Power transfers, nonlinear distortions, internal noise of electronic equipments, frequency bands and applicable regulations, disturbances generated outside the equipments, attenuation due to gases and rainfall, frequency conversion and superheterodyne receivers, multi-section terrestrial and satellite connections, examples of applications.
R. E. Collin: "Foundations for Microwave Engineering", II ed., McGraw-Hill, 1992
F. T. Ulaby, R. K. Moore, A. K. Fung: "Microwave Remote Sensing active and passive", Vol. I, Addison-Wesley, 1981
T. T. Ha: "Digital Satellite Communications", II ed., McGraw-Hill, 1990
ITU-R Recommendations, www.itu.org
Documentation Eutelsat: www.eutelsat.org
European normative EN 300 421: www.et
Lecture notes available on the MOODLE platform of UniFI
Learning Objectives
Objective of the course is to provide an understanding of the basic operating concepts of modern telecommunication systems and to explain general design criteria for developing their components.
Prerequisites
Basic concepts of circuits theory, signal theory and electromagnetism
Teaching Methods
Class lessons with bottom-up system approach: the final connection is the synthesis of all its parts. Each component is preliminarily explained and illustrated by means of examples.
Further information
The course is an updated synthesis of two previous courses, later condensated in a unique 9 ECTS courses, shortened to the present 6-ECTS version beginning with 2014/15
Type of Assessment
Prova orale.
Course program
1 - CHARACTERISATION OF IDEAL AND REAL TWO-PORT LINEAR SYSTEMS
Introduction. Models of 2-port linear time-invariant systems using Z parameters. Input and output impedences. Systems’ transfer functions. Direct connection of a generator with a load. Conditions for undistorted output and maximum power transfer. Connection of a generator with a load by means of a 2-port system. Definitions of power gain, available power gain, transduction power gain. Available attenuation of passive systems. Expressions for the average power at the output of a 2-port system. Nonlinear distortions of 2-port systems: compression and harmonic distortion; intermodulation distortion.
2 – INTERNAL NOISE
Characterisation of internal (device) noise: recalls on statistics features of thermal noise; expression of the mean power spectrum at radio-frequencies; approximate expression for frequencies up to microwaves; equivalent Thévenin and Norton generators; cases of passive bipoles with resistive elements at equal and different temperatures: concept of equivalent noise temperature; extension of the concept of equivalent noise temperature to the case of non-thermal noise; general modelling of a noisy generator bipole.
Noise introduced by 2-port systems: equivalent noise temperature brought back to the system’s output or input; case of a passive system; case of an active system: punctual noise figure and its relationship with the equivalent noise temperature. Meaning of the noise figure in terms of signal-to-noise ratio. Standard noise figure. Noise specifications of a radio-frequency amplifier. Cumulative noise figure of cascaded systems (Friis’ formula). Mean noise figure and noise temperature.
3 - RUMORE ESTERNO
Brief notes on ITU. Noise of meteorological origin: general characteristics and maps of ITU-R. Man-made noise. Radiometric quantities: radiance and spectral radiance. Power received by an antenna in terms of radiance. Concept of blackbody and Planck’s law; Rayleigh-Jeans’ and Wien’s approximations of Planck’s law. Concept of grey body; radiance temperature of equivalent blackbody; emissivity. Extension to the case of non-thermal emissions. Power received by an antenna and definition of radiometric temperature of antenna. Expression in terms of main-lobe and side-lobes contributions. Galactic emission. Radio maps of sky: contribution of galaxy; radio-stars. Atmospheric absorption noise. Apparent temperature of sky. Terrain noise; radiometric temperature of terrain. Estimation of antenna’s temperature in the micro-wave region.
4 – RADIO-RECEIVERS
Characteristics of superheterodyne receivers. The problem of image frequency. Use of a filter preselector for rejecting the image frequency. Image frequency rejection by means of double conversion and self-rejection mixers. Brief notes on homodyne receivers, sensibility and dynamics of receivers, and on automatic gain control (AGC) systems. Frequency modulation (FM) analogue broadcasting of stereophonic sound.
5 – BASIC ANALYSIS OF TERRESTRIAL AND SATELLITE LOS LINKS
Recalls on the formula of line-of-sight (LOS) radio links. Definition and examples of measurement of the factor G/T of a receiving station in the band of microwaves. Expression of the signal-to-noise ratio (SNR) of a LOS link. General characteristics of connections via geo-stationary satellites. Expression of SNR for non-regenerative satellite connections. Brief notes on the modalities of access and back-off technique of transponders. Comparisons with a terrestrial radio-bridge link. Brief notes on digital television broadcast from satellite (DHT); example of sizing of a DHT receiving station.
6 – TROPOSPHERIC ATTENUATION
Attenuation due to gaseous atmospheric constituents. Attenuation due to precipitations: expression of the specific attenuation in the case of rain: distributions of drops diameters as a function of the rainfall rate; evaluation of rainfall specific attenuation and related frequency plots.