MXPA99002201A - Wideband slot-loop antennas for wireless communication systems - Google Patents

Abstract

A wideband slot-loop antenna is described which comprises a generally planar loop element having a generally rectangular outer perimeter and a slot defining an inner perimeter, the mid portion of the slot-loop structure providing a major radiation portion of the antenna;a loading structure extending from one end of the slot, the loading structure for top loading the radiation portion;and an impedance matching portion for coupling a feed to the major radiation portion. The antenna also includes distributed matching patches. The distributed matching patches realize extra wideband performance. The antennas in the present invention are suitable for various wireless communications, such as PCS, Cellular Telephone, wireless data and computer network

Description

WIDE-BAND BROADBAND ANTENNAS FOR WIRELESS COMMUNICATION SYSTEMS The present invention relates to broadband slot antennas and, more particularly, slotted frame antennas.

BACKGROUND OF THE INVENTION The antennas are used for various communication systems, such as television (TV), cellular telephone, local area network (LAN-local area network) and data, personal communication service (PCS-personal communication service), etc., which are the areas that are developing rapidly. A strong and clear signal and a wide coverage of the information that is sent and received is very critical for wireless communication systems. Therefore, good antennas are required. It has been proven that existing antennas in the market have several problems, such as narrow bandwidth, low gain, larger size and high cost. The narrow bandwidth limits in a particular way the range of applications. For example, if an antenna is designed for a personal communication network (PCN) frequency band, it may not cover the PCS band frequency. Low gain results in poor coverage in communication systems; requiring vice-versa, high sensitivity in reception, or high transmission power. Most users prefer a smaller sized antenna to create open space. Finally, the high cost is due to the complexity of antenna structures available today. Returning to the early years of the 90s, a slot-frame antenna, with reflector backing was proposed by M. Cai and M. Ito in an article "New Type of Printed Polygonal Loop Antenna; IEE Proceedings-H, Vol. 138, No. 5, Oct. 1991, pp. 389-396. " 'Antenna was designed based on the idea of combining a simple polygonal frame antenna and a rectangular slot antenna. Therefore, the antenna as proposed, has the advantages of polygonal frame and rectangular slot antennas, such as high directivity as well as high production tolerance. In addition, this antenna is described with a 24% impedance bandwidth. However, because the rectangular slot is used as a main portion of radiation, the radiation is not very efficient. This antenna is not suitable for narrower bandwidth applications (such as television) due to its limited bandwidth. In addition, this type of antenna is limited in the various radiation patterns it provides. In addition, the feedback presents problems in the manufacturing processes. In view of the various drawbacks associated with current antennas, it would be advantageous to provide an antenna, which alleviates some of these problems to provide a more reliable and efficient antenna design. Therefore, there is a need for an antenna with some of the following characteristics: high gain to improve the performance of existing communication systems such as sensitivity and effective radiation power; the increased bandwidth for multiple system applications and for wider frequency coverage; configurable for multiple radiation patterns to accommodate different environmental scenarios; a simplified format for easy manufacturing at high performance and at a low cost; and easy installation.

SUMMARY OF THE INVENTION In the present invention, novel structures of upper load antennas are applied to provide superior radiation efficiency and broad bandwidth potential. In conjunction with the upper load structure, the coupling circuits are investigated to give extra broadband performance. The invented antennas also provide unidirectional as well as bidirectional radiation patterns. To overcome the inefficiency of feeding an RF signal to an antenna, simple power structures are used to make the antenna easily manufactured, at an effective cost, and that is suitable for different types of applications. The antennas in accordance with one embodiment of the present invention preferably include single antenna structures with top loading shapes and distributed coupling circuits to provide wide bandwidth potential, high gain, smaller size and radiation pattern wanted.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features of the preferred embodiments of the invention will become more apparent in the following detailed description where reference is made to the accompanying drawings, wherein: Figure 1 is a top view of a configuration of flat antenna and associated coupling circuits, in accordance with one embodiment of the present invention; Figure 2 is a top view of an antenna configuration with a U-shaped slot, top loading and coupling circuits in accordance with a further embodiment of the present invention; Figure 3 is a graph showing the frequency response of the antenna shown in Figure 1; Figures 3 (a) and 3 (b) show respective radiation patterns to the E plane and to the H plane. Figure 4 bidirectional radiation patterns of the antenna shown in Figure 1; Figure 5 is a schematic diagram of an antenna having a metal foil reflector, in accordance with one embodiment of the invention; Figures 6 (a) and 6 (b) show respective unidirectional radiation patterns to the E plane and to the H plane of the antenna shown in Figure 5; Figure 7 is a schematic diagram of a power line structure of a two-element antenna array coplanar configuration, in accordance with one embodiment of the present invention; Figure 8 is a schematic diagram of a 4-element antenna array configuration having a power serial structure, in accordance with the present invention; Figure 9 is a schematic diagram of a 2-element antenna array configuration, having a side-feed structure, in accordance with one embodiment of the present invention; Figure 10 is a schematic diagram of a single-element antenna having a lower lateral microtira line feed structure, in accordance with one embodiment of the present invention; and Figure 11 is a schematic diagram of an 8-element antenna array configuration using the 4-element antenna array shown in Figure 8.

DETAILED DESCRIPTION OF A PREFERRED MODE With reference to Figure 1, a general geometry of a direct end antenna and its coupling circuits, in accordance with one embodiment of the present invention, is generally indicated by the number 1. In this diagram all the dimensions are indicated in millimeters. The antenna comprises a flat loop element, having an outer perimeter 1 (e) generally rectangular and a slot 1 (d) defining an inner perimeter, the middle portion 1 (b) of the slot-frame structure, which provides a greater portion of radiation from the antenna; a load structure 1 (a) having a double ring configuration extending from one end of the slot 1 (d), the load structure for the top load of the radiation portion; and an impedance coupling portion 1 (c) for coupling a supply 6 to the major radiation portion 1 (b). The antenna is preferably engraved on a flat dielectric member coated with copper, such as a printed circuit board (5) FR4. The FR4 material is only for the antenna support. The antenna can be coupled with a coaxial connector at the feed end of the antenna. The dual ring top load configuration (la) provides an inductive top load that shrinks the overall size of the antenna, provides broadband potential and improves radiation efficiency. The double rings have a diameter of about 3 mm to 15 mm, but are not limited to this size as shown in Figure 1. The middle part (Ib), which is the portion of highest radiation comprises a central slot structure with its longitudinal axis aligned along the longitudinal axis of the antenna so that an electromagnetic field develops between the groove and the normal E field towards the metal flange and separates the radiation portion in the arms of the loop or frame. The impedance transformation section 1 (c) is formed by a pair of inclined elements each coupling a feeder 6 (a) and 6 (b) to a respective arm of the frame element. The impedance transformation section also behaves like a portion of radiation. Note that the sections (the), (Ib) and (lc) are distinguished from each other by dashed lines as shown in Figure 1. The first and second provisional connection elements (2) and (4) are formed next to the respective outer edges of the transformation element of impedance. The provisional connection elements (2) and (4) are closely coupled to the impedance transformation portion (1c) and used as distributed coupling components. They provide wide bandwidth performance in conjunction with the top loading structure. The provisional connections (2) and (4) are formed on the same side of the printed board as the coupling components. Either the provisional connection (2) or the (4) can be, but are not limited to the shape and size shown in Figure 1, as long as a suitable coupling that is achieved by means of the coupling effect. A third provisional connection element (3) is used to provide a capacitive coupling between both portions of the part (lc), which cancels the inductive part of the impedance looking in the part (lc) towards the radiation portion over a range of broad frequency. Therefore, a wider bandwidth is still achieved. This provisional connection is considered as a distributed coupling component as well as, this may be, but is not limited to the other side of the printed circuit board. Also, this may be, but is not limited to the shape, size and position shown in Figure 1. In use, an RF signal from a transceiver or the like, is coupled to the respective power points thereby inducing a current in the antenna, alternatively a current induced in the antenna from a received signal, is supplied to the transceiver (6). Referring to Figure 2, an additional embodiment of a top loading structure is shown. The upper load structure in this embodiment comprises a narrow U-shaped slot, the arms of the U extend into the respective dipole sections 7 (b) and the base of the U extends transverse to the end of the slot in the section 7 (a). The narrow slot has a length of about half a wavelength at the center frequency of the antenna. The U-shaped slot provides an inductive top load for the antenna. In this way, the antenna size is reduced but its radiation efficiency is increased. In addition, the antenna with this top loading configuration has a broad bandwidth potential. The other parts are the same as those of Figure 1. The top loading structure can be a single ring as indicated by the number (25) in Figure 2 or a double ring configuration as indicated in Figure 1. Figure 3 shows the frequency response of the antenna configuration described with respect to Figure 1, with approximately 85% of the bandwidth covering 1.7 GHz at 4.3 GHz. Figure 4 (a) shows the radiation pattern of the bidirectional antenna as described in Figure 1 with a beam width of 70 ° in both the forward and backward direction. Figure 4 (b) shows the corresponding H plane radiation pattern. These patterns are very suitable for PCS systems, in street scenarios or in corridor applications. As shown in Figure 5, a direct feed end antenna in accordance with a further embodiment of the invention includes a terrestrial plane (20) separate from the radiation portion of the antenna described in Figure 1. The terrestrial plane makes that the antenna has a unidirectional radiation pattern as shown in Figures 6 (a) and 6 (b). It can be noted that the rigid dielectric shown in Figure 1 can be replaced by air for example, if the copper sections are sufficiently rigid. Figure 7 shows a balanced 2-element antenna array structure, which is comprised of two direct end antennas connected at their direct feed points to form a central feed antenna. The direct feed point of the array is powered by coplanar transmission lines comprising a pair of outside transmission lines (b) and an internal transmission line 9 (a), both extending from one edge of the substrate to the direct feed point. The inner conductor 9 (a) is connected to a common supply point (A) of the elements of "Radiation • (10) and (11) that are electrically connected in parallel to form a balanced array The outer conductors 9 (b) are connected to respective central power points (B) and (C) of the radiation elements (10) and (11) In this configuration, a terrestrial plane is also used to direct the radiation.The radiation portion can be any configuration but is not limited to those described in Figure 1 or Figure 2. Figure 8 shows a 4-element antenna arrangement having a balanced structure in accordance with one embodiment of the invention.In this configuration, the antenna is also powered by the end, however, the RF signal is applied along a line (12) coplanar to the radiators or radiating elements The radiators (13) and (14) are electrically connected in parallel to form a balanced sub-arrangement, then this sub-arrangement is cascaded with the coplanar transmission line (15) of approximately 0.65 wavelength. The other sub-arrangement consisting of radiators (16) and (17) is terminated at the other end of the coplanar line (15). The radiation elements (13), (14), (16) and (17) can have any configuration, but are not limited to those described in Figure 1 or Figure 2. Figure 9 shows an antenna array of 2 elements with a lateral feed configuration in accordance with another embodiment of the invention. The RF signal is fed along a microtire transmission line (18), with the ground of the microstrip line (18b) connected to the upper charge edge center (D). The microtira line is formed by part of the conductor (18a) and part of the radiation element (19). The transmission line is terminated at point (E) through a track. The radiation element (19) can be any slot-frame configuration, but is not limited to those described in Figure 1 and Figure 2. Figure 10 shows a single element antenna with a power supply configuration. bottom side, in accordance with a further embodiment of the invention. The power structure (21a) and (21b) act as a low coupling loss network to provide broad bandwidth performance. A provisional connection (22) differentiated from (21b) by a dashed line is used as a distributed coupling component. This provides a capacitive coupling and cancels the inductive part of the impedance that looks at the radiation portion. Note that this provisional connection is different from the provisional connection (3) as shown in Figure 1, since it is not an isolated provisional connection. The RF signal is fed through the coupling network (21) and through a path (23) to a radiation element (24), which can have any configuration, but is not limited to those described in Figure 1 and in Figure 2. Figure 11 shows an 8-element antenna arrangement with feedback configuration, in accordance with a further embodiment of the invention. In this, the arrangement of 4 elements of mode two is combined as described in figure 8. For convenience, arrangements should be made as upper and lower arrangements, with both arrangements formed on one of the surfaces of a member dielectric, which is referred to as the top layer. The arrays are connected by a microtire line that extends between the feed points of the two arrays. The upper and lower copper layer of the dielectric member constitutes the microtira line. To adequately feed the 4-element upper antenna array and the 4-element lower antenna array, transitions from coplanar transmission lines to microstrip lines are made by way of paths (27) and (32). The microtira lines are constituted by a narrow copper strip (33) that connects the two arrays in the upper layer and a wide copper strip (26) in the bottom layer (indicated by broken lines) of the dielectric FR-4 material of 60 mils. The narrow copper strip on the upper surface is comprised of three parts indicated by the numbers 28, 29 and 31. Each of these parts has a different width, each constituting a different impedance of microtira line. A small provisional connection 30 is arranged at approximately a little more than half a wavelength from the upper array, to which the power is applied. The first microtira (28) / (26) is a quarter-wavelength line of 70.7-Ohm that transforms the impedance of 50 -Ohm considering the top antenna arrangement of 4 elements at 100 Ohm. This impedance of 100 Ohm is further transformed into the same impedance (ie, 100 Ohm) by the intermediate microtira (29) / (26), which has half a wavelength in length and provides a phase shift of 180 degrees. These 100 Ohm are then derived with another impedance of 100 Ohm transformed by the lower microtira (31) / (26) from the impedance of 50 Ohm considering the lower antenna arrangement of 4 elements to provide about 50 Ohm in the center of the connection small provisional (30). The provisional connection (30) is also used to provide light impedance tuning. A short cable is used to feed and / or pick up an RF signal to and / or from the 8-element antenna arrangement, respectively, by connecting its center conductor to the provisional upper copper connection (30) via a hole and its outer conductor. cover, to the lower copper strip (26). Thus, it can be seen that this invention provides a significant improvement of the prior art for the following reasons. The upper double-laden structure (la), as shown in Figure 1, provides broad bandwidth potential, smaller size and highly efficient radiation capacity. The U-shaped top load structure of half wavelength, as shown in Figure 2, provides broad bandwidth potential, smaller size and highly efficient radiation capacity. The provisional coupling connections (2), (3) and (4) as shown in Figure 1 and Figure 2 are used to provide extra broadband performance. The simple and novel power supply structure (9), making use of a coplanar transmission line and radiation components electrically connected in parallel, as shown in Figure 7, is used to minimize the insertion loss of the RF signal Due to the feeding structure, it simplifies manufacturing, and provides flexibility in various applications. A series feed structure with coplanar transmission lines (12) and (15) as shown in Figure 8 is applied to the antenna array to achieve less RF signal insertion loss, simplifies manufacturing and provides flexibility in several Applications. A lateral feed structure (18), making use of a microtira line and the radiation component as shown in Figure 9, is employed to provide RF signal feeding flexibility to the radiation elements for the array applications. big antenna The provisional connection (22), as shown in Figure 10, in conjunction with a power structure (21) (which is also considered as the coupling network), provides broadband performance and reduced insertion loss. The lower lateral feed configuration makes the antenna easily manufactured and the RF signal is conveniently fed to the antenna from the bottom. The upper and lower microtira (28) / (26) and (31) / (2-6) "'as shown in Figure"' 11, are, respectively, quarter-wavelength impedance transformers for transforming impedances of 50 Ohm (considering the upper and lower antenna arrays of 4 elements) to 100 Ohm. The intermediate microtira (29) / (26) provides 180 degree phase slip.

The provisional connection (30) is used to provide light impedance tuning. A short cable is used to feed and / or pick up an RF signal to and / or from the 8-element antenna array, respectively connecting its center conductor to the upper provisional copper connection (30) via a hole, and its cover conductor external to the lower copper strip (26). Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claims appended thereto.

Claims (7)

1. CLAIMS; An antenna comprising: (a) a generally planar loop element having a generally rectangular outer perimeter and a slot defining an inner perimeter, the middle portion of the slot-frame structure providing a greater portion of radiation the antenna; (b) a loading structure extending from one end of the slot, the loading structure for the top loading of the radiation portion; and (c) an impedance coupling portion for coupling a supply to the largest portion of radiation.
2. 2. An antenna as defined in claim 1, the load structure is a double ring configuration.
3. 3. An antenna as defined in claim 1, the loading structure includes a single-ring configuration coupled to a narrow U-shaped slot.
4. 4. An antenna as defined in claim 3, the narrow slot is a half wavelength slot.
5. 5. An antenna as defined in claim 1, the impedance coupling element comprises first and second inclined sections for connecting the power to the respective end of the frame radiation section.
6. 6. An antenna as defined in claim 5, which includes a provisional connection coupling element distributed to provide capacitive coupling between the first and second inclined sections, whereby the capacitive coupling cancels the inductive part of the impedance which considers the coupling element. 7. An antenna as defined in claim 6, the provisional connection coupling elements are located adjacent in relation to the outer edges of the inclined sections. 8. An antenna as defined in claim 1, which includes a first and a second of the connected frame elements to form a first array of 2-element, balanced central-feed antenna, and includes a feeder structure having lines of coplanar transmission extending from the feed points of the frame to an edge of the antenna, whereby the feed structure minimizes the insertion loss of an RF signal applied to it. 9. An antenna as defined in claim 1, including first and second pairs of frame elements, the respective frame pairs are electrically connected in parallel to form the first and second balanced sub-arrays; a coplanar transmission line of approximately 0.65 wavelength connecting the first and second arrays; and a feeding structure for coupling an end feed to the arrangements. 10. An antenna as defined in any of claims 1, 2, 3, 8 and 9, including a microstrip feeding structure. 11. An antenna as defined in claim 10, the power structure comprises a terrestrial plane (18a) of the upper microtire transmission line that is connected to a central point of the upper load structure, and a transmission line lower microtira terminated at a central feed point of the radiation element through a track. 12. An antenna as defined in claim 1, which includes a lower side-feed structure to provide broadband performance, lateral feed includes a terrestrial plane and a multiple impedance section. An antenna as defined in claim 12, which includes a small provisional connection connected to the terrestrial plane to provide a capacitive coupling to cancel the inductive part of the impedance that the radiation portion considers. 14. An antenna as defined in claim 1, including first and second balanced sub-arrangements of 4 elements; and a power structure for coupling a central power to the arrays, the power supply comprises a half wavelength delay line for coupling a 50 Ohm source impedance of a power cable with the two antenna arrays of 4 elements and which has the upper and lower microtiter impedance of 70.
7. 7 Ohm of a quarter wavelength that couples the elements coupled from the delay line to the respective arrangements, so that the power structure provides a transition from a coplanar to the microtira line through tracks.