CN115150236A

CN115150236A - Signal processing method and related equipment

Info

Publication number: CN115150236A
Application number: CN202110341411.7A
Authority: CN
Inventors: 吕瑞; 李昆
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2022-10-04
Also published as: WO2022206464A1

Abstract

The embodiment of the application discloses a signal processing method and related equipment, which can be applied to a scene of terahertz short-distance communication. The method of the embodiment of the application comprises the following steps: and the sending end equipment modulates the original baseband signal to obtain a target modulation signal. And the level set of the target baseband signal corresponding to the target modulation signal comprises a positive level and a negative level. The set of levels includes a positive level and a negative level. The set of levels includes at least one first level and a second level that is similar or equal in magnitude but opposite in polarity to the first level is not in the set of levels. The set of levels further includes at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. Further, the transmitting-end device transmits the target modulation signal to the receiving-end device. The receiving end equipment can complete demodulation by adopting a differential demodulation method according to the amplitude information and the phase information of the signal without depending on carrier synchronization, thereby reducing the complexity and the power consumption of the realization.

Description

Signal processing method and related equipment

Technical Field

The present application relates to the field of communications, and in particular, to a signal processing method and related device.

Background

Terahertz short-distance interconnection utilizes Terahertz Active Cable (TAC) to realize short-distance transmission of high-speed large-bandwidth Terahertz signals. The sending end equipment receives a baseband signal input from an external port, and modulates the baseband signal to a terahertz carrier wave for sending. And the receiving end equipment receives and demodulates the terahertz modulation signal from the TAC, and finally outputs the recovered baseband signal from an output port to realize data transmission.

In order to enable the receiving-end apparatus to correctly demodulate the terahertz modulation signal, one current approach is to perform carrier synchronization. The transmitting end equipment needs to insert pilot frequency information into the transmitting signal, and the receiving end equipment extracts the frequency deviation and the phase deviation of the receiving and transmitting carrier waves by means of the pilot frequency information and the demodulation error of the receiving signal. After compensating the synchronization error in the received signal, the receiving end can correctly demodulate the transmitted signal. However, the functions of inserting pilot information by the sending end and implementing carrier synchronization by the receiving end cause significant complexity and power consumption cost in system implementation.

Disclosure of Invention

The embodiment of the application provides a signal processing method and related equipment.

In a first aspect, the present application provides a signal processing method applied to a sending-end device. The method comprises the following steps: firstly, the sending end device modulates the original baseband signal to obtain a target modulation signal. Besides the original baseband signal needs to be modulated onto the carrier wave during the modulation process, the level of the original baseband signal needs to be adjusted to obtain the target baseband signal, so as to construct a specific level distribution. Specifically, the set of levels of the target baseband signal includes a positive level and a negative level. The set of levels includes at least one first level and a second level of similar or equal magnitude but opposite polarity to the first level is not in the set of levels. Furthermore, the set of levels also includes at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. Further, the transmitting-end device transmits the target modulation signal to the receiving-end device.

In this embodiment, the transmitting end device may process the baseband signal to adjust the level of each symbol in the baseband signal to obtain a particular signal format suitable for differential demodulation. Under the framework that the receiving end equipment adopts coherent reception, aiming at the specific signal format, the receiving end equipment can finish demodulation by adopting a differential demodulation method according to the amplitude information and the phase information of the signal without depending on carrier synchronization. By the method, carrier synchronization is not needed, data pilot frequency is not needed to be added, differential coding is not needed, and complexity and power consumption of implementation are reduced.

In some possible embodiments, the number of values of the level amplitude in the level set is as small as possible, the power consumption required for transmitting the modulation signal by the transmitting-end device can be reduced. For example, the total number of amplitudes of the levels in the level combination is less than 32.

In some possible embodiments, the number of positive and negative levels in the level set is as close as possible but not equal, which may also reduce the power consumption required by the transmitting end device to transmit the modulated signal. For example, the difference in the number of positive and negative levels in the level set is greater than 0 and less than 32.

In some possible embodiments, the modulating, by the sending end device, the original baseband signal to obtain the target modulation signal includes: firstly, the sending end device carries out carrier modulation according to a first carrier signal and an original baseband signal to obtain an original modulation signal. And then, the sending end equipment generates a target modulation signal according to the original modulation signal and the second carrier signal. The frequency of the first carrier signal is the same as that of the second carrier signal, and the amplitude of the first carrier signal is different from that of the second carrier signal. Through the mode, the specific implementation mode for adjusting the level of the original baseband signal is provided, and the realizability of the scheme is enhanced.

In some possible embodiments, the scheme can be applied to a scene of terahertz short-distance communication, wherein the first carrier signal and the second carrier signal are terahertz carrier signals, and the practicability of the scheme is enhanced.

In some possible embodiments, the performing, by the sending end device, carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulated signal includes: the sending end device modulates the original baseband signal to a first carrier signal through a radio frequency switch to obtain an original modulation signal. By the mode, the specific implementation mode for carrying out carrier modulation on the original baseband signal is provided, and the realizability of the scheme is further improved.

In some possible embodiments, the performing, by the sending end device, carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulated signal includes: the sending end device carries out carrier modulation on the first carrier signal and the original baseband signal through the mixer to obtain an original modulation signal. By the mode, another specific implementation mode for carrying out carrier modulation on the original baseband signal is provided, and the flexibility of the scheme is enhanced.

In some possible embodiments, the generating, by the sending end device, the target modulation signal according to the original modulation signal and the second carrier signal includes: and the sending end equipment performs power synthesis on the original modulation signal and the second carrier signal through a power synthesizer to obtain a target modulation signal. By the mode, the specific implementation mode of carrier injection is provided, and the practicability of the scheme is further improved.

In some possible embodiments, the generating, by the sending-end device, the target modulation signal according to the original modulation signal and the second carrier signal includes: and the sending end equipment determines a bias voltage according to the second carrier signal and loads the bias voltage on the original modulation signal to obtain a target modulation signal. By the method, another specific implementation mode of carrier injection is provided, and the flexibility of the scheme is improved.

In some possible embodiments, the step of modulating, by the sending end device, the original baseband signal to obtain the target modulation signal includes: first, the sending end device adjusts the level of an original baseband signal to obtain a target baseband signal, where the target baseband signal has a level set. And then, the sending end equipment carries out carrier modulation according to the third carrier signal and the target baseband signal to obtain a target modulation signal. Through the mode, another specific implementation mode for adjusting the level of the original baseband signal is provided, and the expansibility of the scheme is improved.

In some possible embodiments, the performing, by the sending end device, carrier modulation according to the third carrier signal and the target baseband signal to obtain a target modulation signal includes: and the sending end equipment carries out carrier modulation on the third carrier signal and the target baseband signal through the mixer to obtain a target modulation signal.

In some possible embodiments, the adjusting, by the sending-end device, the level of the original baseband signal to obtain the target baseband signal includes: the sending end equipment adjusts the voltage output by the direct current power supply through the voltage adjusting device, and couples the adjusted voltage with the original baseband signal to obtain a target baseband signal.

In some possible embodiments, the adjusting, by the sending-end device, the level of the original baseband signal to obtain the target baseband signal includes: the sending end equipment adjusts the bias voltage loaded on the original baseband signal by the direct current power supply through the bias voltage adjusting device to obtain a target baseband signal.

In a second aspect, an embodiment of the present application provides a sending end device, which includes a modulation module and a sending module. A modulation module: the modulation method is used for modulating an original baseband signal to obtain a target modulation signal, wherein a level set of the target baseband signal corresponding to the target modulation signal comprises a positive level and a negative level. The set of levels includes at least one first level and a second level that is similar or equal in magnitude but opposite in polarity to the first level is not in the set of levels. Furthermore, the set of levels also includes at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. A sending module: used for transmitting the target modulation signal to the receiving end equipment.

In some possible embodiments, the number of values of the level amplitude in the level set is as small as possible, so that power consumption required by the transmitting end device to transmit the modulation signal can be reduced. For example, the sum of the amplitudes of the levels in the level combination is less than 32.

In some possible embodiments, the number of positive and negative levels in the level set is as close as possible but not equal, which can also reduce the power consumption required by the transmitting end device to transmit the modulated signal. For example, the difference in the number of positive and negative levels in the level set is greater than 0 and less than 32.

In some possible embodiments, the modulation module includes a carrier generation device, a gain adjustment device, a carrier modulation device, and a carrier injection device. The carrier generation means is for generating a first carrier signal. The carrier modulation device is used for carrying out carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulation signal. The gain adjusting device is used for carrying out gain adjustment on the first carrier signal to obtain a second carrier signal. The frequency of the first carrier signal is the same as the frequency of the second carrier signal, and the amplitude of the first carrier signal is different from the amplitude of the second carrier signal. The carrier injection device is used for generating a target modulation signal according to the original modulation signal and the second carrier signal.

In some possible embodiments, the first carrier signal and the second carrier signal are terahertz carrier signals.

In some possible embodiments, the carrier modulation means comprises a radio frequency switch. The radio frequency switch is used for modulating the original baseband signal to a first carrier signal to obtain an original modulation signal.

In some possible embodiments, the carrier modulation means comprises a mixer. The mixer is used for carrying out carrier modulation on the first carrier signal and the original baseband signal to obtain an original modulation signal.

In some possible embodiments, the carrier injection means comprises a power combiner. The power synthesizer is used for performing power synthesis on the original modulation signal and the second carrier signal to obtain a target modulation signal.

In some possible embodiments, the carrier injection means comprises bias voltage adjustment means. The bias voltage adjusting device is used for determining a bias voltage according to the second carrier signal and loading the bias voltage on the original modulation signal to obtain a target modulation signal.

In some possible embodiments, the modulation module includes a level adjustment device, a carrier generation device, and a carrier modulation device. And the level adjusting device is used for adjusting the level of the original baseband signal to obtain a target baseband signal, and the target baseband signal has a level set. The carrier generation means is for generating a third carrier signal. And the carrier modulation device is used for carrying out carrier modulation according to the third carrier signal and the target baseband signal to obtain a target modulation signal.

In some possible embodiments, the carrier modulation means comprises a mixer. The mixer is used for carrying out carrier modulation on the third carrier signal and the target baseband signal to obtain a target modulation signal.

In some possible embodiments, the level adjustment device includes a dc power supply, a voltage adjustment device, and a combiner. The direct current voltage source is used for outputting voltage. The voltage regulating device is used for regulating the voltage. The combiner is used for coupling the regulated voltage and the original baseband signal to obtain a target baseband signal.

In some possible embodiments, the level adjustment device includes a dc power supply and a bias voltage adjustment device. The dc power supply is used to apply a bias voltage to the raw baseband signal. The bias voltage adjusting device is used for adjusting the bias voltage to obtain a target baseband signal.

In a third aspect, the present application provides a signal processing method applied to a receiving end device. The method comprises the following steps: the receiving end device receives the modulation signal from the transmitting end device. The level set of the baseband signal to which the modulation signal corresponds includes a positive level and a negative level. The set of levels includes at least one first level and a second level that is similar or equal in magnitude but opposite in polarity to the first level is not in the set of levels. Furthermore, the set of levels also includes at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. And the receiving end equipment performs amplitude detection on the modulation signal to obtain the level amplitude of each symbol in the baseband signal. And the receiving end equipment performs phase detection on the modulation signal to obtain the phase difference between every two adjacent symbols in the baseband signal. The receiving end device demodulates a first symbol to be demodulated according to the level amplitude of the first symbol, where the first symbol includes a symbol with a first level and a symbol with a level of 0 in the baseband signal. The receiving end device demodulates the second symbol to be demodulated according to the phase difference between the reference symbol and the second symbol to be demodulated, the second symbol includes symbols except the first symbol in the baseband signal, the reference symbol is a symbol which completes demodulation before the second symbol to be demodulated, and the reference symbol does not include a symbol with a level of 0.

In some possible embodiments, the method further comprises: the receiving device generates a carrier signal. And the receiving end equipment carries out orthogonal frequency mixing on the modulation signal and the carrier signal to obtain an I/Q signal.

The amplitude detection of the modulation signal by the receiving end device to obtain the level amplitude of each symbol in the baseband signal comprises: and the receiving end equipment performs amplitude detection on the I/Q signal to obtain the level amplitude of each symbol in the baseband signal.

The phase detection of the modulation signal by the receiving end device to obtain the phase difference between every two adjacent symbols in the baseband signal comprises: the receiving end equipment carries out phase detection on the I/Q signals to obtain the phase of each symbol in the baseband signals, and the phase difference between every two adjacent symbols in the baseband signals is calculated according to the phase of each symbol in the baseband signals.

In some possible embodiments, amplitude detection of the modulated signal by the receiving end device to obtain the level amplitude of each symbol in the baseband signal includes: the receiving end equipment carries out level detection on the modulation signal through an envelope detector to obtain the level of each symbol in the baseband signal.

The phase detection of the modulation signal by the receiving end device to obtain the phase difference between every two adjacent symbols in the baseband signal comprises: the receiving end equipment branches the modulation signal to obtain a first modulation signal and a second modulation signal. And the receiving end equipment performs delay processing on the second modulation signal to obtain a third modulation signal. And the receiving end equipment performs frequency mixing on the first modulation signal and the third modulation signal to obtain a mixed signal, and performs phase detection on the mixed signal to obtain a phase difference between every two adjacent symbols in the baseband signal.

In a fourth aspect, an embodiment of the present application provides a receiving end device, which includes a receiving module, an amplitude detection module, a phase detection module, and a demodulation module. The receiving module is used for receiving the modulation signal from the sending terminal equipment. The level set of the baseband signal to which the modulation signal corresponds includes a positive level and a negative level. The set of levels includes at least one first level and a second level of similar or equal magnitude but opposite polarity to the first level is not in the set of levels. Furthermore, the set of levels also includes at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. The amplitude detection module is used for carrying out amplitude detection on the modulation signal so as to obtain the level amplitude of each symbol in the baseband signal. The phase detection module is used for carrying out phase detection on the modulation signal so as to obtain the phase difference between every two adjacent symbols in the baseband signal. The demodulation module is used for demodulating a first symbol to be demodulated according to the level amplitude of the first symbol, wherein the first symbol comprises a symbol with a first level and a symbol with a level of 0 in the baseband signal. The demodulation module is further configured to demodulate a second symbol to be demodulated according to a phase difference between the reference symbol and the second symbol to be demodulated, where the second symbol includes symbols except the first symbol in the baseband signal, the reference symbol is a symbol that completes demodulation before the second symbol to be demodulated, and the reference symbol does not include a symbol with a level of 0.

In some possible embodiments, the receiving end device further includes an I/Q mixer and a carrier generation apparatus. The carrier generation means is for generating a carrier signal. The I/Q mixer is used for carrying out quadrature mixing on the modulation signal and the carrier signal to obtain an I/Q signal. The amplitude detection module is specifically configured to perform amplitude detection on the I/Q signal to obtain a level amplitude of each symbol in the baseband signal. The phase detection module is specifically configured to perform phase detection on the I/Q signal to obtain a phase of each symbol in the baseband signal, and calculate a phase difference between every two adjacent symbols in the baseband signal according to the phase of each symbol in the baseband signal.

In some possible embodiments, the amplitude detection module comprises an envelope detector, and the phase detection unit module comprises a splitter, a delay adjustment device, a mixer, and a phase detector. The envelope detector is used for carrying out level detection on the modulation signal to obtain the level amplitude of each symbol in the baseband signal. The splitter is used for splitting the modulation signal to obtain a first modulation signal and a second modulation signal. The delay adjusting device is used for carrying out delay processing on the second modulation signal to obtain a third modulation signal. The mixer is used for mixing the first modulation signal and the third modulation signal to obtain a mixed signal. The phase detector is used for carrying out phase detection on the mixed signal to obtain the phase difference between every two adjacent symbols in the baseband signal.

In a fifth aspect, an embodiment of the present application provides a communication system, including the sending end device in any implementation manner of the second aspect and the receiving end device in any implementation manner of the fourth aspect.

In this embodiment, the sending end device may process the baseband signal to adjust the level of each symbol in the baseband signal, so as to obtain a specific signal format suitable for differential demodulation. Under the framework that the receiving end equipment adopts coherent reception, aiming at the specific signal format, the receiving end equipment can finish demodulation by adopting a differential demodulation method according to the amplitude information and the phase information of the signal without depending on carrier synchronization. By the method, carrier synchronization is not needed, data pilot frequency is not needed to be added, differential coding is not needed, and complexity and power consumption of implementation are reduced.

Drawings

Fig. 1 is a schematic structural diagram of a communication system in an embodiment of the present application;

fig. 2 is a schematic diagram of an embodiment of a signal processing method applied to a sending-end device in the present application;

FIG. 3 is a schematic diagram of a level distribution of an original baseband signal according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a level distribution of a target baseband signal according to an embodiment of the present application;

FIG. 5 is a constellation diagram of baseband I/Q signals in an embodiment of the present application;

fig. 6 is a schematic diagram of an embodiment of a signal processing method applied to a receiving end device in the present application;

FIG. 7 is another constellation diagram of baseband I/Q signals in an embodiment of the present application;

FIG. 8 is another constellation diagram of baseband I/Q signals in an embodiment of the present application;

fig. 9 is a schematic diagram of a first structure of a sending end device in an embodiment of the present application;

fig. 10 is a schematic diagram of a second structure of a sending end device in an embodiment of the present application;

FIG. 11 is a schematic diagram of carrier modulation by an RF switch according to an embodiment of the present application;

FIG. 12 is a schematic diagram of reverse phase power combining in an embodiment of the present application;

fig. 13 is a schematic diagram of a third structure of a sending end device in the embodiment of the present application;

fig. 14 is a schematic diagram of a first structure of a receiving end device in the embodiment of the present application;

fig. 15 is a schematic diagram of a second structure of a receiving end device in the embodiment of the present application;

fig. 16 is a schematic structural diagram of a receiving end device in the embodiment of the present application;

fig. 17 is a schematic structural diagram of a communication system in an embodiment of the present application.

Detailed Description

The embodiment of the application provides a signal processing method and related equipment, and transmitting end equipment can process a baseband signal to adjust the level of each symbol in the baseband signal, so that the baseband signal with a specific level distribution mode is obtained. The receiving end equipment can complete demodulation by adopting a differential demodulation method according to the amplitude information and the phase information of the baseband signal, thereby reducing the complexity and the power consumption of the realization. It should be noted that the terms "first," "second," "third," "fourth," and the like (if any) in the description and claims of this application and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Fig. 1 is a schematic structural diagram of a communication system in an embodiment of the present application. As shown in fig. 1, the present application is mainly applied in the scenario of terahertz short-range communication. Short-distance transmission of high-speed large-bandwidth Terahertz signals is achieved between the sending end device 1 and the receiving end device 2 through a Terahertz Active Cable (TAC) 3. In order to increase the transmission distance of the terahertz signal in the TAC (3) and provide a larger signal bandwidth and a larger data transmission rate, the transmitting end device 1 and the receiving end device 2 need to adopt coherent modulation and demodulation to improve the receiving sensitivity. Specifically, the transmitting-end device 1 receives a baseband signal input from an external port, the carrier generation module 12 outputs a terahertz carrier, and the modulation module 11 modulates the baseband signal onto the terahertz carrier for transmission. The receiving end device 2 receives the terahertz modulation signal from the TAC (3), the carrier generation module 22 outputs a terahertz carrier, and the demodulation module 21 demodulates the terahertz modulation signal according to the terahertz carrier to recover the baseband signal.

It should be understood that the transmitting end device 1 and the receiving end device 2 described above are defined based on the data flow direction. The sending end device 1 may also include the demodulation module 21 and the carrier generation module 22 described above to implement the functions of the receiving end device 2. Similarly, the receiving end device 2 may also include the above-mentioned modulation module 11 and carrier generation module 12 to implement the functions of the transmitting end device 1.

Currently, coherent demodulation is usually performed by using a carrier synchronization or differential phase keying manner, but the complexity of signal processing is high by using these manners, and the power consumption of a transmitting end device and a receiving end device is also high. Therefore, the present application provides a signal processing method and related device, which reduce implementation complexity and power consumption, and are described in detail below.

Fig. 2 is a schematic diagram of an embodiment of a signal processing method applied to a sending-end device in the present application. In this example, the signal processing method includes the following steps.

201. And the sending end equipment modulates the original baseband signal to obtain a target modulation signal.

The sending end equipment obtains a target modulation signal by modulating the original baseband signal. In addition to modulating the original baseband signal onto the carrier wave, the level of the original baseband signal needs to be adjusted during the modulation process, so as to construct a specific level distribution. That is, the level set of the target baseband signal corresponding to the target modulation signal has such a specific level distribution. The target baseband signal may be understood as a baseband signal obtained by level-adjusting an original baseband signal. The original baseband signal, the target modulated signal and the target baseband signal will be described below by taking fig. 11 and fig. 12 as an example. As shown in fig. 11, modulating the original baseband signal onto the first carrier signal can obtain an original modulated signal, which is a sine wave signal of high frequency. The dotted line above the original modulation signal can be regarded as an envelope of the original modulation signal, which is used to represent the level distribution of the original baseband signal corresponding to the original modulation signal. As shown in fig. 12, the target modulation signal can be obtained by performing carrier injection on the original modulation signal. Similarly, the dotted line above the target modulation signal may be regarded as an envelope of the target modulation signal, which is used to represent the level distribution of the target baseband signal corresponding to the target modulation signal. The level of the original baseband signal can be adjusted by means of carrier injection to obtain the level distribution of the target baseband signal.

In particular, the set of levels includes a positive level and a negative level. The set of levels includes at least one first level and a second level of similar or equal magnitude but opposite polarity to the first level is not in the set of levels. The set of levels further comprises at least a third level and a fourth level, the third level and the fourth level being of similar or equal magnitude and opposite polarity. The level distribution provided by the present application is described below with a specific example.

Fig. 3 is a schematic diagram of a level distribution of an original baseband signal according to an embodiment of the present application. It should be understood that the level of the original baseband signal is typically made up of a positive level. As shown in fig. 3, the original baseband signal in the PAM4 format is taken as an example, and the original baseband signal has 4 different levels with levels (1, 2,3, and 4), respectively. Alternatively, the levels of the original baseband signal may be symmetrically distributed with respect to the level 0, for example, the original baseband signal may have 4 different levels having levels (-1.5, -0.5, 1.5). In addition, in any of the level distribution methods, the level distributions are equally spaced. The application does not limit the specific size of a level interval, for example, a level "1" means 50mv, a level "2" means 100mv, and then a level interval is 50mv.

Fig. 4 is a schematic diagram of a level distribution of a target baseband signal in an embodiment of the present application. The present embodiment constructs a level distribution that is not completely symmetrical with respect to the 0 level, unlike the level distribution of the original baseband signal, and the conventional modulation method does not construct such a specific level distribution. In particular, such a specific level distribution can be obtained by adjusting the level of the original baseband signal entirely upward or entirely downward. As shown in fig. 4, the level of the original baseband signal shown in fig. 3 may be adjusted downward as a whole to obtain target baseband signals having (-1, 0, 1, 2) 4 different levels. It can be seen that level "2" corresponds to the first level mentioned above, level "1" and level "-1" correspond to the third level and fourth level mentioned above, and level "-2", which is symmetrical to level "2", is not in the set of levels of the target baseband signal. It will be appreciated that the magnitudes of the first and second levels are not necessarily exactly equal, nor are the magnitudes of the third and fourth levels. The design requirement of the present application is also met as long as the difference between the amplitudes of the first level and the second level is less than or equal to the preset value, and the difference between the amplitudes of the third level and the fourth level is less than or equal to the preset value. The preset value is not limited to a size, and for example, the preset value may be 10% of one level interval. That is, the level error acceptable in the present application is 10% of one level interval at the maximum. For example, the level distributions (-0.9, 0, 1, 2) also meet the design requirements of the present application, while (-1.5, -0, 1, 2) do not meet the design requirements of the present application. It should be understood that the third level and the fourth level may be regarded as levels of the same magnitude as long as they are within the acceptable range of the level error. The first level may be a level having a unique magnitude of a level in the target baseband signal, and is not particularly limited to a certain level. That is, the first level includes at least one level having a unique level amplitude. For example, if the target baseband signal has 4 different levels (-0.5, 1.5, 2.5), the first level includes a level "1.5" and a level "2.5".

In some possible embodiments, in order to reduce power consumption required by the transmitting end device to transmit the modulated signal, the number of positive and negative levels in the level set of the target baseband signal should be as close as possible but not equal to each other, and the number of values of the level amplitude in the level set should be as small as possible. For example, also by adjusting the level of the original baseband signal shown in fig. 3 downward as a whole, the power consumption required for transmitting a signal having a level distribution of (-1, 0, 1, 2) is lower than that required for transmitting a signal having a level distribution of (-0.5, 1.5, 2.5). It should be understood that the number of values of the level amplitude in the level set should satisfy: 1 < M < 32, wherein M represents the value number of the level amplitude in the level set. The difference between the number of positive and negative levels in the set of levels should be such that: n is more than 0 and less than 32. It should be understood that the upper limit of the values of M and N may be 32, 64, etc., and the specific description herein is not limited.

202. The sending end equipment sends the target modulation signal to the receiving end equipment.

The target modulation signal sent by the sending end equipment is transmitted to the receiving end equipment through a line. The receiving end equipment can obtain a baseband I/Q signal after carrying out coherent demodulation by using a locally generated carrier. There may be time-varying conditions in both frequency and phase due to the carrier generated by the transmitting device and the carrier generated by the receiving device. This carrier non-synchronization condition can result in unknown dynamic rotation of the demodulated baseband I/Q signal. Fig. 5 is a constellation diagram of a baseband I/Q signal in an embodiment of the present application. Based on the level distribution of the target baseband signal shown in fig. 4, four levels (-1, 0, 1, 2) are named A, B, C, D, respectively, as shown in fig. 5. Due to the presence of the indeterminate rotation of the I/Q phase, the four levels of the target baseband signal will form a central origin and two circular traces with different radial amplitudes on the I/Q plane. Wherein B is located at the center origin, A and C are located on a circular trajectory with a radius of 1, and D is located on a circular trajectory with a radius of 2. Since the transmitting end device constructs the level distribution of the target baseband signal, the receiving end device can still demodulate the received baseband signal under the condition that the carriers are not synchronized, so as to recover the target baseband signal transmitted by the transmitting end device. The following describes a signal processing method of the receiving end device.

Fig. 6 is a schematic diagram of an embodiment of a signal processing method applied to a receiving end device in the present application. In this example, the signal processing method includes the following steps.

601. The receiving end device receives the target modulation signal from the transmitting end device.

602. And the receiving end equipment carries out amplitude detection on the target modulation signal to obtain the level amplitude of each symbol in the target baseband signal.

It should be understood that the target baseband signal may be divided by symbols, and each symbol may contain the same number of bits. The receiving end device may perform amplitude detection on each symbol in turn to obtain a level amplitude of each symbol.

603. And the receiving end equipment performs phase detection on the target modulation signal to obtain the phase difference between every two adjacent symbols in the baseband signal.

It should be understood that the receiving end device needs to adopt a differential decision manner for the symbols with partially identical electrical amplitude. Therefore, the receiving-end device needs to perform phase detection on the target modulation signal to obtain the phase difference between every two adjacent symbols.

604. And the receiving terminal equipment demodulates the first symbol to be demodulated according to the level amplitude of the first symbol.

In this embodiment, the first symbol is a symbol having a first level or a symbol having a level of 0 in the target baseband signal. It should be understood that if the level amplitude of a certain symbol is unique in the levels of all symbols, the receiving end device can perform demodulation according to the level amplitude of the symbol. Since there is no second level in the target baseband signal that is similar or equal in magnitude to the first level but opposite in polarity, the first level is unique among the levels of all symbols, and the 0 level is also unique among the levels of all symbols. Taking fig. 5 as an example, if the level amplitude of the current symbol to be demodulated is 2, the current symbol to be demodulated can be decided as level D. If the level amplitude of the current symbol to be demodulated is 0, the current symbol to be demodulated can be judged as level B.

605. And the receiving end equipment demodulates the second symbol to be demodulated according to the phase difference between the reference symbol and the second symbol to be demodulated.

In this embodiment, the second symbol is a symbol other than the first symbol in the target baseband signal. That is, the level amplitude of the first symbol is unique among the levels of all the symbols, and the level amplitude of the second symbol is not unique among the levels of all the symbols. At least one set of second symbols having similar or equal levels of magnitude but opposite polarity is present in the target baseband signal, e.g., the second symbols include the third level symbols and the fourth level symbols described above. The demodulation cannot be performed only according to the level amplitude of the second symbol, therefore, the reference is neededThe second symbol is demodulated by the symbol, wherein the reference symbol is a symbol that completes demodulation before the second symbol to be demodulated. The demodulation method of the second symbol is described below with reference to fig. 5 as an example. If the level amplitude of the current second symbol to be demodulated is 1, further comparing the phase difference between the second symbol to be demodulated and the reference symbol

If it is

And the reference symbol is D or C, the current second symbol to be demodulated is decided as level C. If it is

And the reference symbol is a, the current second symbol to be demodulated is determined to be level a. If it is

Or

And the reference symbol is D or C, the current second symbol to be demodulated is decided as level a. If it is

Or

And the reference symbol is a, the current second symbol to be demodulated is determined to be level C. And after the judgment, setting the second symbol which is currently demodulated as the reference symbol.

Note that since a symbol having an amplitude of 0 does not have phase information, a symbol having a level of 0 cannot be used as a reference signal. Therefore, if a symbol which completes demodulation before the second symbol to be currently demodulated is a symbol with amplitude 0, another symbol which completes demodulation before the second symbol and has amplitude different from 0 can be used as a reference symbol to complete demodulation. That is to say, in the embodiment of the present application, except for the symbol with the amplitude of 0, other demodulated symbols may be used as reference symbols to participate in the demodulation of the next symbol to be demodulated. It should be understood that if the first symbol to be demodulated is the second symbol after the demodulation process is started, there is no reference symbol at this time, so the formal demodulation should start with the first symbol having the first level that completes demodulation according to amplitude. Taking fig. 5 as an example, it should be assumed that starting from the demodulation of level D, a symbol having a D level may be taken as a reference symbol.

Fig. 7 is another constellation diagram of a baseband I/Q signal in an embodiment of the present application. In some possible embodiments, there may be level non-linear distortion in the original baseband signal input to the transmitting end device, and adjacent levels are not equally spaced. For example, the level distribution of the PAM4 signal without distortion is (1, 2,3, 4), and the level distribution of the PAM4 signal after distortion is (0.5, 1.4, 2.5, 3.6). According to the level adjustment method introduced in the embodiment shown in fig. 2, the level distribution of the PAM4 signal after level adjustment is (-1, -0.1, 1, 2.1), and at this time, the constellation diagram of the baseband I/Q signal after coherent demodulation by the receiving end device is shown in fig. 7. Due to the effect of the asynchronization of the transmit and receive carriers, the trace of the baseband I/Q signal will appear as a circle of 3 different radii. Level a and level C are on the same radius circle, and level D is on the largest radius circle. The demodulation rules for level a, level C and level D are the same as the differential demodulation method described above with reference to fig. 5. The ring formed by level B near the origin also carries information of I/Q phase, which may also be used as a reference symbol in some scenarios. For example, when the radius of the circle where B is located is much larger than the signal noise, i.e. the signal-to-noise ratio is higher, the demodulation method of level B is the same as the demodulation method of level D in the example of fig. 5, and the symbol of level B after demodulation can be used as the reference symbol. However, in the case that the radius of the circle where B is located is not much different from the noise in the signal, the phase of the symbol with level B is easily interfered by the additive noise, so that a large error occurs in the phase to interfere the demodulation of the subsequent symbol.

Fig. 8 is another constellation diagram of a baseband I/Q signal in an embodiment of the present application. In some possible embodiments, the original baseband signal input to the transmitting end device may also be a PAM8 signal. When there is level nonlinear distortion, the level distribution of the PAM8 signal is (0.52,1.41,2.52,3.63,4.5,5.45,6.52,7.48), which is named A, B, C, D, E, F, G, H. According to the level adjustment method introduced in the embodiment shown in fig. 2, the level distribution of the PAM8 signal after level adjustment is (-2.91, -2.02, -0.91,0.2,1.07,2.02,3.09,4.05), and the constellation diagram of the baseband I/Q signal after coherent demodulation by the receiving end device is shown in fig. 8. Due to the non-linear distortion of the original baseband signal, the I/Q signals corresponding to the level B and the level F form an overlapped circular track under the influence of the asynchronization of the transmitting and receiving carriers. The I/Q signals corresponding to level C and level E form two very closely spaced rings, and a similar situation occurs between level a and level G. The signal demodulation method corresponding to the level H is the same as the demodulation method of the level D in the example of fig. 5. The demodulation of level B and level F is the same as that of level a and level C in the example of fig. 5 described above. The demodulation method for level D is the same as that for level B in the example of fig. 7. Under the influence of signal noise, the ring formed by the level C and the level E becomes difficult to distinguish due to broadening, and the corresponding signs cannot be distinguished accurately by using amplitude information. Thus, level C and level E still use the same demodulation as level a and level C described above in the example of fig. 5. The difference is that when the symbol is judged to be level C or level E according to the level amplitude, an amplitude interval containing the level C and the level E is used for judgment, and as long as the level amplitude of the symbol is in the interval, the symbol is judged to correspond to the level C or the level E. Similarly, the demodulation of level a and level G is also similar.

The above description has been introduced for the signal processing methods applied to the transmitting end device and the receiving end device, respectively. The following describes a specific implementation manner by respectively combining structures of the sending end device and the receiving end device.

Fig. 9 is a schematic diagram of a first structure of a sending end device in an embodiment of the present application. As shown in fig. 9, the transmitting-end device includes a modulation module 901 and a transmission module 902. The modulation module 901 is configured to perform the operation of step 201 in the embodiment shown in fig. 2. The sending module 902 is configured to perform the operation of step 202 in the embodiment shown in fig. 2. The modulation module 901 modifies the level distribution of the original baseband signal by modulating the original baseband signal, thereby constructing a specific level distribution. Reference may be made to the description of the specific level distribution in step 201, and details are not described herein. It should be noted that the structure of the modulation module 901 can be implemented in many different ways, which are described below separately.

The implementation mode is as follows: and after the carrier modulation, the level of the original baseband signal is adjusted by means of carrier injection.

Fig. 10 is a schematic diagram of a second structure of a sending-end device in an embodiment of the present application. As shown in fig. 10, the modulation module 901 includes a carrier generation device 1001, a carrier modulation device 1002, a gain adjustment device 1003, and a carrier injection device 1004. Specifically, the carrier generating device 1001 is configured to locally generate a first carrier signal with a specific frequency, and the first carrier signal may be divided into two paths and output to the carrier modulating device 1002 and the gain adjusting device 1003, respectively. Wherein the first carrier signal may be a terahertz carrier signal. The carrier generation device 1001 may be formed by a crystal oscillator element, a frequency multiplier, and a phase-locked loop circuit, and may further include an amplification circuit to generate a high-power carrier. The carrier modulation device 1002 is configured to modulate an input original baseband signal onto a first carrier signal to obtain an original modulated signal. The gain adjustment device 1003 is configured to perform gain adjustment on the first carrier signal to obtain a second carrier signal, where the first carrier signal and the second carrier signal have the same frequency but different amplitudes. The gain adjustment device 1003 may be an amplifier or an attenuator with adjustable gain. The carrier injection device 1004 is configured to generate a target modulation signal according to the original modulation signal and the second carrier signal. It should be understood that the carrier energy in the original modulation signal can be specifically adjusted by means of carrier injection to obtain the target modulation signal, which is equivalent to adjusting the level of the original baseband signal to obtain the target baseband signal respectively. The carrier injection means 1004 may generate a target modulation signal from the original modulation signal and the second carrier signal.

In a possible implementation, the carrier modulation device 1002 may be a radio frequency switch. Fig. 11 is a schematic diagram of carrier modulation performed by the rf switch in the embodiment of the present application. As shown in fig. 11, the on and off of the rf switch corresponds to the level of the original baseband signal, by which the amplitude of the first carrier signal can be adjusted. It should be understood that in practical applications, the rf switch is not limited to the on and off states shown in fig. 11, for example, the original baseband signal is a PAM4 signal, and the on degree of the rf switch may correspond to 4 different levels of the PAM4 signal. In another possible implementation, the carrier modulation device 1002 may also be a mixer, where the original baseband signal and the first carrier signal are multiplied together to implement carrier modulation.

In one possible implementation, the carrier injection device 1004 may be a power combiner, and the power combiner is configured to perform power combining on the original modulation signal and the second carrier signal to obtain the target modulation signal. In another possible embodiment, the carrier injection device 1004 may also be a bias voltage adjusting device, and the bias voltage adjusting device may determine a bias voltage according to the second carrier signal and load the bias voltage on the original modulation signal to obtain the target modulation signal. It should be noted that a specific implementation manner of the carrier injection device 1004 may be selected based on the implementation manner of the carrier modulation device 1002, and the application is not limited specifically. For example, if the carrier modulation device 1002 employs a radio frequency switch, the carrier injection device 1004 may employ a power combiner. For another example, if the carrier modulation device 1002 uses a mixer to mix the original modulation signals into a pair of differential signals, the carrier injection device 1004 may use a bias voltage adjustment device to inject the second carrier into the original modulation signals by applying different bias voltages to the differential signals of the original modulation signals to obtain the target modulation signals.

Optionally, the modulation module 901 may further include a phase adjustment device 1005. The phase of the carrier frequency bins in the original modulated signal may vary significantly due to group delay. Therefore, in order to construct the level distribution of the target baseband signal introduced in the above embodiment, it is also necessary to adjust the phase of the second carrier signal by the phase adjustment device 1005. It should be understood that the phase adjusting device 1005 may be specifically a phase shifter or an adjustable phase shifter, and may also be a delay line or an adjustable delay line with a specific length, which is not limited herein. It should be noted that, in the above embodiment that uses the radio frequency switch, the phase of the carrier is not adjusted, the baseband signal corresponding to the original modulation signal may be all positive levels, and the phase of the second carrier signal may be adjusted by the phase adjusting device 1005, so that the phase difference between the second carrier signal and the carrier frequency point in the original modulation signal is 180 °. The carrier injection device 1004 performs inverse power synthesis on the second carrier signal and the original modulation signal to obtain a target modulation signal. Fig. 12 is a schematic diagram of the inverse phase power combining in the embodiment of the present application. As shown in fig. 12, the level of the baseband signal can be changed by inverse power combining. The implementation mode using the mixer can adjust the phase of the carrier, and the phase adjusting device 1005 can adjust the phase of the second carrier signal, so that the phase difference between the second carrier signal and the carrier frequency point in the original modulation signal is 0 °. The carrier injection device 1004 performs coherent power synthesis on the second carrier signal and the original modulation signal to obtain a target modulation signal.

The implementation mode two is as follows: the level of the original baseband signal is adjusted and then carrier modulation is carried out.

Fig. 13 is a schematic diagram of a third structure of a sending-end device in this embodiment. As shown in fig. 13, the modulation module 901 includes a level adjustment device 1301, a carrier generation device 1302, and a carrier modulation device 1303. Specifically, the level adjusting device 1301 is used to adjust the level of the original baseband signal to obtain the target baseband signal. The carrier generation means 1302 is configured to generate a carrier signal. The carrier modulation device 1303 is configured to modulate a target baseband signal onto a carrier signal to obtain a target modulation signal. The level adjusting device 1301 includes a dc power supply 13a, a voltage adjusting device 13b, and a combiner 13c. The voltage regulator 13b is used to regulate the voltage output from the dc power supply 13 a. The combiner 13c is configured to couple the adjusted voltage with the original baseband signal to obtain a target baseband signal. In another possible embodiment, a bias voltage adjusting device may be used instead of the voltage adjusting device 13b and the combiner 13c, for example, when the original baseband signal is a pair of differential signals, the bias voltage adjusting device may adjust the bias voltage applied by the dc power supply 13a on the original baseband signal to obtain the target baseband signal.

In this way, the original baseband signal can be directly subjected to level adjustment to construct the level distribution of the target baseband signal introduced in the above embodiment, and then the target baseband signal is subjected to carrier modulation to obtain the target modulation signal. The carrier modulation device 1303 may be a mixer, and the target baseband signal and the carrier signal are multiplied in the mixer to implement carrier modulation. Due to the multiplication characteristic of the mixer, the symbol polarity of the target baseband signal is mapped into the phase information of the carrier signal, i.e. the phase information of the carrier signal can represent the level polarity of the target baseband signal.

Fig. 14 is a schematic diagram of a first structure of a receiving end device in the embodiment of the present application. As shown in fig. 14, the receiving-end apparatus includes a receiving module 1401, a carrier generating device 1402, an I/Q mixer 1403, an amplitude detecting module 1404, a phase detecting module 1405, and a demodulating module 1406. Specifically, the receiving module 1401 is configured to receive a target modulation signal from a transmitting end device. The carrier generation means 1402 is used to generate a carrier signal of a predetermined frequency. The I/Q mixer 1403 performs quadrature mixing on the target modulation signal with the carrier signal to obtain an I/Q signal. The amplitude detection module 1404 is used for performing amplitude detection on the I/Q signal to obtain the level amplitude of each symbol in the target baseband signal. The phase detection module 1405 is configured to perform phase detection on the I/Q signal to obtain a phase of each symbol in the target baseband signal, so as to calculate a phase difference between every two adjacent symbols. The demodulation module 1406 is used to demodulate the signal according to the information output from the amplitude detection module 1404 and the phase detection module 1405 to recover the original baseband signal. The demodulating module 1406 is specifically configured to perform the operations of step 604 and step 605 in the embodiment shown in fig. 6, which are not described herein again. It should be noted that the present application does not limit the specific implementation of the amplitude detection module 1404, the phase detection module 1405 and the demodulation module 1406. For example, the amplitude detection module 1404 and the phase detection module 1405 may be implemented with digital op-amp circuits or in digital signal processors. For example, the amplitude detection module 1404 may be an envelope detector or a power detector, etc., and the phase detection module 1405 may be a phase detector. The demodulation module 1406 may be implemented with digital state machine circuitry or with a digital signal processor.

Fig. 15 is a schematic diagram of a second structure of a receiving end device in an embodiment of the present application. As shown in fig. 15, the receiving-end apparatus includes a receiving module 1501, an envelope detector 1502, a delay adjustment device 1503, a mixer 1504, a phase detector 1505, and a demodulation module 1506. Specifically, the receiving module 1501 is configured to receive a target modulation signal from a transmitting end device. The target modulation signal output by the receiving module 1501 may be divided into two paths, where the first path is used for amplitude detection and the second path is used for phase detection. The envelope detector 1502 may perform level detection on the first target modulation signal to obtain a level amplitude of each symbol in the target baseband signal. It should be understood that devices such as power detectors, schottky Barrier Diodes (SBDs), and Gilbert Cell mixers (Gilber Cell mixers) may also be employed to achieve similar functionality as the envelope detector 1502. The second path of target modulation signal may be further divided into two paths, wherein one path is output to the mixer 1504 after being delayed by the delay adjustment device 1503, and the other path is directly output to the mixer 1504 without being delayed. It should be understood that the present embodiment may employ a fixed delay, and may also employ an adjustable delay, which is not limited herein.

The delayed signal R1 is mixed with the undelayed signal R2 by the mixer 1504 to output a baseband signal with differential phase. The signal R1 is denoted as R1 (t) = S (t + D) cos (wt + Φ). The signal R2 is represented as R2 (t) = S (t + D) cos (w (t + D) + Φ). Where S (t) is the baseband signal, D is the delay, w is the carrier signal, and φ is an unknown carrier phase. The baseband signal after mixing is B (t) = R1 (t) R2 (t) = S (t) S (t + D) cos (wD). Since the frequency of the carrier signal w is much greater than the symbol rate F of the data transmission. Therefore, the delay D can be set to a value that satisfies wD =2N pi for the closest one to 1/F, when B (t) = S (t) S (t + D). The phase detector 1505 is used to extract the phase in the signal B. At the correct sampling instant of the symbol, S (t) and S (t + D) have only two levels of polarity, positive and negative. Therefore, the output of the phase detector 1505 also has only two phase values, 0 and pi. When the S (t) and S (t + D) levels are the same polarity, the phase detector 1505 outputs a 0. When the S (t) and S (t + D) levels are of opposite polarity, the phase detector 1505 outputs pi. The demodulation module 1406 is used for demodulating according to the information output by the envelope detector 1502 and the phase detector 1505 to recover the original baseband signal. The demodulation module 1406 is specifically configured to perform the operations of step 604 and step 605 in the embodiment shown in fig. 6, which are not described herein again.

Fig. 16 is a schematic diagram of a third structure of a receiving end device in this embodiment. In some possible embodiments, the signal received by the receiving end device may be affected by inter-Symbol interference (ISI), and the error code of the signal may be seriously degraded. In order to improve the demodulation performance of the baseband signal, based on the structure shown in fig. 14, as shown in fig. 16, the receiving end device may further include an equalizer 1407. The equalizer 1407 may perform channel equalization on the I/Q signal to compensate for inter-symbol interference generated during transmission. The Equalization function may be implemented by using Forward Equalization (FFE) or Continuous Time Linear Equalization (Continuous Time Linear Equalization). The equalized signal may be demodulated normally by the demodulation module 1406. In addition, in the case that the transceiving end signal clocks are not synchronized, the receiving end device may also perform clock recovery through the clock recovery module 1408 after extracting the amplitude of the I/Q signal. It will be appreciated that the equalizer 1407 and clock recovery module 1408 described above may also be implemented in a digital signal processor. It should be noted that the receiving end device in the embodiment of the present application may implement the function of a coherent receiver, and besides the above listed devices, the receiving end device may further include other devices such as a dispersion compensator and a phase recovery module, which is not limited herein.

Fig. 17 is a schematic structural diagram of a communication system in an embodiment of the present application. The communication system includes a transmitting-end device 1701 and a receiving-end device 1702. The sending-end device 1701 is configured to perform some or all of the operations in the embodiment shown in fig. 2. The sink device 1702 is configured to perform some or all of the steps in the embodiment shown in fig. 6. Specifically, the transmitting device 1701 may be the transmitting device described in any of the embodiments of fig. 9, 10, or 13. The sink device 1702 may be the sink device described in any of the embodiments of fig. 14, fig. 15, or fig. 16.

In this embodiment, the sending end device may process the baseband signal to adjust the level of each symbol in the baseband signal, so as to obtain a specific signal format suitable for differential demodulation. Under the framework that the receiving end equipment adopts coherent reception, aiming at the specific signal format, the receiving end equipment can finish demodulation by adopting a differential demodulation method according to the amplitude information and the phase information of the signal without depending on carrier synchronization. By the method, carrier synchronization and data pilot frequency increase are not needed, differential coding is also not needed, and the complexity and the power consumption of implementation are reduced.

Finally, it should be noted that: the above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A signal processing method, comprising:

a sending end device modulates an original baseband signal to obtain a target modulation signal, wherein a level set of the target baseband signal corresponding to the target modulation signal includes a positive level and a negative level, the level set includes at least one first level and does not include a second level, the polarity of the first level is opposite to that of the second level, the difference between the amplitude of the first level and the amplitude of the second level is less than or equal to a preset value, the level set at least includes a third level and a fourth level, the polarity of the third level is opposite to that of the fourth level, and the difference between the amplitude of the third level and the amplitude of the fourth level is less than or equal to the preset value;

and the sending end equipment sends the target modulation signal to receiving end equipment.

2. The method of claim 1, wherein the total number of magnitudes for the levels in the set of levels is less than 32.

3. Method according to claim 1 or 2, characterized in that the difference between the number of positive levels and the number of negative levels in the set of levels is greater than 0 and less than 32.

4. The method according to any one of claims 1 to 3, wherein the step of modulating the original baseband signal by the transmitting end device to obtain the target modulation signal comprises:

the sending end equipment carries out carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulation signal;

the sending end device generates the target modulation signal according to the original modulation signal and a second carrier signal, wherein the frequency of the first carrier signal is the same as the frequency of the second carrier signal, and the amplitude of the first carrier signal is different from the amplitude of the second carrier signal.

5. The method of claim 4, wherein the first carrier signal and the second carrier signal are terahertz carrier signals.

6. The method according to claim 4 or 5, wherein the step of the sending end device performing carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulated signal comprises:

and the sending end equipment modulates the original baseband signal to a first carrier signal through a radio frequency switch to obtain the original modulation signal.

7. The method according to claim 4 or 5, wherein the step of the sending end device performing carrier modulation according to the first carrier signal and the original baseband signal to obtain an original modulated signal comprises:

and the sending end equipment carries out carrier modulation on the first carrier signal and the original baseband signal through a mixer to obtain the original modulation signal.

8. The method according to any one of claims 4 to 7, wherein the generating, by the transmitting end device, a target modulation signal from the original modulation signal and a second carrier signal comprises:

and the sending end equipment performs power synthesis on the original modulation signal and the second carrier signal through a power synthesizer to obtain the target modulation signal.

9. The method according to any one of claims 4 to 7, wherein the generating, by the sending end device, a target modulation signal from the original modulation signal and a second carrier signal comprises:

and the sending end equipment determines a bias voltage according to a second carrier signal, and loads the bias voltage on the original modulation signal to obtain the target modulation signal.

10. The method according to any one of claims 1 to 3, wherein the step of modulating the original baseband signal by the transmitting end device to obtain the target modulation signal comprises:

the sending end equipment adjusts the level of the original baseband signal to obtain the target baseband signal;

and the sending end equipment carries out carrier modulation according to a third carrier signal and the target baseband signal to obtain the target modulation signal.

11. The method of claim 10, wherein the step of the sending end device performing carrier modulation according to a third carrier signal and the target baseband signal to obtain a target modulation signal comprises:

and the sending end equipment carries out carrier modulation on the third carrier signal and the target baseband signal through a mixer to obtain the target modulation signal.

12. The method of claim 10 or 11, wherein the adjusting, by the sending-end device, the level of the original baseband signal to obtain the target baseband signal comprises:

and the sending end equipment adjusts the voltage output by the direct-current power supply through a voltage adjusting device, and couples the adjusted voltage with the original baseband signal to obtain the target baseband signal.

13. The method of claim 10 or 11, wherein the adjusting the level of the original baseband signal by the transmitting device to obtain the target baseband signal comprises:

and the sending end equipment adjusts the bias voltage loaded on the original baseband signal by the direct-current power supply through a bias voltage adjusting device to obtain the target baseband signal.

14. A sending terminal device is characterized by comprising a modulation module and a sending module;

the modulation module: the modulation method comprises the steps that a level set of a target baseband signal corresponding to the target modulation signal comprises a positive level and a negative level, the level set comprises at least one first level and does not comprise a second level, the polarity of the first level is opposite to that of the second level, the difference between the amplitude of the first level and the amplitude of the second level is smaller than or equal to a preset value, the level set at least comprises a third level and a fourth level, the polarity of the third level is opposite to that of the fourth level, and the difference between the amplitude of the third level and the amplitude of the fourth level is smaller than or equal to the preset value;

the sending module: and the target modulation signal is used for sending the target modulation signal to a receiving end device.

15. The transmitting device of claim 14, wherein a total number of magnitudes of levels in the level set is less than 32.

16. The transmitting-end device of claim 14 or 15, wherein the difference between the number of positive levels and the number of negative levels in the level set is greater than 0 and less than 32.

17. The sending end device according to any one of claims 14 to 16, wherein the modulation module includes a carrier generation means, a gain adjustment means, a carrier modulation means, and a carrier injection means;

the carrier generation device: for generating a first carrier signal;

the carrier modulation device: the original modulation signal is obtained by carrying out carrier modulation according to the first carrier signal and the original baseband signal;

the gain adjusting device: the gain adjustment module is used for performing gain adjustment on the first carrier signal to obtain a second carrier signal, wherein the frequency of the first carrier signal is the same as that of the second carrier signal, and the amplitude of the first carrier signal is different from that of the second carrier signal;

the carrier injection device: for generating the target modulation signal from the original modulation signal and a second carrier signal.

18. The transmitting-end device according to claim 17, characterized in that the first carrier signal and the second carrier signal are terahertz carrier signals.

19. The transmitting-end device according to claim 17 or 18, characterized in that the carrier modulation means comprises a radio frequency switch;

the radio frequency switch: and the original baseband signal is modulated onto a first carrier signal to obtain the original modulated signal.

20. The transmitting-end apparatus according to claim 17 or 18, characterized in that the carrier modulation means includes a mixer;

the mixer: and the original modulation signal is obtained by performing carrier modulation on the first carrier signal and the original baseband signal.

21. The transmitting device according to any of claims 17 to 20, characterised in that the carrier injection means comprises a power combiner;

the power combiner: and the second carrier signal is used for carrying out power synthesis on the original modulation signal and the second carrier signal to obtain the target modulation signal.

22. The transmitting end device according to any of claims 17 to 20, wherein the carrier injection means comprises a bias voltage adjusting means;

the bias voltage adjusting device: and the circuit is used for determining a bias voltage according to the second carrier signal and loading the bias voltage on the original modulation signal to obtain the target modulation signal.

23. The sending end device according to any one of claims 14 to 16, wherein the modulation module includes a level adjustment means, a carrier generation means, and a carrier modulation means;

the level adjustment device: the target baseband signal is obtained by adjusting the level of the original baseband signal;

the carrier generation device: for generating a third carrier signal;

the carrier modulation device: and the target modulation signal is obtained by carrying out carrier modulation according to the third carrier signal and the target baseband signal.

24. The transmitting-end device of claim 23, wherein the carrier modulation means includes a mixer;

the mixer: and the third carrier signal and the target baseband signal are subjected to carrier modulation to obtain the target modulation signal.

25. The transmitting-side apparatus according to claim 23 or 24, wherein the level adjusting means includes a dc power supply, a voltage adjusting means, and a combiner;

the direct-current power supply comprises: for outputting a voltage;

the voltage regulating device: for adjusting the magnitude of the voltage:

the combiner comprises: and the voltage regulator is used for coupling the regulated voltage and the original baseband signal to obtain the target baseband signal.

26. The sender apparatus according to claim 23 or 24, wherein the level adjusting means comprises a dc power supply and a bias voltage adjusting means;

the direct-current power supply comprises: for loading a bias voltage on the original baseband signal;

the bias voltage adjusting device: for adjusting the bias voltage to obtain the target baseband signal.

27. A communication system, comprising the transmitting-end device and the receiving-end device according to any one of claims 14 to 26, wherein the receiving-end device comprises a receiving module, an amplitude detection module, a phase detection module, and a demodulation module;

the receiving module: the device is used for receiving a modulation signal from a sending end device;

the amplitude detection module: the amplitude detection is carried out on the modulation signal to obtain the level amplitude of each symbol in a baseband signal corresponding to the modulation signal;

the phase detection module: the phase detection is carried out on the modulation signal to obtain the phase difference between every two adjacent symbols in the baseband signal;

the demodulation module: demodulating a first symbol according to a level amplitude of the first symbol, the first symbol including a symbol having the first level and a symbol having a level of 0 in the baseband signal;

demodulating the second symbol to be demodulated according to a phase difference between a reference symbol and the second symbol to be demodulated, wherein the second symbol includes symbols except the first symbol in the baseband signal, the reference symbol is a symbol which completes demodulation before the second symbol to be demodulated, and the reference symbol does not include a symbol with a level of 0.