JPH07336308A - Optical radio equipment - Google Patents

Abstract

PURPOSE:To eliminate reflection interference signals even when the reflection interference signals generated by the reflection of output signals are mixed in input signals by controlling the output of a variable gain amplifier circuit based on the detection level of reception interference signals. CONSTITUTION:A photodetector 200 detects reception optical signals including interference signals by the reflection from the optical transmission line of a light emitting element 102, converts them to electric signals and inputs them to the common-mode input terminal of an addition circuit 204. The circuit 204 receives the output of a variable amplifier circuit 205 for which transmission data are passed through a delay circuit 101 and amplified in the reverse phase input terminal and outputs signals for which the output signals of the circuit 205 are subtracted from the output signals of the detector 200 to a judgement circuit 202. In the meantime, the output of the circuit 204 feedback controls the gain of the circuit 205 by a level proportional to the amplitude difference of the output signals of the detector 200 and the output signals of the circuit 205. Thus, only desired signal components are present in the output signals of the circuit 204 and improved reception characteristics are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wireless device, and more particularly to an optical wireless device suitable for a communication system for simultaneous bidirectional optical spatial data transmission using different transmission rates.

[0002]

2. Description of the Related Art When performing simultaneous bidirectional optical spatial data transmission using different transmission rates, a transmission signal may be reflected by a reflecting object on the transmission path and be mixed into a reception signal. When the reflected signal mixes with the received signal in this way, the reflected signal becomes an interfering signal and the reception characteristics are significantly deteriorated. Therefore, in the conventional optical wireless device, a filter is used to remove the reflected interference signal.

FIG. 6 is a block diagram showing an example of the configuration of a conventional optical wireless device. In FIG. 6, reference numeral 400 is a transmission data input terminal, 401 is a drive circuit, 402 is a light emitting element, 500 is a photodetector, 501 is a bandpass filter, 502 is a determination circuit, and 503 is a reception data output terminal. The transmission data applied to the transmission data input terminal 400 is converted into an electric signal (generally a current signal) for driving the light emitting element 402 by the driving circuit 401, and the light emitting element 402 is converted.
Is supplied to. The light emitting element 402 sends out an optical signal having an intensity proportional to the amplitude of this current signal. On the other hand, the photodetector 500 receives the received optical signal, but at the same time, the transmitted optical signal sent from the light emitting element 402 is reflected by the reflecting object on the transmission path and becomes a reflected optical signal, resulting in the photodetector 500.
Therefore, the photodetector 500 outputs the received signal including the reflection interference signal together with the desired optical signal.

Therefore, the photodetector 500 converts the received optical signal into an electric signal proportional to its intensity and supplies the electric signal to the bandpass filter 501, and the bandpass filter 501 does not use the interfering signal contained in the input signal. Then, the output signal is supplied to the determination circuit 502. Judgment circuit 5
In 02, the input signal is compared with a reference signal (a DC signal having a predetermined amplitude). For example, when the amplitude of the input signal is larger than the amplitude of the reference signal, the received data has a logical level “1”. , It is judged as “0” when it is small,
The data is output to the reception data output terminal 503.

[0005]

As described above, in the conventional optical wireless device, the filter is used to remove the interfering signal mixed in the received optical signal. There is a problem that it is extremely difficult to remove the reflection interference signal when the difference from the reception transmission rate is small. Further, there is a problem that the waveform of the desired reception signal is greatly distorted due to the band limitation of the filter, and the reception characteristics are significantly deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the drawbacks of the conventional optical wireless device, and performs simultaneous bidirectional optical spatial data transmission using different transmission speeds. In the optical wireless device, the optical wireless device is
A variable gain amplifier circuit that amplifies an output signal from a drive circuit that drives a light emitting element, an adder circuit that subtracts the output signal of the variable gain amplifier circuit from an output signal of a photodetector, and a receiver included in the output of the adder circuit A level detection circuit for detecting the signal level of the interfering signal, and controlling the gain of the variable gain amplification circuit based on the output signal of the level detection circuit.

Further, the optical wireless device further includes a variable delay circuit for delaying the output signal of the variable gain amplifier circuit, and a unit for detecting a phase difference between the reception interference signal and the output signal from the variable gain amplifier circuit. A phase difference detection circuit is provided, and the delay of the variable delay circuit is controlled based on the output signal of the phase difference detection circuit.

Further, the optical wireless device further comprises an operation mode control circuit, and performs training of gain control of the variable gain amplifier circuit and delay control of the variable delay circuit in the training operation mode, and then performs the training to the adder circuit. Gain control information and delay control information when there is no amplitude difference and delay difference between the two input signals to be input, and the variable gain amplification based on these gain control information and delay control information in the normal operation mode are obtained. The gain of the circuit and the delay of the variable delay circuit are controlled.

[0009]

As described above, the interfering signal mixed in the received signal is a signal in which the transmitted signal is reflected by the reflecting object on the transmission line, and thus it is known. In the optical wireless device of the present invention, by utilizing the fact that this reflection interference signal is known, an adder circuit and a variable gain amplifier circuit for amplifying the output signal from the drive circuit for driving the light emitting element are provided to receive the received signal. The reflected interference signal is removed by reducing the output of the variable gain amplifier circuit from. In this case, the signal level of the reception interfering signal included in the output of the adding circuit is detected, and the gain of the variable gain amplifying circuit is controlled according to this signal level, so that the output of the variable gain amplifying circuit and the interfering signal are Received interference signals are removed with the same amplitude.

Further, by providing a variable delay circuit to delay the output of the variable gain amplifier circuit, when there is a timing deviation between the received optical signal input to the adder circuit and the input signal from the variable gain amplifier circuit. , The effect of timing deviation can be removed. In this case, a circuit for detecting the phase difference between the reception interference signal included in the output of the adding circuit and the output signal of the variable gain amplifying circuit is provided, and the output of the adding gain amplifying circuit is controlled according to this phase difference. hand,
Eliminate accurate reception interference signals.

Further, an operation mode control circuit is provided, which is configured to perform training of gain control and delay control,
In the training operation mode, a test transmission signal of a predetermined pattern is sent to obtain proper gain control information and delay control information, and these are stored and stored in the normal operation mode. The gain of the variable gain amplifier circuit based on the gain control information and the delay control information,
In addition, the delay of the variable delay circuit is controlled so that it can be used even when a high-speed response is required.

[0012]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a block diagram showing a configuration of a first embodiment of an optical wireless device of the present invention. This embodiment shows an example in which the transmission rate of the transmission signal is lower than the transmission rate of the reception signal. In the figure, reference numeral 100 is a transmission data input terminal, 101 is a drive circuit, 102 is a light emitting element, 200 is a photodetector,
201 is a band pass filter, 202 is a determination circuit, 203
Is a reception data output terminal, 204 is an addition circuit, 205 is a variable gain amplification circuit, 206 is a low-pass filter, and 207 is a level detection circuit.

The adder circuit 204 is provided between the photodetector 200 and the bandpass filter 201, and the variable gain amplifier circuit 205 is provided between the drive circuit 101 and the adder circuit 204. The output of the addition circuit 204 is supplied to the low-pass filter 206, and the output of the low-pass filter 206 is supplied to the variable gain amplification circuit 205 via the level detection circuit 207.

The transmission data signal applied to the transmission data input terminal 100 is input to the drive circuit 101, and the drive circuit 101 supplies a current proportional to this input signal to the light emitting element 102.
And a current that is k times (k is a constant) the driving current for driving the light emitting element 102 are supplied to the variable gain amplifier 205.

The light emitting element 102 emits a transmission optical signal having a light intensity proportional to the drive current supplied from the drive circuit 101. When this optical signal is transmitted on the transmission line,
When reflected by a reflective object on the transmission path, this reflected signal is input to the photodetector 200. Therefore, the photodetector 20
The received optical signal received at 0 may include a desired optical signal and a reflected optical signal. The photodetector 200 converts this received optical signal into an electrical signal proportional to its intensity and outputs it to the in-phase input terminal of the adder circuit 204.

On the other hand, the output of the variable gain amplification circuit 205 is supplied to the negative phase input terminal of the addition circuit 204, and the addition circuit 204 extracts the output signal of the variable gain amplification circuit 205 from the output signal of the photodetector 200. Output the subtracted signal. Therefore, if the amplitude of the reflection interference signal included in the output signal of the photodetector 200 is equal to the amplitude of the output signal of the variable gain amplifier circuit 205, only the desired signal component exists in the output signal of the adder circuit 204. As a result, good reception characteristics can be obtained.

The output signal of the adder circuit 204 is supplied to the bandpass filter 201, where unnecessary noise is removed, and then supplied to the decision circuit 202. The judgment circuit 202 judges whether the received data is at the logical level "0" or "1" from the amplitude of the input signal, and outputs the judgment result to the received data output terminal 203 as the received data.

The output signal of the adder circuit 204 is supplied to the low pass filter 206. Low pass filter 2
Reference numeral 06 extracts an interfering signal component included in the output signal of the adding circuit 204 and supplies it to the level detecting circuit 207.
The level detection circuit 207 detects the average value of the interference signal component, supplies the average value to the variable gain amplification circuit 205, and controls the gain of the variable gain amplification circuit 205. With such a configuration, the output level of the level detection circuit 207 is proportional to the difference between the amplitude of the reflection interference signal included in the output signal of the photodetector 200 and the amplitude of the output signal of the variable gain amplification circuit 205. Will be done.

Here, the output signal of the photodetector 200 is a signal for turning on / off the current values 0 and I1, and the output signal of the variable gain amplifier circuit 205 turns on the current values 0 and I2.
It is assumed that the signal is a signal to be turned on / off and there is a timing deviation τ between these output signals. FIG. 2 is a waveform diagram showing output waveforms of the photodetector 200, the variable gain amplification circuit 205, and the addition circuit 204 in this case. The average value of the interference signal components detected by the level detection circuit 207 is the average value = −τ × I2 + (T−τ) × (I1−I2) + τ.
× I1 = (I1−I2) × T However, T is the reciprocal of the data transmission rate, and a level proportional to the amplitude difference between the output signal of the photodetector and the output of the variable gain amplifier circuit can be obtained. The gain of the variable gain amplifier circuit 205 is, of course, the level detection circuit 20.
When the output of 7 is positive, the gain is increased, and when it is negative, the gain is decreased.

As described above, in the optical wireless device according to the first embodiment of the present invention, the adder circuit 204 is provided and the photodetector 2 is provided.
00, the output of the variable gain amplifier circuit 205 is subtracted to supply the received data signal to the determination circuit 202 to remove the reception interference signal, and the gain of the variable gain control circuit 205 is changed to the level detection circuit. The output of 207, that is, the output signal of the photodetector 200 and the variable gain amplifier circuit 20.
Since feedback control is performed by the level proportional to the amplitude difference of the output signal of 5, the amplitudes of the two signals input to the adder circuit are the same, and the reception interference signal can be removed.

Example 2. FIG. 3 is a block diagram showing the configuration of the second embodiment of the optical wireless device according to the present invention. In addition,
In the following embodiments, the same or corresponding parts as those of the device shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the first embodiment shown in FIG. 1 described above, the photodetector 20
Although the amplitude of the output signal of 0 and the amplitude of the output signal of the variable gain amplifier circuit 205 are made equal to remove the reception interference signal, for example, the input timing of the reflection interference signal and the transmission signal. If there is a timing deviation from the input timing of, the influence of the reflection interference signal remains on the output signal of the adding circuit 204. The second embodiment is configured to correct this timing deviation. Although this embodiment can be applied to the case where the timing deviation is less than 1/2 of the cycle of the transmission signal, most of the communications in this type of optical wireless device satisfy this condition.

In FIG. 3, reference numeral 208 is a band pass filter, 209 is a level detection circuit, and 210 is a variable delay circuit. In this embodiment, the variable delay circuit 210 is arranged on the input side of the variable gain amplifier circuit 205, but it may be arranged on the output side. The output of the drive circuit 101 is
The signal input to the variable delay circuit 210 and delayed according to the output of the level detector 209 is added to the variable gain amplifier circuit 205.
Output to. The output of the adder circuit 204 is band-limited by the low-pass filter 206, and the level detection circuit 20
7 and the band pass filter 208.

The signal supplied to the bandpass filter 208 contains a frequency component equal to ½ of the baud rate of the signal, and the amount of this frequency component is the pulse width τ (the amount corresponding to the timing deviation). Is proportional to. The center frequency of the bandpass filter 208 is set to ½ of this baud rate frequency, so the signal after passing through the bandpass filter 208 is a sine wave signal having a frequency of ½ of the baud rate frequency. Become.

This signal is further output to the level detection circuit 209. The level detection circuit 209 detects the effective value or peak value of the signal, supplies this information to the variable delay circuit 210, and controls the delay amount. Note that this control is performed so as to reduce the delay amount when the output level of the level detection circuit 209 is positive.

As described above, in the optical wireless device of the second embodiment, since the delay circuit 210 is provided to correct the timing deviation between the input timing of the reflection interference signal and the input timing of the transmission signal, The influence of the reflection interference signal does not remain on the output signal of the adder circuit 204. In this case, a sine wave signal having a frequency proportional to 1/2 of the baud rate frequency of the signal, that is, the pulse width τ (amount corresponding to the timing deviation) is taken out, and the delay circuit is delayed according to the peak value or the effective value. Since the delay of 210 is controlled, the delay amount according to the timing deviation can be accurately obtained.

Example 3. FIG. 4 is a block diagram showing the configuration of Embodiment 3 of the optical wireless device of the present invention. The optical wireless communication system may require a high-speed response, and in this case, the response becomes difficult with the closed loop control as in the above-described first and second embodiments. The third embodiment is an apparatus applicable even when such a high-speed response is required. In addition to the transmission data input terminal 100, the operation mode control signal input terminal 300 and the transmission control signal input terminal 301 are provided. An operation mode control circuit 302 for controlling the operation mode according to input signals from these terminals is provided.

FIG. 5 shows the drive mode control circuit 3 shown in FIG.
FIG. 6 is a block diagram showing an example of the configuration of 02. In FIG. 5, reference numeral 302-1 is a transmission / reception control circuit, and 302-2 is A.
/ D conversion circuit, 302-3 is a switch, 302-4 is an averaging circuit, 302-5 is a storage circuit, 302-6 is a D / A
A converting circuit, 302-7 is an A / D converting circuit, 302-8 is a switch, 302-9 is an averaging circuit, 302-10 is a memory circuit, and 302-11 is a D / A converting circuit.

At the operation mode control signal input terminal 300,
An operation mode control signal for operating the optical wireless device in the normal mode or the training mode is input. When the logic level of this input signal is "1", the optical wireless device operates in the training mode, and when it is "0", it operates in the normal mode. What is this training mode?
As a transmission signal, for example, a repeating pattern of logic levels “1” and “0” is sent for a certain period of time to obtain gain control information and delay control information when the reflection interference signal is removed, and this is stored in a storage circuit. This is the operating mode to be used. A transmission control signal is input to the transmission control signal input terminal 301. Here, transmission is performed when the transmission control signal is at the logic level "1",
It is not transmitted when it is "0", and is valid only when the operation mode control signal is the logical level "0", that is, the normal mode.

First, the operation of the gain control system in the training mode will be described. When the logic level of the operation mode control signal is “1”, that is, in the training mode, the transmission / reception control circuit 302-1 supplies the drive circuit 101 with a repeating pattern of logic levels “1” and “0”, The light emitting element 102 transmits an optical signal having a repeating pattern of "1" and "0". As described above, the level detection circuit 207 includes only the reflection interference signal among the outputs of the adder circuit 204, and outputs this output as A /
It is supplied to the D conversion circuit 302-2 and the switch 302-8. In the A / D conversion circuit 302-2, the level detection circuit 20
The output signal of No. 7 is converted into a digital signal at a constant cycle, the digital signal is averaged by the averaging circuit 302-4, and then written in the memory circuit 302-5.

However, this writing operation is performed by the transmission / reception control circuit 302-1 at the end of the training mode.
That is, the time when the logic level of the operation mode control signal changes from “1” to “0” and the time when the transmission ends in the normal mode, that is, the transmission control signal input to the transmission control signal input terminal 301 changes from “1” to “0”. It is controlled so that it is performed only when it changes to ". In addition, the memory circuit 302-
The storage capacity of 5 is one data, and is configured to store only updated and latest data.

The output of the memory circuit 302-5 is converted into an analog signal by the D / A converter 302-6, and the switch 3
02-3. The switch 302-3 selects the output signal of the level detection circuit 207 in the training mode, and the D / A conversion circuit 302- in the normal mode.
It operates so as to select the output signal of No. 6 and supply it to the variable gain amplifier circuit 205. With such a configuration, the storage circuit 302-5 can finally store the variable gain amplification circuit control information when there is no amplitude difference between the two input signals of the addition circuit 204. Therefore, at the time of normal transmission, the adder circuit 20 stored in the storage circuit 302-5 is used.
The value when there is no amplitude difference between the two input signals of No. 4 is output from the switch 302-3 to the variable gain amplifier circuit 205 as a control signal.

Next, the training mode of the delay control system will be described. The output signal of the level detection circuit 209 of the delay control system is the A / D conversion circuit 302-7 and the switch 3
02-8. The A / D conversion circuit 302-7 converts the output signal of the level detection circuit 209 into a digital signal at a constant cycle, and the digital signal is averaged by the averaging circuit 30.
After averaging in 2-9, it is written in the memory circuit 302-10.

However, by the transmission / reception control circuit 302-1, this writing operation is completed at the end of the training mode, that is, at the time when the logic level of the operation mode control signal changes from "1" to "0" and the transmission in the normal mode. It is controlled to be performed only at the end time, that is, at the time when the transmission control signal input to the transmission control signal input terminal 301 changes from "1" to "0". In addition, the memory circuit 302-
The capacity of 10 is for one data, and only the latest data is stored.

The output of the storage circuit 302-10 is converted into an analog signal by the D / A converter 302-11 and supplied to the switch 302-8. The switch 302-8 selects the output signal of the level detection circuit 209 in the training mode, and the D / A conversion circuit 30 in the normal mode.
It operates so as to select the output signal 2-11 and supply it to the variable delay circuit 210. With such a configuration, the storage circuit 302-10 finally stores the variable delay circuit control information when there is no delay difference between the two input signals of the adder circuit 204. Therefore, at the time of normal transmission, the adder circuit 2 stored in the storage circuit 302-10 is used.
The value when there is no amplitude difference between the two input signals 04 is output from the switch 302-8 to the variable delay circuit 210 as a control signal.

As described above, by providing the operation mode control circuit 302, the above-described training mode is executed when the power of the optical wireless device is turned on, or when the optical wireless device is not in communication, so that the storage circuits 302-5 and 302-10 are properly operated. The variable gain amplifier circuit control information and the variable delay circuit control information are stored, and in the normal mode, by controlling the variable gain amplifier circuit and the variable delay circuit using the stored information, It becomes possible to deal with the response sufficiently. Since the contents of the storage circuits 302-5 and 302-10 are updated at each transmission, it is possible to follow the change of the interfering signal with time.

[0036]

As described above, according to the optical radio apparatus of the present invention, even when the reflection interference signal generated by the reflection of the output signal is mixed in the input signal, it is possible to obtain the reception data from which the reflection interference signal is removed. It is possible to ensure good communication quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing respective output waveforms of a photodetector, a variable gain amplifier circuit, and an adder circuit of the optical wireless device of the present invention.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.

5 is a block diagram showing a configuration example of an operation mode control circuit of the device shown in FIG.

FIG. 6 is a block diagram showing a configuration of a conventional optical wireless device.

[Explanation of symbols]

 100 Transmission Data Input Terminal 101 Drive Circuit 102 Light Emitting Element 200 Photodetector 201 Bandpass Filter 202 Judgment Circuit 203 Received Data Output Terminal 204 Adder Circuit 205 Variable Gain Amplifier Circuit 206 Low Pass Filter 207,209 Level Detection Circuit 208 Bandpass Filter 210 Variable Delay Circuit 302 Operation Mode Control Circuit

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Claims (3)

[Claims] 1. A variable gain amplifier circuit for amplifying an output of a drive circuit for driving a light emitting element, and an output signal of a photodetector in an optical wireless device for simultaneous bidirectional optical spatial data transmission using different transmission rates. From the output signal of the variable gain amplifier circuit, and a level detection circuit for detecting the signal level of the reception interference signal included in the output of the addition circuit, and based on the output signal of the level detection circuit, An optical wireless device having a configuration for controlling the gain of a variable gain amplifier circuit. 2. A variable delay circuit for delaying the output signal of the variable gain amplifier circuit, and a phase difference detection circuit for detecting the phase difference between the reception interference signal and the output signal of the variable gain amplifier circuit. The optical wireless device according to claim 1, wherein the delay of the variable delay circuit is controlled based on the output signal of the phase difference detection circuit. 3. An operation mode control circuit is provided, and in the training operation mode, two input signals input to the adder circuit are trained for gain control of the variable gain amplifier circuit and delay control of the variable delay circuit. Gain control information and delay control information when there is no amplitude difference and delay difference between them, and in the normal operation mode, the gain of the variable gain amplifier circuit and the variable control circuit based on the gain control information and the delay control information. The optical wireless device according to claim 2, wherein the optical wireless device is configured to control the delay of the delay circuit.