JP3137167B2 - Transceiver and return light canceling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates, regarding <br/> the transceiver device and the returning light cancellation Way Method of optical wireless communication performing transmission received at the same time.

[0002]

2. Description of the Related Art Conventionally, a plurality of information processing terminal devices such as a plurality of personal computers (hereinafter, referred to as personal computers) are connected to each other to connect to a LAN (Local Area Neighbor).
In the case of constructing a work (work), the personal computers are connected to each other by a wire such as a coaxial cable or an optical cable. Wired connection is advantageous in that there are few data errors due to external noise because mechanically reliable connection is possible, but there are problems such as high cost of wiring work and work required for every layout change. .

In recent years, there has been an increasing demand for data transmission by interconnecting portable information processing terminal devices such as laptop computers, book computers, palmtop computers, and electronic notebooks. Since these devices are originally intended to be portable and used, it is extremely rare to use them in a state of being connected by wire. For this reason, there have been many restrictions, such as mechanical damage to the connection part due to the insertion and removal of the connector and the troublesome connection work. Therefore, there is a demand for making all or a part of the transmission path wireless so that a personal computer can be connected.

[0004] There are two types of wireless transmission means, one using radio waves as a medium and the other using light as a medium. For high-speed data transmission, wireless transmission using light, which has no legal restrictions, is advantageous. It is. Further, since the Ethernet LAN, which is the most widely used wired LAN, has a transmission speed of 10 Mbps, it is desirable that the wireless transmission line has a transmission speed of 10 Mbps. Further, the wireless transmission line completely replaces the wired transmission line. In order to realize the above, it is essential to use a complete two-way transmission path.

[0005]

However, in optical wireless transmission, light is transmitted to free space and receives light from free space. Therefore, for example, the transmission signal light transmitted by an object located near the device is transmitted by itself. Is reflected and the like and is input to the receiving unit, so that it is impossible to accurately extract a desired communication signal of the other party.

[0006] The present invention focuses on the above problems,
The purpose of this invention is to solve this problem effectively, and the purpose is to cancel the signal due to the return light by branching a part of the transmission signal, adjusting the level and phase of this signal and adding it to the reception signal. It is an object of the present invention to provide an optical wireless communication transmitting / receiving device and a return light canceling method.

[0007]

As a result of intensive studies, the present inventor has found that, in order to cancel the influence of the reflected light of the optical signal transmitted by itself, the phase of a part of the transmission signal is adjusted and this is inverted to the reception signal. The present invention has been accomplished by obtaining the finding that the addition can be carried out in a phase.

[0008] The first device invention is defined in the claims.
However, there is a transmitting unit and a receiving unit for performing optical wireless communication between a plurality of transmitting and receiving devices, and a part of a frequency band used as a transmission signal has a frequency band different from other transmitting and receiving devices. In the assigned transmitting and receiving device, a phase adjusting unit for adjusting the phase of the transmission signal of the transmitting unit,
A filter unit that extracts a signal in a frequency band assigned only to the transmission signal of the transmission / reception device from the reception signal from the reception unit as a test signal, and a reference signal in the same frequency band as the test signal in the transmission signal. A return light canceling device includes a comparing unit for comparing the inspection signal with the test signal, and a level adjusting unit for adjusting an output level of the phase adjusting unit based on an output of the comparing unit.

According to a second aspect of the present invention, packet data is transmitted between a plurality of transmitting and receiving apparatuses.
The same frequency band is used by the Chester-encoded communication signal.
A transmission / reception device for performing full-duplex two-way optical wireless communication using the communication signal , wherein the communication signal is transmitted and the communication signal is used.
A transmission unit that transmits by inserting pilot signals single frequency <br/> number different from the other transceiver is assigned to the rest period between the delivery period of each of the communication signals in a frequency band use, A receiving unit for receiving a communication signal transmitted from another transmitting / receiving apparatus , and a receiving signal received by the receiving unit;
The return light of the transmission signal transmitted from the transmission unit
And a return light canceling device for adjusting the phase of the transmission signal branched and supplied from the transmission unit to the phase of the return light received by the reception unit.
And phase adjuster that adjust a fixed amount for, from the receiving unit
Allocated to the pilot signal from the received signal branched and supplied
A filter unit for taking out a signal of the temple is in that frequency band, the transmission unit and the signal taken out by the filter unit
Branch supplied transmission signal and a comparator for comparing, saw including a level adjuster for adjusting the level of the output of the phase adjuster by the output of the comparison unit, from the level adjustment unit from
Output signal is added in reverse phase to the received signal received by the receiver.
And the transmission period of the communication signal is adjusted by the level adjustment.
Hold the adjustment amount in the adjusting unit and transmit the adjustment amount to the comparing unit.
During the period when the pilot signal is branched and supplied from the
Only the amount of adjustment of the output level by the level adjustment unit is varied . Further, the third device invention is a contractor.
As specified in claim 3, the transmission and reception between a plurality of
Packet data is transmitted using a Manchester-encoded communication signal.
Full-duplex two-way optical wireless communication using the same frequency band
Transmitting and receiving the communication signal.
Other transmission / reception devices within the frequency band used by the communication signal.
Pilot signal to which a single frequency different from the
Signal during the idle period between the transmission periods of each said communication signal.
And a transmission unit that transmits data from another transmission / reception device.
A receiving unit for receiving a communication signal;
The transmission signal transmitted from the transmission unit included in the received signal
A return light canceling device for removing the return light of the
The return light canceling device outputs the signal from the transmitting unit.
Light receiving element of the receiving section in order to direct RECEIVING optical light signal
Separate from the light-emitting element of the transmission unit provided near
2 light-receiving elements and a reception signal branched and supplied from the reception unit.
Frequency band assigned to the pilot signal from
Filter for extracting the signal of the band, and this filter
The extracted signal and the transmission branched from the transmission unit
A comparison unit that compares the signal and the output of the comparison unit
Level adjustment for adjusting the output level of the second light receiving element
And an output unit for receiving the output signal from the level adjustment unit.
Adding in reverse phase to the received signal received by the receiver,
During the transmission period of the communication signal, the amount of adjustment by the level adjustment unit
From the transmitter to the comparator.
Level adjustment unit only during the period when the
The amount of output level adjustment at
You.

[0010]

According to the first aspect of the present invention, a part of the transmission signal of the transmission unit is branched, and this signal is delayed by a predetermined amount by the phase adjustment unit and adjusted in phase. On the other hand, the optical signal transmitted from the transmitting / receiving device of the other party is received by the receiving unit, the filter unit extracts a test signal of a predetermined frequency band from the received signal, and this test signal is compared by the comparing unit in the transmission signal. This inspection signal is compared with a reference signal in the same frequency band to determine whether or not the suppression amount is appropriate.

[0011] According to the second apparatus invention, the transmitting section inserts a pilot signal into a non-packet section and outputs it.

On the other hand, the optical signal transmitted from the transmitting / receiving apparatus of the other party is received by the receiving unit, the filter unit extracts a pilot signal included in the received signal from the received signal, and the extracted pilot signal is converted by the comparing unit into the transmitting unit. Is compared with the pilot signal generated in step (1) to determine whether the suppression amount is appropriate. The output signal from the comparison unit is used as a control signal for the level adjustment unit, and controls the amplitude of the output signal from the phase adjustment unit. The output of this level adjuster is
The signal is inverted to become a cancel signal, which is added to the received signal from the receiving unit, and suppresses the influence of the reflected light, that is, the return light contained therein.

If the amount of adjustment in the phase adjustment unit is such that the amount of delay caused by the communication distance between the two transmission / reception devices is negligible compared to other factors, the transmission unit and the reception unit can adjust the amount of delay. What is necessary is just to set so that it may become a fixed delay amount which has a characteristic. When a separate second light receiving element, for example, a monitoring light receiving element, is provided in addition to the main light receiving means, a cancel signal is obtained based on a reception signal from the monitoring light receiving element. The control may be performed as described above.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical wireless communication transmitting / receiving apparatus according to the present invention will be described below.
It is described in detail with reference to an embodiment of the location and the returning light cancellation Way Method in the accompanying drawings. FIG. 1 is a circuit diagram showing a transmission / reception device having a first optical wireless communication return light canceling device, and FIG.
FIG. 3 is a diagram showing an output frequency spectrum of a transmission signal of two transmitting / receiving apparatuses, and FIG. 4 is a timing chart for explaining an operation of the return light canceling apparatus.

In this embodiment, a case will be described in which a transmitting / receiving apparatus for optical wireless communication is applied to AV (Audio Visual) bidirectional transmission. As shown in FIG. 2, two transmitting / receiving apparatuses A and B for optical wireless communication include transmitting sections 1A and 1B and receiving sections 2A and 2B used for optical communication and return light canceling apparatuses 3A and 3B, which are features of the present invention, respectively. The transmission / reception devices A and B are arranged so that the transmission / reception units face each other so as to transmit and receive optical signals. In this embodiment, the two devices A and B are arranged relatively close to each other, and perform communication within a distance of, for example, 1 m.

In each of the transmitting and receiving apparatuses A and B, the audio signal and the video signal are FM-modulated, added, and output. In this case, the frequencies of the FM modulated carrier signals of the audio signals of the devices A and B are, for example, 2.3 MHz and 2.8 M
Since the other parts are configured in exactly the same manner except for the point different from Hz, the configuration of one transmitting / receiving apparatus A will be described as an example. An example of the frequency spectrum of the transmission signal is shown in FIG. 3, and the video signal is commonly used in the range of 6 MHz to 20 MHz.

The transmitting section 1A comprises a first FM modulator 4A for FM modulating a video input signal, a second FM modulator 5A for FM modulating an audio input signal, and each of these modulators 4A, 5A.
It is mainly composed of an adder 6A for adding the output signal of A, and a driver 8A for driving a light emitting element 7A such as an LED by the output signal of the adder 6A.

The receiving section 2A includes a light receiving element 9A such as a photodiode for receiving an optical signal from the transmitting / receiving device B, a light receiving device 10A for converting the signal into a received signal, and the output of the light receiving element 9A. An adder 11A for adding a cancel signal and a first amplifier 1 for amplifying the output.
2A, a demodulator 13A for demodulating the output, first and second band pass filters (BPF) 20A and 21A for separating the video signal and the audio signal from the output, and a first for demodulating the output from the BPF. And the second FM demodulator 1
4A and 15A. The added signal in the transmitting section 1A, that is, the transmission signal is transmitted to the driver 8A.
Is applied to the light emitting element 7A through the
It will emit an optical signal into free space within degrees.

The transmission / reception device A performs transmission and reception at the same time. The receiving range is also set within the range of 60 degrees as in the case of transmission. The reason why the directivity is set to 60 degrees for both transmission and reception in this manner is to enable communication to be performed within a range of 60 degrees without directing the devices to each other. Here, the optical signal transmitted from the transmission / reception device B has the same band as the optical signal that has been subjected to exactly the same modulation as that of the transmission / reception device A except for the FM carrier frequency of the audio signal.

When there is no reflective object near the transmitting / receiving device A, the optical signal received by the transmitting / receiving device A is only the signal from the transmitting / receiving device B, so that high quality reception is possible.
However, when there is the reflector 16 (see FIG. 2), the optical signal from the transmitting / receiving device B and the optical reflected signal at the output of the transmitting / receiving device A are mixed and received. Since the two signals have the same band and cannot be separated, the received signal is deteriorated in quality because it must be used as a received signal while being mixed. However, this quality is degraded by the return canceling device 3A of the present invention. Deterioration can be reduced. The cancellation of the reflected light can be completely performed by adding a signal having the same amplitude in opposite phase to the received signal due to the reflection, and such a signal can be obtained based on the transmitted signal.

The return light canceling device 3A capable of canceling the light includes a phase adjusting unit 17A for adjusting the phase of the signal branched from the transmission signal of the transmitting unit 1A by an appropriate amount,
A reher adjuster for adjusting the level (amplitude) of the output, for example, a voltage-controlled attenuator 18A, an inverter 19A for inverting the output and outputting a cancel signal, and extracting a test signal in a predetermined frequency band from the received signal. A band-pass filter 22A as a filter unit, and a comparison unit, for example, a D-flip-flop (FF) 23A, which compares a reference signal in the same frequency band as the inspection signal in the transmission signal with the inspection signal and outputs a control signal. It is mainly composed of In the present embodiment, a 2.3 MHz audio signal transmitted from the transmission unit 1A is used as the reference signal. Therefore, a 2.3 MHz BPF having the same frequency is used as the BPF 22A for extracting the test signal. .

The 2.3 MHz reference signal (audio signal) is
Digitized by the binarizer 24A and D-FF23A
And the output of the BPF 22A is
After being re-amplified by the second amplifier 25A, the binarizer 26
It is digitized by A and input to the D terminal of the D-FF 23A. The output of the D-FF 23A has a resistor 27A.
And an integrator composed of a capacitor 28A, that is, a low-pass filter 29A.

Next, the operation of the present embodiment configured as described above will be described. First, in one transmission / reception device A, a video signal and an audio signal are modulated by first and second modulators 4A and 5A, respectively, and then added to each other to generate a transmission signal S1, and a driver is used by this signal. By driving 8A, an optical signal is transmitted from light emitting element 7A to another transmitting / receiving apparatus B.

Similarly, an optical signal is transmitted from the other transmitting / receiving apparatus B disposed opposite to the transmitting / receiving apparatus A, and each apparatus simultaneously performs optical transmission and optical reception. The reception signal S2 is split and divided into first and second BPFs.
Video signal and 2.8M through 20A and 21A respectively
Hz audio signal is extracted, and each signal is demodulated by the first and second demodulators 14A and 15A, respectively, to output a video,
Outputs audio.

Here, the transmission / reception apparatus A will be described as an example. A part of the optical signal transmitted from the apparatus A is reflected by, for example, a reflector 16 located in the vicinity, and is transmitted to the own reception unit 2.
A will be mixed with the received signal from the other device B. This reflected light signal is transmitted to the device A
Is propagated through a transmission path including the light emitting element 7A, the space, and the light receiving element 9A, and the received signal undergoes a phase change and an amplitude change by passing through the transmission path.

Each change amount changes depending on the reflection condition. The phase change is the sum of the phase delay due to the light emitting element 7A, the phase delay due to the light receiving element 9A, and the delay due to space travel (which can be regarded as a phase change). The phase change by the light emitting element and the light receiving element is a fixed amount irrespective of the reflection state, but the delay amount due to space travel, that is, the phase change amount changes depending on the reflection state. The amount of this change is determined by the distance of the reflection path.

Assuming that the distance of the reflection path is L (cm), the delay amount τ (ns) is expressed by the following equation. τ = L / c = 0.033 (ns) (1) where c = 3 × 10 ¹⁰ (cm / s) [speed of light] Is obtained, for example, if L is 10 cm and the carrier frequency is 10 MHz,
Since the cycle of MHz is 100 ns, the change amount is as follows. 0.033 × 10 × 360 ÷ 100 = 1.19 (degrees)

That is, at a distance of about 10 cm, the amount of phase change can be almost ignored. Accordingly, even if the phase change due to reflection is a fixed value, there is almost no error. Therefore, if a part of the transmission signal is branched and given the same fixed amount of phase change as above to make the phases opposite, the phase condition for cancellation can be satisfied.

When there is a reflection path of 10 cm or more, the change in phase cannot be ignored, but as the reflection path becomes longer, the reflection level decreases in proportion to the square of the distance. do not do. Therefore, it is possible to respond to the phase change by adjusting the fixed amount as described above. On the other hand, the amount of change in the amplitude greatly changes depending on the reflection condition. If the amplitude change amount can be detected and the amplitude of the branched transmission signal can be controlled in accordance with the reflection state, the signal can be canceled or canceled by a signal having the same amplitude in the opposite phase to the reception reflection signal.

The control of the amplitude of the cancel signal is performed as follows. The split transmission signal is supplied to the phase adjuster 17.
A gives the same phase change as the reflected reception signal to become an adjustment signal S4, which is then controlled by the voltage-controlled attenuator 18A to have substantially the same amplitude as the reflection reception signal, and then the cancellation signal via the inverting unit 19A. S7 is created and input to the adder 11A to cancel the reflected signal. The phase adjustment amount in the phase adjustment unit 17A is a fixed amount determined by the element characteristics as described above. The key to canceling the reflected signal is how to generate the control signal S3 of the voltage controlled attenuator 18A.

Next, generation of the control signal S3 will be described. The signal of the specific wavelength of the output of the adder 11A, that is, the check signal S5 of 2.3 MHz in the present embodiment, that is, the check signal S5, is amplified by the subsequent first amplifier 12A, and then input to the demodulator 13A and the BPF 22A. After removing the components other than the sound FM signal of the 2.3 MHz carrier through the second amplifier 25A, the signal is amplified again by the second amplifier 25A, and the TTL (Transistor) is output by the binarizer 26A.
r Transistor Logic) level. The obtained TTL level signal is supplied to D
-Input to the D terminal of FF23A.

On the other hand, the audio signal, that is, the reference signal S6 is input to the CK input of the D-FF 23A by the
A binarized signal is added to the level. The output of D-FF is C
An operation of holding the D level of the rising edge of the K input until the next CK rising edge is performed. The timing chart at this time is shown in FIG. 4, and FIG. 4 (B) and FIG.
FIG. 4D shows a case where the cancellation is insufficient, and FIG.
(E) shows the case of excessive cancellation. In addition, FIG.
4B, there is a delay in the pulse waveform shown in FIG.
A is due to the delay.

Now, consider the case where the canceling level of the cancel signal S7 is smaller than the reflected signal level.
As shown in (C), the output of the D-FF 23A becomes low. The D-FF output is applied as a control signal S3 of the voltage-controlled attenuator 18A via the low-pass filter 29A. The voltage control attenuator 18A outputs the control signal S3
Has a characteristic that the amount of attenuation decreases as the voltage decreases. Therefore,
Cancel signal S7 by low control signal S3
Rises and gradually approaches the level of the reflected signal, and optimal cancellation is performed.

On the other hand, when the cancellation level is excessive, the output of the D-FF 23A becomes high as shown in FIG. 4 (E), so that the level of the cancel signal S7 goes down and gradually decreases. The reflection level is approached, and optimal cancellation is performed.

In any case, if it deviates from the optimal cancel, the output of the D-FF 23A is generated so as to pull it back, so that the optimal cancel state is always maintained. Note that the output of the D-FF 23A continuously assumes high and low values when the control signal S3 is in the middle of being pulled in. However, since the output of the D-FF 23A outputs a high and low value in a fine cycle when the pull-in starts, the voltage of the control signal S3 becomes The DC (direct current) voltage of a certain level between high and low is integrated by the low-pass filter 29A.

The canceling operation of the transmitting / receiving apparatus A has been described above. The canceling operation of the other transmitting / receiving device B is performed in substantially the same manner. However, device B has a carrier of its own transmitted voice FM signal of 2.8 MHz, and
The difference is that the bandpass filter for detecting the reflected signal passes only the 2.8 MHz component.

As described above, the transmission / reception device A and the transmission / reception device B differ in the frequency of the signal for canceling the reflection, so that the signal of the other party is not canceled. As described above, the adverse effect of the reflection signal of the own transmission signal can be substantially canceled, and the communication signal of the other party can be accurately extracted. Note that the position of the reversing unit 19A is not limited to the illustrated example, and may be provided before the attenuator 18A or before the phase adjusting unit 17A. Further, in the present embodiment, the inverting unit 19A that inverts the phase of the signal to reverse the phase is provided separately from the phase adjusting unit 17A, but this phase inverting function may be included in the phase adjusting unit 17A. Of course it is good. Further, the adder 11A is replaced with a subtractor,
The phase inversion function can be omitted.

Next, the second device invention will be described with reference to FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted.
This embodiment is an example of performing bidirectional communication of packet data. The data is compliant with, for example, a wired LAN Ethernet (10 Mbps).

Communication is performed between the transmitting / receiving apparatus A and the transmitting / receiving apparatus B as shown in FIG. The transmitting / receiving device A is built in, for example, the back of the portable personal computer PC, and has a structure in which the transmitting unit 1A and the receiving unit 2A are exposed to the outside as in the case shown in FIG. On the other hand, the transmitting / receiving device B is
And is connected to a wired LAN via a terminal TR and has light transmitting and receiving units 1B and 2B. The transmitter 1A is provided with an interface 31A instead of the modulator, and the receiver 2A is also provided with an interface 31A instead of the filter or the demodulator.
A digitizer 32A and an interface 33A are provided.
Then, returning to the two devices A and B, the light canceling devices 3A and 3B
Are respectively provided. This return light canceling device is shown in FIG.
Are different from the device shown in FIG. 1 in that the band of the band-pass filter 22A is set to the frequency band of the pilot signal described later, and the open / close switch 34A that is closed only during an idle period between packets adjacent to the output side of the D-FF 23A. Is provided.

The bidirectional communication is performed by the transmitting / receiving units of the transmitting / receiving apparatus A and the transmitting / receiving apparatus B configured as described above, and the personal computer is wirelessly connected to the wired LAN. A signal flowing on the Ethernet from the personal computer and the cable is directly input to each device, and each device outputs a signal in the same form as a signal flowing on the Ethernet to the personal computer and the wire. The signal flowing on the Ethernet is, for example, Manchester-encoded packet data. As shown in FIG.
MHz.

In order to realize full-duplex two-way communication,
Generally, both signals are set to different frequency bands by means of modulation or the like, and isolation is measured. However, when a signal having a 20 MHz band is modulated as described above and frequency multiplexing is measured, the required band is widened. Too much, exceeding the response of the optical element. Therefore, the signals transmitted from the transmission / reception device A and the transmission / reception device B are made the same band as the signal flowing on the Ethernet, and full duplex two-way communication is realized by performing reflection cancellation.

The communication data is in a packet form and has a pause. Therefore, in this embodiment, the pilot signal S8 is inserted by the interface 31A during the idle period. The pilot signal S8 has a single frequency. For example, the transmitting and receiving device A has a frequency of 1 MHz, and the transmitting and receiving device B has a frequency 1.5 times that of the device A, for example, 1.5 MHz. That is, since the frequency spectrum of the Manchester code uses a wide band from 0 Hz to 20 MHz, the pilot signal cannot be superimposed on the data. Therefore, the pilot signal is added during the idle period between packets so that it can be temporally separated. ing. A transmission signal formed by inserting a pilot signal S8 between data which is a communication signal is a driver 8A
The light emitting element 7A is driven via the, and an optical signal is transmitted to the space.

The transmission and reception directional angles are set to about 60 degrees as in the case of the first device invention, so that communication can be performed regardless of how the personal computer is placed on the desk within a certain range. Since the communication distance is within the range of the desk surface, the maximum communication distance is approximately 1 m. The reception of the optical signal from the transmission / reception device B is performed by the light receiving element 9A and the light receiving device 10A to obtain the reception signal S2. The received signal S2 also includes its own reflected light as described above.

The reflection cancellation is basically the same as that of the first device invention. However, in this example, since the cancellation reference pilot signal S8 is generated in a time-division manner, the D-FF2
The output signal of 3A is supplied to the low-pass filter 29A composed of an integrating circuit only when the packet is idle, and the open / close switch 34A is opened in the packet data section to hold the voltage of the control signal S3 supplied to the voltage controlled attenuator 18A. . Here, the opening / closing control of the opening / closing switch 34A is given from the interface 31A.

As in the first device invention, the pilot signal S8 is made different between the transmitting / receiving device A and the transmitting / receiving device B to avoid canceling the signal from the other party. 1 MHz pilot signal S8
The reason for setting these to 1.5 MHz is to prevent those harmonic components from overlapping. If the frequency of the pilot signal of the other transmitting / receiving apparatus B is 2 MHz instead of 1.5 MHz, the second harmonic of 1 MHz is 2M
Hz, a cancel malfunction may occur.

The reason why the frequency of each pilot signal is set lower than that of the data signal is that the frequency of the pilot signal is set at a position where the spectrum distribution of the data signal is low, so that the frequency of the pilot signal depends on the data signal from the other party. This is for reducing the malfunction of the cancellation.

The level of the pilot signal frequency band due to the partner data signal changes depending on the communication distance, and increases as the communication distance decreases. When the communication distance is long, there is almost no problem because the interference component from the partner data is very small. On the other hand, as the communication distance becomes shorter, the interference component increases, and the canceling accuracy deteriorates. However, in this case, since the number of desired signals increases, the reception level is improved more than the deterioration of the cancellation accuracy, and as a result, there is little difference in deterioration due to reflection. Therefore, according to the present method, effective reflection cancellation can be realized from a short distance to a long distance. Note that the position of the reversing section 19A is not limited to the illustrated example, and the attenuator 18
It may be provided before A or before the phase adjustment unit 17A. Further, also in the present embodiment, the inversion unit 19A is connected to the phase adjustment unit 17.
A is provided separately from A, but this phase inversion function
Of course, it may be included in 7A. Further, the adder 11A can be replaced by a subtractor, and the phase inversion function can be omitted.

In each of the apparatus examples described above, an electric means is employed as a phase adjusting means for obtaining a cancel signal. However, in order to further enhance the cancellation effect,
The monitor circuit shown in FIG. 9 may be used. In this figure, a monitor light receiving element 36A and its light receiver 37A are arranged as a second light receiving element very close to the light emitting element 7A, and the cancel signal S is provided by exactly the same mechanism as that for receiving the reflected light.
Get 7. In this case, since the phase delay amount is included in the reception signal of the monitoring light receiving element 36A, the use of a complicated phase adjustment unit is unnecessary, or the adjustment is unnecessary. As described above, the optical signal from the light emitting element 7A is directly received by the monitoring light receiving element 36 using the monitoring light receiving element 36A, thereby enabling accurate phase adjustment. Although the device example shown in FIG. 9 shows a case where the monitoring light receiving element is provided in the device example shown in FIG. 5, the monitoring light receiving element may be provided similarly to the device example shown in FIG.

In the above embodiment, the case where the present invention is applied to a transmitting / receiving apparatus for transmitting audio / video signals or a transmitting / receiving apparatus for bidirectional communication of packet data has been described. However, the present invention is not limited to this. Such a communication system may be used.

[0050]

As described above, the transmission / reception apparatus of the present invention is used.
And according to the returned light cancel Way Method can exert effects excellent as follows. Since a part of its own transmission signal is branched and its level and phase are adjusted, this signal is inverted to form a cancellation signal and added to the reception signal, so that the signal due to reflected return light is substantially suppressed. Can be canceled. Therefore, by performing a signal canceling operation using such reflected light, full-duplex bidirectional communication using the same band can be provided at a low cost with a simple configuration. The light receiving element other than the communication light receiving element directly receives the optical signal of its own light emitting element and obtains the control signal from this signal, thereby accurately adjusting the phase (delay) of the cancel signal and improving the cancel effect. Can be enhanced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a transmission / reception device having a return light canceling device for first optical wireless communication.

FIG. 2 is a layout diagram showing a positional relationship between two transmitting / receiving apparatuses.

FIG. 3 is a diagram illustrating output frequency spectra of transmission signals of two transmission / reception devices.

FIG. 4 is a timing chart for explaining the operation of the return light canceling device.

FIG. 5 is a circuit diagram showing a transmission / reception device having a return light canceling device of the second optical wireless communication.

FIG. 6 is a layout diagram showing a positional relationship between two transmitting / receiving apparatuses.

FIG. 7 is a diagram showing a state where a pilot signal is inserted between packet data.

FIG. 8 is a diagram illustrating a frequency spectrum of a Manchester code.

FIG. 9 is a circuit configuration diagram showing a modification of the present invention.

[Explanation of symbols]

1A, 1B: transmitting section, 2A, 2B: receiving section, 3A, 3B
... return light canceling device, 7A ... light emitting element, 8A ... driver, 9A ... light receiving element, 10A ... light receiving element, 16 ... reflector
17A: phase adjustment unit, 18A: voltage control attenuator (level adjustment unit), 19A: inversion unit, 22A: band-pass filter, 23A: D-flip-flop (comparison unit), 29A
... low-pass filter, 31A ... interface, 34A
… Open / close switch, 36A… Monitor light receiving element, A, B…
Transmission / reception device, S1: transmission signal, S2: reception signal, S3 ...
Control signal, S4: adjustment signal, S5: inspection signal,
S6: Reference signal, S7: Cancel signal, S8: Pilot signal.

────────────────────────────────────────────────── ⁷ Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H04B 10/14 10/18 10/22 (56) References JP-A-58-171138 (JP, A) JP-A-62-116024 (JP, A) JP-A-5-259993 (JP, A) JP-A-7-336308 (JP, A) JP-A-7-336303 (JP, A) JP-A-7-235906 (JP, A) 63-111038 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H04B 1/76 H04B 7/005 -7/015

Claims (5)

(57) [Claims] 1. A method for transmitting packet data between a plurality of transmitting / receiving apparatuses.
Same frequency band due to Manchester coded communication signal
And a transceiver for performing full-duplex bidirectional optical wireless communication using the communication signal , wherein the communication signal is transmitted and used by the communication signal.
Sends a pilot signal in the frequency band single frequency different from the other transceiver is assigned for each said communication signal
A transmitting unit that inserts and transmits a pause period during a period, a receiving unit for receiving a communication signal transmitted from another transmitting / receiving device, and a receiving unit that is included in a received signal received by the receiving unit.
To remove the return light of the transmission signal transmitted from the transmitter
A return light canceling device, wherein the return light canceling device is branched and supplied from the transmitting unit.
Phase of the transmitted signal to be received by the receiving unit.
And phase adjuster that adjust a fixed amount in order to adjust the phase, a filter unit for taking out a signal of the frequency band allocated to the pilot signal from the received signal branching supplied from the receiving unit, the filter unit a comparing unit for comparing the transmission signal the branched supplied from the transmission unit and the signal taken out Te, saw including a level adjuster for adjusting the level of the output of the phase adjuster by the output of the comparator unit, An output signal from the level adjustment unit is received by the reception unit.
The received signal is added in reverse phase to the received signal, and the transmission of the communication signal is performed.
The outgoing period holds the adjustment amount in the level adjustment unit,
The pilot signal branches from the transmitting unit to the comparing unit.
The output level of the level adjustment unit only during the
A transmission / reception device characterized in that the amount of adjustment of the channel is variable . 2. The transmission / reception apparatus according to claim 1, wherein the phase adjustment function of the phase adjustment unit includes a phase inversion function. 3. Packet data is transmitted between a plurality of transmitting / receiving apparatuses.
Same frequency band due to Manchester coded communication signal
And a transceiver for performing full-duplex bidirectional optical wireless communication using the communication signal , wherein the communication signal is transmitted and used by the communication signal.
Sends a pilot signal in the frequency band single frequency different from the other transceiver is assigned for each said communication signal
A transmitting unit that inserts and transmits a pause period during a period, a receiving unit for receiving a communication signal transmitted from another transmitting / receiving device, and a receiving unit that is included in a received signal received by the receiving unit.
To remove the return light of the transmission signal transmitted from the transmitter
Of a return light cancellation apparatus, the return light cancellation apparatus, the receiving unit separately of the transmission unit and the light receiving element of the <br/> optical signal output from the transmitting unit in order to direct RECEIVING light A second light receiving element provided in the vicinity of the light emitting element, and a frequency band allocated to the pilot signal from a reception signal branched and supplied from the reception unit .
A filter unit for taking out a signal, a comparing unit for comparing the branch supply transmission signal <br/> from the transmitting unit and the signal taken out by the filter unit, the second by the output of the comparator unit look including a level adjuster for adjusting the level of the output of the light receiving element receives the output signal from the level controller at the receiving unit
The received signal is added in reverse phase to the received signal, and the transmission of the communication signal is performed.
The outgoing period holds the adjustment amount in the level adjustment unit,
The pilot signal branches from the transmitting unit to the comparing unit.
The output level of the level adjustment unit only during the
A transmission / reception device characterized in that the amount of adjustment of the channel is variable . 4. Packet data between another transmitting and receiving device
In the same frequency band due to Manchester-coded communication signals
Method for canceling return light in a transmitting / receiving apparatus that performs full-duplex bidirectional optical wireless communication using an area , wherein the communication signal is transmitted and used by the communication signal.
Sends a pilot signal in the frequency band single frequency different from the other transceiver is assigned for each said communication signal
A return signal is inserted in the idle period between the transmission periods and transmitted from the transmission unit, and the transmission signal branched from the transmission unit is received by the reception unit.
Ri and phase adjustment in a fixed amount in order to match the phase of light, and extracts a signal of the included in the received signal received by the receiving section the frequency band allocated to the pilot signal Ru Tei, branched from the transmission unit The pilot signal is transmitted from the transmitting unit based on the comparison result.
Adjustable output level only during signal output
Adjust the level of the phase-adjusted transmission signal while changing
Wherein the return signal is added to the received signal received by the receiving section in a reverse phase . 5. Packet data between another transmitting and receiving apparatus.
In the same frequency band due to Manchester-coded communication signals
Transmission / reception device that performs full-duplex two-way optical wireless communication using
A method for canceling a return light in a device, wherein the communication signal is transmitted and used by the communication signal.
A single frequency that is different from other
Transmitting the pilot signal assigned to each of the communication signals.
The signal is inserted into the idle period between the periods and transmitted from the transmitting unit, and is separately provided from the light emitting element of the transmitting unit separately from the light receiving element of the receiving unit.
Outgoing from the transmitting section by a second light receiving element provided beside
Directly receiving the input optical signal, and receiving the received light signal by the receiving unit.
Extract frequency band signal assigned to lot signal
And compared with the transmission signal branched and supplied from the transmission unit.
And based on the comparison result,
Adjustable output level only during signal output
Of the signal received by the second light receiving element while changing
Adjust the bell so that the received signal received by the
A method of canceling a return light , wherein the addition is performed by :