SYSTEM OF MEASURE AND REPRESENTATION OF

ELECTROMAGNETIC EMISSIONS

Rafael Herradón, Florentino Jimenez, Julia Galiano, Juan Fernández-Corugedo

Departamento de Ingenieria Audiovisual y de Comunicaciones(DIAC).

Politecnic University of Madrid (UPM)

Keywords: Real-time systems control, environmental monitoring and control, Simulation, Propagation models,

Antennas, Radio communications.

Abstract: Due to the vertiginous increase of the electromagn

etic emissions of the modern communication systems and

to the affected population's concern, it becomes necessary a more exhaustive control of this type of

contamination. There are available different measure devices that make a characterization of the received

emissions, but most does not discriminate between the contributions from different systems. Therefore, you

cannot identify the systems responsible for the excessive measured levels. Of all the studied devices, the one

that better it fulfils the expectations it is the spectrum analyzer, that it allows to characterize the received

emissions, separating the different bands of the spectrum, and isolating the frequencies that don't perform

the existent norm. To control the spectrum analyzer we have developed a software program that makes the

measures according to the procedure exposed in the standard. Finally, another program processes and it

represents the results of the measures. In addition, this application can calculate the theoretical level of

radiation of different communication systems by simulation approximations and then, to compare with the

measurement levels and with the reference level.

1 INTRODUCTION

People demand every time a bigger mobility of the

systems of communications that they use in their

daily life. To satisfy this demand, different

technologies have appeared in the last times based

on the propagation of the electromagnetic waves that

it has relegated the cable to a second plane. As

examples of these technologies, we can mention the

mobile telephony (GSM, UMTS …), the wireless

networks (WiFi, Wimax), the communication

through Bluetooth, etc… The most attractive case

has been in the entire world the exponential grow of

the use of the mobile telephone.

The problem of the expansion of the wireless

syste

ms is the increase of the emission levels that it

can be considered harmful if it surpasses certain

exposure levels. To this physical problem, it is

necessary to add the visual and psychological impact

in the population that it is caused by the antennas of

base stations. All of this has produced an effect of

rejection in the population. Although they do not

want to lose the comforts that offer them these new

systems, they want to be sure that they do not

represent a danger for their health, demanding a

more restrictive control of the emissions levels

produced for these systems.

To respond to this concern they have been

devel

oped a series of recommendations and

standards that they regulate the maximum levels of

emissions that will tolerate (ICNIRP, 1998). In spite

of this effort, the population does not have

knowledge from the levels to those that is exposed,

and neither have they known the levels to which the

exhibition can be harmful. Even those titled capable

to characterize this emissions they find several

problems in identifying the source of emissions that

is surpassing the acceptable levels.

To solve these problems, we have developed a

syste

m able to make a complete characterization of

the completely conflicting spectrum, using the

hardware and software resources to obtain

accurately measurement, representation and

estimation of the emission levels.

368

Herradón R., Jimenez F., Galiano J. and Fernández-Corugedo J. (2005).

SYSTEM OF MEASURE AND REPRESENTATION OF ELECTROMAGNETIC EMISSIONS.

In Proceedings of the Second International Conference on Informatics in Control, Automation and Robotics - Signal Processing, Systems Modeling and

Control, pages 368-371

DOI: 10.5220/0001183603680371

 SciTePress

2 CAE PROGRAM

Spectrum Analyzer control (CAE) is a software

application that allows the user to make different

types of measures. This program controls a

Spectrum Analyzer and a GPS by the serial ports. To

carry out these measures the user has a series of

utilities, created for each one of the measure options.

The program is divided in five modules:

Configuration: This module helps the user through

the process of configuration of the antenna factor

and the lost of the cable.

Analyzer mode: The program sends commands to

the analyzer in real time, and the user can select the

frequencies that he wants to measure, showing the

results in a program window in the same way that

they would be seen in the analyzer.

Carrier measurement: It makes a temporal

characterization of a number of carriers selected by

the user. For this application, we use the span zero

mode of the spectrum analyzer.

Band measurement: This is the most significant

module for the estimation of emissions level. It has

two measure methods, one quick, but of less

reliability and another that requires more time but

whose results are more precise.

Each one of these applications saves the obtained

data with a certain format, in some cases attaching

the obtained graphs. So the user can check the

measures in any moment.

Figure 2: Text and graphical format of data

Each one of the text files contains the position

provided by the GPS, as well as all the data obtained

in the realized measure. Additionally, we can send

de captured data to a remote monitoring system

(Ruiz et al., 2005) using a mobile data

communication system as GPRS.

2.1 Jump in Frequency

This approach has been developed by the necessity

of making reliable measures, similar to accurately in

the broadband systems, such as isotropic probes and

field meters. We have made several measures that

have demonstrated that they should not take all the

points captured by the analyzer to make the field

calculations and received power. To know what

frequencies it is necessary to use and which it is

necessary to discard we use the following equation:

(1)

where RBW and Span are the resolution bandwidth

and the span of spectrum analyzer respectively and

Rate it is an adjusting parameter.

With this equation, we obtain the jump that we

make when we select the frequencies band that will

be analyzed

Figure 1: Application main window

pointsN

Span

RBWRate

Jump ⋅ º

⋅

SYSTEM OF MEASURE AND REPRESENTATION OF ELECTROMAGNETIC EMISSIONS

369

3 MODELEM PROGRAM

MODELEM is an application developed in

MATLAB to Model the Electromagnetic Emissions.

It is very intuitive and easy use software with a

series of graphic interfaces. The user can do

different actions related with Coordinates change,

antennas radiation diagram, propagation models,

transmission systems and projects. A project consists

on calculating the levels generated by a transmission

system and to make a graphic representation.

Moreover, the measurements done with the

software CAE can be represented in MODELEM to

compare the similitude between the theoretical

calculus and the measurement values. If the GSP

was connected when the measurement was been, the

coordinates are used to do the representation.

However, if the GSP was not connected, the

coordinates should be introduced manually. Then a

map can be superimposed at the measured levels.

)bpd(),,d(F

EIRP

)bpd(),,d(F

EIRP

kkkk

≤ϕθ

∑

So this program has different functions: represent

measures, simulate theoretical levels and compare

both with the security reference levels give by the

standards.

3.1 Representation of measures

The first of these functions allows the user to

process the data obtained in the measure. To

complete the representation we can add a map.

3.2 Diagrams of Radiation

Besides the representation of measures, the

MODELEM can simulate the levels radiated by a

series of systems transmitters.

To make the simulation, the user has to introduce

the data of the transmitters, and the horizontal and

vertical radiation diagram of the antennas. One of

the most complicated task is calculates the diagram

in three dimensions.

Figure 4: Radiation diagram of the antenna

3.3 Radiation models

To obtain the emitting levels we can use different

propagation models: theoretical models, (Free

Space, Flat Terrain), empirical models (UIT-R,

Okumura Hata, etc) or models based on Ray-tracing

and Ray-launching. It is necessary to consider some

specific circumstances such as the number and

location of the different emitting sources, the high

range of frequencies, etc.

One accurate and not excessively complicate

model to estimate the level of emissions is proposed

in (Herradon et al., 2002). This is a two-slopes

model with a Rayleigh factor for multipath

propagation.

(2)

Figure 3: Representation of measures and map.

ICINCO 2005 - SIGNAL PROCESSING, SYSTEMS MODELING AND CONTROL

370

where EIRP, equivalent isotropic radiated powe

istance from the source and

r, d

()

the relative

diation pattern. The model above mentioned is

ditions. T

for

u itting levels produced by a typical

o tion for mobile communications

with PIRE = 1 KW are shown. In this case we use

me approaches for

ifferent environments, and they was compared with

number of emitting stations appear in figure 6.

We had developed a system that allows any user to

agnetic emissions of a

t types of measures, and saving the

sults for their later study.

gation models, several

ansmission systems, etc. The user can check if the

Guidelines for limiting exposure to time-varying electric,

agnetic fields. ICNIRP, 1998.

dation K.52., 2000)

Guidance on complying with limits for human

Radiation levels for some

ons.

only appropriate in far-field con he most

common accepted definition far-field in

communications is d = 2D

/λ, where D is the largest

dimension in the antenna, λ is the wavelength and

both must be in the same units. However, in emitting

measurements it can be considered that the field is

almost formed from d= λ.

3.4 Results

In fig re 5 the em

3-sect r base sta

the free space expression as propagation model.

Figure 5: Power density levels, in horizontal and vertical

plane, relative to Reference Levels

Considering the application of the before models,

we have been carried out so

measurements carry out with the CAE program. The

results are very closed when we adjust the

propagation model.

An area corresponding to a big city with a high

Figure 6: Simulation of emitting levels in a city

4 CONCLUSIONS

make a study of the electrom

interest area.

The program CAE help to the user in the process

of realization of measures. Allowing the user to

make differen

In the program MODELEM, the user can do a

simulation of emission levels, including antennas

radiation diagrams, propa

le els obtained in the measure coincide with the

obtained ones in the theoretical simulation

REFERENCES

magnetic and electrom

(ITU-T. Recommen

exposure to Electromagnetic Fields”. ITU-T.

Recommendation K.52. Feb 2000.

Recommended practice for measurements and

computations with respect to human exposure to

Radiofrecuency Electromagnetics Fields, 3 KHz to

300 GHz”.IEEE.1998

V. Ruiz, M. R. Herradon, F. Jiménez. “Remote

Monitoring Distributed Systems”. ICINCO- 2005

Herradon, F. Jimenez, L. Muñoz Aguilera. Simulation

of Electromagnetic

Radiocommunication System. Advances in Systems

Engineering Signal Processing and Communicati

WSEAS press.2002. pp 273-277.

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