A method for improving signal transmission efficiency in digital isolators based on quadrature amplitude modulation

Abstract

The present invention discloses a method for improving the signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation, which relates to communication technology and digital isolation technology, and can efficiently utilize the transmission channel in the digital isolator to improve the signal transmission efficiency. The digital isolator of the present invention includes a transmitting module, a transmission channel, and a receiving module; the method is divided into three steps: 1) the transmitting module of the digital isolator divides the multi-channel input signals into two groups, maps the digital characteristics of each group into analog potentials, and modulates the characteristics of all input signals onto one signal through orthogonal amplitude modulation; 2) only one isolation transmission medium is required for transmitting the signal after the orthogonal amplitude modulation of the transmitting module; 3) the receiving module demodulates and decodes the signal transmitted from the isolation transmission medium to generate the final multi-channel output.

Description

Technical Field

[0001] The invention relates to communication technology and digital isolation technology, and in particular to a method for improving signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation. Background Art

[0002] Quadrature Amplitude Modulation is a modulation method that multiplies the modulating signal with two orthogonal carriers so that the amplitude of the carrier signal contains the information of the modulating signal. This modulation method is very suitable for digital signals, similar to the amplitude shift keying method, which modulates the digital code of the input signal onto the amplitude of the carrier. However, the application range of quadrature amplitude modulation is wider, and this method can greatly improve the signal transmission rate of the input signal. Common modulation methods include hexadecimal quadrature amplitude modulation and 64-decimal quadrature amplitude modulation.

[0003] Digital isolators play a very important role in scenarios where high voltage and low voltage coexist. They are often found in automotive electronics, mechanical automation, and medical equipment. In order to ensure the security of communication, it is necessary to isolate the high voltage domain from the low voltage domain, which includes power isolation and signal isolation. The power isolation requirement means that the electronic devices at both ends of the isolator must have their own separate power supply and grounding points. Signal isolation means that the communication between the electronic devices at both ends of the isolator cannot be carried out directly through a low-resistance channel. There must be a high-resistance isolation barrier to ensure the safety between different electronic devices. However, this often affects the efficiency of digital communication, so a method that can greatly improve channel utilization is needed. Summary of the invention

[0004] One object of the present invention is to improve the utilization rate of the isolation channel in the digital isolator and realize a method for efficient utilization of the isolation channel. The present invention first proposes a digital isolator, including a transmission channel composed of a transmitting module, a receiving module and an isolation transmission medium; the transmitting module has multiple input ports and one output port; the receiving module has one input port and multiple output ports; the number of the transmission channel is one, and the two ends of the transmission channel are respectively connected to the output port of the transmitting module and the input port of the receiving module; wherein the number of the input port of the transmitting module is equal to the number of the output port of the receiving module;

[0005] The transmitting module includes a signal preprocessing module, a digital-to-analog conversion module and a signal modulation module; the signal preprocessing module preprocesses the input multi-channel input signals, and the digital-to-analog conversion module is used to convert the digital code of the input signal into a corresponding analog level value; the signal modulation module is used to modulate the analog level onto the carrier signal by orthogonal amplitude modulation to obtain a final modulated signal;

[0006] The transmission channel is used to transmit a signal with multi-channel input signal characteristics to a receiving module; the receiving module includes a demodulation module, a level judgment module and an analog-to-digital conversion module; the demodulation module is used to generate a carrier signal and multiply the carrier signal with the final modulation signal, demodulate the signal, and obtain the corresponding analog level value; the level judgment module is used to judge the analog level obtained after demodulation to reduce the bit error rate of the signal; the analog-to-digital conversion module is used to convert the level judged by the level judgment module into a corresponding digital code and generate a final output.

[0007] As a preferred solution of the present invention, the signal preprocessing module preprocesses multiple input signals, including filtering out high-frequency noise through a filter; removing circuit glitches that appear on the input signal to prevent circuit misjudgment caused by irregular changes in the amplitude of the input signal; and shaping the input signal to make the input signal a high / low level that the circuit can correctly distinguish.

[0008] As a preferred solution of the present invention, the transmission channel includes but is not limited to capacitors, transformers, light emitting diodes and combinations thereof.

[0009] The present invention also provides a method for improving signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation, comprising the following steps:

[0010] The transmitting module first pre-processes the multi-channel input signals, divides the pre-processed input signals into two groups, maps the digital codes of each group of input signals into analog potentials, multiplies the analog potential obtained by the first group with the carrier, and multiplies the analog potential obtained by the second group with the carrier after phase shift of 90°, and adds the two multiplied signals to realize orthogonal amplitude modulation, thereby obtaining a modulated signal with the characteristics of the multi-channel input signals;

[0011] The transmission channel composed of the isolation transmission medium transmits the modulated signal having the characteristics of the multi-channel input signals to the receiving module;

[0012] The receiving module demodulates, filters, extracts signal features from the signal having the characteristics of multiple input signals, decodes all input signals, and generates a final output.

[0013] As a preferred solution of the present invention, the grouping of the input signals is specifically as follows: N input signals are divided into two groups, the number of input signals in the first group is i, and there are 2 i The number of input signals in the corresponding second group is Ni, with 2 N-i A digital code.

[0014] As a preferred solution of the present invention, the process of physical mapping of the digital code maps the input signal into a corresponding analog potential according to the digital code of each group of signals.

[0015] As a preferred solution of the present invention, the transmission channel composed of the isolation transmission medium physically isolates the generating module and the receiving module, and there is a transmission path for the physical signal; the isolation methods in the transmission channel include but are not limited to electromagnetic isolation, capacitive isolation, and optical coupling isolation.

[0016] As a preferred solution of the present invention, the receiving module demodulates the modulated signal transmitted to the receiving module through the transmission channel, multiplies the carrier signal with the final modulation signal to obtain a first group of demodulated signals; and multiplies the carrier signal after phase shifting 90° with the final modulation signal to obtain a second group of demodulated signals.

[0017] As a preferred solution of the present invention, the receiving module performs low-pass filtering on the demodulated signal to obtain a characteristic signal existing on the modulated signal; decodes the characteristic signal, judges the extracted characteristic signals one by one, and generates a final output.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The digital isolator of the present invention is cleverly designed and realizes the transmission of multi-channel signals by adopting one isolation channel.

[0020] The method for improving signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation proposed by the present invention can improve the utilization rate of the isolation medium in the digital isolator, reduce the area of ​​the chip, improve the digital transmission rate, and has a simple structure and strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an overall structural diagram of the example of this method.

[0022] Figure 2 It is a 2-bit 4-level converter involved in the example described in this method.

[0023] Figure 3 This is the corresponding relationship between the input and output of the 2-bit 4-level converter in the example described in this method.

[0024] Figure 4 It is a logic block diagram of level determination in the example of this method.

[0025] Figure 5 It is the corresponding relationship between the input and output of the 2-bit analog-to-digital conversion module of the example of this method. DETAILED DESCRIPTION

[0026] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0027] In addition, it should be understood by those skilled in the art that the drawings provided herein are for illustrative purposes and that the drawings are not necessarily drawn to scale. At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through an electrical connection or an electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected" between two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two. Unless the context clearly requires, the words "including", "comprising" and the like in the specification should be interpreted as including the meaning rather than the exclusive or exhaustive meaning; that is, the meaning of "including but not limited to". In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0028] In a specific embodiment of the present invention, Figure 1 As shown, a digital isolator includes a transmitting module, a receiving module and a transmission channel formed by an isolation transmission medium; the transmitting module has four input ports and one output port; the receiving module has one input port and four output ports; the number of the transmission channel is one, and the two ends of the transmission channel are respectively connected to the output port of the transmitting module and the input port of the receiving module; wherein the number of the input port of the transmitting module is equal to the number of the output port of the receiving module;

[0029] In this embodiment, the transmitting module includes a signal preprocessing module, a digital-to-analog conversion module and a signal modulation module; the signal preprocessing module preprocesses multiple input signals, and the digital-to-analog conversion module is used to convert the digital code of the input signal into a corresponding analog level value; the functions of the preprocessing module and the digital-to-analog conversion module in the transmitting module are realized by a 2bit4 level conversion module; the signal modulation module is used to modulate the analog level onto the carrier signal by orthogonal amplitude modulation; the signal modulation module is composed of three modules: a carrier signal generation module, a multiplication module, and an addition module;

[0030] In this embodiment, the transmission channel is used to transmit a signal with multi-channel input signal characteristics to a receiving module; the receiving module includes a multiplication module, a carrier signal generating module, a filter, a 4-level judgment module and an analog-to-digital conversion module; the multiplication module, the carrier signal generating module and the filter are used as a demodulation module to generate a carrier signal and multiply the carrier signal with the final modulation signal, demodulate the signal, and obtain the corresponding analog level value; the level judgment module is a 4-level judgment module, and the level judgment module is used to judge the analog level obtained after demodulation to reduce the bit error rate of the signal; the analog-to-digital conversion module adopts a 2-bit ADC, and the analog-to-digital conversion module is used to convert the level judged by the level judgment module into a corresponding digital code and generate a final output.

[0031] In this embodiment, a method for improving signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation is also provided; the method comprises the following steps:

[0032] Step 1: Preprocess the four input signals;

[0033] First, the four input signals IN1, IN2, IN3, and IN4 will cause various interferences to the input signals during transmission due to the existence of actual conditions including but not limited to bonding wires, crosstalk, and electromagnetic interference (EMI). Therefore, the input signals must be filtered first. The actual noise frequency is in a higher frequency band than the transmission signal, so the high-frequency noise in the signal can be filtered out by low-pass filtering the signal.

[0034] Step 2: Figure 2 A circuit diagram of a 2bit4 level converter is given to realize the level conversion of the input signal. Figure 3 The corresponding relationship between the input and output of the 2-bit 4-level converter is given. The specific conversion process is:

[0035] IN1 is connected to LSB, IN2 is connected to MSB, and after passing through a 2-4 decoder composed of a logic circuit, intermediate signals (S1, _S1), (S2, _S2), (S3, _S3), (S4, _S4) are generated to realize the output level selection function;

[0036] Connect 5 resistors with a resistance value of R in series, with one end connected to VDD and the other end connected to -VDD. The 4 intermediate nodes of the circuit generate the required voltage levels (3VDD / 5, VDD / 5, -VDD / 5, -3VDD / 5). Each node is then connected to a transmission gate. The enable signal of each transmission gate is from top to bottom: (S1, _S1), (S2, _S2), (S4, _S4), (S3, _S3), and finally the voltage level output function is realized.

[0037] Further, IN3 is connected to the LSB, and IN4 is connected to the MSB, and the intermediate signals (S5, _S5), (S6, _S6), (S7, _S7), (S8, _S8) are generated through a 2-4 decoder composed of a logic circuit to realize the output level selection function;

[0038] Connect 5 resistors with a resistance value of R in series, with one end connected to VDD and the other end connected to -VDD. The 4 intermediate nodes of the circuit generate the required voltage levels (3VDD / 5, VDD / 5, -VDD / 5, -3VDD / 5). Each node is then connected to a transmission gate. The enable signal of each transmission gate is from top to bottom: (S5, _S5), (S6, _S6), (S7, _S7), (S8, _S8), and finally the voltage level output function is realized.

[0039] Combined with the level selection function, the level output function finally realizes 2bit4 level conversion, where A_I has four level amplitudes (3VDD / 5, VDD / 5, -VDD / 5, -3VDD / 5) and A_Q has four level amplitudes (3VDD / 5, VDD / 5, -VDD / 5, -3VDD / 5).

[0040] Step 3: Implement the quadrature amplitude modulation function. The specific process is as follows:

[0041] Branch where IN1 and IN2 are located: I_TX = A_I*sin (wct);

[0042] Branch where IN3 and IN4 are located: Q_TX = A_Q*cos (wct);

[0043] Final modulated signal: M=I_TX+Q_TX=A_I*sin(wct)+A_Q*cos(wct).

[0044] Step 4: Signal coherent demodulation, the specific process is as follows:

[0045] OUT1, OUT2 branch: I_RX = M*sin (wct);

[0046] OUT3, OUT4 branch: Q_RX = M*cos (wct);

[0047] Step 5: Perform low-pass filtering on I_RX and Q_RX to obtain DC components AI and AQ. The corresponding relationship between AI and A_I is that when the value of AI is less than -2VDD / 5, the value of A_I is -3VDD / 5; when the value of AI is greater than -2VDD / 5 and less than 0, the value of A_I is -VDD / 5; when the value of AI is greater than 0 and less than 2VDD / 5, the value of A_I is VDD / 5; when the value of AI is greater than 2VDD / 5, the value of A_I is 3VDD / 5

[0048] The corresponding relationship between AQ and A_Q is that when the value of AQ is less than -2VDD / 5, the value of A_Q is -3VDD / 5; when the value of AQ is greater than -2VDD / 5 and less than 0, the value of A_Q is -VDD / 5; when the value of AQ is greater than 0 and less than 2VDD / 5, the value of A_Q is VDD / 5; when the value of AQ is greater than 2VDD / 5, the value of A_Q is 3VDD / 5.

[0049] Step 6: Make level judgment on AI and AQ. Figure 4 The logic block diagram of the level judgment is given. When the value of the input signal is less than -2VDD / 5, the value of the output signal is -3VDD / 5; when the value of the input signal is greater than -2VDD / 5 and less than 0, the value of the output signal is -VDD / 5; when the value of the input signal is greater than 0 and less than 2VDD / 5, the value of the output signal is VDD / 5; when the value of the input signal is greater than 2VDD / 5, the value of the output signal is 3VDD / 5. This step takes into account that during the actual transmission of the signal, the level generated in step 2 will be offset. In order to reduce the bit error rate and improve the accuracy of the signal output, it is necessary to perform level judgment and generate the corresponding level.

[0050] Step 7: Use a 2-bit analog-to-digital converter to convert the level generated in step 6 into a digital signal to complete the final output. Figure 5 As shown, when the value of A_I (A_Q) is -3VDD / 5, OUT1 (OUT3) and OUT2 (OUT4) are "0" and "1"; when the value of A_I (A_Q) is -VDD / 5, OUT1 (OUT3) and OUT2 (OUT4) are "1" and "1"; when the value of A_I (A_Q) is VDD / 5, OUT1 (OUT3) and OUT2 (OUT4) are "1" and "0"; when the value of A_I (A_Q) is 3VDD / 5, OUT1 (OUT3) and OUT2 (OUT4) are "0" and "0".

[0051] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for improving signal transmission efficiency in a digital isolator based on orthogonal amplitude modulation, wherein the digital isolator comprises a transmission channel formed by a transmitting module, a receiving module and an isolation transmission medium; the transmitting module has a plurality of input ports and an output port; the receiving module has an input port and a plurality of output ports; the number of the transmission channel is one, and the two ends of the transmission channel are respectively connected to the output port of the transmitting module and the input port of the receiving module; The number of input ports of the transmitting module is equal to the number of output ports of the receiving module; The transmitting module includes a signal preprocessing module, a digital-to-analog conversion module and a signal modulation module; the signal preprocessing module preprocesses the input multi-channel input signals, and the digital-to-analog conversion module is used to convert the digital code of the input signal into a corresponding analog level; The functions of the pre-processing module and the digital-to-analog conversion module in the transmitting module are realized by a 2-bit 4-level conversion module; the signal modulation module is used to modulate the analog level onto the carrier signal by orthogonal amplitude modulation and obtain the final modulated signal; The transmission channel is used to transmit a signal with multi-channel input signal characteristics to a receiving module; the receiving module includes a demodulation module, a level judgment module and an analog-to-digital conversion module; the demodulation module is used to generate a carrier signal and multiply the carrier signal with the final modulation signal, demodulate the signal, and obtain the corresponding analog level value; the level judgment module is a 4-level judgment module, and the level judgment module is used to judge the analog level obtained after demodulation to reduce the bit error rate of the signal; The analog-to-digital conversion module uses a 2-bit ADC, and the analog-to-digital conversion module is used to convert the level determined by the level determination module into a corresponding digital code and generate a final output; Characterized in that the method comprises the following steps: The transmitting module first preprocesses the multi-channel input signals and divides the preprocessed input signals into two groups. The number of input signals in the first group is i, with 2 i The number of input signals in the corresponding second group is Ni, with 2 N-i A digital code is provided, where N is the number of paths into which the input signal is divided; the digital code of each group of input signals is mapped to an analog potential according to the digital code of each group of signals, the analog potential obtained by the first group is multiplied by the carrier, the analog potential obtained by the second group is multiplied by the carrier after a 90° phase shift, the two multiplied signals are added together, orthogonal amplitude modulation is realized, and a modulated signal having the characteristics of multiple input signals is obtained; The transmission channel composed of the isolation transmission medium transmits the modulated signal having the characteristics of the multi-channel input signals to the receiving module; The receiving module demodulates, filters, extracts signal features, and decodes all input signals for the signal with the characteristics of multiple input signals to generate a final output; wherein the receiving module demodulates the modulated signal transmitted to the receiving module through the transmission channel, multiplies the carrier signal with the final modulation signal to obtain a first group of demodulated signals; multiplies the carrier signal after phase shifting 90° with the final modulation signal to obtain a second group of demodulated signals; the receiving module performs low-pass filtering on the demodulated signal to obtain a characteristic signal existing on the modulation signal; decodes the characteristic signal, judges the extracted characteristic signals one by one, and generates a final output.

2. The method according to claim 1, characterized in that The signal preprocessing module preprocesses the multiple input signals, including filtering out high-frequency noise through a filter; removing circuit glitches on the input signal to prevent circuit misjudgment caused by irregular changes in the amplitude of the input signal; and shaping the input signal to make the input signal a high / low level that the circuit can correctly distinguish.

3. The method according to claim 1, characterized in that The transmission channel includes a capacitor, a transformer, a light emitting diode and a combination thereof.

4. The method according to claim 1, characterized in that: The transmission channel composed of the isolation transmission medium physically isolates the transmitting module and the receiving module, and there is a transmission path for physical signals; the isolation methods in the transmission channel include electromagnetic isolation, capacitive isolation, and optical coupler isolation.

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