Showing papers on "Ka band published in 1997"

Channel characterization and modeling for Ka-band very small aperture terminals

Abstract: An increasing number of commercial applications are being promoted for future Ka-band satellite communication systems. Many of these systems will involve low-margin very small aperture terminals (VSATs). These systems are subject to important atmospheric propagation degradations that affect the quality of transmission and the link availability. The objective of this paper is to characterize the Ka-band channel and evaluate the performance degradation in VSATs resulting from atmospheric propagation, impairments. In particular microwave propagation through a turbulent atmosphere is discussed, and the statistical characterization and modeling of tropospheric scintillation is reviewed. Moreover, the paper extends the method proposed by Filip and Vilar (1990) for the long-term characterization and modeling of the combined effect of rain impairments and scintillation. Specifically, the increase in noise temperature during rain events is added to the Filip-Vilar model. This leads to a five-parameter global fading distribution that is used to predict typical Ka-band satellite link outage time, the mathematical formalism is illustrated by applying the method to the selected case of the Advanced Communications Technology Satellite (ACTS)-Georgia Tech experimental downlink. Numerical results confirm that both rain impairments and scintillation are important factors in the design of Ka-band VSAT systems.

European research on Ka-band slant path propagation

Abstract: Europe saw two major initiatives in the mid-1980's to verify the viability of 20-50 GHz frequency bands for high capacity radio transmission. The first was the experimental telecommunication satellite OLYMPUS commissioned by the European Space Agency; the second was the ITALSAT program planned by the Italian Space Agency. Both spacecraft were equipped with highly stable propagation beacon payloads for accurate measurement of propagation conditions. Two international groups of experimenters (OPEX for OLYMPUS and CEPIT for ITALSAT), who had agreed on a set of common procedures for the earth stations' design, experiment management, and comparison of results, carried out the propagation measurements in a collaborative manner. This paper gives a summary of these activities and their results.

Ka-band propagation measurements: an opportunity with the Advanced Communications Technology Satellite (ACTS)

Abstract: The Advanced Communications Technology Satellite (ACTS) was conceived at the National Aeronautics and Space Administration (NASA) as a follow on program to its long history in satellite communications projects that have reduced the risk of developing new technologies that fall outside the sponsorship capability of the private sector. To counter the foreign challenge that developed in the late 1970's to the once insuperable US lead in this field, ACTS was developed to maintain the US preeminence. Launched in September 1993 from the space shuttle, key technologies on ACTS include a multibeam antenna, a baseband processor, a 900 MHz wideband microwave switch matrix, adaptive rain fade compensation techniques, and the use of Ka-band frequencies. Since this is the United States' first effort in using Ka-band for satellite communications, beacons are incorporated on the satellite, which provide an opportunity for propagation measurements. NASA is sponsoring a network of propagation experimenters using these beacons and receive-only terminals identical in design. This paper provides some history that leads to the eventual development of ACTS. Also, a system overview of the spacecraft is provided for those less familiar with it.

Application of open-loop uplink power control in Ka-band satellite links

Abstract: Propagation impairments impose a limit on the use of the 20/30-GHz frequency band for satellite communication applications. Power control is one of the techniques that can be used to mitigate such impairments. Results of an experiment conducted using the Advanced Communications Technology Satellite (ACTS) to evaluate the efficacy of open-loop uplink power control are presented. A power control system is required to maintain the power flux received at the satellite at a constant level irrespective of the fading along the propagation path. The control parameter for the power controller was derived from the fading and enhancements observed on a downlink beacon signal thus requiring frequency translation of the propagation effects to the uplink frequency. In this scheme, the controller performance is largely a function of the frequency translation accuracy, which is determined by the prevailing propagation conditions. In addition, equipment-induced variations in the control parameter can produce power control errors. To maintain the control accuracy within reasonable limits, an algorithm that can differentiate various propagation factors as well as equipment effects was devised. It was found that under most conditions, the power control accuracy could be maintained within /spl plusmn/2.5 dB.

Ka-Band ultra low noise MMIC amplifier using pseudomorphic HEMTs

Abstract: A Ka-band monolithic low noise two stage amplifier has been developed using an AlGaAs-InGaAs-GaAs pseudomorphic HEMTs with a gate length of 0.15 /spl mu/m. For a superior noise figure, the MMIC was optimized by inserting a low loss resonator type stabilizing circuit without sacrificing the gain performance. The amplifier has achieved a 1.0 dB noise figure with an associated gain of 18.0 dB at 32 GHz. These results are the best of AlGaAs-InGaAs-GaAs P-HEMT MMICs ever reported to date.

System requirements for Ka-band Earth-satellite propagation data

Abstract: Accurate estimates of the propagation impairments that affect link quality and availability and determine signal interference fields are essential for the reliable design of telecommunication systems and the efficient use of the electromagnetic spectrum. Recent announcements by commercial entities of their intent to use Ka-band spectrum to supply satellite services have heightened interest in propagation data and models for these frequencies. This paper provides a brief overview of Ka-band Earth-satellite systems and requirements in relation to the need for specific types of propagation data.

Rain Fade Compensation Alternatives for Ka Band Communication Satellites

Abstract: Future satellite communications systems operating in Ka-band frequency band are subject to degradation produced by the troposphere which is much more severe than those found at lower frequency bands. These impairments include signal absorption by rain, clouds and gases, and amplitude scintillation's arising from refractive index irregularities. For example, rain attenuation at 20 GHz is almost three times that at 11 GHz. Although some of these impairments can be overcome by oversizing the ground station antennas and high power amplifiers, the current trend is using small (less than 20 inches apertures), low-cost ground stations (less than $1000) that can be easily deployed at user premises. As a consequence, most Ka-band systems are expected to employ different forms of fade mitigation that can be implemented relatively easily and at modest cost. The rain fade mitigation approaches are defined by three types of Ka-band communications systems - a low service rate (less than 1.5 Mb/s), a moderate service rate (1.5 to 6 Mb/s) system and a high service rate (greater than 43 Mb/s) system. The ACTS VSAT network, which includes an adaptive rain fade technique, is an example of a moderate service rate.

Solar Scintillation Effects on Telecommunication Links at Ka-Band and X-Band

Abstract: Many deep-space missions encounter solar conjunction Some missions, such as Solar Probe and Stardust, encounter solar conjunction during their main missions The Sun–Earth–Probe (SEP) angle is used to describe the degree of conjunction When the SEP angle is small, the solar plasma causes degradation in telecommunication link performance In this article, we present a model that we developed to study the amplitude scintillation effects on telemetry signals at both 84 GHz (X-band) and 32 GHz (Ka-band) Both analytical and simulated results show that, at a low bit-error rate (<10−5), X-band links suffer degradation of 82 dB for the Solar Probe mission at perihelion Ka-band links, however, suffer only a few tenths of a dB In addition to this 8-dB Ka-band advantage over X-band under scintillation conditions, there is also the 4to 6-dB Ka-band advantage due to higher frequency

Low phase noise Ka-band VCOs using InGaP/GaAs HBTs and coplanar waveguide

Abstract: Ka-band voltage controlled oscillators (VCOs) have been designed using InGaP/GaAs HBT technology. The best measured VCO shows a phase noise of -95 dBc/Hz at 100 kHz offset and -112 dBc/Hz at 1 MHz offset, delivering 5.3 dBm output power at 40.8 GHz. Variations of circuit topology and resonator type were fabricated to evaluate their contribution to phase noise and tuning range.

Dynamic response of long optical-cavity laser diode for Ka-band communication satellites

Abstract: This paper presents the performance of a novel Fabry-Perot (FP) laser diode. The laser is composed of a long gain section, and a multiple-quantum-well (MQW) electroabsorption (E/A) modulator. The laser diode is mode locked using the integrated E/A modulator at 19.3 GHz. Sub-carrier data signals at S-band and a frequency reference of 19.3 GHz are simultaneously distributed using modulation of the gain and E/A sections of the laser, respectively. This paper also compares performance of this laser diode at various operation points in terms of pulsewidth, pulse-to-pulse coherency, phase-noise degradation of the frequency reference, and two-tone spurious-free dynamic range. Implication of this laser's performance as an optical transmitter is also evaluated for a fiber-optic (FO) distribution network in Ka-band phased-array antennas for satellite communications.

K- and Ka-band waveguide microcalorimeters for microwave power standards

Abstract: Three sets of waveguide microcalorimeters of K- and Ka-band are described. Included are construction details of the microcalorimeters, operation procedure, and uncertainty analysis. The results of measurements and intercomparisons are presented. The uncertainty analysis shows a total uncertainty including systematic uncertainty and random uncertainty of 0.53-0.68%.

Input stage for police radar detector including input signal preamplification

Abstract: An input stage for a police radar detector includes a single mixer together with at least one preamplifier to detect radar signals in the X, K and Ka bands. A preamplifier may be used on the X band alone, the K band alone, the Ka band alone, the X and K bands or the X, K and Ka bands. The use of these preamplifiers provides better noise figure; however, multiple responses cannot be scanned at the same time in bands utilizing a preamplifier with sufficient selectivity to reduce noise in its respective image bands to tolerable levels so that some or all of the receiver responses are swept independently with the preamplifier or preamplifiers being enabled one at a time as appropriate for each band being scanned. Since more sweep time is required when multiple responses are no longer swept simultaneously, a currently preferred form of the input stage couples the Ka band signals to a single mixer through a preamplifier which permits multiple responses to be swept in the Ka band, or passively for economy, to receive dual responses in the Ka band. Utilizing a novel frequency scheme for a radar detector yields two responses approximately 1.3 Ghz apart that fall within the Ka band so that the Ka band can be swept by tuning the first LO 124 through a 1.3 Ghz range with the two responses covering the 2.6 Ghz required for sweeping the entire Ka band.

Low cost compact electronically scanned millimeter wave lens and method

Abstract: A low cost, compact, electronically scanned millimeter wave (MMW) lens enables the projection of a highly directional beam of Ka band millimeter wave (MMW) electromagnetic energy, while eliminating the need for mechanical movement of the lens. The present invention allows for the economical production and operation of the lens in the Ka and higher frequency ranges by exploiting waveguide technology. The waveguides of the present invention are tapered longitudinally resulting in a wider portion of the waveguide in electromagnetic communication with an interior cavity of the lens. The waveguide taper improves impedance matching between the waveguides and the lens cavity. The waveguides also include symmetric power dividers, located longitudinally within the waveguide aperture, ensuring port widths below λ g /2, thus, reducing or eliminating unwanted mode components which reduces sidelobe energy. This results in a low loss, low sidelobe steerable beam of MMW energy.

The application of S-band polarimetric radar measurements to Ka-band attenuation prediction

Abstract: In September 1993, the National Aeronautics and Space Administration's Advanced Communications Technology Satellite (ACTS) was deployed into a geostationary orbit near 100/spl deg/ W longitude. The ACTS satellite employs two Ka-band beacons, one at 20.185 GHz and another at 27.505 GHz. Impairments due to rain attenuation and tropospheric scintillations will significantly affect new technologies for this spectrum. Heavy rain at Ka-band can easily produce 30 dB of attenuation along the propagation path. Propagation experiments being conducted in seven different climatic zones involve multiyear attenuation measurements along the satellite-Earth slant path. Measurements in the B2 climatic zone are made with an ACTS propagation terminal located in northeast Colorado. In order to gain move understanding about the physical processes that are responsible for Ka-band attenuation, the Colorado State University CHILL S-band polarimetric radar is used to take radar measurements along the slant path. The Colorado Front Range experiences a variety of weather conditions throughout the year ranging from upslope rain conditions to winter storms. Four such events measured along the slant path are illustrated in this paper. They include two convective cases and two "bright-band" cases. The S-band polarimetric radar data is used to initialize radar-based attenuation-prediction models, which are applied to the four precipitation events described. The comparisons of predicted attenuation to measured attenuation are quite good. It was also found during the course of the experiment that water droplets standing on the antenna surface can cause appreciable attenuation at Ka-band frequencies. That finding needs to be recognized in future model development and statistical analysis.

Antenna system for multi-band satellite communications

Abstract: Multi-band satellite communications antennas have applications in the commercial, defense, and civilian federal marketplace. All defence agencies have requirements for transportable multi-band systems. There are many civilian federal organizations requiring multi-band capabilities, and the commercial market uses C- and Ku-band systems, with future requirements for Ka-band coverage. The latest Intelsat satellites carry both C- and Ku-band transponders, therefore, many of the world's earth stations are, or will be, operating in both bands. The use of an antenna permitting operation of the earth terminal in all three bands without requiring the replacement of the feed is a highly desirable capability. This paper describes the design, development, and testing of an antenna system that permits operation in the three main frequency bands, (C, X, and Ku), including simultaneous operation in multiple bands. This antenna system operates in all three bands without the need to replace any components. The paper also discusses the possibilities of extending the frequency coverage of the antenna system into the Ka-band. The multi-band antenna system can increase the capabilities and operational flexibility of existing earth stations as well as new systems.

Police radar detector including nuisance alert suppression

Abstract: A radar detector suppresses nuisance alerts due to detection of a third harmonic of a common LO signal of other radar detectors by detecting a second harmonic of the offending LO signal. If a detected radar signal in the Ka band is of a frequency within a suspect range corresponding to possible third harmonic spurious LO signals, a determination is made as to whether a potential alert blocking signal around the second harmonic of a nominal 11.55 Ghz signal is also present. In the illustrated embodiment, the second harmonic alert blocking signal which is checked has a frequency which is 2/3 the frequency of the detected Ka signal ± a guard band of, for example ±40 Mhz, and is within a range of frequencies from about 22.813 Ghz to about 23.8 Ghz. If no blocking signal has been detected within about 10 seconds before or within three sweeps after detection of the Ka band signal in the suspect range, the detected Ka band signal is reported. If a blocking signal is detected, the signal strength of the detected Ka band signal is examined relative to the signal strength of the blocking signal. If the Ka band signal strength is greater than a reporting threshold and also is greater than the signal strength of the blocking signal by a minimum threshold, the detected Ka band signal is reported. Otherwise the detected Ka band signal is treated as a nuisance signal generated by a nearby radar detector and suppressed.

A high-gain circularly polarized Ka-band microstrip reflect array

Abstract: A half-meter, 32 GHz, circularly polarized microstrip reflectarray antenna has been developed. Excellent efficiency, good bandwidth, and low average sideglobe and cross-pol levels are achieved. It is believed that this is electrically the largest microstrip reflectarray (6924 elements) that has ever been developed, and it is the first time that circular polarization has been demonstrated using microstrip elements.

A novel monolithic HEMT-HBT Ka-band VCO-mixer design

Abstract: Here we present a novel demonstration of a HEMT-HBT VCO-mixer which utilizes a unique active topology and is the first Ka-band MMIC demonstrated using GaAs HEMT-HBT IC technology. The MMIC integrates a novel HEMT-HBT cascode active mixer topology which operates similar to a dual-gate mixer. An all active HEMT-HBT VCO is constructed from the HBT of the cascode by providing a HEMT tunable active inductor-resonator. The VCO can be tuned from 28.5 to 29.3 GHz while providing /spl ap/0 dBm of output power. Operated as an upconverter, the HEMT-HBT VCO-mixer achieves 6-9 dB conversion-loss over a 31 to 39 GHz output frequency band. The compact MMIC is 1.44/spl times/0.76 mm/sup 2/ in area due to the use of novel active circuit topologies and relies on minimal use of passive matching. The novel miniature active RF IC techniques demonstrated here have direct implications for future high complexity HEMT-HBT millimeter-wave MMICs.

Ka-Band Atmospheric Noise-Temperature Measurements at Goldstone, California, Using a 34-Meter Beam-Waveguide Antenna

Abstract: (View graphs) NASA's Deep space missions have used 960 MHz, 2.3 GHz, and 8.4 GHz for spacecraft communications dowlinks. Ka-band (32 GHz) is being considered as a downlink frequency for future flight projects.

Performance of a Ka-band transponder breadboard for deep space applications

Abstract: This article summarizes the design concepts and implementation of an advanced Ka-band (34.4 GHz/32 GHz) transponder breadboard for the next generation of space communications systems applications. The selected architecture upgrades the X-band (7.2 GHz/8.4 GHz) deep space transponder (DST) to provide Ka-band up/Ka- and X-band down capability. In addition, it can also be configured to provide X-band up/Ka- and X-band down. The Ka-band Transponder breadboard incorporates state-of-the-art components including sampling mixers, Ka-band dielectric resonator oscillator, and microwave monolithic integrated circuits (MMICs). The MMICs that were tested in the breadboard include upconverters, downconverters, automatic gain control circuits, mixers, phase modulators, and amplifiers. The measured receiver dynamic range, tracking range, acquisition rate, static phase error, and phase jitter characteristics of the Ka-band breadboard interfaced to the advanced engineering model X-band DST are in good agreement with the expected performance. The results show a receiver tracking threshold of -149 dBm with a dynamic range of 80 dB, and a downlink phase jitter of 7/spl deg/ rms. The analytical results of phase noise and Allan standard deviation are in good agreement with the experimental results.

The Status of Ka-Band Communications for Future Deep Space Missions

Abstract: Over the past decade, the Jet Propulsion Laboratory's Telecommunications and Mission Operations Directorate has invested in a variety of technologies, targeted at both the flight and ground sides of the communications link, with the goal of developing a Ka-band (32 GHz) communications capability for future deep space missions.

System implications of rain and ice depolarisation in Ka-band satellite communications

Abstract: This paper investigates the impact of rain and ice depolarisation on the performance of satellite communications systems operating in the Ka-band with orthogonal polarisations. Various prediction methods for evaluating the degradation of dual-polarised system availability due to rain and ice are reviewed. Their results are compared using depolarisation data and statistics collected in Belgium at 20 GHz during the ESA's Olympus satellite experiment and exhibit significant discrepancies. A procedure based on the combined use of experimental data and of a simulation software for communications systems confirms the prediction produced by one method. The proposed procedure also yields estimation of system quality during particular depolarisation events.

Rain Fade Compensation for Ka-Band Communications Satellites

Abstract: This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.

Performance Optimization of Ka-Band MMIC Power Amplifier Using On-Wafer Pulsed Power Test

Abstract: A novel technique has been developed to optimize the power MMIC performance by using on-wafer pulsed power test. Traditionally, only dc parameters were used to determine the chip operating bias condition. The on-wafer test was used to determine the functionality of the device, and the MMIC chip performance is optimized through manual bias tuning at module level. This technique provides significant cost savings in high volume production environment.

Initial test and evaluation of the millimeter-wave holographic surveillance system

Abstract: A test and evaluation pilot study was conducted in January 1996 at Sea-Tac International Airport in Seattle, Washington to determine the initial effectiveness of the Millimeter- wave Holographic Weapons Surveillance System. This is a new personnel surveillance systems for the detection of concealed metal, plastic, and ceramic weapons and other threatening materials. Two different frequency bands were used in the study: Ku band and Ka band. Over 7000 Millimeter-wave (MM-wave) holographic images were obtained on 21 different models. The 7000 images were used to produce simulated real-time surveillance system videos. The videos were constructed by obtaining 36 images of the models at 10 degree increments for 360 degree coverage. A library of two hundred videos were produced for this pilot study: 100 at Ku band and 100 at Ka band. The videos contained either a threat or no threat. The threats were concealed at different locations on the models. Various innocuous items and different clothing combinations were also used n the construction of these videos. Twenty-nine certified Sea-Tac screeners were used in the initial test and evaluation of this new surveillance technology. Each screener viewed 160 MM-wave videos: 80 Ku band and 80 Ka band. The ratio of non- threat to threat videos per band was three to one. Test and evaluation software was developed to collect data from the screeners on-line for the type and location of threat detected. The primary measures of screener performance used to evaluate this new technology included, the probability of detection, the probability of a false alarm, measures of screener sensitivity and bias, and threat detection time.

Interim Findings of ACTS Ka-Band Propagation Campaign

Abstract: The ACTS propagation campaign is focusing on two broad areas: 1) Rain/signal attenuation data collection at seven sites in North America, 2) Theoretical and empirical consideratons for a global model to predict first & second order temporal and spatial statistics on attenuation, scintillation, conherence bandwidth, and depolarization due to weather (precipitation and atmospheric including interaction of weather with the antenna) for satellite systems at Ka-band.

MMIC based SOM in optically fed phased array antennas for Ka-band communication satellites

Abstract: Experimental results are presented for an optically fed MMIC based self-oscillating mixer (SOM) at 19 GHz. A frequency reference, used to subharmonically synchronize the 19 GHz VCO, and FM data signals are optically distributed to generate RF signals for Ka-band communication satellites.