussed, and the statistical characterization and modeling of tropospheric scintillation is reviewed. Moreover, the paper extends the method proposed by Filip and Vilar (1990) for the long-term characterization and modeling of the combined effect of rain impairments and scintillation. Specifically, the increase in noise temperature during rain events is added to the Filip-Vilar model. This leads to a five-parameter global fading distribution that is used to predict typical Ka-band satellite link outage time, the mathematical formalism is illustrated by applying the method to the selected case of the Advanced Communications Technology Satellite (ACTS)-Georgia Tech experimental downlink. Numerical results confirm that both rain impairments and scintillation are important factors in the design of Ka-band VSAT systems.

Results from the Virginia Tech propagation experiment using the Olympus satellite 12, 20 and 30 GHz beacons

A comprehensive set of propagation experiments was performed using the Olympus satellite 12, 20, and 30 GHz beacons. This set of experiments is unique in North America because of simultaneous reception of signals spanning the Ku- and Ka-bands from the same orbital slot, which permits direct inference of the frequency behavior of signal variations. The elevation angle from the receiving site in Blacksburg, VA, to the satellite was 14 degrees. Beacon, radiometric, and weather data for one year were analyzed. The statistical results for rain rate, beacon attenuation, attenuation ratios, radiometrically derived attenuation, fade duration and fade slope are presented. They are important to the design of Ku- and Ka-band satellite communication systems. The beacon attenuation results include cumulative statistics for attenuation with respect to free space and with respect to clear air. Attenuation ratio data are presented using attenuation with respect to clear air to focus on rain effects. Instantaneous attenuation ratios computed from instantaneous beacon levels were found to be nearly identical to statistical attenuation ratios obtained from cumulative attenuation statistics at each frequency.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fade countermeasures at Ka band for olympus

AbstractFade countermeasure techniques that can be applied to Ka band satellite communication systems are reviewed. Considered in detail are diversity, adaptive forward error correction, fade spreading, up‐link power control and adaptive TDMA. The techniques are compared for their effectiveness at Ka band, and recommendations are made for operating systems. The two important control techniques of fade detection and fade control are discussed in terms of their ease of implementation for each countermeasure technique. Details of a planned experiment to evaluate the application of fade countermeasures to VSAT networks via the Olympus satellite are presented.