KR102623191B1 - Echo canceller for asymmetric full-duplex transceiver - Google Patents

Abstract

The echo cancellation circuit for asymmetric full-duplex signal transmission and reception includes a transceiver in which a transmitter that transmits a first frequency band signal and a receiver that receives a second frequency band signal are connected to a common connection pin. In the circuit, the transmitter includes a waveform adjustment unit that converts transmission data into an analog signal to generate a transmission signal and adjusts the waveform of the transmission signal, and the receiver includes an ADC that converts the analog signal and outputs a digital signal; and a subtractor for subtracting profile data from the digital signal output from the ADC. It includes, and the profile data is characterized in that it is data of a digital signal output from the ADC in the absence of the second frequency band signal.

Description

Echo cancellation circuit for asymmetric full-duplex signal transmission and reception {Echo canceller for asymmetric full-duplex transceiver}

The present invention relates to an echo cancellation circuit for asymmetric full duplex signal transmission and reception.

FIG. 1 is a diagram for explaining a conventional two-way data transmission device, FIG. 2 is a diagram for explaining a conventional echo cancellation principle, and FIG. 3 is a diagram for explaining a transmission signal, leakage signal, and reception signal in a conventional transceiver. It is a drawing. (Figure 1 is cited from Non-Patent Document 1 and Figure 2 is cited from Non-Patent Document 2)

Referring to Figure 1, the method of transmitting data in two directions (Bidirectional or Duplex) using one transmission line (two transmission lines in the case of differential signals) is widely used in various interfaces such as Ethernet because it can reduce the number of transmission lines. there is. Here, bidirectional data transmission is divided into a half-duplex method that divides time and transmits in one direction at a time for each section, and a full-duplex method that supports two-way transmission at the same time. In the full duplex method, the signal currently being transmitted and the signal being received are combined at the input terminal, so the signal being transmitted (Echo: a signal returning to the receiving terminal among the transmitted signals) is canceled and only the signal that is desired to be received is received. A residual echo cancellation circuit is required. In this way, in order to prevent self-interference from the transmitting signal to the receiving end, a hybrid circuit can be provided as an echo cancellation circuit. An ideal hybrid circuit sends the transmitted signal only to the receiving end on the distal side (far-end), does not transmit the signal to the receiving end on the proximal side, and transmits the signal received from the distal side to the receiving end on the proximal side. do. At this time, it is essential to remove the signal leaking directly from the proximal transmitting end to the proximal receiving end to prevent transmission errors.

The hybrid circuit can be implemented with passive elements outside the chip, such as a transformer using magnetic coupling, as illustrated in (a) of FIG. 2, but it is preferable to be formed inside the transmitting and receiving IC for reasons such as cost and size. A hybrid circuit composed of active elements removes the transmission signal from the signal loaded on the input/output terminal using a replica transmission circuit, or amplifies and subtracts the input/output current, as illustrated in Figure 2 (b) and (c). There was an R-gm type circuit that did this.

Referring to FIG. 3, in the case of an asymmetric method in which the frequency bandwidth of the transmitted and received signal differs depending on the direction, the transmitted signal and the received signal can be separated using a filter. At this time, even if a replica transmission circuit is used, if it is not accurately removed from the subtractor and the spectrum of the transmission signal exists within the passband of the band pass filter (BPF), leakage of the residual signal passing through the BPF and being transmitted to the receiving end A signal occurs.

Therefore, in an asymmetric full duplex circuit, there is a need to develop an input/output interface circuit that can solve the self-interference problem without using a replica transmission circuit.

The above-mentioned background technology is technical information that the inventor possessed for deriving the present invention or acquired in the process of deriving the present invention, and cannot necessarily be said to be known art disclosed to the general public before filing the application for the present invention.

<Patent Document 1> US 08315378 B2

<Non-patent Document 1> Goyal, Sandeep; Parulekar, Ganpat Anant; Gupta, Shalabh (2021): A True Full-Duplex IO (TFD-IO) with Background SI Cancellation for High-Density Interfaces. TechRxiv. Preprint. <Non-patent Document 2> Y. Tomita, H. Tamura, M. Kibune, J. Ogawa, K. Gotoh and T. Kuroda, “A 20-Gb/s Simultaneous Bidirectional Transceiver Using a Resistor-Transconductor Hybrid in 0.11- $ \mu{\hbox {m}}$ CMOS," in IEEE Journal of Solid-State Circuits, vol. 42, no. 3, pp. 627-636, March 2007, doi: 10.1109/JSSC.2006.891719.

One aspect of the present invention can provide an echo cancellation circuit for asymmetric full duplex signal transmission and reception that can reduce self-interference errors without using a replica transmission circuit in an asymmetric full duplex circuit.

The echo cancellation circuit for asymmetric full-duplex signal transmission and reception according to an embodiment of the present invention, which was created to achieve the above problem, has a common transmitter for transmitting a first frequency band signal and a receiver for receiving a second frequency band signal. In the echo cancellation circuit for asymmetric full duplex signal transmission and reception including a transceiver connected to a connection pin, the transmitter converts transmission data into an analog signal to generate a transmission signal, and includes a waveform adjustment unit for adjusting the waveform of the transmission signal; , the receiver includes an ADC that converts the analog signal and outputs a digital signal; and a subtractor for subtracting profile data from the digital signal output from the ADC. It includes, and the profile data is characterized in that it is data of a digital signal output from the ADC in the absence of the second frequency band signal.

At this time, it is preferable that the waveform adjustment unit adjusts the waveform of the transmission signal so that the rate of change of the signal value per unit time is reduced.

In addition, the first frequency band signal is a signal of a lower frequency band than the second frequency band signal, and the receiver includes a filter that passes signals higher than the minimum frequency of the second frequency band among the signals input to the receiver. More may be included.

In addition, the waveform adjustment unit is configured to provide a first section in which the rate of change of the signal value per unit time of the transmission signal gradually increases, a third section in which the rate of change of the signal value per unit time gradually decreases, and the first section and the second section. The waveform of the transmission signal can be adjusted to include a second section corresponding to the section.

Additionally, the waveform adjustment unit may include a multi-bit DAC.

In addition, the waveform adjustment unit includes a plurality of delay elements and a plurality of DACs, and each of the plurality of DACs can output a signal delayed by the plurality of delay elements to form a stepped transmission signal.

Additionally, at least some of the plurality of delay elements and the plurality of DACs may be implemented as variable elements.

In addition, the transmitter further includes an analysis unit that analyzes the ADC output signal and an adjustment command generator that generates an adjustment command to control the waveform adjustment unit, wherein the adjustment command allows the waveform adjustment unit to adjust the waveform of the transmission signal. You can modify the waveform value adjustment variable used to do this.

According to one embodiment of the present invention, in an asymmetric full duplex circuit, a useful effect is provided in that self-interference errors can be reduced without using a replica transmission circuit.

1 is a diagram for explaining a conventional two-way data transmission device,
Figure 2 is a diagram for explaining the conventional echo cancellation principle,
Figure 3 is a diagram for explaining the transmission signal, leakage signal, and reception signal in a conventional transceiver;
Figure 4 is a diagram for explaining an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention;
Figure 5 is a block diagram schematically illustrating an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention;
Figure 6 is a diagram for identifying the position of a signal in a conventional transceiver and an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention;
Figure 7 is a diagram for explaining the waveform adjustment unit of the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention;
Figure 8 is a diagram for explaining the signal waveform of the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention;
Figure 9 is a diagram to explain the difference in error depending on the slope of the signal,
Figure 10 is a diagram for explaining the signal waveform of an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to another embodiment of the present invention;
Figure 11 is a diagram for explaining the process of storing a profile and waveform in an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. Here, the same symbols are used for the same components, and repetitive descriptions and detailed descriptions of known functions and configurations that may unnecessarily obscure the gist of the invention are omitted. Embodiments of the invention are provided to more completely explain the invention to those skilled in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Figure 4 is a diagram illustrating an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention, and Figure 5 is a diagram illustrating an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention. It is a block diagram schematically illustrating, Figure 6 is a diagram for identifying the position of the signal in the conventional transceiver 1 and the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention, and Figure 7 is It is a diagram for explaining the waveform adjustment unit 111 of the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention, and Figure 8 is an echo for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention. This is a diagram for explaining the signal waveform of the removal circuit ((a) is the signal waveform at position ① in Figure 6, (b) is the signal waveform at position ② in Figure 6, and (c) is at position ③ in Figure 6. (signal waveform of), FIG. 9 is a diagram for explaining the difference in error according to the slope of the signal, and FIG. 10 is a diagram for explaining the signal waveform of the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to another embodiment of the present invention. ((a) is the signal waveform at position ① in FIG. 6, (b) is the signal waveform at position ② in FIG. 6, (c) is the signal waveform at position ③ in FIG. 6), and FIG. This is a diagram to explain the process of storing a profile and waveform in an echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention.

Referring to the drawing, the transceiver 1 includes a transmitter 11 and a receiver 12, and the transmitter 11 and the receiver 12 are connected to the transmission line 2 through a common connection pin 13. A distal transceiver (3) may be connected to the other side of the transmission line (2).

In the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention, the transmission signal transmitted from the transceiver (1) uses the first frequency band, and the distal transceiver (3) transmits it to the transceiver (1). The reception signal received from uses the second frequency band. As an example, the transmission signal may be a signal requiring a transmission speed of 100Mbps, and the reception signal may be a signal requiring a transmission speed of 4Gbps. In order to quickly transmit relatively large amounts of data, such as video data captured by a camera, it is advantageous to utilize a high-frequency band. On the other hand, signals that transmit relatively low-capacity data, such as camera control signals, do not need to use high-frequency bands and can use low-frequency bands. In this case, a transmission rate of 4Gbps can be applied to the image data captured by the camera, and a transmission rate of 100Mbps can be applied to the signal for camera control.

In one embodiment, the transmitter 11 may include a waveform adjuster 111, and the receiver 12 may include an ADC 121 and a subtractor 122. Furthermore, the transmitter 11 may further include a serializer 113, a buffer 112, etc., and the receiver 12 may further include a filter 123, etc.

The waveform adjustment unit 111 performs the function of adjusting the waveform of the transmission signal. In Figure 8, a typical conventional transmission waveform is indicated by SP, and a transmission waveform whose waveform has been adjusted according to an embodiment of the present invention is indicated by S.

In one embodiment, the waveform adjustment unit 111 may adjust the waveform of the transmission signal so that the rate of change of the signal value per unit time is reduced. In other words, the slope of the transmission waveform S illustrated in FIG. 8 can be made smaller than the slope of the conventional transmission waveform SP.

If the waveform of the transmission signal is adjusted as illustrated in FIG. 8, self-interference error can be reduced even without a low-pass filter (LPF) on the transmission side.

As illustrated in (b) of FIG. 8, SP, which is a conventional transmission waveform, has the shape of an RC delay through LPF, and S, which is a transmission waveform according to an embodiment of the present invention, has already had its high-frequency components removed to some extent. , there is no need to use LPF. Additionally, this allows more precise control of the transmission waveform.

In addition, when the transmission signal S passes through the filter 123, as illustrated in (c) of FIG. 8, the low-frequency component is prevented from passing, and only the waveform with the DC component removed remains. In addition, SP, which is a conventional transmission waveform, has a larger slope than the transmission waveform S, so it shows a waveform with a large maximum value even after passing through the filter 123, but the maximum value of the transmission waveform S is significantly reduced.

In one embodiment, the serializer 113 may perform the function of receiving multiple parallel signals and converting them into high-speed serial signals.

In one embodiment, the ADC 121 converts the received signal, which is an analog signal, into a digital signal and outputs it, and may allow the received signal to pass through the filter 123 to reach the ADC 121. Here, the filter 123 may be implemented as a high-pass filter (HPF) or a band-pass filter (BPF). This filter 123 is designed to accurately receive the transmission signal in the second frequency band transmitted by the distal transceiver 3, and can alleviate problems caused by self-interference by only passing signals above the minimum frequency of the second frequency band. there is.

Referring to FIG. 7, the waveform adjustment unit 111 may be implemented as a multi-bit DAC 1111 as illustrated in (a) of FIG. 7. The multi-bit DAC 1111 can generate a transmission signal with a waveform such as the transmission waveform S illustrated in FIG. 8 by time-division detecting and outputting the input data signal.

In another embodiment, the multi-bit DAC 1111 may adjust the waveform of the transmission signal as illustrated in FIG. 10 by adjusting the time division detection interval and amplification rate of the data signal. If the time section is divided into the first section (P1), the second section (P2), the third section (P3), and the fourth section (P4), then in the first section (P1), the slope of the signal waveform is as high as possible. You can make it smaller. However, if the slope of the first section P1 is excessively lowered, a problem may occur in which the maximum value of the signal cannot be reached within the unit time of signal transmission, so the slope of the signal waveform can be gradually increased. Additionally, in the third section P3, the slope of the signal waveform may be gradually reduced. In addition, in the second section P2 that exists between the first section P1 and the third section P3, the slope of the signal waveform can be implemented to be relatively steep. Accordingly, the maximum value of the signal can be reached within the unit time of signal transmission. In other words, the rate of change of the signal value per unit time can be gradually increased in the first section (P1), and the rate of change of the signal value per unit time can be gradually decreased in the third section (P3). In the fourth section (P4), the signal waveform reaches the maximum value and can be maintained.

In another embodiment, the waveform adjustment unit 111 may be implemented as a waveform adjustment circuit 1112 including a plurality of delay elements 11121 and a plurality of DACs 11122, as illustrated in (b) of FIG. , each of the plurality of DACs 11122 can output a signal delayed by a plurality of delay elements 11121 to form a stepped transmission signal.

In another embodiment, the waveform adjustment unit 111 includes a variable delay element 11121-1 and a variable DAC 11122-1 in the waveform adjustment circuit 1112-1, as illustrated in (c) of FIG. 7. This can be done, and the waveform of the transmission signal can be adjusted as illustrated in FIG. 10 by adjusting the delay time and amplification rate accordingly.

Referring to (c) of FIG. 10, it can be seen that, unlike the case illustrated in (c) of FIG. 8, the maximum signal value increased but the maximum slope decreased. This has an advantage in cases where the profile of the residual signal is not properly removed from the digital domain due to timing error.

In FIG. 9, the residual signal is displayed as a solid line and the profile signal is displayed as a dotted line. As illustrated in (a) of FIG. 9, the slope of the transmission signal waveform is large, and as illustrated in (b) of FIG. 9, the transmission signal Comparing the case where the slope of the waveform is small, it can be understood that the difference in signal values generated during a short time (t1) is large V1 > V2. Therefore, it can be understood that in the echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention, the smaller the initial slope of the transmission signal waveform, the more the problem due to self-interference can be improved.

The echo cancellation circuit for asymmetric full duplex signal transmission and reception according to an embodiment of the present invention may further include a control unit 15 that controls the degree of waveform adjustment. The adjusted waveform is more useful when the initial slope is small, but if the initial slope is excessively lowered, problems may occur in which the maximum value of the signal cannot be reached in the minimum unit time, so the waveform is adjusted to a range that can satisfy at least these two conditions. It has to be.

In one embodiment, the control unit 15 may include an analysis unit 151 and an adjustment command generation unit 152. The analysis unit 151 performs the function of analyzing the data signal output from the ADC 121. The adjustment command generation unit 152 uses the analysis results of the analysis unit 151 to generate an adjustment command to control the waveform adjustment unit 111. Here, the adjustment command may mean a command that causes the waveform adjustment unit 111 to modify the waveform value adjustment variable used to adjust the waveform of the transmission signal. For example, the adjustment command may be a command for controlling the multi-bit DAC (1111). Additionally, the adjustment command may be a command that controls adjustment variables such as the delay time of each delay element or the amplification rate of the DAC.

Referring to FIG. 11, the transmitter 11 outputs a transmission signal (S110). At this time, it is preferable that S110 is performed in a state where the distal transceiver 3 is not transmitting. Next, the analysis unit 151 measures and analyzes the profile (S120). Next, it is determined whether the condition is satisfied based on the measured profile (S130). At this time, if the condition is not met, the waveform value control variable is modified and fed back to step S110. By repeating this process, if a profile satisfying the conditions is confirmed in step S130, this profile is stored (S150). At this time, the waveform is saved along with the profile.

The profile data secured in this way may be stored in the profile register 14 and provided to the subtractor 122.

The subtractor 122 can remove the self-interference signal caused by the signal transmitted by the transmitter 11 by removing profile data from the data signal output from the ADC 121.

When the profile data is prepared in this way, even if the transceiver 1 transmits a transmission signal in the first frequency band while the distal transceiver 3 is transmitting a transmission signal in the second frequency band, the receiver of the transceiver 1 By filtering the received signal (123) and subtracting pre-prepared profile data from the digital signal output through the ADC (121), the self-interference problem caused by the transmission signal in the first frequency band can be solved.

In one embodiment, the leakage signal profile of the transmitted signal in the first frequency band can be preset in response to a test pulse measured in advance in the absence of a received signal, and then updated through an intermittent correction process. . Additionally, profiles can be preset to known values.

As described above, in the digital domain, a profile for a transmitted signal can be maintained in advance, so the size and shape of a leakage signal due to the currently transmitted signal can be predicted. In addition, the waveform predicted in real time can be removed through a subtraction operation in the digital domain, thereby solving the self-interference problem.

The present invention has been described with reference to an embodiment illustrated in the accompanying drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. You will be able to. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

1: transceiver
11: Transmitter
111: Waveform adjustment unit
1111: Multi-bit DAC
1112: Waveform adjustment circuit
11121: Delay element
11122 : DAC
112: buffer
113: serializer
12: receiver
121: ADC
122: subtractor
123: filter
13: Common connection pin
14: Profile register
15: control unit
151: analysis department
152: Adjustment command generation unit
2: Transmission line
3: Original transmitter and receiver

Claims (8)

In the echo cancellation circuit for asymmetric full duplex signal transmission and reception, including a transceiver where a transmitter for transmitting a first frequency band signal and a receiver for receiving a second frequency band signal are connected to a common connection pin,
The transmitter converts transmission data into an analog signal to generate a transmission signal and includes a waveform adjustment unit that adjusts the waveform of the transmission signal,
The receiver includes an ADC that converts an analog signal and outputs a digital signal; and a subtractor for subtracting profile data from the digital signal output from the ADC. Including,
The first frequency band signal and the second frequency band signal have different frequency bands,
The profile data is data of a digital signal output by the ADC when the transmitter transmits the first frequency band signal but there is no second frequency band signal. Echo cancellation for asymmetric full duplex signal transmission and reception Circuit.
According to paragraph 1,
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, wherein the waveform adjustment unit adjusts the waveform of the transmission signal so that the rate of change of the signal value per unit time is reduced.
According to paragraph 1,
The first frequency band signal is a signal of a lower frequency band than the second frequency band signal,
The receiver further includes a filter that passes a signal higher than the minimum frequency of the second frequency band among the signals input to the receiver.
According to paragraph 1,
The waveform adjustment unit, the transmission signal
A first section in which the rate of change of the signal value per unit time gradually increases,
A third section in which the rate of change of the signal value per unit time gradually decreases, and
A second section corresponding to between the first section and the third section
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, characterized in that it adjusts the waveform of the transmission signal including.
According to paragraph 1,
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, wherein the waveform adjustment unit includes a multi-bit DAC.
According to paragraph 1,
The waveform adjustment unit includes a plurality of delay elements and a plurality of DACs,
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, wherein each of the plurality of DACs outputs a signal delayed by the plurality of delay elements to form a stepped transmission signal.
According to clause 6,
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, wherein at least some of the plurality of delay elements and the plurality of DACs are implemented as variable elements.
According to paragraph 1,
The transmitter is,
It further includes an analysis unit that analyzes the ADC output signal and an adjustment command generation unit that generates an adjustment command to control the waveform adjustment unit,
An echo cancellation circuit for asymmetric full duplex signal transmission and reception, wherein the adjustment command causes the waveform adjustment unit to modify a waveform value adjustment variable used to adjust the waveform of the transmission signal.