Conformal antenna for wireless local area network transceivers

Abstract: In a transceiver for a WLAN having a two-part folding housing of electrically insulating material, one part having a shielded compartment for the radio circuitry, there is provided a two-part strip-conductor antenna conforming with the outer surface of the one part of the housing, the radio compartment shielding forming a ground plane for this antenna.

Description: The present invention relates to conformal antennae for wireless local area network (WLAN) transceivers. In particular but not exclusively the invention relates to antennae for transceivers adapted to plug in in place of Personal Computer Memory Card International Association (PCMCIA) memory expansion cards. Such transceivers generally comprise a computer interface, a WLAN controller and transmitter and receiver circuits operating at carrier frequencies of the order of 2.4 GHz, and can provide 1 Mbit/sec data links for personal computers or notebook computers over short ranges of the order of, say, one hundred feet. EP-A-0624002 discloses a LAN transceiver designed to plug into a PCMCIA slot of a network computer. EP-A-0619620 discloses a heating or warm water cost measuring device including an antenna. According to the present invention in a transceiver for a wireless local area network, the transceiver comprising a housing of electrically insulating material having inner surfaces defining a compartment for transmitter and receiver circuits of said transceiver and an outer surface, and an electrically screening coating on at least some of said inner surfaces defining said compartment, there is provided an antenna comprising at least one strip conductor on said outer surface of said housing, said strip conductor being electrically insulated from said screening coating. Preferably there are provided two said strip conductors extending in opposite directions around an edge of said housing and conforming to said outer surface, from a pair of spaced feed conductors that extend from the outer surface of said housing to one of said inner surfaces defining said compartment. The housing may be of two-part hinged form, a first part defining said compartment and a second part being of the form of a PCMCIA memory expansion card. A transceiver having an antenna in accordance with the present invention will now be described with reference to the accompanying drawing, of which:- Figure 1 shows diagrammatically parts of the transceiver, and Figure 2 shows diagrammatically a transceiver in conjunction with a lap-top computer. Referring to the drawings, the transceiver includes a housing comprising two parts 1 and 2 connected by a hinge 3, the first part 1 being in the form and size of a PCMCIA memory expansion card, say some 54mm wide, 86mm long and 5mm thick, with a plug connector 4 at its free end for connection to a socket connector provided on a lap-top computer 5 (Figure 2). The part 1 may carry for example computer interface circuitry (not shown) and a local area network controller (not shown), while the part 2 may be shaped so as to provide a compartment 6 for radio transmitter and receiver circuits (not shown), and to partially enclose the first part 1 in a closed or folded position. The inner surfaces 7 of the part 2 which define the compartment 6 are provided with a coating of electrically conducting material which electrically shields or screens the transmitter and receiver circuitry in the compartment 6. Around part of the outer edge of the part 2 there is provided an antenna comprising two conductive strips 8, preferably copper strips, formed or fixed on the outer surface of the part 2 and electrically insulated either by the material of the housing, by an underlying dielectric layer (not shown), or by an air gap (not shown) from the screening coating on the inner surfaces 7. These strips 8, which extend in L-shape around the outer comers of the part 2, are electrically connected to circuitry (not shown) within the compartment 6 by conductors 9 electrically connected to adjacent ends of the strips 8. The conductive coating on the inner surfaces 7 of the part 2 acts as a ground plane for the antenna strips 8. The length of the strips 8 is chosen so that the impedance of the antenna at the operating frequency, measured at the conductors 9, is inductive, so that the antenna may be matched to the radio transmitter and/or receiver circuitry by means of a capacitor (not shown) connected between a or each conductor 9 and ground. The transmitter and receiver circuitry may be connected to the circuits on the part 1 by way of a flexible cable (not shown) across the hinge joint 3.

Claims: A transceiver for a wireless local area network, comprising a housing (1, 2) of electrically insulating material having inner surfaces (7), defining a compartment (6) for transmitter and receiver circuits of said transceiver and an outer surface, and an electrically screening coating on at least some of said inner surfaces (7) defining said compartment, wherein there is provided an antenna comprising at least one strip conductor (8) on said outer surface of said housing (1, 2), said strip conductor being electrically insulated from said screening coating. A transceiver in accordance with Claim 1 wherein there are provided two said strip conductors (8) extending in opposite directions from a pair of spaced feed conductors (9) around an edge of said housing (1, 2) and conforming to said outer surface. A transceiver in accordance with Claim 2 wherein said feed conductors (9) extend from the outer surface of the housing (1, 2) into said compartment (6). A transceiver in accordance with any preceding claim wherein the housing (1, 2) is of two-part hinged form, a first part (2) defining said compartment and a second part (1) being of the form of a PCMCIA memory expansion card.

Inventors: WILLIAMS DAVID A, WILLIAMS, DAVID A.
Applicants: ZARLINK SEMICONDUCTOR LTD, ZARLINK SEMICONDUCTOR LIMITED
Application year: 1995
Main classification: H04B1
IPC codes: H04B1, H01Q1, H01Q9, H01Q5