Satellite Communication Terminals Research Articles

Antenna Systems for Satellite Communication Terminals

This Roadmap presents the research trends on antenna systems for Satellite Communication terminals. To address the challenges posed by this application in terms of wide fractional bandwidth and large field-of-view, several antenna concepts and architectures are being investigated, which can be grouped in three main technology areas: fully electronic scan, fully mechanical scan with unconventional steering mechanisms and beam switching. Design techniques, current results and future developments are outlined, considering representative examples for each technology area.

Four‐channel GaAs multifunction chips with bottom RF interface for Ka‐band SATCOM antennas

AbstractReceiver and transmitter monolithic microwave integrated circuit (MMIC) multifunction chips (MFCs) for active phased‐array antennas for Ka‐band satellite communication (SATCOM) terminals have been designed and fabricated using a 0.15‐μm GaAs pseudomorphic high‐electron mobility transistor (pHEMT) process. The MFCs consist of four‐channel radio frequency (RF) paths and a 4:1 combiner. Each channel provides several functions such as signal amplification, 6‐bit phase shifting, and 5‐bit attenuation with a 44‐bit serial‐to‐parallel converter (SPC). RF pads are implemented on the bottom side of the chip to remove the parasitic inductance induced by wire bonding. The area of the fabricated chips is 5.2 mm × 4.2 mm. The receiver chip exhibits a gain of 18 dB and a noise figure of 2.0 dB over a frequency range from 17 GHz to 21 GHz with a low direct current (DC) power of 0.36 W. The transmitter chip provides a gain of 20 dB and a 1‐dB gain compression point (P1dB) of 18.4 dBm over a frequency range from 28 GHz to 31 GHz with a low DC power of 0.85 W. The P1dB can be increased to 20.6 dBm at a higher bias of +4.5 V.

A Ku-Band Foldable Reflectarray Based on a Maltese-Cross Microstrip Element

Introduction. Reflectarrays have a number of design and functional advantages over their closest analogue - reflector antennas (RA). Although microstrip elements are the most preferred reflectarray elements, single-layer microstrip elements do not allow accurate phase control due to the limited phase adjustment range and a high phase slope. The use of multilayer elements significantly complicates the antenna design and increases its cost. The development of a single-layer element that allows more than 360° phase adjustment and a low phase curve slope is urgent.Aim. To develop a single-layer microstrip phase-correcting element with a phase adjustment range of more than 360° and to design a reflectarray on its basis for operation in satellite communication networks.Materials and methods. Numerical studies were carried out using finite element analysis and the finite-difference time-domain method. Radiation patterns were measured using the near-field scanning method in an anechoic chamber.Results. A phase-correcting element based on a single-layer Maltese cross-shaped microstrip element with close to linear dependence of element size on the phase of the reradiated wave and more than 360° phase adjustment range was developed. On the basis of the investigated element, a foldable reflectarray was designed. The reflector consists of four subarrays, which provide its compact folding for transportation. The results of experimental studies confirmed a high efficiency of the reflectarray, the gain of which is 1.5 dB lower than that of an identical overall dimensions RA in a 7 % operating frequency band. The operating frequency band of the reflectarray in 1 dB gain zone was 11 %.Conclusion. On the basis of a Maltese cross microstrip element, it is possible to implement a single-layer reflectarray with a more than 10 % frequency band. The developed prototype showed the possibility of creating highly efficient foldable reflectarrays for operation in satellite communication and television terminals.

Integrated satellite-ground post-disaster emergency communication networking technology

The reconstruction of the communication network is a precondition for the smooth implementation of rescue and disaster recovery after geological disasters. Although traditional post-disaster emergency communication equipment, such as emergency communication vehicles, satellite access stations and satellite communication terminals, to a certain extent, can solve communication problems, the firmware of them makes such equipment faced with difficulty in adapting to the complex disaster environment, limited network coverage and poor mobility of such devices. To settle those problems, we have proposed an integrated satellite-ground emergency constructed-network after disaster technology. The nodes of the network specifically including Mesh AP (access point) nodes and satellite portable stations, adopt a portable design which can be easily carried by the Network deployer and deployed to the corresponding location. The actual deployment test results of the multi-site network show that our technical solution can build a stable emergency communication network within 30 ​min and support multi-user access, on which users can carry out audio and video communication, file transmission and other services.

Оценка реализуемости активной фазированной антенной решётки терминала системы спутниковой связи "Экспресс-РВ"

The basic principles of building a promising domestic regional satellite communication system "Express-RV", based on the highly elliptical orbit "Molniya" and intended for broadband access of civil sector subscribers to various public communication networks, in particular to the Internet, are considered. The main technical requirements for the antenna systems of mobile satellite communication terminals of the Express-RV system are formulated. The necessity of using active phased array antennas for a number of types of such terminals is justified. A brief overview of the principles of implementation and examples of the design of microstrip active phased array antennas, including their elementary emitters and individual modules, are given. The problem of the occurrence of the blinding effect inherent in flat microstrip gratings made on dielectric substrates is noted; measures to compensate for this effect are considered. The possibility of expanding the maximum scanning angle of a narrowly directed beam of an active phased array antenna by using a magnetically controlled scattering dielectric lens, as well as creating segment-dome structures of antenna systems in relation to mobile terminals of mobile satellite communications of the "Express-RV" system, is shown. Simple analytical relations are derived that allow us to estimate the number of elementary emitters required for the implementation of a receiving-transmitting active phased array antenna with specified technical characteristics: gain and maximum scanning angle; the corresponding dependencies are given. The cost of creating an antenna system based on an active phased array is estimated.

Research on Satellite Concealment Communication Method Based on WFRFT

Satellite signal concealment technology protects the safety of signal waveform by using signals with high power and specific parameter characteristics. However, with the development of modulation recognition and Successive Interference Cancellation (SIC) technology, the cover signal using conventional modulation methods can be cracked by non-cooperative receivers. In order to meet the safety communication requirements of portable satellite communication terminals, the idea of using local signal copies for self-interference cancellation in Paired Carrier Multiple Access (PCMA) is used for reference. This paper proposes a satellite secure communication method suitable for portable terminals, and introduces Weighted-type FRactional Fourier Transform (WFRFT) as a modulation method to mask the signal, thereby increase the difficulty of non-cooperative parties in identifying and demodulating the cover signal. Simulation shows that the method proposed in this paper improves the security of signal transmission, and the loss of the system's bit error rate is within an acceptable range after signal separation, which is suitable for practical use.

Analysis of Circularly Polarized CTS Arrays

This article presents an efficient analysis method for a novel continuous transverse stub (CTS) antenna. As opposed to state-of-the-art CTS antenna designs, the proposed architecture achieves circular polarization using a single CTS array and without any polarization converter. The structure consists of long radiating slots/stubs fed by over-moded parallel-plate waveguides. More precisely, the transverse electromagnetic (TEM) mode and the first transverse electric (TE1) mode of the feeding waveguides are used to generate a circularly polarized field. The array is analyzed using a spectral mode-matching method. First, the active reflection coefficient of the infinite array is derived in closed form. A windowing approach is then adopted to compute the radiation patterns of finite-size arrays. Numerical results obtained with this method are in excellent agreement with full-wave simulations, carried out with a commercial software. The performance of this class of CTS antennas has been investigated using the developed model. It is theoretically demonstrated that the proposed array can be designed to attain an axial ratio (AR) lower than 3 dB over a 52.9% relative bandwidth at broadside. Furthermore, the active input reflection coefficient is lower than −10 dB over a 40.8% relative bandwidth, when the array steers its main beam at $\theta _{0}=45^\circ $ . This solution is an attractive candidate for next generation satellite communication terminals.

Fast Acquisition Scheme of the Spread Spectrum Signals for Satellite Communications

A four-channel parallel acquisition scheme combining partial matched filters and fast Fourier transforms (PMF-FFT) is proposed for the fast acquisition of the spread spectrum signals in satellite communication terminals installed into the offshore buoys with the high-dynamic movement, which is used tofinish data communication missions between the buoys and the satellite. Compared with traditional code phase FFT scheme, the new scheme reduces the maximum acquisition time to 26.5% and the maximum computation amount to 46.9%. It also improves about 4 times in the frequency resolution and 1.6 dB in the receiving sensitivity at the expense of computation complexity compared to PMF-FFT scheme. The parallel PMF-FFT scheme greatly reduces scallop loss, thus ensuring acquisition sensitivity. The parallel PMF-FFT scheme within the satellite communication terminal can ensure the fast and stable tracking of satellite signal by the violently moving antenna within 20 ms under level-4 sea state.

Research about dynamic programming technology of Marine cloud-communication

In order to meet the increasing requirements of marine data transmission with the exploitation of the ocean, a cloud-communication network structure suitable for marine communication, and its operation mode and design method are proposed through analysis of existing communication technologies. Firstly, the structure of the cloud communication network is designed. The controllers manage the satellite communication terminals (including communication objects and nodes) of the ships, offshore facilities and shore-based data centers through the cloud communication network. Then, based on the network structure, the corresponding operation mode is proposed, that is, the dynamic programming technology is used to centrally control the communication terminal, and multiple nodes are called to assist to form a “cloud channel” to coordinate the communication task. Finally, the two main points of channel dynamic programming technology are analyzed. One is to provide suitable communication coordination nodes for communication objects, and the other is to allocate the best communication channels. Aiming at the selection algorithm of cooperative nodes and communication channels, the design ideas and basic models of the algorithm are proposed, and the feasibility of channel dynamic programming is illustrated.

Low-Cost Ka-band Switchable RHCP/LHCP Antenna Array for Mobile SATCOM Terminal

Achieving a functional antenna for mobile satellite communications terminals in Ka-band is probably one of the most challenging tasks in current antenna engineering, particularly bearing in mind they need to be low profile and “affordable.” This quest is involving many companies in the field. Our contribution represents one of such efforts. The antenna is based on a slotted waveguide array technology to maximize efficiency and it features a number of novel solutions, going from its robust polarization switching mechanism, to the use of a thin wideband polarizer and the utilization of groove gap waveguides. This communication reports the measured data of a fully functional prototype to validate its novel contributions.

K/Ka-band dual-polarized SIW-fed lens antennas for Rx/Tx integration

AbstractThis contribution deals with array elements for K/Ka-band satellite communication terminals. It proposes an end-fire design realized in substrate integrated waveguide technology and featuring dual-band functionality, and dual circular polarization. The latter is achieved by means of a dual-band orthomode transducer. An extended hemispherical dielectric lens ensures good matching and radiation properties. The feed structure is composed of a multilayer printed circuit board and tapered superstrates. The design procedure of the components is explained in detail and three different variants of the antenna are compared. The measured scattering and far-field parameters validate the concept.

Innovative Antenna Front Ends from L-Band to Ka-Band [Antenna Applications Corner

We provide an overview of several high-tech antenna apertures and antenna front ends, developed and realized by IMST (in some cases in cooperation with partners) over a time span of more than 15 years. These front ends have become key components for bandwidth-hungry applications such as mobile/nomadic satellite communication terminals (satcom-onthe-move) and radar systems. Satcom terminal data throughput for multimedia services provided via satellite links is increasing rapidly. Such terminals require highly complex radio-frequency (RF) systems capable of tracking satellites despite movements of the mobile terminal platform. Depending on the type of platform (land mobile, maritime, or aeronautical), the requirements for these front ends and the resulting complexity can vary. This also applies to radar sensors for automotive applications and unmanned aerial vehicle (UAV) platforms, for example. In all of these front ends, the antenna architecture is always based on a phased/steerable array topology. Such systems are, in general, complex configurations: they require not only RF circuitry but also complex baseband processing and highly accurate sensor platforms to perform adequate beam steering and tracking. The overall design must be cost-effective, a very demanding requirement. Through the years, IMST has developed a customized set of highly specialized skills to address all of these challenges.

MIMO H∞ control of three-axis ship-mounted mobile antenna systems

ABSTRACTThe need for on-line information in any environment has led to the development of mobile satellite communication terminals. These high data-rate terminals require inertial antenna pointing error tolerance within fractions of a degree. However, the base motion of the antenna platform in mobile applications complicates this pointing problem and must be accounted for. Gimbaled motorised pedestals are used to eliminate the effect of disturbance and maintain uninterrupted communication. In this paper, a three-axis ship-mounted antenna on a pedestal gimbal system is studied. Based on the derived dynamic model of the antenna pedestal multi input-multi output PID and H∞ linear controllers are designed to stabilise the antenna to keep its orientation unaltered towards the satellite while the sea waves disturb the antenna. Simulation results are presented to show the stabilisation performance of the system with the synthesised controllers. It is shown through performance comparison and analysis that the proposed H∞ control structure is preferable over PID controlled system in terms of system stability and the disturbance rejection.

Beam-Scanning Continuous Transverse Stub Antenna Fed by a Ridged Waveguide Slot Array

A continuous transverse stub (CTS) array antenna is presented for beam-scanning applications. Rotatable ridged waveguide slot array (RWSA) is used as a line source to feed a CTS array for the first time. The proposed RWSA has easy design, compact structure, light weight, and easy sidelobe control. The CTS array and RWSA can be designed and optimized separately. A good beam-scanning capability of ±30° is achieved by rotating the RWSA at almost the same angles, thus obtaining a fine beam-scanning resolution. The measured aperture efficiency exceeds 60% in the entire beam-scanning range. Therefore, the proposed antenna can be a good alternative for radar systems and satellite communication terminals, which require low cost and high gain.

High-Efficiency Stacked Shorted Annular Patch Antenna Feed for Ku-Band Satellite Communications

Reflector-based satellite communication (SatCom) terminals require high sensitivity to minimize overall antenna size, and in view of their simplicity and high radiation efficiency, horn antennas are used almost exclusively as reflector feeds. As these terminals become more complex, smaller and more compact feeds that can be directly integrated with microstrip circuits are desirable. Standard microstrip antennas (MSAs) have unacceptably low radiation efficiency for use as reflector feeds. We show that the stacked shorted annular patch (SSAP) can be used as a replacement for horn feeds and achieves higher radiation and spillover efficiencies than conventional patch antennas due to the absence of distribution networks and dielectric substrates. Using a half-wavelength stacked patch as a director realizes a pattern that achieves high illumination efficiency with standard parabolic reflector geometries. Simulation and measurements show that the compact SSAP may be the first reported nonwaveguide feed antenna to achieve sensitivity comparable to that of a conventional horn feed.

Design of Microstrip Patch Array Antenna for Ku-Band Applications

For satellite communications terminals, this paper deals with the design of a Micro strip Patch Array Antenna for KU-band applications that resonates at 12.3 GHz respectively. The substrate used for design is ARLON AD300N and the software used for simulation is Agilent ADS Momentum. This design expressed the array antenna in 8-element.It approach their corresponding results are validated based on their antenna parameters like VSWR, gain, directivity and power radiated and so on. One of the microstrip antennas MSA arrays achieved a radiation efficiency of 100%, which is among the best reported efficiencies for this resonating frequency and class of antennas.

Low-Cost Vertical Patch Antenna With Wide Axial-Ratio Beamwidth for Handheld Satellite Communications Terminals

This paper presents a low-cost circularly polarized (CP) small antenna for handheld satellite communications terminals in S-band. It consists of an elliptical vertical patch antenna (VPA) element backed by an elliptical air cavity of different ellipticity. Two dielectric substrates, each with an elliptical opening, are stacked together and mounted onto a ground plane. The rim on the smaller opening of the upper substrate is conveniently plated with conductor to form the VPA, whereas the larger opening of the lower substrate and the ground plane forms the air cavity. The elliptical VPA, when excited by a probe feed, generates CP radiation. Dielectric loading of the VPA not only achieves its size reduction but also widens the 3-dB beamwidth. The fabricated antenna has a measured gain of 5.1 dBic at 3.71 GHz, impedance bandwidth of 12.6%, 3-dB beamwidth of 102° and axial-ratio beamwidth (AR <; 3.0 dB) of 121°.

Noise figure reduction by port decoupling for dual circular polarised microstrip antenna

A planar dual circular polarised (CP) feed is highly desirable for dish-type satellite communication terminals, but isolation between ports is typically poorer for CP microstrip antennas than for linearly polarised elements. Mutual coupling between the output ports of a dual CP planar feed can affect the equivalent noise temperature of the satellite ground terminal receiver. A port decoupling network is designed for a single-layer dual CP microstrip antenna to increase the isolation to >20 dB between the antenna ports while maintaining CP quality. The effect of decoupling for the single-layer dual CP feed on the performance of a high sensitivity dual polarised receiver for satellite communication applications is analysed.

English

With the advancement of wireless communication systems and increasing importance of other wireless applications, wideband and low profile antennas are in great demand for both commercial and military applications. Multi-band and wideband antennas are desirable in personal communication systems, small satellite communication terminals, and other wireless applications. Recent efforts by several researchers around the world to combine fractal geometry with electromagnetic theory have led to a plethora of new and innovative antenna designs. This paper describes the theories and techniques for shrinking the size of an antenna through the use of fractals. Fractal antennas can obtain radiation pattern and input impedance similar to a longer antenna, yet take less area due to the many contours of the shape. Fractal antennas are a fairly new research area and are likely to have a promising future in many applications.

Rate Control for Network-Coded Multipath Relaying with Time-Varying Connectivity

This paper presents techniques for achieving high throughput in delay-constrained, multihop wireless communication networks with time-varying link connectivity. We develop a rate-controlled, multipath strategy using network coding, and compare its performance with that of multipath flooding and with the performance of traditional single-path strategies. These performance comparisons include both theoretical benchmarks and simulation results from cooperative relay scenarios, which incorporate different sets of link connectivity statistics that are drawn from field tests of mobile satellite communication terminals. The results indicate that with appropriate rate-control, network coding can provide throughput performance comparable to multipath flooding of the network while utilizing bandwidth nearly as efficiently as single-path routing.