JPH1022923A - Infrared digital data communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared digital data communication equipment efficiently removing impairment external light noise caused by an inverter fluorescent lamp, etc. SOLUTION: A modulation circuit 34 modulates a sub-carrier wave supplied from a frequency synthesizer 26 by transmission data to select a frequency higher than the impairment light noise as the frequency of this sub-carrier wave. In addition at a reception part 24, a signal photodetected by a photodetector 30 is frequency-converted by a mixer circuit 42 to a high frequency outside a frequency range which can be responded by the photodetector 30. Thereby a sub-carrier wave included in a received infrared signal does not include a noise component and the signal is processed by the frequency, which is higher than the impairment light noise picked up by the photodetector 30, by the mixer circuit 43 so that impairment light noise is not mixed into the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared digital data communication apparatus for transmitting and receiving information signals such as audio, video and data.

[0002]

2. Description of the Related Art Conventionally, communication devices using infrared rays have been used in a wide range of fields such as television remote control devices. Furthermore, in recent years, with the progress of computerization in society, it has been applied to data communication between computers and the like.

In the infrared communication apparatus described above,
As a modulation method, AM modulation in which the intensity of infrared rays is changed by a transmission signal may be used. However, in AM modulation, in addition to infrared signals, light beams such as illumination are received, and these become noise and reception interference occurs. Is easy to occur.

[0004] FIG. 5 shows an example of a light beam that becomes a noise in such infrared communication. As shown in FIG. 5, various light beams are noises. To remove these noises, the transmission signal is once modulated by a subcarrier having a different frequency from the disturbance light, and then is a main carrier. Conventionally, a method of re-modulating the infrared light with the sub-carrier is used. Thus, noise due to light rays as shown in FIG. 5 is removed by the filtering effect at the time of demodulation.

FIG. 6 shows an example of a method of modulating infrared rays via the above-described subcarrier. In FIG. 6, a sub-carrier having a predetermined frequency is frequency-modulated (FSK-modulated) by a transmission signal, and the flickering cycle of the infrared is changed by the modulated sub-carrier, so that the amplitude modulation (ASK-modulation) of the infrared as a main carrier is performed. ) Is performed and emitted to space as an infrared signal.

On the receiving side, the infrared signal modulated as described above is received by a light receiving element as shown in FIG. 5, is photoelectrically converted, and is taken out as an electric signal. FIG. 7 shows a frequency spectrum of the reception signal extracted from the light receiving element. In FIG. 7, the spectrum enclosed by the broken line is the spectrum of the subcarrier including the transmission signal. The other spectra are the spectra of noise due to light rays mixed from the various light sources shown in FIG. Therefore, by filtering only the frequency band of the subcarrier, a target signal can be extracted without including noise.

[0007]

However, as shown in FIG. 5, there are various types of light sources that cause noise in infrared communication. In particular, in the case of an inverter fluorescent lamp, its blinking cycle is short, and The disturbance light noise that occurs is
It has reached a frequency of 1 MHz or more, including harmonic components. As described above, the frequency spectrum of the noise mixed into the infrared communication apparatus is not discrete as shown in FIG. 7, but is actually 1 MHz to 1 MHz as shown in FIG.
It exists continuously up to a frequency band exceeding Hz.

On the other hand, as a frequency of the above-mentioned subcarrier, a frequency around 455 KHz is conventionally used.
As shown in FIG. 8, a noise component with high intensity still exists in that frequency band. For this reason, there has been a problem that even if a modulation method via a subcarrier is adopted, noise removal cannot be sufficiently performed.

Further, in a conventional infrared digital data communication apparatus, a superheterodyne system is generally employed in order to improve the sensitivity on the receiving side. In a superheterodyne receiver, amplification is performed at an intermediate frequency lower than the subcarrier frequency,
There is an advantage that a stable high gain can be obtained without being affected by harmonics or the like. However, as described above, the disturbance light noise that enters the receiver exists continuously in a frequency band from DC to over 1 MHz, so that the disturbance light noise having the same frequency as the intermediate frequency is received via an amplifier or the like. And there is a problem that the S / N ratio of the received signal is deteriorated.

In infrared communication, especially in infrared digital data communication, the communication time is long, the data to be transmitted is large, the communication distance is long, and it is necessary to always secure an infrared data transmission path with a plurality of communication partners. Therefore, a communication failure due to disturbance light noise is likely to occur. Therefore, noise removal is extremely important, but as described above, conventional methods have not always been sufficient.

In order to prevent the influence of the disturbance light noise as described above, a method of blocking disturbance light such as a fluorescent lamp or controlling the optical directivity of infrared rays to narrow the light in one direction can be considered. As described above, there is also a problem that the usability is significantly deteriorated by such a method due to the necessity of securing a transmission path with a plurality of communication partners.

An object of the present invention is to provide an infrared digital data communication device capable of efficiently removing disturbance light noise caused by an inverter fluorescent lamp or the like.

[0013]

In order to achieve the above object, the present invention relates to an infrared digital data communication apparatus capable of removing disturbance light noise, wherein a transmitting side modulates an infrared ray with a transmission signal. When performing the modulation, the signal is modulated via a subcarrier having a frequency higher than the disturbance light noise, and the receiving side demodulates the received signal after converting the frequency of the received signal to a high frequency outside the frequency range in which the light receiving element can respond. It is characterized by.

[0014] The sub-carrier is from 1.2 MHz to 3 MHz.
Frequencies in the range of 0 MHz are preferred.

The frequency at which the received signal is frequency-converted is preferably 10.7 MHz or 23 MHz.

An infrared digital data receiving apparatus for receiving an infrared signal and extracting digital data includes a light receiving element for receiving the infrared signal and an output of the light receiving element set to a high frequency outside a frequency range in which the light receiving element can respond. It is characterized by including a mixer circuit for frequency conversion, an intermediate frequency amplifier for amplifying an output of the mixer circuit, and a demodulation circuit for demodulating received data from an output of the intermediate frequency amplifier.

In the above configuration, since the sub-carrier has a higher frequency than the disturbance light noise, it is possible to prevent noise components from being mixed into the sub-carrier and to reduce the frequency range in which the light receiving element can respond on the receiving side. Since the received signal is also frequency-converted to a high frequency, noise can be prevented from being mixed into the received signal from an amplifier or the like via the power supply circuit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of an infrared digital data communication apparatus according to the present invention. In FIG. 1, an infrared data communication device 10 according to the present embodiment includes a control unit 12, a power supply circuit 14, and an infrared digital data communication unit 16.

In the control section 12, digital data is exchanged between the infrared digital data communication apparatus 10 and a computer or a peripheral device connected to the infrared digital data communication apparatus 10 via an interface 18. These digital data are stored in the CPU
The data is transmitted and received between the transmission unit 22 and the reception unit 24 of the infrared digital data communication unit 16 through the communication unit 20. CPU2
0 controls the frequency synthesizer 26 of the infrared digital data communication unit 16 and supplies a signal of a required frequency to the transmission unit 22 and the reception unit 24.

The transmitting section 22 receives the transmission signal to be transmitted from the CPU 20 and modulates the sub-carrier signal supplied from the frequency synthesizer 26. The blinking of the light emitting element 28 is controlled based on the modulated subcarrier signal, and infrared light is emitted into space as an infrared signal.

On the other hand, an infrared signal emitted from another infrared digital data communication device is incident on the light receiving element 30 of the infrared digital data communication unit 16, where photoelectric conversion is performed. The reception signal converted into an electric signal by the light receiving element 30 is demodulated in the reception unit 24, a predetermined transmission signal is extracted, and the transmission signal is supplied to the CPU 20. The received signal is transmitted to the CPU 20 and the interface 18
Is supplied to a computer or a peripheral device connected to the infrared digital data communication apparatus 10 via the.

A predetermined power is supplied from the power supply circuit 14 to the control unit 12 and the infrared digital data communication unit 16 described above.

FIG. 2 is a detailed block diagram of the infrared digital data communication section 16 described above. In FIG. 2, digital data, that is, transmission data, as a transmission signal supplied from the CPU 20 is input to a header ender generation circuit 32 of the transmission unit 22, and a header and an ender are added. The packet generated in this way is
The sub-carrier input to the modulation circuit 34 and thereby input from the frequency synthesizer 26 is modulated. The output signal of the modulation circuit 34 is input to the filter / transmission amplifier 36, where the high frequency component is removed and the output signal is amplified to a predetermined level. The flashing of the light emitting element 28 is controlled by the amplified signal, and emitted to the space as an infrared signal.

From the frequency synthesizer 26 to the modulation circuit 3
The frequency of the subcarrier input to 4 is set to a higher frequency than the various disturbance light noises shown in FIG. This is shown in FIG. 4 as the spectrum of the subcarrier. As a result, when the subcarrier is extracted from the reception signal received by the reception unit 24, disturbance light noise is not included therein.

As described above, the frequency of the disturbance light noise is highest due to the inverter fluorescent lamp,
Since it has a frequency of about 1.2 MHz at the maximum,
Higher frequencies are preferred as sub-carriers. In addition, the frequency characteristics of the light emitting element can correspond to a frequency up to about 30 MHz in a commercially available device.
Therefore, the frequency of the above-mentioned subcarrier is 1.2 MHz.
Frequencies in the range of z to 30 MHz are preferred. In this frequency range, as described above, a commercially available light-emitting element can be used, and it is not necessary to use a light-emitting element of a special specification, so that the cost of the infrared digital data communication device 10 can be reduced.

On the other hand, an infrared signal emitted from another infrared digital data communication device 10 is received by the light receiving element 30 and is photoelectrically converted to an electric signal. The received signal converted into the electric signal is supplied to the subcarrier amplifier 3
8, the gain of which is controlled in accordance with the output of the AGC circuit 40. The output of the sub-carrier amplifier 38 is supplied to the mixer circuit 42 by the frequency synthesizer 2.
6 and is frequency-converted to a predetermined frequency.

From the received signal converted to a predetermined frequency, an intermediate frequency filter 44 extracts a signal only in a frequency band including a target signal. As the intermediate frequency filter, for example, a ceramic filter, a crystal filter, or the like can be used.

The output of the intermediate frequency filter 44 is amplified by an intermediate frequency amplifier 46 and demodulated in a demodulation circuit 48. The signal demodulated by the demodulation circuit 48 is subjected to waveform shaping by the waveform shaping comparator 50 using the reference clock frequency sent together with the data signal, and jitter included in the demodulated waveform is removed.

In this signal, the header and the end of the packet added at the time of transmission in the header / ender detection circuit 52 are removed, and necessary digital data is output to the CPU 20 of the controller 12 as received data.

As described above, a superheterodyne receiver is used as the receiver 24, and a commercially available receiver can be used. Therefore, the cost of the infrared digital data communication device 10 can be reduced. it can.

The frequency of the signal supplied from the frequency synthesizer 26 to the mixer circuit 42 of the receiving section 24 is determined based on the frequency response characteristics of the light receiving element 30. FIG. 3 shows a frequency response characteristic of the light receiving element 30. In FIG. 3, the horizontal axis indicates the frequency of the infrared signal received by the light receiving element 30, and the vertical axis indicates the output of the light receiving element 30. As can be seen from FIG. 3, the frequency response characteristic of the light receiving element 30 does not respond to an incident optical signal of a predetermined frequency or more, that is, has a characteristic of a low-pass filter. Now, suppose that the frequency converted by the mixer circuit 42 is
Assuming that the frequency is within a frequency range in which the light receiving element 30 shown in FIG. 3 can respond, the noise component received by the light receiving element 30 via the power supply circuit 14 shown in FIG. Will be mixed.

That is, a pin photodiode or the like is used as the light receiving element 30, to which a reverse bias voltage is normally applied from the power supply circuit 14. On the other hand, predetermined power is also supplied from the power supply circuit 14 to the intermediate frequency amplifier 46 and the like. Therefore, the noise component picked up by the light receiving element 30 passes through the power supply circuit, enters the intermediate frequency amplifier 46 and the like, and is included in the signal amplified here as noise.

As described above, the light receiving element 3
If the frequency is converted to a high frequency outside the responsive frequency range of 0, no disturbance light noise exists in that frequency band, so that the disturbance light noise picked up by the light receiving element 30 is included in the signal from the intermediate frequency amplifier 46 or the like. Mixing can be prevented.

Since the frequency characteristic of the light receiving element 30 can normally respond to a frequency range from DC to about 3 MHz, the frequency at the output side of the mixer circuit 42 is higher than the frequency range in which the light receiving element 30 can respond. Is fine. Here, as a ceramic filter or the like used as the intermediate frequency filter 44, a filter having a specification of 10.7 MHz or 23 MHz is commercially available. Therefore, if the output of the mixer circuit 42 is set to the above-mentioned frequency, it can be higher than the frequency range in which the light receiving element 30 can respond, and the intermediate frequency filter 44 can be constituted by a commercial product, which is suitable for both noise removal and cost reduction. is there.

FIG. 4 shows the features of the operation of the infrared digital data communication apparatus 10 according to the present embodiment described above. In FIG. 4, the noise component due to disturbance light is D
It is distributed in a frequency range from C to about 1.2 MHz. Therefore, on the transmitting side, the frequency of the subcarrier supplied from the frequency synthesizer 26 to the modulation circuit 34 is set to a higher frequency. As described above, the range is preferably from 1.2 MHz to 30 MHz. By adopting such a subcarrier frequency,
The sub-carrier included in the infrared signal transmitted and received between the transmitting unit 22 and the receiving unit 24 can be placed in a frequency region that is not affected by disturbance light noise. It is possible to prevent noise components from being mixed into the digital data signal.

When the received signal is frequency-converted in the mixer circuit 42 of the receiving section 24, a high frequency outside the frequency range to which the light-receiving element 30 can respond is adopted as the converted frequency. The disturbance light noise picked up by the intermediate frequency amplifier 46
Thus, it can be prevented from being mixed into the digital data signal.

[0038]

As described above, according to the present invention,
By setting the subcarrier frequency to a higher frequency than the disturbing light noise and setting the frequency at which the received signal is frequency-converted to a high frequency outside the frequency range in which the light receiving element can respond, the disturbing light Noise can be prevented from being mixed, and the communication reliability of the infrared digital data communication device can be improved.

In addition, a general superheterodyne receiver can be used as the receiver, and the cost of the apparatus can be reduced.

As described above, a highly reliable infrared digital data communication device can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an infrared digital data communication device according to the present invention.

FIG. 2 is a detailed block diagram of an infrared digital data communication unit of the infrared digital data communication device shown in FIG.

FIG. 3 is a diagram illustrating a frequency characteristic of a light receiving element used in the receiving unit illustrated in FIG. 2;

FIG. 4 is an explanatory diagram of an operation of the infrared digital data communication device shown in FIG.

FIG. 5 is a diagram showing a light source of an optical signal including disturbance light noise entering an infrared digital data communication apparatus.

FIG. 6 is an explanatory diagram of a modulation method of a conventional infrared digital data communication device.

FIG. 7 is an explanatory diagram of a conventional noise removal method for an infrared digital data communication device.

FIG. 8 is a diagram showing a relationship between a subcarrier and a noise component in a conventional infrared digital data communication device.

[Explanation of symbols]

10 infrared digital data communication device, 12 control unit,
14 power supply circuit, 16 infrared digital data communication section, 1
8 interfaces, 20 CPUs, 22 transmission units, 24
Receiving section, 26 frequency synthesizer, 28 light emitting element, 30 light receiving element, 32 header ender generation circuit,
34 modulation circuit, 36 filter / transmit amplifier, 38
Sub-carrier amplifier, 40 AGC circuit, 42 mixer circuit, 44 intermediate frequency filter, 46 intermediate frequency amplifier, 48 demodulation circuit, 50 waveform shaping comparator, 5
2 Header ender detection circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H04B 10/04 10/06 10/02 10/18 H04Q 9/00 311

Claims (4)

[Claims] 1. An infrared digital data communication device capable of removing disturbance light noise, wherein a transmitting side modulates infrared light with a transmission signal via a subcarrier having a higher frequency than the disturbance light noise. An infrared digital data communication apparatus, wherein the modulation is performed, and the reception side converts the frequency of the received signal to a high frequency outside the frequency range in which the light receiving element can respond, and then demodulates the signal. 2. The infrared digital data communication device according to claim 1, wherein said subcarrier has a frequency in a range of 1.2 MHz to 30 MHz. 3. The infrared digital data communication device according to claim 1, wherein the frequency at which the received signal is frequency-converted is 10.
An infrared digital data communication device having a frequency of 7 MHz or 23 MHz. 4. An infrared digital data receiving apparatus for receiving an infrared signal and extracting digital data, comprising: a light receiving element for receiving an infrared signal; and an output of the light receiving element outside a frequency range in which the light receiving element can respond. A mixer circuit for converting the frequency to a high frequency, an intermediate frequency amplifier for amplifying the output of the mixer circuit, and a demodulation circuit for demodulating received data from the output of the intermediate frequency amplifier. Receiver.