Tracking Antenna Research Articles

AirGuardian – UAV Hardware and Software System for Small Size UAVs

AirGuardian is a complex of an Unmanned Aerial Vehicle and ground station UAV hardware and software systems which has been developed at Obuda University. The hardware and software of the autopilot (AERObot), the antenna tracker station and the ground control station were simultaneously created resulting in the optimal cooperation of the modules. The aim of the research on AERObot – the special autopilot – was to create a generic autopilot which is capable of controlling different designs, weights and structures of airframes without any complex mathematical model recalculation.

Fade Mitigation for Air-to-Ground Communication in Aeronautical Telemetry

Telemetry links were comprised of a transmit antenna mounted on the underside of fuselage and a fixed ground station equipped with a tracking antenna. Air-to- ground channel for this telemetry link can be estimated as line of sight propagation. But there is link loss observed at ground control station for certain instant of time. Possible causes of link loss in this case are due to aircraft maneuvering and fading. So analysis of various fade mitigation techniques as well as bit error rate (BER) and signal to noise (SNR) ratio performance comparison between selection diversity, equal gain combining and maximal ratio combining scheme is done. Finally bit error rate performance comparison curve between maximal ratio scheme (MRC) and Alamouti dual antenna transmission scheme is plotted, in order to find out the best scheme for fade mitigation, among all the above mentioned schemes.

The Quiz for this Issue [Testing Ourselves

Five years! It's been five years since the “Testing Ourselves” column took off We started with the first quiz back in February 2007. We have had variety of quizzes and, including this issue, 29 tutorials since then. We have discussed simple but fundamental issues, such as the meaning of the numbers we use [1], models and modeling [2], EMC [3], the antenna as a transducer [4], transverse waves [5], reciprocity [6], reliability [7], high-frequency asymptotics [8], the use of the discrete Fourier transform [9] and digital multi-meters [10], calibration in electromagnetics (EM) [11–13], statistics in EM [14], and bio-electromagnetics [15]. We have designed a rooftop antenna tracker [16] and a green energy supply system [17]. We have presented some interesting applications of, e.g., chaos [18] and FDTD [19]. We have also introduced MATLAB-based virtual tools (see, e.g., MWFilterDesigner in [20] and WedgeGUI in this issue).

기어와 유연축을 갖는 구동계로 구동되는 OTM 안테나 시선의 안정화 제어

In this study, an OTM(on-the-move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite while moving was addressed. Since LOS(line-of-sight) of antenna should direct satellite consistently while vehicle moving to guarantee high satellite communication quality, active antenna LOS stabilization is a core technology for OTM antenna. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. In consideration of driving mechanism which consists of gear train and flexible driving shafts, a two-mass-system dynamic model coupled with vehicle motion was presented. An internal PI-control loop + outer PI-control loop structure has been suggested in order to damp the torsional vibration and stabilize control system. The classical pole-placement method was applied to design control gains. In addition, a vehicle motion compensation control beside of the feedback control loop has been suggested to improve LOS stabilization performances. The feasibility of the proposed control design was verified along with some experimental results.

Characterization of system calibration parameters for high gain dual polarization satellite beacon diagnostics of ionospheric variations

[1] We present complementary methods for calibrating the dual-polarization feed of a ground-based tracking antenna used for ionospheric measurements. Several calibration parameters are defined which describe the state of the measurement equipment. These key parameters then form a transformational Mueller matrix which may be used to remove system bias in data received from known beacons. Several strategies are developed to quantify these time-dependent distortions for the Green Bank 140′ diameter antenna and receiver, although these methods could be applied to other similar systems. One approach quantifies the receiver biases in terms of amplitude and gain differentials. This is accomplished by measuring polarimetric differences between channels using a test signal with a known amplitude and phase. Due to variations over time periods on the scale of a beacon track, this procedure is most effective when the calibration signal is injected concurrently with the beacon measurements. To determine antenna feed distortion, including cross-polarization and ellipticity, data is recorded from an external celestial source. An example shows the effectiveness of this calibration technique by comparing calibrated data to data without correction. Error estimates of the calibration parameters in the example establish an upper bound of 0.22 TEC units for measurements at 150 MHz along track.

Fixed ground stations for multi-satellite geostationary missions

Multi-satellite missions, such as the next generation of METEOSAT geostationary satellites, require a ground station able to support an arbitrary number of satellites that can fly wherever within a pre-determined sky region, called control box. The use of high frequencies, around 26 GHz, imposes on the ground station high antenna gains to compensate for the noise temperature collected at those frequencies to obtain the specified G/T. Regardless of the narrow beamwidths that emerged from the adoption of high antenna gains, it is also required to operate with fixed (i.e. without any kind of tracking) antennas. This paper shows how all these specifications drive a new type of ground station with respect to current solutions. The proposed architecture is based on a multi-reflector system able to provide a set of interleaved beams, which generates an almost uniform coverage of the control box. The architecture is analyzed and designed, optimizing all the main antenna parameters, and presenting the analytical results.

Analysis of the Signal Response of a Scanning-Beam Millimeter-Wave Correlation Radiometer

An analysis of the response of a scanning-beam millimeter-wave correlation radiometer is presented with an emphasis on the spectral signal response. The derivation and subsequent analysis presented here focuses specifically on the effects of the natural oscillation of the signal, called the fringe frequency, as it pertains to rotating sensors. The amplitude and bandwidth of the spectral density are analyzed in multiple cases, including for tracking and nontracking antennas, and for situations in which the antenna beam or the fringe washing function of the correlation radiometer is wide and can be neglected. Closed-form solutions are found for the case where the antennas track the source. Theoretical and simulated responses are given, and experimental results are compared to expected results from the theory for a correlation radiometer designed for security sensing. Measured experimental results show minimal deviation from theoretical calculations, validating the theoretical models derived herein.

GPS 속도와 가속도 기반의 칼만 필터를 이용한 무인항공기 추적 안테나 시스템의 시험

The UAV tracking antenna system based on GPS has a characteristic of update of position information which can occurs a position error. To reduce the position error, UAV tracking antenna system separates period of GPS update-rate and predicts the position of UAV using divided time points. These process improves the tracking performance of UAV. To predict the position of UAV by divided time points, we used a linear kalman filter based on the velocity and acceleration. Using this system, we measured velocity and acceleration according to the change of position. Finally, we can predict the change of position on divided time points.

Reliable Control of Ship-Mounted Satellite Tracking Antenna

Motorized antenna is a key element in overseas satellite telecommunication. The control system directs the on-board antenna toward a chosen satellite while the high sea waves disturb the antenna. Certain faults (communication system malfunction or signal blocking) cause interruption in the communication connection resulting in loss of the tracking functionality, and instability of the antenna. In this brief, a fault tolerant control (FTC) system is proposed for the satellite tracking antenna. The FTC system maintains the tracking functionality by employing proper control strategy. A robust fault diagnosis system is designed to supervise the FTC system. The employed fault diagnosis solution is able to estimate the faults for a class of nonlinear systems acting under external disturbances. Effectiveness of the method is verified through implementation and test on an antenna system.

小型飛行体へのマイクロ波無線給電システム

A microwave power beaming system was developed to realize wireless power supply to a Micro Aerial Vehicle. This system consists of transmitting, tracking, and receiving systems. In the transmitting system, a 5.8GHz microwave beam was irradiated from an active phased array antenna. Transmitting power was 4W and the beam divergence angle was 9deg. In the tracking system, a 2.45GHz pilot signal was detected by a two-dimensional tracking antenna and the position was deduced though the software retro-directive function. The maximum tracking error was 1.97deg in the azimuth direction and 1.79deg in the radial direction. In the receiving system, a light-weight flexible patch rectenna was developed using felt pad as substrate. The maximum rectenna efficiency of 45.3% was obtained with a 100Ω road at 63mW input power. By integrating these systems, auto-tracking wireless power supply was demonstrated to a MAV model circling at the altitude of 1,500mm. As a result, a motor was kept rotated. Received power was 24.3mW at maximum and 17.6mW on average and the total transmission efficiency was estimated at 0.60%.

Error Analysis of Orbit Determination for the Geostationary Satellite with Single Station Antenna Tracking Data

In the study, position and velocity values of a geostationary satellite are found. When performing this, a MATLAB algorithm is used for Runge-Kutta Fehlberg orbit integration method to solve spacecraft’s position and velocity. Integrated method is the solution for the systems which mainly work with a single station. Method provides calculation of azimuth, elevation and range data by using the position simulation results found by RKF. Errors of orbit determination are analysed. Variances of orbit parameters are chosen as the accuracy criteria. Analysis results are the indicator of the method’s accuracy

저궤도 위성용 TT&C 안테나의 설계

In this paper, we study a TT&C link to obtain a required specifications of TT&C(Telemetry Tracking and Command system) antenna for an LEO(Low Earth Orbit) satellite. The premised mission orbit is the sun-synchronized and circular orbit and it performs earth-space observations. We design minimum TT&C link-budget to obtain required antenna beamwidth and gain. The proposed turnstile antenna provides wide beamwidth and circular polarization. We suggested the attaching position that shows the most effective results by confirming the variation of antenna performance when the proposed antenna is adapted to satellite`s various positions. Also we proved the proposed antenna`s ability while it is performing the mission through the orbit simulation based on the electrical performance of the proposed turnstile antenna.

Microstrip Monopulse Feed for Parabolic Dish Tracking Antenna Used in a Radio Theodolite System

This paper presents the design and development of a tracking antenna for the application of radiosonde tracking in a radio theodolite system. A parabolic dish reflector antenna with a microstrip monopulse feed has been developed and tested with the system. An array of 2 x 2 microstrip patch antenna has been proposed as a feed for the reflector dish. The monopulse tracking is executed by generating sum and difference patterns in both azimuth and the elevation plane. The tracking antenna has been characterized in the open space at the installation site. The sum and difference pattern of the individual feed system and the same with the reflector have been measured and presented. The pattern shows the different angle discrimination capabilities due to their different gain associated with the individual system.

A Single-Channel Microstrip Electronic Tracking Antenna Array With Time Sequence Phase Weighting on Sub-Array

We have designed and tested a novel electronic tracking antenna array that is formed by 2 × 2 microstrip sub-arrays. Through time sequence phase weighting on each sub-array, the amplitude and phase on each sub-array can be recovered from the output of the resultant single channel. The amplitude and phase on each array can be used to produce the sum and difference radiation pattern by digital signal processing. In comparison with the monopulse system, the RF comparator is eliminated and the number of the receiver channels is reduced from 3 to 1. A proof-of-concept prototype was fabricated and tested. The measured results confirmed the validity and advantages of the proposed scheme. The procedure of channel correction is given.

Stabilization Control of line of sight of OTM(On-The-Move) Antenna

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.

Influence and correction method of atmosphere refraction on tracking antenna direction

Influence and correction method of atmosphere refraction on tracking antenna direction

A Rooftop Antenna Tracking System: Design, Simulation, and Implementation

A rooftop dish-antenna tracking system is designed. The power budget is given for the selection of appropriate motors and corresponding drives. A mathematical model of such a system is presented. The tracking system is realized practically with commercial PLC and display units. A Matlab-based tracking-system simulator is also developed.

Testing Ourselves

This month's quiz challenges readers to help design a kind of antenna tracking system.

Recent Korean R&D in Satellite Communications

The R&D in satellite communications in Korea has been driven mainly by KCC (Korea Communications Commission) but in a small scale compared to Korea space development program organized by MEST (Ministry of Education, Science and Technology). Public and civilian satcom sector R&D has been led mainly by ETRI with small/medium companies contrary to rare investment in private sector while military sector R&D has been orchestrated by ADD with defense industry. By the COMS (Communication, Ocean and Meteorological Satellite) experimental Ka-band payload, Korea pursues a space qualification of own technology for national infrastructure evolution as well as industrialization of space R&D results. Once COMS launched and space qualified in 2009, subsequent application experiments and new technology R&D like UHDTV will entail service and industry promotion. The payload technology is expected for the next Korean commercial satellites or for new OBP satellites. The COMS ground control system and GNSS ground station technologies are under development for COMS operation and enhanced GNSS services along with advent of Galileo respectively. Satellite broadband mobile VSAT based on DVB-S2/RCS (+M) and low profile tracking antennas have been developed for trains, ships, and planes. While APSI is developing GMR-1 based Thuraya handset functions, ETRI is designing IMT-Advanced satellite radio interface for satellite and terrestrial dual-mode handheld communication system like Japanese STICS, with universities' satellite OFDM researches. A 21 GHz Ka-band higher-availability scalable HD broadcasting technology and SkyLife's hybrid satellite IPTV technology are being developed. In near term Korea will extend R&D programs to upgrade the space communication infrastructure for universal access to digital opportunity and safer daily life from disaster, and to promote space green IT industrialization, national security, and space resources sovereign. Japanese stakeholders are invited to establish a collaborative R&D with Korea for mutual benefit of the future.

Orbit Determination Accuracy Improvement for Geostationary Satellite with Single Station Antenna Tracking Data

An operational orbit determination (OD) and prediction system for the geostationary Communication, Ocean, and Meteorological Satellite (COMS) mission requires accurate satellite positioning knowledge to accomplish image navigation registration on the ground. Ranging and tracking data from a single ground station is used for COMS OD in normal operation. However, the orbital longitude of the COMS is so close to that of satellite tracking sites that geometric singularity affects observability. A method to solve the azimuth bias of a single station in singularity is to periodically apply an estimated azimuth bias using the ranging and tracking data of two stations. Velocity increments of a wheel off-loading maneuver which is performed twice a day are fixed by planned values without considering maneuver efficiency during OD. Using only single-station data with the correction of the azimuth bias, OD can achieve three-sigma position accuracy on the order of 1.5 km root-sum-square.