United States Patent £19J
`Skerlos et al.
`
`[II]
`
`[45]
`
`4,426,662
`Jan. 17, 1984
`
`[54]
`
`[75]
`
`IR REMOTE CONTROL
`DETECTOR/DECODER
`Inventors: Peter C. Ske.rlos, Arlington Hts.;
`Thomas J . Zato, Palatine, both of Ill.
`[73] Assignee: Zenith Radio Corporation, Glenview,
`Ill.
`[21) Appl. No.: 340,555
`[22) Filed:
`Jan. 18, l982
`Int. Cl.' ............................................... H04B 9/ 00
`[5 1)
`[52) U.S. Cl . ................................. 358/194.1; 455/603;
`455/ 619
`[58] Field of Search .................. ... 358/194. 1; 455/603,
`455/607, 608, 619
`
`[56)
`
`References Cited
`U.S. PATENT DOCUM ENTS
`J.866.t77 2/t975 Kawama1a ct at ..
`lsoda .
`3.928.760 12/ 1975
`4.121 ,198 10/ 1978 Tsuboi e t al. .
`4,231,031 10/ 1980 Crowther ............................ 455/ 603
`t/ 1981 Davie~ .............................. 358/ 194.1
`4,246,611
`4,337,480 6/ 1982 Bourassi n ......................... 358/194.1
`
`OTHER PUBLICATIONS
`Microcomputer-Based Remote Control System for TV
`
`tV
`
`12
`
`l.R.IN-....,.__)
`
`10
`
`Receivers Tsuboi et al, IEEE T rans Consum Electron(cid:173)
`ics vol.-CE-25 No. 5 Nov. 1979, pp. 731 - 740.
`
`Primary Examiner- Michael A. Masinick
`
`[57]
`ABSTRACT
`A pulse code modulated (PCM) infrared (IR) remote
`control detector/decoder with improved noise immu(cid:173)
`nity particularly adapted fo r use with a television re(cid:173)
`ceiver is disclosed. The IR pulses are modulated by
`means of a high frequency clock signal in translating the
`transmitted signal to a higher frequency, more noise
`immune portion of theIR spectrum. After receipt of the
`transmitted signal by a signal detector, the high fre(cid:173)
`quency modulation is removed from the pulses which
`are then decoded. Under the control of a mic rocom(cid:173)
`puter, the decoder looks for the start data bit and, if
`received, the subsequent control instructions. When the
`data transmission has been decoded, the microcomputer
`activates the appropriate control o utputs to the televi(cid:173)
`sion receiver's tuner system to achieve the desired con(cid:173)
`trol function.
`
`7 Claims, 16 Drawing Figurt:s
`
`tV
`
`---, 58
`I
`:r1-.~
`:;-t
`
`38
`
`:
`I
`I
`I
`-t-- 36
`I
`_}-
`
`32
`
`Roku EX1006
`U.S. Patent No. 9,911,325
`
`

`

`U.S. Patent
`
`Jan. 17, 1984
`
`Sheet 1 of 5
`
`4,426,662
`
`~
`0:
`~
`LLI
`~
`3:
`t-
`;::)
`CL
`t-
`::::>
`0
`
`0
`Q)
`(/)
`E
`0
`CD
`
`0 w
`0 z
`~
`X
`lJJ
`
`~
`I
`~
`z
`C.•
`t-
`frl (/)
`
`0 w
`0 z
`~
`X
`lJJ
`CD
`I
`aJ
`z
`0
`t-
`u w
`
`(/)
`
`0 .,
`
`(/)
`:(.
`0
`~
`
`0
`Q)
`(/)
`~
`
`8 I() j_
`
`ID
`
`~
`-~ ~
`
`~
`-~
`~
`
`~
`-~ ~
`
`

`

`U.S. Patent
`
`Jan. 17, 1984
`
`Sheet 2 of 5
`
`4,426,662
`
`en
`LtJ
`a:::
`._
`en
`LtJ
`...J
`:::>
`.-:x:a..
`~!::a
`en~Lt.J
`z
`1-::
`<ll--<r
`O:::::>_j
`. .-o
`1--a..:::>
`0:::::>0
`....iO~
`
`N
`:I:
`~
`
`t
`z
`LtJ
`:::>
`0
`LtJ
`a::
`LL.
`
`~
`~
`~
`
`LtJ
`0
`:::>
`1--
`~~----~------------------~
`a..
`~
`<l
`
`

`

`N
`0\
`'" 0\
`0\
`N
`.. +:.
`
`+:.
`
`VI
`0 .....,
`w
`0 ....
`0
`::r'
`VJ
`
`w -~.....,J
`
`~
`00
`\0
`......
`
`~ ::s
`~ a
`c . en .
`
`~
`
`63
`
`RECEIVER
`TELEVISION 1
`
`COMPUTER I---62
`
`MICRO-
`
`I __-56
`
`DECODER
`
`PULSE
`
`rn3
`
`30
`
`_.J
`"--32
`I
`-t--36
`I
`I
`I
`I
`
`--:J.... I
`
`l
`
`60
`
`+V
`
`CIRCUIT
`SQUARING I
`
`48
`
`I~54
`---,
`
`1-\38
`
`-=-_j
`
`CONTROL
`
`GAIN
`
`10~
`
`24
`
`20
`
`l.R.IN~
`
`tV
`
`12
`
`

`

`N
`0\
`"' 0\
`0\
`N
`~
`~ ,.
`
`VI
`0 ......,
`~
`~ ...
`
`~
`::r
`(/)
`
`U.S. Patent
`
`Jan. 17, 1984
`
`Sheet 4 of 5
`
`4,426,662
`
`I r-o
`I
`-,
`
`72,
`______________ :.J
`I
`I
`I
`I
`I
`I
`I
`I
`
`;r-~//
`
`-
`
`-
`
`~----------------
`
`-::-
`
`
`
`56/
`
`/.31
`
`"
`
`fo6
`
`68
`
`

`

`U.S. Patent
`
`Jan. 17, 1984
`
`Sheet 5 of 5
`
`4,426,662
`
`I !I
`l7.r-SC lit II~Sec
`
`!
`I
`
`I !
`n~----+'~ n..___
`. I
`I r+-!
`
`-
`
`FCa-S.D j ! ..____ __ ____,
`~.l&r ·
`,.____
`2.07m Sec.-+------~ 3m Sec.
`'I
`'
`;E"./!rSE 'I ~I· - - 2 .07mSec. -+-! -
`I.
`7HoFIU
`n
`I!
`I !
`. a.
`~-----+--+-i
`17!T-' G 1.· I
`! -
`I I
`
`~t5:_7f--+,J ~~--------~' ·
`. I..___
`7RSI I Ill
`
`i I
`-•f4-l• 3m Secil.--l -
`.
`
`IU,___' -
`
`
`
`I IL.t--: -
`
`
`
`I I
`
`

`

`1
`
`4,426,662
`
`2
`additional pulses of a second frequency F2 inserted in
`spaces between the pulses of the first frequency. System
`noise immunity is allegedly improved by making the
`receiver insensitive to noise received during the inte r(cid:173)
`pulse periods. However, this approach requires the use
`of sophisticated pulse processing circuitry because two
`pulse frequencies are utilized and is limited in the num(cid:173)
`ber of pulse codes available since one half of the avail(cid:173)
`able pulse codes must be devoted to filling in the spaces
`between the control signal pulses operating at a fre(cid:173)
`quency of Ft.
`The present invention is intended to overcome the
`aforementioned limitatio ns of the prior art by providing
`a remote control system in which a pulse code modu(cid:173)
`lated control signal is used to modulate a second signal
`so as to transmit the control signal in a more noise free
`portion of the 1R spectrum. The pulse code modulation
`(PCM) approach provides for an increased number of
`available codes and associated television receiver con(cid:173)
`trol functions.
`
`OBJECTS OF THE INVENTION
`Accordingly, it is an object of the present inventio n
`to provide an improved remote control signal detec(cid:173)
`tor I decoder.
`It is another object of the present invention to pro(cid:173)
`vide an IR signal detector/decoder with improved
`noise immunity for use in the remote control of a televi(cid:173)
`sion receiver.
`Still another object of the present invention is to
`reduce the susceptibility of a remote control system to
`spurious inputs by employing pulse code modulated
`control signals having frequencies in a relatively noise(cid:173)
`free portion of the electromagnetic spectrum.
`A still further object of the present invention is to
`provide for the microcomputer-controlled decoding of
`digital remote control signals in a television receiver.
`
`lR REMOTE CONTROL DETECTOR/DECODER
`
`BACKGROUND OF THE INVENTION
`This invention generally relates to remote control 5
`receivers and more specifically is directed to an infrared
`(JR) remote control detector/decoder providing im(cid:173)
`proved noise immunity particularly adapted for use
`with a television receiver.
`Television receiver 1 emote control systems generally 10
`employ either an ultrasonic or optical link. Spurious
`signal problems associated with ultrasonic remote con(cid:173)
`trol systems, such as multi-path reception, telephone
`ringing, key jangling, etc., limit the practicality of these
`systems for home use and have led to wider use of IR 15
`remote control systems. However, even systems utiliz(cid:173)
`ing signals propagated in the IR spectrum suffer from
`spurious inputs resulting in control signal input errors.
`One approach to reducing erroneous inputs in a re(cid:173)
`mote control system in which light signals are used as 20
`the remote control signal is disclosed in U.S. Pat. No.
`3,928,760 to Isoda. This approach utilizes a light signal
`emitted from an electroluminescent diode which is am(cid:173)
`plitude-modulated by a modulated frequency in the
`ultrasonic frequency range. By thus amplitude modulat- 25
`ing a light signal at an ultrasonic frequency, ambient
`noise in the ultrasonic frequency spectrum, such as that
`previously described, is allegedly avoided. In addition,
`it is asserted that by modulating the light signal at a
`rdatively high frequency, amplitude-modulated light 30
`noise generated by various sources, such as nuorescent
`lamps, is avoided.
`An extension of the approach employed in the above
`referenced patent is disclosed in U.S. Pat. No. 3,866, 177
`to Kawamata et al wherein is disclosed a remote control 35
`system using light as a controlling signal which is first
`modulated by a high frequency signal and is then fur(cid:173)
`ther modulated with a low frequency signal. The re(cid:173)
`ceived light signal is demodulated to pick up the low
`freq uency component which serves as the control sig- 40
`naL The purpose of this high and low frequency modu(cid:173)
`ldtion oft he remote control light signal is to avoid spuri(cid:173)
`ou~ inputs generated by DC energized nuorescent
`lamps in which the DC current is transformed into a
`high frequency c urrent of 15kHz to several tens kHz by 45
`a high frequency inverter and energizes the lamp
`thereby. T he high frequency signal thus generated is
`frequently not stable further reducing the desirability of
`a hght signal remote control system modulated at a high
`frequem:y.
`In an attempt to make the remote control system
`more noise immune, the control signal is propagated in
`the form of various combinations of pulses of a single
`frequency wave. With the number of pulses being preset
`in the transmiuer and with the receiver responsive to 55
`only a predetermined number of pulse arrangements,
`~uch remote contro l syste ms proved to be not only
`more noise immune, but also capable of transmitting a
`large number of commands for controlling various
`iunctions of a television receiver. However, even with 60
`the use of complex pulse code schemes, remote control
`l>Y~Iems utilizing this approach offer o nly limited noise
`Immunity.
`U.S. Pat. No. 4, 121,198 to Tsuboi et al represents an
`attempt to further improve the noise immunity of a 65
`pulse code modulation remo te control system. In this
`approach a coded command ~ignal transmitted as a
`plurality of pulses of a first frequency Ft also includes
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The appended claims set forth those novel features
`believed characteristic of the invention. However, the
`invention itself as well as further objects and advantages
`thereof will best be understood by reference to the
`following detailed description of a preferred embodi(cid:173)
`ment taken in conjunction with the accompanying
`drawings, where like reference characters identify like
`elements throughout the va.rious figu res, in which:
`FIGS. IA-JC depict the pulse trains of the transmit-
`50 ted control signal in theIR remote control system of the
`present invention, with a single pulse train shown in
`various degrees of expansion;
`FIG. 2 illustrates the frequency translation of the
`transmiued control signals in the IR spectrum;
`FIG. 3 is a schematic diagram, partly in functional
`block form, of the detector/preamplifier utilized in a
`preferred embodiment of the present invention;
`FIG. 4 shows the detailed logic circuitry of a remote
`control signal decoder utilized in a preferred embodi(cid:173)
`ment of the invention; and
`FIGS. SA-SJ show the wave forms of the signals
`present in various portions of the decoder illustrated in
`FIG. 4.
`
`DESCRIPTION OF T HE PREFERRED
`EMBODIMENTS
`The present invention is utilized with a remote con(cid:173)
`trol system in which pulse code modulated (PCM) out-
`
`

`

`4,426,662
`
`3
`put signals are generated in response to user operated
`controls. The code consists of a start bit comprised of
`the first two pulses followed by five groups of three
`pulses each of a data bit and its complement for control
`signal verification. The entire code, therefore, consists 5
`of II bits of information with a single pulse representing
`a "0" state, while a double pulse represents the "I"
`state.
`The pulses are generated at a frequency in the infra(cid:173)
`red (IR) spectrum and are chopped by a 40 kHz clock 10
`signal. This is done to translate the signal to a higher
`frequency to avoid the usual spectrum of IR noise
`which is more predominant at the lower frequencies.
`The II bits are transmitted in approximately a 56 milli(cid:173)
`second period which is repeated every 180 milliseconds IS
`as long as the transmitter key is depressed. The codes
`for all transmitted functions have the same period; how(cid:173)
`ever, the fi ve bit code generated is unique for each
`function .
`Shown in FIG. lA is the output wave form of the 20
`transmitted IR signal which is repeated every 180 milli(cid:173)
`seconds. Each series of pulses is pulse code modulated
`as shown in FIG. lB wherein an individual pulse train is
`presented in expanded form to show the coded pulse
`arrangement of the transmitted pulse groups. The I I 25
`bits of coded information are transmitted in approxi(cid:173)
`mately 56 milliseconds. Shown in FIG. lC is a still
`expanded view of a single data bit comprised of two
`pulse trains each SOO microseconds in length. A SOD
`millisecond interval is incorporated between individual 30
`pulse trains. The individual pulses shown in FIG. l C
`represent the ON/ OFF pulsing of the tra.nsmitter's light
`emitting diodes (LEOs). The LEOs are pulsed on and
`off in order to permit high current pulses at low duty
`cycles resulting in high power outputs of the I.R. diodes 35
`allowing increased range.
`As previously stated, the IR pulses are modulated by
`a high frequency, i.e., 40kHz, clock signal in the remote
`control transmitter. This results in a translation in the
`transmitted IR signal to a higher frequency in the IR 40
`spectrum as shown in FIG. 2. This frequency transla(cid:173)
`tion is performed in order to remove the transmitted
`signal from a noisy portion of the IR spectrum and
`locate it in a relatively noise-free portion of that fre(cid:173)
`quency spectrum. The plot of IR noise sources and 45
`harmonics in FIG. 2 represents various sources of spuri(cid:173)
`ous inputs in an IR remote control system, such as nuo(cid:173)
`rescent and incandescent lamps and sunlight. By thus
`translating the frequency of the PCM control signals to
`a more noise-free portion of the spectrum, the remote 50
`control system of the present invention is made more
`reliable and receiver signal processing is simplified.
`Referring to FIG. 3, there is shown in schematic and
`block diagram form an IR remote control detector/de(cid:173)
`coder 10 in accordance with the present invention. A 55
`transmitted IR control signal is incident upon a photo
`diode 14 after transiting optical filter 12. Photo diode 14
`is reverse biased by means of a + V voltage source for
`greater sensitivity and is rendered conducting upon
`receipt of an incident IR signal. Connected to the cath- 60
`ode of photo diode 14 is grounded resistor 18 for proper
`diode biasing. The output of photo diode 14 is AC cou(cid:173)
`pled by means of capacitor 16 to the input of a high gain
`amplifier 22 for removing the DC ambient light signal
`from the received pulsed control input signal. In addi- 65
`tion, capacitor 16 in combination with grounded resis(cid:173)
`tor 20 filter out low frequency noise components of the
`received IR control signal. The gain of amplifier 22 is
`
`4
`controlled by means of g.rounded resistor 24 which in
`the preferred embodiment of the present invention is a
`variable resistance.
`Ttie output of high gain amplifier 22 is coupled by
`means of resistor 26 to the base of buffer transistor 28.
`Transistor 28 provides a butTer between high gain am(cid:173)
`plifier 22 and band pass filter 32 and, in combination
`with an emitter grounding resistance 30, further ampli(cid:173)
`fies the control signal input. Resistance 26 provides for
`proper t.ransistor biasing for transistor 28 and limits the
`current thereto. The amplified output of transistor 28 is
`provided to the primary winding 40 of transformer 34 in
`band pass filter 32. Primary winding 40 is also coupled
`by means of resistance 46 to the + V power supply.
`Transformer 34 includes a secondary winding 42 induc(cid:173)
`tively coupled to primary winding 40 for generating an
`output signal in response to the input control signal
`provided to primary winding 40. Signal gain may be
`accomplished in transformer 34 by providing secondary
`winding 42 with a greater number of turns than that of
`primary winding 40. In the preferred embodiment of the
`present invention, the signal gain across transformer 34
`is approximately 4 to I.
`Coupled across secondary winding 42 is grounded
`capacitor 36 which filters out unwanted signal compo(cid:173)
`nents. Thus, transformer 34 in combination with
`grounded capacitor 36 and resistor 50 forms a band pass
`filter network having a transmission frequency cent~d
`around 40 kHz which is the rate at which the incoming
`pulse control signals are modulated. The output of band
`pass filter 32 is provided to envelope detector 38 which
`includes diode 52 and grounded capacitor 54. The posi(cid:173)
`tive portion of the signal transmitted by band pass filter
`32 forward biases diode 52 and renders it conducting.
`The negative portion of the band pass filter signal re(cid:173)
`verse biases diode 52, rendering it nonconducting, and it
`is not transmitted by envelope detector 38. Thus, enve(cid:173)
`lope detector 38 effectively removes the carrier signal
`from the PCM control signals in providing the base
`band control signal pulses to squaring circuit 48. Squar(cid:173)
`ing circuit 48 is incorporated to reshape the pulsed
`output of envelope detector 38 so that the signal pro(cid:173)
`vided by squaring circuit 48 to butTer transistor 60 is
`comprised of well-defined squared pulses similar to
`those received by photo diode 14. In the preferred em(cid:173)
`bodiment of the present invention, squaring circuit 48 is
`a conventional Schmidt trigger circuit.
`The output of squaring circuit 48 is provided to the
`base of buffer transistor 60. With the collector of tran(cid:173)
`sistor 60 coupled to the + V power supply and its emit(cid:173)
`ter coupled to ground via resistance 58. transistor 60
`butTers the output of squaring circuit 48 in providing
`low impedance data pulses having short rise and fall
`times to pulse decoder 56. Pulse decoder 56 then pro(cid:173)
`cesses these serial data control signals, in a manner
`described below, and provides information regarding
`the pulse code to microcomputer 62 at a suitable rate
`allowing microcomputer 62 to process this control data
`in a conventional manner. Microcomputer 62 then pro(cid:173)
`vides control signals to the apparatus to be controlled
`by means of the lR remote control system of the present
`invention. which in a preferred embodiment of this
`invention is a conventional television recdver.
`In a preferred embodiment of the present invention,
`the outputs of microcomputer 62 are provided to the
`television receiver's tuning system, with which mi(cid:173)
`crocomputer 62 may be integrated, in controlling the
`various functions and operating parameters of the tele-
`
`

`

`4,426,662
`
`S .
`vision receiver. Since the processing of the control
`signals in microcomputer 61 and the interfacing of mi·
`c rocomputer 62 with the control device, such as a tele·
`vision receiver, may be conventional in nature and does
`not form a part of the present invention, this portion of s
`the present system is not discussed further herein.
`Referring to FIG. 4, there is shown a PCM control
`signal decoder 56 utilized in a preferred embodiment of
`the present invention. In discussing decoder 56, refer(cid:173)
`ence is made to FIGS. 5A- 5J wherein are presented the 10
`signal levels at various locations in decoder 56. The
`locations A-J in the decoder 56 of FIG. 4 correspond,
`respectively, to the signals shown in FIGS. 5A-5J.
`The pulsed output of the detector portion of the pres·
`ent invention is provided to input pin 66 of decoder 56. lS
`The pu.lsed control signals on line A are shown in PIG.
`SA and are provided to D -type flip-flops 82, 84. A
`clocking signal is provided via input terminal 64 to
`inverters 86, 88 as shown in FIG. 58. ln the preferred
`embodiment of the present invention, this signal is com- 20
`prised of 150 kHz pulses. The output of flip-flops 82, 84
`is provided to AND gate 90, the output of which is
`provided to NAND gate 9l and to AND gates 100, 102.
`The output of NAND gate 92 is coupled to and clears
`D-type flip-flops 75 through 80, .the combination of 2S
`which comprises a counter 71. Thus, a control signal
`input provided to input pin 66 causes a transition at the
`Q output of flip-flop 84 which initiates a monostable
`period which is generated by flip-flops 75 through 80.
`A 14kHz clock signal is also provided to input pin 68 30
`of decoder 56 and thence to one input of NOR gate 70.
`This clock signal is also provided to the clock input of
`D-type flip-flop 98. The other input to NOR gate 70 is
`provided by the output of NOR gate 96 which is en(cid:173)
`abled by the combined Q outputs of flip-flops 75-80. 3S
`When the output from NOR gate 96 to NOR gate 70 is
`low and the clock signal provided to input pin 68 tog(cid:173)
`gles up or down, NOR gate 70 is enabled providing an
`input to the T-input of flip-flop 75. The toggling of
`flip-flop 75 initiates a c hain reaction among the remain- 40
`ing flip-flops in counter 72 such that the clock signal is
`djvided by a predetermined number to provide a pulse
`output from counter 72 of a predetermined duration. In
`the preferred embodiment of the present invention, the
`14 kHz clock signal provided to input pin 68 is divided 4S
`by 29 in counter 72 to provide a 2.07 millisecond output
`from counter 72, as shown in FIG. 50. Once counter 72
`has counted the required time interval, the output of
`NOR gate 96 to ffip-flop 98 is switched.
`The output pulse of AND gate 90, as shown in F IG . SO
`SC, is provided to NAND gate 92 which clears and
`presets counter 72 and is also provided to AND gates
`100, 102. The other input to AND gates 100, 102 is
`provided by D·type flip-flop 98 which is enabled and
`disabled by the output of counter 72. The output pulse SS
`of flip-flop 98 is shown in FIG. 5E and from this it can
`be seen that only during the 2.07 millisecond interval
`provided by counter 72 can the output of flip-flop 98 be
`toggled, or change state. The o utput of AND gates 100,
`102, as shown in FIG. 5G, is determined by theE and F 60
`inputs to AND gates 100, 102. When the output of
`AND gate 90 shown in FIG. 5C is high and the output
`of flip-flop 98 is high, the outputs of AND gates 100,
`102 as shown in FIG. 5G will tum ofT and on in re(cid:173)
`sponse to the high states of signals C and G . When the 6S
`output of flip-flop 98 is high as shown in FIG. 5E, and
`the output pulses of AND gate 90 as shown in F IG . 5C
`are high, the outputs G of AND gates 100, 102 are gated
`
`6
`through NOR gates 104, 106 to a D-type flip-flop 114.
`Thus, an incoming control signal pulse provided to
`input pin 66 sets flip-flop 84 and initiates the counting of
`a predetermjned time interval by counter 72. If a second
`pulse is received by input pin 66 during this interval,
`flip-flop 84 is reset. With the timing interval, signal from
`counter 71 provided to AND gates 100, 101 by NOR
`gate 96 and a control signal input provided to AND
`gates 100, 102 by flip-flop 98, the state of output flip·
`flop 114 is determined by whether or not a control
`signal input was received during the predetermined
`time interval. This is how decoder 56 determines
`whether one or two pulses, a binary "'()"or a binary "I",
`was provided to input pin 66.
`Coupled NOR gates 104, 106 in combination form an
`RS flip-flop and are responsive to the outputs of AND
`gates 100, 102 as shown in FlO. 50. The pulsed output
`of NOR gates 104, 106 is shown in FIG. 5H and from
`this it can be seen that the output of NOR gates 104, 106
`is reset when the output of AND gate 90 momentarily
`goes low as shown in FIG. 5C in setting counter 72.
`When the output of NOR gates 104, 106 is high and the
`clock input thereto as provided via inverter 108 from
`NOR gate 96 goes high, then the output of the D-type
`output flip-flop 114 begins clocking control data into
`the microcomputer 62 where this data is processed in a
`conventional manner. Thus, a high output from flip-flop
`114 represents a double pulse input, or a binary " 1",
`while a low output from flip-flop 114 represents a single
`pulse input, or a binary "0".
`There bas thus been shown a detector/decoder for
`processing pulse code modulated infrared remote con(cid:173)
`trol signals in which the control pulses are modulated
`by means of a high frequency clock signal in translating
`the transmitted signal to a higher frequency, more noise
`immune portion of the IR spectrum. The present inven(cid:173)
`tion detects and decodes these pulse code modulated
`signals and provides these user initiated commands in
`the form of a conventional data pulse train to a mi(cid:173)
`crocomputer which, in tum, directly controls the re(cid:173)
`motely controlled apparatus, such as a conventional
`television receiver.
`While particular embodiments of the prese.nt inven·
`tion have been shown and described, it will be apparent
`to those skilled in the art that changes and modifications
`may be made therein without departing from the inven(cid:173)
`tion in its broader aspects. The aim of the appended
`claims, therefore, is to cover all such changes and modi·
`fications as fall within the true spirit and scope of the
`invention.
`We claim:
`1. In an infrared remote control receiver for process·
`ing pulse code modulated control signals generated in
`response to user selected inputs and modulated by a
`high frequency carrier signal in translating said control
`signals to a higher frequency for remotely controlling a
`plurality of functions in a controlled apparatus by means
`of a microcomputer responsive to said control signals, a
`signal detector/decoder comprising:
`light detecting means for receiyjng .a remote control
`signal transmitted by infrared radiation;
`a band pass filter tuned to the frequency of said carrier
`signal and coupled to said light det ecting means for
`filtering said received control signals;
`envelope detection means coupled to said band pass
`filter for demodulating said carrier signal and for
`recovering said pulse code modulated control signals;
`and
`
`

`

`s
`
`7
`signal decoding means coupled to said envelope detec(cid:173)
`tion means for decoding said pulse code modulated
`contro l signals and providing the thus decoded con(cid:173)
`trol signals to said microcomputer for controlling
`said apparatus;
`wherein said control signal includes an initialization
`pulse with said signal decoding means responsive to
`said initialization pulse for generating and providing a
`sampling interval signal to said microcomputer and
`wherein said signal decoding means decodes said 10
`pulse code modulated control signals and provides
`the thus decoded control signals to said microcom(cid:173)
`puter d uring said sampling interval.
`2. A signal detector/decoder as described in claim l
`wherein said controlled apparatus comprises a televi- 1 s
`sion receiver includi ng a tuning system coupled to and
`responsive to the control signal-initiated outputs of said
`microcomputer.
`3. A signal detector/decoder as described in claim l
`wherein said signal decoder means includes an input 20
`latch coupled to said envelope detector and responsive
`to said pulse code modulated control signal for a prede(cid:173)
`termined ti me period following receipt of said initializa·
`tion pulse, an output latch coupled to said microcom(cid:173)
`puter for providing said decoded control signals thereto 25
`and logic control c ircuitry coupling said input and out·
`put latc hes for decoding said pulse code modulated
`control signals and providing a latching signal represen(cid:173)
`tative thereof to said output latch.
`4. A signal detector/decoder as described in claim 3 30
`wherein said logic control circuitry includes counting
`means coupled to said input latch and responsive to the
`state thereof for providing a predetermined delay be·
`tween the receipt of said initialization pulse by said
`input latch and the transmission of said decoded control 35
`signals by said o utput latch to said microcomputer.
`5. A signal detector/decoder as described in claim l
`wherein said light detecting means comprises a photo
`diode responsive to infrared radiation incident thereon
`in combination with an optical filter through which said 40
`infrared radiation is transmitted prior to being incident
`upon said light detecting means.
`6. In an infra red remote control receiver for process(cid:173)
`ing a pulse code mod ulated control signal generated in
`response to user selected inputs and mod ulated by a 4S
`high frequency carrier signal in translati ng said control
`signal to a higher frequency for remotely controlling a
`plurality of functions in a controlled apparatus by means
`of a microcomputer responsive to said control signal,
`said control signal including an initialization pulse, a SO
`signal detector/decoder comprising:
`light detecting means for receiving a remote control
`signal transmitted .by infrared radiation, said light
`detecting means including a photo d iode responsive
`to infra red radiation incident thereon in combination SS
`with an optical filter through which said infrared
`radiation is transmitted prior to being incident upon
`said light detecting means;
`a band pass filter tuned to the frequency of said carrier
`signal and coupled to said light detecting means for 60
`filtering said received control signals, said band pass
`filter including a transforme r having a primary wind·
`
`4,426,662
`
`8
`ing coupled to said light detecting means and a s~c·
`ondary winding, wherein a grounded c apacitor is
`coupled across said secondary winding;
`envelope detection means coupled to the secondary
`winding of said band pass filter for receiving tht'
`filtered output therefrom, demodulating satd carrier
`signal, and recovering said pulse code modulated
`control signals; and
`signal decoding means coupled to said cnvdope detec·
`tion means for decoding said pulse code modulated
`control signals and providing the thus decoded con·
`trol signals to said microcomputer for controlling
`said apparatus, and wherein said signal decoding
`means is responsive to said inittalization pulse for
`generating and providing a sampling interval signal
`to said microcomputer with said decoded control
`signals provided to said microcomputer during said
`sampling interval.
`7. In an infrared remote control receiver for process·
`ing pulse code modulated control signals generated in
`response to user selected inputs and modulated by a
`high frequency carrier signal in translating satd control
`signals to a higher frequency for remotely controlling a
`plurality of functions in a television receiver by means
`of a microcomputer responsive to said control signals, a
`signal detector/ decoder comprising:
`light detecting means for receiving a remote control
`signal transmitted by infrared radiation;
`a band pass filter tuned to the frequency of' said carrier
`signal and coupled to said light detecting means for
`filtering said received control signals, said band pass
`filter including a transformer having a primary wind(cid:173)
`ing coupled to said light detecting means and a sec(cid:173)
`ondary winding, wherein a grounded capad10r is
`coupled across said secondary winding;
`envelope detection means coupled to the secondary
`winding of said band pass filter for receiving the
`filtered output therefrom, demodulating said carrier
`signal, and recovering said pulse code modulated
`control signals; and
`signal decoding means coupled to said envelope detec(cid:173)
`tion means for decoding said pulse code modulated
`control signals and providing the thus decoded con(cid:173)
`trol signals to said microcomputer for controlling
`said television receiver, said signal decoding means
`including:
`an input latch coupled to said envelope detection means
`and responsive to said pulse code modulated control
`signals;
`an output latch coupled to said microcomputer for pro·
`viding said decoded control signals thereto; and
`logic control circuitry coupling said input and output
`latches for decoding said pulse code modulated con(cid:173)
`trol signals and providing a latching signal represen(cid:173)
`tative thereof to said output latch, said logic control
`circuitry including counting means coupled to said
`latch and responsive to the state thereof for providing
`a predetermined delay between the receipt of said
`initialization pulse by said input latc h and the trans(cid:173)
`mission of said decoded control signals by said output
`latch to said microcomputer.
`• • • • •
`
`6S
`
`