Page 25 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

A QUICK OVERVIEW OF A NEW SCINTILLATION DATABASE
Ana Pinho, Susana Mota, Armando Rocha
Departamento de Eletrónica, Telecomunicações e Informática/Instituto de Telecomunicações, Universidade de Aveiro, Campus
Universitário Santiago 3810 193, Portugal

Abstract – This paper explores a new Ka and Q-band dry scintillation database and ancillary meteorological
data collected at Aveiro, Portugal in two converging Earth-satellite propagation paths. The measurement
equipment, the parameters of both links and the processing procedure of the database are described first.
The dependencies of the hourly averaged scintillation standard deviation with respect to several
meteorological parameters, measured at the ground level, and with respect to the wet refractive index are
analyzed. The diurnal variation of the hourly averaged scintillation standard deviation, on a monthly and
yearly basis, is explored. The yearly amplitude distributions, fades and enhancements, are presented and
compared against some available models. The scatter plot of the concurrent hourly averaged scintillation
standard deviation is analyzed and a frequency scaling factor is tentatively derived.

Keywords – Diurnal variability, modeling, scintillation

they do not share any hardware.
1. INTRODUCTION
The general characteristics of the links are given in
A microwave signal crossing the atmosphere is the following table: where the (dB-Hz) is the
0
subjected to several impairments such as carrier to noise spectral density ratio in clear sky.
attenuation, depolarization and scintillation. The Table 1 – Ka and Q-band receiver characteristics
scintillation is caused by the scattering of
atmospheric refractive index irregularities in Parameter Ka-Band Q-band
turbulent layers that evolve over time and drift Antenna diameter (m) 1.50 0.62
through the propagation path carried by the wind. Elevation(º) 39.63 31.9
The phase and amplitude distorted wave front is Azimuth (º) 153.95 134.6
integrated by the receiving antenna aperture giving CNR0 (dB-Hz) 53.0 57.7
rise to the observed signal amplitude fluctuations Polarization quasi-V (º): tilt angle 19.5 12.3
(phase fluctuations are more difficult to measure) Sampling rate (S/s) 8 8
around a mean value computed typically in
1 minute to 5 minutes. The site coordinates are 40 37´ N and 8 39’ W
0
0
being the Q-band receiver about 3 m below the Ka-
The modeling of scintillation is important because it band receiver (in an office below the roof). The
can disturb the fade mitigation systems and the angular aperture between the two links is about 17 .
0
scintillation fades can impact the availability of Recently the K-band receiver front-end was
terminals with very small fade margins. refurbished and the has been improved by
0
Scintillation long term data at Q-band and databases about 4 dB. A small meteorological station is also
collected with concurrent satellite links are yet co-sited and measures temperature, relative
relatively scarce in the literature. humidity, rain rate, wind speed and atmospheric
pressure at the ground level.
2. EXPERIMENTAL SCENARIO Q-band data are logged by a MATLAB application
Two propagation experiments have been active at our into a set of files and the Ka-band beacon and
site: one using the Ka-Sat satellite Ka-band beacon at meteorological data are logged by a Labview
19.68 GHz and the other with the Alphasat satellite Q- application into another set of files. The beacon data
band beacon at 39.402 GHz. The receivers use FFT copolar amplitude time series is stored at a
techniques for signal detection whose samples are sampling rate of 8 S/s.
stored, in both cases, at a rate of 8S/s. More information
can be found in [1]. The receivers are fully independent;

© International Telecommunication Union, 2019 9