JP3229732B2 - Infrared transmitter and infrared receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception device capable of infrared communication with a personal computer, an electronic organizer, and other general home appliances having an infrared communication function.

[0002]

2. Description of the Related Art Waveforms of typical four-valued PPM, eight-valued PPM, and sixteen-valued PPM among PPM systems conventionally used are shown in FIG. In general, in the 2 ⁿ -valued PPM scheme, a symbol time (represented by T _O in the figure) is divided into 2 ⁿ slots, and a pulse is output only during a slot time corresponding to data. No output. In this case, since n (bit) can be transmitted during the symbol time T ₀ (s), the data rate is n / T ₀ (bps).

[0003] As a conventional technology applying the PPM system to spatial optical communication using infrared rays, for example, US Photonics
There is a Collaborative of the company's products. This adopts 16-level PPM fixed at 1 Mbps in infrared communication.

[0004]

By the way, as a large noise source in infrared communication, there is a noise due to a fluorescent lamp.
FIG. 9 shows the spectral distribution of noise caused by a fluorescent lamp. The noise caused by the fluorescent lamp is abundant in the low frequency band (up to about 200 kHz), and hardly exists above 400 kHz.

[0005] When performing optical communication, an energy-efficient PPM method is often used.
Since the signal spectrum of the PM waveform is often present in the low frequency band, the spectrum overlaps with the low frequency noise caused by the fluorescent lamp. Therefore, it is difficult to remove a noise component using a filter or the like, and the SN ratio is greatly deteriorated. For example, as in the case of Collaborative of Photonics, the data rate is fixed in the conventional PPM method. If the data rate is fixed at a low speed, high-speed communication cannot be performed, and there is a problem of deterioration of the SN ratio as described above. Conversely, if the data rate is fixed at a high speed, there is a problem that communication with a device that can only follow a low data rate cannot be performed.

It is an object of the present invention to solve the problem that the PPM communication system can be used only at a fixed data rate.
An object of the present invention is to simultaneously solve the problem that the SN ratio is degraded due to fluorescent light noise when the PPM communication method is used at a low data rate.

[0007]

SUMMARY OF THE INVENTION An infrared transmitter according to the present invention.
Transmits data having a predetermined data rate to the data rate.
PPM waveforms with a time interval narrower than the time interval corresponding to
A PPM encoding unit to be converted;
An infrared transmitting device that emits the supplied PPM waveform.
Characterized by comprising comprise.

[0008] Further, the infrared transmitting apparatus may be configured so that the data
Within the time interval corresponding to the rate, the PPM waveform is
It is characterized by being repeatedly generated a plurality of times .

[0009] Further, the infrared transmitting apparatus may include
The time interval narrower than the time interval corresponding to the rate is variable
There is a feature. Further, the infrared transmitting device
The signal spectrum of the PPM waveform is
Spectrum with less overlap with the lower frequency spectrum
It is characterized by having. Infrared receiver according to the present invention
Receives the infrared PPM waveform transmitted from the space
An infrared receiving device and the infrared PPM waveform
PP that converts to received data according to the internal data rate
And an M decoding unit. Soshi
The infrared receiving device described above, wherein the PPM decoding unit comprises:
Within a predetermined time interval, the received infrared PPM
Treat the waveforms as representing the same data,
Converts to a single received data based on multiple infrared PPM waveforms
Vinegar Rukoto and features.

[0010]

According to the present invention, the data rate of the PPM system can be made variable without being affected by fluorescent light noise, so that communication with a device that can communicate only at a low data rate becomes possible, and SN The ratio can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 shows a block diagram of the infrared transmitting side and the infrared receiving side. Here, the infrared transmission side has an infrared transmission device and a transmission control unit. The transmission control unit
A data rate holding register for holding a data rate specified by a host (computer or the like), a PPM encoding unit for receiving transmission data from the host, converting it into a PPM pulse format and supplying it to an infrared transmission device Having. The infrared receiving side has an infrared receiving device and a receiving control unit. The reception control unit includes: a data rate holding register for holding a data rate designated by the host; and a PPM decoding unit for receiving a PPM pulse waveform from the infrared receiving device, converting it into reception data, and supplying the reception data to the host. And

The transmitting side knows the data rate by writing the data rate to the data rate holding register of the transmission control section by the transmitting side host. After setting the data rate from the host, the PPM encoding unit receives the transmission data from the host and converts the data into PPM format. The transmission device receives the PPM waveform from the transmission control unit and radiates it to the space as infrared rays.

On the other hand, the receiving side knows the data rate by writing the data rate to the data rate holding register of the receiving control section by the receiving side host. After the reception control unit knows the reception data rate from the host, the reception device receives the PPM waveform radiated from the transmission side and transmitted through space. The PPM decoding unit receives the PPM waveform from the receiving device, converts it into a reception data format, and passes it to the host.

[0015] The transmission control unit has a high data rate P so that the signal spectrum hardly overlaps with the fluorescent lamp noise.
A PM waveform can be generated. The clock for this may be generated by the transmission control unit itself, or may be supplied by the host. Since the signal spectrum in this case hardly overlaps with the fluorescent lamp noise, the transmission control unit uses the same PPM as before.
Waveform is used. That is, one PPM pulse is 1
A symbol (in the case of 2 ⁿ PPM, one symbol is n [bit]).

In order to realize a data rate lower than the above data rate, the transmission control unit does not change the shape of the PPM pulse itself, but forms one symbol with a plurality of PPM waveforms. For example, if one symbol is represented by two identical PPM pulses, the data rate is halved. In general, N
If one symbol is composed of the PPM waveforms, the data rate becomes 1 / N. As long as the receiving unit can reproduce the original data from the N PPM pulse trains, the transmitting side may transmit any N PPM pulses. When the data rate is reduced in this way, since the speed of the PPM pulse itself does not change, most of the signal spectrum exists in the high-frequency band, and is not affected by fluorescent lamp noise. Will be.

FIG. 2 shows an embodiment in which the present invention is applied to infrared data communication of an electronic organizer. In FIG. 2, infrared transceiving units 21, 22, and 23 for executing the present invention are inserted in electronic notebooks 11, 12, and 13, respectively.
Each infrared transmitting / receiving unit is designed to transmit / receive using 4-level PPM, and has an amplifier for amplification and a high-pass filter (cut-off frequency is 300 kHz) for cutting off fluorescent lamp noise. The maximum data rate of the infrared transmitting / receiving unit is 1.2288 Mbps. The processing speed of the main body of the electronic notebooks 11 and 12 is high, and the data rate of transmission and reception can handle up to 1.2288 Mbps.
It can handle only up to 3.6Kbps.

FIG. 3 shows an interface between the electronic organizer body and the infrared transmitting / receiving infrared transmitting / receiving unit. FIG.
In this example, the case where the electronic organizer 11 sends data to the electronic organizer 12 is shown. First, the electronic notebook 11 transmits transmission data (Tx) to a transmission unit (corresponding to the transmission control unit and the infrared transmission device in FIG. 1) in the infrared transmission / reception unit 21.
D), the transmitting unit of the infrared transmitting / receiving unit 21 generates a PPM pulse from the data and radiates the infrared to the space. On the other hand, the receiving unit (corresponding to the receiving control unit and the infrared receiving device in FIG. 1) of the infrared transmitting / receiving unit 22 that has received infrared rays from the space extracts data from the received PPM pulse train and sends the received data (RxD ).

First, the case where the electronic organizer 11 performs data communication with the electronic organizer 12 will be described. Electronic organizer 1
1, 12 and the infrared transmission / reception units 21 and 22 can operate at 1.2288 Mbps, respectively, and thus perform communication at this data rate. In this case, the infrared transmitting / receiving unit 2
The transmission control unit 1 transmits data at the timing shown in FIG. FIG. 5 shows the spectrum distribution of this signal. The PPM waveform received by the infrared transmitting / receiving unit 22 is amplified by an amplifier in the infrared transmitting / receiving unit 22 and passed through a high-pass filter having a cutoff at 300 kHz in the infrared transmitting / receiving unit 22. Since the noise of a fluorescent lamp is often present below 200 kHz, the noise is removed by this filter, and only the PPM waveform can be easily extracted.

Next, a case where the electronic organizer 11 performs data communication with the electronic organizer 13 will be described. Since the electronic organizer 13 can only operate at a maximum of 153.6 Kbps, the data rate needs to be reduced to 153.6 Kbps or less.

First, 153.
Assuming a case of outputting 6 Kbps, data communication is performed at the timing shown in FIG. The spectrum distribution of this signal is as shown in FIG. 11, and it can be seen that the spectrum just overlaps with the spectrum of the noise of the fluorescent lamp.

Therefore, according to the present invention, the infrared transmission / reception unit 21 transmits the PPM waveform to the infrared transmission / reception unit 23 at the same speed as the above. Then, one symbol is composed of eight PPM waveforms. The infrared transmission / reception unit 23 is a PPM that represents the same data as the original data every eight times
Send out a pulse. FIG. 6 shows the timing of the transmitted PPM waveform, and FIG. 7 shows the spectrum of the signal. The PPM waveform received by the infrared transmission / reception unit 23 is amplified by an amplifier in the infrared transmission / reception unit 23 and passed through a high-pass filter having a cutoff at 300 kHz in the infrared transmission / reception unit 23. In this case, since most of the spectrum of the signal exists at 200 KHz or more, only the noise is removed by this filter, and only the PPM waveform can be easily extracted.

The infrared transmission / reception unit 23 determines transmission data from the eight PPM pulses after passing through the filter, and sends 153.6 Kbps reception data (RxD) to the electronic notebook 13. Since the PPM pulse representing the same data as the original data is transmitted eight times, the infrared transmitting / receiving unit 23 detects the most received PPM pulse and determines that the corresponding data has been transmitted. I do.

In the infrared transmitting / receiving apparatus using the PPM method according to the present invention, the data rate can be varied in a time series.

[0025]

According to the present invention, the data rate of the PPM communication system can be varied without deteriorating the fluorescent lamp noise resistance in the infrared physical layer. As a result, it is possible to communicate with a device that can communicate only at a low data rate. Further, since the PPM waveform is transmitted a plurality of times in one symbol, strong error correction and error detection can be performed on the receiving side.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmitting side and a receiving side according to an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment when the present invention is used for infrared data communication of an electronic organizer.

FIG. 3 is a diagram showing an interface when the electronic organizer 11 transmits to the electronic organizer 12, according to the embodiment of the present invention.

FIG. 4 is a diagram showing transmission timing when the electronic notebooks 11 and 12 communicate according to the embodiment of the present invention.

FIG. 5 is a diagram showing a spectrum distribution of the signal shown in FIG. 4;

FIG. 6 is a diagram showing a transmission timing when the electronic notebook 11 and the electronic notebook 13 communicate according to the embodiment of the present invention.

FIG. 7 is a diagram showing a spectrum distribution of the signal of FIG. 6;

FIG. 8 is a diagram for explaining a conventional PPM method.

FIG. 9 is a diagram showing a spectral distribution of noise due to a fluorescent lamp.

FIG. 10 is a diagram showing a transmission timing at which a conventional PPM-based electronic organizer 11 and an electronic organizer 13 communicate with each other.

FIG. 11 is a diagram showing a spectrum distribution of the signal of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Electronic organizer 12 Electronic organizer 13 Electronic organizer 21 Infrared transmitting / receiving unit 22 Infrared transmitting / receiving unit 23 Infrared transmitting / receiving unit

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H04B 10/105 10/14 10/18 10/22 10/26 10/28

Claims (6)

(57) [Claims] 1. A PPM encoder for converting data having a predetermined data rate into a plurality of PPM waveforms at time intervals shorter than the time interval corresponding to the data rate, and a PPM waveform supplied from the encoder. An infrared transmission device that emits light, and wherein the signal spectrum of the PPM waveform has a spectrum in which overlap with a spectrum by a fluorescent lamp is reduced. 2. The infrared transmitting apparatus according to claim 1, wherein the number of PPM waveforms at a time interval narrower than a time interval corresponding to the data rate is variable. 3. The method according to claim 1, wherein the data having a predetermined data rate is converted into data having a time interval narrower than a time interval corresponding to the data rate.
A PPM encoding unit that converts the PPM waveform into a PPM waveform; and an infrared transmitting device that emits the PPM waveform supplied from the encoding unit.The PPM waveform includes a plurality of the PPM waveforms within a time interval corresponding to the data rate. And the signal spectrum of the PPM waveform is
An infrared transmitting device having a spectrum in which overlap with a spectrum by a fluorescent lamp is reduced. 4. The infrared transmitting apparatus according to claim 3, wherein the number of PPM waveforms at a time interval narrower than a time interval corresponding to the data rate is variable. 5. The data rate transmitted from the space ,
Multiple infrared rays with a smaller time interval than the corresponding time interval
An infrared receiving device for receiving a PPM waveform;
An infrared receiving device comprising: a PPM decoding unit that converts a PM waveform into reception data in accordance with a data rate inside the device. 6. The PPM decoding unit processes the received infrared PPM waveform within a predetermined time interval as if the received infrared PPM waveform represents the same data.
The infrared receiving apparatus according to claim 5, wherein the data is converted into a single received data based on the M waveform.