KR20110011677A

KR20110011677A - A dielectrically-loaded antenna

Info

Publication number: KR20110011677A
Application number: KR1020107027828A
Authority: KR
Inventors: 올리버 폴 레이스텐; 니콜라스 로저 패드필드
Original assignee: 사란텔 리미티드
Priority date: 2008-05-13
Filing date: 2009-05-12
Publication date: 2011-02-08
Also published as: CN102089929A; WO2009138729A1; GB0808661D0; BRPI0911840A2; TW201001801A

Abstract

The dielectric mounted multifiller antenna has an electrically insulating solid core that supports the antenna element structure having four pairs of substantially helical radiating elements. Each pair of opposedly disposed antenna elements forms part of a conductive loop having an effective electrical length near N tube wavelengths, where N is an integer and at least two, at an operating frequency. In general, each helical element is fully wound once about an axis on the outer surface of the core. The antenna provides an improved gain-bandwidth product compared to conventional dielectric mounted multifiller helical antennas, and a 3 dB beam width for circular polarized radiation of at least 90 °.

Description

A dielectrically-loaded antenna

The present invention relates to a dielectric mounted antenna for operation above 200 MHz and a portable wireless terminal comprising the antenna.

Such antennas are disclosed in a number of applicants' patent publications, including GB2292638A, GB2309592A, GB2310543A, GB2338605A, GB2346014A, GB2351850A, and GB2367429A. Each of these antennas has at least a pair of diametrically opposed helical antenna elements plated on a substantially cylindrical electrically insulating core made of a material having a dielectric constant of at least five. The material of the core occupies a major part of the volume defined by the core outer surface. Extending from one end face to the opposite end face through the core is an axial bore containing a coaxial feeder structure comprising an inner conductor surrounded by a shielding conductor. At one end of the bore, the feeder structure conductors are connected to respective antenna elements with associated connections adjacent the end of the bore. At the other end of the bore, the shield conductor is connected to the conductor connecting the antenna elements, in each of these examples being in the form of a conductive sleeve encircling part of the core to form a barun. Each antenna element terminates at the rim of the sleeve and is parallel to each helical path from its connection to the feeder structure.

Some of these prior art publications disclose quadrifilar helical antennas designed primarily for receiving or transmitting circularly polarized electromagnetic waves. Each of these antennas has four helical tracks plated on the cylindrical string surface of the core, or four groups of helical tracks, each group comprising two tracks forming one composite antenna element and separated by narrow slits. .

Whether the antenna has four helical antenna elements or two helical antenna elements, the connections connecting the antenna elements to the feeder structure conductors are radial tracks plated on the planar end face of the core.

It is known to provide quadrefill helical antennas with an impedance matching network. This may be embodied as a small printed circuit or laminate board that is secured to the end face of the core and provides a coupling between the feeder structure and the radial connections as disclosed in the above-mentioned prior art publications. An antenna with such a matching network is disclosed in international patent application WO2006 / 136809.

International patent application WO2008 / 084205, published July 17, 2008, discloses dielectric mounted antennas with three pairs and four pairs of opposite helical antenna elements, respectively. This application and the disclosure of each of the prior patent publications mentioned above are specifically incorporated herein by reference.

It is an object of the present invention to provide an antenna having an improved gain-times-bandwidth product.

According to a first aspect of the invention, a dielectric-mounted multifilar antenna having an operating frequency above 200 MHz has a dielectric constant of at least 10 and has the electrical properties of a solid material occupying a major portion of the internal volume defined by the core outer surface. An insulating core and at least two pairs of substantially helical conductive antenna elements spaced about an axis of the antenna and comprising a three dimensional antenna element structure on or adjacent to the core outer surface. Each of these pairs of antenna elements forms part of a conductive loop having an effective electrical length near an N tube wavelength (where N is an integer and at least 2) at an operating frequency. In general, since each substantial helical element has an electrical length of N / 2 wavelength, it is appropriate to allow it to be substantially turned full once about the antenna axis. The antenna elements are preferably spaced substantially uniformly around the antenna axis. Also, the antenna elements are preferably in the same space in the axial direction. The antenna has a far-field 3 dB beamwidth for circular polarized radiation of at least 90 °, thus obtaining a beam width of 120 ° in general. It is advantageous that the dielectric constant of the solid material is at least 20, and the preferred material is calcium magnesium titanate having a relative dielectric constant of 21. Thus, it is possible to construct an antenna that achieves a zenith gain around +3 dB related to isotropy for circular polarized radiation.

Preferred antennas according to the invention comprise an antenna element structure having at least three pairs of substantially helical Fulton antenna elements. In a preferred antenna according to the invention, the core has an outer cylindrical surface portion, a first end surface portion, and a second end surface portion facing opposite to the first end surface portion. In this case, each pair of helical antenna elements includes two long conductive elements plated or bonded in a diametrically opposed configuraton to the outer cylindrical surface of the core. The antenna has an axially located feeder structure with a central feeder connection coupled with the first end surface portion. The axial feeder structure preferably passes through the core such that the antenna constitutes a so-called "backfire" antenna.

The antenna element structure of the preferred antenna each comprises a plurality of radially extending connection elements on or adjacent to the first end face portion, each of which connects each of the helical elements to a central feeder connection. The length is different for each pair of helical antenna elements so that the electrical length of the conductive loop included in each pair is different.

The antenna resonates in a circular polarization resonant mode at operating frequency, the resonant mode being characterized by a rotating dipole, the voltage maximums being excited in each of the long antenna elements continuously in the direction of rotation.

The preferred antenna comprises a pair of antenna element coupling nodes. Each of the pair of helical antenna elements has one antenna element connected to one of the coupling nodes, and another antenna element connected to the other one of the coupling nodes. The preferred antenna also has a common interconnecting conductor for helical antenna elements, which is advantageously in the form of a conductive ring interconnecting the ends of the long conductive elements. This conductor can be located in a plane that surrounds the axis and generally extends perpendicular to the axis. These intermediate connecting conductors enclose the core at the outer cylindrical surface and define a resonant conductive path around the core. Each helical antenna element has a first end connected to one or the other of the coupling nodes, and a second end connected to the common intermediate connecting conductor, wherein the connections of the second ends are at uniformly spaced connection points. .

It is advantageous that the electrical length of the annular conduction path formed by the common interconnecting conductor surrounding the core is substantially the same as the in-tube wavelengths of integers (1, 2, 3, ...) corresponding to the operating frequency of the antenna. This enhances the circular polarization resonance mode of the antenna because the common interconnecting conductors ring ring at the operating frequency, promoting the progression of the rotating dipole around uniformly spaced helical antenna elements.

The common intermediate connecting conductor may be a narrow annular conductor track with both edges on the outer side of the core. This arrangement is particularly suitable for endfire multifilar helical antennas. Optionally, the common intermediate connecting conductor may be comprised of a conductive sleeve that extends over the second end face and surrounds the core and connects with the shielding conductor of the coaxial transmission line feeder structure. This feeder structure passes through the core at connections with helical antenna elements at opposite end faces of the core. Such sleeves may form an integral balun as described in the applicant's prior patent publications mentioned above.

The ends of the helical antenna elements are preferably spaced equidistantly about the central axis, and this physical spacing is equal to the phase differences between the voltages and the currents for the respective elements. In general, the physical angular spacing between successive helical antenna elements does not vary more than 2: 1 at points between both ends of the helical elements and their ends.

In a preferred embodiment of the invention, the helical antenna elements are pure spirals of substantially the same length and the same pitch. The phase of the currents and voltages in the long antenna elements may not be completely dependent on the electrical lengths of these elements, in particular due to the common intermediate conductor, which exhibits ring resonance at the operating frequency. However, in the preferred embodiment, the phase of the elements can be achieved by arranging the radially extending connecting elements on the first end face portion differently for each pair of helical elements as mentioned above. For example, in an antenna having four pairs of helical antenna elements located in the outer cylindrical surface portion of the core, four first antenna elements are arranged next to each other to form a first group of antenna elements, and four second antenna elements are Arranged next to each other to form a second group of antenna elements, each group of antenna elements is connected to respective coupling nodes for coupling the antenna elements to the feeder structure. In this case, the radially extending connecting elements of each group change progressively monotonously, and the sense of the progression changes each group to make a monotonic progression in the lengths of the conductive loops around the core for each group. It is the same every time. As a result, each helical element and its corresponding connecting element have a respective pre-determined electrical path length between each coupling node and the other end of the helical element connected to the intermediate connecting conductor surrounding the core adjacent to the second end face of the core. Form together the conductors that produce it.

The radially extending connecting elements are preferably formed as part of a conductive foil on the first end surface portion of the core or adjacent to the first end surface portion, the foils respectively comprising radially extending connecting elements coupled to each of the groups of helical elements. It has two internal conductive arcs that interconnect. Preferred antennas include an impedance matching network consisting of a laminate board having conductive layers electrically connected to the above mentioned inner conductive arcs.

The ends of the helical antenna elements away from the radially extending connecting elements are preferably connected. Therefore, in a preferred embodiment, each helical antenna element of each pair of such elements has a first end coupled to each of the coupling nodes, and a second end connected to the second end of the other helical antenna element of the pair, It generally forms at least a portion of a conductive loop that is symmetric about an axis and has a predetermined resonance frequency. The loops formed by these pairs of helical elements are distributed at an angle with respect to the axis, and the respective resonant frequencies of the loops vary monotonically with an angular orientation about the axis. In this case, the second ends of the helical antenna elements are connected by a common intermediate connecting conductor surrounding the core so that the second ends are defined by the connections of the elements to the common angular edges of the intermediate heat conductor. can do. The edge connecting these helical elements can be located in a plane substantially perpendicular to the antenna axis.

It should be noted here that in the preferred embodiment of the present invention the phase of the currents and voltages on the helical antenna element is achieved by the conductors on the core rather than by using an antenna network.

A preferred embodiment of the present invention takes the form of an octapilar helical antenna having four pairs of long helical antenna elements on the cylindrical surface portion of the core, the angular spacing of such neighboring elements being in the cylindrical axis. 45 °. Each helical element is preferably wound completely once substantially about the axis.

The helical elements preferably include conductive tracks on the outer side of the core. They may be pure helices or may be displaced from the pure helical path, for example by meandering. It is also possible to change the electrical length, for example by bending only one of the edges of the track to a different size or by bending both edges to a different size. It should be noted here that octafiller antennas are more efficient than uniform quadrefill antennas because there are more conductive track edges of the radiating structure than equivalent quadrefill antennas. At the typical operating frequency of this antenna, currents tend to be trapped at the edges or perimeters of the conductor. As a result, increasing the number of paralleled edges reduces ohmic losses and, as a result, increases efficiency. By arranging each pair of helical antenna elements to form a conductive loop having an electrical length that is twice or more than twice the wavelength in the tube, the volume of the antenna is reduced compared to the octafiller antenna described in our pending GB0800222.2. Is increased. Increased volume is known to further increase the efficiency of the antenna without reducing its beam width. This is in contrast to the normally observed effect that helical antennas are usually more directional as the number of turns increases. The antenna of the present invention, despite having electrically longer conductive loops, exhibits a wavelength in air due to the relatively high relative dielectric constant of the radiating length of the antenna, ie the axial range of the helical antenna elements. Since it is still small compared to [lambda]), it is believed to show little or no reduction in beam width. It is preferable that the radiation length is λ / 4 or less. In the most preferred embodiment of the present invention, the radiation length is lambda / 6 or less.

If the spacing between each pair of helical elements measured perpendicular to the axis is about half the average axial range of the helical elements or the radiation length of the antenna, the efficiency is maximized.

Thus, it is possible to achieve a gain at the zenith of +3 dB (ie on the antenna axis) against isotropy for circular polarized radiation. The gain in this efficiency can be used to obtain improved sensitivity for the receiver and more effective transmission rate for the transmitter without significantly lowering the beam width.

Curving the helical elements can be used as a means of changing the respective electrical lengths of the elements to aid in the phase of the currents and voltages. It is also possible to vary the length of the helical elements with respect to each other by forming a common intermediate connecting conductor, eg a conductive sleeve, with a nonplanar edge to which the helical elements are connected. In order to obtain a larger change in relative length than is achieved with this single technique, it is possible to combine all of the above features or any one or both of them with the above-mentioned change in length of the radially extending connecting elements.

A particular use for such an antenna is in satellite cordless telephones using, for example, an iridium system having an operating frequency from 1616 MHz to 1626.5 MHz.

The present invention also includes a portable wireless communication terminal including the antenna as described above.

The invention is described below by way of example with respect to the drawings. In the drawing:
1 is a perspective view of an antenna according to the present invention,
FIG. 2 is a perspective view of a plated antenna core of the antenna of FIG. 1, seen from the distal end and one side,
3 is an axial cross-sectional view of the feeder structure of the antenna of FIG. 1,
4 is a detailed perspective view of the distal end of the antenna of FIG. 1, showing a matching network on a laminated board of the feeder structure;
5A and 5B are diagrams illustrating conductor patterns of conductive layers on the distal and base surfaces of the laminated board of the feeder structure, FIGS.
6 is a diagram illustrating a radiation pattern of an antenna.

1 and 2, an octafiller antenna according to the present invention comprises eight axially coextensive helical conductive tracks 10A and 10B plated or metallized on an outer cylindrical surface portion of a cylindrical core 12. 10C, 10D, 10E, 10F, 10G, 10H) antenna element structure with eight long antenna elements. The core is made of ceramic material. In this case, the material is calcium magnesium titanate having a relative dielectric constant of about 21. This material has excellent dimensional and electrical stability with temperature changes. Dielectric losses are generally negligible. In this embodiment, the core has a diameter D of 14 mm. The length of the core is more than twice the diameter, but may be smaller in other embodiments of the present invention. The core is made by pressing but can be made by an extrusion process, which is then fired.

Such a preferred antenna is a backfire in that it has a coaxial transmission line housed in an axial bore 12B that penetrates the core from the first end face portion in the form of the end face 12D to the second end face portion in the form of the base face 12P. Helical antenna. Both end faces 12D, 12P are planar and perpendicular to the central axis of the corner. The coaxial transmission line is a rigid coaxial feeder housed in the center of the bore 2B with an external shielded conductor spaced from the wall of the bore 12B so that a dielectric layer is effectively present between the shield conductor and the material of the core 12. to be.

Referring to FIG. 3, the coaxial transmission line feeder includes a conductive tubular outer shield conductor 16, a first tubular air gap or insulation layer 17, and an elongated inner conductor 18 insulated from the shield conductor by the insulation layer 17. Equipped. The shielding conductor 16 has spring-hanging portions or spacers 16T that protrude outwardly and are integrally formed so that the shielding conductor is spaced apart from the wall of the bore 12B. The second tubular air gap passes between the shield conductor 16 and the wall of the bore 12B. Instead, the insulating layer 17 may be formed of a plastic sleeve and may be a layer between the shielding conductor 16 and the wall of the bore 12B. At the lower proximal end of the feeder, the inner conductor 18 is located at the inner center of the shield conductor 16 by an insulating bush 18B.

The combination of the shield conductor 16, the inner conductor 18, and the insulating layer 17 connects the distal ends of the antenna elements 10A to 10H to the radio frequency (RF) circuit of the device to which the antenna is connected. This constitutes a transmission line of pre-determined characteristic impedance, here 50 ohms, which passes through the antenna core 12 for this purpose. The connection between the antenna elements 10A-10H and the feeder is made via conductive feed connections coupled with the helical tracks 10A-10H, which are plated on the end face 12D of the core 12. Formed radial tracks 10AR, 10BR, 10CR, 10DR, 10ER, 10FR, 10GR, 10HR (see FIGS. 1 and 2). Each feed connection extends from one end of each helical track to one of two inner arcuate conductors 10AD, 10EH plated on the core end face 12D adjacent to the end of the bore 12B.

The two arcuate conductors 10AD and 10EH are connected to the shielding and inner conductors 16 and 18 respectively by conductors on the laminated board 19 fixed to the core end surface 12D as described below. The coaxial transmission line feeder and the lamination board 19 together constitute a single feed structure before being assembled inside the core 12, and their interconnections can be seen by comparing FIGS. 1, 2 and 3.

Referring to FIG. 3, the inner conductor 18 of the transmission line feeder has a base portion 18P protruding as a pin from the base surface 12P of the core 12 for connection to the device circuit. Similarly, integral lugs (not shown) on the proximal end of the shield conductor 16 project beyond the core base surface 12P to make a connection with the device circuit ground.

As shown in FIG. 1, the proximal ends of the antenna elements 10A-10H are interconnected by a common virtual ground conductor 20. In this embodiment, the common conductor is annular and is in the form of a plating sleeve that surrounds the proximal end of the core 12 adjacent to the base surface 12P. The sleeve 20 is shielded conductor of the feeder by a plating conductive layer (not shown) of the core base end surface 12P to form a quarter wave balun as described in the above-mentioned prior art publications. 16).

Each of the eight helical antenna elements 10A-10H is connected to one of the arcuate conductors 10AD and 10EH and then to one of the helical element and arcuate conductor connected to the inner conductor 18 and the shielding conductor 16 of the transmission line feeder. Four pairs of elements 10A, 10E; 10B, 10F; 10C having another opposite helical element connected to the inner conductor 18 of the transmission line feeder and then the other opposite helical element connected to the shield conductor 16 , 10G; 10D, 10H). Therefore, the eight helical antenna elements 10A-10H are, in fact, one group of elements 10A-10D all connected to the first arched conductor 10AD and the other group of elements 10E-10H are all connected. It can be considered to be arranged in four two groups (10A-10D, 10E-10H) connected to the second arched conductor (10EH). Thus, the two arcuate conductors constitute first and second coupling nodes interconnecting the respective helical antenna elements and for connecting each group of elements to one or the other of the conductors of the transmission line feeder. Provide common connections.

As a result, each such pair of helical elements 10A, 10E; 10B, 10F; 10C, 10G; 10D, 10H has a corresponding pair of radial feed connection elements 10AR, 10ER; 10BR, 10FR '10CR, 10GR; 10DR, 10HR and the rim 20U of the sleeve 20 form a conductive loop between the two coupling nodes. In such an antenna, the electrical length of the conductive loop is 2λ _g (where λ _g is the in-tube wavelength of the currents traveling along the loop's conductors at the antenna's operating frequency). Each helical element of the pair is a full turn once within a range of + or-15% around the antenna axis such that the pair of helical elements have a torsion angle of about 360 with the radial feed connection elements and the rim. Try to form a torsion loop with °. The antenna of the present invention shows little or no reduction in beam width compared to an octafiller antenna having a loop length of λ _g and half-turn elements. However, the gain times bandwidth product is significantly increased because the volume of the antenna is approximately doubled (compared to octafiller antennas with lambda _g loops and the same core diameter).

Regarding the operating wavelength in air in the small antenna, the radiation length L _r (see FIG. 1) in this embodiment (ie, the average axial range of the helical elements 10A-10H of the antenna) is about 0.15 lambda ( Is the wavelength in the art). At 1621MHz in the iridium cordless telephone band, 0.15λ is about 28.5mm. In an antenna operating at this frequency, the axial length L _b of the balun sleeve 20 is about 4.5 mm, thus obtaining a total antenna length of about 33 mm. The aspect ratio of the radiating part of the antenna, ie the radiation length L _r divided by the diameter D, is about two. In general, the good aspect ratio is equal to the number of wavelengths represented by the electrical length of the conductive loop formed by each pair of helical elements and corresponding radial feed connection elements.

It has been described above that the conductive loops formed by each pair of helical elements and corresponding radial feed connection elements are twice the wavelength (ie, an electrical length of 720 °). In practice, this is the average length of the conductive loops, each loop having a slightly different length compared to the neighboring loop to obtain the progression of the individual resonant frequencies from pair to pair. Thus, at the operating frequency, there are phase shifts between the currents of each successive pair of devices, which phase shifts the circular polarization waves from the conventional quadrefill helical antenna to 90 ° phase shifts from device to device. In the same way as generating a resonance for, the resonance of the antenna occurs with respect to the circularly polarized waves. Applicants have found that best results are obtained when eight helical elements 10A-10H are of equal or similar length, and the variation in loop lengths from helical pair to helical pair is best seen in FIGS. 2 and 4. It was found that this was achieved by varying the lengths of the radial feed connection elements 10AR, 10ER; 10BR, 10FR; 10CR, 10GR; 10DR, 10HR.

Referring to FIGS. 2 and 4, the radial feed connection elements 10AR-10HR have respective inner arcuate conductors 10AD forming helical elements 10A-10H and a pair of coupling nodes as described above. , 10EH). The radial feed connection elements and the inner arcuate conductors are formed of a single conductive layer plated directly on the end face 12D of the core. As can be seen, the first 180 ° opposite pair of radial elements 10AR, 10ER are generally the next pair of radial elements 10BR, 10FR, the shortest pair of elements 10DR, 10HR in a counterclockwise direction. Longer than). More precisely, the lengths of the edges of the radial elements 10AR-10HR vary. That is, the spaces 24AB, 24BC, 24CD, 24EF, 24FG, and 24GH between neighboring radial elements are in the form of truncated sectors, and the degree of truncation is the radial elements of each group 10AR, 10BR; 10CR, 10DR; 10ER, 10FR; 10GR, 10HR) and increase counterclockwise. As a result, the lengths of the edges of each successive pair of elements are the same, but because of the difference in the edge lengths of each helical element 10A-10H resulting from an angled junction with the rim 20U (see FIG. 2), the helical The effective lengths of the device and radial device combinations 10A, 10AR-10H, 10HR vary gradually monotonically within each of the two groups of devices. (As understood by those skilled in the art, it is the lengths of the edges that determine loop lengths, since currents at the operating frequency tend to concentrate on the edges of the conductive tracks.)

In a preferred embodiment of the invention, the eight helical antenna elements 10A-10H are of equal length or of similar lengths. As a result, the rim 20U of the sleeve 20 is substantially planar and lies transverse to a plane substantially perpendicular to the antenna axis. However, as mentioned above, non-planar rims may be used in some cases.

Therefore, in summary, the helical elements 10A-10H of the preferred antenna are equally spaced at regular intervals at intervals of 360 ° / n (where n is the number of elements) around the core 12, and Each is arranged in two groups with n / 2 elements of similar length because of the varying distance of the rim 20U of the sleeve 20 from the end face 12D perpendicular to the central axis of the core. Each element substantially completely winds up the core once in this embodiment.

Plating on the conductive sleeve 20 and the proximal end surface 12P of the core is carried out with the shielding conductor 16 of the feeder when the antenna is operated at the operating frequency, from the device to which it is connected when the antenna is installed. Form a sleeve balun that provides common mode isolation. Therefore, the currents in the sleeve are trapped in the sleeve rim 20U. Thus, at the operating frequency, the rim 20U of the sleeve 20 and each pair of helical elements 10A 10E-10D, 10H form respective conductive loops connected to the balanced feed and the currents are connected to the rim 20U. Move between each pair of elements via.

In a preferred embodiment of the present invention, the circumference of the sleeve is equal to the constant intraluminal wavelengths at the operating frequency. This has the effect of reinforcing the resonance mode resulting from the resonance of the aforementioned conductive loops formed by the rim and the pair of helical elements at the operating frequency. In particular, as described in British Patent Publication GB2346014A described above, the sleeve 20 acts as a resonant structure itself independently from the helical elements 10A-10H. Therefore, the rim 20U of the sleeve having the same electrical length as the operating wavelength resonates in the ring mode. The reinforcement of the resonance mode due to the pairs of helical elements, the radial feed connection elements and the loops formed by the rim 20U, as described in GB2346014A, results in a wave at the rim 20U at the junction of each helical element and the rim. It can be visualized by injecting onto the ring shown and then moving around the rim 20U to form a rotating dipole. Because of the electrical length of the rim 20U, when the scanned wave moves around the rim 20U and returns to the junction point, the next wave is scanned from each helical element, thereby reinforcing the first wave. The constitutive coupling of these waves results from the resonance length of the rim.

Further details of the ring resonance and action of the plating sleeve 20 on the proximal end surface 12P of the core, which is responsible for the operation of the antenna with respect to the circularly polarized electromagnetic waves, are described in GB2346014A mentioned above. The sleeve and plating of this embodiment of the present invention are advantageous in that they provide both balun function and ring resonance, but ring resonance is applied to the feeder shielding conductor 16 to form an open-ended cavity, as in this embodiment. Rather than being in the form of a connected sleeve, they may be provided independently by connecting the helical elements 10A-10H to an annular conductor surrounding the core 12 with base and distal edges on the outer side of the core. Such conductors may be provided with loops provided by helical elements and their intermediate connections, provided that they have an electrical length corresponding to the wavelength in the tube of an integral multiple (1,2,3, ....) at the operating frequency. As long as the ring resonance still reinforces the resonance mode associated with these fields, and can form an annular track similar to the conductive tracks forming a helical track 10A-10H, the width can be relatively narrow.

With regard to the resonant action of the loops provided by the helical elements 10A-10H and their intermediate connections, they are coupled so that the antenna operates at a resonance mode sensitive to circular polarization signals at the operating frequency of the antenna. Each pair of helical elements 10A, 10E; 10B, 10F; 10C, 10G; 10D, 10H, with associated radial elements, have associated resonances within a single operating frequency band of the antenna, all of which are Likewise, they cooperate with each other to form a common circular polarization resonance. Different lengths of helical element and radial element combinations cause a 360 ° / n (45 °) phase difference between the currents in the other elements of each group 10A-10D, 10E-10H. In this resonant mode, the currents are connected on the one hand to the inner feed conductor 18 and on the other hand to each pair of helical elements 10A, 10E connected to the shielding conductor 16 by coupling conductors of the laminated board 19. 10B, 10F; 10C, 10G ;, 10D, 10H) and flow around the rim 20U. The sleeve 20 is trapped to prevent the flow of currents from the antenna elements 10A-10H to the shielding conductor 16 at the base end surface 12P of the core with plating on the base end surface 12P of the core. Act as.

The operation of dielectric mounted multi-filler helical antennas with balun sleeves is described in more detail in the aforementioned British patent applications GB2292638A and GB2310543A.

The feeder transmission line simply performs off-line functions with a characteristic impedance of 50 ohms for transmitting signals to the antenna element structure. First, as described above, the conductive shield conductor 16 cooperates with the sleeve 20 to act to provide common mode isolation at the point of connection of the feed structure to the antenna element structure. The length of the shielding conductor between (a) the connection with the plating 22 on the proximal end 12P of the core and (b) the connection to the conductors on the laminated board 19 is the dimensions of the bore 12B and The conductive sleeve at the outer surface of the shielding conductor 16, together with the dielectric constant of the material filling the space between the wall and the shielding conductor 16, is at least approximately 1/4 wavelength at the frequency of the antenna's required resonance mode, so that the conductive sleeve The combination of 20, plating 22 and shielding conductor 16 allow for stable currents at the connection of the feed structure to the antenna element structure.

Such a good antenna has an insulating layer surrounding the shield conductor 16 of the feed structure. Since this layer generally has a dielectric constant lower than that of the core and is air in this case, it reduces the influence of the core 12 on the electrical length of the shielding conductor 16 and thus the exterior of the shielding conductor 16. Reduces the influence of the core 12 on any longitudinal resonances associated with it. Since the resonant mode associated with the required operating frequency is characterized by voltage dipoles extending radially, ie transversely, of the cylindrical core axis, the effect of the low dielectric constant sleeve on the required resonant mode is at least in the preferred embodiment. It is relatively small because the eve thickness is significantly less than the core thickness. Therefore, it is possible to decouple the linear resonant mode associated with the shield conductor 16 from the desired resonant mode.

Details of the feed structure will now be described with reference to FIGS. 3, 4, 5A and 5B. The feed structure comprises a combination of coaxial 50 ohm wires 16, 17, 18 and a flat laminated board 19 connected to the distal end of the wire. The laminated board 19 is a double sided printed circuit board (PCB) that is laid flat in face-to-face contact with the end face 12D of the core 12. The maximum dimension of the PCB 19 is that the most of the radial feed connection elements 10AR, 10ER, as shown in FIG. 1, while the PCB 19 is completely within the periphery of the distal face 12D of the core 12. It is smaller than the diameter of the core 12 to be small enough not to cover the long part.

In the present embodiment, the PCB 19 is in the form of a disk located centrally on the end face 12D of the core. The diameter of the PCB is such that the PCB rests on the arcuate internal component coupling conductors 10AD and 10EH plated on the core end surface 12D. As shown in FIG. 4, the PCB has a substantial central hole for receiving the inner conductor 18 of the coaxial feeder transmission line. The three off-center holes accommodate the end lugs 16G of the shielding conductor 16. Lugs 16G are curved or “jogged” to assist in positioning PCB 19 relative to the coaxial feeder structure. All four holes are formed through. In addition, the peripheral portions 19P of the PCB 19 are plated, and the plating extends on the base surface and the end surface of the board.

The PCB 19 can be used on both sides in that it has a terminal conductive layer and a base conductive layer on opposite sides of the intervening insulating layer. Each conductive layer is etched into a respective conductor pattern, as shown in FIGS. 5A and 5B. Where the conductor pattern extends to the peripheral portions 19P and through holes of the PCB 19, the respective conductors in the different layers are interconnected by edge plating and hole plating, respectively. As can be seen from FIGS. 5A and 5B, the terminal conductive layer has a pair of pads 42P connected to the inner conductor 18 (when fixed in the central hole). These pads 42p are fan or sector-shaped conductor regions 42S connected to the lugs 16G of the shield conductor 16 of the feeder (when received in respective through vias). Surrounded by). The pads 42P and neighboring fan-shaped conductor regions are connected by a pair of chip capacitors 44 soldered to the distal end of the PCB 19, as shown in FIG. The capacitors together form a shunt capacitance between the shield conductor 16 and the inner conductor 18 of the feeder. Note that the terminal conductive layer (see FIG. 5B) has a corresponding sectored conductive region 46S that matches the sectored region 42S, and these two plating regions are the shield conductor 16 of the feeder and the arcuate inner conductor 10AD. ) And thus a shield connection (16) between the shield conductor (16) of the feeder and the helical elements (10A-10D). The cutouts 42C and 46C of the terminal conductive layer and the base conductive layer coincide with the gaps between the radial feed connection elements 10BR and 10CR, and distribute the distribution of currents between each group of helical elements 10A-10D. Promote.

The conductor pattern of the terminal conductive layer is formed from the connection with the inner feeder conductor 18 to the second pan or segment-shaped conductive region 42F, and to the plating outer periphery lying on the arcuate or partially annular conductor 10EH. The second conductor region 42L extends to 19P). In addition, the cutout 42C in the segmented region contributes to the uniform dispersion of currents in the respective helical elements 10E-10H. There is no corresponding underlying conductive region in the base conductive layer. The conductive region 42L between the plating peripheral portion 19P and the central hole 32 lying on the arcuate track 10EH is formed between the inner conductor 18 of the feeder and the other group of helical antenna elements 10E-10H. It acts as a series inductance.

The combination of the PCB 19 and the long feeder 1618 with the base surface of the PCB 19 in contact with the distal face 12D of the core, as described above, aligned over the arcuate interconnects 10AD, 10EH. When secured to this core 12, connections are made between the base tracks on the core end face 12D and the peripheral portions 19P to form a reactive matching circuit having a shunt capacitance and series inductance.

The connections between the feeders 16-18, the PCB 19, and the conductive tracks on the end face 12D of the core are made by soldering or bonding with a conductive adhesive. The feeder 16-18 and the PCB 19 together form a single feeder structure when the distal end of the inner conductor 18 and the shielding lugs 16G are soldered into respective vias of the PCB 19. Feeder 16-18 and PCB 19 together form a single feeder structure with an integrated matching network.

The shunt capacitance and the series inductance form a matching network between the distal end of the coaxial transmission line and the radiating antenna element structure of the antenna. The shunt capacitance and series inductance are provided by coaxial wires physically embodied as shielding conductors 16, insulating layers 17, and inner conductors 18 when connected to a radiofrequency circuit having a 50 ohm terminal at the proximal end of the coaxial line. Matching the impedance together, this coaxial line is matched to the impedance of the antenna element structure at its operating frequency or frequencies.

The far-field radiation pattern generated by the antenna described above for circularly polarized radiation at the operating frequency is substantially heart-shaped, as shown in FIG. At elevation angles above about 30 °, the antenna is substantially omni-directional, and at the ceiling 50 (on the axis of the antenna) the gain is approximately 3 dB greater than isotropic. The beam width defined by the gain within the gain range of 3 dB in the ceiling 50 is approximately 120 °, as shown by the 3 dB line 52 and the beam width limits 54. Similar results are obtained at other azimuth angles.

10A, 10B, 10C, 10D, 10E, 10F, 10H: antenna element
10AD, 10EH: arched conductor
10AR, 10BR, 10CR, 10DR, 10ER, 10FR, 10GR, 10HR: feed connection element
12: Core 12B: Bore
12D: distal face 12P: proximal face
16: shielding conductor 17: insulating layer
18: Internal conductor 19: Board
20: Sleeve 20U: Rim

Claims

In the dielectric-mounted multi-pillar antenna having an operating frequency exceeding 200MHz,
An electrically insulating core of solid material having a relative dielectric constant of at least 10 and occupying a major portion of the internal volume defined by the core outer surface, and at least two pairs of substantially helical conductive antenna elements spaced apart about an axis of the antenna; And a three-dimensional antenna element structure on or adjacent to the core outer surface, wherein each pair of antenna elements is effective near an N tube wavelength (where N is an integer and at least 2) at an operating frequency. An antenna that forms part of a conductive loop having an electrical length and has a 3 dB beamwidth for circular polarized radiation of at least 90 °.

The antenna of claim 1, wherein the relative dielectric constant of the solid material is at least 20.

The antenna of claim 1 or 2, wherein the 3dB beamwidth for the circularly polarized radiation is 120 °.

4. An antenna as claimed in any preceding claim, wherein the antenna element structure comprises at least three pairs of helical antenna elements.

5. The method of claim 1, wherein each of at least some of the substantially helical antenna elements are fully wound once about the antenna axis, wherein the antenna elements are substantially uniform around the antenna axis. Antennas spaced apart and substantially coaxial.

The method according to any one of claims 1 to 5,
The core has an outer cylindrical surface portion, a first end surface portion, and a second end surface portion facing opposite to the first end surface portion,
Each of the pair of helical antenna elements comprises two elongated conductive elements oppositely opposite each other in the outer cylindrical surface portion of the core,
The antenna includes a center feeder connection portion coupled to the first end surface portion,
The antenna element structure each comprising a plurality of radially extending connection elements on or adjacent to the first end face portion, coupling each of the helical elements to the feeder connection, the connecting element Length of the antenna is different for each of the helical antenna elements of the pair such that the electrical length of the conductive loop included in each pair is different.

The method of claim 6,
With four pairs of helical antenna elements,
The antenna further includes a pair of antenna element coupling nodes.
Each of the pair of helical antenna elements includes a first antenna element connected to one of the coupling nodes, and a second antenna element connected to another one of the coupling nodes, and the four first antenna elements are connected to a first antenna element. Are arranged side by side as antenna elements of a group, and the four antenna elements are arranged side by side as antenna elements of a second group,
The radially extending connecting elements of each group gradually decrease in length in a predetermined direction around the periphery of the first end surface portion, and the sense of the progression is the same for each group so that the lengths of the conductive loops An antenna adapted to create a monotonic progression around the core.

8. The device of claim 7, wherein the radially extending connecting elements form a portion of a conductive foil over the first end surface portion of the core or adjacent to the first end surface portion, the foils respectively being in each of the groups of helical elements. An antenna having two internal conductive arcs interconnecting the connected feeder coupling elements.

The antenna element structure of claim 1, wherein the antenna element structure comprises a common intermediate conductor conductor to which each of the antenna elements is connected and surrounds the core, wherein the common intermediate conductor conductor comprises: An antenna defining a conduction path around the core connected at substantially evenly spaced connection points.

10. An antenna according to claim 9, wherein the electrical length of the conductive path is substantially equal to the wavelengths in the tube of an integer (1, 2, 3, ...) corresponding to the operating frequency.

The antenna according to any one of claims 1 to 10, wherein the average axial range of the helical antenna elements is lambda / 4 or less, where lambda is the wavelength in air of electromagnetic waves at an operating frequency.

12. The antenna of claim 11 wherein the average axial range of the helical antenna elements is less than [lambda] / 6.

13. The antenna of claim 1 wherein the spacing between each pair of helical elements measured perpendicular to said axis is about one half of said average axial range of said helical elements.

14. An antenna as claimed in any preceding claim, having an operating frequency from 1616 MHz to 1626.5 MHz.

A portable wireless communication terminal comprising an antenna according to any one of claims 1 to 14.