JP2004242224A - Reflected wave signal removal apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflected wave component removal apparatus in a transmission system connected by one wire cable that removes a reflected wave component in which a transmission signal from a local station reflects and is superimposed on a reception signal from a remote station. <P>SOLUTION: The reflected wave component removal apparatus in a data transmission system that transmits data simultaneously and bidirectionally over a cable 6 using the same wavelength or same frequency comprises: a transmission unit 1 for transmitting a transmission signal to the cable 6 via a branching/coupling unit 3; a reception unit 2 for performing reception via the branching/coupling unit 3; a subtraction unit 5 for removing the reflected component of reception signal from the reception signal received by the reception unit 2; and a reflected wave estimation unit 4 for seeking an estimate of the reflected wave component entering the subtraction unit 5, based on a correlation between an output signal and an input signal of the subtraction unit 5 at a plurality of timings. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reflected wave signal that transmits and receives simultaneously using an optical signal of the same wavelength, an electric signal of the same frequency, or a baseband signal through a single-core transmission line, and the transmission signal is reflected halfway and returns to the receiving side. The present invention relates to a reflected wave signal elimination device that eliminates a signal.
[0002]
[Prior art]
As a conventional transmission system, for example, a configuration shown in FIG. 9A or 9B is known. In FIG. 1A, 101 and 102 are transmitting units, 103 and 104 are receiving units, 105 and 106 are branching / coupling units, and 107 is a reflection point (X) such as a repeater or a connector. When the transmission signal wavelengths or the transmission signal frequencies of the transmission units 101 and 102 are the same, the transmission signal reflected at the reflection point (X) 107 returns as indicated by the dashed-dotted arrow, and the transmission / reception of the own station is performed. The signal is superimposed on the main signal from the partner station and input to receiving sections 103 and 104 via coupling sections 105 and 106. Therefore, when the reflection component of the transmission signal is superimposed on the reception signal, the reception error rate of the reception units 103 and 104 increases.
[0003]
Therefore, as shown in FIG. 9B, by making the transmission wavelength λ1 of the transmission unit 101 different from the transmission wavelength λ2 of the transmission unit 102, even if the light is reflected at the reflection point (X) 110, The reception error rate can be improved by inputting only the main signal from the partner station to the receiving sections 103 and 104. In addition, reference numerals 108 and 109 denote wavelength division multiplexing units (WDMs: Wavelength Division Multiplexers). The wavelength division multiplexing unit 108 transmits the main signal of the wavelength λ1 from the transmission unit 101 to the transmission line, blocks the passage of the reflected wave signal of the wavelength λ1, and receives the main signal of the wavelength λ2 from the partner station. Input to 103. Further, the wavelength division multiplexing unit 109 sends the main signal of the wavelength λ2 from the transmitting unit 102 to the transmission line, blocks the reflected wave signal of the wavelength λ2 from passing, and receives the main signal of the wavelength λ1 from the partner station. 104.
[0004]
In FIG. 9A, the relationship between the branching / coupling units 105 and 106, the transmission units 101 and 102, and the reception units 103 and 104 when using an optical signal is shown in FIG. 10, for example. Configurations can be used. In the figure, reference numeral 111 denotes a laser diode (or light emitting diode) for converting an electric signal constituting a transmitting unit into an optical signal, 112 denotes a photodiode for converting an optical signal constituting a receiving unit to an electric signal, and 113 denotes a branch. / A half mirror (or fiber fusion type branch coupler) for performing synthesis, 114 and 117 are lenses, 115 is an optical fiber constituting a transmission path, and 116 is a supporting member.
[0005]
The laser diode 111 (or light emitting diode) is driven by the transmission signal, and the main signal of the modulated optical signal is transmitted to the optical fiber 115 via the lens 114 and the half mirror 113. The optical signal received via the optical fiber 115 is incident on the photodiode 112 via the half mirror 113 and the lens 117, converted into an electric signal, and processed as a received signal.
[0006]
Also, in telephone communication, an echo canceller for improving the reception quality is known. When a voice signal from a receiver goes around a transmitter and a far-end echo is generated, an echo path is estimated and received. An echo signal for canceling the echo component is formed based on the signal, and the echo signal is subtracted from the transmission signal and transmitted. This conventional echo canceller generally estimates an echo path during a training period (for example, see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-5-176046 [0008]
[Problems to be solved by the invention]
If the wavelengths (or frequencies) of the transmission signals of the transmission units 101 and 102 in FIG. 9A are the same, the configuration of the branching / coupling units 105 and 106 is, as shown in FIG. It can be realized with a relatively simple configuration using the optical fiber 113 or the fiber fusion type branch coupler. However, due to reflection from a reflection point by a connector for connection of the optical fiber 115, a repeater, or the like, a reflected wave signal having the same wavelength (same frequency) as the transmission signal is combined with the reception signal to form the photodiodes constituting the reception units 103 and 104. It is incident on 112. Therefore, there is a problem in that an unnecessary signal is superimposed on the received signal, thereby increasing the reception error rate.
[0009]
Therefore, the influence of the reflected wave on the received signal can be reduced by making the wavelength (frequency) of the transmitted signal different like the wavelengths λ1 and λ2 of the transmitted signal in FIG. 9B. However, the configuration of the wavelength division multiplexing units 108 and 109 requires a configuration for branching and coupling corresponding to the wavelength, and there is a problem that the configuration by a filter or the like is complicated and the cost is increased. Further, since the laser diodes as the transmission units 101 and 102 need to be configured to output optical signals of different wavelengths, there is a problem that the cost is increased as compared with the configuration of outputting optical signals of the same wavelength.
[0010]
Further, the conventional echo canceller is to estimate the sneak component of the received signal and remove it from the transmitted signal when the received signal wraps around the transmission signal and is superimposed to become an unclear sound signal on the receiving side. It does not solve the problem that the reception error rate increases due to reflection on the transmission path and superimposition on the received signal, and also estimates the echo path during the training period and the like. In some cases, the echo cancel value cannot be controlled.
[0011]
The present invention solves the above-mentioned conventional problems. When data is transmitted and received simultaneously using signals of the same wavelength (the same frequency or baseband) using a single transmission line, the present invention is applied to the case where The transmitted signal of the station is reflected by each unit including the own station, and the reflected wave component superimposed on the received signal from the partner station is estimated, and the reflected wave component is canceled based on the estimated value to improve the reception error rate. The purpose is to:
[0012]
[Means for Solving the Problems]
Referring to FIG. 1, the reflected wave signal removing apparatus of the present invention transmits an optical signal of the same wavelength or an electric signal of the same frequency (or baseband signal) simultaneously and bidirectionally through the same cable 6. A reflected wave removing device in a data transmission system, which transmits a transmission signal to a cable 6 via a branch / coupling unit 3 and receives the transmission signal from the cable 6 via the branch / coupling unit 3. A receiver 2 and a reflected wave estimator 4 for obtaining an estimated value of a reflected wave component in accordance with a correlation with the transmitted signal based on a signal obtained by subtracting an estimated value of the reflected wave component of the transmitted signal from the signal received by the receiver 2. The subtraction unit 5 can subtract the estimated value of the reflected wave component from the signal received by the reception unit 2.
[0013]
The reflected wave estimating unit 4 includes an intersymbol interference polarity detecting unit that detects an intersymbol interference polarity based on a signal obtained by subtracting an estimated value of a reflected wave component from a signal received by the receiving unit 2, and a delay circuit that delays a transmission signal. A correlator for obtaining a correlation between the delayed transmission signal by the delay circuit and the detection signal by the intersymbol interference polarity detection unit; an integrator for integrating a correlation output signal of the correlator; and an integrated output signal of the integrator. , An amplitude controller for controlling the level of the delayed transmission signal, and means for subtracting the output signal of the amplitude controller as an estimated value of the reflected wave component from the signal received by the receiver.
[0014]
The reflected wave estimating unit 4 detects an intersymbol interference based on a signal obtained by subtracting the estimated value of the reflected wave component from the signal received by the receiving unit 2, and writes and receives the transmitted signal in accordance with the transmission clock. An elastic memory for reading by a clock, a delay circuit for delaying a transmission signal according to a reception clock, a correlator for obtaining a correlation between a delayed transmission signal by the delay circuit and a detection signal by an intersymbol interference detection unit, An integrator that integrates the correlation output signal; an amplitude controller that controls the level of the delayed transmission signal based on the integrated output signal of the integrator; and a receiving unit that uses the output signal of the amplitude controller as an estimated value of the reflected wave component. Means for subtracting from the received signal of
[0015]
Further, a delay circuit that inputs a transmission signal and a transmission clock to be input to the elastic memory, delays the transmission signal according to the transmission clock, and inputs the transmission signal to the transmission unit 1 can be provided. The reflected wave estimating unit 4 has an adder for adding the output signal of the amplitude controller and outputting an estimated value of the reflected wave component. Can be configured to have a subtractor 5 for subtracting.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a view for explaining the principle of the present invention, wherein 1 is a transmitting section, 2 is a receiving section, 3 is a branching / combining section, 4 is a reflected wave estimating section, 5 is a subtracting section, and 6 is a cable. The other station is connected via a cable 6 and transmits and receives data using the cable 6, and various network configurations can be applied. The cable 6 is a single-core optical fiber when transmitting and receiving data using optical signals of the same wavelength, and when transmitting and receiving data using electric signals of the same frequency and transmitting and receiving baseband signals. For example, a coaxial cable or a pair cable used in a LAN (local area network) or the like can be used.
[0017]
The transmitting unit 1 and the receiving unit 2 have a function of processing signals of the same wavelength (same frequency, baseband). For example, when data is transmitted and received using an optical signal, the transmitting unit 1 in the opposing device connected by a single cable 6 of a single-core optical fiber uses a laser diode or a light emitting device that generates an optical signal of the same wavelength. It is composed of a light emitting element such as a diode. Therefore, since the transmission unit 1 and the reception unit 2 in each transmission device can use light emitting elements such as laser diodes or light emitting diodes that generate optical signals of the same wavelength with the same configuration, cost can be reduced. .
[0018]
Further, the transmission signal from the transmission unit 1 is reflected by the branching / coupling unit 3, the connector, the repeater, etc., and returns to the reception unit 2 side. Since transmission and reception are performed simultaneously by a single cable 6, the reflected wave component of the transmission signal is superimposed on the reception signal and input to the reception unit 2. When data is transmitted and received using an optical signal, the receiving unit 2 has a configuration including a light receiving element such as a photodiode.
[0019]
The above-mentioned reflected wave component is estimated by the reflected wave estimating unit 4, the estimated value of the reflected wave component obtained by the reflected wave estimating unit 4 is subtracted from the received signal, and the reflected wave component superimposed on the received signal is removed. . Thereby, the reception error rate can be reduced. Also, the subtraction unit 5 shows a case where the estimated values of the reflected wave components obtained by the reflected wave estimation unit 4 are combined and subtracted from the signal received by the reception unit 2. The configuration may be such that the estimated value of the reflected wave component obtained corresponding to time is sequentially subtracted from the signal received by the receiving unit 2.
[0020]
FIG. 2 is an explanatory diagram of the first embodiment of the present invention, in which 11 indicates a transmitting unit, 12 indicates a receiving unit, 13 indicates a branching / combining unit, 14 indicates a receiving processing unit, and 15 indicates a subtracting unit. The transmitting unit 1 corresponds to the transmitting unit 11, the receiving unit 2 corresponds to the receiving unit 12, the branching / combining unit 3 corresponds to the branching / coupling unit 13, and the subtracting unit 5 corresponds to the subtracting unit 15. Also, the reception processing unit 14 has a function of processing a signal obtained by subtracting the estimated value of the reflected wave component in the subtraction unit 15 from the signal received by the reception unit 12 to reproduce a reception clock and data. . The 17 _adders, 18 1 ~ 18 _n are delay _circuits, 19 1 ~ 19 _{n correlator,} 20 1 to 20 _{n integrator,} 21 1 through 21 _n is the amplitude controller 22 is intersymbol interference polarity detection 1 and corresponds to the configuration of the reflected wave estimation unit 4 in FIG.
[0021]
The transmitting unit 11 and the receiving unit 12 have a configuration for simultaneously transmitting and receiving signals of the same wavelength (the same frequency or baseband), and a transmission signal from the transmitting unit 11 is transmitted via a branching / coupling unit 13 via a cable. The signal received through the cable is branched by the branching / coupling unit 13 and input to the receiving unit 12. When transmitting and receiving via a cable by an optical signal, the transmission unit 11 includes a light emitting element such as a laser diode or a light emitting diode, converts the transmission signal into an optical signal by the light emitting element, and outputs the converted signal via the branching / coupling unit 13. It is sent out to a cable consisting of optical fibers. The receiving section 12 includes a light receiving element such as a photodiode. The light receiving element of the receiving section 12 converts an optical signal into an electric signal, performs amplification and equalization, and inputs the signal to the subtracting section 15. In the case of transmission and reception using electric signals, the signal of the modulation frequency in the transmission unit 11 and the signal of the demodulation frequency in the reception unit 12 are the same frequency or baseband signal.
[0022]
The reception processing unit 14 has functions such as clock timing extraction and data identification. The delay circuit 18 ₁ ~ 18 _n may be or flip flops for sequentially delaying transmission signals in accordance with a transmission clock or receive clock, a configuration in which cascaded other delay elements. The delay circuits 18 ₁ to 18 _n sequentially convert the delayed transmission signals obtained by sequentially delaying the transmission signals and the detection signals from the intersymbol interference polarity detection unit 22 into correlators 19 _{1 to} 19 _n corresponding to the delayed transmission signals. to enter the correlation values, respectively, the correlation value from the correlator ₁₉ 1 ~ 19 _n is input to the integrator ₂₀ 1 to 20 _n, based on an output signal from the integrator ₂₀ 1 to 20 _n, the delay circuit the amplitude of 18 ₁ delayed transmission signal by ~ 18 _n, respectively controlled by the amplitude controller ₂₁ 1 through 21 _n, are added by adders 17, the estimated value of the reflected wave component to be input to the subtraction unit 15. In this case, the adder 17 adds the estimated value of the reflected wave component of the delayed transmission signal corresponding from the amplitude controller 21 ₁ through 21 _n, the case of subtraction collectively from the received signal at the subtraction unit 15 Show. It is also possible to adopt a configuration where the estimated value of the reflected wave component of the delayed transmission signal corresponding from the amplitude controller 21 ₁ through 21 _n, respectively subtracted separately from the received signal by the receiver 12.
[0023]
Therefore, the reception processing unit 14 receives the reception signal in which the reflection wave component according to the estimated value of the reflection component is removed from the reception signal on which the reflection wave component of the transmission signal is superimposed, and receives the reception data. It can be restored without errors. By reflected wave components are removed also, intersymbol interference polarity detection unit 22 is comprised to determine the polarity of the inter-symbol interference, an integrator 20 ₁ to 20 _n, before the no intersymbol interference Since the correlation value is maintained, the estimated value of the reflected wave component from the adder 17 can be continuously output. Therefore, the reflected wave component can be continuously removed. Note that by the reflected wave component is small, if the intersymbol interference is almost no correlation value becomes a value close to 0, from a value close to the amplitude controller 21 ₁ through 21 _n output signal almost zero, summing The estimated value of the reflection component from the detector 17 is almost zero.
[0024]
The intersymbol interference polarity detection unit 22 may have, for example, the configuration shown in FIG. In the figure, FF1 to FF3 indicate flip-flops, G1 and G2 indicate AND circuits, and G3 and G4 indicate OR circuits.
[0025]
The output signal of the subtraction unit 15 is input to the data terminals D of the flip-flops F1 to F3, and a clock synchronized with the data is input to the clock terminal C. "1" of the flip-flops F1 to F3 corresponds to the output terminal Q, and "0" corresponds to the inverted output terminal * Q. The level of the set condition of each of the flip-flops F1 to F3 is set by a reference voltage or the like (not shown) corresponding to the identification levels H, C, and L of the eye pattern in FIG.
[0026]
When the output signal obtained by subtracting the estimated value of the reflected wave component from the received signal by the subtractor 15 exceeds the identification level H, the output terminals 1 of the flip-flops F1 to F3 all become “1” (high level), The intersymbol interference detection signal of the output signal of the OR circuit G3 becomes “1” indicating that the intersymbol interference is positive, for example, and the * intersymbol interference signal of the output signal of the OR circuit G4 is that the intersymbol interference is positive, for example. "0" (low level). When the output signal of the subtraction unit 15 is equal to or lower than the discrimination level H but exceeds the discrimination levels C and L, the output terminals 1 of the flip-flops F2 and F3 become "1", and the output terminal of the flip-flop F1. 1 becomes "0". Therefore, the inter-symbol interference signal of the output signal of the OR circuit G3 is "0", indicating that the intersymbol interference is negative, and the * intersymbol interference signal of the output signal of the OR circuit G4 is "1". This indicates that the intersymbol interference is negative.
[0027]
If the output signal of the subtraction unit 15 is equal to or lower than the discrimination level C and exceeds the discrimination level L, the output terminal 1 of the flip-flop F3 becomes "1", and the output terminals 1 of the flip-flops F1 and F2 become "0". Become. Therefore, the inter-symbol interference signal of the output signal of the OR circuit G3 is “1”, indicating that the intersymbol interference is positive, and the * intersymbol interference signal of the output signal of the OR circuit G4 is “0”, This indicates that the intersymbol interference is negative. Therefore, in the eye pattern shown in FIG. 4, when the received signal level exceeds the discrimination level H and when the reception signal level is between the discrimination levels C and L, the intersymbol interference indicates a positive polarity. It becomes “1”. Similarly, when the received signal level is between the discrimination levels H and C and when the received signal level is equal to or lower than the discrimination level L, the value becomes “0” indicating that the intersymbol interference has a negative polarity.
[0028]
Figure 5 shows an example of in-correlator ₁₉ 1 ~ 19 _n and the integrator ₂₀ 1 to 20 _n in FIG. 2, EX-NOR constitutes the correlator ₁₉ 1 ~ 19 _n exclusive NOR circuit , R1 and C1 denotes a resistor and a capacitor constituting the integrator ₂₀ 1 to 20 _n, OUT denotes an output signal.
[0029]
Exclusive inversion forming the correlators 19 _{1 to} 19 _n by using the delayed transmission signals delayed by the delay circuits 18 ₁ to 18 _{n in} FIG. 2 and the intersymbol interference from the intersymbol interference polarity detection unit 22, respectively. Input to the OR circuit EX-NOR. The output signal of the exclusive-OR circuit EX-NOR is output when the correlation between the delayed transmission signal and the intersymbol interference detection signal is large, that is, when both the delayed transmission signal and the intersymbol interference detection signal are “1” or “ In the case of "0", it becomes "1", and when the correlation is small, it becomes "0". Then, integrated by a resistor R1 and the capacitor C1 constituting the integrator ₂₀ 1 to 20 _n. Therefore, when the correlation between the delayed transmission signal and the intersymbol interference detection signal is large, the level of the integrated output signal OUT increases.
[0030]
In FIG. 6 (A), (B) shows an example of a in the amplitude controller ₂₁ 1 through 21 _n in FIG. 2, R4～R12 resistance, Q1 to Q6 are _{transistors, V REF} denotes a reference voltage. 5A, a delayed transmission signal is input to the base of a transistor Q1, a reference voltage V _REF is applied to the base of a transistor Q2, and the output signal OUT of the integrator shown in FIG. And an output signal whose amplitude is controlled is transmitted from the collector of the transistor Q2.
[0031]
In FIG. 6B, a delayed transmission signal is applied to the bases of transistors Q1 and Q4, and a reference voltage V _REF is applied to the bases of transistors Q2 and Q5. For example, the intersymbol interference signal from the OR circuit G3 is applied as OUT1 to the base of the transistor Q3, the * intersymbol interference signal from the OR circuit G4 is applied as OUT2 to the base of the transistor Q6, and the collectors of the transistors Q2 and Q4 An output signal whose amplitude is controlled is transmitted.
[0032]
When the output signal OUT of the correlator increases due to the large correlation between the delayed transmission signal and the intersymbol interference detection signal, the current flowing through the transistor Q3 increases, and the output signal amplitude for the delayed transmission signal increases. When the output signal OUT of the correlator becomes low due to the small correlation, the current flowing through the transistor Q3 decreases, and the output signal amplitude with respect to the delayed transmission signal decreases. Therefore, assuming that the estimated value of the reflected wave component is an amplitude according to the correlation value between the delayed transmission signal and the intersymbol interference detection signal, for example, the adder 17 of FIG. The reflected wave component superimposed on the received signal can be canceled by the addition and subtraction from the received signal in the subtracting section 15.
[0033]
Similarly, in FIG. 6B, an output signal whose amplitude is controlled can be transmitted in accordance with the polarity of the intersymbol interference. By connecting the configurations of FIGS. 5 and 7 described above, an estimated value of the reflected wave component can be obtained based on the intersymbol interference polarity detection signal and the delayed transmission signal.
[0034]
FIG. 7 is an explanatory diagram of the second embodiment of the present invention. The same reference numerals as in FIG. 2 indicate the same parts, 31 is an intersymbol interference detection unit, 32 is an elastic memory, CK1 is a transmission clock, and CK2 is Indicates the receiving clock. Note that the intersymbol interference detection unit 31 corresponds to the intersymbol interference polarity detection unit 22 in FIG. The reception processing unit 14, a reception clock CK2 is extracted by the function of the receive clock timing extraction, inputs the receive clock CK2 and ISI 31, a delay circuit ₁₈ 1 ~ 18 _n, to the Elastic Tech memory 32 I do. Elastic Tech memory 32 writes transmission data in accordance with a transmission clock CK1, is sequentially delayed by the delay circuit ₁₈ 1 ~ 18 _n is read according to the received clock CLK2 and delayed transmission signal.
[0035]
The calculation processing function of the estimated value of the reflected wave component includes a delay circuit ₁₈ 1 ~ 18 _n correlator ₁₉ 1 ~ 19 _n integrators ₂₀ 1 to 20 _n and the amplitude controller ₂₁ 1 through 21 _n and an adder 17 Is the same as that of each of the above-described embodiments, and the configuration of each of the above-described units can be applied.
[0036]
In this embodiment, the correlation between the intersymbol interference detection signal synchronized with the reception clock CK2 and the delayed transmission signal synchronized with the reception clock CK2 can be obtained by the correlators 18 ₁ to 18 _n. . Therefore, the estimated value of the reflected wave component at the data identification timing can be obtained, and the reflected wave component superimposed on the received signal can be removed by the subtraction unit 14, so that the data identification error can be reduced. . Also in this embodiment, instead of the configuration for inputting the added output signal of the adder 17 to the subtraction unit 14, the estimated value of the reflected wave component from the amplitude controller 21 ₁ through 21 _n, by the receiver 12 It is also possible to adopt a configuration for subtracting from the received output signal.
[0037]
FIG. 8 is an explanatory view of the third embodiment of the present invention. The same reference numerals as those in FIGS. 2 and 7 denote the same parts, and 33 denotes a delay circuit. The delay circuit 33 delays a transmission signal according to the transmission clock CK1. When the transmission signal is reflected in the branching / coupling unit 13 or in a short time, the estimated value of the reflected wave component is obtained with a delay by the delay by the elastic memory 32, and it becomes difficult to remove the reflected component. . Therefore, by delaying the transmission signal input to the transmission unit 11 by the delay circuit 33, it is possible to obtain an estimated value for the reflected wave component reflected in a short time via the branching / coupling unit 13. Note that, in this embodiment as well, the configuration of each unit described above can be applied, and redundant description will be omitted.
[0038]
【The invention's effect】
As described above, according to the present invention, the transmission devices facing each other have the same configuration and are connected by a single-core cable, and the transmission signal from the transmission unit 1 of the transmission device itself is transmitted as the reflected wave signal from the connection unit or the like. When the signal is superimposed on the received signal from the device and input to the receiving unit 2 via the branching / combining unit 3 of the own transmission device, the reflected wave estimating unit 4 determines the correlation between the output signal of the subtracting unit 5 and the transmission signal. The estimated value of the reflected wave component is obtained based on the signal, and the estimated value of the reflected wave component is subtracted from the signal received by the receiving unit 2. Thereby, the reflected wave component superimposed on the received signal can be canceled. Therefore, the transmission unit 1 and the reception unit 2 in the opposite transmission device are configured to process signals of the same wavelength (or the same frequency or baseband), and cost reduction can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the principle of the present invention.
FIG. 2 is an explanatory diagram of the first embodiment of the present invention.
FIG. 3 is an explanatory diagram of an intersymbol interference detection unit.
FIG. 4 is an explanatory diagram of intersymbol interference polarity detection.
FIG. 5 is an explanatory diagram of a correlator and an integrator.
FIG. 6 is an explanatory diagram of an amplitude controller.
FIG. 7 is an explanatory diagram of a second embodiment of the present invention.
FIG. 8 is an explanatory diagram of a third embodiment of the present invention.
FIG. 9 is an explanatory diagram of a transmission system.
FIG. 10 is an explanatory diagram of a branch / coupling unit.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 transmission unit 2 reception unit 3 branching / combining unit 4 reflected wave estimating unit 5 subtractor 6 cable 11 transmission unit 12 receiving unit 13 branching / combining unit 14 reception processing unit 15 subtraction unit 17 adders 18 ₁ to 18 _n delay circuit 19 ₁ ~ 19 _n correlators ₂₀ 1 to 20 _n integrators ₂₁ 1 through 21 _n amplitude controller 22 intersymbol interference polarity detection unit

Claims (5)

In a reflected wave eliminator in a data transmission system for transmitting data at the same wavelength or the same frequency in both directions simultaneously by the same cable,
A transmission unit for transmitting a transmission signal to the cable via a branch / coupling unit;
A receiving unit for receiving via the branching / coupling unit;
A reflected wave estimating unit for obtaining an estimated value of the reflected wave component according to a correlation with the transmission signal based on a signal obtained by subtracting an estimated value of the reflected wave component of the transmission signal from a signal received by the receiving unit. A reflected wave signal removing apparatus characterized by the above-mentioned. The reflected wave estimating unit detects intersymbol interference polarity detection based on a signal obtained by subtracting an estimated value of a reflected wave component of a transmission signal from a reception signal of the reception unit, based on a signal obtained by subtracting an estimated value of a reflected wave of the transmission signal. , A delay circuit for delaying the transmission signal, a correlator for calculating a correlation between the delayed transmission signal by the delay circuit and a detection signal by the intersymbol interference polarity detection unit, and integrating a correlation output signal of the correlator. An amplitude controller for controlling the level of the delayed transmission signal based on the integrated output signal of the integrator; and subtracting the output signal of the amplitude controller from the signal received by the receiver as an estimated value of the reflected wave component. 2. The reflected wave signal removing apparatus according to claim 1, further comprising: The reflected wave estimating unit detects an intersymbol interference caused by a reflected wave of the transmission signal at a timing of a reception clock extracted from a signal obtained by subtracting an estimated value of a reflected wave component of the transmission signal from a reception signal of the reception unit. An interference detection unit, an elastic memory that writes the transmission signal according to a transmission clock and reads the transmission signal according to the reception clock, a delay circuit that delays the transmission signal according to the reception clock, a delay circuit between the delay transmission signal and the code A correlator for obtaining a correlation with a signal detected by the interference detector, an integrator for integrating a correlation output signal of the correlator, and an amplitude controller for controlling a level of the delayed transmission signal by an integrated output signal of the integrator. Means for subtracting the output signal of the amplitude controller as an estimated value of the reflected wave component from the signal received by the receiving section. Reflected wave signal removing apparatus according to claim 1, wherein. 5. A delay circuit that receives the transmission signal and the transmission clock input to the elastic memory, delays the transmission signal according to the transmission clock, and inputs the delayed signal to the transmission unit. The reflected wave signal removing device according to claim 1. The reflected wave estimating unit includes an adder that adds an output signal of the amplitude controller and outputs an estimated value of a reflected wave component, and estimates an emission component of the reflected wave component by the adder from a signal received by the receiving unit. The reflected wave signal removing apparatus according to any one of claims 1 to 5, further comprising a subtractor for subtracting the signal.

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