Wideband Satellite Research Articles

Design and Implementation of Transparent Cross‐Polarization Interference Compensation in a Wideband Dual‐Polarization Satellite Receiver

ABSTRACTIn this paper, simultaneous transmission on two orthogonal antenna polarizations in a polarization division multiplexing (PDM) fashion is studied for wideband satellite communication links using dual‐polarization satellite receivers for the purpose of doubling the data rate. In order to mitigate the cross‐polarization interference (XPI), a new digital blind and transparent XPI compensation method is proposed, coined as XPI correlation learning estimation and adaptive reduction (XPI‐CLEAR). The received signal‐to‐noise‐and‐interference ratio (SNIR) and packet‐error rate (PER) performance with this non‐data‐aided and non‐decision‐directed method is assessed in a comprehensively modelled XPI channel with effects such as depolarization due to atmospheric conditions, imperfect cross‐polarization discrimination (XPD) of the antennas at the transmitter and the receiver, memory effects due to frequency selectivity of the XPD, and differential frequency offset (DFO) between the two channels. The application of the XPI‐CLEAR method presents considerable energy efficiency improvements for all the studied XPI channel effects, and is particularly beneficial for higher order modulation. A low‐complexity hardware implementation with symbol rates up to 500 MBaud validates the XPI‐CLEAR method as a practical solution to increase the data rates of the satellite air interface and to achieve the doubling of the throughput of the satellite link by the use of PDM.

Research on onboard multistage digital demultiplexer for satellite communication based on MF-TDMA system

A new multicarrier multi-rate digital demultiplexer system structure based on MF-TDMA(Multi-Frequency Time Division Multiple Access) in a wideband satellite communication system is described. Compared with the traditional tree multicarrier demultiplexer method, the new structure uses a half-band filter instead of the quadrature mirror filter, which has three advantages: 1) It fully avoids the shortcomings of the traditional method, such as confusion distortion and amplitude distortion. 2) The computation to achieve filtering is reduced by nearly half. 3) It effectively improves the demodulation performance of the system. In this paper, the new structure performs the multistage digital demultiplexer and demodulation of the MF-TDMA signal. The results show no obvious signal distortion, which is demultiplexed by the new structure. The bit error rate of the demodulated signal is better than that of the traditional single carrier demodulator. The bit error rate is very close to the theoretical value of QPSK demodulation.

A UWB Metal Waveguide Slot Array Antenna Based on Hybrid Resonant Structural Components

Due to their high reliability, anti-interference, and power capacity, metal waveguide slot array antennas are commonly used in harsh and extreme working conditions. However, the fractional bandwidth of waveguide slot array antennas is usually not wide enough (<20%), which limits the performance of the microwave system. Aiming at expanding the bandwidth, this letter proposes a metal slot array antenna utilizing hybrid resonant structures. Five resonance frequency points are simultaneously excited and are subtly arranged, resulting in a great expansion of the working frequency band. The measured results of the metal slot array antenna demonstrate that the working frequency band is from 7.35 to 10.05 GHz and the fractional bandwidth is expanded to 31%. The average realized gain is 15 dBi and the polarization is lower than −20 dB in the whole working frequency band. Therefore, this ultrawideband metal slot array antenna can not only enable the electronic equipment to work in harsh environments, such as space, but also improve the system performance in applications, such as wideband satellite communication and wideband radar imaging.

The technology platform of the EIVE CubeSat mission for high throughput downlinks at W-band

This paper details the motivation and the status of a new satellite mission, which targets the in-orbit verification of a wide band satellite communication link, operating in the high millimeter-wave regime at 71–76GHz. Under ideal weather conditions, data rates over 15Gb/s in complex modulation formats are expected to be demonstrated in-orbit, while data rates over 6Gb/s are still expected under adverse atmospheric and weather conditions. The scientific payload, hosted by a 6U-CubeSat platform, comprises a high-performance W-band transmitter with GaN-based solid state power amplifiers, an InGaAs-based low-noise receiver and a modern FPGA-based digital processing unit, realizing arbitrary waveform generation functionality and 4k image/video storage. The ground terminal employs a highly directive Cassegrain antenna with coarse GNSS and fine multi-mode RF tracking and a low-noise receiver together with an integrated high-speed digital processing and storage unit.

Square Waveguide Polarizer with Diagonally Located Irises for Ka-Band Antenna Systems

This article presents the results of development and optimization of a new square waveguide polarizer with diagonally located square irises. The application of suggested geometrical modification of irises form and location instead of a standard wall-to-wall irises configuration allows to exclude 45-degree twists between wideband waveguide polarizer and orthomode transducer of a dual-polarized antenna feed system. In addition, a waveguide polarizer and polarization duplexer can be manufactured by milling technology as two single details, which makes the proposed engineering solution reliable, simple for simulation, development and application. Suggested new polarizer design was developed for the satellite operating Ka-band. It contains 12 irises, which are symmetrically located in the diagonal corners of a square waveguide. Obtained optimal polarization converter provides excellent matching and polarization performance. The maximum level of VSWR is less than 1.04 for both orthogonal polarizations. Values of cross-polarization discrimination are higher than 32 dB in the operating Ka-band. Developed square waveguide polarizer with diagonally located irises can be applied in modern wideband satellite antennas.

GLOBAL NAVIGATION SATELLITE SYSTEMS AND THEIR ROLE IN PRECISION AGRICULTURE TECHNOLOGIES

Today, global navigation satellite systems are being implemented in many structural units of the Ukrainian economic complex, many spheres of human activity, and every year they continue to develop. One of the main feature of these satellite systems is the requirements for high accuracy and speed of received data. They provide the opportunity to reduce operating costs and increase the efficiency of use of equipment and other resources. Therefore, the use of navigation satellite systems for controlling machine units, establishing their location, monitoring soil condition and yield mapping is becoming increasingly relevant today. The subject of study in this article were global navigation satellite systems NAVSTARGPS (USA), GLONASS (RF), GALILEO (EU), BEIDOU (China) and regional navigation systems NavIC (India) and QUASI-ZENITH (Japan). The purpose of the work was to clarify and establish the main characteristics of global navigation satellite systems and their role in the implementation of precision agriculture technologies. The task of the work was: to analyze the functional characteristics of global positioning satellite systems and their main elements; to find out principles of operation of systems: navigation, coordinates, time; to establish the accuracy of navigation systems; to substantiate the role of global positioning satellite systems in the effective implementation of precision agriculture technologies in agriculture. The research methodology was based on the method of materialistic dialectics, methods of analysis and synthesis of both information from official sources and information from the works of other researchers. Two major operators of satellite navigation systems the NAVSTAR GPS and GLONASS, which are similar in many respects, have been identified in the scientific work. Among the distinctive features there are the nature of the location, the motion of satellites in orbits and their total number, methods of encoding the CDMA and FDMA signals, the use of different coordinate systems WGS-84 and PZ90.11. As for the other two satellite navigation systems GALILEO and BEIDOU, they are developing rapidly with great ambition and potential. It is established that at the present time the accuracy of determining the coordinates of the GLONASS system is inferior to the performance of the American satellite navigation system GPS. GLONASS provides more accurate positioning in the northern latitudes and GPS in the middle. It is noted that the positioning accuracy of machine units for the implementation of precision farming technologies can be improved (from 2 to 20 cm) due to differential signal correction with the help of free and commercial wideband satellite navigation subsystems. These services will allow to implement the tasks of precision driving, and therefore, to ensure the accurate implementation of sowing material, fertilizers and herbicides to spare them, accurate inter-row cultivation of industrial crops, accurate harvesting, etc., when performing agro-technological operations using ground vehicles and landless vehicles.

Accurate hyperspectral and infrared satellite image registration method using structured topological constraints

As the hyperspectral and infrared characteristics of satellite images are different, the accurate registration between these two kinds of images is a challenge. Considering the robustness of scene structure, this paper proposes an accurate hyperspectral and infrared satellite image registration method using structured topological constraints. First, Delaunay triangulation is used to correlate the scattered feature points, and these local points are combined in a graph arrangement to form triangular mesh. And then, based on the correspondences between local points, triangular edges and triangular surfaces, the multi-level structured topological constraints are established to dynamically remove the outliers. Further, based on the established spatial topology, an image fitting method using multiple transformation models is proposed, which can solve the problem of local distortion of wide-band satellite images rapidly through region merging. Compared with the existing state-of-the-arts, the experimental results show that the proposed method has high registration accuracy, good robustness and fast computational speed for satellite images.

Efficient Wideband Spectrum Sensing with Maximal Spectral Efficiency for LEO Mobile Satellite Systems.

The usable satellite spectrum is becoming scarce due to static spectrum allocation policies. Cognitive radio approaches have already demonstrated their potential towards spectral efficiency for providing more spectrum access opportunities to secondary user (SU) with sufficient protection to licensed primary user (PU). Hence, recent scientific literature has been focused on the tradeoff between spectrum reuse and PU protection within narrowband spectrum sensing (SS) in terrestrial wireless sensing networks. However, those narrowband SS techniques investigated in the context of terrestrial CR may not be applicable for detecting wideband satellite signals. In this paper, we mainly investigate the problem of joint designing sensing time and hard fusion scheme to maximize SU spectral efficiency in the scenario of low earth orbit (LEO) mobile satellite services based on wideband spectrum sensing. Compressed detection model is established to prove that there indeed exists one optimal sensing time achieving maximal spectral efficiency. Moreover, we propose novel wideband cooperative spectrum sensing (CSS) framework where each SU reporting duration can be utilized for its following SU sensing. The sensing performance benefits from the novel CSS framework because the equivalent sensing time is extended by making full use of reporting slot. Furthermore, in respect of time-varying channel, the spatiotemporal CSS (ST-CSS) is presented to attain space and time diversity gain simultaneously under hard decision fusion rule. Computer simulations show that the optimal sensing settings algorithm of joint optimization of sensing time, hard fusion rule and scheduling strategy achieves significant improvement in spectral efficiency. Additionally, the novel ST-CSS scheme performs much higher spectral efficiency than that of general CSS framework.

Spatial Correlation Characteristics Analysis of Multi-Beam Channels of Mobile Satellite System

Due to the influence of scatterers around the receiving antenna, the multipath signal in satellite mobile communication systems is correlated with each other which would influence the system performance. There is no systematic standard on the channel modelling of the wideband satellite channel at present, so the study of the modelling of the wideband satellite channel is of great importance. In this paper, firstly we created a multi-beam model which can figure out the antenna gain of the nth component beam. Secondly, we combined the characteristics of multi-beam satellite channel and the distribution of the scatterers, and set up a three-dimension random channel model. This model is more realistic for satellite communication system since it considers the height of scatterers. According to the channel models, we had the formula of spatial correlation coefficient. We used the formula to calculate the relationship between spatial correlation coefficient and the interval of antennas. The result shows that the spatial correlation exists and cannot be ignored while modeling for mobile satellite system.

Study on the dual-orthogonal polarized MIMO wideband satellite mobile channel based on a 4-state LMS model

This paper focused on establishing a MIMO wideband land mobile satellite (LMS) channel statistics model. The particularity of this channel modeling was its wideband characteristics and the DPAs structure. Based on the Loo and Fontan model, a 4-state wideband LMS model was analyzed by combination of a Markov chain and properties of the wideband channel including its multipath excess delay and temporal-correlation performance. The paper also studied the effects of DPAs on channel modeling including the Cross Polarization Discrimination (XPD) and Cross Polarization Coupling (XPC). Through detailed analysis of the 4-state widebandLMSmodel and the effects of DPAs on channel modeling above, a typical dual-orthogonal polarized MIMO wideband satellite mobile channel model could be built. According to the modeling steps, channel time-series can be generated to assist further analysis of the system performance and evaluation of new technologies.

Analysis and Design of a Novel Coupled Shorting Strip for Compact Patch Antenna With Bandwidth Enhancement

As it is well known, the bandwidth of a patch antenna will decrease with the decrease of antenna size, no matter what size reduction technique is adopted. In this letter, a detailed research on the shorting load, which is a traditional and effective size reduction technique for patch antennas, is done with the help of a transmission line (TL) model of the patch antenna, and a novel design of a coupled shorting strip with bandwidth enhancement is proposed. Based on the research, a compact circularly polarized (CP) patch antenna loaded by the proposed shorting strip is designed for the application of E6 band of COMPASS Navigation System, which has a small electrical size of only λ/7 ×λ/7 ×λ/15 (λ is the wavelength in free space). The simulated and measured results show that the proposed antenna has good and stable performance over the whole operating band, which means that it is quite an ideal compact antenna used for wideband satellite navigation applications.

Multirate recovery scheme for wide-band global navigation satellite system signals

In this study, a multirate approach is proposed for the recovery of wide-band global navigation satellite system (GNSS) signals. Two or more narrow-band front-ends are used in parallel for collecting different portions of the spectrum of a wide-band GNSS signal that is then reconstructed from its sub-band components. Algorithms for compensating for phase offsets and amplitude imbalances have been developed and used to equalise possible differences among the recovered narrow-band components. Specific focus is given to the case where two front-ends are employed and live GNSS data from the Galileo in-orbit validation elements, GIOVE-A and GIOVE-B are used for demonstrating the effectiveness of the developed reconstruction algorithm.

Digital satellite receiver for wideband multi-rate Ka-band communications

This correspondence presents the architecture of a high-speed low-complexity digital receiver for wideband satellite communications supporting multiple baud rates, ranging from 10 to 200 MBaud. The design of the modem is based on the cascaded integrator-comb (CIC) scheme which exploits a parallel processing so as to provide an outstanding decimation agility. Eventually, bit error rate (BER) performance of the multi-rate receiver are assessed by floating-point simulations.

Deterministic wideband modeling of satellite propagation channel with buildings blockage

The article presents an example of satellite propagation modeling, applying the radio channel transfer function analysis as described and experimentally verified in scientific literature. The simulation of a satellite radio channel is executed by employing "ray tracing" and the uniform geometric theory of diffraction-based method for an assumed urban and suburban environment and different polarizations. Derived results regarding the channel transfer function are analyzed via a simulation of the wideband propagation measurement system and the Fourier transform procedures. It has been concluded that, contrary to ground cell radio system situations, where two-ray models usually suffice, a more detailed calculation should be considered for wideband satellite radio systems. Moreover, it is shown that the conclusions derived for the path loss and the delay spread depend not only on the specific propagation scenario, but also on the building permittivity.

Air traffic management

Several studies and demonstrations described in this report show the potential for existing satellite technology to support future ATM needs using a reasonable level of satellite communications resources. A prototype system tested by NASA performed well and demonstrated the feasibility of a wideband satellite link approach. System optimisation and the reduction of system and component costs through continued research and development must continue to enable the implementation of satellite communications for ATM by the time aviation traffic levels require it.

Closed-loop congestion control in a GEO satellite system

Congestion control is a key issue in broadband networks, which is particularly hard in a geostationary (GEO) satellite framework because of the long propagation delays, the limited satellite payload complexity and the scarce amount of capacity. This paper, partially supported by the WISDOM 1 1 WISDOM (WIdeband Satellite Demonstration Of Multimedia) is a European Union project in the framework of the 4th Framework ACTS (Advanced Communications, Technology and Services) programme. project, shows that the problem can be modelled as a closed-loop control system with two cascade controllers: the former on-board and the latter on-earth. The proposed novelties are (i) the application of control-theoretic methodologies to the congestion control in satellite networks, and (ii) the introduction of global control parameters that, even if they are not connection-specific, meet the control objectives.

Design and Implementation of 40-GHz-Band LNA MMICs with Super Low-Gain Flatness

This paper introduces the design and implementation of 40-GHz-band 4-stage/2-stage low-noise amplifier with low-gain flatness for wide-band wireless multimedia and satellite communication systems. The 40-GHz-band 4-stage MMIC demonstrate a small signal gain of more than 20 dB, an input return loss of 10.2 dB, and an output return loss of 21.8 dB for 40∼42 GHz. The gain flatness of the 40-GHz-band 4-stage LNA was 0.1 dB for 40∼42 GHz. The noise figure of the 40 GHz-band 4-stage LNA was simulated to be less than 3.2 dB for 40∼42 GHz. While the 40-GHz-band 2-stage LNA MMIC demonstrate a small signal gain of more than 10.5 dB, an input return loss of 8.6 dB, and an output return loss of 19.8 dB for 40∼42 GHz. The gain flatness of the 40-GHz-band 2-stage LNA was 0.4 dB for 40∼42 GHz. The noise figure of the 40-GHz-band 2-stage LNA was simulated to be less than 3.0 dB for 40∼42 GHz. The chip size of the 2-stage and the 4-stage LNA MMICs were 2.1×1.7 mm and 3.7×1.7 mm, respectively.

Application of filter sharpening to cascaded integrator-comb decimation filters

A new architecture for the implementation of high-order decimation filters is described. It combines the cascaded integrator-comb (CIC) multirate filter structure with filter sharpening techniques to improve the filter's passband response. This allows the first-stage CIC decimation filter to be followed by a fixed-coefficient second-stage filter, rather than a programmable filter, thereby achieving a significant hardware reduction over existing approaches. Furthermore, the use of fixed-coefficient filters in place of programmable-coefficient filters improves the overall throughput rate. The resulting architecture is well suited for single-chip VLSI implementation with very high data-sample rates. We discuss an example with specifications suitable for use in a wideband satellite communication subband tuner system and for signal analysis.

A vision of the second century of wireless communication

Just as the first century of wireless communication led to nearly universal radio broadcasting, so the second century is certain to provide ubiquitous two-way wireless connectivity by utilizing new digital spread spectrum multiple access technologies coupled with wideband network connectivity, using both terrestrial and satellite resources. The social implications of this rapid evolution can only be vaguely imagined.

Ionospheric scintillation-induced integration losses for space-based radar

An estimate of the impact of very severe ionospheric conditions on the coherent and noncoherent integration process from a two-way, transionospheric, propagation path is obtained for a specific type of frequency-diverse waveform. A bound on the total integration loss that would result from using this waveform during such ionospheric conditions is obtained through the analysis of data from the wideband satellite experiment. >