Radio frequency local area network adapter card structure and method of manufacture

• US 5,815,120 A
• Filed: 02/28/1996
• Issued: 09/29/1998
• Est. Priority Date: 02/28/1996
• Status: Expired due to Fees

• Current Assignee: Lenovo Singapore Pte Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Lawrence, Mark John, Nunnery, William B.
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): PHAN, THO GIA
• Application Number:
  US08/608,229
• Time in Patent Office: 944 Days
• Field of Search: 343/752, 343/702, 343/872, 343/846, 343/895, 343/833, 343/873
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/2275 associated to expansion card or bus, e.g. in PCMCIA, PC cards, Wireless USB
• CPC Class Codes: H01Q 1/42 Housings not intimately mechanically associated with radiating elements, e.g. radome
• CPC Class Codes: H01Q 1/526 Electromagnetic shields
• CPC Class Codes: H01Q 9/36 with top loading
• CPC Class Codes: H01Q 9/38 with counterpoise with counterpoise comprising elongated elements coplanar with the active element H01Q9/44

Abstract

A radio frequency (RF) local area network (LAN) adapter card for a personal computer conforms to the Personal Computer Memory Card International Association (PCMCIA) standard 2.0 (extended), providing a credit-card sized RF LAN communications terminal that plugs into the side of a personal computer, a laptop computer, a palmtop computer, and the like. The RF LAN adapter card includes a minimum height, broadband integrated antenna that provides a vertically polarized RF signal with good horizontal range. The combination of the antenna and its surrounding radome provide a high gain, omnidirectional radiation pattern that overcomes the parasitic distortions imposed by the close proximity of the personal computer housing. The adapter card housing includes internal RF shielding structures that shield the antenna from noise radiated by radio frequency signal circuits within the housing. A conductive adhesive coating is provided on the conductive layer of the ground plane of the antenna, for mechanically and electrically connecting the ground plane to the adapter card housing. This enables the antenna to be assembled to the housing at a later time after testing of the internal circuits in the adapter card.

Claims

1. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a surface lying in a geometric plane with a conductive layer thereon forming a ground plane;

a subsystem housing having a support for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer housing;

an antenna mounted on said substrate and electrically insulated from said ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said ground plane;

said personal computer housing imposing a disturbance to a radiated field from said antenna;

a radome mounted on said subsystem housing and surrounding said antenna, having an enhanced directivity oriented toward said personal computer housing, to compensate for said disturbance to said radiated field;

wherein said radome further comprises;

a substantially hemispherical shell having an open side mounted on said subsystem housing surrounding said antenna, with an edge forming a plane substantially parallel to said geometric plane, with one face of said shell proximate to said personal computer housing having a substantially planar surface substantially perpendicular to said geometric plane;

wherein said radome further comprises;

said one face of said shell proximate to said personal computer housing further including a cylindrical surface projecting therefrom having a cylindrical axis substantially perpendicular to said geometric plane;

wherein said antenna further comprises;

a top hat antenna having a mast portion oriented substantially perpendicularly to said geometric plane with one end thereof mounted on said substrate at a base point and electrically connected to a radio frequency signal source and the opposite end of said mast terminated at a conductive plate oriented substantially parallel to said geometric plane;

wherein said antenna further comprises;

said circular conductive plate having a radius of a first magnitude and said mast having a length of a second magnitude, the sum of said first and second magnitudes being substantially equal to a quarter wave length of electromagnetic radiation having a central resonant frequency value radiated by said antenna in response to said radio frequency signal source;

wherein said antenna further comprises;

a first transmission line mounted on said substrate and coupling said base point to said radio frequency signal source, forming a quarter wavelength matching transformer;

a second transmission line mounted on said substrate and connected to said base point, forming an impedance match at frequencies lower than said central frequency; and

a third transmission line mounted on said substrate and connected to said base point, forming an impedance match at frequencies higher than the central frequency.

2. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a surface lying in a geometric plane with a conductive layer thereon forming a ground plane;

a subsystem housing having a support for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer housing;

an antenna mounted on said substrate and electrically insulated from said ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said ground plane;

said personal computer housing imposing a disturbance to a radiated field from said antenna;

a radome mounted on said subsystem housing and surrounding said antenna, having an enhanced directivity oriented toward said personal computer housing, to compensate for said disturbance to said radiated field;

wherein said subsystem housing further comprises;

a circuit card having a first edge mounted to said mechanical connector assembly, said card having logic circuits and radio frequency signal circuits mounted on a first surface thereof;

said logic circuits coupled to electrical terminals in said mechanical connector assembly for exchanging first digital signals with said personal computer, said logic circuits outputting second signals to said radio frequency signal circuits in response to said first signals;

said radio frequency signal circuits coupled to said antenna and outputting radio frequency signals as said radio frequency signal source to said antenna in response to said second signals; and

a conductive grounding electrode mounted along the periphery of said first surface of said card, connected to a system grounding potential, for shielding said antenna from said radio frequency signal circuits.

3. The radio frequency communications input/output subsystem for a personal computer of claim 2, wherein said subsystem housing further comprises:

a frame having a recessed portion on a first side thereof for mating with said periphery of said card, including a plurality of electrically conductive springs for resiliently contacting said conductive grounding electrode to make electrical contact therewith for shielding said antenna from said radio frequency signal circuits, said springs extending to a second side of said frame opposite to said first side thereof;

a top conductive cover having an edge portion on a first side thereof for mating with said springs on said second side of said frame, said springs resiliently contacting said top conductive cover to make electrical contact therewith for shielding said antenna from said radio frequency signal circuits and forming a reflecting ground plane for said antenna;

a planar platform surface on a second side of said top conductive cover opposite to said first side, for mechanically supporting and electrically contacting said conductive layer of said ground plane of said antenna, said platform including an aperture therein; and

a first shielded coaxial connector mounted on said first surface of said circuit card at a second end opposite from said mechanical connector assembly, said first coaxial connector juxtaposed with said aperture in said planar platform;

whereby said circuit card can be tested by connecting a test probe to said first shielded coaxial connector through said aperture prior to assembling said antenna to said subsystem housing.

4. The radio frequency communications input/output subsystem for a personal computer of claim 3, wherein said subsystem housing further comprises:

a second shielded coaxial connector mounted on said conductive layer of said ground plane of said antenna, for mating engagement with said first coaxial connector through said aperture, a center electrode of said second connector coupled to said antenna.

5. The radio frequency communications input/output subsystem for a personal computer of claim 4, wherein said subsystem housing further comprises:

a bottom conductive cover having an edge portion for mating engagement with an edge of said top conductive cover and having a recessed central portion;

a resilient pad positioned between said recessed central portion of said bottom cover and a second surface of said circuit card opposite to said first surface thereof, for resiliently forcing said plurality of electrically conductive springs into contact with said conductive grounding electrode of said circuit card to make electrical contact therewith, and forcing said springs into contact with said top conductive cover to make electrical contact therewith.

6. The radio frequency communications input/output subsystem for a personal computer of claim 4, wherein said subsystem housing further comprises:

a conductive adhesive coating on said conductive layer of said ground plane of said antenna, for mechanically and electrically connecting said ground plane to said planar platform surface of said top conductive cover;

whereby said antenna can be assembled to said subsystem housing at a time following testing of said circuit card through said aperture and said top conductive cover forms a reflecting ground plane for said antenna.

7. The radio frequency communications input/output subsystem for a personal computer of claim 6, wherein said subsystem housing further comprises:

said radome mounted on said top conductive cover over said planar platform surface.

8. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a surface lying in a geometric plane with a conductive layer thereon forming a ground plane;

a subsystem housing having a support for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer housing;

an antenna mounted on said substrate and electrically insulated from said ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said ground plane;

said personal computer housing imposing a disturbance to a radiated field from said antenna;

said antenna having an enhanced directivity oriented toward said personal computer housing, to compensate for said disturbance to said radiated field;

wherein said antenna further comprises;

a driven element having a mast portion oriented substantially perpendicularly to said geometric plane with one end thereof mounted on said substrate at a base point and electrically connected to a radio frequency signal source; and

a parasitic director element having a mast portion oriented substantially perpendicularly to said geometric plane with one end thereof mounted on said substrate;

said director element positioned between said personal computer housing and said driven element and spaced from said driven element to form a plane therewith that is oriented toward said personal computer housing;

whereby the gain of said antenna is greater in a direction toward said personal computer housing than it is in a direction away from said personal computer housing.

9. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a first surface lying in a geometric plane with a conductive layer thereon forming a ground plane;

a antenna mounted on a second surface of said substrate opposite to said first surface and electrically insulated from said ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said ground plane;

a subsystem housing having a supporting surface for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer housing;

a circuit card in said subsystem housing having a first edge mounted to said mechanical connector assembly, said card having logic circuits and radio frequency signal circuits mounted on a first surface thereof;

said logic circuits coupled to electrical terminals in said mechanical connector assembly for exchanging first digital signals with said personal computer, said logic circuits outputting second signals to said radio frequency signal circuits in response to said first signals;

said radio frequency signal circuits coupled to said antenna and outputting radio frequency signals as said radio frequency signal source to said antenna in response to said second signals;

a conductive grounding electrode mounted along the periphery of said first surface of said card for shielding said antenna from said radio frequency signal circuits;

a frame in said subsystem housing having a recessed portion on a first side thereof for mating with said periphery of said card, including a plurality of electrically conductive springs for resiliently contacting said conductive grounding electrode to make electrical contact therewith for shielding said antenna from said radio frequency signal circuits, said springs extending to a second side of said frame opposite to said first side thereof;

a top conductive cover having an edge portion on a first side thereof for mating with said springs on said second side of said frame, said springs resiliently contacting said top conductive cover to make electrical contact therewith for shielding said antenna from said radio frequency signal circuits and for forming a reflecting ground plane for said antenna;

a planar platform surface on a second side of said top conductive cover opposite to said first side, for mechanically supporting and electrically contacting said conductive layer of said ground plane of said antenna, said platform including an aperture therein;

a first shielded coaxial connector mounted on said first surface of said circuit card at a second end opposite from said mechanical connector assembly, said first coaxial connector juxtaposed with said aperture in said planar platform;

a second shielded coaxial connector mounted on said conductive layer of said ground plane of said antenna, for mating engagement with said first coaxial connector through said aperture, a center electrode of said second connector coupled to said antenna;

a bottom conductive cover having an edge portion for mating engagement with an edge of said top conductive cover and having a recessed central portion;

a resilient pad positioned between said recessed central portion of said bottom cover and a second surface of said circuit card opposite to said first surface thereof, for resiliently forcing said plurality of electrically conductive springs into contact with said conductive grounding electrode of said circuit card to make electrical contact therewith, and forcing said springs into contact with said top conductive cover to make electrical contact therewith; and

a conductive adhesive coating on said conductive layer of said ground plane of said antenna, for mechanically and electrically connecting said ground plane to said planar platform surface of said top conductive cover to enable said top conductive cover to form a reflecting ground plane for said antenna;

whereby said antenna is shielded from noise radiated from said radio frequency signal circuits and said top conductive cover forms a reflecting ground plane for said antenna.

10. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a first surface lying in a geometric plane with a conductive layer thereon forming a ground plane;

a antenna mounted on a second surface of said substrate opposite to said first surface and electrically insulated from said ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said ground plane;

a subsystem housing having a supporting surface for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer housing;

a circuit card in said subsystem housing having a first edge mounted to said mechanical connector assembly, said card having logic circuits and radio frequency signal circuits mounted on a first surface thereof;

said logic circuits coupled to electrical terminals in said mechanical connector assembly for exchanging first digital signals with said personal computer, said logic circuits outputting second signals to said radio frequency signal circuits in response to said first signals;

said radio frequency signal circuits coupled to said antenna and outputting radio frequency signals as said radio frequency signal source to said antenna in response to said second signals;

a conductive cover mounted to said circuit card for shielding said antenna from said radio frequency signal circuits, said cover having a planar platform surface on a second side thereof, said platform including an aperture therein;

a first shielded coaxial connector mounted on said first surface of said circuit card at a second end opposite from said mechanical connector assembly, said first coaxial connector juxtaposed with said aperture in said planar platform to enable said circuit card to be tested by connecting a test probe to said first shielded coaxial connector through said aperture prior to assembling said antenna to said subsystem housing;

a second shielded coaxial connector mounted on said conductive layer of said ground plane of said antenna, for mating engagement with said first coaxial connector through said aperture, a center electrode of said second connector coupled to said antenna; and

a conductive adhesive coating on said conductive layer of said ground plane of said antenna, for mechanically and electrically connecting said ground plane to said planar platform surface of said conductive cover and enabling said top conductive cover to form a reflecting ground plane for said antenna;

whereby said antenna can be assembled to said subsystem housing at a time following testing of said circuit card through said aperture and said top conductive cover forms a reflecting ground plane for said antenna.

11. A radio frequency communications input/output subsystem for a personal computer, comprising:

an electrically insulating substrate having a first surface lying in a geometric plane with a conductive layer thereon forming a substrate ground plane;

an antenna mounted on a second surface of said substrate opposite to said first surface and electrically insulated from said substrate ground plane, with a principal axis of said antenna oriented substantially perpendicularly to said substrate ground plane;

a first transmission line mounted on said second surface of said substrate and coupling said base point to said radio frequency signal source, forming a quarter wavelength matching transformer;

a second transmission line mounted on said second surface of said substrate and connected to said base point, forming an impedance match at frequencies lower than said central frequency; and

a third transmission line mounted on said second surface of said substrate and connected to said base point, forming an impedance match at frequencies higher than the central frequency,

a subsystem housing having a supporting surface for maintaining the substrate in a fixed position therewith, and including a mechanical connector assembly for mounting engagement with a mating connector on a personal computer, said antenna positioned at a remote end of said housing from said personal computer;

whereby the antenna has a broad band radiation characteristic.

12. A process for manufacturing a radiofrequency local area network adapter card, comprising the steps of:

building a circuit card;

testing the circuit card by connecting a first coaxial connector thereon to a testing apparatus to perform electrical tests on circuits on the circuit card;

positioning a resilient pad in a recess of a bottom metal cover;

placing the circuit card on top of the resilient pad;

positioning a frame on top of the circuit card, the frame having lower fingers of springs which contact a ground conductor on the circuit card;

placing a top metal cover over the frame with upper fingers of said springs contacting a bottom surface of the top cover and aligning an aperture of the top cover with the first coaxial connector on the circuit card;

pressing downwardly on the top cover against the springs causing them to flex and tightly engage the bottom surface of the top cover and tightly engage the ground conductor of the circuit card;

bringing an edge of the top cover into abutment with an edge of the bottom cover and clamping them into place, to enable the edges to be joined together;

joining the edge of the top metal cover to the edge of the bottom metal cover;

performing a second stage of electrical testing of the circuit card, to test the integrity of the covers for avoiding leakage of radiofrequency radiation;

connecting the first connector on the circuit card to a testing apparatus, by accessing the first connector through the aperture in the top cover and performing electrical tests on the circuits on the circuit card;

inserting a second coaxial connector on a bottom side of the antenna card through the aperture of the top cover, to engage the first coaxial connector on the circuit card;

assembling the antenna card to the top cover with a conductive adhesive coating on a conductive layer of the antenna card, thereby mechanically and electrically connecting the conductive layer to the top conductive cover;

placing a radome over the top cover; and

performing final functional testing to test the performance of the adapter card in communications applications.

13. A process for manufacturing a radiofrequency local area network adapter card, comprising the steps of:

positioning a resilient pad on a bottom metal cover;

placing a circuit card on top of the resilient pad;

positioning a frame on top of the circuit card, the frame having lower fingers of springs which contact a ground conductor on the circuit card;

placing a top metal cover over the frame with upper fingers of said springs contacting a bottom surface of the top cover and aligning an aperture of the top cover with the first coaxial connector on the circuit card;

pressing downwardly on the top cover against the springs causing them to flex and tightly engage the bottom surface of the top cover and tightly engage the ground conductor of the circuit card, said pressing thereby bringing an edge of the top cover into abutment with an edge of the bottom cover to enable the edges to be joined together;

joining the edge of the top metal cover to the edge of the bottom metal cover;

connecting the first connector on the circuit card to a testing apparatus, by accessing the first connector through the aperture in the top cover and performing electrical tests on the circuits on the circuit card;

inserting a second coaxial connector on a bottom side of an antenna card through the aperture of the top cover, to engage the first coaxial connector on the circuit card; and

assembling the antenna card to the top cover with a conductive adhesive coating on a conductive layer of the antenna card, thereby mechanically and electrically connecting the conductive layer to the top conductive cover.