_
`United States Patent
`
`[19]
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`US005189543A
`[11] Patent Number:
`
`5,189,543
`
`
`
` Lin et al. [45] Date of Patent: Feb. 23, 1993
`
`
`
`[54]
`
`[75]
`
`INFRA-RED WIRELESS KEYBOARD
`SYSTEM
`,
`
`Inventors: Steve Lin, Taiepi; Kent Kao, Keelung
`City; Robert I-Isue, Hsing—Chuang
`City’ an of Taiwan
`
`[73] Assignee: Acer Incorporated, Taiwan
`[21] Appl. No.: 615,567
`
`OTHER PUBLICATIONS
`Infoworld, Jul. 17, 1989, Darrow, B. (359/ 172).
`Pliotolink TM RS-232, Photonics Corporation 1989.
`(359/172).
`Primary Examiner—Edward L. Coles, Sr.
`Assistant Examir1er—Kinfe-Michael Negash
`Attorney’ Agent’ or Fl.rm__Greg T. Sueoka
`[57]
`ABSTRACT
`
`A communication system comprising a wireless key-
`'
`.
`board for emitting infra-red signals, a receiving unit for
`NW‘ 19’ 1990
`[22] Filed‘
`converting the infra-red signals to an electrical signal, a
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`carrier filtering circuit for removing the camer compo-
`’
`nent of the input signal, a single-shot circuit coupled to
`the carrier filtering circuit for convening its input signal
`to a known code wave form, and a microprocessor for
`receiving the code wave. The invention allows multiple
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`[56]
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`,
`References cued
`U.S. PATENT DOCUMENTS
`4,628,541 12/1986 Beavers ............................... 455/617
`4,897,821
`1/1990 Thierry et al.
`.
`455/603
`4,905,279 2/1990 Nishio ....... ..
`455/603
`4,914,517
`4/1990 Dutfield .............................. 455/603
`
`3 Claims, 3 Drawing Sheets
`
`2
`
`SELECTING
`SIGNALS
`
`KEY MATRIX
`
`
`
`
`
`DE“'3‘3T'ON
`INFRA-RED
`DRIVER
`
`
`CONTROL
`SIGNALS
`
`OSCILLATING
`SIGNALS
`
`RPX Exhibit 1038
` RPX Exhibit 1038
`RPX v. DAE
`RPX V. DAE
`
`STATUS SIGNALS
`
`
`
`
`
`
`
`POWER SOURCE
`CONTROL CIRCUIT
`
`
`
`
`
`

`
`U.S. Patent
`
`Feb. 23, 1993
`
`Sheet 1 of 3
`
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`
`U.S. Patent
`
`Feb. 23, 1993
`
`Sheet 3 of 3
`
`5,189,543
`
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`
`1
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`5,189,543
`
`2
`
`INFRA-RED WIRELESS KEYBOARD SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`This invention is in the field of infra-red communica-
`
`tions. More particularly, it relates to multi-user infra-red
`communication systems.
`Methods and apparatus for emitting infra-red signals
`for use‘in wireless communication systems are known.
`One such system is shown in U.S. Pat. No. 4,628,541,
`the specification of which is incorporated herein for all
`purposes. Known infra-red wireless keyboard systems
`can accommodate multiple users with multiple chan-
`nels. In operation, an ID code is combined with the
`signals transmitted by the wireless keyboard. This com-
`bined signal is then transmitted at a particular carrier
`frequency. The receiver, which is coupled to the com-
`puter system, can determine from the received ID code
`which channel the keyboard is using. Although this
`arrangement allows for multiple ‘users, these multiple
`users cannot simultaneously access the computer with-
`out causing mutual interference. If two users were to
`attempt to input data simultaneously into their respec-
`tive computer systems, the fact that the carrier frequen-
`cies are the same will result in the loss of the ID code
`and data to both systems.
`As an example of the interference problem, assume
`two different users are transmitting to two separate
`computer systems, the first user transmitting on channel
`1 and the second user transmitting on channel 2. Using
`known wireless keyboard systems, the first user can
`transmit data to the first computer system through
`channel 1, but if the second user attempts to transmit
`data simultaneously to the second system, both sets of
`data will be destroyed due to interference.
`Given the limitations of the known wireless keyboard
`systems, a wireless keyboard that can transmit data
`simultaneously with other keyboards without interfer-
`ing with them or being interfered with would be an
`advance of the known art.
`
`SUMMARY OF THE INVENTION
`
`In a preferred embodiment of the present invention,
`each channel is programmed with its own ID code and
`its own designated carrier frequency. Whenever a key is
`depressed, the key code and the ID code are transmitted
`according to the known RS 232 format at a designated
`frequency by an infra-red Light Emitting Diode
`(‘LED’). The receiving unit receives the infra-red signal
`and outputs a corresponding electrical signal to a tuning
`and amplifying circuit for further processing.‘The pro-
`cessed signals are transmitted to a carrier filtering cir-
`cuit which strips off the carrier and outputs the result to
`a single-shot circuit. The single-shot circuit converts
`the signals to a code wave of RS 232 type which is then
`sent to the microprocessor.
`The carrier frequency is designated by the user,
`within a narrow band of frequencies. The ID codes and
`the carrier frequency associated with each channel is
`different. Thus, even if multiple users are transmitting
`simultaneously, the tuning circuit of the receiver can be
`set to a particular carrier frequency, rejecting simulta-
`neously received signals having different carrier fre-
`quencies.
`The invention will now be described in detail with
`reference to the figures listed and described below.
`
`10
`
`I5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram of an infra-red wireless
`keyboard which incorporates the present invention;
`FIG. 2 is a block diagram of a receiver for receiving
`signals from the wireless keyboard, the receiver incor-
`porating the present invention; and
`FIG. 3 is a detailed circuit diagram of the tuning,
`amplifying and carrier-filtering circuits shown in FIG.
`2.
`
`DESCRIPTION OF THE SPECIFIC
`EMBODIMENT(S)
`
`FIG. 1 is a block diagram of an infra-red wireless
`keyboard/transmitter constructed according to the
`teaching of the present invention. It comprises micro-
`processor 1, key matrix 2, channel switch 3, infra-red
`driver 4, power source control circuit 5 and battery 6.
`Channel switch 3 allows a user to select and operate on
`a given channel with a carrier frequency preassigned by
`microprocessor 1.
`In operation, microprocessor 1 sends scanning signals
`to key matrix 2 in order to detect the depression of one
`of the keys. If no keys are depressed, power source
`control circuit 5 places microprocessor 1 into a low-
`power standby mode. Control circuit 5 also resets mi-
`croprocessor 1 if power is cut off, ensuring proper mi-
`croprocessor operation in all cases. If a key has been
`depressed, control circuit 5 switches microprocessor 1
`to a normal operating mode. Microprocessor 1 assigns a
`key code to the depressed key according to its position
`in the key matrix. Microprocessor 1 then references
`channel switch 3 to obtain the proper ID code, each
`channel having a predefined ID code. The ID code and
`the key code are then combined into a 2 byte data word
`by microprocessor 1. Software in microprocessor 1 then
`generates a carrier frequency preassigned to the se-
`lected channel by microprocessor 1. Microprocessor 1
`transmits the 2 byte data word according to a known
`communications format such as RS 232, at the carrier
`frequency. Infra-red driver 4 emits the data through an
`infra-red LED.
`FIG. 2 shows a receiver of infra-red signals con-
`structed according to the teachings of the present in-
`vention. It comprises receiving unit 20, tuning and am-
`plifying circuit 2l, carrier filtering circuit 22, single-
`shot circuit 23, and microprocessor 24.
`Receiving unit 20 receives infra-red signals from in-
`fra-red driver 4 and outputs a corresponding electrical
`signal to tuning and amplifying circuit 21. If the carrier
`frequency of the received signal does not match the
`user-preset frequency designated by the tuning circuit,
`the received signal is rejected. If the carrier frequency
`of the received signal matches the preset frequency
`designated by the tuning circuit 21, the received signal
`is amplified by the amplifying circuit 21. The amplified
`signal is then sent to carrier filtering circuit 22 which
`strips off the carrier and sends the resulting signal to
`single-shot circuit 23. Single-shot circuit 23 converts its
`input into a code wave signal having a wave form of RS
`232 type and sends this RS 232 wave to microprocessor
`24. The width of the code wave pulse is controlled by
`the time constant control signals, generated by control
`circuit 26. Microprocessor 24 receives the ID code and
`data code outputted by single-shot circuit 23. If the ID
`code is correct, the data code will be received and sent
`to a computer system (not shown in FIG. 2) via key-
`board connector 25. It should be noted that interference
`
`

`
`3
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`5,189,543
`
`4
`board means including a channel switch circuit for
`user selection of the carrier frequency;
`a receiving means for receiving the infra-red signals
`and for converting the received signals to an elec-
`trical signal;
`a tuning and amplifying circuit means coupled to the
`receiving means, the tuning circuit capable of being
`tuned to a preset carrier frequency by the user, the
`tuning circuit receiving the electrical signal and
`transmitting it to the amplifying circuit if the car-
`rier frequency of the electrical signal and the preset
`carrier frequency tuned on the tuning circuit means
`are the same, the amplifying circuit amplifying the
`electrical signal;
`a carrier filtering circuit means, coupled to the tuning
`and amplifying circuit means for filtering the car-
`rier component of the electrical signal;
`single-shot circuit means coupled to the carrier filter-
`ing circuit means,
`the single‘-shot circuit means
`converting the demodulated electrical signal to a
`code wave signal compatible with a predefined
`communication signal protocol; and
`a microprocessor coupled to the single-shot circuit
`means for receiving said code wave signal and for
`determining if the ID code is correct.
`2. The system of claim 1, wherein the tuning and
`amplifying circuit comprises a remote control preampli-
`fier and at least one tuning circuit for allowing a user to
`select among a plurality of frequencies.
`3. The system of claim 1, wherein said predefined
`communications format is the RS 232 signal protocol.
`8
`t
`3
`t
`I
`
`if
`invention,
`problems could occur with the present
`several users in the same area attempt to tune their
`transmitters and receivers to the same frequency. In this
`case, some procedure must be implemented to allocate
`the frequencies.
`FIG. 3 shows the tuning and amplifying circuit 21
`and carrier filter circuit 22 of FIG. 2 in greater detail.
`The functions of circuits 21 and 22 are performed by a
`NEC p.PC 14741-IA integrated circuit and two discrete
`tuning circuits. The output is provided on pin 1 of the
`integrated circuit, which is the output of carrier filter-
`ing circuit 22 in FIG. 2. The detailed description of the
`UPC 1474 HA is contained in a product specification
`appended hereto as Appendix A.
`The present invention has now been described in a
`preferred embodiment. Various changes and modifica-
`tions are readily envisioned and fully within the scope
`of the invention. For example other communications
`means other than an RS 232 communications means can
`be used. Additionally, the tuning and amplifying circuit
`of FIG. 2 could be duplicated in order to have a more
`accurate band pass function. Accordingly, the scope of
`the invention should be limited only by the breadth of
`the claims.
`What is claimed is:
`1. A communication system comprising:
`a wireless keyboard means for emitting infra-red sig-
`nals, the infra-red signals comprising an ID code
`and data, the code and data being transmitted ac-
`cording to a predefined communication format at a
`user-selected carrier frequency, the wireless key-
`
`'
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`5
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`10
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`15
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`20
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`25
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`30
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`35
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`45
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`50
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`55
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`65