Communication is one of the most essential activities of mankind and there is no doubt that satellite communications have made a tremendous stride in this matter. The goal has been to create uninterrupted, seamless, high throughput connectivity no matter where. The fact that this is all possible is because of the existence of electromagnetic waves: Antennas play a pivotal role in advanced functionality, efficient usage of the bandwidth, and cost effective deployment of this technology. The trends of the technological development of antennas for a wide range of commercial satellite communication services and the challenges faced in their development are chronologically reviewed. Various antenna concepts are summarized and future challenges are projected. A rather comprehensive list of references is included to assist the reader with further reading beyond this paper.

Technology Trends and Challenges of Antennas for Satellite Communication Systems

Due to pressures in the commercial sphere for increased information transfer rates or from the military to further miniaturize equipment to improve its portability, there has been a steady move toward higher carrier frequencies. For more than a decade now, increasing numbers of satellite communications systems have been in operation at millimeter wavelengths. Even where there is a clear view of the satellite from the ground station, a range of meteorological phenomena still combine to make propagation impairment a serious problem. Because of their complexity, difficulties in modeling them, and deficiencies in basic physical understanding, progress in engineering such systems has involved a large dose of empiricism. Ideally, this means a solid database of propagation measurements, made as nearly as possible in the intended geographical area of operations. Because of the time and cost of their accumulation, attempts have been made to use classification into climate zones on a worldwide basis to extend existing data to a wider range of situations. However, most of the measurements in the databases have been made in northern hemisphere temperate zones. Much evidence suggests that in tropical and equatorial zones, the factors that make important contributions to propagation impairment are different, putting a strong question mark over the use of existing design methods. This review looks at those deficiencies and their likely impact on system performance. At this time, rather than providing definitive answers - which must wait on further work - the best that can be done is to highlight difficulties and encourage realistic expectations. In a final section, the review examines the question of whether costly, application-specific measurement programs might now be avoided by mining increasingly sophisticated national meteorological records.

Propagation impairment on Ka-band satcom links in tropical and equatorial regions

Impairment of radio wave signal by rainfall on fixed satellite service on earth-space path at 37 stations in Nigeria

Model-oriented methods to predict antenna noise temperature due to rainfall along slant paths are developed and illustrated for communication systems at Ka-band and above. The adopted Sky Noise Eddington Model (SNEM) relies on an accurate analytical solution of the radiative transfer equation and on stratiform and convective rainfall stratified structures, synthetically generated from cloud-resolving model statistics. The approach to predict antenna noise temperature is based on the multiple regression analysis, trained by SNEM-derived cloud radiative data sets, and can handle either slant-path attenuation or columnar liquid water or rain rate as input predictors. Statistical scaling with respect to frequency and zenith angle is also analyzed and modeled in the microwave and millimeter-wave range. In order to test the proposed prediction technique, measurements of the ITALSAT satellite ground-station at Pomezia (Rome, Italy) are taken into consideration for two case studies. Combined data from the ITALSAT three-beacon receiver at 18.7, 39.6, and 49.5 GHz and from a three-channel microwave radiometer at 13.0, 23.8, and 31.6 GHz are processed. Results are shown and discussed in terms of antenna noise temperature estimation by using the satellite-beacon path attenuation as predicting variable.

Predicting Antenna Noise Temperature Due to Rain Clouds at Microwave and Millimeter-Wave Frequencies

[1] Long-term statistics of tropospheric attenuation were derived from almost 4 years of measurements made in the south of England using the ITALSAT F1 beacon signals at 49.5, 39.6, and 18.7 GHz; coincident rainfall rate measurements were made at the site of the receiving ground station. A method to remove the nonatmospheric changes of the beacon signals and to establish the reference levels from which to measure the excess and total attenuation has been presented in detail. The accuracy of fade level retrieval is estimated to be ∼±0.5 dB. A new method for predicting the annual total attenuation statistics has been proposed and validated against our data and data collected in Italy at 18.7, 39.6, and 49.5 GHz. For both locations, the new proposed method gives much better predictions compared with the established International Telecommunication Union recommendation method. A significant monthly and seasonal variation was observed in the attenuation and rainfall statistics and should be taken into consideration when planning the design and use of future slant path systems. We have seen that the attenuation statistics are subject to diurnal variations; however, for the period analyzed, this variation does not seem to follow a particular pattern.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005RS003252

Long-term statistics of tropospheric attenuation from the Ka/U band ITALSAT satellite experiment in the United Kingdom

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.

F. Davarian

Papers

System requirements for Ka-band Earth-satellite propagation data