Antenna system and apparatus for radio-frequency wireless keyboard

This application is a continuous of application Ser. No. 08/932,753, now U.S. Pat. No. 6,138,050, filed Sep. 17, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless keyboards for use in a data processing system and, more specifically, to antenna systems for wireless keyboards for use in a data processing system.

2. Description of the Related Art

Wireless keyboards for use with personal computers are known. Specifically, wireless infrared keyboards for use with personal computers are known. An infrared wireless keyboard simply uses an infrared transmitter in the keyboard and an infrared receiver in a personal computer to establish an input link from the keyboard to the personal computer. The wireless infrared keyboard does not, of course, need a physical wire connection between the keyboard and the personal computer so that there is no wire clutter.

The infra-red wireless keyboard, however, has numerous drawbacks. Specifically, the infrared wireless keyboard requires a clear line-of-sight between the infrared transmitter in the keyboard and the infra-red receiver in the personal computer. Moreover, the distance between the infrared keyboard and the personal computer must not be too great so that the infrared receiver in the personal computer cannot detect the infrared beam from the infrared transmitter of the wireless keyboard.

The clear line-of-sight and distance requirements constrain the flexibility a that user would desire with regard to a wireless device because an artificial limit is placed on the location and the distance that can exist between the infrared wireless keyboard and the personal computer. In addition, the infrared wireless keyboard has large power consumption requirements because of the infrared transmitter. The infrared wireless keyboard typically operates on a six-volt power source that is commonly derived from four 1.5-volt batteries. Moreover, the increased power consumption reduces overall battery life so that the batteries must be replaced more often.

Conventional radio-frequency (“RF”) wireless keyboards addressed some of the shortcomings of the infrared wireless keyboards. Conventional RF wireless keyboards required less power than infrared wireless keyboard, and therefore, provided greater overall battery life so that batteries were replaced less often.

Conventional RF wireless keyboards had drawbacks. One drawback is that the requirement of an RF antenna being large enough so that it is efficient in transmitting RF signals. For example, a conventional RF antenna using electromagnetic propagation principles has a RF antenna that is of the same order of size as the RF wavelength. For example, a 27 MHz signal has a wavelength of eleven meters and would require an antenna of approximately three to six meters for signal transmission. Such a large RF antenna, however, is incompatible with devices such as the wireless keyboard that must be small enough to remain convenient and handy.

To accommodate the requirement of a large antenna without frustrating the advantages of the convenience and handiness of a wireless keyboard, complex and expensive antenna circuitry is incorporated into the conventional RF wireless keyboard. Such circuitry, however, increase the production costs associated with the conventional RF wireless keyboard. Further, the complex and expensive circuitry also increases the power consumption by the system, and therefore, reduces the battery life so that the batteries are replaced more often. Moreover, in some instances even the complex and expensive antenna circuitry still lacks the efficiency for transmitting RF signals that a large RF antenna provided.

Therefore, there is a need for an antenna system for a wireless keyboard that (1) has operational flexibility without physical restraints on communication between the wireless keyboard and a personal computer, (2) is inexpensive to operate and produce without complex and expensive added circuitry, (3) is compact enough to reside within a small housing, (4) consumes less power, and (5) is relatively easy to realize.

SUMMARY OF THE INVENTION

The present invention includes a low-cost, efficient, compact antenna system for use in a wireless keyboard. The wireless keyboard includes a housing and keys. The antenna system includes a radio-frequency antenna for use in a radio-frequency wireless keyboard. The radio frequency (“RF”) antenna remotely couples the wireless keyboard to a personal computer or other device capable of receiving input from a keyboard.

The antenna system of the radio-frequency wireless keyboard includes an antenna wire having a first end and a second end, an RF printed circuit board that includes a digital processing circuit and a RF transmitter circuit, and a metallic plate having a first end and a second end within the wireless keyboard. In one embodiment, the printed circuit board may include a ground portion. The antenna system resides within the housing of the wireless keyboard.

The first end of the metallic plate is coupled to the an output of the RF transmitter circuit, which in one embodiment may be coupled to the ground portion. The second end of the metallic plate is coupled to the first end of the antenna wire. The second end of the antenna wire is coupled to another output of the RF transmitter circuit. Thus, the structure of the present invention forms an antenna loop that includes the antenna wire and the metallic plate as a component of the antenna loop. The antenna loop is used to generate a magnetic field from which RF signals are transmitted in accordance with electromagnetic propagation principles.

The RF printed circuit board includes a digital processing circuit and a RF transmitter for the radio frequency wireless keyboard. The metallic plate within the keyboard may be a metallic plate that is preexistent within a housing of a conventional keyboard. The metallic plate in the keyboard protects against electrostatic discharge. The metallic plate also creates a more rigid keyboard structure and adds some weight to the keyboard to generate a feeling of quality and durability with a user.

The antenna loop of the present invention has a length approximately equal to the length of the keyboard and a width that is as large as the remaining free space (height, length, and/or width)within the keyboard. Moreover, the antenna system is designed so that the entire antenna loop may be located within the housing of a conventional keyboard.

In an alternative embodiment, the RF antenna of the antenna system may be comprised of the metallic plate. For example, in one embodiment the antenna wire may be substituted with a cut-out of the metallic plate. The antenna system includes a metallic plate with a first portion and a second portion and a cut-out space in-between. The first portion is coupled to an output of the RF transmitter circuit and the second portion may be coupled to another output of the RF transmitter circuit or a ground. An antenna loop is formed by the first and the second portions and the length of the antenna loop is the length of the keyboard while the width of the antenna is as large as the remaining free space (height, length, and/or width) of the keyboard. Again, the antenna loop is used to generate a magnetic field from which the RF signals are transmitted.

In another embodiment of the present invention, the RF transmitter may be directly coupled to the metallic plate without having a ground connection. The antenna system is comprised of the metallic plate. The metallic plate operates as a whip or dipole antenna that is used to generate an electric field from which RF signals are transmitted in accordance with electromagnetic propagation principles.

The present invention advantageously uses the metallic plate preexisting in many conventional keyboards as a part of the antenna system to increase the radiation efficiency of the antenna. Further, the present invention illustrates this increase in efficiency by providing good radiation characteristics in both horizontal polarization and vertical polarization. The increased efficiency of the present invention beneficially provides a wireless keyboard that consumes less power than conventional wireless keyboards. In one embodiment, the antenna system and apparatus uses only a 3.0 volt power supply, such as that provided by two 1.5-volt batteries, for example.

In addition to the increased efficiency and reduced power consumption, the present invention is also advantageously compact so that it can reside within the housing of the wireless keyboard. The present invention also provides for easy connection to the printed circuit board that includes the radio-frequency transmitter.

The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a block diagram of a data processing system including a wireless keyboard in accordance with the present invention;

FIG. 2

is a diagram illustrating a computer keyboard in accordance with the present invention;

FIG. 3

a

is a diagram illustrating an internal structure of a wireless keyboard in accordance with the present invention;

FIG. 3

b

is a block diagram of an RF transmitter printed circuit board (“RF transmitter PCB”)

410

in accordance with the present invention;

FIGS. 4

a

,

4

b

, and

4

c

are diagrams illustrating one embodiment a radio frequency antenna system within the housing of a wireless keyboard in accordance with the present invention;

FIGS. 5

a

,

5

b

, and

5

c

are diagrams illustrating alternative embodiments of a radio frequency antenna system within the housing of the wireless keyboard in accordance with the present invention;

FIGS. 6

a

,

6

b

, and

6

c

are diagrams illustrating a second embodiment of a radio frequency antenna system within the housing of a wireless keyboard in accordance with the present invention; and

FIGS. 7

a

and

7

b

are diagrams illustrating a third embodiment of a radio frequency antenna system within a housing a wireless keyboard in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be described with reference to the Figures, where like reference numbers indicate identical or functionally similar elements. The present invention includes a low-cost, efficient, compact antenna system for use in a wireless keyboard device. The antenna system includes a radio-frequency (“RF”) antenna system.

FIG. 1

illustrates a data processing system

101

in accordance with the present invention. The data processing system

101

includes a processor system

110

having a central processing unit (“CPU”)

115

, a radio-frequency (“RF”) receiver subsystem

120

, an input device subsystem

130

a

, a video subsystem

135

a

, and a data bus

140

. The CPU

115

, the receiver subsystem

120

, the input device subsystem

130

a

, and the video subsystem

135

a

are all coupled to the data bus

140

.

In addition, the data processing system

101

includes a mouse

130

b

, a video monitor

135

b

and an RF wireless keyboard

125

. The input device subsystem is coupled with an input device, for example the mouse

130

b

. The video subsystem

135

a

is coupled to a video system, for example the video monitor

135

b

. The RF receiver subsystem

120

is coupled to an RF input device, for example the wireless keyboard

125

.

The RF receiver subsystem

120

may be a mono receiver or may be a multiple receiver. That is, the RF receiver subsystem

120

may be coupled via RF with the wireless keyboard alone or with the wireless keyboard and other RF transmitting devices, for example a RF wireless mouse. It is noted that in an alternative embodiment the RF receiver subsystem

120

maybe a standalone-type device that may be coupled to, but is located external to, the processor system

110

.

During operation of the data processing system

101

, the wireless keyboard

125

transfers RF signals representing particular keys of the keyboard to the processing system

110

, and more specifically, to the RF receiver system

120

. The RF receiver system

120

converts the RF signal to the appropriate key character and passes the key character to the CPU

115

for processing. The CPU

115

may forward the key character to the display unit

135

for display.

FIG. 2

is an external diagram of one embodiment of the wireless keyboard

125

in accordance with the present invention. The wireless keyboard

125

having a housing

210

and a keycap subsystem

215

that includes one or more keycaps

215

a

. The housing

210

may be composed of a plastic, for example an injection molded thermoplastic or other similar material. Further, the keycaps

215

a

may also be composed of a thermoplastic material.

It is noted that the keyboard function of the wireless keyboard

125

may be functionally and structurally similar to a commercially available keyboard such as a 101-key keyboard from IBM Corporation of Armonk, N.Y., a wave keyboard from Microsoft Corporation, of Redmond, Wash., or a membrane-type keyboard, for example. In addition, the dimensions of the wireless keyboard

125

may be approximately 46 centimeters by 18 centimeters by 3 centimeters, for example.

FIG. 3

a

is a diagram of internal structural components of a keyswitch system

301

of the wireless keyboard

125

. The keyswitch system

301

includes a keyswitch pad

310

, a keyswitch printed circuit membrane (“keyswitch PCM”) subsystem

315

that includes one or more keyswitch printed circuit membranes, and a metallic plate

320

. The keyswitch pad includes keyswitches

325

that are membrane keyswitches or mechanical keyswitches, for example. It is noted that in an alternative embodiment, the keyswitch PCM subsystem

315

maybe substituted with a keyswitch printed circuit board (“keyswitch PCB”). Further, the keyswitch PCB may be constructed to incorporate the metallic plate

320

, for example as a thin copper film.

The keyswitch pad

310

and the keyswitch PCM subsystem

315

may be comprised of a lightweight flexible plastic or other similar material. The metallic plate

320

may be comprised of a metallic material that may be flexible or substantially rigid and may have dimensions of 40 centimeters by 15 centimeters, for example. The keyswitches

325

are membrane keyswitches or mechanical keyswitches, for example. Each keyswitch

325

a

is associated with a particular keycap

215

a

that is, in turn, associated with a particular character or function on the wireless keyboard

125

.

The keyswitch pad

310

is coupled to the keyswitch PCM subsystem

315

. The combination of the keyswitch pad

310

and keyswitch PCM subsystem

315

is coupled to the metallic plate, which provides structural rigidity for the keyswitch system

101

of the wireless keyboard

125

. The metallic plate

320

also protects the keyswitch PCM subsystem

315

against electrostatic discharge.

In addition, the keyswitch PCM subsystem

315

includes a series of electrical contacts. Each electrical contact is in an open position until closed by a particular keyswitch

325

a

. A keyswitch

325

a

closes the electrical contact when the associated keycap

215

a

is depressed by a user. As further described below, the RF wireless keyboard

125

transmits an RF signal representing the character or function associated with the particular keycap

215

a

and keyswitch

325

a

to the RF receiver subsystem

120

.

FIG. 3

b

is a block diagram of an RF transmitter printed circuit board (“RF transmitter PCB”)

410

, or alternatively an RF transmitter printed circuit membrane (“RF transmitter PCM”), in accordance with the present invention. The RF transmitter PCB

410

generates RF signals for transmission to the receiver subsystem

120

. The RF transmitter PCB

410

includes a digital processing circuit

350

and a low-power RF transmitter circuit

360

having two output terminals. In one embodiment, one output terminal is an electrical ground

370

of the transmitter PCB

410

. The digital processing circuit

350

is coupled to the RF transmitter circuit

360

.

The digital processing circuit

350

includes a keyswitch scanner subsystem

352

and a keyswitch encoder subsystem

354

. The RF transmitter circuit

360

includes a modulator subsystem

362

and may also include an amplifier subsystem

364

. The scanner subsystem

352

is coupled to the keyswitch PCM subsystem

315

and the keyswitch encoder subsystem

354

. The keyswitch encoder subsystem

354

is coupled to the modulator subsystem

362

. The modulator subsystem

362

is coupled to the amplifier subsystem

364

. The RF transmitter circuit

360

is coupled to an RF antenna system in accordance with the present invention.

In one embodiment, during operation of the wireless keyboard

125

the scanner subsystem

352

scans the keyswitch PCM subsystem

315

to detect a closed electrical contact as a result of a depressed keycap

215

a

. Once detected, the keyswitch encoder subsystem

354

generates an encoded data signal associated with a character or function of the depressed keycap

215

a

. The encoded data signal is modulated by the modulator subsystem

362

so that it may be transmitted as an RF signal. The RF signal may also be amplified by the amplifier subsystem

364

before transmission by the RF antenna system. It is noted that the RF transmitter PCB

410

, as well as other electrical systems within the RF wireless keyboard

125

, may be powered by a battery supply such as two 1.5 volt alkaline or nickel-cadmium batteries, for example.

FIG. 4

a

is a diagram of one embodiment of an RF antenna system

401

within the wireless keyboard

125

in accordance with the present invention.

FIG. 4

b

is a standalone diagram of an RF antenna system

401

in accordance with the present invention. The RF antenna system

401

includes the metallic plate

320

, an antenna wire

415

, and a connector wire

420

. The RF antenna system

401

may include the RF transmitter PCB

410

.

The antenna wire

415

is coupled at a first end to an output of the amplifier subsystem

364

of the RF transmitter PCB

410

and is coupled at a second end to a first end or section of the metallic plate

320

. A second end or section of the metallic plate

320

is coupled, through the connector wire

420

, to a second output of the amplifier subsystem

364

, which may be the ground

370

of the RF transmitter PCB

410

.

The antenna wire

415

and the metallic plate

320

form an antenna loop that is coupled to the outputs of the amplifier subsystem

364

. The length of the antenna loop may be approximately equivalent to the length of the wireless keyboard

125

and the width of the antenna loop may be as large as the remaining free space (height, length, and/or width) within the wireless keyboard

125

. For example, the antenna loop may have a length of 40 centimeters and a width of 2 centimeters. In alternative embodiments the length and/or the width of the antenna loop may be enlarged or shortened.

The antenna loop of the antenna system

401

generates a magnetic field from which the RF signals from the RF transmitter circuit

360

are transmitted to the receiver subsystem

120

in accordance with electromagnetic propagation principles. The space between the antenna wire

415

and the metallic plate

320

provides a large antenna loop surface for transmitting the RF signals.

It is noted that in one embodiment of the present invention, the RF antenna system

401

includes an antenna wire

415

having one turn. In an alternative embodiment of the present invention, the antenna wire

415

may have more than one turn. For example,

FIG. 4

c

illustrates an antenna loop having an antenna wire

415

with two turns. The additional turns of the antenna wire

415

expands the surface area of the antenna loop to increase the transmission range of the RF antenna system

401

. Further, it is noted that in alternative embodiments of the present invention the antenna loop may lie in the same geometric plane as the metallic plate

320

as shown in

FIG. 5

a

or in any other plane, for example, as shown in

FIGS. 5

b

and

5

c.

FIG. 6

a

is a diagram of a second embodiment of an RF antenna system

403

within the RF wireless keyboard

125

in accordance with the present invention.

FIG. 6

b

is a standalone diagram of the second embodiment of the RF antenna system

403

in accordance with the present invention. It is noted that the antenna system

403

is functionally equivalent to the antenna system

401

.

The RF antenna system

403

includes a second embodiment of a metallic plate

322

having a first antenna portion

322

a

and a second antenna portion

322

b

, the RF transmitter PCB

410

, and the connection wires

420

. The RF antenna system

403

may also include the RF transmitter PCB

410

. It is noted that the second embodiment of the metallic plate

322

is functionally and structurally similar to the metallic plate

320

described above.

The first antenna portion

322

a

and the second antenna portion

322

b

are from the same metallic plate

322

and form a cut out space

322

c

in-between. One output of the amplifier subsystem

364

of the RF transmitter circuit

360

is coupled via a connection wire

420

to the first antenna portion

322

a

. The second output of the amplifier subsystem

364

of the RF transmitter circuit

360

, which may be the ground

370

of the RF transmitter PCB

410

, is coupled to the second antenna portion

322

b.

An antenna loop is formed by the first antenna portion

322

and the second antenna portion

322

b

of the metallic plate

322

. Once again, the length of the antenna loop may be approximately equivalent to the length of the wireless keyboard

125

and the width of the antenna loop may be as large as the remaining free space (height, length, and/or width) within the wireless keyboard

125

. The antenna loop may lie in any plane as described above with respect to

FIGS. 5

a

,

5

b

, and

5

c.

The cut-out space

322

c

between the first antenna portion

322

a

and the second antenna portion

322

c

provides for a large antenna loop surface for transmitting RF signals. Further, the metallic plate may be cut out to include more than two antenna portions to form a cut-out space having two or more turns as illustrated in

FIG. 6

c

. As described above with respect to

FIG. 4

c

, the additional turns expand the surface area of the antenna loop to increase the transmission range of the antenna system

403

. Once again, the RF signals that are transmitted by the antenna loop may be received by the receiver subsystem

120

.

FIG. 7

a

is a diagram of a third embodiment of an RF antenna system

405

within the RF wireless keyboard

125

in accordance with the present invention.

FIG. 7

b

is a standalone diagram of the third embodiment of the RF antenna system

405

. It is noted that the antenna system

405

is similar to the antenna system

401

such that a large order antenna size is not required to transmit RF signals from the RF transmitter circuit

360

of the wireless keyboard

125

.

The antenna system

405

includes a third embodiment of a metallic plate

324

, the RF transmitter PCB

410

, and the connection wire

420

. It is noted that the third embodiment of the metallic plate

324

is similar to the metallic plate

320

with respect to, for example, serving as part of the antenna system while preventing electrostatic discharge and providing structural rigidity. The output of the amplifier subsystem

364

of the RF transmitter circuit

360

is coupled through the connection wire

420

directly to the metallic plate

324

. There is no ground connection between the metallic plate

324

and the RF transmitter PCB

410

.

The antenna system

405

includes the metallic plate

324

that operates a whip or dipole antenna. The whip antenna of the antenna system

405

generates an electric field from which RF signals are transmitted to the receiver subsystem

120

in accordance with electromagnetic propagation principles.

During operation of the wireless keyboard

125

, when a keycap

215

a

is depressed, an amplified RF signal is generated from the RF transmitter PCB that represents the character or function associated with the depressed keycap

215

a

as described above with respect to

FIG. 3

b

. The RF signal is output from the amplifier subsystem

364

along the antenna loop (current flow) or whip (voltage differential) of the antenna system

401

,

402

,

403

for transmission from the RF wireless keyboard

125

. The RF signal that is transmitted through the antenna system

401

,

403

,

405

may be received by the receiver subsystem

120

for processing the RF signal.

In one embodiment of the present invention the antenna system

401

,

403

,

405

is tuned to transmit the RF signals at a frequency of 27 MHz, although it may also be tuned to transmit at other functionally equivalent frequencies. Transmitting RF signals at a frequency of 27 MHz generates a wavelength of approximately eleven meters. While conventional RF antennas are three to six meters in size to transmit such RF signal, the present invention is advantageously compact to fit within the wireless keyboard

125

without performance loss or degradation.

The antenna system

401

,

403

,

405

of the present invention beneficially uses the metallic plate

320

,

322

,

324

present in a wireless keyboard as a part of a RF antenna system for RF communication with the receiver subsystem

120

. Integrating the metallic plate

320

,

322

,

324

provides efficiencies for transmission of RF signals as existing keyboard components are used for the antenna system

401

,

403

,

405

. Further, using the metallic plate

320

,

322

,

324

as a part of the antenna system

401

,

403

,

405

prevents transmission of distorted RF data signals resulting from excessive attenuation or interference because of the presence of the metallic plate

320

,

322

,

324

in the keyboard. It is noted that the metallic plate

320

,

322

,

324

may be of different geometric shapes and have various configurations without departing from the spirit of the invention.

The present invention also increases antenna efficiency by providing good radiation characteristics in both horizontal polarization and vertical polarization. Thus, the quality of the RF signal link between the wireless keyboard

125

and the receiver subsystem

120

remains a good quality link even if the RF transmitter circuit

360

or the receiver subsystem

120

are not flat on a table. Another advantage of the antenna system

401

,

403

,

405

is that the receiver subsystem

120

does not require a customized configuration and can simply be integrated within a desktop or tower personal computer. In addition to begin efficient, the antenna system

401

,

403

,

405

is also compact so that it can fit within the keyboard housing

210

of the wireless keyboard

125

.

The antenna system

401

,

403

,

405

of the present invention also provides a benefit of using the low-power RF transmitter subsystem

364

for transmission of RF signals. Specifically, power consumption is reduced so that battery-life is increased in the wireless keyboard

125

. For example, the antenna system

401

,

403

,

405

allows for the use of a 3.0 volt power supply, e.g., two 1.5-volt batteries, that last longer than a 6.0 volt or larger power supplies in conventional wireless keyboards.

While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and components disclosed herein and that various modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims.