17-experimental characterization of a surfaguide fed plasma antenna

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 59, NO. 2, FEBRUARY 2011 425

Experimental Characterization of a Surfaguide FedPlasma Antenna

Paola Russo, Member, IEEE, Valter Mariani Primiani, Member, IEEE, Graziano Cerri, Member, IEEE,Roberto De Leo, and Eleonora Vecchioni

Abstract—The possibility of using a surfaguide device as plasmasource for plasma antenna application has been experimentallyinvestigated. The surfaguide was optimized, realized and used forthe ignition of a plasma column to be used as a radiating struc-ture: the coupling with the radiated signal network and plasmaantenna efficiency were measured showing that a surfaguide canbe effectively used to create and sustain the plasma conductivemedium. A plasma diagnostic technique was also developed toevaluate the plasma column length and plasma conductivity withrespect to the power supplied. These measurements highlightedthat plasma antenna properties are strongly affected by the pumpsignal and therefore this signal has to be optimized in order tohave the highest conductivity.

Index Terms—Conductivity, efficiency, plasma antennas,surfaguide.

I. INTRODUCTION

T HE idea of using a plasma element as the conductivemedium in radio-frequency (RF) antennas and reflectors

is not new [1]: several studies have demonstrated the feasi-bility of such devices [2]–[4]. In recent years, the scientificcommunity has shown a growing interest in plasma antennasmainly because of their peculiar and completely innovativeproperties with respect to traditional metallic antennas. Theelectromagnetic characterization of a plasma antenna accordingto standard parameters requires the analysis of the physicalaspects involved in the interaction mechanism between anelectromagnetic field and a plasma; therefore new models andexperimental techniques have to be developed [5]–[8].

A plasma antenna can be rapidly switched on or off by ap-plying bursts of power to a tube filled with a low pressure gas:the power supplied ionizes the gas providing the conductivemedium for the RF signal to be radiated; in plasma antenna ap-plication two signals are needed: the pump signal that createsand sustains the plasma column, and the signal to be radiated(in the following simply indicated as “radiated signal”) that hasto be coupled to the plasma element.

Thanks to this mode of operation, the plasma antenna offersseveral advantages over traditional metal antennas.

Manuscript received November 17, 2009; revised June 30, 2010; acceptedAugust 04, 2010. Date of publication December 03, 2010; date of current ver-sion February 02, 2011.

P. Russo, V. M. Primiani, and G. Cerri are with the “Università Politecnicadelle Marche,” Ancona I-60131, Italy (e-mail: [email protected]).

R. De Leo is with the University of Ancona, Ancona I-60131, Italy.E. Vecchioni was with the “Università Politecnica delle Marche,” Ancona,

Italy. She is now with the Software R&D Unit, Thermowatt, SpA, Arcevia60011, Italy.

Digital Object Identifier 10.1109/TAP.2010.2096387

The possibility to switch on and off the plasma makes plasmaantennas suitable for the production of time varying radar crosssection elements: when plasma is on, it behaves like a conductor,when it is off, it behaves like a dielectric material. This charac-teristic provides the possibility of creating reconfigurable array:an electrical control of the ignited elements allows the modifica-tion of the array geometry and so of its radiation characteristics.A simple linear plasma antenna can be created by using a tubefilled with a gas. The effective antenna length of the column caneasily be changed by controlling the power supplied to the pumpsignal.

Finally, the electromagnetic characteristics of plasma can beused to realize frequency selective shields.

The key point in the realization of plasma elements to be usedas plasma antennas is the ignition of the plasma column: thepump signal network has to be optimized in order to obtain thehighest plasma conductivity with the lowest power. At the sametime, the realization of the feeding network must not degradethe antenna radiating properties.

In the past, plasma was produced by DC or high frequencydischarges from two electrodes at opposite ends of the column;[1] proposed a new way of producing microwave and RF dis-charges based on electromagnetic surface waves to sustain thedischarge: in this way plasma could be driven from only oneend of the column and electrodes should no longer be needed.Since the 1960s studies have shown that a surface wave canpropagate along the interface between a plasma column and thetube containing it [9], [10] but the idea of using these waves tosustain a plasma column was only developed in the 1970s: in[11] a surface-wave-produced discharge was identified for thefirst time. On the basis of these studies, several surface-waveplasma sources have been developed: in [5], [8] a surface wave islaunched by a capacitive coupling applying an intense field be-tween a copper ring placed around the tube and a ground plane.The surfaguide is another device, first proposed in [12] and il-lustrated in several papers [13]–[17], which could be used as aplasma source, and it is by far the simplest of the surface-wavelaunchers: it is a wave-guide device able to excite a surface wavethat propagates along the tube axis providing the power requiredto ignite the plasma.

With respect to other plasma sources the surfaguide presentssome advantages that can be favorably considered in designingplasma antennas: it is the most suitable device to propagatea power signal, confining its electromagnetic field in a closedstructure; it is simple to realize, and matching stubs can easilybe inserted in the design. Moreover, it can be used to feed sev-eral plasma elements realizing arrays of antennas. Finally, it of-fers the possibility of using the frequency of 2450 MHz for the

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426 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 59, NO. 2, FEBRUARY 2011

pump signal because at this frequency high power is availablewith low cost.

In this paper a complete characterization of the surfaguide asa feeding network for plasma antenna application is presented.This is a new application of an old structure that is usually usedto produce plasma for different purposes. In this paper the geo-metric parameters of the surfaguide have been designed in orderto optimize the radiation properties.

In this study is also proposed a measurement set-up and de-scribed the experimental procedures followed to characterizeboth the surfaguide system and the radiated signal network. Inparticular a 2.45 GHz pump signal is used for antenna ignition,and the frequency of 430 MHz is chosen for the radiated signal,because both frequencies belong to the ISM frequency set andcan be used without particular restrictions.

The most critical aspect of the work is related to the strongcoupling between the pump and the radiated signal networks.In fact, plasma antenna parameters have to be characterized, interms of efficiency, effective length and conductivity, when thesurfaguide is used to create and sustain the conductive medium.

Moreover, plasma antenna properties are also strongly af-fected by the pump signal and therefore they have to be self-con-sistently determined: in particular, plasma conductivity, that de-termines the “metallic behavior” of plasma, relies on the ioniza-tion process ignited by the pump signal.

The paper is organized as follows: Section II shows thedesign, the optimization and the realization of the surfaguideand the pump signal network used to supply the 2.45 GHzsignal; Section III illustrates the signal network and describesthe measurement of antenna efficiency; finally Section IVreports the measurement procedures to characterize the plasmacolumn length and conductivity.

II. SURFAGUIDE: OPTIMIZATION AND REALIZATION

This section describes the realization of the surfaguidesystem, designed to achieve an efficient ignition of the plasmacolumn; this device represents the main difference with respectto traditional radiating systems, and is necessary to create theantenna. The whole feeding network set-up is also important,because it allows the power delivered to the antenna to becontrolled and the effective power required for ignition to bemeasured.

A plasma column is created by applying a pump signal toa tube containing a gas; the gas is ionized by a strong mi-crowave electric field applied at one termination of the tube bya surfaguide device. The surfaguide launches an azimuthallysymmetric electromagnetic surface wave that propagates alongthe tube creating and sustaining the plasma column.

The surfaguide is basically a waveguide with a tapered sec-tion designed to increase the electric field strength in the reducedheight region without affecting the impedance matching. Fig. 1shows the longitudinal section of the surfaguide: it consists oftwo trunks L0 of a standard waveguide WR340, two transitionsL1, and a waveguide L2 with a reduced height. The guide is ter-minated by a moving short, whose length Ls can be varied formatching when the plasma column is turned on.

Two holes along the central axis of the reduced height guideallow the glass tube to be inserted: a commercially available

Fig. 1. Longitudinal section of the surfaguide. The vertical tube containsplasma to be ignited.

Fig. 2. Longitudinal section of the surfaguide in the coupling region with theglass tube: the simulated electric field is normalized to 1 W of incident power.

tube designed for lighting purposes was used to create theplasma column.

The structure presented in Fig. 1 has to be optimized forthe frequency 2.45 GHz: the surfaguide geometrical parametersneed to be carefully chosen in order to have a very intense fieldcoinciding with the holes where the tube is inserted. The opti-mization of the surfaguide dimensions was achieved using thecommercial software CST Microwave Studio [18] to simulateelectromagnetic field behavior before plasma ignition; the tubeis a glass cylinder with thickness mm, diameter

mm, filled with a dielectric having a relative dielectricconstant . Fig. 2 shows the electric field in the longitu-dinal section of the surfaguide: the field of the waveguideis well-coupled with the axial TM field of the surface wave alongthe glass tube that ignites the plasma: asGHz cm GHz cm (where is the plasma frequency) onlythe first TM mode of the surface wave is expected to be excited[14].

A parametric investigation of the field behavior was numer-ically carried out to determine the best values of the hole di-ameter D, guide height h, and transition length ; field valueswere normalized to 1 W of incident power and was set to getthe maximum field which corresponds to the tube axis. To com-pare different situations the electric field was evaluated at three

RUSSO et al.: EXPERIMENTAL CHARACTERIZATION OF A SURFAGUIDE FED PLASMA ANTENNA 427

TABLE IMAXIMUM ELECTRIC FIELD INTENSITY

TABLE IIMAXIMUM ELECTRIC FIELD INTENSITY

points: in the reduced height guide, on the internal face of theglass tube, at the tube centre.

First of all a numerical investigation was conducted for thefield intensity with hole diameter D and fixed h, and and,as expected, this showed that the narrower D is, the more intensethe field is; therefore, D is chosen as small as possible to allowthe tube to be inserted.

The behavior of the field as a function of h for fixed D, and(Table I) is more interesting: a reduction in the guide height

increases the field inside the tube, but beyond the optimal valuea further reduction does not improve the field strength in thetube.

Table II shows the behavior of the electric field as a functionof the taper length and the final short termination distance: alsoin this case the optimal value was found, and finally the designparameters were set: mm, mm, mm.

After realizing the surfaguide, the 2.45 GHz pump signal net-work was developed (Fig. 3). The power needed to ionize thegas was supplied by a magnetron generator; an isolator was in-serted to prevent the high reflected power from arriving at thesignal generator and a directional coupler was used to monitorthe incident and reflected power.

The minimum power necessary to ignite a small portion ofplasma in the tube region crossing the waveguide is 2 W: on in-creasing the power it is possible to notice that the plasma columnheight also increases.

Fig. 3. Pump signal network.

Fig. 4. Signal connection network: the capacitive coupling between the copperring and the metallic box is used to feed the antenna.

The set-up shown in Fig. 3 was used to investigate the non-linear behavior of a plasma column as a function of the power:this aspect strongly affects the plasma antenna characteristics,in particular, efficiency, column length and conductivity.

III. MEASUREMENT OF ANTENNA EFFICIENCY

This measurement was carried out by comparing the powerdelivered by the radiated signal of a plasma antenna, and thesame signal, radiated under the same conditions, by a copperantenna. The procedure is conceptually simple, but requiresan accurate realization of the set-up in order to control: (i) thecoupling between the pump and radiated signal networks toprevent instrument damage (Section III.A), (ii) the radiatedsignal power and matching conditions for measurement accu-racy (Section III.B).

A. Coupling Between Pump and Radiated Signal Networks

A preliminary measurement of the coupling between thepump signal and the radiated signal network was performed:coupling occurs because the signal is connected to the plasmacolumn.

The signal to be radiated was coupled to the plasma antennaaccording to the set-up shown in Fig. 4, [5], [7]. The networkwas enclosed in a metallic cubic box with a side of 6 cm, placedbelow the surfaguide. The fluorescent tube comes out of the topwall of the box through a 19 mm diameter hole, and penetratesinto the surfaguide for plasma ignition.

A capacitive coupling is generated for the radiated signal be-tween the box and a copper ring surrounding the tube; this pro-vides the electric field that excites the signal current along the

keshavarz

Highlight


Fig. 5. Measurement set-up used to characterize coupling between pump andsignal networks.

Fig. 6. Measurement set-up for antenna relative efficiency.

plasma antenna. The copper ring is placed at about 1 mm fromthe box upper wall.

The pump and signal networks are coupled by the plasmagenerated in the tube. The pump generator generally providesa high power wave that could damage the signal network, andtherefore it is necessary to quantify and reduce the coupling.The 2.45 GHz signal coupled to the signal network was mea-sured straightforwardly with the set-up shown in Fig. 5: the iso-lator exhibits a band pass between 423 and 433 MHz for the430 MHz direct signal and an attenuation of 13.8 dB for an in-verse signal at 2.45 GHz; a further protection for the spectrumanalyzer is given by the 20 dB attenuator and by the cable at-tenuation. The 2.45 GHz signal coupled to the signal networkis dBm (3,6 dBm at the insulator) for an incident pumppower of 44 dBm: this attenuation is high enough to ensure thatthe signal generator (later used in place of the spectrum ana-lyzer) is not damaged for incident power up to 100 W (Fig. 6).

B. Relative Efficiency Measurement

A plasma column is characterized by a specific conductivitygiven by the free electrons of the ionized gas: if this conductivityis high enough, the plasma column can be efficiently used asthe medium for an RF signal to be radiated. However, plasmaconductivity is not as high as that of metal and therefore plasmaantenna efficiency compared with the efficiency of a traditionalmetallic element has to be evaluated.

The procedure consists in measuring the field radiated by aplasma column and the field radiated by a metallic element of

TABLE IIICORRECTION FACTOR

the same length and fed with the same signal network, as shownin Fig. 6, but switching off the pump signal; relative efficiencyis defined as

(1)

where and are the power received atthe spectrum analyzer when plasma and copper respectively areused as radiating elements.

The 430 MHz generator is set at the maximum availablepower (20 dBm) in order to have a good signal to noise ratioat the receiver. The radiated signal was measured with a loopplaced in four different positions at the same distance from theradiating element in order to check the reliability of the results(Fig. 6).

During the first stage, measurements were carried out afterswitching on the plasma element with 25 W of pump power,which allows the complete ignition of the column. The plasmacolumn was then removed and substituted with a copper tube ofthe same length; the pump signal was switched off because notneeded and the signal to be radiated was coupled to the copperelement in the same way as the plasma column.

Table III shows the matching conditions of the radiatedsignal coupling network (Fig. 4) at 430 MHz; this prelimi-nary measurement is necessary in order to compare the twosituations, since the efficiency has to be evaluated for thesame effective signal power passing through the antenna inputterminals. Measurements highlighted that the copper antennais more mismatched than the plasma element, and therefore acorrection factor of 0.9 dB was added to the power radiated bythe copper element.

Results of the power measured by the spectrum analyzer forthe plasma and the copper elements in four different positionsare reported in Table IV. It is important to point out that themeasurement of the radiated signal is a narrowband measure-ment around 430 MHz, while the pump signal has a 2450 MHzfrequency. This narrowband measurement reduces the 430 MHznoise floor (when the useful signal is switched off) about 30 dBbelow the useful signal peak.

In Table IV, it is possible to notice that the average perfor-mance degradation of the plasma antenna with respect to thetraditional metallic one is about 2.9 dB for all probe positions.This means that, for the analyzed structure, about half the powerof the radiated signal is lost due to losses mechanism inside theplasma.


TABLE IVRECEIVED POWER

Fig. 7. Current probe for plasma diagnostics (a) to be put around the glass tube(b).

IV. PLASMA COLUMN HEIGHT AND CONDUCTIVITY

MEASUREMENTS

A direct measurement of the plasma column length H andconductivity is not possible. In fact a simple visual inspectionof the light emitted by plasma [5] to evaluate H is susceptibleto great measurement uncertainty. Moreover, the inner region ofthe tube is not accessible for a direct measurement of .

As a consequence an indirect diagnostic technique to evaluatethe plasma state along the column as a function of the pumppower was developed.

The idea was to design a loop probe to be inserted around thetube: the probe consists of a copper coil, Fig. 7(a), positioned asshown in Fig. 7(b) and connected to a network analyzer.

The probe input impedance depends on the ma-terial wrapped by the coil, which acts as a transformer: in partic-ular R depends on the power dissipated in the plasma becauseof the currents induced by the probe itself. The idea is to re-late R to the plasma state which coincides with the point wherethe probe is positioned; this method was developed consideringthe following assumptions: (i) conductivity depends only on thepump signal and not on the radiated signal or on the network an-alyzer signal: this assumption is well satisfied because the VNAsignal is very low (10 mW) compared to the pump signal (sev-eral watts); (ii) at the measurement frequency the effects of thewire resistance and the loop radiation resistance are negligiblewith respect to the dissipation in the material filling the tube; fi-nally, to make reasonable this assumption (iii) measurement hasto be carried out at a frequency lower than the resonance of thecoil in order to neglect the effect of the parasitic capacitances.Moreover, as the frequency approaches the resonance of the coil,the value of R depends not only on the conductivity , but alsoon more complicated factors (radiation, field penetration into

Fig. 8. Set-up for the measurement of plasma column length and conductivity.

Fig. 9. Real part of the input impedance measured with the coil placed in dif-ferent positions along the column: the point coinciding with the transition regionis critical, and the corresponding curve (crossed line) is the average of a few re-peated measurements.

the plasma) which affect its measurement. As a consequence ofthese assumptions, the frequency range for the network analyzersignal was MHz.

Measurements were carried out as shown in Fig. 8: the probewas positioned around the glass tube and connected to the net-work analyzer by a low pass filter to prevent the 2.45 GHz signalfrom damaging the network analyzer. The plasma state of thecolumn was achieved by retrieving the values of R moving theprobe along the tube.

A. Plasma Antenna Height

The input impedance was first measured when no pumppower was applied to the gas tube (gray line in Fig. 9). Subse-quently the pump power was switched on and the gas insidethe tube was ionized; as the power becomes greater, the plasmacolumn length increases. Supplying a fixed pump power to thecolumn, the plasma is ignited for only a certain length. The coilwas then moved along the column to appreciate how the plasmastate varies in the longitudinal direction: as the distance fromthe surfaguide increases, R becomes smaller, and, coincidingwith the position where the conductivity is no longer significant(28 cm in Fig. 9), the real part is the same as measured whenno pump signal is applied. This position at which the antenna isconsidered switched off (Fig. 9) determines the plasma columnlength.

This result allows us to determine the profile of the plasmacolumn length with respect to the pump power. Fig. 10 showsthe experimental results for the plasma column height comparedwith those obtained with a different feeding network in [5]. Inboth situations the column height is proportional to the square


Fig. 10. Plasma column length as a function of the absorbed power.

Fig. 11. Copper coil simulated with CST.

root of the power; the difference in values is due to the differentpump signal networks, gas pressure, and composition. More-over, in this study the column height was determined by mea-suring a significant electrical parameter rather than by a simplevisual inspection.

B. Plasma Conductivity

The same set-up shown in Fig. 8 was used to measure theplasma conductivity along the column: this is a key parameterbecause it affects all the radiation properties of plasma antennas.As a direct measurement is not possible, its value has to be in-ferred from R, determined for each probe position along the tubeaccording to the procedure described in the previous section. Apower balance between the power absorbed by the probe resis-tance R and the power lost in the plasma region surrounded bythe coil allows us to recover a relationship between R and [19]

(2)

In (2) the dependence of R on frequency and conductivity isexplicitly written. In our case the value of the constant cannotbe analytically calculated, therefore it has to be evaluated aftera proper calibration of the probe. Calibration was performed bysimulating the probe with the commercial software CST-Mi-crowave Studio [18] as shown in Fig. 11.

Numerical results were compared with some measurementsin order to check the accuracy of the simulations and to pro-vide the self-consistency of the procedure. was measured byputting the probe around some test-tubes filled with homoge-neous solutions of known conductivity and permeability whichwere then simulated with the aforementioned numerical tool.

Fig. 12. Real part of the input impedance measured on test-tubes of knownconductivity, numerical vs experimental.

Fig. 13. Relationship between R and � numerically recovered for three dif-ferent plasma (layer) radial thicknesses.

The frequency range chosen was lower than 150 MHz in orderto be far enough from the resonance of the coil (380 MHz) andto be sure that any variation in the permittivity of the materialwould not affect the measurements of the real part of the inputimpedance.

Fig. 12 reports the values measured and simulated for threedifferent test-tubes showing a good agreement between the ex-perimental and numerical results. Moreover, in the frequencyrange chosen, increases with and it is proportional to theconductivity predicted by (2).

The numerical results obtained for different material fillingthe glass tube could be used to obtain the desired relationship

with a good approximation, but in a plasma antennait strongly depends on the charge distribution inside the tube. Itis well-known from literature that plasma is mostly distributedalong the inner surface of the tube [20], [21], but we are not ableto appreciate experimentally the radial profile of conductivity.As an example, Fig. 13 shows the results obtained for a plasmauniformly distributed in an annular region of radial thickness

mm, mm, mm respectively.The uncertainty of the conductivity radial profile also affects

its distribution along the tube: Fig. 14 shows three differentlongitudinal profiles of plasma conductivity with respect to the


Fig. 14. Plasma conductivity with respect to tube length.

length of the tube, determined from the R measurement alongthe plasma tube.

Results show that the knowledge of plasma thickness is es-sential for determining the conductivity profile. Actually the un-knowns of the problem are two: plasma thickness and its con-ductivity. The knowledge of the loop input impedance is notsufficient to resolve the problem. It is necessary to add anotherindependent parameter that depends on both the unknowns: therelative efficiency and R, measured along the tube, permit to re-cover both the unknowns.

C. Method of Moments (MoM) Simulation of Antenna RelativeEfficiency

The goal of the MoM simulation is the theoretical determina-tion of plasma antenna efficiency at the frequency of the radiatedsignal (430 MHz) for different plasma conductivity profiles. Acomparison between the efficiency obtained with the MoM sim-ulation and the efficiency measured in Section III allows bothan estimation of the value of and an estimation of the plasmathickness.

In this section a dipole antenna with conductivity variationalong its length, as in the case of a plasma antenna, is inves-tigated. The classic approach based on the electric field inte-gral equation (EFIE) was adopted, and thin wire approximation(TWA) was assumed; the antenna is considered as a monopoleof length H over a ground plane.

With reference to the coordinate system in Fig. 1, for thescalar component , the EFIE to be satisfied on the antennasurface can be written as

(3)

The plasma conductivity is modeled as the straight interpo-lating line of Fig. 14

(4)

TABLE VRECEIVED POWER

being the conductivity coinciding with the point wherethe pump signal is applied. is the dipole current density ofthe radiated signal

(5)

with S(y) being the cross section where current flows with area

(6)

is the plasma column radius and is thesmallest value between the plasma layer thickness t and the skindepth at MHz, . is theantenna current flowing along the dipole axis according to theTWA and is also the problem unknown. Finally, isthe magnetic current loop, wrapped around the dipole, placed in

and representing the signal source.The method of moments (MoM) was applied using pulse

functions as basis functions and the point matching condition;the use of the proper conductivity for the plasma column leadsus to consider a varying cross section where the current densityflows along the antenna.

A numerical code was developed to solve the EFIE usingMoM. Convergence tests led to the choice of 61 basis andweighting functions for MoM implementation.

Both copper and plasma antennas were analyzed: in the firstcase an ideal conductor was assumed, whereas in the secondcase three different conductivity profiles were used. In particularthe straight interpolating lines and the corresponding thicknessof Fig. 14 were used. It is important to remember that these threeprofiles derive from the measured input impedance of the loopplaced around the tube.

Table V shows the power balance for a generatorV, and the theoretical efficiency calculated for the three situa-tions. These results highlight that the higher the conductivity isthe greater the radiation is and therefore a better efficiency isachieved.

It is clear that the conductivity profile with mm isthe most acceptable because only this value implies a calculatedefficiency dB similar to the measured one ( dB).


The results of the entire recovering procedure show that curvemm of Fig. 14 best describes the antenna conductivity

profile.We would like to underline that the plasma thickness

: in fact t depends on the power and fre-quency of the pump signal, whereas depends on the fre-quency of the radiated signal (430 MHz) and plasma conduc-tivity. In this example the skin depth has a minimum value of2.5 mm at the base of the antenna, therefore it is always greaterthan the estimated plasma thickness (0.5 mm).

V. CONCLUSION

Plasma antennas present some potential advantages com-pared with traditional metallic radiating systems, although anew approach for their characterization is required. This isdue to the need for generating plasma, the physical supportwhich allows the signal to be radiated. Even if the literatureconcerning plasma physics and application is extensive, veryfew papers deal with the specific subject of plasma antennas.In this context this paper is a step towards the definition ofmeasurement techniques for the experimental characterizationof this kind of antenna.

Two main problems have been considered and solved: the firstis the presence of two radio frequency signals at the same timeon the same structure; the second is the design of a sensor forthe characterization of the plasma state.

In the former case a suitable measurement set-up was devel-oped to evaluate and reduce the strong coupling between thepump and the radiated signals in order to prevent instrumentdamage and measurement errors; for the latter problem the mea-surement of the plasma state was complicated because the re-gion where plasma is ignited (a glass tube) is not accessible.In this situation an indirect measurement procedure was carriedout, involving a self-consistent technique that allows us to re-trieve the value of plasma conductivity using experimental dataand simulations.

The complex solution provided for plasma antenna charac-terization is intrinsic to the physical phenomenon, because allthe parameters strongly depend on each other according to non-linear relations.

Three important parameters were successfully measured: theefficiency of the plasma antenna, its length, and the column con-ductivity. Other parameters were also characterized in order toobtain the above mentioned quantities: matching conditions forboth the pump signal and the radiated signal, coupling betweenthe pump and signal networks.

The experimental analysis showed that the surfaguide is aneffective device to excite plasma antennas and is also suitablefor array configurations. At the same time this study underlinedthe need not only to have a model to describe the interactionmechanism between a surface wave and plasma but also to carryout a parametric investigation of the problem: for this purpose anumerical tool was developed to help the optimization of all theparameters involved in plasma antenna design.

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[21] O. A. Ivanov and V. A. Koldanov, “Self-consistent model of a pulsedair discharge excited by surface waves,” Plasma Phys. Rep., vol. 26,pp. 902–908, Oct. 2000.

Paola Russo (S’98–M’00) was born in Turin, Italy, in1969. She received the Ph.D. degree in electronic en-gineering from the Polytechnic of Bari, Italy, in April1999.

In 1999, she worked with a research contract atthe Motorola Florida Research Lab. From 2000 to2004, she worked with a research contract on the de-velopment of numerical tools applied to the couplingof electromagnetic field and biological tissue, and todifferent EMC problems, in the Department of Elec-tronics, University of Ancona (now Università Po-

litecnica delle Marche). Since January 2005, she is a Researcher at the Univer-sità Politecnica delle Marche, Italy, where she teaches EMC and antenna design.Her main research topics are on the application of numerical modeling to EMCproblem, reverberation chamber, and new antenna design.

Prof. Russo is a member of the IEEE EMC and AP societies and of the ItalianSociety of Electromagnetics SIEM.


Valter Mariani Primiani (M’93) was born in Rome,Italy in 1961. He received the “Laurea” degree inelectronic engineering in 1990.

Currently, he is an Associate Professor of electro-magnetic compatibility at the “Università Politecnicadelle Marche,” Ancona, Italy, where he is a memberof the DIBET Department, responsible for the EMCLaboratory. His area of interest in electromagneticcompatibility concerns the prediction of digital PCBradiation, the radiation from apertures, the ESD cou-pling effects modelling and the analysis of emission

and immunity test methods. More recently he has extended his research activityin the field of the application of reverberation chambers for compliance testingand for metrology applications.

Prof. Primiani is a member of the IEEE EMC and IM societies and of theItalian Society of Electromagnetics SIEM.

Graziano Cerri (M’93) was born in Ancona, Italy,in 1956. He received the Laurea degree in electronicengineering from the University of Ancona, in 1981.

In 1983, after military service in the EngineerCorp. of the Italian Air Force, he became an Assis-tant Professor in the Department of Electronics andControl, University of Ancona where, from 1992,he was an Associate Professor of microwaves in thesame Department, and is currently a Full Professorof electromagnetic fields in the DIBET Department,Università Politecnica delle Marche. His research is

mainly devoted to EMC problems, to the analysis of the interaction betweenEM fields and biological bodies and to antennas.

Prof. Cerri is a member of AEI (Italian Electrotechnical and Electronic Asso-ciation). Since 2004, he is the Director of ICEmB (Interuniversity Italian Centerfor the study of the interactions between Electromagnetic Fields and Biosys-tems). He is also a Member of the Administrative and Scientific Board of CIRCE(Interuniversity Italian Research Centre for Electromagnetic Compatibility), theScientific Board of CNIT (Interuniversity National Centre for Telecommunica-tions), and the Scientific Board of SIEm (Italian Association of Electromag-netics).

Roberto De Leo was born in Bari, Italy, in 1942. Hereceived the Laurea degree in electronic engineeringfrom the Politecnico di Torino, Turin, Italy, in 1965.

From 1966 to 1975, he was an Assistant Professorof electronics on the Faculty of Engineering, Univer-sity of Bari, Bari, Italy, where, in 1976, he was ap-pointed Full Professor of Microwaves. In 1980, hewas appointed Full Professor of electromagnetic fieldat the University of Ancona, Ancona, Italy, where, in1992, he became a Full Professor of electromagneticcompatibility. His scientific interests are devoted to

theoretical and experimental aspects of EMC.Prof. De Leo was an Associate Editor of the IEEE Transactions on Electro-

magnetic Compatibility. since 1976, he has been a Member of the ScientificCouncil of the Electromagnetic Group of the Italian National Research Council(CNR), and from 1989 to 1993, he was also the President of this Group. He isalso a member of the Scientific Board of SIEm (Italian Association of Electro-magnetics).

Eleonora Vecchioni was born in Macerata, Italy, in1981. She received the Laurea degree in electronicsengineering and the Ph.D. degree in electromag-netism from the Università Politecnica delle Marche,Ancona, Italy, in July 2006 and December 2009,respectively.

Her research interests include computationalelectrodynamics and plasma physics, in particularthe physical and numerical characterization of theelectromagnetic properties plasma. In January 2010,she was collaborating with the Dipartimento Di

Ingegneria Biomedica, Elettronica e Telecomunicazioni of Univpm, as anexternal collaborator and since June 2010, she is working in the Software R&DUnit, Thermowatt Company.