GB2508428A - Small tapered slot antenna using a magneto-dielectric material - Google Patents

Abstract

A tapered slot antenna 10 comprises one or more electrically conductive parts 12 forming the boundaries of a tapered slot 15 where the slot region between the boundaries includes a magneto-dielectric material 14. The magneto-dielectric material 14 has a relative permittivity and a relative permeability which is substantially equal to 3. The tapered slot 15 has a length of substantially 0.75 m and a mouth width which is substantially 0.5 m. The exponential taper rate of the slot 15 may substantially equal 0.9. The magneto-dielectric material 14 may have a thickness or about 31.4 mm. The electrically conductive parts 12 may be formed by two separate metal sheets or by conductive layers printed on to a circuit board 11. The magneto-dielectric material may be provided as a surface layer on a printed circuit board. The tapered slot antenna 10 may be used in an antenna array formation.

Description

REDUCED SIZE TAPERED SLOT ANTENNA USING A MAGNETO-DIELECTRIC

MATERIAL

Tapered slot antennas (TSA) have potential advantages such as ease of fabrication, wide bandwidth and high gain. These ad-vantages make them a suitable choice as antennas for a wide variety of applications such as airborne radar, communication systems and imaging systems (see for example the references "Ebnabbasi and others" and "Janaswamy and Schaubert" men- tioned below) . Tapered slot antennas are particularly suita- We for producing ultra-wideband signals. A further applica-tion includes the detection of conducting materials with a ground penetrating radar, Simple planar fabr.i cation on lay-ered dielectric substrates is feasible, and the tapered slot is often fed using microstrip line or stripline feed configu-rations. Different types of tapering such as linear, constant width, exponential, broken linear and dual exponential taper-r ing have been proposed in the past.

r TSAs are a class of end-fired travelling wave antennas radi -ating at the wider end of the slot. These structures provide wide-frequency bandwidths, often limited by the bandwidth of a balun feeding of the tapered slot section. The travelling wave propagation is achieved due to the fact that the phase velocity in tie radiator is less than the speed of light in free space. The phase velocity of wave propagating in a medi-um is vph l/sqrt(E*), where end g are the electrical oermitivJLy and the magnetic permeability of the medium, ro-spectively, and "sort" refers to the square root.

The permeability p is related to the vacuum permeabiiity via u = p0 * pr, wherein pr is defined as the relative permea-bility. Likewise, the permittivity a is related to the vacuum permittivity sO via a = a Q * a _r, wherein r is defined as the relative permlitivity. Standard textbooks on electro-dynamics provide a mote detailed explanation for the use of these definitions and the underlying assumptions (see for ex-ample J.D. Jackson, Classical Electrodynamics, John Wiley & Sons, New York, third edition, 1999, section 1.4, Maxwells equations in macroscopic matter) The values of i and a also define further material proper-ties. For exampie, an intrinsic impedance Z of the material is given by sqrt(p/a) . In a magneto-dielectric material, both a r and ur are different from their vacuum value of 1. In the current application, magneto-dielectric materials are considered fcr which both a r and r are greater than one.

Magneto-dielectric macerials generally have lower vph values than conventional dielectric materials. According to the pre-sent application, magneto-dielectric materials, which have lower phase velocity chan conventional dielectric substrates are used as substrates for ISAs. Currently, materials with magneto-dielectric properties have been realized for frequen-cies of at least up to 1GHz. However, the design principles of the present application can be extended to higher frequen-cies, when materials with magneto-dieiectric properties are realizable in the future.

In an antenna, the eiectromagnetic waves may travel only par- tially through a buik material with given values a, p. There- by, fringe effects occur which motivate the definition of ef-fective values aeff, peff. The values of aeff, ieff as well as the values of a, p are in general frequency depend-ent. Moreover, they may in general depend on a direction of propagation of an electromagnetic wave.

F. Oraizi, and S. Jam ("Oraizi and JamT) discloses a tapered slot antenna design in "Optimum Design of Tapered Slot Anten-na Profile", IEEE Trans. Antennas and Propagation, vol 51, no 8, 1 Aug 2003. P. J. Gibson ("Gibson") discloses an exponentially tapered slot antenna in "The Vivaldi Aerial", Proc. 9th European Microwave Conference. Brighton, U.K., 1979, pp.101-105.

J. Shin and D.H. Sohaubert ("Shin and Schubert") disclose an investigation of a Vivalid antenna in "A parameter study of stripline-fed Vivaldi notch-antenna arrays", IEEE Trans. An-tennas Propagat. vol. 47, no. 5, May 1999, pp. 879-886.

K. Ebnabbasi, D. Eusuioc, R. Birken, and M. Wang ("Ebnabbasi and others"), discloses designs of tapered slot antennas in "Taper Design of Vivaldi and Co-Planar Tapered Slot Antenna (TSA) by Chebyshev Transformer", IEEE Trans. Antennas Propa-cat., vol. 60, no. 5, May 2012, pp. 2252 -2259.

R. Janaswamy and U. H. Sohaubert ("Janaswamy and Schaubert") disclose impedance measurements of a slotline in "Character- istic impedance of a wide slotline on low permittivity sub-strates", IEEE Trans. Microw. Theory Tech., vol. MTT-34, no. 8, pp. 900-902, Aug. 1986.

R. Mueller, S. Lutz, R. Loroh, and T. Walter ("Mueller and others") disclose a Vivaldi antenna in "A UHF Ultrabroadband Vivaldi-Type Direction Finding Antenna", Proceedings of 2010 IEEE International Symposium on Antennas and Propagation, To-ronto, Canada, July 12-17, 2010.

N.y. Venkatarayau and Y. B. Can ("Venkataravalu and CanT) disclose an array of napered slot antennas in "Design of a Tapered Slot Array Ancenna for UIA'E Through-Wall RADAR", Pro-ceedings of 2010 IEEE International Symposium on Antennas and Propagation, Toronto, Canada July 12-17, 2010.

From the US 2011 00068991 it is known to use magneto-dielectric materials as substrates for reducing the size of patch antennas. In contrast to tapered slot antennas, howev- er, patch antennas are resonant antennas with narrow band-widths and using magneto-dielectric substances reduces the antenna bandwidth even further.

The US 2008 0055:76 discloses a particular broadband antenna structure with two radiators loaded with compound material cf polymer resin containing magnetic material powder that real- izes broadband characceristics at low freguencies. This an-tenna radiates in all directions and is not a traveling wave antenna.

The investigations of the current application are carried out on magneto-dielectric materials as the substrate in a typical Vivaldi antenna, similar to the one shown in "Oraizi and Jam". The tapered profile is described by an exponential curve presented in "Shin and Schaubert". The balun design or the feed network to excite the tapered slot section is not considered in the simulations. A commercial full-wave elec-tromagnetic simulation tool (CST-Microwave Studio) is used for the simulations. The tapered section of the antenna is considered as a bilateral siotline. The bilateral slot line supports a quasi-Transverse electromagnetic (TEN) mode. The propagation constant and characteristic impedance of a slotline are a function of the slotline width, thickness of the substrate and the material property of the substrate, no- tably the electrical permittivity sr and the magnetic permea- bility li r (see "Janaswarny and Schaubert") . The tapered sec-tion of the ISA is simulated assuming the taper to be a stepped slotline transformer, similar to the one shown in "Craizi and Jam".

In rarticilar, the current specification discloses a tapered slot antenna (ISA) having a tapered slot for guiding a tray-cling electrcmagnetic wave, wherein boundaries of the tapered slot are formed by one or more conducting parts. The one or more conducting parts comprise a conductive material such as a copper layer or some other metallic surface or plate.

A region between the boundaries of the slot comprises a mag-neto-dielectric naterial. According to the specification, the region between the boundaries of the throat, which extends at least from the beginning of a slot tapering to an opposite slot mouth, is essentially filled out with the magneto-dielectric material.

The ISA comprises a feeder antenna such as a strip line for radiating an electromagnetic wave into the area of the ta-pered slot. The feeder antenna is arranged in the region of a narrower end of the slot and is connected to a signal con-nector such as a plug for a coaxial cable for connecting the feeder antenna to an electromagnetic signal source.

Design parameters of the ISA are chosen such that a relative permittivity of the magneto-dielectric material is equal to 3 within a 10% margin, a relative permeability of the magneto-dielectric material is equal to 3 within a 10% margin, a length of the tapered slot is equal to 0.75 m within a 10% margin and a mouth width of the tapered slot is equal to 0.5 m within a 10% margin. Herein, an interval within a 10%:. mar-gin of a value has an upper boundary equal to the value plus 10% of its magnitude and a lower boundary equal to the value minus 10% of its magnitude.

A relative perrneabiliuy greater than 1 allows to reduce the size of the antenna while the choice of the length and mouth width can provide reflection characteristics comparable to a larger TSA antenna.

In oarticular, the width of the tapered slot increases from a narrower end of the slot towards a broader end or mouth off the slot. The TSA of The current specification is a traveling wave antenna, which progressively converts electromagnetic energy within a selecoed rage of frequencies into electromag-netic waves traveling from the narrower end to the broader end of the slot.

For providing desired reflection characteristics, the TSA may be tapered according co an exponential tapering, wherein an exponential taper rate of the tapered slot is equal to 0.9 within a 10% margin.

A thickness of the magneto-dielectric material is equal to 31.4 mm within a 10%: margin. This choice of thickness can re-duce fringe effects, for example.

In a more specific embodiment, the tapered slot antenna has an exponential tapering, wherein the relative permittivity of the substrate is equal to 3 within a 5 3 margin, the relative permeability of the substrate is equal to 3 within a 5% mar-cm, the length of the tapered slot antenna is equal to 0.75 m within a 5% margin, the mouth width of the tapered slot an-tenna is equal to 0.5 m within a 5% margin and the taper rate is equal to 0.9 within a 5 3 margin.

In a yet more speoifio embodiment, the tapered slot antenna has an exponential tapering, wherein the relative nermittivi-ty of the substrate is essentially equal to 3, the relative permeability of the substrate is essentially equal to 3, the length of the tapered slot antenna is essentially equal to C.75 rn, the mouth widnh of the tapered slot antenna is essen-tially equal to 0.5 m and the taper rate is essentially equal to 0.9.

The TSA may comprise a ground connector for connecting the one or more conduoting parts to a ground potential. The one or more conducting parts, which for the boundaries or edges of the slot may be formed by one or more conducting layers on a printed circuit board, which provides an efficient and cost effective way of producing the TSA.

The one or more conducting parts may comprise at least two separate parts. Thereby, they can be connected to different potentials and radiation characteristics may be adapted. In another embodiment, the at least two separate parts comprise metal sheets.

The TSA may furthermore comprise a printed circuit board, wherein the magneto-dielectric material is provided by a sub-strate material of the printed circuit board. This provides an efficient and cost effective way of providing the magneto-

B

dielectric material. In order to realize the abovementioned values of permittivity and permeability, the magneto-dielectric material may also comprise an array of small scale structures, for example an array of miniature antennas sich as open slit rings.

In another embodiment, the magneto-dielectric material may be provided by surface layer of the printed circuit board.

Furthermore, the application provides an array of the above- mentioned tapered sloc antennas, wherein the tapered slot an- tennas of the array are connected to an electromagnetic sig-nal source. Such an array may be provided to achieve higher input powers and/or a greater range of irradiation. The TSA array may be used for a ground or wall penetrating radar or for detection apparatuses for biological systems, for exam- ple. The smaller size of the TSA according to the specifica-tion can provide advantages such as a higher mobility of the TSA array or easier integration within existing equipment.

The subject of the present application is now explained in further detail with respect to the following Figures in which Figure 1 shows a top surface of an exponentially tapered slot antenna according to the application, Figure 2 shows a botrom surface of the antenna of Fig. 1, Figure 3 shows different shapes of tapered slot antennas, Figure 4 shows an electric field distribution of a quasi TEM mode on a bilateral slotline, Figure 5 shows slotline impedances for different substrate properties, Figure 6 shows a scactering coefficient S_il for Vivaldi ta-pered slot antennas with and without reduced lengths, Figure 7 shows port signals for exponentially tapered slot antennas winh and without reduced leneths, Figure 8 shows a scartering coefficient S_il for Vivaldi an- tennas with reduced length and modified taper pro-files, and Figure 9 shows port signals for exponentially tapered slot antennas wich reduced length and modified taper profiles, Figure 10 shows an array of exponentially tapered slot anten-nas (E?SA) Figure 11 shows an E-plane radiation pattern of an EISA ac-

cording to rhe specification, and

Figure 12 shows an H-plane radiation pattern of an EISA ac-

cording to rhe specification.

In the following specification, details are provided to de- scribe the embodiments of the application. It shall be appar-ent to one skilled in the art, however, that the embodiments may be practised without such details. For example, a tapered slot of the antenna may be provided between two separate con- ducting layers or between two separate conducting parts in-stead of being provided as a out-out of a single conducting layer. The feeder strip may be provided with or without a stub and the antenna slot may be provided with or without a terminating oiroular cavity. Among others, a coupling to an high frequency (HF) input may be realized differently from the shcwn embodinents.

In the context of the current specification "HF" refers to a frequency range of the tapered slot antenna. The frequency range may for example comprise a sub-Gigahertz range from 300 MHz -1GHz but also higher frequency ranges.

Fig. 1 shows a top side of a tapered slot antenna 10 accord-ing to the present application and Fig. 2 shows a bottom side of the tapered slot antenna 10. The tapered siot antenna 10 comprises a double-sided printed circuit board (PCB) 11. The double sided PCE 11 comprises a first conducting layer 12 on a top surface of the double-sided PCB 11 and a second con-ducting layer 13 on a bottom surface of the double-sided POB 11. The first and second conducting layers 12, 13 are provid-ed on a ground plate 14. The ground plate 14 is made of a magneto-dielectric substrate having a relative permeability pr that is greater than one and a relative perrnittivity £r i5 that is greater than one.

On the top surface of the PDB board, a tapered slot shape 15 is etched out of the conductive layer of the top surface. The tapered slot shape comprises a tapered slot section 16, a throat section 17 and a circular cavity section 18. A shape of the tapered slot section if defined by y(x) = c1exp(Rx) + 02, wherein the y-axls excends along a longitudinal direction of the slot and the x-axis extends perpendicular to the y axis in a plane of the slon. The constants ci and c2 are chosen such that the slot width at the throat is y(xi) = yl and the slot width at the mouch is y(x2) = y2, wherein yl and y2 are predetermined width values, x2 -xl is a predetermined length L of the tapered slot and R is a predetermined rate of taper.

Fence, Y2 -Yi Cl = exp(Rx2) -exp(Rx1) and -y1exp(Rx2) -y2exp(Rx1) C2 -exp(Rx2) -exp(Rx1) The mouth width y2 is also referred to as W. The start Fl(xl,yl) point and the end point P2(x2,y2) are shown in Fig. 1.

The first conducting layer 12, which limits the slot, is sol-dered to a shield cylinder 20 of a coaxial plug 19 by solder joints 21.

On a rear side of the double-sided FOB 11, a conductive strip 22 is provided such that it crosses the projection of the slot throat 17 to the rear side in a right angle. A first end of the conductive strip 22 terminates in a radial stub 23, which has an opening angle of 90 degrees, and a second end of the conductive strip 22 is soldered to a core of the coaxial plug by a solder joinc 25.

In operation, the core 24 of the coaxial plug 19 is connected to a HF source and the shield cylinder 20 is connected to a ground potential, as indicated by the symbols in Fig. 1. The portion of the strip 22 that crosses the throat of the slot acts as a dipole antenna, which radiates into the throat of the slct. The generated electromagnetic travels from the throat to the mouth of the slot where it is radiated away.

Several tapered slot antenna (TSA) types exist according to the shape of tapering. Some examples of these types are shown in Fig. 1, a) -e), in which a) shows a linearly tapered slot antenna (LTSA), b) shows a Vivaldi or exponentially tapered slot antenna, c) shows a constant width slot antenna (CWSA) and e) shows a Fermi capering and d) shows a piecewise con-stant width tapering. The exponentially tapered slot antenna may comprise different sections along the x-axis that are ta-pored according to different exponential dependencies. The boundaries of the slots may also comprise corrugations in or-der to reduce edge diffractions.

In the examples nentioned below, the tapered slot antennas are characterized by design parameters such as the slot length I, the mouth width W, the rate of taper R and the ma-terial constants sr and pr. Except for the rate R of taper these parameters also apply to more general antenna shapes, such as the cnes shown in Fig. 3 and 5. Moreover, the rate of taper can be generalized to the case of a linearly tapered antenna.

For the simulations, the design parameters are chosen as fol-lows: Parameter Values Slot Length, L 1 m or 0.75 m Mouth Vcidth, W 0.75 in or 0.5 m 1 or 3 pr 1 or 3 R 0.6 or 0.9 Furthermore, for those simulations of the present application for which a r or i r are different from their vacuum value 1 the dielectric material or the magneto-dielectric material has a substrate thickness of 31.4 mm.

The tapered section is viewed as an impedance transformer from the impedance of the slotline at the feed region to a load impedance which is much larger and amounts to multiples of the free-space wave impedance (see TEbnabbasi and oth-cr5"). As a first step to investigate the effect of using magnetc-dielectrtc maccrisis as substrates for such tapered slot antennas, the dependence of the characteristic impedance Z_s of a slotline on rhe width of the slot line as well as on the material properties of the substrate is simulated. The simulation results are shown in Fig 5.

According to the simulation results, (a) for any given slorline width, Zs is proportional to a power of u and inversely proportional to a power of s. This is in agreement with rhe fact that for a typical transmission line the characteristic impedance, = cff/Fcff where peff and ceff are the effective permittivity and per-meability of the transmission line medium, (b) for a given set of material properties the characteristic impedance ZO increases with increase in the slot width W. The increase in width of the slot reduces the capacitance in the equivalent ctrcuic of the transmission line and hence in-creases the characteristic impedance, (c) the rate of change of Z_s with respect to the width of the sict is lower for higher permittivity than in the free-space case, and (d) the rate of change of Zs is higher for cases of higher permeability than in The free-space case.

Faving a higher rate of change of Zs with respect to slot-width provides the advantage that the length of the tapered section in the TSA can be reduced. Due to the result (d), having a substrate wirh a magnetic property along with a die-lectric property gives the advantage that Zs varies faster with the increase in The width of the slotline and hence the length of the tapered section in the TSA can be reduced.

The set of design parameters are chosen with the objective of achieving a good performance around the 3COM MHz -15Hz band - In particilar, the parameters can be chosen such that the re-flecticn coefficient is lower than -10 dB for this frequency band, in order to achieve a performance that is similar to the original design without magneto-dielectric material.

As a first test case, which is shown in Fig. 6, the scatter-ing coefficient S_li for the free-space case with ar = 1.0 and pr = 1.0 is compared with the case of a magneto- dielectric material with Er = 3.0 and ir = 3.0. For the ex-amples of Fig. 6 and 7, the mouth width 14 is 0.75 m and the taper rate R is 6.0.

The scattering coefficient 511, which is shown in Figs. 6 and 8 as a function of frequency, is an example of a scatter- ing or S-parameter. Scattering parameters are used for de-scribing the behaviour of linear electrical components and networks for small signals. In Figs. 6 and 8, a lower boind of a frequency range of interest between 600 MHz and 1 G]z is indicated by an arrow next to the x-axis.

S-parameters are used for computations in high frequency technology and are primarily important for measurement tech-nology, as S-parameters ara acquired by measuring the wave impedance, which is present between connections of a device under test (OUT) during normal operation. Thereby, it is pos- sible to avoid undesired impedance transformations at the in-and outputs of the OUT, which are due to the measuring lines.

The nurrber of S-parameters is equal to the number of device ports to the square. For describing a one-port device, as shown in Figs. 1 and 2, a single S parameter is sufficient.

The S parameters do not describe the conditions at the port in terms off the applied instantaneous voltage and current but rather in terms of incident and reflected waves.

With ZO referring to the impedance of the measuring device (50 U in the present case) and Zn referring to the impedance at the n-tb port of a DUT, a reflection factor rn can be de-fined as Zn -Zo For a one port device, the reflection factor r is equal to the single S-parameter 511. The reflection factor is related to the standing wave ratio (SWR) In practice, the S-parameters are determined with network an- alyzers as a function of frequency. The S-parameters are di-mensionless complex numbers, wherein the modulus is usually indicated in decibel (dE) and the phase in degrees (°) . The wave impedance is conventionally set to 50 U. The transmission coefficients are often represented in a Car-tesian diagram while for reflection coefficients as Smith chart is often preferred. Thereby, the impedance of the DLTT can be inspected and rhe matching optimized. 511 indicates the impedance matching of the input. It is a measure of the matching quality to a reference system (conventionally 50 Ohm or 75 Ohm) . low value indicates only weak reflection of an input signal.

Three different cases are compared in Fig. 6: a. Er = 1.01, pr = 1.0 and I = 1 m, b. sr = 3.0, pr = 3.0 and L = 1 m, and c. £ r = 3.0, p r = 3.0, L = 0.75 m.

Comparing case (a) with case (b) , it is observed that in gen-eral there is a downward shift in the frequency response from free-space case due to the magnet-dielectric substrate used.

This frequency shift of approximately 0.1 GHz is indicated in Fig. 6 by an arrow. Due to the downward shift, the physical dimensions of the antenna can be reduced while achieving SElL-ilar performance as in the free-space case in terms of the frequency band of operation. This is demonstrated by compar- ing against case (c) which uses the magneto-dielectric mate- rial and has a reduced slot length. Indeed the frequency re-sponse shifts back to that of the free space case.

Fowever, the magnitude of the reflection coefficient increas-es for case (c) . The reason for this is better understood by analysing the tine domain signal at the antenna port shown in Fig. 7. Two distinct rime events are observed in the port signals in the domain, which are: P. Reflections occurring at the start of tapering along the exponentially tapered slot and B. Reflections occurring due to the impedance discontinuity at the end of the tapered section and free space.

The following cbservarions can be made: 1. the reflections B occur later in time for design case (b) due to the fact that with the use of a magneto-dielectric ma- terial the phase velocity is reduced which results in a long- er time for the signal to travel across the length of the ta- pered slot. This time shift is indicated in Fig. 7 by an ar-row, ii. by reducing the length of the tapered slot section (de-sign case (c) ) , the reflections occur around the same time as that in the free-space case. The decrease in the phase veloc-ity by using magneto-dielectric substrate effectively makes it possible to decrease the length of the tapered section, and ill. in case (c) reflections at the start of the tapering are higher than for the free-space case. The use of magneto-dielectric material substrates while using the same tapered profile as fcr the free-space case results in different mi-pedance variations compared to the free-space case.

According to the present application, a redesign of the ta-pered section in terms of width (w) and rate of taper (PD on top of a reduction in length is made in order to reduce the reflections.

To analyse the effects of changes in the width and rate of taper R while using magneto-dielectric substrates, three dif-ferent design cases (all with L = 0.75 m) are compared: d. Er = 3.01 pr = 3.0, w =0.75 in and R = 0.6, e. er = 3.0, pr = 3.0, w = 0.5 in and R = 0.6, and f. £ r = 3.0, i r = 3.0, w = 0.5 in and B = 0.9.

By changing the width alone (case d and e) the impedance var-iation that the tapered section presents to the travelling wave changes and along with it the leaky behavicur of the travelling wave. For chis reason, the change with dimensions in general (for length L and width W) is compensated with the change in the rate of taper, A (case f) . Fig. 8 illustrates that fcr design case (f) the reflectivity Sil is smoothened out and in general lower than for design cases (d) and (e) Furthermore, in the time-domain port signal shown in Fig. 9 the reflecticns of type A are significantly lower for case (f) compared to case (e) A tapered slot antenna with a magneto-dieleotrio material ao-oording to the present applioation may, among others, provide the following advantages: 1. a new design parameter, the magnetio property of the sub-strate is introduoed whioh allows greater flexibility in the design, 2. the physioal length of the tapered seotion oan be reduoed.

Along with this advantage, the width of the tapered seotion oan as well be reduoed, leading to an overall size-reduotion of the TSA. This is desirable, espeoially for low frequenoy applioations, and 3. Additional effeots in the radiation pattern in terms off cain direotivity and beam width are expeoted. However, the variations in pattern charaoteristios due to ohanges in di-mensions are similar, irrespeotive of the material properties of the substrate.

The reduotion in width leads to an additional advantage when using suoh a TSA as a unit element in a phased array. More unit elements oan be used in a given area leading to an in-orease in the array gain and direotivity.

Fig. 10 shows an example of an array of exponentially tapered slot antennas whloh are eaoh made up of separate metal parts.

Fig. 11 shows H-plane radiation patterns of the ETSA of de-sign oase f and Fig. 12 shows an H-plane radiation pattern of the exponen-tially tapered slot antenna for design oase f.

In Figs. 11 and 2 a radiation pattern at 500 MHz is indicat- ed by a solid line and a radiation pattern at 800 MHz is in-dicated by a dashed line.

Reference tapered slot antenna 11 double sided PCB 12 first conducting layer 13 second conducting layer 14 ground plate/substrate tapered slot shape 16 tapered slot secrion 17 throat section 18 cavity section 19 coaxial plug shield cylinder 21 solder joints 22 conductive strip 23 radial stub 24 core of coaxial plug solder joint

Claims (12)

1. CLAIMS1. Tapered slot antenna, comprising -a tapered slot for guiding a traveling electromagnetic wave, wherein boundaries of the tapered slot are formed by one or more conducting parts, the one or more con-duoting parts comprising a conductive material, and wherein a region between the boundaries of the slot corn-prises a magneto-dielectric material, -a feeder antenna for radiating an electromagnetic wave into the area of the tapered slot, -a signal connector for connecting the feeder antenna tc an electromagnetic signal source, wherein a relative permittivity of the magneto-dielectric material is equal to 3 within a 101 margin, a relative permeability of the magneto-dielectric material is equal to 3 wiThin a 10% margin, a length of the ta-pered slot is equal to 0.75 m within a 10% margin and a mouth width of the tapered slot is equal to 0.5 m within a 10% margin.
2. 2. Tapered slot antenna according to claim 1, wherein the tapered slot is capered according to an exponential ta- pering, and wherein an exponential taper rate of the ta-pered slot is equal to 0.9 within a 10% margin.
3. 3. Tapered slot antenna according to claim 1 or claim 2, wherein a thickness of the magneto-dielectric material is equal to 31.4 mm within a 10% margin.
4. 4. Tapered slot antenna according to one of the preceding claims, the tapered slot antenna having an exponential tapering, wherein the relative permittivity of the sub-strate is equal no 3 within a 5 1 margin, the relative permeability of The substrate is equal to 3 within a 5%.margin, the lengTh of the tapered slot antenna is equal to 0.75 m within a 5% margin, the mouth width of the ta-pered slot antenna is equal to 0.5 m within a 5% margin and the taper rare is equal to 0.9 within a 5 1 margin.
5. 5. Tapered slot antenna according to one of the preceding claims, the tapered slot antenna having an exponential tapering, wherein the relative permittivity of the sub- strate is essentially equal to 3, the relative permea-bility of the substrate is essentially equal to 3, the length of the tapered slot antenna is essentially equal to 0.75 m, the mouth width of the tapered slot antenna iS is essentially equal to 0.5 m and the taper rate is es-sentially equal no 0.9.
6. 6. Tapered slot antenna according to one of the preceding claims, comprising a ground connector for connecting the one or more conducting parts to a ground potential.
7. 7. Tapered slot antenna according to one of the preceding claims, wherein The one or more conducting parts are formed by one or more conducting layers on a printed circuit board.
8. 8. Tapered slot antenna according to one of the claims 1 to 4, wherein the one or more conducting parts comprise at least two separare parts.
9. 9. Tapered slot antenna according to claim 8, wherein the at least two separate parts comprise metal sheets.
10. 10. Tapered slot antenna according to one of the preceding claims, comprising a printed circuit board, wherein the magneto-dielectric material is provided by a substrate material of the printed circuit board.
11. II. Tapered slot antenna according to one of the claims 1 to 9, comprising a printed circuit board, wherein the mag-neto-dielectric material is provided by surface layer of the printed circuit board.
12. 12. Array of tapered slot antennas according to one of the preceding claims, wherein the tapered slot antennas of the array are connected to an electromagnetic signal source.