JP2012532518A - Multi filler antenna - Google Patents

Abstract

  In a dielectric loaded multifilar helical antenna, a conductive phasing ring (16) is placed between the feed node and the helical radiating element to couple them together. The phasing ring includes an annular conductive path having an electrical length equal to the full wavelength at the operating frequency and resonates at that frequency. The helical element is coupled to the outer periphery of the phasing ring at each spaced coupling location. The helical element may include an open circuit or closed circuit elongated conductive track, or a combination of both. When the spiral element is a closed circuit track, these tracks are interconnected by a second resonant ring (60U), which is the same as the first resonant ring. Resonates at a frequency or at a different frequency. The present invention is applicable to both endfire and backfire helical antennas.

Description

  The present invention relates to a multi-filar antenna for circularly polarized radiation having an operating frequency in excess of 200 MHz, and primarily but not exclusively to a dielectric-loaded multi-filar antenna.

  Dielectric-loaded multifilar antennas are disclosed in WO 2006/136809, British Patent Application Publication No. 2442998A, European Patent Application Publication No. 1147571A, and British Patent Application Publication No. 2420230A, No. 2444388A. No. 2,437,998A and No. 2,445,478A. The entire disclosures of these patent publications are incorporated herein by reference. Such antennas are primarily intended to receive circularly polarized signals from, for example, Global Navigation Satellite System (GNSS), for example for positioning and navigation purposes, from satellites in a Global Positioning System (GPS) satellite configuration. ing. Other satellite-based services where such antennas are useful include L-band Inmarsat services 1626.5-1675.0 MHz and 1518.0-1559.0 MHz services, TerreStar® S-band services, ICO Global Communications S Band services and satellite phone services such as SkyTerra services are included. The S band service has a frequency band assignment in the range of 2000 MHz to 2200 MHz.

  According to a first aspect of the present invention, there is provided a dielectric-loaded multifilar antenna for circularly polarized radiation having an operating frequency greater than 200 MHz, wherein the antenna has a relative dielectric constant of at least 5. An electrically insulating substrate formed from a solid dielectric material, a pair of feed nodes, at least four elongated conductive radiating elements located on the substrate, and disposed between and coupled to the feed node and radiating elements A phasing ring formed by a closed loop that resonates at an operating frequency, wherein the radiating elements are coupled to the phasing ring at respective spaced coupling positions. In this way, the radiating element is fed through the phasing ring that has the effect of feeding the radiating element in phase progression, resulting in circular polarization characteristics. Typically, an antenna has a central axis and a phasing portion that includes conductive tracks located on and surrounding the axis. The phasing ring may be a continuous track or an open track. In the case of an open track, the ring includes at least a lumped reactance in series with a conductive track, typically a pair of capacitances, which together with the reactance form the closed loop described above. .

  Preferably, the phasing ring is circular, but other configurations are possible, including squares or other polygons and serpentine circles (ie, following a path that repeatedly deviates in and out of the circle).

  In a particularly preferred antenna according to the invention, the substrate is a cylindrical body having a cylindrical side surface and proximal and distal end surfaces. The phasing ring is preferably located at the proximal end face so that the antenna is an “endfire” antenna, ie, generates a circularly polarized radiation pattern with a maximum value in the distal direction. The feed node is very easily centered on the substrate itself or as part of the connection assembly associated with the end face carrying the phasing ring. In the preferred antenna, the feed node is coupled to the phasing ring at approximately diametrically opposite positions by respective feed connection conductors extending radially with respect to the cylindrical axis.

  The phasing ring is preferably dielectrically loaded by the substrate and has a single wavelength electrical length (ie 360 °). In a preferred antenna, the radiating element has a first end coupled to the phasing ring and a second end spaced from the phasing ring, the second end being an open circuit. In this case, the electrical length in each of the radiating elements is preferably a quarter wavelength or an odd integer multiple thereof at the operating frequency.

  In an alternative preferred embodiment, the antenna is a second conductive ring that also resonates at the operating frequency, in this case the second end of the radiating element, each having an electrical length of half wavelength or an integral multiple thereof. A second conductive ring linking the two.

  It is also possible to construct a “backfire” antenna in accordance with the present invention, with the phasing ring typically plated on the distal end face of the core. A second conductive ring that resonates at a different frequency may in this case surround the core on its cylindrical side. Such a ring may be formed as an annular edge of a conductive sleeve that extends around the proximal end of the core, the sleeve being part of an integral balun, as described in the above-mentioned prior patent publications. Form. Some of the radiating elements may be closed circuit and extend from the distal phasing ring to an open circuit end spaced from the second conductive ring, while other radiating elements are open circuit and distant Extending from the phased ring to the second ring. In this way, the antenna can be resonated at two distinct operating frequencies, each resonance being for circularly polarized radiation.

  According to a second aspect of the present invention, a dielectric-loaded multifilar antenna for circularly polarized radiation having an operating frequency greater than 200 MHz has a relative permittivity greater than 5 and is defined by an outer core surface. An electrically insulating core of solid material occupying most of the internal volume, a plurality of feed nodes, and an antenna element structure on or adjacent to the outer surface of the core, the plurality of elongated conductive antenna elements, and the elongated antenna elements And an antenna element structure that includes a ring coupled between the feed node and resonating at an operating frequency, wherein the elongated antenna element extends from the resonant ring in a direction away from the feed node.

  If the resonant phasing ring is associated with a first laterally extending surface portion, the elongated conductive antenna element may extend on the side portion from the ring toward the second laterally extending surface portion; Each such element is a spiral track on the cylindrical side of the core. The two feed nodes preferably constitute a balanced feed point represented by a conductive pad close to the central axis of the antenna, each such pad connected to the phasing ring by a respective inductive connection link to the antenna. Further includes a shunt capacitance coupled across the two feed nodes for matching purposes.

  The resonant phasing ring may include an annular conductive path on the side of the core at a location adjacent to the first laterally extending surface, the elongated conductive antenna element being helical and axial It extends to.

  According to yet another aspect of the present invention, a dielectric-loaded multifilar antenna for circularly polarized radiation having an operating frequency greater than 200 MHz has a relative permittivity greater than 5 and is defined by an outer core surface. An electrically insulating core of solid material that occupies most of the internal volume, a pair of feed nodes, an antenna element structure on or adjacent to the core outer surface, connected to the feed node, and a phasing ring And an antenna element structure including at least four elongated conductive elements coupled to the phasing ring at respective spaced points on the phase ring.

The antenna may form part of an antenna assembly that includes an antenna as described above with a balun coupled to the feed node. The assembly may instead have a differential amplifier with a differential input coupled to the feed node.

  In this specification, the term “radiation” refers to an element that, when applied to an antenna element, emits an electromagnetic field if the antenna is energized by a transmitter operating at the operating frequency of the antenna. Instead, it will be appreciated that when an antenna is coupled to the receiver, such elements absorb electromagnetic energy from the surroundings and then the antenna operates in reverse. Consequently, the specification and claims in this document containing the term “radiation” include within its scope antennas intended exclusively for use with receivers as well as antennas used for transmission.

1 is a perspective view of a first antenna according to the present invention as seen from one lateral and proximal end. FIG. FIG. 2 is a perspective view of a printed circuit board carrying a balun and front end radio frequency amplifier adapted to implement the antenna of FIG. 1. It is an equivalent circuit diagram of an antenna. It is an equivalent circuit diagram of an antenna. FIG. 6 is a perspective view of an antenna unit forming part of a second antenna according to the present invention, showing the unit viewed from one side and the proximal end. FIG. 4 is a perspective view of an antenna unit forming part of a second antenna according to the present invention, showing the unit viewed from one side and the distal end. FIG. 6 is a perspective view of a third antenna according to the present invention, viewed from one side and the distal end. FIG. 5B is a diagrammatic representation of a third antenna plated conductor using the same perspective as FIG. 5A. It is an axial sectional view of the feed structure of the third antenna. FIG. 7 is a detail of the feed structure shown in FIG. 6, showing the laminate substrate of the feed structure separated from the distal end of the transmission line feeder section. It is a figure which shows the conductor pattern of the conductive layer in the laminated substrate of a feeder structure. It is a figure which shows the conductor pattern of the conductive layer in the laminated substrate of a feeder structure. It is an equivalent circuit diagram. The third insertion loss of the antenna (S ₁₁₎ is a graph showing the frequency response. It is a figure which shows the modification of the distal end conductor pattern for 3rd antennas.

  The invention will now be described by way of example with reference to the drawings.

  Referring to FIG. 1, a first antenna according to the present invention includes an endfire dielectric loaded 12 wire filler antenna 10 having a cylindrical dielectric core 12, which typically has a dielectric constant of 36. Made of ceramic material with a rate.

  A semi-rotating spiral track 14 having the same extent in the axial direction is plated on the cylindrical outer surface portion 12, and each track has a central axis (not shown) of the antenna defined by the cylindrical side surface portion 12S of the core. A central elongated conductive radiating element is formed. The core has a proximal core surface 12P that extends perpendicular to the antenna axis and side 12S. This forms the end face of the antenna. The other end of the antenna is formed by a core distal surface portion 12D which also extends perpendicular to the antenna axis and forms another end face.

A conductive ring 16 is plated on the proximal core surface 12P. Helical radiating element 1
Each of 4 extends on an edge formed by the intersection of the proximal surface portion 12P of the core and the cylindrical side surface portion 12S to meet the outer periphery of the conductive ring 16 in the proximal surface portion 12P, and each of the spiral elements 14 Are uniformly distributed around the circumference of the ring.

  Adjacent to the distal end 12P of the core, the helical element 14 terminates at an open circuit end 14E. In this preferred embodiment of the invention, the helical elements 14 are all the same length, each having an electrical length of a quarter wavelength at the operating frequency of the antenna, but this length is a proximal conductive It is the length of each element from the connection part of each element with the property ring 16 to the open circuit end 14E. In practice, spiral element 14 includes an open-ended monopole spiral element array. In an alternative embodiment, element 14 may advantageously be a quarter turn helix rather than a half turn.

  The two feeding connection conductors 18A, which extend radially inward from the inner periphery of the conductive ring 16 and are plated on the proximal core surface portion 12P, are connected to the conductive ring 16 at diametrically opposite positions. 18B. The inner ends of the feed connection conductors, ie the two ends of these conductors adjacent to the central axis of the antenna, form a feed node that constitutes a balanced feed connection for the antenna. Each feeding connection conductor 18A, 18B forms a series inductance at the operating frequency of the antenna. Bridging the feed node formed by the inner ends of the feed connection conductors 18A, 18B is a shunt capacitor 20 that forms a reactive matching network with the series inductance described above. A pair of metal spring connectors 22 extend from near the feed node to connect the antenna to receiving and / or transmitting circuitry.

  The electrical length of the conductive ring 16 is one wavelength at the operating frequency of the antenna, that is, 360 °. It therefore resonates at the operating frequency as follows. That is, when driven by a signal at the operating frequency from the spiral element 14 (when the antenna is used to receive a signal) or from the feed node (when the antenna is used for transmission), the resonant current is Resonates to circulate in the conductive ring 16 and thereby resonate the antenna around the conductive ring 16 and around the proximal end of the helical element 14 in a circularly polarized mode due to the resulting phase progression. To do. Thus, due to the current amplitude and phase distribution in the element 14, the phasing of the helical element 14 effectively synthesizes the rotating dipole and thus provides the desired circular polarization characteristics.

  Thus, in practice, the conductive ring 16 is topologically speaking a phasing ring between the feed node and the radiating element, which is driven from the feed node via this intermediate phasing ring. Is done. (Note that the feed node is inside the conductive ring 16 while the radiating element is outside.)

  In this embodiment of the invention, the conductive ring 16 is uninterrupted. However, as will be described below, it is also possible to have two open circuits, bridged with capacitors, which form part of an alternative matching network.

As shown, the conductive ring is preferably circular, but this is not essential. There are 12 spiral radiating elements in this embodiment, but smaller numbers may be used, for example 10, 8, 6, or 4. However, a common feature is that the phasing ring forms a closed conductive loop that resonates at the operating frequency. Thus, the ring 16 defines the phasing of the helical element 14 in this case, although all of the elements have the same length and configuration. In particular, when embodied as a plated conductor or conductor portion on a substrate formed by the core 12, the use of a resonant ring in this way can be produced at a relatively low cost compared to a lumped phase network. A particularly stable phasing element is formed that maintains an excellent manufacturing yield. In this example, the antenna impedance at the feed node is relatively low (typically a few ohms) using the quarter-wave helical element 14. As described above, the feeding node forms a balanced feeding point. If the antenna is to be used with a single-ended receiver front end, the antenna may be connected to a printed circuit board mounted with a dedicated balun circuit, as shown in FIG. Referring to FIG. 2, the receiver front end circuit board 30 has a printed track 32 for connection to the proximal pin 22 (FIG. 1) of the antenna. The track 32 forms a connection between the antenna and the balun circuit, which can be obtained from Johnson Technology, Inc. (Camarillo, CA90312, USA) may be a balun unit selected from a range manufactured under model number BL15. Balun circuit 34 provides a single-ended output for radio frequency front-end amplifier 36, which is also mounted on printed circuit board 30.

  The radiation pattern of the antenna is a conventional dielectric loaded quadrifilar antenna in that it is cardioid shaped, has a distal axial maximum, and is nearly omnidirectional in orientation. Is similar to the pattern shown by

  As shown by the equivalent circuit of FIGS. 3A and 3B, the matching network of the antenna of FIG. 1 is a series inductance shunt capacitance type. 3A shows the conductive ring 16 as a loop, each feed connecting conductor 18A (FIG. 1) is represented by an inductance L, and the capacitor 20 (FIG. 1) appears as a shunt capacitance C across the feed node F. Yes. Referring to FIG. 3B, the phasing ring and associated helical element may be represented by a resistor R. The equivalent circuit of FIG. 3B is shown as a balanced arrangement. Typically, when measured at the feed node F, the source impedance represented by the antenna and matching network is 50 ohms.

  4A and 4B, the second antenna according to the present invention has two phasing rings for additional phasing stability. For simplicity, in the proximal view of FIG. 4A, the plated conductor on the proximal end face portion 12P of the core is shown without connection pins and shunt matching capacitors. In practice, the antenna includes these components as described above in connection with FIG. The artwork of the proximal end face 12P is substantially the same as that of the first antenna described above with reference to FIG. However, in this embodiment, the helical elements 14 each have substantially full rotation about the core 12, and as shown in FIG. 4B, an edge formed by the intersection of the cylindrical side surface 12S and the distal end surface portion 12D. The top extends to a second conductive ring 40 plated on the distal end face 12D. In an alternative embodiment, the helical element is a semi-rotating element.

  The electrical length of each helical element 14 in this embodiment is a half wavelength at the antenna operating frequency. In this antenna variation, the spiral element may have an electrical length that is an integer multiple of full wavelength or higher and half wavelength. As in the first antenna described above in connection with FIG. 1, the electrical length of the proximal conductive ring 16 is full wavelength, ie 360 °. In this antenna, the distal conductive ring 40 is sized identically. However, it is possible to arrange for the electrical lengths of the two conductive rings to be different and broaden their resonant frequency, thereby increasing the bandwidth of the antenna.

  For a given core material and core diameter, the core 12 of this second antenna is longer and heavier than the core of the first antenna, but the second phasing ring provides greater phasing stability. I will provide a.

Referring to FIGS. 5A and 5B, a third antenna according to the present invention has 10 elongate antenna elements, comprising an antenna element structure comprising 10 elongate antenna elements constituted by two groups of such elements. A decafilar spiral antenna having one group includes a plurality of closed circuit spiral conductive tracks 50A, 50B, 50C, 50D, 50E, 50F, and another group includes a plurality Open circuit conductive tracks 51A, 51B, 51C, 51D, all of which are plated on the cylindrical outer surface 52 of the solid cylindrical core 52 or otherwise metallized. In FIG. 5B, the core and other components are omitted for clarity.

  The core is made of a ceramic material. In this case, it is a titanate material with a dielectric constant around 36. In this embodiment, intended for operation in the GPS L1 and L2 bands (1575.42 MHz and 1227.6 MHz), the core diameter is 14 mm. The core length of 17.75 mm is longer than the diameter, but in other embodiments it may be shorter than the diameter.

  This third antenna has a backfire in that it has a coaxial transmission line feeder housed in an axial hole (not shown) that passes through the core from the distal end face 52D to the proximal end face 52P of the core. It is a spiral antenna. Both end faces 52D and 52P are flat and perpendicular to the central axis of the core. In this embodiment of the invention, they are oriented in the opposite direction in that one is oriented distally and the other is oriented proximally. The coaxial transmission line is a rigid coaxial feeder housed in the center of the hole so that the outer shield conductor is spaced from the wall of the hole so that a dielectric layer is effectively present between the shield conductor and the core 52 material. To. Referring to FIG. 6, the coaxial transmission line feeder has a conductive tubular outer shield 56, a first tubular void or insulating layer 57, and an elongated inner conductor 58 insulated from the shield by the insulating layer 57. The shield 56 has an integrally formed spring tongue 56T or spacer that protrudes outwardly, which separates the shield from the sidewall of the hole. A second tubular void exists between the shield 56 and the sidewall of the hole. Alternatively, the insulating layer 57 may be formed as a plastic sleeve, similar to the layer between the shield 56 and the hole wall. At the lower proximal end of the feeder, the inner conductor 58 is centered within the shield 56 by an insulating bush (not shown), as described in the above-mentioned WO 2006/136809 by the applicants. Placed in.

The combination of shield 56, inner conductor 58 and insulating layer 57 is to couple the distal ends of spiral tracks 50A-50F, 51A-51D to the radio frequency (RF) circuit of the device to which the antenna is to be connected. In addition, a transmission line having a predetermined characteristic impedance (here, 50 ohms) passing through the antenna core 52 in an axial hole (not shown) is formed. The coupling between the antenna elements 50A-50F, 51A-51D and the feeder is made through conductive connections associated with the spiral tracks 50A-50F, 51A-51D, which are connected to the core 52. Formed as short radial tracks 50AR, 50BR, 50CR, 50DR, 50ER, 50FR, 51AR, 51BR, 51CR, 51DR plated on the distal end face 52D. Each connection extends from the distal end of the respective helical track to the outer edge of the distal conductive phasing ring 16 plated on the core distal surface 52D adjacent to the end of the axial hole in the core. . As can be seen from FIG. 5B, the phasing ring 16 has a core distal surface 52D and a helical track 50A that are more than the central axis and axial transmission line feeder section of the antenna (as described above in connection with FIG. 6). -50F, closer to the periphery of the proximal end of 51A-51D. In this embodiment of the invention, the phasing ring 16 has an average diameter of 11 mm and an electrical length equivalent to all wavelengths at a first operating frequency of 1575.42 MHz, ie 360 °. The open circuit spiral tracks 51A-51D also resonated at the first operating frequency of the antenna 1575.42 MHz and were angularly spaced by their respective connections 51AR-51DR, as shown in FIG. 5B. Connected to the distal phasing ring 16 in part. They are not exactly evenly distributed around the phasing ring 16, but the dispersion causes the four open circuit elements to generate a circularly polarized response in this first resonant mode of the antenna. Uniform enough to synchronize.

  Closed circuit spiral tracks 50A-50F representing the second group of radiating elements resonate at a GPS L2 frequency of 1227.60 MHz, which is the second lower operating frequency representing the second resonant mode of the antenna. As will be described below, they are also connected to the distal phasing ring 16 in their angularly spaced locations by their respective connections 50AR-50FR.

  As will also be described below, the distal phasing ring 16 is connected to the shield and inner conductor of the axial transmission line section via a matching network by conductors on the laminate substrate 59 secured to the core distal surface 52D. 16, 18. Both the coaxial transmission line feeder section and the laminate substrate 59 include a single feed structure prior to assembly into the core 52, and their interrelationship can be seen by comparing FIGS. 5A and 6.

  The electrical length of the phasing ring 16 is also determined by factors including its physical path length, the relative permittivity of the core material, and the configuration, placement and material of the laminated substrate 59.

  Referring again to FIG. 6, the transmission line feeder inner conductor 58 has a proximal portion 58P protruding as a pin from the proximal face 52P of the core 52 for connection to the device circuitry. Similarly, a proximal end integral lug (not shown) on shield 56 projects beyond core proximal surface 52P for connection to the device circuit ground.

  The proximal ends of the six closed circuit spiral tracks 50A-50F in the first group are interconnected by a common virtual ground conductor 60. In this embodiment, the common conductor is a second annular phasing ring and is in the form of a plated sleeve that surrounds the proximal end of the core 52. This sleeve 60 is in turn connected to the shield conductor 56 of the feeder, in which case the feeder emerges from the vicinity of the core by means of a plated conductive coating 62 on the proximal end face 52P of the core 52 (FIG. 1). ).

  The first group of six closed circuit spiral tracks 50A-50F are of different lengths, and each set of three elements 50A-50C, 50D-50F has a sleeve edge 60U generally the core proximal end face 52P. As a result of having a variable distance from, it has elements of slightly different length. When the shortest elements 50A, 50D are connected to the sleeve 60, the edge 20U is a little further away from the proximal surface 52P than when the longest antenna elements 50C, 50F are connected to the sleeve 60. The different lengths of the conductive path including the closed circuit spiral tracks 50A-50F in this case cause the antenna to operate in a second resonant mode where the antenna is sensitive to circularly polarized signals at the GPS L2 frequency, 1227.60 MHz. In some cases, this results in a phase difference between the currents in the elements in each set 50A-50C, 50D-50F of the three elements. In this mode, current is connected to the elements 50D, 50E, 50F connected to the distal phasing ring 16 on one side of the core 52, and to the distal phasing ring 16 on the other side of the core 52. It flows around the edge 60U of the sleeve 60 between the other set of elements 50A, 50B, 50C.

  The conductive sleeve 60, the plating 62 on the proximal end face 52P, and the outer shield 56 of the feeder lines 56, 58 together form a quarter wave balun, which is installed by the antenna. Provide common mode isolation of antenna element structures from devices that are sometimes connected. The balun converts the single-ended current at the proximal ends of the feeder lines 56, 58 into a balanced current at the distal end that appears at the distal end face portion 52D of the core 52.

Edge 60U of the sleeve 60, has an electrical length of lambda _g2, lambda _g2 is the guide wavelength for the current passes around the edge 60U at the second frequency of the resonant modes of the antenna, so that the edges, It shows ring resonance at that frequency. The operation of the sleeve edge 60U as a resonant element is described in more detail in the above-mentioned EP 1147571A.

  Although the sleeve 60 and plating 62 of this embodiment of the present invention is advantageous in that they provide both balun function and ring resonance, ring resonance also makes the sleeve a feeder shield as in this embodiment. Rather than being configured to connect to conductor 56 to form an open-ended cavity, as in the embodiment described above in connection with FIGS. 4A and 4B, a second group of spiral tracks 50A-50F surrounds core 52, It can also be provided independently by connecting to an annular conductor having both proximal and distal edges on the outer face of the core. Such conductors may be relatively narrow as long as they can form an annular track that is similar in width to the conductive tracks forming the spiral tracks 50A-50F, 51A-51D, and that is the operating frequency of the antenna. The ring resonance that reinforces the resonance mode associated with the loop provided by the closed circuit spiral tracks 50A-50F and their interconnections, i.e., the second resonance mode. Generate.

  It will be appreciated that the edge 60U of the sleeve 60 acts as a second proximal phasing ring that reinforces the circularly polarized resonance at a lower operating frequency, ie 1227.60 MHz. As described above, the sleeve edge 60U may be located on the outer cylindrical surface portion 52C of the core 52, whereas in another variation, a phasing ring is formed that is completely located on the proximal end face portion 52P. To do so, the balun may include a disk-like conductor alone on the proximal surface 52P of the core 52, and a second group of spiral tracks 50A-50F may extend on the proximal surface portion 52P of the core 52. .

  The sleeve 60 and proximal surface plating 62 serve as a trap that prevents current flow from the closed circuit spiral tracks 50A-50F to the shield 56 of the feedline on the proximal end face 52P of the core. The closed circuit spiral so that each subset of the closed circuit spiral track typically has one long track 50C; 50F, one intermediate length track 50B; 50E, and one short track 50A; 50D. It is noted that the conical tracks 50A-50F may be viewed as two subsets of three helical tracks interconnected by the distal phasing ring 16.

(A) shortest closed circuit spiral track 50A, 50D and sleeve edge 60U, (b) intermediate length closed circuit spiral track 50B, 50E and sleeve edge 60U, and (c) longest closed circuit spiral track 50C. , 50F and sleeve edge 60U, respectively, that run between the opposite sides of the phasing ring 16, are respectively the in-tube wavelengths along the loop at the frequency of the second resonance mode. _It has an effective electrical length approximately equal to _g2 . These radiating elements are half-rotating elements and have the same extent on the cylindrical surface portion 52C of the core. The configuration of the closed circuit spiral tracks 50A-50F and their interconnection is such that they operate in the same manner as a simple dielectric loaded six-wire spiral antenna, the operation of which is described above in the UK This is described in more detail in US Pat. No. 2,445,478A.

In contrast to the closed circuit spiral tracks 50A-50F, the other spiral conductor tracks 51A-51D are positioned between the distal end face 52D of the core and the sleeve edge 60U, as shown in FIGS. 5A and 5B. And has an open circuit proximal end on the core cylindrical surface 52C. The arrangement of these open circuit spiral tracks is such that they are also evenly distributed around the core and interleaved between the closed circuit tracks 51A-50F, with each open circuit track 51A-51D being approximately centered about the axis of the core. It is made to make a half turn. Since they are evenly distributed around the axis of the core, the open circuit spiral tracks 51A-50D are generally aligned with orthogonal track pairs 51A, 51D.
C; 51B and 51D are included. Each open circuit track 51A-51D together with its respective radial connection element 51AR-51DR on the core distal end face 52D forms a quarter-wave three-wave monopole in the following sense. That is, in this embodiment, the electrical length of each track is 4 of the in-tube wavelength λ _g1 along the track, especially at the frequency of the first circularly polarized resonance mode of the antenna determined by the length of each open circuit element. It means that it is almost equal to 3 minutes. In this embodiment, the frequency of the first circular polarization resonance mode is the GPS L1 frequency 1575.42 MHz.

  As with the closed circuit spiral conductor tracks 50A-50F, the open circuit tracks 51A-510 also exhibit small differences in physical and electrical length. Thus, the open circuit track includes a first pair of diametrically opposite tracks 51A, 51C that is longer than the second pair of diametrically opposite tracks 51B, 51D. These small variations in length help in synthesizing a rotating dipole at the frequency of the first circular polarization resonant mode, with their respective resonances being phase forward and phase delayed.

Note that in this embodiment of the invention, the frequency of the first resonance mode is higher than the frequency of the second resonance mode. In other embodiments, the opposite may be true. Although fundamental or harmonic resonance of a spiral element may be used, in general, closed circuit elements have an average electrical length of nλ _g2 / 2 and open circuit elements are (2m−1) λ _g1 / 4. It has an average electrical length, where n and m are positive integers.

  Since the system of monopole elements formed by the open circuit spiral tracks 51A-51D and their respective radial tracks 51AR-51DR has no connection to the sleeve edge 60U, the first circularly polarized resonance mode is It is determined independently of the ring resonance of the edge 60U. However, the distal phasing ring 16 and balun formed by the sleeve 60, the feeders 56, 58 and their plating layer 62 on the proximal end face 52P of the core (which reduces the self-capacitance effect of the shield conductor 56). Interconnection improves the matching of quadrifila monopoles 51A-51D, thereby producing a stable circularly polarized radiation pattern in the first resonant mode. Furthermore, as a result, the tolerance of monopole length is not as important.

  In this specification, the terms “radiation” and “radiating” should be broadly interpreted in the following sense. That is, when applied to antenna characteristics or elements, they are the characteristics or elements of the antenna that are related to the radiation of energy when the antenna is used with a transmitter, or when the antenna is used with a receiver, It is meant to refer to a characteristic or element related to the absorption of energy from the surroundings.

With respect to two sets of five spiral tracks 50A, 51A, 50B, 51B, 50C; 50D, 51C, 50E, 51D, 50F connected to the distal phasing ring, closed circuit tracks 50A, 50B around the core, respectively , 50C; 50D, 50E, 50F and the sequence of open circuit tracks 51A, 51B; 51C, 51D are made symmetrical with respect to the centerline CL1; CL2 (see FIG. 5B). In other words, for each feed coupling node, the sequence is mirrored to the respective centerline. More specifically, the arrangement of spiral tracks is for spiral track elements connected to each feed coupling node, where they include pairs of adjacent antenna elements, each pair comprising one closed circuit antenna element and The sequence of antenna elements is designed to include one open circuit antenna element, and in a given direction around the core, the number of pairs in which the closed circuit element precedes the open circuit element is the same. Is equal to the number of pairs preceding the closed circuit element. In this context, note that each such “pair” of elements may include at least one element that is also another such pair of elements, and antennas coupled to one side of the distal phasing ring 16. The element includes four pairs 50A, 51A; 51A, 50B; 50B, 51B and 51B, 50C. Of these four pairs, the closed circuit element precedes the open circuit element when viewed in sequence in the counterclockwise direction from the top of the antenna (ie, from a location located distal to the distal core surface 52D). There are two pairs 50A, 51A; 50B, 51B, and two pairs 51A, 50B; 51B, 50C, where the open circuit element precedes the closed circuit element, thereby equal as specified above. Satisfy the condition of a number pair. The same applies to the antenna element connected to the other side of the phasing ring 16. Thus, there are two pairs 50D, 51C; 50E, 51D in which the closed circuit element precedes the open circuit element, and two pairs 51C, 50E; 51D, 50F in which the open circuit element precedes the closed circuit element. This ordering of closed and open circuit elements has been found to produce an excellent antenna radiation pattern compared to an antenna that does not meet this condition.

  It is possible to satisfy the condition with an antenna having only four closed circuit elements and four open circuit elements. However, a combination of six elements of one type and four elements of the other type, ie in this case six closed circuit elements and four open circuit elements, is preferred. This is because a more uniform spacing between the elements of each group 50A-50F; 51A-51D can be obtained. Thus, if in any given plane perpendicular to the antenna axis, a complete set of antenna elements 50A-50F, 51A-51D is evenly distributed around the core, closed circuit spiral tracks 50A-50F Has an angular spacing of 72 ° (for 4 track pairs) and 36 ° (for 2 track pairs). The maximum deviation from the optimal interval of 60 ° is 24 °. For the four open circuit spiral tracks 51A-51D, the inter-element angular spacing is 72 ° and 108 °. That is, a deviation of only 18 ° from the optimal value of 90 °.

  Impedance matching is performed by a matching network embodied in a stacked printed circuit board (PCB) assembly 59 mounted directly on the distal end face 52D of the core, as shown in FIG.

  As shown in FIG. 6, the PCB assembly 59 forms a part of a power supply structure in which power supply lines 56 and 58 are incorporated.

  Feed lines 56, 58 perform functions other than the mere function of a line having a characteristic impedance of 50 ohms for transmitting signals to or from the antenna element structure. First, as described above, the shield 56 works with the sleeve 60 to provide common mode isolation at the connection point of the feed structure to the antenna element structure. The length of the shield conductor between (a) the shield conductor connection to the plating 62 on the proximal end face 52P of the core and (b) the shield conductor connection to the conductor on the PCB assembly 59 is Along with the dimensions of the directional hole (where the feeder transmission line is accommodated) and the dielectric constant of the material that fills the space between the shield 56 and the hole wall: That is, the electrical length of the shield 56 on the outer surface of the shield is approximately a quarter wavelength at each of the two required resonance mode frequencies of the antenna, resulting in the conductive sleeve 60, the plating 62 and the shield 56 being The combination is adapted to generate a balanced current at the connection of the feed structure to the antenna element structure.

In this preferred antenna, an insulating layer surrounds the shield 16 of the feed structure. This layer has a dielectric constant lower than the dielectric constant of the core 52 and is an air layer in the preferred antenna, but any longitudinal resonance relative to the electrical length of the shield 56 and thus outside the shield 56. Again, the influence of the core 52 is reduced. Since the resonant mode related to the required operating frequency is characterized by a voltage dipole extending diametrically, i.e. transversely to the cylindrical core axis, the influence of the low dielectric constant sleeve on the required resonant mode is at least in the preferred embodiment the sleeve Is relatively small because the thickness of the core is considerably less than the thickness of the core. Accordingly, the linear resonant mode associated with shield 56 can be decoupled from the desired resonant mode.

  As described above, the antenna has a resonance frequency determined by the effective electrical length of the helical antenna elements 50A-50F; 51A-51D. The electrical length of the element for a given resonant frequency also depends on the relative permittivity of the core material, and the antenna dimensions are significantly reduced for an air-centered quadrifilar antenna. Since the phasing ring is plated on the core material, their dimensions are also significantly reduced relative to the full wavelength air ring.

  The antenna according to the invention is particularly suitable for dual-band satellite communications above about 1 GHz. In this case, the second group of helical antenna elements 50A-50F has an average longitudinal extent (ie, a range parallel to the central axis) of about 16 mm, whereas the first group of helical antenna elements. 51A-51D has an average longitudinal extent of about 15.5 mm. The length of the conductive sleeve 20 is typically around 1.75 mm. This results in a quarter wave balun at approximately the frequency of the two frequency operating bands. This dimension is not critical. In practice, the sleeve length is set to provide a quarter-wave balun operation, often at any intermediate frequency, depending on either of the two center frequencies or the spacing between the center frequencies. May be. In general, it is desirable for the sleeve to form a quarter wave balun in the middle of the center frequency.

  The exact dimensions of antenna elements 50A-50F and 51A-51D can be determined at the design stage based on trial and error by attempting empirical optimization until the required phase difference is obtained. The diameter of the coaxial transmission line in the axial hole of the core is around 2 mm.

  Here, further details of the feeding structure will be described. As shown in FIG. 6, the feed structure includes a combination of coaxial 50 ohm feed lines 56, 57, 58 and a planar laminated substrate assembly 59 connected to the distal end of the line. The PCB assembly 59 is a multilayer printed circuit board located in flat direct contact with the distal end face 52D of the core 52. As shown in FIG. 1, the maximum dimension of the PCB assembly 59 is smaller than the diameter of the core 52 so that the PCB assembly 59 is completely within the periphery of the distal end face 52D of the core 52.

  In this embodiment, the PCB assembly 59 is in the form of a disc located in the center of the distal surface 52D of the core. The diameter is such that the outer circumference overlaps the distal phasing ring 16 plated on the core distal surface 52D. As shown in the exploded view of FIG. 6A, the assembly 59 has a substantially central hole 72 that houses the inner conductor 58 of the coaxial feeder transmission line. Three eccentric holes 74 house the distal lugs 56G of the shield 56. The lug 56G is bent or “curved” to assist in positioning the PCB assembly 59 relative to the coaxial feeder structure. All four holes 32, 34 are plated to the inside. Further, the portion 59P around the assemblies 59A, 59PB is plated, and the plating extends to the proximal and distal surfaces of the laminated substrate.

The PCB assembly 59 has a laminated substrate in that it has an insulating layer and three patterned conductive layers. Additional insulating and conductive layers may be used in alternative embodiments of the invention. As shown in FIG. 6A, in this embodiment, there are two outer conductive layers including a distal layer 76 and a proximal layer 78 separated by insulating layers 80A, 80B. These insulating layers 80A and 80B are made from an FR-4 glass reinforced epoxy substrate. There is an intermediate conductor layer 81 between the insulating layers 80A and 80B. The distal and proximal conductor layers are etched with their respective conductor patterns as shown in FIGS. 7A and 7B, respectively.
When the conductor pattern extends to the peripheral portions 59PA, 59PB of the laminated substrate and to the plated through holes 72, 74, the respective conductors in the different layers are interconnected by edge plating and hole plating, respectively. As can be seen from the drawing showing the conductor pattern of the conductor layers 76, 78, the distal conductive layer 76 has elongated conductor tracks 36L1, 36L2, which are connected to the inner feeder conductor 58 (that is, Is connected to the first peripheral plating edge portion 59PA of the substrate via the first fan-shaped current distribution conductor 86A that spreads outward with low inductance. The fan-shaped conductor 86A is formed at the outer end thereof by the first plating peripheral edge portion 59PA, but forms an angle of 90 ° with respect to the core axis. The elongated track between the inner feed conductor 58 and the sector conductor 86A is two parts 76L1, 76L2, which constitute an inductance at the operating frequency of the antenna because of their relatively narrow and elongated shape. To do. Since the first peripheral edge 59PA is connected to the distal ring 16 in the region of half radial conductors 50DR, 50ER, 50FR, 51CR, 51DR in the core distal end face 52D (FIG. 5A), these inductances are , In series between the inner feed line conductor 18 and two of each helical antenna element, ie each group 50A-50F; 51A-51D.

  When the feeder shield 56 is housed in a hole 74 in the laminated substrate, the second outer fan-shaped current distribution conductor 86B (which also has a low inductance due to its relatively large area) opposes the substrate. It is directly connected to the peripheral plating edge portion 59PB on the side. Thus, the shield is substantially directly connected to the phasing ring 16 in the region of the other radial conductors 10AR, 50BR, 50CR, 51AR, 51BR. The second sector conductor 86B extends along the inductive elongated tracks 36L1, 36L2 toward the first sector conductor 86A and provides a pad for discrete shunt capacitance. Thus, in this embodiment, the second sector conductor 86B has two extensions 76FA, 76FB that run parallel to the inductive tracks 76L1, 76L2 on the opposite side. Each extension 76FA, 76FB is formed as a much wider track compared to the central inductive track and thus has a negligible inductance. One of these extensions 76FA is connected to the first chip capacitor 82-1 connected to the plating associated with the central hole 72, and the second connected to the junction between the two inductive track portions 76L1, 76L2. The pad for the chip capacitor 82-8A is provided. The other extension 36FB provides a pad for the third chip capacitor 82-2B that is similarly connected to the junction between the inductive track portions 76L1, 76L2. In this embodiment of the present invention, the capacitors 82-1, 82-2A, and 82-2B are 0201 size chip capacitors (for example, GJM manufactured by Murata Manufacturing Co., Ltd.). Note that because it is on the distal face of the laminated substrate 59, the sector conductors 86A, 86B are spaced from the core distal end face 52P and are therefore less loaded by the core dielectric material.

  The above combination constitutes a bipolar reactive matching network schematically shown in FIG. The network comprises (a) partial circuits 100, 101, respectively representing a source constituted by closed circuit spiral elements 50A-50F and associated components, and a source constituted by open circuit spiral elements 51A-51D and associated components, respectively. (B) provide dual-band matching with 50 ohm load 102; In this example, feed lines 56-58 (FIGS. 6 and 6A) are 50 ohm coaxial line sections 104. Inductors L1 and L2 are formed by the track sections 76L1, 76L2 referred to above. Shunt capacitance C1 is the capacitance shown as capacitor 82-1 in FIGS. 6A and 7A. The other shunt capacitance C2 is formed by the parallel combination of the two chip capacitors 82-2A, 82-2B described above in connection with FIG. 7A. By using two capacitors for the second capacitance C2, it is possible to obtain a relatively high capacitance value using a thin chip capacitor, and resistance loss is reduced.

  The conductor pattern of the intermediate conductive layer 81 is in the form of a single ring spaced from the peripheral edge conductors 59PA, 59PB and from the vias represented by the plated holes 72,74. This ring or washer limits the electromagnetic field associated with the phasing ring 16, thereby lowering its resonant frequency to the first operating frequency.

  Connections between the feed lines 56, 58, the PCB assembly 59, and the conductive tracks on the core distal surface 52D are made by soldering or by bonding with a conductive adhesive. Feed lines 56-58 and assembly 59 are united together when the distal end of inner conductor 58 is soldered in laminated substrate via 72 and shield lug 56G is soldered in each eccentric via 74. Form a feeder structure. Feed lines 56-58 and PCB 59 together form a single feed structure with an integral matching network.

  The network formed by the series inductances L1, L2 and the shunt capacitances C1, C2 has a radiating antenna element structure of the antenna and a 50 ohm termination at the proximal end of the transmission line section when connected to the radio frequency circuit. This 50 ohm load impedance is matched to that impedance at the operating frequency of the antenna element structure. The parallel impedance represented by the matching network also has beneficial effects and improved respective radiation patterns that allow wider tolerances for the monopole antenna elements 51A-51D.

  As described above, the feeding structure is assembled as a unit before being inserted into the antenna core 52, and the laminated substrate of the assembly 19 is fixed to the coaxial line 16-18. Subsequent steps in manufacturing the third antenna are as described in the above-mentioned WO 2006/136809 pamphlet.

Using the above structure, it is possible to generate a dual-band circularly polarized frequency response, and the antenna insertion loss vs. frequency graph is generally as shown in FIG. The antenna has a first band concentrated at the upper resonance frequency f ₁ and a second band concentrated at the lower resonance frequency f ₂ . In this antenna, the frequency separation f ₂ -f ₁ of the _two center frequencies is about 25 percent of the average frequency ½ (f ₁ + f ₂ ). It has an antenna radiation pattern mainly oriented upwards with respect to right-handed circular polarization in both bands.

  It will be appreciated that the antenna according to the invention can be applied to left-handed circularly polarized waves. One service using left-handed circular polarization is a GlobalStar voice and data communications satellite system having a handset-to-satellite transmission band centered at about 1616 MHz and another satellite-to-handset transmission band centered at about 2492 MHz. It is.

What has been described above is a possible configuration in which the phasing ring 16 is discontinuous with an open circuit bridged by a capacitor. Such a deformation provides greater flexibility in selecting the resonant frequency of the phasing ring within a given space. Further, the capacitor may form part of an alternative impedance matching network. Such a variation is shown in FIG. 10, which is plated with a phasing ring 16 on the end face of a cylindrical core 52 with two open circuits bridged by respective capacitors 120. It is a top view of the done end surface. As described above in connection with FIGS. 5A and 5B, in this variant, the phasing ring is connected around its outer periphery to ten helical radiating elements using short radial connections. The feeding structure is not shown in FIG. In practice, a PCB matching network having the same general physical configuration as described above may be used. Alternatively, inwardly extending radial feed connection conductors 18A, 18B couple the phasing ring 16 directly to an axially located transmission line feeder or, in the case of an endfire antenna, in conjunction with FIG. It is directly coupled to the circuit board positioned in the axial direction as described above.

Claims (28)

A multifilament antenna for circularly polarized radiation having an operating frequency exceeding 200 MHz,
An electrically insulating substrate;
A pair of power supply nodes,
At least four elongated conductive radiating elements located on the substrate;
A phasing ring formed by a closed loop that resonates at the operating frequency and is disposed between the feed node and the radiating element to couple them together;
Including
The radiating elements are coupled to the phasing ring at respective spaced coupling positions;
Multi filler antenna. The antenna has a central axis;
The phasing ring includes a conductive track located on the substrate and surrounding the axis;
The antenna according to claim 1. The phasing ring includes a continuous annular conductor;
The antenna according to claim 1 or 2. The phasing ring includes at least one pair of concentrated reactances in series with the conductive track portion;
The conductive track portion forms the closed loop that resonates with the reactance at the operating frequency.
The antenna according to claim 1 or 2. The substrate is formed of a solid dielectric material having a dielectric constant of at least 5 and has a cylindrical side surface and a cylindrical body having proximal and distal end surfaces;
The solid material of the core occupies a majority of the internal volume defined by the outer surface of the core;
The phasing ring is located on one of the end faces,
The feed node is coupled to the phasing ring at a position that is centrally located and generally diametrically opposed by a respective feed connection conductor extending substantially radially of the cylindrical axis;
The antenna as described in any one of Claims 1-4. The phasing ring is circular,
The antenna according to claim 5. The substrate is a cylinder having a cylindrical side and proximal and distal end faces;
The phasing ring is located on one of the end faces,
The feed node is coupled to the phasing ring by a reactive matching network that is centrally located and accommodates a pair of connections to the phasing ring that are generally opposed in diameter;
The antenna as described in any one of Claims 1-4. The connecting portion includes a plurality of sector conductors, each sector conductor having an outer portion connected to the phasing ring along an arc that forms an angle of at least 45 degrees with respect to the axis of the cylindrical body;
The antenna according to claim 7. The radiating element has a first end coupled to the phasing ring and a second end spaced from the phasing ring;
The antenna as described in any one of Claims 1-8. At least some of the second ends are open circuits;
The antenna according to claim 9. Having a second conductive ring on the substrate;
The second ring links together at least some of the second ends of the radiating elements;
The antenna according to claim 9. The radiating element includes a plurality of spiral radiating elements on the cylindrical side portion each having a first end coupled to the phasing ring and a second end spaced from the phasing ring;
The antenna further includes a second conductive ring on or adjacent to the other end of the cylindrical body;
The second conductive ring resonates at a second operating frequency of the antenna;
A first radiating element having a second end of an open circuit spaced from the second ring, and a closed circuit connected to the second ring by a second end; A second radiating element of
The antenna according to claim 7 or 8. m and n are non-zero positive integers,
Let λ _g1 and λ _{g2 be the guide} wavelengths of the first and second operating frequencies of the antenna, respectively,
The electrical length of the first radiating element is (2m−1) λ _g1 / 4,
The electrical length of the second radiating element is nλ _g2 / 2.
The antenna according to claim 12. A feeder structure including a transmission line section passing through the core from the proximal end face to the distal end face;
The feed node forms the distal end of the transmission line section;
The reactive matching network includes a bipolar network on the distal end face;
The antenna according to claim 12 or 13. A dielectric-loaded multifilar antenna for circularly polarized radiation having an operating frequency exceeding 200 MHz, wherein the antenna is
An electrically insulating core of solid material having a dielectric constant greater than 5 and occupying a majority of the internal volume defined by the outer surface of the core;
Multiple power supply nodes;
An antenna element structure on or adjacent to the outer surface of the core and including a plurality of elongated conductive antenna elements;
A ring coupled at the operating frequency coupled between the elongated antenna element and the feed node;
Including
The elongated antenna element extends from the resonant ring in a direction away from the feed node;
Dielectric loaded multifilar antenna. The elongated conductive antenna element has an open circuit end;
The antenna according to claim 15. The core has a central axis;
The outer surface of the core has first and second opposite surface portions extending transversely to the axis, and a side portion between the laterally extending surface portions;
The feed node and the resonant ring are associated with the first laterally extending surface;
The elongated conductive antenna element extends from the ring on the side portion toward the second laterally extending surface portion;
The antenna according to claim 15 or 16. Having two feeding nodes connected to the ring at respective connection points located on opposite sides on the ring;
The antenna according to claim 17. Having two feeding nodes connected to the ring by respective inductive connection links;
The antenna further includes a shunt capacitance coupled across the two feed nodes;
The antenna according to any one of claims 15 to 18. The core is a cylinder;
The resonant ring includes an annular conductive path on the first laterally extending surface;
The elongate conductive antenna element is spiral and has the same extent in the axial direction;
The antenna according to claim 17. The core is a cylinder;
The resonant ring includes an annular conductive path on the side portion adjacent to the first laterally extending surface portion;
The elongate conductive antenna element is helical and has an axial extension;
The antenna according to claim 17. The resonant ring includes at least one series connected capacitance;
The antenna according to any one of claims 15 to 21. The elongated conductive antenna element is a quarter-wave or three-quarter wavelength element at the operating frequency;
The antenna according to any one of claims 16 to 21. A power supply node pair constituting a balanced power supply connection for the resonant ring;
The antenna according to any one of claims 15 to 18. A dielectric-loaded multifilar antenna for circularly polarized radiation having an operating frequency exceeding 200 MHz, wherein the antenna is
An electrically insulating core of solid material having a dielectric constant greater than 5 and occupying a majority of the internal volume defined by the outer surface of the core;
A pair of power supply nodes,
An antenna element structure that is on or adjacent to the outer surface of the core and connected to the feed node and coupled to the phasing ring at each spaced point on the ring An antenna element structure including at least four elongated conductive elements,
A dielectric-loaded multifilar antenna. The electrical length in each of the at least four elongated conductive elements is an odd integer (1, 3, 5, ...) times a quarter wavelength at the operating frequency.
The antenna according to claim 25.   27. An antenna assembly comprising the antenna of any one of claims 24-26 and a balun coupled to the feed node.   20. An antenna assembly comprising the antenna of claim 18 or 19, and a differential amplifier having a differential input coupled to the feed node.

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