WO2001041257A1

WO2001041257A1 - Antenna device with transceiver circuitry

Info

Publication number: WO2001041257A1
Application number: PCT/SE2000/002392
Authority: WO
Inventors: Björn LINDMARK; Per-Anders Arvidsson
Original assignee: Allgon Ab
Priority date: 1999-12-01
Filing date: 2000-11-30
Publication date: 2001-06-07
Also published as: CN1336024A; AU1911401A; EP1247311A1; WO2001041256A1; AU1425501A

Abstract

An antenna device for use in a wireless telecommunication system, comprising a housing (2) including transceiver circuitry and a generally planar printed circuit board, PCB (3). The housing includes a conductive portion (4) with an open cavity (5) adjacent to a radiating element (9). The cavity walls (5) shield the radiating element (9) from the transceiver circuitry (15).

Description

ANTENNA DEVICE WITH TRANSCEIVER CIRCUITRY

Field and Background of the Invention

The present invention relates to an antenna device for use m a telecommunication system, m particular m a mobile telephone system. The antenna device comprises: a housing a generally planar printed circuit board, PCB, arranged m said housing and having a front side and a rear side, a ground plane layer on said front side of said PCB - said ground plane layer being provided with a radiating element located m a radiating portion of said PCB a feed network located m opposite relation to said radiating element for feeding electromagnetic power to said radiating element, and a shielding box located adjacent to said radiating portion for preventing radiation backwards from said rear side.

Related Art

In such an antenna device, it is considered particularly useful to provide a slot-coupled planar antenna element as first described m "Microstπp Antenna Aperture-Coupled to a Microstπp Line" by David M. Pozar, Electronic Letters, 17 January 1985, Vol. 21, No. 2, and later by the same author m "A Reciprocity Method of Analysis for Printed Slot and Slot- Coupled Microstrip Antennas", IEEE Transactions on antennas and propagation, Vol. AP-34, No. 12, December 1986.

Dual polarized antennas of this type are disclosed m "Construction of a slot-coupled planar antenna for dual polarization" by M. Yamazaki, E.T. Rahardio, ad M. Haneishi, Electronic Letters, 27 October 1994, Vol 30, No. 22. A planar antenna structure is disclosed m the published PCT Application No. PCT/SE97/00776 by the applicant. The latter document is incorporated herein by reference.

This planar antenna technology consists generally of a conductive ground plate with an aperture. A microstrip feed line is provided across the aperture. Further, a radiating patch is located parallel to the plate above and spaced from the aperture. Furthermore, an open shielding box is provided on the opposite side of the plate to direct the antenna radiation generally towards the patch.

SE-C2-504 950 and SE-C2-504 951 disclose some ideas relating to cooling of circuitry integrated in an antenna device, wherein air flow is provided in a cavity and dimensions of cooling flanges are selected to improve antenna function, respectively.

When providing an antenna device for a small -size base station, it is desired to integrate the base station in the antenna unit or locate the antenna in the base station, all in order to obtain one compact unit. The radiating element may then be connected to the RF and digital circuitry without any cumbersome connector and cable arrangements. When integrating the radiating element and the transceiver circuitry of the base station one would arrive at some compromise between the general electromechanical design of the two. The transceiver circuitry dissipates heat and generally needs EMI protection/shielding from the environment. The general technique to accommodate the electrical components of the circuitry is to provide a printed circuit board (PCB) having printed circuits in two (one would be possible) or more layers to which the components are soldered. The components are generally placed on both sides of the PCB, in either surface mount or via mount. The PCB is normally enclosed in a conductive (metal or metallized) box of housing to provide shielding. The box or housing may also be equipped with cooling flanges to increase heat transfer from the enclosed circuitry.

An antenna device, as referenced above, is quite suitable to provide at least partly in PCB technology. Naturally, the radiating element will handle RF energy that could influence the function of the base station circuitry if not appropriately shielded. However, an antenna element provided directly on the PCB could not radiate because of the shielding. On the other hand, placing the radiating element outside the circuitry shielding would require at least one additional PCB resulting in extra part and assembly costs. Therefore, the invention is concerned with providing transceiver circuitry and at least part of the radiating element in the same housing, preferably on the same PCB, while maintaining proper isolation between the two.

As will be evident from this disclosure, there is a number of other antenna designs that would also work well in PCB technology.

Summary of the Invention

Consequently, a main object of the invention is to provide a compact antenna device and to integrate the transceiver circuitry and a radiating element within the same housing, preferably on one PCB. Another object is to provide isolation between the transceiver circuitry and the radiating element . Yet another object is to provide efficient assembly and large- scale production of the antenna device. These and further objects are attained and the above- indicated problems are solved by antenna devices according to the appended claims.

A particular advantage of the inventive antenna device is that the printed circuit board (PCB) can be used for all signal transfer in the device, thus making it suited for automatic assembly and cost-efficient large-scale production. Further, the inventive device allows a very compact structure that will be light-weight and easy to handle in installation.

Other advantageous developments of the invention are set forth in the dependent claims and the detailed description below.

Brief Description of the Drawings

Fig. 1 shows an embodiment of the antenna device according to the invention including a housing accommodating both transceiver circuitry (not shown) and a radiating element, the latter being electrically isolated and provided in an open cavity on the front side of the casing;

Fig. 2a shows a cross section of an embodiment similar to that of fig. 1 with a shielding box soldered to the PCB;

Fig. 2b shows a cross section of a modified embodiment similar to that of fig. 2a, provided with two radiating patches;

Fig. 3 shows a cross section of another embodiment with a different shielding box;

Fig. 4 shows a cross section of still another embodiment with a shielding box formed by printed circuits of the PCB; and

Figs. 5a-d show a number of radiating elements of various kinds different from those of the figs. 1-4. Description of Preferred Embodiments of the Invention

With reference to fig. 1, there is disclosed an antenna device with a radiating element integrated with a small-size base station in a mobile phone telecommunication system and which could be part of a GSM network. The integrated antenna device 1 has a partially conductive housing including a non- conductive cover 2 and a metal casing 4 provided with fasteners (not shown) on its back adapted for installing the device 1 on a wall or on a pole. The purpose of using a small - size base station may be to widen the coverage of the system by increasing the signal strength in an area where signals are weak from another adjacent, larger base station. At least equally importantly, it may be desirable to provide a small - size base station to increase the number of calls that the system can handle in an area. The base station generally has a feeding interface. Such an interface will generally include cables and connectors for power supply to active components in the base station as well as signal transfer of voice and data signals. It could include radiative means for signal transfer and solar panels for power supply.

The housing 2,4 accommodates the base station circuitry. This circuitry (however not shown in fig. 1) is mounted on a printed circuit board, PCT, 3 which has a conductive pattern in a layer on one or two sides 3', 3" and, typically, inside for interconnecting the different circuitry components. The conductive pattern may of course in itself form components, especially of radio frequency. The same PCB also includes a radiating element, which in this preferred embodiment is an aperture-fed patch antenna. The integration of the radiang element and the transceiver circuitry on the same PCB is combined with an electrical separation of the two, so that the antenna element will not disturb the operation of the circuitry. The separation is obtained by a conductive open cavity 5 being formed by a recess m the metal casing 4 on the front side 3' of the PCB, adjoining a shielding box 6 on the rear side 3" of the PCB so as to enclose a radiating antenna pattern on the PCB. The coupling between the conductive walls of the cavity 5 on the front side 3' of the PCB and the shielding box 6 on the rear side 3" must be such that energy input to the antenna does not escape sideways to cause malfunction of the transceiver circuitry. The connection may be conductive or capacitive.

The non-conductive protective cover 2 permits transfer of radiation energy to and from the antenna element. The conductive metal casing 4 is connected to signal ground, including the walls of the conductive cavity 5 and the shielding box 6 on the rear side of the PCB 3.

In this embodiment, the radiating element consists of an aperture m the form of a slot 9 m a ground layer 8 on the front side of the PCB. Electromagnetic energy is fed from microstrip feed line 10 across it on the rear side of the PCB. The side and bottom walls of the cavity 5 directs the emitted radiation towards a patch 11 located m the upper or front portion of the cavity 5 m opposite relation to the slot 9. The patch is supported by the conductive housing by means of non-conductive pillars (not shown) . The microstrip feed line 10 is connected to the RF circuitry of the transceiver and therefore penetrates the side walls of the shielding box 6. Cooling flanges 12 are provided on the upper or front wall 4a of the metal casing 4 to improve convection or heat transfer from the transceiver circuitry to the ambient air.

Like parts are assigned the same reference numerals m figs. 1-4. With reference to fig. 2, there is provided an arrangement similar to that of fig. 1, however showing more details. The antenna consists of the ground layer 8, the slot 9, the feed line 10, the patch 11, and the shielding box 13, made of a metal sheet material bent into the shape of an open box and provided with a plurality of pins 14 making electrical and mechanical contact with the PCB ground layer 8. Simplified circuitry components are indicated by the numeral 15. These components 15 are arranged inside the metal casing 4 in a region of the PCB 3 located outside the cavity 5 and the antenna. Accordingly, the antenna elements 9,11 are shielded from the transceiver circuitry and will not be disturbed by the latter.

In the modified embodiment shown in fig. 2b, the antenna device includes a first patch 11 and a second, somewhat smaller patch 16. The patches 11, 16 have greater length (between the opposite side edges 11', 11" and 16', 16", respectively) than the diameter of the bottom wall of the cavity 5. This diameter is defined by the bottom edges 17, 18 of the cavity walls 5.

In this way, thanks to the outwardly inclined or flared cavity walls 5, the transceiver circuitry 15 in the conductive casing 4 has an enlarged space compared to a cavity with parallel sides, and the antenna function is enhanced by the greater size possible of the patches 11, 16 being spaced from the PCB. The antenna is formed by the ground layer 8, the slot aperture 9, preferably including two crossing slots, the feed line 10, preferably a dual polarized feed arrangement, the patches 11 and 16, and the shielding box 13.

One reason for using two patches instead of one could be to adjust the radiation pattern of the antenna. Another reason could be to increase the antenna bandwidth. Fig. 3 illustrates a modified embodiment, where the shielding box consists of separate walls 16 and a conductive plate 17, possibly making up a portion of the metal casing 4. The entire assembly is held together by screws 18', which provide a conductive connection between the shielding box 16, 17 and the conductive cavity 5.

With reference to fig. 4 there is provided yet another arrangement. Here, the shielding box consists of walls in form of conductive via holes 20 connecting a conductive rear side layer 19 with the ground layer 8. In this embodiment, the PCB 3a is somewhat thicker than in figs. 2 and 3, and a feed element in the form of a strip line 10 is embedded centrally in the PCB.

Fig. 5a shows an alternative radiating element. The depicted part of the PCB 3 is roughly the one that would be visible from above in the housing cavity 5 of fig 1. The radiating element is a resonant slot 21 excited by a microstrip line 22 on the rear side of the PCB.

Fig. 5b shows another alternative antenna, with two slot- coupled patches 23, 24, operating in two different frequency bands or in a single, relatively wide band.

Fig. 5c shows another alternative antenna, where the radiating element is a printed dipole with L-shape conductors 25, 26 on both sides of the PCB 3.

Fig. 5d, finally, shows another alternative antenna, where the radiating element is a printed spiral 27 with a feed line 28 on the rear side connected by a via hole 29 to the middle of the spiral 27. The term transceiver should be understood generally in this disclosure as a device that receives and/or transmits signals. In the present invention the reception and/or transmission is effected by at least one antenna element .

The inventive concept can be applied to different devices. For instance, the device could be a repeater or a booster device in a mobile telephone system, or a so-called tower top amplifier integrated with an antenna device.

Claims

1. An antenna device for use m a wireless telecommunication system, comprising: a housing (2,4) - a generally planar printed circuit board, PCB (3) , arranged m said housing and having a front side (3') and a rear side (3") , a ground plane layer (8) on said front side of said PCT said ground plane layer (8) being provided w th a radiating element (9) located m a radiating portion of said PCB a feed network (10) located m opposite relation to said radiating element (9) for feeding electromagnetic power to said radiating element, and a shielding box (6) located adjacent to said radiating portion for preventing radiation backwards form said rear side, characterised m that said shielding box (6) is electrically coupled to a conducting portion (4) of said housing (2,4) - said conducting portion (4) of the housing forms, at the front side of said PCB, an open cavity (5) located adjacent to said radiating portion to permit forward radiation to and from said radiating element (9) , said open cavity is defined by a bottom wall formed by said ground plane layer (8) of said PCB and inner side walls (5) of said conducting portion (4) extending generally m a forward direction from said PCB, and said housing (2,4) also accommodates transceiver circuitry

(15) for said telecommunication system, said transceiver circuitry (15) being shielded from said radiating element

(9) by means of said inner side walls (5) .

2. The antenna device defined m claim 1, wherein said transceiver circuitry (15) is arranged on said PCB (3) outside said radiating portion, said transceiver circuitry being isolated form said radiating element (9) .

3. The antenna device defined m claim 2, wherein said transceiver circuitry (15) is located on said front side of said PCB.

4. The antenna device defined m claim 3, wherein said inner side walls (5) extend obliquely away from said radiating portion so as to define a flared open cavity.

5. The antenna device defined m any one of claims 1-4, wherein said conducting portion (4,5) and said shielding box (6) are conductlvely mtercoupled through said PCB (3) .

6. The antenna device defined m any on of claims 1-4, wherein - said shielding box (6) are capacitively mtercoupled through

7. The antenna device defined m any preceding claim, wherein said open cavity (5) has a general shape selected from a group consisting of: square, rectangular, circular, X- shaped, bow-tie-shaped.

8. The antenna device defined m any preceding claim, wherein said shielding box (19,20) is formed as an integrated part of said PCB (3a) with a plurality of via holes (20) forming side walls of said box.

9. The antenna device defined m any preceding claim, wherein said radiating element is an aperture (9) coupled to at least one radiative patch (11; 11, 16) located at and spaced from said front side of said PCB.

10. The device defined m claim 9, wherein said aperture comprises two orthogonal slots arranged to provide dual polarization.

11. The antenna device defined m any one of the claims 1-8, wherein said radiating element is a resonant slot (21) exited by a microstrip line (22) .

12. The antenna device defined m any one of the claims 1-8, wherein said radiating element is a printed dipole (25,26) .

13. The antenna device defined m any one of the claims 1-8, wherein said radiating element is a printed spiral element (27) .

14. The antenna device defined m any of preceding claim, comprising an array of at least two radiating elements.

15. The antenna device defined m any preceding claim, wherein - said conductive portion of said housing comprises a metal casing (4 ) .

16. The antenna device defined m any preceding claim, wherein said conductive portion (4) includes, at least on said front side of said PCB, an enhanced convection portion (12) to cool said transceiver circuitry (15) .

17. The antenna device defined m claim 16, wherein said enhanced convection portion includes a cooling flange (12) .