Antenna assembly

[0002] This invention relates to an antenna assembly suitable for a communication device such as a mobile transceiver, a mobile telephone, a device for providing radio communication to and from a personal computer, a wireless base station and so on. More particularly the invention relates to an antenna which is particularly adapted for insertion in a printed circuit board which carries at least some of the components for the communication device.

[0003] A known form of antenna which may be employed in communication devices of the foregoing character is a planar suspended F antenna, which comprises a radiating element, typically a planar sheet, mounted above and extending partly over a ground plane, the radiating element being connected to the ground plane along one edge. A conductive antenna feed couples signals to or from the antenna and the operating circuits of the communication device the antenna feed is normally connected to the radiating element at a position substantially separated from the grounded edge thereof, typically at a location part of the way along the radiating element and at one edge thereof. The radiating element requires a continuous ground plane underneath it and according there should be no components of the aforesaid operating circuits located close to the radiating element.

[0004] It is desirable for the minimization of cost in product manufacturing to employ single sided printed circuit boards. Since a planar suspended F-type antenna requires significant space around it to be free from components, and having regard to the desirability of economising as far as possible in the occupancy of the area available on a printed circuit board, it is known to form the antenna with extending legs which are placed on the non-component side of the printed circuit board. Such a structure is difficult to place automatically and commonly it has to be placed and soldered in circuit by hand.

[0005] The invention particularly concerns an antenna assembly comprising a printed circuit board having on one face various components and on the other face a ground plane, said printed circuit board including an aperture and an antenna structure comprising a conductive ground plane element having peripheral parts overlapping the edge of the aperture, a connecting element extending from the ground plane member through the said aperture, a radiator element integral with the connecting element and extending generally parallel and within the area of the ground plane element, and an antenna feed element which extends from the radiating element though said aperture to said one face of the printed circuit board.

[0006] The antenna structure may be readily made from a single sheet of appropriate conductive material. It may be formed into the required shape by cutting and bending and may readily be inserted with the aid of an automatic insertion tool, through the aperture in the printed circuit board from the component side thereof until the peripheral parts engage the component bearing face of the printed circuit board. Automatic soldering is easy to perform on the component side of the printed circuit board both to secure the ground plane element in position and to provide the necessary conductive connection for the antenna feed.

[0007] A specific example of the invention will be described hereinafter with reference to the accompanying drawings.

[0008] FIG. 1 is a perspective view of an antenna assembly according to the invention.

[0009] FIG. 2 is a sectional view of the centre line of the antenna structure shown in FIG. 1.

[0010] In the assembly shown in the drawings, there is a generally planar printed circuit board 1 which has an ‘upper’ face 2 and a lower 3. The printed circuit board is a single sided board in which the various electrical components, either discrete components, individual integrated circuits and conductive paths and so on are disposed only on one face, in this example the upper face 2 of the printed circuit board. The lower face 3 of the board is covered with a conductive layer to constitute a ground plane for the printed circuit board.

[0011] For the accommodation of a planar suspended F antenna, the printed circuit board is provided with a rectangular aperture 4 through which an antenna structure 5 may be automatically inserted from the component side of the printed circuit board. The aperture 4 is a ‘though-plated’ aperture which connects the pads on the ‘upper’ face of the printed circuit board to the ground plane on the lower face so ensuring the integrity of the ground plane. The antenna structure 5 comprises an integral member having four principal parts. These parts include a ground plane 6 constituted by a generally flat element. Spaced from and generally (though not necessarily exactly) parallel to the ground plane 6 is a planar radiator element 7 which is preferably somewhat less than coextensive with the ground plane 6 and is preferably within the area defined by the ground plane 6.

[0012] The ground plane 6 is crenellate around its edges, so as to form a multiplicity of attachment lugs 8 which overlap the margin of the aperture 4 and are soldered to underlying pads 2a, 2betc on the upper surface of the board 1. Connecting the planar element 6 and the radiator element 7 is a connecting part 9 which preferably forms a join with the antenna element along a mutual margin of the element 6 and connecting part 9 and has a common edge with the ground plane member 6. The lug 8awhich extends from the common edge of part 9 and planar element 6 may be cut out from the aperture in the part 9.

[0013] Also integral with the antenna structure is an antenna feed 10 which extends from a location preferably adjacent a side edge of the radiator element to the plane of the ground plane element, having an end lug which is disposed inside a peripheral aperture or slot 11 in the ground plane element so that the feed does not connect with the ground plane except by way of the radiator element.

[0014] The structure may be inserted into the aperture from the component side of the board 1 so that the lugs 8 engage the pads on the upper surface of the printed circuit board and the connecting element 9 abuts one side of the aperture. The lugs 8 may be reflow soldered into position by an appropriate automatic soldering tool.