CN113595640B - Signal processing method and device - Google Patents
Signal processing method and device Download PDFInfo
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- CN113595640B CN113595640B CN202010367211.4A CN202010367211A CN113595640B CN 113595640 B CN113595640 B CN 113595640B CN 202010367211 A CN202010367211 A CN 202010367211A CN 113595640 B CN113595640 B CN 113595640B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
Abstract
A signal processing method and apparatus for reducing the effect of dispersion on a transmission signal. The method comprises the following steps: the method comprises the steps that a sending end carries out in-phase quadrature (IQ) phase rotation processing on a first signal to obtain a second signal, and a target signal to be sent to a receiving end is determined based on the second signal and a third signal, wherein the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal. Therefore, the influence of ISI interference on the power of a received signal when constellation points of the received signal are expanded can be changed by changing the relative rotation phase of a baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capacity of the system can be improved, and the influence of dispersion on a transmission signal can be reduced.
Description
Technical Field
The present disclosure relates to the field of communications technologies, and in particular, to a signal processing method and apparatus.
Background
With the continuous expansion of the data center scale and the rapid increase of data traffic, the requirements of interconnection scale and transmission rate between various cabinet devices are also continuously increasing, and a short-distance interconnection system with low cost, low power consumption and high rate becomes a basic application requirement of the market.
Optical fibers and terahertz active cables (terahertz active cable, TAC) with greater transmission bandwidth and lower material costs are gaining more and more attention and application in the market trend of ever-increasing transmission rate demands. The optical fiber and the TAC can introduce dispersion damage in transmitted light and electromagnetic waves due to the influence of material characteristics and signal transmission modes, so that distortion and distortion of a transmission signal occur. Since the TAC has several orders of magnitude larger dispersion coefficient and transmission loss than the optical fiber, the influence of dispersion damage thereof becomes more serious.
In order to reduce cost and power consumption, a transceiver module of the short-range interconnection system generally uses a simple modulation and demodulation method, for example, a transmitting end generally uses a non-return-to-zero (NRZ) or 4 pulse amplitude modulation (pulse amplitude modulation, pam 4) mode to modulate signals, and a receiving end uses a Direct Detector (DD) mode to demodulate signals. Since the signal processing capability of the short-range interconnection system is very limited, serious degradation of system performance occurs when channel impairments such as chromatic dispersion are faced by the transmission line. For example, dispersion can lead to pulse broadening such that inter-symbol interference (ISI) occurs in the received symbol sequence, and crosstalk from adjacent symbols can further degrade the signal-to-interference-plus-noise ratio (signal to interference plus noise ratio, SINR) of normal symbols beyond noise, resulting in symbol decisions with bit errors. When ISI increases to some extent, the eye of the received signal may be closed, causing communication disruption.
At present, an anti-dispersion method such as equalization is generally used to avoid the above problems, however, the use of the anti-dispersion method such as equalization is very costly, and there is no simple anti-dispersion method in the amplitude modulation-direct detection system.
Disclosure of Invention
The application provides a signal processing method and a device thereof, which are used for providing a signal processing method to reduce the influence of dispersion on a transmission signal.
In a first aspect, the present application provides a signal processing method, the method comprising: the transmitting end carries out in-phase quadrature (IQ) phase rotation processing on the first signal to obtain a second signal, and determines a target signal to be transmitted to the receiving end based on the second signal and a third signal; the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.
By the method, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmission signal can be reduced. And moreover, the capacity of resisting chromatic dispersion of the system is improved without depending on equalization processing of a receiving end, so that the implementation complexity and difficulty of the receiving end are greatly simplified. And meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that the system supports a longer transmission distance in the existing dispersion-limited system.
In one possible design, when the first signal is the dc signal and the third signal is the signal to be modulated, the transmitting end determines a target signal based on the second signal and the third signal, and the specific method may be: the sending end combines the second signal and the signal to be modulated into a fourth signal, and carries out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal. Therefore, the influence of ISI interference on the power of a received signal when constellation points of the received signal are expanded can be changed by changing the relative rotation phase of a baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capacity of the system can be improved, and the influence of dispersion on a transmission signal can be reduced.
In one possible design, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulating a carrier signal; the transmitting end determines a target signal based on the second signal and the third signal, and the specific method may be: and the sending end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and the fifth signal and the second signal are combined into the target signal. Therefore, the influence of ISI interference on the power of a received signal when constellation points of the received signal are expanded can be changed by changing the relative rotation phase of a baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capacity of the system can be improved, and the influence of dispersion on a transmission signal can be reduced.
In one possible design, when the first signal is the signal to be modulated and the third signal is the dc signal, the transmitting end determines a target signal based on the second signal and the third signal, and the specific method may be: and the transmitting end combines the second signal and the direct current signal into a sixth signal, and carries out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal. This can improve the system's ability to resist dispersion, thereby reducing the effect of dispersion on the transmitted signal.
In one possible design, the target signal may conform to the following formula:
The method can change the influence of ISI interference on the power of the received signal when expanding constellation points of the received signal by changing the relative rotation phase of a baseband direct current component and the signal to be modulated in the system, thereby improving the anti-dispersion capability of the system and reducing the influence of dispersion on the transmission signal.
In a second aspect, the present application further provides a signal processing apparatus, which may be a transmitting end, and the signal processing apparatus has a function of implementing the transmitting end in the foregoing first aspect or each possible design example of the first aspect. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the functions described above.
In one possible design, the structure of the signal processing apparatus may include a plurality of processing units, for example, a first processing unit and a second processing unit, where the units may perform corresponding functions in the foregoing first aspect or each possible design example of the first aspect, and detailed descriptions in method examples are specifically referred to herein and are not repeated herein.
In one possible design, the signal processing device includes a processor and a transceiver in its structure, and optionally a memory. The transceiver is used for receiving signals and for communicating with other devices in the communication system. The processor is configured to support the signal processing apparatus to perform the respective functions of the above-described first aspect or each of the possible design examples of the first aspect. The memory is coupled to the processor that holds the program instructions and data necessary for the signal processing device.
In a third aspect, embodiments of the present application provide a communication system that may include the above-mentioned transmitting end, receiving end, and the like.
In a fourth aspect, embodiments of the present application provide a computer readable storage medium storing program instructions that, when run on a computer, cause the computer to perform the first aspect of embodiments of the present application and any one of its possible designs. By way of example, computer-readable storage media can be any available media that can be accessed by a computer. Taking this as an example but not limited to: the computer readable medium may include non-transitory computer readable media, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.
In a fifth aspect, embodiments of the present application provide a computer program product comprising computer program code or instructions which, when run on a computer, cause the computer to implement the method in any one of the possible designs of the first aspect described above.
In a sixth aspect, the present application further provides a chip coupled to a memory for reading and executing program instructions stored in the memory to implement the method of any one of the possible designs of the first aspect.
The technical effects of each of the second to sixth aspects and the technical effects that may be achieved by each of the aspects are referred to the technical effects that may be achieved by each of the possible aspects of the first aspect, and the detailed description is not repeated here.
Drawings
Fig. 1 is a schematic diagram of a communication system provided in the present application;
FIG. 2 is a flow chart of a signal processing method provided in the present application;
FIG. 3 is a schematic diagram of a signal processing procedure provided in the present application;
FIG. 4 is a schematic diagram of another signal processing procedure provided herein;
FIG. 5 is a schematic diagram of another signal processing procedure provided herein;
fig. 6 is a block diagram of a transceiver system provided in the present application;
Fig. 7 is a schematic diagram of a signal constellation provided in the present application;
fig. 8 is a schematic diagram of a signal constellation provided in the present application;
fig. 9 is a schematic diagram of a signal constellation provided in the present application;
fig. 10 is a schematic diagram of a signal constellation provided in the present application;
FIG. 11 is a diagram of an amplitude modulation circuit provided herein;
fig. 12 is a schematic diagram of a signal constellation provided in the present application;
fig. 13 is a schematic diagram of a signal constellation provided in the present application;
fig. 14 is a schematic diagram of a signal constellation provided in the present application;
FIG. 15 is a diagram of an amplitude modulation circuit provided herein;
fig. 16 is a circuit diagram of a direct modulation scheme provided in the present application;
fig. 17 is a schematic diagram of a signal constellation provided in the present application;
fig. 18 is a schematic diagram of a signal constellation provided in the present application;
fig. 19 is a schematic structural diagram of a signal processing device provided in the present application;
fig. 20 is a block diagram of a signal processing apparatus provided in the present application.
Detailed Description
The present application will be described in further detail with reference to the accompanying drawings.
The embodiment of the application provides a signal processing method and a device thereof, which are used for providing a signal processing method to reduce the influence of dispersion on a transmission signal. The method and the device described in the present application are based on the same technical concept, and because the principles of solving the problems by the method and the device are similar, the implementation of the device and the method can be referred to each other, and the repetition is not repeated.
Currently, in a scene of using an optical fiber, TAC and the like as transmission materials, a transmitting end adopts an amplitude modulation mode such as NRZ or PAM4 and the like under normal conditions, and the amplitude of a transmitting carrier wave is changed by different information; after the channel transmission, the receiving end extracts the amplitude change from the receiving carrier wave by using a power detection or envelope detection mode, thereby recovering the transmitting signal. However, when the channel is damaged such as dispersion caused by the transmission line, the system performance is seriously deteriorated. For dispersion resistance, the following two schemes are currently adopted:
in one scheme, since the transmitting end and the receiving end have no complex signal processing function, the anti-dispersion method is generally implemented by a non-signal processing mode. For example, the average dispersion coefficient of the whole transmission channel is reduced by inserting a section of anomalous dispersion optical fiber in the transmission channel in a gap manner; or, by controlling parameters such as modulation modes, signal transmission speeds, signal waveforms and the like used by the transmitting end and the receiving end under different transmission distances, the distortion of the received signals caused by chromatic dispersion damage is controlled within a certain degree, so that normal transceiving communication is realized.
In this solution, the essence of this technical approach is to avoid the fatal distortion of the signal quality caused by chromatic dispersion by changing the characteristics of the transmission line itself or limiting the system's ability to use the transmission line. However, the manner in which the characteristics of the transmission line are physically changed may involve alterations and additions to the transmission line design, structure, or materials, resulting in increased costs and increased deployment difficulties. With the increasing demands of applications, this approach of avoiding ISI effects by limiting the system rate is ineffective when the transmission distance and bandwidth requirements approach or are greater than the dispersion control threshold of the transmission line. This disadvantage is particularly pronounced in TAC systems.
In another scheme, signal distortion caused by dispersive ISI is compensated by adding an equalizer at the transmitting end or the receiving end, so that the capability of the communication system for resisting channel impairment is improved. In a high baud rate system, the implementation difficulty of the equalizer increases sharply, and great cost and power consumption are brought.
In summary, both of the above solutions cannot resist chromatic dispersion well and cannot be widely used. Based on the method, an amplitude modulation mode which is relatively insensitive to chromatic dispersion ISI is designed, and the bearing capacity of a direct detection receiving end on the total chromatic dispersion of a transmission system is greatly improved under the condition that ISI compensation technologies such as equalization and the like are not relied on. Thus, the signal processing method provided by the application can be well resistant to chromatic dispersion so as to reduce the influence of chromatic dispersion on a transmission signal.
In the description of this application, the words "first," "second," and the like are used solely for the purpose of distinguishing between descriptions and not necessarily for the purpose of indicating or implying a relative importance or order.
In order to describe the technical solution of the embodiments of the present application more clearly, the following describes the signal method and the device provided in the embodiments of the present application in detail with reference to the accompanying drawings.
Fig. 1 shows a possible architecture of a communication system to which the signal processing method provided by the embodiment of the present application is applicable, where the architecture of the communication system includes a transmitting end and a receiving end, and a transmission line between the transmitting end and the receiving end is an optical fiber, TAC, and the like with a relatively large transmission bandwidth and relatively low material cost.
Illustratively, the transmitting end may be, but not limited to, a transmitting chip that is a pluggable connector (QSPF), or a device or apparatus including the transmitting chip, or a transmitter of a terahertz (THz) communication system, etc.; the receiving end may be, but is not limited to, a receiving chip of a QSPF, or a device or apparatus including the receiving chip, or a receiver of a THz communication system, etc.
The signal processing method provided by the embodiment of the application is suitable for the communication system shown in fig. 1. Referring to fig. 2, the specific flow of the method includes:
The signal to be modulated is a real baseband signal which needs to be sent by the sending end.
In an alternative embodiment, the signal processing procedure of the transmitting end may include at least three examples according to different situations of the first signal and the third signal:
in a first example, when the first signal is the dc signal and the third signal is the signal to be modulated, the transmitting end determines the target signal based on the second signal and the third signal, and the specific method may be: the transmitting end combines the second signal and the signal to be modulated into a fourth signal, and carries out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal (i.e. the modulated signal). For example, the signal processing procedure of the transmitting end to obtain the modulated signal may be as shown in fig. 3.
Specifically, the direct current signal may be changed into a complex baseband signal after IQ phase rotation.
In a second example, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulating a carrier signal; the transmitting end determines a target signal based on the second signal and the third signal, and the specific method may be: the transmitting end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combines the fifth signal and the second signal into the target signal (i.e. the modulated signal). For example, the signal processing procedure of the transmitting end to obtain the modulated signal may be as shown in fig. 4.
In this example, since the carrier signal itself may be regarded as a modulated dc signal, the signal processing shown in fig. 4 in this example may be obtained after exchanging the sequence of the carrier modulation operation and the signal combining operation in fig. 3 in the first example.
Specifically, in this example, the signal to be modulated is modulated by a carrier to obtain a modulated signal (i.e., the fifth signal) in a carrier frequency band; the carrier signal is IQ phase rotated to obtain a bandpass real signal (i.e., the second signal).
In a third example, when the first signal is the signal to be modulated and the third signal is the dc signal, the transmitting end determines a target signal based on the second signal and the third signal, and the specific method may be: the transmitting end combines the second signal and the direct current signal into a sixth signal; and performing carrier modulation on the sixth signal based on the carrier signal to obtain the target signal (i.e., the modulated signal). For example, the signal processing procedure of the transmitting end to obtain the modulated signal may be as shown in fig. 5.
In a specific embodiment, taking the method in the first example as an example, a block diagram of a transceiver system formed by the transmitting end and the receiving end may be shown in fig. 6. Wherein the transmitting end uses the modulation method in the first example to transmit the signal S [ n ]]Modulating (i.e. the signal processing method in the first example) to obtain the target signal cn that the transmitting end needs to transmit to the receiving end](may also be referred to as a transmit signal); the receiving end receives the received signal J [ n ]]Amplified and fed into a self-mixer for detection, wherein the self-mixer can be replaced by other types of Power Detectors (PD) or envelope detectors (envelope detector, ED), and the output obtained by low-pass filtering the detection result is the power |J [ n ] of the received signal ]| 2 Finally, the receiving end judges the signal power through a judging device to recover the corresponding signal powerA signal is transmitted.
Specifically, the anti-dispersion principle applied in the present application may be as follows:
the dispersion of the channel appears as a second order component of the channel phase-frequency response in a signal transmission model, which may correspond to the following equation (1):
R(f)＝S(f)·H(f)＝S(f)·exp(2πj·βLf 2 ) Formula (1);
wherein S (f) and R (f) are the frequency spectrums of the transmission signal and the reception signal, respectively, and H (f) is the frequency response of the entire transmission channel. Wherein the frequency response of the overall transmission channel comprises a channel amplitude-frequency response and a channel phase-frequency response, which may comprise a first order component and a second order component. Here, the influence of the channel amplitude-frequency response is not considered, so that the channel amplitude-frequency fluctuation is not reflected in the formula (1), or the channel amplitude-frequency response is 1 in the formula (1). Also, since the first-order component of the phase-frequency response of the channel affects only the overall transmission delay of the signal in the channel without distorting the signal waveform, for simplicity, it is omitted from formula (1), i.e., only the second-order component exp (2pi j·βlf of the channel phase-frequency response is represented in formula (1) 2 ). In the second-order component of the channel phase-frequency response, β is the dispersion coefficient of the transmission line, and L is the transmission distance, which together determine the total degree of dispersion.
Further, according to the nature of fourier transform, the second-order component of the channel phase-frequency response in equation (1) will appear as a second-order phase change in the channel impulse response in the time domain, which specifically may conform to the following equation (2):
where h (t) is the channel impulse response, A is a complex constant, and α is a coefficient determined by the total level of dispersion in the transmission channel. T in brackets on the right according to equation (2) 2 The component may yield a first characteristic of a second order dispersive time domain channel: the impulse response h (t) of the channel is symmetrical with respect to the channel response at the central position t=0, i.e. the channel impulse at the position t= -t0The impulse response h (-t 0) is equal in magnitude and phase to the channel impulse response h (t 0) at the position of t=t0.
Under limited bandwidth conditions, the channel impulse response of equation (2) exhibits a second characteristic according to the stationary phase principle (principle of stationary phase) that is: the channel impulse response amplitude is larger only near the center position, and the channel impulse response amplitude on both sides outwards is drastically reduced as it is far from the center position.
In the time domain impulse response of a transmission channel, the impulse response coefficient h (0) =a of the center position t=0 is the transmission loss and phase transformation of the main signal (i.e., the signal other than the interference signal); whereas the impulse response coefficient of the non-central position t+.0 corresponds to the ISI interference of the channel. From the two characteristics of the channel impulse response analyzed above, it is known that during the gradual increase of the second-order dispersion effect, a symmetrical ISI interference appears at both sides of the main signal position at the same time, and that due to the characteristic that ISI decays rapidly with distance, the amplitude of two ISI immediately adjacent to both sides of the main signal response increases to be close to the amplitude of the main signal response, the amplitude of the ISI interference increase further outside of the two ISI interference is not large.
If the symbol sequence (i.e. the target signal) sent by the sending end is C [ n ], where the sequence number n is an integer, and after the channel transmission, the symbol sequence (i.e. the received signal) received by the receiving end is J [ n ], then J [ n ] and C [ n ] may conform to the following formula (3):
where h [ i ] represents the discretized channel impulse response, k represents the sequence number of channel ISI spreading on both sides of the center response, and N is channel noise. Because of the symmetry and fast decay characteristics of ISI, equation (3) can be reduced to equation (4) below before ISI spreads widely:
wherein complex number A represents the impulse response coefficient of the main signal, complex number I 1 The interference coefficients representing the two strongest ISI responses, with the other ISI having weaker interference, are collectively referred to as noise term O. The inequality in equation (4) characterizes the upper bound of ISI interference, where the transmitted signals at times n+1 and n-1 exhibit coherent addition, with the ISI interference being the greatest. Finally, through the equation transformation, the relative ISI interference coefficients of adjacent transmitted signals can be represented by amplitude γ and phase θ.
The method improves the anti-dispersion capability of the direct-detection receiver at the receiving end by introducing a DC component with phase bias (i.e. introducing IQ phase rotation) during signal processing. Based on the above principle, the target signal obtained by the signal processing method (i.e. amplitude modulation mode) proposed in the present application may conform to the following formula (5):
Wherein C n]For the target signal (i.e., transmit signal); s [ n ]]The signal to be modulated is a real signal with the mean value of 0; DC is the direct current signal;
is phase offset; f (f) c Is the carrier frequency.
In the above formula (5), the phase offset parameter
Does not change the amplitude of the DC component and thus transmits a signal C [ n ]]Is not changed by the phase bias. Due to S [ n ]]Is a real signal with an average value of 0, and therefore C [ n ]]Can be written as the rightmost complex version of equation (5). At this time, the signal C [ n ] is transmitted in FIG. 6]The baseband signal constellation of (a) may be as shown in fig. 7.
Further, after the transmission through the channel, the reception signal J [ n ] of the reception end may conform to the following formula (6):
wherein the first term in equation (6) is a fixed dc offset component and the second term is a useful signal term after interference by adjacent ISI.
The receiving end obtains the power |J [ n ] of the received signal after detection]| 2 The decision principle of the decision device on the signal power is equivalent to receiving the signal J [ n ] through the constellation diagram]The radius of the circle is used to determine the original signal S [ n ] to be modulated]As shown in fig. 8, after signal processing is performed by the method of the present application, the constellation diagram of the signal received by the receiving end, where four black circles respectively correspond to the signals S [ n ] that send four different values ]And when the power of the signal output by the receiver detector changes, the receiver detector outputs the change range of the power of the signal.
It can be deduced from simple geometric principles that when the direction of spreading ISI interference on constellation points is tangential to the power detection circle, the spreading of ISI spreading on the power detection circle is minimal, and the deterioration of the detection performance of the receiver is minimal. After phase biasing according to this principle, the constellation of the received signal corresponding to equation (6) will change to the one shown in fig. 8.
At this time, J [ n ]]DC component after medium rotation
Is directed exactly orthogonal to the direction of spread of ISI interference versus constellation points.
In the following, the signal processing method provided in the present application is compared with the performance of a standard PAM4 modulation system used in the prior art under the same dispersive channel. At this time, a baseband signal constellation of the transmission signal of the standard PAM4 modulation system used in the related art is shown in fig. 9.
After the channel transmission, the constellation diagram of the received signal and the power variation range of the detector output determined by the receiving end are shown in fig. 10.
At this time, the innermost gray ring in fig. 10 is very close to the immediately adjacent gray ring, and when the decision device decides the transmission signals corresponding to the two rings in a noise environment, the error probability is greatly increased. As can be seen from comparing fig. 10 with fig. 8, the distances between all the rings in fig. 8 are very large, and the signal processing method (amplitude modulation method) of the present application makes the receiving end still maintain relatively high receiving performance under the interference of channel dispersion ISI, and the anti-dispersion performance is greatly improved.
Specifically, as can be seen from the comparison between fig. 10 and fig. 8, by adopting the signal processing method provided by the application, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the amplitude modulation system, so that the anti-dispersion performance of the direct detection receiving system is greatly improved. The system performance is improved without depending on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. And meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that the system supports a longer transmission distance in the existing dispersion-limited system.
In a specific example, the signal processing method using the above formula (5) may be implemented by an amplitude modulation circuit diagram as shown in fig. 11. Specifically, f c Is the carrier frequency of the transmitted signal, cos (f c t) and sin (f) c t) are two orthogonal carrier local oscillators. Decomposing the DC component after IQ phase rotation into real component according to the technical principle of formula (5)
And imaginary component->
And the real component of DC is added to the signal S [ n ] to be modulated in advance]The DC imaginary component is used as a Q-channel signal, and then the IQ modulator is used for realizing carrier modulation and combination.
Note that, the two paths of signals I, Q input by the IQ modulator may be directly constructed by using an analog baseband waveform, or may be calculated in a digital chip to generate a corresponding digital signal and then converted into an analog signal by a digital-to-analog converter (D/a), which is not limited in this application.
In the example shown in fig. 11, assuming that S [ n ] to be transmitted at this time is a 2-bit signal, the signal constellation corresponding to the point a may be as shown in fig. 12; the signal constellation corresponding to the point B may be as shown in fig. 13; the point C can obtain a constellation diagram formed by the I, Q two paths of signals on the I/Q plane when IQ modulation is performed finally, as shown in fig. 14, where the distribution of the constellation diagram shown in fig. 14 is consistent with the distribution of the constellation diagram shown in fig. 7.
In this example, the circuit configuration and operation of the receiving terminal are substantially identical to those of the receiving terminal in fig. 6. It is easily demonstrated by the nature of the vector sum that the DC component, after IQ phase rotation, is per signal C n]The radius of the power circle where the constellation point is located is changed, so as shown in fig. 11, when the decision device at the receiving end performs demodulation decision on the signal, the decision threshold also needs to be according to the phase of the DC rotation at the transmitting end
And (5) adjusting.
DC rotation phase to be configured at a determination transmitting end
In one way, the phase difference θ of the strongest ISI interference coefficient relative to the main signal response coefficient is obtained by channel estimation at the receiving end, and then the required phase ∈is calculated according to the principle of making the DC component after rotation orthogonal to the ISI spreading direction>
In another way, the receiving end detects the output signal eye pattern or detects the bit error rate after demodulation, and performs an optimal search on the required rotation phase, so that the open-close balance of multiple eyes in the signal eye pattern or the bit error rate is the lowest at this time, and at this time, as shown in fig. 11, an eye pattern monitoring or bit error monitoring functional module needs to be added in the receiving end.
In another specific example, the signal processing of the transmitting end includes a DC component IQ phaseThe rotated circuit diagram (which may be referred to as an amplitude modulation circuit diagram) may be as shown in fig. 15. In this example, the real component DC.cos after DC component rotation
In a display manner with the signal S [ n ] to be modulated]Combining, and then obtaining signals after carrier modulation through a single carrier modulator; the addition of the imaginary component after DC rotation is realized by a branch coupling circuit at the rear side of the single carrier modulator. The branch coupling circuit directly takes a modulated carrier wave as an input, and the input carrier wave signal is equivalent to a direct current signal subjected to carrier wave modulation at the moment; the branch coupling circuit includes a phase shifter and a gain controller (which may be an amplifier or an attenuator, etc.) operating in the carrier frequency band. Wherein the phase shifter shifts the phase so that the carrier signal corresponding to the DC imaginary component and the carrier signal in the modulated signal are exactly 90 degrees different at the later signal combining point, and the gain controller adjusts the gain so that the carrier amplitude of the branch satisfies the formula (5) >
Is a relationship of (3).
In yet another specific example, a circuit diagram (which may be referred to as a circuit diagram of a direct modulation scheme) including DC IQ phase rotation in signal processing of the transmitting end may be as shown in fig. 16. The conventional direct modulator can directly control the amplitude of a single-tone carrier signal with gain K according to the value of a signal to be modulated, for example, for microwave signal modulation, the direct modulator can be an electric control switch working in a microwave frequency band; for optical signal modulation, the direct modulator here may be an external modulated laser. The direct modulator directly realizes the effects of DC real component superposition and carrier modulation. While the introduction of the DC imaginary component is still accomplished with a branch coupling circuit structure, the internal structure and function of which are similar to the branch coupling circuit referred to in fig. 15. Assuming that the modulation gain of the direct modulator is 1, the modulation depth of the direct modulator under the minimum value is H, namely the direct modulator when the signal to be modulated takes the minimum valueThe intensity of the output signal is H, then in order to achieve a phase of
The amplification gain in the branch coupling circuit is required to be configured as +.>
In the above examples, the case where IQ rotation is performed on the dc signal is included in the signal processing in the first example and the second example. Due to IQ phase rotation of the dc component, the reference of the rotation is the baseband signal S n to be modulated ]Itself. It can thus be further understood that IQ phase rotation of the relative position of the direct current component in the baseband signal (i.e. the signal to be modulated) and the baseband signal results in the situation in the third example, i.e. the signal processing procedure as shown in fig. 5. In a third example, the direct current signal is not IQ phase rotated any more, but IQ phase rotated to the signal to be modulated, and then combined with the direct current component, and then carrier modulated. Angle of IQ phase rotation
The IQ phase rotation angle for the dc component is the same as in the example described above, but of opposite sign. Taking a 2-bit signal to be modulated as an example, in the modulation process, a signal constellation diagram corresponding to the point a in fig. 5 may be shown in fig. 17; further, after the combination with the dc signal, the constellation corresponding to the B point may be as shown in fig. 18.
Comparing the constellation of fig. 18 with the constellation of fig. 14 described above, it can be seen that the constellation of fig. 18 has only a single rotation relative to the origin, and that the rotation does not affect the normal demodulation and anti-dispersion performance of the system. Thus, the third example and the first example are consistent with the effect of the second example on chromatic dispersion resistance.
By adopting the signal processing method in the embodiment of the application, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmission signal can be reduced. And moreover, the capacity of resisting chromatic dispersion of the system is improved without depending on equalization processing of a receiving end, so that the implementation complexity and difficulty of the receiving end are greatly simplified. And meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that the system supports a longer transmission distance in the existing dispersion-limited system.
Based on the foregoing embodiments, the embodiments of the present application further provide a signal processing apparatus, which is configured to implement the signal processing method provided in the embodiment shown in fig. 2. The signal processing device may be a transmitting end in the above embodiment, and specifically may be a processor in the transmitting end, or a chip system, or a functional module, etc. Referring to fig. 19, the signal processing apparatus 1900 includes a first processing unit 1901 and a second processing unit 1902, where:
The first processing unit 1901 is configured to perform in-phase quadrature IQ phase rotation processing on a first signal to obtain a second signal, where the first signal is one of a signal to be modulated and a direct current signal; the second processing unit 1902 is configured to determine, based on the second signal and the third signal, a target signal that needs to be sent to a receiving end; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.
In an alternative embodiment, when the first signal is the dc signal and the third signal is the signal to be modulated, the second processing unit 1902 is specifically configured to, when determining the target signal based on the second signal and the third signal: and combining the second signal and the signal to be modulated into a fourth signal, and carrying out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal.
In another optional implementation manner, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulating a carrier signal; the second processing unit 1902 is specifically configured to, when determining a target signal based on the second signal and the third signal: and carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combining the fifth signal and the second signal into the target signal.
In yet another alternative embodiment, when the first signal is the signal to be modulated and the third signal is the dc signal, the second processing unit 1902 is specifically configured to, when determining the target signal based on the second signal and the third signal: and combining the second signal and the direct current signal into a sixth signal, and carrying out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal.
By way of example, the target signal may conform to the following equation:
By adopting the signal processing device in the embodiment of the application, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmission signal can be reduced. And moreover, the capacity of resisting chromatic dispersion of the system is improved without depending on equalization processing of a receiving end, so that the implementation complexity and difficulty of the receiving end are greatly simplified. And meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that the system supports a longer transmission distance in the existing dispersion-limited system.
It should be noted that, in the embodiment of the present application, the division of the units is schematic, which is merely a logic function division, and other division manners may be implemented in actual practice. The functional units in the embodiments of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be embodied in essence or a part contributing to the prior art or all or part of the technical solution, in the form of a software product stored in a storage medium, including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a read-only memory (ROM), a random access memory (random access memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Based on the above embodiments, the embodiments of the present application further provide a signal processing apparatus, which is configured to implement the signal processing method shown in fig. 2. The signal processing device may be a transmitting end in the above embodiment, and specifically may be a processor in the transmitting end, or a chip system, or a functional module, etc. Referring to fig. 20, the signal processing apparatus 2000 may include: a transceiver 2001 and a processor 2002. Optionally, the signal processing device 2000 may further include a memory 2003. The memory 2003 may be provided inside the signal processing device 2000 or may be provided outside the signal processing device 2000. Wherein the processor 2002 may control the transceiver 2001 to receive and transmit signals.
In particular, the processor 2002 may be a central processing unit (central processing unit, CPU), a network processor (network processor, NP) or a combination of CPU and NP. The processor 2002 may further comprise a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (programmable logic device, PLD), or a combination thereof. The PLD may be a complex programmable logic device (complex programmable logic device, CPLD), a field-programmable gate array (field-programmable gate array, FPGA), general-purpose array logic (generic array logic, GAL), or any combination thereof.
Wherein said transceiver 2001, said processor 2002 and said memory 2003 are interconnected. Optionally, the transceiver 2001, the processor 2002 and the memory 2003 are connected to each other by a bus 2004; the bus 2004 may be a peripheral component interconnect standard (Peripheral Component Interconnect, PCI) bus or an extended industry standard architecture (Extended Industry Standard Architecture, EISA) bus, among others. The buses may be classified as address buses, data buses, control buses, etc. For ease of illustration, only one thick line is shown in fig. 20, but not only one bus or one type of bus.
In an alternative embodiment, the memory 2003 is used for storing programs and the like. In particular, the program may include program code including computer-operating instructions. The memory 2003 may include RAM, and may also include non-volatile memory (non-volatile memory), such as one or more magnetic disk memories. The processor 2002 executes the application programs stored in the memory 2003 to realize the functions described above, thereby realizing the functions of the signal processing apparatus 2000.
Specifically, the processor 2002 may enable the signal processing apparatus 2000 to implement the signal processing method provided in the embodiment of the present application by performing the following operations: carrying out in-phase quadrature (IQ) phase rotation processing on the first signal to obtain a second signal, and determining a target signal to be sent to a receiving end based on the second signal and a third signal; the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.
In an alternative embodiment, when the first signal is the dc signal and the third signal is the signal to be modulated, the processor 2002 is specifically configured to, when determining the target signal based on the second signal and the third signal: and combining the second signal and the signal to be modulated into a fourth signal, and carrying out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal.
In another optional implementation manner, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulating a carrier signal; the processor 2002 is specifically configured to, when determining the target signal based on the second signal and the third signal: and carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combining the fifth signal and the second signal into the target signal.
In yet another alternative embodiment, when the first signal is the signal to be modulated and the third signal is the dc signal, the processor 2002 is specifically configured to, when determining the target signal based on the second signal and the third signal: and combining the second signal and the direct current signal into a sixth signal, and carrying out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal.
Illustratively, the target signal meets the following formula:
By adopting the signal processing device in the embodiment of the application, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmission signal can be reduced. And moreover, the capacity of resisting chromatic dispersion of the system is improved without depending on equalization processing of a receiving end, so that the implementation complexity and difficulty of the receiving end are greatly simplified. And meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that the system supports a longer transmission distance in the existing dispersion-limited system.
Based on the above embodiments, the present application further provides a computer readable storage medium, where the computer readable storage medium is configured to store a computer program, where the computer may implement any one of the signal processing methods provided in the above method embodiments when the computer program is executed by a computer.
The present application also provides a computer program product, where the computer program product is configured to store a computer program, where the computer program when executed by a computer may implement any one of the signal processing methods provided in the foregoing method embodiments.
The embodiment of the application also provides a chip, which comprises a processor and a communication interface, wherein the processor is coupled with the memory and is used for calling a program in the memory to enable the chip to realize any signal processing method provided by the embodiment of the method.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.
Claims (11)
1. A signal processing method, comprising:
the method comprises the steps that a sending end carries out in-phase quadrature (IQ) phase rotation processing on a first signal to obtain a second signal, wherein the first signal is one of a signal to be modulated and a direct current signal;
the transmitting end determines a target signal to be transmitted to the receiving end based on the second signal and the third signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal;
when the first signal is the direct current signal and the third signal is the signal to be modulated, the transmitting end determines a target signal based on the second signal and the third signal, including: the transmitting end decomposes the second signal into a real component and an imaginary component, and superimposes the real component on the third signal to serve as an I-path signal, and the imaginary component serves as a Q-path signal, and carrier modulation and combination are performed based on the I-path signal and the Q-path signal to obtain the target signal.
2. The method of claim 1, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the transmitting end determines a target signal based on the second signal and the third signal, comprising:
The sending end combines the second signal and the signal to be modulated into a fourth signal;
and the transmitting end carries out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal.
3. The method of claim 1, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulating a carrier signal; the transmitting end determines a target signal based on the second signal and the third signal, including:
the sending end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal;
and the transmitting end combines the fifth signal and the second signal into the target signal.
4. The method of claim 1, wherein when the first signal is the signal to be modulated and the third signal is the dc signal, the transmitting end determines a target signal based on the second signal and the third signal, comprising:
the transmitting end combines the second signal and the direct current signal into a sixth signal;
and the transmitting end carries out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal.
5. A method according to any one of claims 1-3, wherein the target signal corresponds to the formula:
wherein C n]Is the target signal; s [ n ]]The signal to be modulated is a real signal with the mean value of 0; DC is the direct current signal;
is phase offset; f (f) c Is the carrier frequency.
6. A signal processing apparatus, comprising:
the first processing unit is used for carrying out in-phase quadrature (IQ) phase rotation processing on a first signal to obtain a second signal, wherein the first signal is one of a signal to be modulated and a direct current signal;
the second processing unit is used for determining a target signal to be sent to the receiving end based on the second signal and the third signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal;
when the first signal is the direct current signal and the third signal is the signal to be modulated, the second processing unit is specifically configured to, when determining a target signal based on the second signal and the third signal: and decomposing the second signal into a real component and an imaginary component, overlapping the real component into the third signal to serve as an I-path signal, taking the imaginary component as a Q-path signal, and carrying out carrier modulation and combination based on the I-path signal and the Q-path signal to obtain the target signal.
7. The apparatus of claim 6, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the second processing unit is configured to, when determining a target signal based on the second signal and the third signal:
combining the second signal and the signal to be modulated into a fourth signal;
and carrying out carrier modulation on the fourth signal based on the carrier signal to obtain the target signal.
8. The apparatus of claim 6, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulation of a carrier signal; the second processing unit is specifically configured to, when determining a target signal based on the second signal and the third signal:
carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal;
combining the fifth signal and the second signal into the target signal.
9. The apparatus of claim 6, wherein when the first signal is the signal to be modulated and the third signal is the direct current signal, the second processing unit is configured to, when determining a target signal based on the second signal and the third signal:
Combining the second signal and the direct current signal into a sixth signal;
and carrying out carrier modulation on the sixth signal based on the carrier signal to obtain the target signal.
10. The apparatus of any of claims 6-8, wherein the target signal corresponds to the following formula:
wherein C n]Is the target signal; s [ n ]]The signal to be modulated is a real signal with the mean value of 0; DC is the direct current signal;
is phase offset; f (f) c Is the carrier frequency.
11. A computer readable storage medium, characterized in that the computer readable storage medium has stored therein a computer program which, when executed by a computer, causes the computer to perform the method according to any of claims 1-5.
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