EP0889543A1 - Wide band printed dipole antenna for microwave and mm-wave applications - Google Patents
Wide band printed dipole antenna for microwave and mm-wave applications Download PDFInfo
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- EP0889543A1 EP0889543A1 EP97110679A EP97110679A EP0889543A1 EP 0889543 A1 EP0889543 A1 EP 0889543A1 EP 97110679 A EP97110679 A EP 97110679A EP 97110679 A EP97110679 A EP 97110679A EP 0889543 A1 EP0889543 A1 EP 0889543A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/061—Two dimensional planar arrays
- H01Q21/062—Two dimensional planar arrays using dipole aerials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
- H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
- H01Q19/108—Combination of a dipole with a plane reflecting surface
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
- H01Q5/40—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
- H01Q5/48—Combinations of two or more dipole type antennas
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
Definitions
- the present invention relates to an antenna according to the preamble of claim 1.
- Such a dipole antenna is known from US-PS 5021799.
- This US-patent discloses a dipole antenna, in which the first line and a second line of a microstrip transmission line means are tapered to provide a microstrip-to-balanced line impedance transformation. Further on, the first and the second line are separated in the direction of the dielectric substrate middle plane, form an electric field and provide an impedance transformation from an unbalanced line part of the microstrip transmission line means to first and second balanced dipole antenna elements. Therefore, in the antenna disclosed in US-PS 5021799, the transformation from unbalanced to balanced transmission is conducted within microstrip transmission line means of the dipole antenna.
- this antenna is inherently selective (not wide band) due to the classic dipole microstrip structure. Further on, this known antenna is tolerance sensitive. The thickness of the substrate of this known antenna is 0.0125 wavelength, that would lead for the 60 GHz range to a thickness of 0.0625, which is very thin and critical to be manufactured and handled. However, due to the specific structure of the dipole antenna disclosed in US-PS 5021799, the dipole antenna can be mainly applied for narrow band applications. The manufacturing tolerances, increased losses in dielectric material, decreasing of the substrate thickness, supporting the substrate with the same distance to the reflector plane, as well as possible appearance of the high order modes limits its application in the lower microwave range (3-30 GHz).
- US-PS 4737797 discloses a dipole antenna without a reflector plane.
- This dipole antenna comprises a transmission part within the microstrip transmission line means, in which signals are converted from an unbalanced line to a balanced line to permit the signal to be radiated by first and second balanced dipole elements.
- the dipole antenna disclosed in US-PS 4737797 exhibits a wide band width up to 1.7 GHz (about 30 %).
- the dipole antenna does not allow applications up to the millimeter wave range, because of very critical tolerances (thin traces) for balun-circuits and very thin substrates (like 0.024 mm for 60 GHz), where a physical support of the structure (robustness) and availability of such small dielectric thickness is questionable.
- the object of the present invention is to provide an antenna according to the preamble of claim 1, which allows applications deep into millimeter wave frequencies within a very large band width with a good efficiency.
- the antenna according to the present invention comprises a dielectric substrate including a front and a back dielectric face, at least one dipole means comprising a first and a second element for radiating and receiving electromagnetic signals, said first element being printed on said front face and said second element being printed on said back face, metal strip means for supplying signals to and from said dipole means, said metal strip means comprising a first line printed on said front face and coupled to said first element and a second line printed on said back face and coupled to said second element, and reflector means spaced to and parallel with said back face of said dielectric substrate, a low loss material being located between said reflector means and said back face and having a dielectric constant less than 1, 2, being characterized in that said first and said second lines are balanced and arranged parallel and opposite to each other on said front and back dielectric face, respectively.
- the antenna according to the present invention has a very large band width and allows applications deep into the millimeter wave frequency range. Further on, the antenna according to the present invention can be fabricated at very low production costs, e.g. due to the utilization of a simple planar technology, utilization of a printed technology and/or simple and cheap photolithographic processing of the prints. Further on, the antenna according to the present invention can be produced with a small size and a high reproducibility due to a low tolerance sensitivity of the dipole antenna. Also, a simple integration with planar RF-assemblies is possible, since it is assumed that future microwave and millimeter wave technologies will be based on planar assemblies rather than waveguide technology.
- a big advantage of the antenna according to the present invention is the possibility to use the same antenna for different kinds of communication systems even at different frequency bands of interest.
- Possible identified mass market applications are e.g. broad band home networks, wireless LAN, private short radio links, automotive millimeter wave radars, microwave radio and TV distribution systems (transmitters and ultra low cost receivers).
- Some of the identified frequency bands of interest are: 5 GHz, 10.5 GHz, 17-19 GHz, 24 GHz, 26-27 GHz, 28 GHz, 40 GHz, 51 GHz, 59-64 GHz, 76 GHz and 94 GHz.
- the antenna according to the present invention satisfies the following general requirements, namely has a specific radiation pattern, a good matching in the frequency band of interest and a good efficiency in the frequency band of interest.
- the antenna according to the present invention has a very large band width of more than 30 % working range compared to known microstrip dipole antennas. Therefore, a same antenna according to the present invention can be used for different systems and different applications. Further on, the production tolerances of different parts of the antenna according to the present invention are much less critical than for known microstrip dipole antennas, which is very important for the frequencies in the microwave and the millimeter wave ranges. Due to its particular structure, the antenna according to the present invention has lower losses and sensitivity to higher order modes propagation at higher frequencies (microwave range) and mm-wave range compared to known microstrip dipole antennas.
- the manufacturing particularly for millimeter wave frequency ranges is much less critical.
- the higher unwanted higher order modes in the case of the microstrip line appear at lower frequencies compared to a balanced microstrip line printed on a substrate with the same thickness.
- the influence of the feeding network on the radiation pattern is much lower, due to the balanced microstrip feeding line structure, than in known microstrip dipole antennas.
- the required dielectric substrate thickness for an optimum working scenario small losses in wanted radiation pattern
- the thickness of the dielectric substrate is not so critical for the antenna according to the present invention, so that the antenna according to the present invention is easier and cheaper to produce.
- a further very large advantage of the antenna according to the present invention is the feasible maximum frequency of operation, which can be achieved by producing the antenna with commercial low cost photo lithography technology.
- the feasible maximum frequency of the antenna according to the present invention is 94 GHz and 140 GHz with a dielectric thickness of about 50 ⁇ m (commercially available) and an advanced photolithographic technology.
- the feasible maximum frequency of known microstrip dipole antennas is 40 GHz and 60 GHz with a very advanced technology and problems in reproducibility. Therefore, the antenna according to the present invention provides a low cost wide band dipole antenna having not critical tolerances particularly suitable for microwave and millimeter wave applications.
- the low loss material is a supporting structure supporting said reflector means and said back face.
- the antenna according to the present invention can comprise a plurality of dipole means, each comprising a first and a second element supported by said front face and said back face, respectively, said first and second line respectively comprising a plurality of first and second line portions, said first and second line portions respectively being connected to each other by T-junctions, said first elements pointing in a first direction and said second elements pointing in a second direction opposite to said first direction.
- An antenna having a plurality of dipole elements has a higher gain than an antenna with one or only a few dipole elements.
- the antenna input impedance is treated and matched in the way of having 100 Ohms in the whole frequency band.
- the impedance transformation is done by increasing the width of each of the line portions.
- each of said first and second line portions can be tapered between two adjacent T-junctions, so that the width of each line portion increases towards said first and second elements, respectively, to provide an impedance transformation in the succeeding T-junction.
- the width of each of the line portions can gradually increase to provide an impedance transformation of a ratio 1:2 in the succeeding T-junction.
- the line portions can be tapered corresponding a linear, exponential or polynomial function.
- the length of said first and second elements is respectively smaller than 0,5 ⁇ the mean width w of the respective element is smaller than 0,35 ⁇ and the width c of a contact area between said respective element and said first or second line coupled to said respective element is smaller than 0,1 ⁇ , whereby ⁇ is the free space wavelength of the center frequency of the band of interest, the angle between the respective line and each of the adjacent sides of the respective element being larger than 10 degrees.
- said first and second elements can have a structure comprising at least three corners, whereby said contact area is one of said corners.
- said first and second elements have a pentagonal shape.
- the antenna of the present invention has a transition element coupled to said first and second lines to provide a transition between said first and second lines and a waveguide for guiding signals to and from the antenna, said transition element comprising first teeth elements coupled to said first line and second teeth elements coupled to said second line, said first teeth elements pointing in a first direction and said second teeth elements pointing in a second direction opposite to said first direction, said first and said second direction being perpendicular to said first and second lines.
- Figure 1 shows a schematic upper view of an antenna according to the present invention, with a projection of metal strip means 7 and a plurality of dipole means 4 from a front face 2 and a back face 3 of the dielectric substrate means 1 in a common plane.
- the first elements 5 of the dipole means 4 are printed on the front face 2 of the dielectric substrate means 1 and the second elements 6 of the dipole means 4 are printed on the back face 3 of the dielectric substrate means 1.
- the first elements 5 are connected to each other with a first line 8 supported by the front face 2 for supplying signals to and from the first elements 5.
- the second elements 6 are coupled to each other with a second line 9 supported by the back face 3 for supplying signals to and from said second elements 6.
- the first line 8 and the second line 9 building the metal strip means 7 have a balanced microstrip structure and are connected to a waveguide transition element 12 near the edge of the dipole antenna to provide a transition between the balanced lines 8 and 9 to a waveguide supplying the signals to be radiated by the dipole means 4.
- the waveguide transition element 12 consists of two parts connecting each of the lines 8 and 9 to a waveguide.
- Each of the two parts of the waveguide transition element 12 comprises a plurality of teeth elements arranged perpendicular to the direction of the lines 8, 9 on the front face 2 and the back face 3, respectively. It is to be noted, that future commercial communication systems in microwave and millimeter wave ranges will be based on planar technology, so that other kinds of transition elements will be needed.
- the waveguide transition element 12 is important for the shown example due to the lack of a planar front end.
- first line 8 and the second line 9 respectively printed on the front face 2 and the back face 3 each split into two branches by means of a T-junction 15 located approximately in the middle of the dipole antenna. From the first T-junction 15 located approximately in the middle of the dipole antenna, succeeding T-junctions 15 being respectively rectangular to each other split the first line 8 and the second line 9 into a respective plurality of first line portions 13 and second line portions 14. Each line portion 13 is connecting two adjacent T-junctions 15 and each second line portion 14 is also connecting two adjacent T-junctions 15.
- each dipole means 4 comprises a first and a second element 5, 6 for radiating and receiving electromagnetic signals transmitted by the first line 8 and the second line 9.
- the first elements 5 are printed onto the front face 2 of the dielectric substrate 1 and the second elements 6 are printed onto the back face 3 of the dielectric substrate 1.
- the first and the second elements 5, 6 respectively extend generally perpendicular to the first or second line portion 13, 14 they are connected with.
- first elements 5 are pointing in a first direction and the second elements 6 are pointing in a second direction which is opposite to that first direction, as can be seen from figure 1.
- the preferred shape of the first and the second elements 5 and 6 is a pentagonal shape.
- first line portions 13 and the second line portions 14 between adjacent T-junctions 15 are tapered to provide an impedance transformation in the succeeding T-junction located in direction to the dipole means 4.
- the first and second line portions 13, 14 are tapered, so that the width of each line portion 13, 14 increases towards that first and second elements.
- FIG 2 the schematic perspective view of a portion of the antenna shown in figure 1 having two dipoles is shown.
- the antenna comprises a substrate 1 having a front face 2 and a back face 3.
- the first elements 5 are printed on the front face 2 and the second elements 6 are printed on the back face 3.
- the first lines 8 are printed on the front face 2 and the second lines 9 are printed on the back face 3.
- only two dipole means 4 are shown, which are fed by first and second lines 8, 9.
- the T-junction 15 between the two shown dipole means 4 is fed by a first line portion 13 on the front face 2 and a second line portion 14 on the back face 3.
- the first and the second line portion 13, 14 are tapered with an increasing width towards the dipole means 4.
- the tapering provides an impedance transition from 100 ⁇ at the narrow part of the first and the second line portion 13, 14 to 50 ⁇ at the large part of the first and the second line portion 13, 14.
- the first and second line portion 13, 14 are split into the not-tapered end portions of the first and the second line 8, 9 leading to the dipole means 4.
- the low loss material 11 between the dielectric substrate 1 and the reflector means 10 is chosen to have minimum losses and a dielectric constant less than 1.2.
- the low loss material 11 is a supporting structure supporting said reflector means 10 and said dielectric substrate on its back face 3.
- the loss material 11 can be air, so that a free space exists between the dielectric substrate 1 and the reflector means 10.
- the low loss material is a polyurethane foam.
- the low loss material can be any other material with a dielectric constant less than 1.2.
- the thickness of the antenna can be influenced.
- dashed lines are used to show the second element 6 and the second line 9 being printed on the back face 3 of the dielectric substrate 1.
- FIG 3 a cross section of an antenna according to the present invention is shown.
- a first element 5 is printed on the front face 2 of the dielectric substrate 1
- the second element 6 is printed on the back face 3 of the dielectric substrate 1.
- the dielectric substrate with the second elements 6 and the second lines 9 printed thereon is supported by a low loss material 11 building a supporting structure.
- a reflector means 10 is located on the face of the low loss material 11 opposite to the back face 3 of the dielectric substrate 1.
- the reflector means shown is a reflector plate parallel to said back face.
- the distance d between the upper face of the reflector means 10 and the middle of the dielectric substrate 1 is about one fourth of the electrical wave length ⁇ of the central frequency (middle of the working band) within the low loss material dealing as a support structure between the dielectric layer 1 and the reflector means 10.
- the distance d is ⁇ / (4 ⁇ sqrt ( ⁇ r )) ⁇ 10% , wherein ⁇ r is the dielectric constant of the low loss material.
- a slight change of the distance d can cause special effects in the radiation pattern of the dipole antenna, which are sometimes wanted.
- the antenna of the shown embodiment has a planar shape, whereby other shapes of the antenna according to the present invention might be used.
- FIG 4 a cross section of the dielectric substrate 1 with the first line 8 and the second line 9 printed on the front face 2 and the back face 3, respectively, is shown.
- the first line 8 and the second line 9 are balanced and arranged parallel and opposite to each other on the front and the back face 2, 3, respectively.
- the width and the shape of the first line 8 and the second line 9 are the same.
- the whole feeding network in form of the metal strip means 7 is realized by balanced metal strip lines being parallel and opposite to each other.
- the symmetry axis of the first line 8 and the second line 9 lies within the middle plane of the dielectric substrate 1.
- the antenna according to the present invention can have one or more dipole means 4.
- the antenna according to the present invention comprises a plurality of dipole means 4
- T-junctions 15 are provided to distribute the signals to and from the plurality of dipole means 4.
- the T-junctions 15 of the first line 8 and the second line 9 are also balanced T-junctions and respectively arranged parallel and opposite to each other on said front and back face 2, 3, respectively. Further on, the T-junctions can be provided with a triangular gap in order to compensate the influence of the junction discontinuity, as can be seen e.g. in the T-junction 15 shown in figure 2.
- a transmission line transition between the balanced metal strip lines according to the present invention to the transmission line technology of the front-end is necessary.
- waveguide technology is used in the front-end, a waveguide transition element 12 shown in figure 1 can be used.
- the front-end utilizes a microstrip technology, a microstrip to balanced microstrip transition should be used.
- the front-end utilizes a coplanar waveguide technology, a coplanar waveguide to a balanced microstrip transition has to be used.
- the front-end utilizes coaxial lines, a coaxial connector to balanced microstrip transition has to be used.
- a first line portion 13 is shown to explain the tapered shape of the line portions between two adjacent T-junctions 15.
- the small end 16 of the shown line portion is connected to a T-junction 15 in direction to a transition element, e.g. the waveguide transition element 12 shown in figure 1, whereas the long side 17 is connected to a T-junction 15 in direction to the dipole means 4.
- the width of the side portion increases from the small end 16 to the large end 17 to provide an impedance transformation from 100 ⁇ to 2 ⁇ 50 ⁇ in the T-junction connected with the long end 17.
- the width of the line portion gradually increases to provide an impedance transformation of a ratio 1:2 in the succeeding T-junction 15.
- the tapering of the balanced line portions 13 and 14 is actually smooth, whereby the width of the lines on the front face 2 and the back face 3 of the dielectric substrate 1 is changed simultaneously. A change of the width of the line portions changes the impedance of the transmission lines. The above statements are equally true for the second line portions 14.
- the side portions 18 and 19 of the line portions can change with a linear function, as in the example shown in figure 5.
- the side portions 18 and 19 can change with an exponential function or a polynomial function including a "Chebisshev Polinom".
- the choice of the respective tapering function depends on the respective working frequency and is made to have a minimal reflectivity in the line portions.
- the tapering of the line portions is advantageous over the known quarter-wave transformers because of the high frequency selectivity and high tolerance dependency of the quarter-wave transformer.
- the balanced metal strip structure is advantageous over known microstrip structures, since transitions to other printed structures over waveguides, e.g. in a front-end, can be obtained much easier.
- using a dielectric substrate 1 with a constant thickness the higher order modes propagation, which is a very undesired effect, appear in known unbalanced microstrip lines at lower frequencies than in the balanced metal strip lines according to the present invention.
- the first and second elements 5, 6 have a structure comprising at least three corners and one of the corners is the contact area between the respective line portion 13 or 14 and the element 5 or 6.
- the element 5 or 6 has four corners with two long sides adjacent to the corner building the contact area and two short sides opposite to said two long sides.
- the element 5 or 6 has three corners.
- the element 5 or 6 has eight comers having two long opposite sides, respectively two middle sides adjacent to said long sides, and two short sides opposite to each other and rectangular to said long sides. One of the two short sides is the contact area to the respective line portion, as can be seen in figure 6 d.
- the length l of said first and second elements 5, 6 is respectively smaller than 0.5 ⁇
- the mean width w is smaller than 0.35 ⁇
- the width c of a contact area between said respective element and said first or second line 8, 9 coupled to said respective element is smaller than 0.1 ⁇ , wherein ⁇ is a free space wavelength of the centered frequency band of interest.
- the mean width w is defined as the width of the respective element 5, 6 at the half of the length l, as can be seen in figure 6.
- the contact area width c is zero, since one of the corners of the respective elements 5, 6 is the contact area, whereas in figure 6 d, the contact area width c is the length of one of the short sides of the element 23.
- the angle ⁇ between the respective line 8, 9 and the sides of the element adjacent to said contact area is preferably larger than 10°.
- Elements 5, 6 with shapes as shown in figure 6 and having the above defined characteristics are elements 5, 6 which can successfully work in frequency bands of at least 30 %, typically 40 - 50 %, related to the center frequency, having a VSWR less than 2. It is to be noted, that such elements 5, 6 can cover with a VSWR less than 2,5 even more than one octave.
- a phase array assembled by dipole antenna elements according to the present invention designed to work at a center frequency of 60 GHz preferably has 64 dipole means, a dielectric substrate with a thickness of 0.127 mm and a dielectric constant of 2.22 (Teflon-fiber-glass), a metallization thickness for the printed lines and elements of 17 ⁇ m, a low loss material of polyurethane with a dielectric constant of 1.03 as a support material and a planar to waveguide (WR-15) transition to a RF front-end.
- the dimensions of such an antenna are preferably as given in figures 7 and 8. For the frequency range of 94 GHz a thinner substrate is recommended.
- the final trimming of the antenna dimensions particularly for higher frequencies should be done by a full wave electromagnetic simulator, if not direct scaling is applied. It is possible, by changing of the in-face feeding network to obtain a reduction of the side lobes at specified frequencies using the same structure for a dipole antenna according to the present invention. Further on, with the proposed structure of a dipole antenna, the increase of the gain of the antenna with the increase of the number of elements 5, 6 is possible.
- Figure 7 shows a top view of some of the multiple elements 5, 6 projected into one common plane having preferred dimensions. All the preferred dimensions given in figure 7 are in millimeters.
- the preferred shape of the elements 5, 6 is a pentagonal shape having 5 corners. One of the corners respectively is the contact area between the pentagonal elements 5, 6 and the first and second lines 8, 9.
- the first elements 5 point in a first direction and the second elements 6 point in a second direction opposite to said first direction.
- the first and the second direction are perpendicular to the length direction of the lines 8, 9.
- the inner side of the pentagonal elements 5, 6 adjacent to the corner building the contact area has a length of 0.6338 mm and the outer side of the elements has a length of 0.9 mm.
- the end side of the pentagonal elements 5, 6 opposite to the corner building the contact area has a length of 0.4595 mm, whereas the two sides between the end side and the sides adjacent to said contact area have a length of 0.8194 mm.
- the width of the first and second lines between the last T-junction 15 and the first and second elements 5, 6 have a constant width of 0.19 mm and a length of 1.884 mm from said T-junction 15 to the contact area.
- the width of the T-junctions 15 is 0.485 mm, which is also the width of the first and second line portions 13, 14 at the T-junctions 15 in direction to the elements 5, 6.
- the distance between the first and second lines 8, 9 contacting the elements 5, 6 and the parallel first and second line portions 13, 14 is 1.8574 mm.
- the distance between the middle axis of adjacent elements 5, 6 being coupled to the same T-junction 15 is 4.39 mm.
- the inner angle of the corner of the pentagonal elements 5, 6 building the contact area is less than 70°, the inner angle of the two corners adjacent to the corner building the contact area is approximately 120° and the two angles opposite to the angle building the contact area is approximately 110°.
- the distance between two first or second elements 5, 6 respectively, being adjacent in the length direction of the elements and coupled over three T-junctions 15 is 4.39 mm, measured between two respective corners having inner angles of approximately 120°. Therefore, respective elements 5, 6 are equidistant from one another.
- a top view of a waveguide transition element 12 is shown with preferred dimensions.
- the waveguide transition element 12 provides a transition between the balanced metal strips 5, 6 to a waveguide, e.g. WR-15.
- the waveguide transition element 12 provides a plurality of teeth-like elements 20, 21 for each of the metal strip lines 8, 9, the teeth-like elements 20, 21 pointing in respective directions perpendicular to said metal strip lines 8, 9.
- the length of the teeth-like elements is 0.93 mm and their width is 0.234 mm.
- the overall length of the waveguide transition element 12 from the first side 22 coupled to the metal strip lines 8, 9 and the second side 23 coupled to the waveguide is 5.18 mm. It is to be noted, that all of the preferred dimensions given in the figures 7 and 8 are adopted to a dipole antenna working at a center frequency of 60 GHz, whereby the major of the dimensions are up- and down-scaleable taking into account the center frequency of 60 GHz.
- the input reflection coefficient of the antenna (S11 in dB) over a frequency band from 50.0 to 65.0 GHz is presented for the antenna according to the present invention.
- the antenna according to the present invention shows excellent values despite a frequency selective waveguide transition from the front end to the balanced metal strip lines of the feeder of the antenna according to the present invention.
- the input reflection coefficient of the antenna according to the present invention does not exceed -13 dB in the range of the measurement, or leads to a VSWR maximum value of 1.58.
- in a range between 50.0 and 65 GHz similar values of S11 have been found, meaning at least 30% working range. Measurements in larger bands were not possible due to the limited frequency band of the used waveguide (WR-15.50 - 70 GHz).
- a measured antenna diagram at 60 GHz for the main horizontal plane for an antenna according to the present invention is shown.
- the diagram shown in figure 10 shows the gain of the antenna according to the present invention in dB over the radiation angle ⁇ between - 45° and + 45°.
- the measurement was performed in comparison to a well-known horn-antenna.
- the light non-symmetrical behavior of the shown diagram is up to non-perfect measurement equipment.
- the measured antenna gain is 23.5 dB vs. about 26.5 dB estimated (simulation) directivity, leading to overall losses of about 3 to 3.5 dB including losses due to the waveguide to balanced metal strip transition, which is a very good value.
- the maximum gain ripple in the measured range does not exceed 1 dB, which shows the excellent performance of the dipole antenna according to the present invention.
- the antenna array is fed in phase, so that side lobes of - 13 dB to the main lobe should appear. In all of the measured cases (50 - 65 GHz), the side lobes did not exceed - 10 to - 11 dB of the carrier strength.
- an input reflection diagram of a simple radiation element is compared to the proposed high-gain solution according to the present invention.
- the input reflection coefficient (S11 in dB) of a microstrip patch antenna designed to 61.5 GHz is shown in figure 11.
- the measured microstrip patch antenna is a low-cost antenna with a very high tolerance sensitivity showing large problems with the feeding of signals, if high gain application with a plurality of elements at very high frequencies are applied.
- the input reflection coefficient (S11 in dB) of a known monopole antenna designed to 61.5 GHz was measured without a radome.
- the measured monopole antenna showed a very high tolerance sensitivity, only a small gain and no high gain features. Also, the reproducibility and the shadowing in the elevation angle of 90° of the measured monopole antenna was very critical.
- FIG 13 one measured and two simulated curves for the input reflection coefficient (S11 in dB) of a dielectric lens antenna in the frequency range of 57.0 to 65.0 GHz are shown.
- the two smooth curves are the simulated curves whereas the third curve showing a sharp drop at 58.7 GHz is the measured dielectric lens antenna.
- the measured dielectric lens antenna required at the moment waveguide feeders, which are large (diameter 8 cm) for 60 GHz and are quite expensive featuring more or less only low gain remote station (base station) applicability in the 60 GHz range.
- the antenna according to the present invention has an excellent performance even at very high frequencies.
- the antenna of the present invention can be produced as a low-cost low gain antenna as well as a high gain antenna for all kinds of purposes in the microwave and in the millimeter wave range and above.
- the antenna according to the present invention can be successfully used for microwave and millimeter wave wireless LANs and private short data links, as well as for automotive radar applications, where low-cost planar solutions are required.
- this antenna can cover a whole band planned for millimeter wave wireless LANs 59 - 64 GHz, and the two bands planned for anti-collision (automotive, car) radars in Europe and the USA (76 GHz) and Japan (61 GHz), simultaneously.
Abstract
The present invention relates to an antenna comprising a dielectric substrate means (1)
comprising a front and a back face (2, 3), at least one dipole means (4) comprising a first
and a second element (5, 6) for radiating and receiving electromagnetic signals, said first
element (5) being printed on said front face and said second element (6) being printed on
said back face (3), metal strip means (7) for supplying signals to and from said dipole
means (4), said metal strip means (7) comprising a first line (8) printed on said front face
(2) and coupled to said first element (5) and a second line (9) printed on said back face (3)
and coupled to said second element (6), and reflector means (10) spaced to and parallel
with said back face (3) of said dielectric substrate (1), a low loss material (11) being
located between said reflector means (10) and said back face (3) and having a dielectric
constant less than 1.2, wherein said first and said second lines (8, 9) are balanced and
arranged parallel and opposite to each other on said front and back dielectric face (2, 3),
respectively. The present invention relates to a low cost wide band planar printed antenna
solution for microwave and mm-wave range. A particular solution for 60 GHz with low
and high gain is introduced.
Description
The present invention relates to an antenna according to the preamble of claim 1.
Such a dipole antenna is known from US-PS 5021799. This US-patent discloses a dipole
antenna, in which the first line and a second line of a microstrip transmission line means
are tapered to provide a microstrip-to-balanced line impedance transformation. Further on,
the first and the second line are separated in the direction of the dielectric substrate middle
plane, form an electric field and provide an impedance transformation from an unbalanced
line part of the microstrip transmission line means to first and second balanced dipole
antenna elements. Therefore, in the antenna disclosed in US-PS 5021799, the
transformation from unbalanced to balanced transmission is conducted within microstrip
transmission line means of the dipole antenna. Also, this antenna is inherently selective
(not wide band) due to the classic dipole microstrip structure. Further on, this known
antenna is tolerance sensitive. The thickness of the substrate of this known antenna is
0.0125 wavelength, that would lead for the 60 GHz range to a thickness of 0.0625, which
is very thin and critical to be manufactured and handled. However, due to the specific
structure of the dipole antenna disclosed in US-PS 5021799, the dipole antenna can be
mainly applied for narrow band applications. The manufacturing tolerances, increased
losses in dielectric material, decreasing of the substrate thickness, supporting the substrate
with the same distance to the reflector plane, as well as possible appearance of the high
order modes limits its application in the lower microwave range (3-30 GHz).
US-PS 4737797 discloses a dipole antenna without a reflector plane. This dipole antenna
comprises a transmission part within the microstrip transmission line means, in which
signals are converted from an unbalanced line to a balanced line to permit the signal to be
radiated by first and second balanced dipole elements. The dipole antenna disclosed in US-PS
4737797 exhibits a wide band width up to 1.7 GHz (about 30 %). However, the dipole
antenna does not allow applications up to the millimeter wave range, because of very
critical tolerances (thin traces) for balun-circuits and very thin substrates (like 0.024 mm
for 60 GHz), where a physical support of the structure (robustness) and availability of such
small dielectric thickness is questionable.
Therefore, the object of the present invention is to provide an antenna according to the
preamble of claim 1, which allows applications deep into millimeter wave frequencies
within a very large band width with a good efficiency.
This object is achieved by an antenna with the features of claim 1. The antenna according
to the present invention comprises a dielectric substrate including a front and a back
dielectric face, at least one dipole means comprising a first and a second element for
radiating and receiving electromagnetic signals, said first element being printed on said
front face and said second element being printed on said back face, metal strip means for
supplying signals to and from said dipole means, said metal strip means comprising a first
line printed on said front face and coupled to said first element and a second line printed
on said back face and coupled to said second element, and reflector means spaced to and
parallel with said back face of said dielectric substrate, a low loss material being located
between said reflector means and said back face and having a dielectric constant less than
1, 2, being characterized in that said first and said second lines are balanced and arranged
parallel and opposite to each other on said front and back dielectric face, respectively.
The antenna according to the present invention has a very large band width and allows
applications deep into the millimeter wave frequency range. Further on, the antenna
according to the present invention can be fabricated at very low production costs, e.g. due
to the utilization of a simple planar technology, utilization of a printed technology and/or
simple and cheap photolithographic processing of the prints. Further on, the antenna
according to the present invention can be produced with a small size and a high
reproducibility due to a low tolerance sensitivity of the dipole antenna. Also, a simple
integration with planar RF-assemblies is possible, since it is assumed that future
microwave and millimeter wave technologies will be based on planar assemblies rather
than waveguide technology. A big advantage of the antenna according to the present
invention is the possibility to use the same antenna for different kinds of communication
systems even at different frequency bands of interest. Possible identified mass market
applications are e.g. broad band home networks, wireless LAN, private short radio links,
automotive millimeter wave radars, microwave radio and TV distribution systems
(transmitters and ultra low cost receivers). Some of the identified frequency bands of
interest are: 5 GHz, 10.5 GHz, 17-19 GHz, 24 GHz, 26-27 GHz, 28 GHz, 40 GHz, 51
GHz, 59-64 GHz, 76 GHz and 94 GHz. At the same time the antenna according to the
present invention satisfies the following general requirements, namely has a specific
radiation pattern, a good matching in the frequency band of interest and a good efficiency
in the frequency band of interest.
Particular advantages of the antenna according to the present invention compared to known
dipole antennas are explained in the following. The antenna according to the present
invention has a very large band width of more than 30 % working range compared to
known microstrip dipole antennas. Therefore, a same antenna according to the present
invention can be used for different systems and different applications. Further on, the
production tolerances of different parts of the antenna according to the present invention
are much less critical than for known microstrip dipole antennas, which is very important
for the frequencies in the microwave and the millimeter wave ranges. Due to its particular
structure, the antenna according to the present invention has lower losses and sensitivity to
higher order modes propagation at higher frequencies (microwave range) and mm-wave
range compared to known microstrip dipole antennas. Due to the low tolerance sensitivity
of the antenna according to the present invention, the manufacturing particularly for
millimeter wave frequency ranges is much less critical. The higher unwanted higher order
modes in the case of the microstrip line appear at lower frequencies compared to a
balanced microstrip line printed on a substrate with the same thickness. Further on, in the
antenna according to the present invention the influence of the feeding network on the
radiation pattern, is much lower, due to the balanced microstrip feeding line structure,
than in known microstrip dipole antennas. The required dielectric substrate thickness for
an optimum working scenario (small losses in wanted radiation pattern) is very small in the
case of known microstrip dipole antennas. The thickness of the dielectric substrate is not
so critical for the antenna according to the present invention, so that the antenna according
to the present invention is easier and cheaper to produce. A further very large advantage of
the antenna according to the present invention is the feasible maximum frequency of
operation, which can be achieved by producing the antenna with commercial low cost
photo lithography technology. The feasible maximum frequency of the antenna according
to the present invention is 94 GHz and 140 GHz with a dielectric thickness of about 50 µm
(commercially available) and an advanced photolithographic technology. The feasible
maximum frequency of known microstrip dipole antennas is 40 GHz and 60 GHz with a
very advanced technology and problems in reproducibility. Therefore, the antenna
according to the present invention provides a low cost wide band dipole antenna having not
critical tolerances particularly suitable for microwave and millimeter wave applications.
Further advantageous features of the antenna according to the present invention are defined
in the subclaims.
Advantageously, the low loss material is a supporting structure supporting said reflector
means and said back face. Further on, the antenna according to the present invention can
comprise a plurality of dipole means, each comprising a first and a second element
supported by said front face and said back face, respectively, said first and second line
respectively comprising a plurality of first and second line portions, said first and second
line portions respectively being connected to each other by T-junctions, said first elements
pointing in a first direction and said second elements pointing in a second direction
opposite to said first direction. An antenna having a plurality of dipole elements has a
higher gain than an antenna with one or only a few dipole elements. The antenna input
impedance is treated and matched in the way of having 100 Ohms in the whole frequency
band. If a transition from some specific impedance of the feeding network is required, the
impedance transformation is done by increasing the width of each of the line portions.
Thereby, each of said first and second line portions can be tapered between two adjacent
T-junctions, so that the width of each line portion increases towards said first and second
elements, respectively, to provide an impedance transformation in the succeeding T-junction.
Thereby, the width of each of the line portions can gradually increase to provide
an impedance transformation of a ratio 1:2 in the succeeding T-junction. The line portions
can be tapered corresponding a linear, exponential or polynomial function.
Also, the length of said first and second elements is respectively smaller than 0,5 λ the
mean width w of the respective element is smaller than 0,35 λ and the width c of a contact
area between said respective element and said first or second line coupled to said
respective element is smaller than 0,1 λ, whereby λ is the free space wavelength of the
center frequency of the band of interest, the angle between the respective line and each of
the adjacent sides of the respective element being larger than 10 degrees. Thereby, said
first and second elements can have a structure comprising at least three corners, whereby
said contact area is one of said corners. Advantageously, said first and second elements
have a pentagonal shape. Further on, the distance of the reflector means to the middle of
said dielectric substrate means is approximately one fourth of the electrical wavelength of
the working band frequency within said low loss material. Advantageously, the antenna of
the present invention has a transition element coupled to said first and second lines to
provide a transition between said first and second lines and a waveguide for guiding
signals to and from the antenna, said transition element comprising first teeth elements
coupled to said first line and second teeth elements coupled to said second line, said first
teeth elements pointing in a first direction and said second teeth elements pointing in a
second direction opposite to said first direction, said first and said second direction being
perpendicular to said first and second lines.
The present invention will in the following be explained in more detail by means of a
preferred embodiment under reference to the enclosed drawings, wherein
Figure 1 shows a schematic upper view of an antenna according to the present invention,
with a projection of metal strip means 7 and a plurality of dipole means 4 from a front
face 2 and a back face 3 of the dielectric substrate means 1 in a common plane. In the
antenna according to the present invention, the first elements 5 of the dipole means 4 are
printed on the front face 2 of the dielectric substrate means 1 and the second elements 6 of
the dipole means 4 are printed on the back face 3 of the dielectric substrate means 1. The
first elements 5 are connected to each other with a first line 8 supported by the front face 2
for supplying signals to and from the first elements 5. The second elements 6 are coupled
to each other with a second line 9 supported by the back face 3 for supplying signals to
and from said second elements 6. In the example shown in figure 1, the first line 8 and the
second line 9 building the metal strip means 7 have a balanced microstrip structure and are
connected to a waveguide transition element 12 near the edge of the dipole antenna to
provide a transition between the balanced lines 8 and 9 to a waveguide supplying the
signals to be radiated by the dipole means 4. The waveguide transition element 12 consists
of two parts connecting each of the lines 8 and 9 to a waveguide. Each of the two parts of
the waveguide transition element 12 comprises a plurality of teeth elements arranged
perpendicular to the direction of the lines 8, 9 on the front face 2 and the back face 3,
respectively. It is to be noted, that future commercial communication systems in
microwave and millimeter wave ranges will be based on planar technology, so that other
kinds of transition elements will be needed. The waveguide transition element 12 is
important for the shown example due to the lack of a planar front end.
In figure 1, the first line 8 and the second line 9 respectively printed on the front face 2
and the back face 3 each split into two branches by means of a T-junction 15 located
approximately in the middle of the dipole antenna. From the first T-junction 15 located
approximately in the middle of the dipole antenna, succeeding T-junctions 15 being
respectively rectangular to each other split the first line 8 and the second line 9 into a
respective plurality of first line portions 13 and second line portions 14. Each line portion
13 is connecting two adjacent T-junctions 15 and each second line portion 14 is also
connecting two adjacent T-junctions 15.
As can be seen from figure 1, the structure of the first and second line portions 13, 14 and
the succeeding T-junctions 15 is symmetrical for the two branches. Further on, respective
adjacent first and second line portions 13 and 14 are rectangular to each other. After the
last T-junctions 15, respective end portions of the first line 8 and the second line 9 lead
into dipole means 4. Each dipole means 4 comprises a first and a second element 5, 6 for
radiating and receiving electromagnetic signals transmitted by the first line 8 and the
second line 9. The first elements 5 are printed onto the front face 2 of the dielectric
substrate 1 and the second elements 6 are printed onto the back face 3 of the dielectric
substrate 1. The first and the second elements 5, 6 respectively extend generally
perpendicular to the first or second line portion 13, 14 they are connected with. Further
on, the first elements 5 are pointing in a first direction and the second elements 6 are
pointing in a second direction which is opposite to that first direction, as can be seen from
figure 1. The preferred shape of the first and the second elements 5 and 6 is a pentagonal
shape. As can be further seen in figure 1, the first line portions 13 and the second line
portions 14 between adjacent T-junctions 15 are tapered to provide an impedance
transformation in the succeeding T-junction located in direction to the dipole means 4. The
first and second line portions 13, 14 are tapered, so that the width of each line portion 13,
14 increases towards that first and second elements.
In figure 2, the schematic perspective view of a portion of the antenna shown in figure 1
having two dipoles is shown. The antenna comprises a substrate 1 having a front face 2
and a back face 3. The first elements 5 are printed on the front face 2 and the second
elements 6 are printed on the back face 3. Also, the first lines 8 are printed on the front
face 2 and the second lines 9 are printed on the back face 3. In figure 2, only two dipole
means 4 are shown, which are fed by first and second lines 8, 9. The T-junction 15
between the two shown dipole means 4 is fed by a first line portion 13 on the front face 2
and a second line portion 14 on the back face 3. The first and the second line portion 13,
14 are tapered with an increasing width towards the dipole means 4. The tapering provides
an impedance transition from 100 Ω at the narrow part of the first and the second line
portion 13, 14 to 50 Ω at the large part of the first and the second line portion 13, 14. At
the T-junction the first and second line portion 13, 14 are split into the not-tapered end
portions of the first and the second line 8, 9 leading to the dipole means 4. The low loss
material 11 between the dielectric substrate 1 and the reflector means 10 is chosen to have
minimum losses and a dielectric constant less than 1.2. In the shown example, the low loss
material 11 is a supporting structure supporting said reflector means 10 and said dielectric
substrate on its back face 3. In other embodiments, the loss material 11 can be air, so that
a free space exists between the dielectric substrate 1 and the reflector means 10.
Advantageously, the low loss material is a polyurethane foam. However, the low loss
material can be any other material with a dielectric constant less than 1.2. By a variation
of the low loss material 11 the thickness of the antenna can be influenced. In figure 2,
dashed lines are used to show the second element 6 and the second line 9 being printed on
the back face 3 of the dielectric substrate 1.
In figure 3 a cross section of an antenna according to the present invention is shown. A
first element 5 is printed on the front face 2 of the dielectric substrate 1, and the second
element 6 is printed on the back face 3 of the dielectric substrate 1. The dielectric substrate
with the second elements 6 and the second lines 9 printed thereon is supported by a low
loss material 11 building a supporting structure. On the face of the low loss material 11
opposite to the back face 3 of the dielectric substrate 1, a reflector means 10 is located.
The reflector means shown is a reflector plate parallel to said back face.
The distance d between the upper face of the reflector means 10 and the middle of the
dielectric substrate 1 is about one fourth of the electrical wave length λ of the central
frequency (middle of the working band) within the low loss material dealing as a support
structure between the dielectric layer 1 and the reflector means 10. Advantageously, the
distance d is λ / (4 × sqrt (εr )) ± 10% , wherein εr is the dielectric constant of the low loss
material. A slight change of the distance d can cause special effects in the radiation pattern
of the dipole antenna, which are sometimes wanted. Further on, the antenna of the shown
embodiment has a planar shape, whereby other shapes of the antenna according to the
present invention might be used.
In figure 4, a cross section of the dielectric substrate 1 with the first line 8 and the second
line 9 printed on the front face 2 and the back face 3, respectively, is shown. As can be
seen from figure 4, the first line 8 and the second line 9 are balanced and arranged parallel
and opposite to each other on the front and the back face 2, 3, respectively. The width and
the shape of the first line 8 and the second line 9 are the same. It is to be noted, that the
whole feeding network in form of the metal strip means 7 is realized by balanced metal
strip lines being parallel and opposite to each other. The symmetry axis of the first line 8
and the second line 9 lies within the middle plane of the dielectric substrate 1. The antenna
according to the present invention can have one or more dipole means 4. If there is only
one dipole means 4, a tapering of portions of the first line 8 and the second line 9 is not
necessary, because there are no junction discontinuities in the metal strip means 7. In case
that the antenna according to the present invention comprises a plurality of dipole means 4,
T-junctions 15 are provided to distribute the signals to and from the plurality of dipole
means 4. The T-junctions 15 of the first line 8 and the second line 9 are also balanced T-junctions
and respectively arranged parallel and opposite to each other on said front and
back face 2, 3, respectively. Further on, the T-junctions can be provided with a triangular
gap in order to compensate the influence of the junction discontinuity, as can be seen e.g.
in the T-junction 15 shown in figure 2.
In order to integrate the antenna according to the present invention with a necessary front-end,
a transmission line transition between the balanced metal strip lines according to the
present invention to the transmission line technology of the front-end is necessary. If
waveguide technology is used in the front-end, a waveguide transition element 12 shown
in figure 1 can be used. If the front-end utilizes a microstrip technology, a microstrip to
balanced microstrip transition should be used. If the front-end utilizes a coplanar
waveguide technology, a coplanar waveguide to a balanced microstrip transition has to be
used. If the front-end utilizes coaxial lines, a coaxial connector to balanced microstrip
transition has to be used.
Due to the ultra-wide-hand operability of the antenna according to the present invention
and commercially available dielectric substrate thicknesses a whole frequency coverage up
to 140 GHz and more can be obtained without need to change the structure of the antenna
according to the present invention. Simple up-scaling and down-scaling the antenna of the
present invention allows the application for higher and lower frequency ranges without the
recalculation of the dipole antenna structure.
In figure 5, a first line portion 13 is shown to explain the tapered shape of the line portions
between two adjacent T-junctions 15. The small end 16 of the shown line portion is
connected to a T-junction 15 in direction to a transition element, e.g. the waveguide
transition element 12 shown in figure 1, whereas the long side 17 is connected to a T-junction
15 in direction to the dipole means 4. The width of the side portion increases
from the small end 16 to the large end 17 to provide an impedance transformation from
100 Ω to 2 × 50 Ω in the T-junction connected with the long end 17. To provide the
impedance transformation from 100 Ω to 50 Ω, the width of the line portion gradually
increases to provide an impedance transformation of a ratio 1:2 in the succeeding T-junction
15. The tapering of the balanced line portions 13 and 14 is actually smooth,
whereby the width of the lines on the front face 2 and the back face 3 of the dielectric
substrate 1 is changed simultaneously. A change of the width of the line portions changes
the impedance of the transmission lines. The above statements are equally true for the
second line portions 14.
The side portions 18 and 19 of the line portions can change with a linear function, as in
the example shown in figure 5. In other embodiments, the side portions 18 and 19 can
change with an exponential function or a polynomial function including a "Chebisshev
Polinom". The choice of the respective tapering function depends on the respective
working frequency and is made to have a minimal reflectivity in the line portions. The
tapering of the line portions is advantageous over the known quarter-wave transformers
because of the high frequency selectivity and high tolerance dependency of the quarter-wave
transformer. Further on, the balanced metal strip structure is advantageous over
known microstrip structures, since transitions to other printed structures over waveguides,
e.g. in a front-end, can be obtained much easier. Also, using a dielectric substrate 1 with a
constant thickness, the higher order modes propagation, which is a very undesired effect,
appear in known unbalanced microstrip lines at lower frequencies than in the balanced
metal strip lines according to the present invention.
In figure 6, four different shapes for the first elements 5 and the second elements 6 of the
dipole means 4 are shown. All the shown shapes are showing very good matching and
radiating performances within more than 50 % band around the central frequency as well
as applicability for microwave and mm-wave range due to not so critical tolerances.
However, the pentagonal shape shown in figure 6 a shows the best performances and is the
preferred shape for the antenna according to the present invention. Preferably, the first and
second elements 5, 6 have a structure comprising at least three corners and one of the
corners is the contact area between the respective line portion 13 or 14 and the element 5
or 6.
In figure 6 b, the element 5 or 6 has four corners with two long sides adjacent to the
corner building the contact area and two short sides opposite to said two long sides. In
figure 6 b, the element 5 or 6 has three corners. In figure 6 d, the element 5 or 6 has eight
comers having two long opposite sides, respectively two middle sides adjacent to said long
sides, and two short sides opposite to each other and rectangular to said long sides. One of
the two short sides is the contact area to the respective line portion, as can be seen in
figure 6 d.
Advantageously, the length l of said first and second elements 5, 6 is respectively smaller
than 0.5 λ, the mean width w is smaller than 0.35 λ and the width c of a contact area
between said respective element and said first or second line 8, 9 coupled to said
respective element is smaller than 0.1 λ, wherein λ is a free space wavelength of the
centered frequency band of interest. The mean width w is defined as the width of the
respective element 5, 6 at the half of the length l, as can be seen in figure 6. In figures 6
a, 6 b and 6 c the contact area width c is zero, since one of the corners of the respective
elements 5, 6 is the contact area, whereas in figure 6 d, the contact area width c is the
length of one of the short sides of the element 23. Further on, the angle α between the
respective line 8, 9 and the sides of the element adjacent to said contact area is preferably
larger than 10°. Elements 5, 6 with shapes as shown in figure 6 and having the above
defined characteristics are elements 5, 6 which can successfully work in frequency bands
of at least 30 %, typically 40 - 50 %, related to the center frequency, having a VSWR less
than 2. It is to be noted, that such elements 5, 6 can cover with a VSWR less than 2,5
even more than one octave.
A phase array assembled by dipole antenna elements according to the present invention
designed to work at a center frequency of 60 GHz preferably has 64 dipole means, a
dielectric substrate with a thickness of 0.127 mm and a dielectric constant of 2.22 (Teflon-fiber-glass),
a metallization thickness for the printed lines and elements of 17µm, a low
loss material of polyurethane with a dielectric constant of 1.03 as a support material and a
planar to waveguide (WR-15) transition to a RF front-end. The dimensions of such an
antenna are preferably as given in figures 7 and 8. For the frequency range of 94 GHz a
thinner substrate is recommended. The final trimming of the antenna dimensions
particularly for higher frequencies should be done by a full wave electromagnetic
simulator, if not direct scaling is applied. It is possible, by changing of the in-face feeding
network to obtain a reduction of the side lobes at specified frequencies using the same
structure for a dipole antenna according to the present invention. Further on, with the
proposed structure of a dipole antenna, the increase of the gain of the antenna with the
increase of the number of elements 5, 6 is possible.
Figure 7 shows a top view of some of the multiple elements 5, 6 projected into one
common plane having preferred dimensions. All the preferred dimensions given in figure 7
are in millimeters. As has been stated above and is shown in figure 7, the preferred shape
of the elements 5, 6 is a pentagonal shape having 5 corners. One of the corners
respectively is the contact area between the pentagonal elements 5, 6 and the first and
second lines 8, 9. The first elements 5 point in a first direction and the second elements 6
point in a second direction opposite to said first direction. The first and the second
direction are perpendicular to the length direction of the lines 8, 9. The inner side of the
pentagonal elements 5, 6 adjacent to the corner building the contact area has a length of
0.6338 mm and the outer side of the elements has a length of 0.9 mm. The end side of the
pentagonal elements 5, 6 opposite to the corner building the contact area has a length of
0.4595 mm, whereas the two sides between the end side and the sides adjacent to said
contact area have a length of 0.8194 mm. The width of the first and second lines between
the last T-junction 15 and the first and second elements 5, 6 have a constant width of 0.19
mm and a length of 1.884 mm from said T-junction 15 to the contact area. The width of
the T-junctions 15 is 0.485 mm, which is also the width of the first and second line
portions 13, 14 at the T-junctions 15 in direction to the elements 5, 6. The distance
between the first and second lines 8, 9 contacting the elements 5, 6 and the parallel first
and second line portions 13, 14 is 1.8574 mm. The distance between the middle axis of
adjacent elements 5, 6 being coupled to the same T-junction 15 is 4.39 mm. The inner
angle of the corner of the pentagonal elements 5, 6 building the contact area is less than
70°, the inner angle of the two corners adjacent to the corner building the contact area is
approximately 120° and the two angles opposite to the angle building the contact area is
approximately 110°. The distance between two first or second elements 5, 6 respectively,
being adjacent in the length direction of the elements and coupled over three T-junctions
15 is 4.39 mm, measured between two respective corners having inner angles of
approximately 120°. Therefore, respective elements 5, 6 are equidistant from one another.
In figure 8, a top view of a waveguide transition element 12 is shown with preferred
dimensions. The waveguide transition element 12 provides a transition between the
balanced metal strips 5, 6 to a waveguide, e.g. WR-15. The waveguide transition element
12 provides a plurality of teeth- like elements 20, 21 for each of the metal strip lines 8, 9,
the teeth- like elements 20, 21 pointing in respective directions perpendicular to said metal
strip lines 8, 9. The teeth-like elements 20 allocated to the first metal strip line point in a
first direction and the teeth-like elements 21 allocated to the second metal strip line 9 point
in a second direction opposite to said first direction. The length of the teeth-like elements
is 0.93 mm and their width is 0.234 mm. The overall length of the waveguide transition
element 12 from the first side 22 coupled to the metal strip lines 8, 9 and the second side
23 coupled to the waveguide is 5.18 mm. It is to be noted, that all of the preferred
dimensions given in the figures 7 and 8 are adopted to a dipole antenna working at a center
frequency of 60 GHz, whereby the major of the dimensions are up- and down-scaleable
taking into account the center frequency of 60 GHz.
In figure 9, the input reflection coefficient of the antenna (S11 in dB) over a frequency
band from 50.0 to 65.0 GHz is presented for the antenna according to the present
invention. As can be seen in figure 9, the antenna according to the present invention shows
excellent values despite a frequency selective waveguide transition from the front end to
the balanced metal strip lines of the feeder of the antenna according to the present
invention. The input reflection coefficient of the antenna according to the present invention
does not exceed -13 dB in the range of the measurement, or leads to a VSWR maximum
value of 1.58. As can be seen in figure 9, in a range between 50.0 and 65 GHz similar
values of S11 have been found, meaning at least 30% working range. Measurements in
larger bands were not possible due to the limited frequency band of the used waveguide
(WR-15.50 - 70 GHz).
In figure 10, a measured antenna diagram at 60 GHz for the main horizontal plane for an
antenna according to the present invention is shown. The diagram shown in figure 10
shows the gain of the antenna according to the present invention in dB over the radiation
angle ϕ between - 45° and + 45°. The measurement was performed in comparison to a
well-known horn-antenna. The light non-symmetrical behavior of the shown diagram is up
to non-perfect measurement equipment. The measured antenna gain is 23.5 dB vs. about
26.5 dB estimated (simulation) directivity, leading to overall losses of about 3 to 3.5 dB
including losses due to the waveguide to balanced metal strip transition, which is a very
good value. There is almost no change of the antenna diagram over the whole measured
frequency range of 50 - 65 GHz. The maximum gain ripple in the measured range does
not exceed 1 dB, which shows the excellent performance of the dipole antenna according
to the present invention.
The antenna array is fed in phase, so that side lobes of - 13 dB to the main lobe should
appear. In all of the measured cases (50 - 65 GHz), the side lobes did not exceed - 10 to -
11 dB of the carrier strength.
In order to show the outstanding capability of the antenna according to the present
invention an input reflection diagram of a simple radiation element (microstrip patch) is
compared to the proposed high-gain solution according to the present invention. The input
reflection coefficient (S11 in dB) of a microstrip patch antenna designed to 61.5 GHz is
shown in figure 11. The measured microstrip patch antenna is a low-cost antenna with a
very high tolerance sensitivity showing large problems with the feeding of signals, if high
gain application with a plurality of elements at very high frequencies are applied.
In figure 12, the input reflection coefficient (S11 in dB) of a known monopole antenna
designed to 61.5 GHz was measured without a radome. The measured monopole antenna
showed a very high tolerance sensitivity, only a small gain and no high gain features.
Also, the reproducibility and the shadowing in the elevation angle of 90° of the measured
monopole antenna was very critical.
In figure 13, one measured and two simulated curves for the input reflection coefficient
(S11 in dB) of a dielectric lens antenna in the frequency range of 57.0 to 65.0 GHz are
shown. The two smooth curves are the simulated curves whereas the third curve showing a
sharp drop at 58.7 GHz is the measured dielectric lens antenna. The measured dielectric
lens antenna required at the moment waveguide feeders, which are large (diameter 8 cm)
for 60 GHz and are quite expensive featuring more or less only low gain remote station
(base station) applicability in the 60 GHz range.
As can be seen from the shown diagrams, the antenna according to the present invention
has an excellent performance even at very high frequencies. The antenna of the present
invention can be produced as a low-cost low gain antenna as well as a high gain antenna
for all kinds of purposes in the microwave and in the millimeter wave range and above.
The antenna according to the present invention can be successfully used for microwave and
millimeter wave wireless LANs and private short data links, as well as for automotive
radar applications, where low-cost planar solutions are required. Moreover, this antenna
can cover a whole band planned for millimeter wave wireless LANs 59 - 64 GHz, and the
two bands planned for anti-collision (automotive, car) radars in Europe and the USA
(76 GHz) and Japan (61 GHz), simultaneously.
Claims (11)
- Antenna, comprisinga dielectric substrate (1) comprising a front and a back dielectric face (2, 3),at least one dipole means (4) comprising a first and a second element (5, 6) for radiating and receiving electromagnetic signals, said first element (5) being printed on said front face and said second element (6) being printed on said back face (3),metal strip means (7) for supplying signals to and from said dipole means (4), said metal strip means (7) comprising a first line (8) printed on said front face (2) and coupled to said first element (5) and a second line (9) printed on said back face (3) and coupled to said second element (6), andreflector means (10) spaced to and parallel with said back face (3) of said dielectric substrate (1), a low loss material (11) being located between said reflector means (10) and said back face (3), and having a dielectric constant less than 1.2,
characterized in,
that said first and said second lines (8, 9) are balanced and arranged parallel and opposite to each other on said front and back dielectric face (2, 3), respectively. - Antenna according to claim 1,
characterized in
that said low loss material (11) is a supporting structure supporting said reflector means (10) and said back dielectric face (3). - Antenna according to one of the preceding claims,
characterized by
a plurality of dipole means (4), each comprising a first and a second element (5, 6) printed on said front face and said back dielectric face (2, 3), respectively, said first and second lines (8, 9) respectively comprising a plurality of first and second line portions (13, 14), said first and second line portions (13, 14) respectively being connected to each other by T-junctions (15), said first elements (5) pointing in a first direction and said second elements (6) pointing in a second direction opposite to said first direction. - Antenna according to claim 3,
characterized in,
that each of said first and second line portions (13, 14) is tapered between two adjacent T-junctions (15), so that the width of each line portion (13, 14) increases towards said first and second elements (5, 6), respectively, to provide an impedance transformation in the succeeding T-junction (15). - Antenna according to claim 4,
characterized in,
that the width of each of the line portions (13, 14) gradually increases to provide an impedance transformation of a ratio one to two in the succeeding T-junction (15). - Antenna according to claim 4 or 5,
characterized in,
that said line portions (13, 14) are tapered corresponding a linear, exponential or polynomial function. - Antenna according to one of the preceding claims,
characterized in,
that the length (l) of said first and second elements (5, 6) is respectively smaller than 0,5 λ the mean width (w) of the respective element is smaller than 0,35 λ and the width (c) of a contact area between said respective element and said first or second line (8, 9) coupled to said respective element is smaller than 0,1 λ, whereby λ is the free space wavelength of the center frequency of the band of interest, the angle between the respective line (8,9) and each of the adjacent sides of the respective element (5,6) being larger than 10 degrees. - Antenna according to claim 7,
characterized in,
that said first and second elements (5, 6) have a structure comprising at least three corners and that said contact area is one of said corners. - Antenna according to claim 7 or 8,
characterized in,
that said first and second elements (5, 6) have a pentagonal shape. - Antenna according to one of the preceding claims,
characterized in,
that the distance (d) of the reflector means (10) to the middle of said dielectric substrate means (1) is approximately one fourth of the electrical wavelength of the working band frequency within said low loss material (11). - Antenna according to one of the preceding claims,
characterized by
a transition element (12) coupled to said first and second lines (8,9) to provide a transition between said first and second lines (8,9) and a waveguide for guiding signals to and from the antenna, said transition element (12) comprising first teeth elements (22) coupled to said first line (8) and second teeth elements (22) coupled to said second line (9), said first teeth elements pointing in a first direction and said second teeth elements pointing in a second direction opposite to said first direction, said first and said second direction being perpendicular to said first and second lines (8,9).
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97110679A EP0889543A1 (en) | 1997-06-30 | 1997-06-30 | Wide band printed dipole antenna for microwave and mm-wave applications |
CA002241128A CA2241128A1 (en) | 1997-06-30 | 1998-06-18 | Wide band printed phase array antenna for microwave and mm-wave applications |
US09/106,989 US6037911A (en) | 1997-06-30 | 1998-06-29 | Wide bank printed phase array antenna for microwave and mm-wave applications |
CNB981155936A CN1150661C (en) | 1997-06-30 | 1998-06-30 | Wide band printed phased array antenna for microwave and mm-wave applications |
KR1019980025325A KR19990007464A (en) | 1997-06-30 | 1998-06-30 | Broadband printing for microwave and millimeter wave applications |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97110679A EP0889543A1 (en) | 1997-06-30 | 1997-06-30 | Wide band printed dipole antenna for microwave and mm-wave applications |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0889543A1 true EP0889543A1 (en) | 1999-01-07 |
Family
ID=8226982
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97110679A Withdrawn EP0889543A1 (en) | 1997-06-30 | 1997-06-30 | Wide band printed dipole antenna for microwave and mm-wave applications |
Country Status (1)
Country | Link |
---|---|
EP (1) | EP0889543A1 (en) |
Cited By (15)
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WO2000051203A1 (en) * | 1999-02-24 | 2000-08-31 | Nokia Networks Oy | Antenna radiator |
EP1056154A1 (en) * | 1999-02-16 | 2000-11-29 | Radio Frequency Systems Inc. | Microstrip antenna having cylindrical shape |
GB2389233A (en) * | 2002-05-27 | 2003-12-03 | Samsung Thales Co Ltd | Planar antenna with linear and circular polarisation |
US6900765B2 (en) | 2003-07-23 | 2005-05-31 | The Boeing Company | Method and apparatus for forming millimeter wave phased array antenna |
US7443354B2 (en) | 2005-08-09 | 2008-10-28 | The Boeing Company | Compliant, internally cooled antenna apparatus and method |
GB2464582A (en) * | 2008-10-20 | 2010-04-28 | Furuno Electric Co | Radar antenna feeder line and horn arrangement |
US8503941B2 (en) | 2008-02-21 | 2013-08-06 | The Boeing Company | System and method for optimized unmanned vehicle communication using telemetry |
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CN110148834A (en) * | 2019-05-21 | 2019-08-20 | 华东师范大学 | High-gain log-periodic antenna based on disresonance type break bounds face |
CN113555691A (en) * | 2021-07-09 | 2021-10-26 | 侯宇庆 | Single printed dipole, double dipole, four dipole and eight dipole array antennas |
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EP1056154A1 (en) * | 1999-02-16 | 2000-11-29 | Radio Frequency Systems Inc. | Microstrip antenna having cylindrical shape |
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US7443354B2 (en) | 2005-08-09 | 2008-10-28 | The Boeing Company | Compliant, internally cooled antenna apparatus and method |
US8503941B2 (en) | 2008-02-21 | 2013-08-06 | The Boeing Company | System and method for optimized unmanned vehicle communication using telemetry |
GB2464582A (en) * | 2008-10-20 | 2010-04-28 | Furuno Electric Co | Radar antenna feeder line and horn arrangement |
GB2464582B (en) * | 2008-10-20 | 2013-02-13 | Furuno Electric Co | Antenna and radar apparatus |
RU2524563C1 (en) * | 2013-02-11 | 2014-07-27 | Корпорация "САМСУНГ ЭЛЕКТРОНИКС Ко., Лтд." | Compact ultra-wideband antenna |
CN104393406A (en) * | 2014-11-20 | 2015-03-04 | 上海无线电设备研究所 | Single-pulse array antenna |
CN104393406B (en) * | 2014-11-20 | 2017-07-14 | 上海无线电设备研究所 | A kind of Monopulse Antenna |
CN108400437A (en) * | 2018-03-14 | 2018-08-14 | 成都泰格微波技术股份有限公司 | Compare airborne antenna before and after a kind of broad beam height |
US11411322B2 (en) | 2018-06-07 | 2022-08-09 | King Fahd University Of Petroleum And Minerals | Concentric pentagonal slot based MIMO antenna system |
CN109301461A (en) * | 2018-11-22 | 2019-02-01 | 湖南华诺星空电子技术有限公司 | A kind of miniature ultra wide band plane yagi aerial |
CN109301461B (en) * | 2018-11-22 | 2024-03-08 | 华诺星空技术股份有限公司 | Miniaturized ultra-wideband planar yagi antenna |
CN110148834A (en) * | 2019-05-21 | 2019-08-20 | 华东师范大学 | High-gain log-periodic antenna based on disresonance type break bounds face |
CN113555691A (en) * | 2021-07-09 | 2021-10-26 | 侯宇庆 | Single printed dipole, double dipole, four dipole and eight dipole array antennas |
CN113555691B (en) * | 2021-07-09 | 2023-09-26 | 侯宇庆 | Uniprinted dipole, double dipole, quad dipole and octadipole array antenna |
CN114256611A (en) * | 2021-11-15 | 2022-03-29 | 北京木牛领航科技有限公司 | Manufacturing constraint method, measuring method and device of millimeter wave radar printed antenna |
CN114256611B (en) * | 2021-11-15 | 2023-08-11 | 北京木牛领航科技有限公司 | Manufacturing constraint method, measuring method and device for millimeter wave radar printed antenna |
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