A Multiband Antenna for Satellite Communications on the Move

SummaryA novel multiband pinwheel fractal antenna with monopole configuration is proposed. The pinwheel fractal antenna has been fabricated on a commercially available FR4 substrate with a thickness of 1.6 mm. This paper proposes a novel pinwheel antenna with a 50% reduction in the dimension of width with a reduced level of return loss. The proposed antenna has multiband characteristics covering the bands of GSM (900 MHz), DCS (1710 GHz), PCS (1900 MHz), UMTS (1920 MHz), and WLAN (2.4–5.9 GHz) applications. The projected antenna resonates at multiple frequencies with acceptable antenna gain and directivity. The proposed antenna design is optimized by particle swarm optimization (PSO) algorithm. The parametric studies and the design rule for the proposed fractal have been reported. The prototypes of the proposed multiband antenna have been demonstrated. The measured and simulated results ensure the multi‐resonance characteristics and authorize the projected design method and gratify the necessities of handheld wireless communication systems. The performance analysis proves that the proposed novel pinwheel antenna provides reduced return loss.

This paper has two objectives: to discuss the role of small satellites in the satellite communications R&D (research and development) in the IT (Information Technology) era, and to show communications technology topics in small satellite applications. The need for small satellite communications is first discussed. The future (next three decades) vision of satellite communications R&D is then described, corresponding to the recent rapid increase of capacity of terrestrial links. Third, the role of small satellites in future satellite communications R&D is discussed. Finally, small satellite related communications technology topics are described to show that there are many interesting research issues.

In this communication, artificial neural networks are used to estimate the initial structure of a multiband planar antenna. The neural networks are trained on a set of selected normalized multiband antennas characterized by time-efficient modal analysis with limited accuracy. Using the Deep Learning Toolbox in Matlab, several types of neural networks have been created and trained on the sample planar multiband antennas. In the neural network learning process, suitable network types were selected for the design of these antennas. The trained networks, depending on the desired operating bands, will select the appropriate antenna geometry. This is further optimized using Newton’s method in HFSS. The use of the neural pre-design concept speeds up and simplifies the design of multiband planar antennas. The findings presented in this paper will be used to refine and accelerate the design of planar multiband antennas.

This paper presents the design and optimization of a multi-band antenna intended for use in satellite communications. The antenna consists of a pentagonal patch multi-band antenna that uses a metamaterial of split ring resonators to enhance its electromagnetic performance. Some disadvantages associated with conventional antennas include being large, having a limited bandwidth and producing high levels of signal reflection. The performance of the antenna is effective in the C, X, and Ku satellite communication bands. The proposed SRR-based pentagonal patch antenna has a low level of reflection with S11<-10dB; a gain of 4.96dB; and a VSWR<2 indicating that very little of the transmitted signal will be reflected back from the antenna. The radiation pattern of the proposed antenna is also very concentrated in 2D space, resulting in higher signal strength and lower interference. Ansys HFSS simulation of the proposed antenna design indicated potential applications for satellite internet, global positioning, remote sensing, and Internet of Things (IoT) systems. Because of its low weight, low cost, and scalable design characteristics, the proposed antenna is expected to be fully compatible with next generation satellite systems. Future improvements to the proposed antenna may include adaptive beamforming and tunable metamaterials to further enhance its satellite communication capabilities.

Transmission planning for military and commercial satellite communications systems has traditionally followed separate (but parallel) paths and led to the development of distinct sets of tools which can handle either only military satellite systems or only commercial satellite systems. With the need to operate DoD communications networks on both military and commercial satellites a unified transmission planning model is required which can model both types of satellite systems in a common framework. This paper proposes a unified approach to transmission planning for military and commercial satellite systems, and discusses both the common requirements for such a transmission planning model, and those requirements specific to the structure and operation of military satellites such as the use of saturated transponders, null-forming multi-beam antennas, special waveform modulation techniques, jamming threats, etc., which need to be treated differently from their commercial counterparts. Software models are proposed for some of the key requirements, and issues related to their implementation are discussed. The paper also describes the capabilities of existing software which can be used for transmission planning on commercial satellites, and how it can be augmented to function in the military satellite communications environment.

A 64-element, Ku-band, active phased-array antenna developed for application in communications satellites is presented. Antenna radiation pattern and spatial isolation measurements show good agreement with predictions. In order to minimize the performance variations among the array elements, the 5-b digital phase shifter, the 50-b digital attenuator, and the amplifiers have been realized using MMIC (monolithic microwave integrated circuit) technology. This allowed the realization of 64 active modules whose amplitude and phase variations over 11.7 to 12.7 GHz are within +or-1.5 dB and +or-10 degrees . The successful development of this broadband active phased array has demonstrated the maturity of MMIC technology and the feasibility of active arrays in future communications satellites. >

A double-layered constellation for a future global satellite communications network connected by optical intersatellite links has been proposed. The constellation consists of lower layer satellites for mobile and personal satellite communications, and upper layer satellites for large- capacity fixed satellite communications and feeder links. Optical inter-satellite links, which can perform high-capacity communications with small terminals, are used for all intersatellite data transmission. Although a polar orbit constellation offers the merit of simpleness in network configurations, the inclined orbit constellation offers the potential for reducing the required number of satellites, improving link properties, and enhancing the coverage in middle and low latitudes, by selecting the most adequate inclination of the orbits. The optical inter- satellite link properties, coverage properties, and required number of satellites are evaluated for constellations using inclined orbits, and then compared with those of a polar orbit constellation. Three constellation types in each layer achieving continuous double coverage are assumed. For each constellation, the relations between these properties and the inclination of the orbits are examined. The basic parameters of optical inter-satellite links on satellite constellations using inclined orbits are also shown.

Experiments on mobile satellite communications are being carried out to determine if they are technically feasible for future domestic satellite services in the Experimental Mobile Satellite System project, which uses Engineering Test Satellite-V. Experimental ISDN (integrated services digital network) basic-rate communications services have also been offered for marine vehicles. The authors describe the configuration of an experimental system for maritime ISDN satellite communications, and the characteristics of ISDN basic-rate interface connections for the digital telephones, G4 facsimiles, and color video-phone terminals of terrestrial ISDN services. This experiment provided much information for designing future mobile satellite communications systems. Moreover, it indicates that forward error correction in a mobile satellite link with poor transmission quality is very effective at improving the communication quality of mobile satellite systems. >

Using quantum computing algorithms in future satellite communication

HexPak is a modular deployable spacecraft structure that keeps pace with the growing demand for higher and higher performance for future military and commercial communications satellites, foremost among them heat rejection from high power communications payloads and limited area on the Earth deck. HexPak consists of hexagonal bays that stack as a self-supporting structure for launch and deploy on station to a planar structure with a deck area many times the fairing cross-section. The large deployed area supports payload apertures much greater than conventional structures, hosts multiple payloads, offers heat rejection significantly beyond traditional designs, and supports multiple satellites per launch with unprecedented volumetric efficiency. The modular structure also provides efficiencies in manufacturing that save time and money. The structure is also ideally suited for structural integration of harnessing and provides an ideal platform for emerging network based, plug’n’play avionics. Since each bay is fabricated and tested individually, bays can be built and tested in parallel and then integrated into a complete spacecraft with the manufacturing time/unit mass greatly improved over more traditional structures. Since the stowed structure is inherently self-supporting, minimal additional structure for launch support is required for single or multiple manifest scenarios resulting in a much more favorable mass to orbit comparison to traditional spacecraft structures. Since the geometry is also hexagonal, there is near optimal utilization of the available fairing volume. HexPak thermal dissipation performance in GEO is examined quantitatively, and strategies for thermal control of different classes of components are developed. Also presented are results of a mechanical hardware testbed deploying three 2 meter bays, which includes a fiber based plug’n’play network supporting high speed interbay communications.

This paper proposes a nonuniform-bandwidth onboard channelizing and switching architecture for broadband satellite communications. Detailed simulations are carried out to explicitly verify the flexibility and scalability of the proposed architecture. Significant performance improvement and reduction in memory size have been demonstrated, making the digital channelization technique attractive for future flexible communications satellite payload architectures.

High Throughput Satellite (HTS) systems still offer much less bandwidth per user with respect terrestrial broadband networks. In order to reach a very high throughput towards “Tbit/s connectivity”, an important breakthrough is needed in terms of bandwidth availability which can be offered by the use of Extremely High Frequency (EHF) bands (30–300 GHz). In particular, Q-V band (30–50 GHz) and W-band (70–110 GHz) offer very promising perspectives, being not used for commercial systems and offering a large part of the spectrum allocated for satellite services. However, it is well known that EHF band transmission through the atmosphere is subject to absorption and dispersive effects in amplitude and phase that have to be carefully characterized. In this framework, some mitigation techniques have to be analyzed and properly tuned in order to realize an efficient transmission. In this paper, the current experimental activities to support future EHF satellite communication systems are reported, with reference to the Italian Space Agency Q/V-band satellite communication experimental campaign. In particular, a new error model for QPSK modulation scheme has been developed from the experimental data. This error model can be used for the design of optimized channel coding and adaptive transmission schemes for Q/V band satellite channels.

This paper considers satellite communication networks where each satellite terminal is equipped with energy harvesting (EH) devices to supply energy continuously, and randomly transmits bursty packets to a geostationary satellite over a shared wireless channel. Packet replicas combined with a successive iteration cancellation scheme can reduce the negative impact of packet collisions but consume more energy. Hence, appropriate energy management policies are required to mitigate the adverse effect of energy outages. Although centralized access schemes can provide better performance on the networks’ throughput, they expend extra signallings to allocate the resources, which leads to non-negligible communication latencies, especially for the satellite communication networks. In order to reduce the communication overhead and delay, a distributed random access (RA) scheme considering the energy constraints is studied. Each EH satellite terminal (EH-ST) decides whether to transmit the packet and how many replicas are transmitted according to its local energy and EH rates to maximize the average long-term network throughput. Owing to the nonconvexity of this problem, we adopted a game theoretic method to approximate the optimal solution. By forcing all the EH-STs to employ the same policy, we characterized and proved the existence and uniqueness of the symmetric Nash equilibrium (NE) of the game. Moreover, an efficient algorithm is proposed to calculate the symmetric NE by combining a policy iteration algorithm and the bisection method. The performance of the proposed RA scheme was investigated via numerous simulations. Simulation results showed that the proposed RA scheme is applicable to the EH devices in the future low-cost interactive satellite communication system.

The scope of the present paper is to outline ESA’s R&D directions for the development of new technologies required for future broadband satellite communication systems. The document outlines likely trends and technological issues that will need to be tackled in the medium and long term (e.g. 5 to 10 years) to improve by more than one order of magnitude satellite communication networks efficiency, thus increasing their economical appeal. It is shown that by timely developing in a co-ordinated fashion a number of techniques and technologies encompassing both ground and space segment it is possible to attain the ambitious target set forth above.

Modern day geostationary orbit communication satellites require antennas with more and more beams to increase the total system capacity. There is also an interest in developing antenna geometries that reduce the spacing between beams to enhance the spectral density over the service area, typically a continental or sub-continental coverage. On smaller platforms, or as a secondary payload on larger satellites, there is also a need to produce multiple beam antenna solutions using only one reflector. In this context, a patent pending multiple-feed-per-beam feed system implementation technique has been developed. Compared to state-of-the-art solutions, the proposed technique is found to increase significantly the spectral density over the service area while maintaining the key performance indicators at antenna level (i.e. aggregate gain and C/I). A specific design is presented for a geostationary broadband mission, which displays an increase of about 50% in the number of beams, assuming same reflector geometry, feed array size and service area. The proposed technique also facilitates the mechanical design of the feed system and is therefore considered a promising solution for the design of future broadband communication satellites.