Band Transponder Research Articles

Preface to the special issue on the Alphasat Aldo Paraboni propagation experiment

Preface to the special issue on the Alphasat Aldo Paraboni propagation experiment

CUTIE: A cubesats tether-inserted mission for moon exploration

This paper presents the concept of a dual cubesat mission designed for Moon exploration that enables scientific measurements that are not accessible by high orbital or landed missions thanks to the use of a long passive tether for orbital insertion. Due to the intrinsic characteristic of the Moon environment, low altitude orbiting spacecrafts are in fact requested for mapping key parameters such as plasma, volatiles and magnetic field. Inserting a satellite in such low trajectories from an orbiter has usually a high cost of propellant to achieve the orbit change or requires a long time to finalize the maneuver with electrical propulsive systems. Limitations are even higher for cubesats that have very limited capacity for orbital adjustment, so they cannot perform substantial orbital changes by using classical propulsive techniques. The use of a long passive tether to exchange momentum between two cubesats can eliminate such drawbacks and provide fast, far-reaching and accurate orbital changes with almost no propellant being consumed. A mission scenario is presented with the two mated cubesats released by an orbiter in circular Moon orbit at 500 km altitude. Thanks to the momentum exchanges provided by the swinging tether the upper cubesat will be left in a 520 × 737 km orbit and the lower cubesat into a 460 × 26 km orbit with a low periselenium that provides an ideal altitude for close observation of the lunar surface and monitoring of characteristic parameters of the Moon environment. With a high-inclination orbit, the low-altitude orbital passes will map the entire Moon surface in around 14 days. The upper cubesat will be transferred on a highly predictable and low-perturbation orbit and equipped with laser corner reflectors and a radio link band transponder to allow tracking both from laser stations on Earth (Matera, Italy ASI geodesy station) and from the Lunar Orbiter via radio link. The integrated analysis with radio signals between Cubesats can also be used to improve orbit determination and study perturbation effects on orbital dynamics.

HF/UHF dual band RFID transponders for an information-driven public transportation system

The limited communication range of HF radio frequency identification (RFID) smart cards does not allow to automatically assess the alighting point of passengers on public transportation. This work considers HF/UHF dual band RFID transponders for electronic ticketing in an information-driven public transportation system. The UHF RFID interface is intended to enable a remote detection of passengers inside a vehicle and thus to assess the alighting point of passengers. A review of the specific operating conditions for the UHF RFID link is given and associated privacy issues are addressed. We introduce a low-complexity approach to safeguard the privacy of passengers. Following a discussion of the architecture of appropriate HF/UHF dual band transponder ICs, the focus is set on questions of the circuit implementation. With regard to the progressing CMOS technology scaling, we can observe potential risks of overvoltage stress for the UHF RFID front-end at high input powers. Two RF voltage limiters that prevent overvoltages are presented. Experimental results of circuit prototypes in a 40 nm CMOS technology demonstrate the functionality of two UHF RFID front-ends that incorporate the RF voltage limiters.

Implementing polarization shift keying over satellite - system design and measurement results

Summary Polarization shift keying (PolSK) is a digital modulation technique using the state of polarization of an electromagnetic wave as the signalling quantity. PolSK comes from fibre communications, where the channel offers two orthogonal states of polarization. This article develops on the idea to adapt this technology to satellite communications, where similar channel conditions exist. For this purpose, a digital PolSK modem was implemented on a programmable logic board. A proposal for constellation design as well as thoughts on synchronization of PolSK over satellite is presented. The modem was used to demonstrate a 16-state Polarization Shift Keying link over a commercial satellite in Ku band. Measurements have been conducted in a back-to-back setup on intermediate frequency and on a Ku band transponder simulator to assess the impact of path-length differences, carrier recovery and non-linearity. Copyright © 2015 John Wiley & Sons, Ltd.

Diurnal Effects on Satellite Network Performance Measured In Tropical Region

The performance and availability of Ku band satellite Broadband and DTH services are affected by rain fade.. Direct -to-home very Small aperture terminal system operating at frequencies above 10 GHz in tropical climate are subjected to many fade occurrences due to heavy rain. This paper presents diurnal varation on the performance of DTH (Direct to home) broadcasting service for the month of February. Keyword: DTH service, diurnal variation, quality of service, rain attenuation, I. Introduction In the design of Ku band satellite links such as direct to home very small aperture terminals (DTH/VSAT) systems, detailed propagation information must be needed to provides better performance, availability, and quality of service (1).These Ku band services are affected by outages for time-critical transmission such as real-time news and sports broadcasting. The DTH yearly availabilities is of 99.5% so the corresponding outage of 0.5% is equivalent to 44 hours per Year. These 44 hours of outage are not usually distributed evenly but are more likely to occur at certain times of the day and are quite often concentrated within a particular season. Such variations will affect customers' services. The probable duration of rain at a given level, effect of weather conditions on the performance of service, what time of the day it is highly affect the service these are the important aspect that will contribute to improve availability of DTH service which leads improve customers satisfaction.(2) II. DTH BROADCASTING SERVICES DTH network consist of broadcasting center, satellites, encoders, multiplexers, modulators and DTH receivers. A DTH service provider has to lease Ku band transponder from the satellite. The encoder converts the audio, video and data signal into the digital format and the multiplexer mixes these signals. AT the user end, there will be small dish and set top box to decode and viewed numerous channels (3)

Dual band RFID transponder antenna designed for a specific chip without addtional impedance matching network

AbstractA simple and novel antenna for dual band transponders in RFID application is introduced. The antenna is designed for directly matching a commercial chip without additional impedance matching network. The simulated and measured results of the proposed antenna show that the transponders integrated with this antenna will be able to comply with the ETSI Air Interface standard in UHF band and ISO 18000‐4 Air Interface Standard in microwave band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 58–60, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22994

A FERROELECTRIC BASED PASSIVE RFID TAG FOR UHF (860–960 MHz) BAND

ABSTRACT For a longer working distance between passive tags and the reader, the ferroelectric based technologies are proposed in UHF (860–960 MHz) band transponder. The small ferroelectric capacitor layout area with a stacked capacitor structure over circuit region and a large dielectric permittivity of 250 to 500 and small 1T1C cell array layout area with simple 2T2C based reference scheme allow small chip size. The low operation voltage of 1.5 V to 2.0 V without high voltage boosting scheme also contribute to small power consumption and low cost.

SMART-1: Development and lessons learnt

SMART-1 is the first of the small missions for advanced research and technology as part of ESA's science programme “Cosmic vision”. It was successfully launched on September 27, 2003 and is presently traveling towards its destination, the Moon. The main objective of the mission, to demonstrate solar electric primary propulsion for future Cornerstones (such as Bepi-Colombo), has already been achieved. At the time of writing the electric propulsion system has been working already for more than 3400 h and has provided a Delta-V to the spacecraft of more than 2500 m/s. The other technology objectives are also being fulfilled by the verification of the proper functioning of such on-board experiments like the X-Ka band transponder, the X-ray spectrometer, the near IR spectrometer, the laser link, etc. The scientific objectives are related to lunar science and will be fulfilled once the spacecraft enters its operational lunar orbit, currently expected for January 2005. SMART-1 lunar science investigations will include studies of the chemical composition of the Moon, of geophysical processes, environment and high-resolution studies in preparation for future steps of lunar exploration. SMART-1 has been an innovative mission in many aspects and we are now drawing some preliminary conclusions about the lessons to be learnt. The paper describes the spacecraft and the technology elements with particular emphasis to the technology nature of the mission. The on-board avionics employs many novel designs for spacecraft, including a serial CAN bus for data communication, autonomous star trackers and extensive use of auto-code generation for implementing the attitude control system and the failure, detection, isolation and recovery (FDIR). Finally, the orbital operation phase currently ongoing, including the routine electric propulsion operations and the instrument commissioning, is providing a wealth of data and lesson-learnt useful for future autonomous planetary missions.

Stardust: Comet and interstellar dust sample return mission

Stardust, the 4th Discovery mission launched in February 1999, will collect coma samples from the recently deflected comet 81P/Wild 2 on 2 January 2004 and return them to Earth on 15 January 2006 for detailed laboratory analyses. Stardust will be the first mission to bring samples back to Earth from a known comet and also the first to bring back contemporary interstellar particles recently discovered. These samples should provide important insights into the nature and amount of dust released by comets, the roles of comets in planetary systems, clues to the importance of comets in producing dust in our zodiacal cloud as well as circumstellar dust around other stars, and the links between collected meteoritic samples with a known cometary body. Samples are collected in newly invented continuous gradient density silica aerogel. Stardust is facilitated by a magnificent trajectory designed to accomplish a complex and ambitious flyby sample return mission within the Discovery program restrictions. The remaining science payload, which provides important context for the captured samples, includes a time‐of‐flight spectrometer measuring the chemical and isotopic composition of dust grains; a polyvinylidene fluoride dust flux monitor determining dust flux profiles; a CCD camera for imaging Wild 2 coma and its nucleus; a shared X band transponder providing two‐way Doppler shifts to estimate limits to Wild 2 mass and integrated dust fluence; and tracking of the spacecraft's attitude sensing for the detection of large particle impacts. The graphite composite spacecraft brings the collected sample back to Earth by a direct reentry in a capsule.

Near‐Earth Asteroid Rendezvous: Mission overview

The Near‐Earth Asteroid Rendezvous (NEAR) mission, the first launch of NASA's Discovery Program, will be the first mission to orbit an asteroid. NEAR will make the first comprehensive scientific measurements of an asteroid's surface composition, geology, physical properties, and internal structure. NEAR launched successfully on February 17, 1996, aboard a Delta 11–7925. It will orbit the 20‐km‐diameter near‐Earth asteroid 433 Eros for about 1 year, at a minimum orbit radius of about 35 km from the center of the asteroid. The NEAR is a solar‐powered, three‐axis stabilized spacecraft with a launch mass including propellant of 805 kg. NEAR uses X band telemetry to the NASA Deep Space Network, with the data rates at Eros up to 8.8 kbits/s using a 34‐m High EFficiency (HEF) dish, and up to 26.5 kbits/s using a 70‐m dish. A solid‐state recorder is accommodated with a memory capacity of 1.8 Gbytes. Attitude control is to 1.7 mrad, line‐of‐sight pointing stability is within 50 μrad over 1 s, and post processing attitude knowledge is within 50 μrad. NEAR accommodates 56 kg of instruments and provides them with 84 W. The instruments are a multispectral imager (MSI), a near‐infrared spectrograph (NIS), an X ray/gamma ray spectrometer (XRS/GRS), a magnetometer (MAG), and a laser rangefinder (NLR), while a radio science (RS) investigation uses the coherent X band transponder. NEAR will make a flyby of the C‐type asteroid 253 Mathilde in June 1997 and will rendezvous with 433 Eros in February 1999. It will execute an initial slow flyby of Eros, with a flyby speed of 5 m/s and a closest approach distance of 500 km. Subsequently, its orbit will be lowered to 35 km. The NEAR Mission Operations Center and the Science Data Center are at the Johns Hopkins Applied Physics Laboratory. The Science Data Center will maintain the entire NEAR data set on‐line, and data from all instruments can be accessed by every member of the NEAR Science Team. Data, including images, are released over the Internet as soon as they are validated.

The Future of Radar Beacons

The principles of radar beacons (racons) are described and their significance for navigation discussed. Developments in radars which may affect the operation of racons are considered and ways of meeting the requirement to locate and identify aids to navigation on a radar display are considered. The developments in non-radar band transponders are reviewed to determine whether they might present an alternative to racons in the future.

Development of HDTV digital transmission system through satellite

A HDTV digital transmission system through satellite has been developed. This system has been designed to utilize QPSK modulation via a 36 MHz bandwidth Ku band transponder. Convolutional code and Reed-Solomon code are applied for the purpose of error protection. The system provides the transmission rate of 40 Mbps for video. A HDTV codec has been fabricated for the system. A transmission experiment has been carried out and gave excellent transmission performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

3-GHz band burst mode earth station transmitter

To reduce the size and the cost of the earth station equipment for satellite communication, a 30-GHz band burst mode earth station transmitter is developed. In this case, the transmitter can access seven 30/20-GHz band transponders on the CS-3 transponder hopping system. Wideband and high-power characteristics are required for the transmitter with the transponder hopping system. For this purpose, a helix-type traveling-wave tube (TWT) transmitter is newly developed to replace the conventional klystron tube, realizing wideband characteristics. The anode voltage switching method is developed and used for the transmitter so that the output of the 30-GHz band helix TWT is increased. The anode voltage of TWT is made ON/OFF (burst mode) in accordance with a time-advanced control signal from TDM A equipment to satisfy the thermal condition for the helix slow-wave circuit and to reduce the power consumption. The major performances are as follows. The output power of 150 W is achieved by combining two tubes under the duty 50 percent or less and the power variation at 150 W is 1 dB/1 GHz or less. The rise and fall time of anode voltage is less than 3 μs.

30/20 GHz Band SCPC Satellite Communication Using Small Earth Stations

This paper presents a domestic satellite communication system accommodating numerous 30/20 GHz band small earth stations emphasizing the system outline, the use of multiple-access (MA) techniques. It also describes associated earth station configurations, equipment performance, and experimental results using the Japanese CS (medium capacity communications satellite for experimental purposes). Two kinds of earth stations are employed in this system, a small earth terminal (SET) and a master earth station (MES). The SET, which has an antenna about 2 m in diameter, is placed near a subscriber. The MES, which has an 11.5 m diameter antenna, is connected to the terrestrial telephone network through a satellite telephone switching center (STC). There are about 50 two-way channels with bit rates of 32 kbits/s which are achieved through the use of a 30/20 GHz band transponder whose EIRP is about 71.5 dBm, a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G/T</tex> of about 2.7 dB/K and an SET's antenna diameter of 1.8 m. This results in a system availability of 99.5 percent under typical Japanese statistical rain attenuation data. To enable a demand-assigned MA technique to be employed in this system, a single channel per carrier (SCPC) is selected, taking into consideration power efficiency of the SET, flexibility of system configurations, and the adaptability of the adaptive power control during rainy periods.

Experimental Program and Performance of Japan's Communication Satellite (CS) and Its First Results

Japan's CS spacecraft was launched successfully in December 1977 and placed at 135°E longitude in a geostationary orbit. On-orbit performance of the satellite was verified quite well with the exception of two sets of K -band transponders. Substantial communication experiments have been conducted for more than half a year starting in May, 1978. In the satellite loop-back configuration at the Main Fixed Earth Station, 1872 and 972 channels of FDM-FM telephony signals can be transmitted through any K - and C -band transponder, respectively, with signal quality better than 50 dB in S/(N + D) . The quality of FM-TV signals is also good (more than 59 dB in unweighted S/N at K -band). Basic transmission characteristics of PCM-PSK signals with various modulation parameters were measured with good results. However, it became clear that spin modulation effects must be considered for estimating the BER performances, especially at K -band. DPCM-TV signal transmission tests were also conducted with satisfactory results. PCM-TDMA systems were verified to work well at K -band, including functions such as frame and burst synchronization, initial acquisition and so forth. Diversity switching functions will be tested in a later experimental phase. In propagation experiments, rainfall attenuation, excess noise temperature due to rain, and effects of the ionosphere have been studied. Although insufficient data have been accumulated, some estimation of the necessary link margin against the rainfall attenuation at K -band was obtained. In general, confidence has been attained that some CS-like system with K -band links will be suitable for practical use. The experiments are now being conducted and will continue through the nominal mission period of 3 years.