CN113395229A - Coherent demodulation method and device suitable for pi/4-DQPSK and readable storage medium - Google Patents
Coherent demodulation method and device suitable for pi/4-DQPSK and readable storage medium Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/22—Demodulator circuits; Receiver circuits
- H04L27/227—Demodulator circuits; Receiver circuits using coherent demodulation
- H04L27/2271—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses only the demodulated signals
- H04L27/2273—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses only the demodulated signals associated with quadrature demodulation, e.g. Costas loop
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/22—Demodulator circuits; Receiver circuits
- H04L27/227—Demodulator circuits; Receiver circuits using coherent demodulation
Abstract
The invention discloses a coherent demodulation method, equipment and a readable storage medium suitable for pi/4-DQPSK, wherein the method comprises the steps of receiving sampling processing, two-path demodulation judgment and carrier loop tracking, receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, and respectively carrying out I-path demodulation processing and Q-path demodulation processing on the digital intermediate frequency signal by utilizing orthogonal local carriers, wherein the result obtained by multiplying the inphase pi/4 phase integer multiple in the I-path demodulation processing and the result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection and are used for tracking and regulating the local carrier after loop filtering. The invention is beneficial to reducing the envelope fluctuation of the modulation signal, the demodulation method realizes the demodulation conversion of the pi/4-DQPSK modulation signal and effectively demodulates the information by a full digitalization processing mode, and simultaneously, the invention also has good carrier tracking capability and good noise resistance.
Description
Technical Field
The present application relates to the field of mobile and satellite communications technologies, and in particular, to a coherent demodulation method and apparatus suitable for pi/4-DQPSK, and a readable storage medium.
Background
In the technical field of mobile communication and satellite communication, a signal modulation mode is selected to be matched with the channel characteristics of signal transmission, and a modulation signal suitable for channel transmission is obtained. In the prior art, the maximum phase jump of a QPSK signal modulation mode is pi, the spectral envelope fluctuation is large, and the spectral distortion generated by nonlinear amplification is easily caused.
In addition, in the QPSK signal modulation scheme, the degradation of demodulation performance is more seriously affected as the frequency difference increases during the synchronization of the received carrier. Therefore, there is a need for an improved signal modulation and reception method to reduce and eliminate the deterioration of demodulation performance due to frequency difference and improve the anti-noise performance of signal reception.
Disclosure of Invention
Based on this, the embodiments of the present invention provide a coherent demodulation method, device and readable storage medium suitable for pi/4-DQPSK, which solve the problem of spectrum distortion caused by a large spectrum envelope waveguide in the prior art for pi/4-DQPSK modulation signal reception and demodulation, and overcome the problem of demodulation performance degradation caused by an increased frequency difference.
In order to solve the above technical problem, an embodiment of the present application provides a coherent demodulation method suitable for pi/4-DQPSK, and a specific technical scheme is as follows: the method comprises the following steps: receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal; two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, in-phase pi/4 phase integral multiple multiplication, phase difference calculation, in-phase-pi/4 phase rotation and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, quadrature pi/4 phase integral multiple multiplication, phase difference calculation, quadrature-pi/4 phase rotation and judgment; and carrier loop tracking, wherein a result obtained by multiplying the in-phase pi/4 phase integer multiple in the I-path demodulation processing and a result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection, and the local carrier is tracked and regulated after loop filtering.
Preferably, the step of generating the pi/4-DQPSK-modulated radio frequency signal from the transmitting end includes: the transmitted data is converted from serial to parallel, and converted from one serial data sequence to two parallel data sequences,corresponding to an in-phase channel data sequence ikAnd orthogonal channel data sequence qkK represents the serial number of data; differential phase encoding using said in-phase channel data sequence ikAnd orthogonal channel data sequence qkCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t); signal modulation, said in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vkAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.
Preferably, the in-phase channel modulation sequence u is obtained by calculating according to the phase difference between the front and rear code elementsk(t) and an orthogonal channel modulation sequence vk(t) are respectively:
wherein the content of the first and second substances,
representing the front-to-back symbol phase difference.
Preferably, the processing method of multiplying the in-phase pi/4 phase integer multiples includes: obtaining a baseband pi/4-DQPSK in-phase component through baseband forming and filtering, taking an information symbol in the baseband as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the baseband pi/4-DQPSK in-phase component to obtain a result that the baseband DQPSK in-phase component is
(ii) a The processing method for multiplying the integral multiple of the orthogonal pi/4 phase comprises the following steps: obtaining a base band pi/4-DQPSK orthogonal component through base band forming filtering, taking an information symbol in the base band as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the base band pi/4-DQPSK orthogonal component to obtain a result that the base band DQPSK orthogonal component is
(ii) a Wherein the content of the first and second substances,
。
preferably, the phase error detection comprises: the baseband DQPSK in-phase component
And baseband DQPSK quadrature component
And performing combination calculation to obtain an error as follows:
will the error
And the signal is input into a loop filter for filtering and then input into a numerical control oscillator to track and regulate a local carrier.
Preferably, the calculated phase difference in the I-path demodulation processing is:
the calculated phase difference in the Q-path demodulation processing is:
preferably, the in-phase-pi/4-phase rotation in the I-path demodulation process is:
the quadrature-pi/4 phase rotation in the Q-way demodulation process is:
preferably, the decision in the I-path demodulation processing and the decision in the Q-path demodulation processing correspond to:
the invention also provides a coherent demodulation device suitable for pi/4-DQPSK, which comprises a memory, a processor and a coherent demodulation program suitable for pi/4-DQPSK, stored in the memory and operable on the processor, wherein when being executed by the processor, the coherent demodulation program of pi/4-DQPSK realizes the steps of the coherent demodulation method suitable for pi/4-DQPSK.
The invention also provides a readable storage medium, on which a coherent demodulation program applicable to pi/4-DQPSK is stored, which when executed by a processor implements the steps of the coherent demodulation method applicable to pi/4-DQPSK as described above.
The embodiment of the application has the following beneficial effects: the invention discloses a coherent demodulation method, equipment and a readable storage medium suitable for pi/4-DQPSK, wherein the method comprises the steps of receiving sampling processing, two-path demodulation judgment and carrier loop tracking, receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, and respectively carrying out I-path demodulation processing and Q-path demodulation processing on the digital intermediate frequency signal by utilizing orthogonal local carriers, wherein the result obtained by multiplying the inphase pi/4 phase integer multiple in the I-path demodulation processing and the result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection and are used for tracking and regulating the local carrier after loop filtering. The invention is beneficial to reducing the envelope fluctuation of the modulation signal, the demodulation method realizes the demodulation conversion of the pi/4-DQPSK modulation signal and effectively demodulates the information by a full digitalization processing mode, and simultaneously, the invention also has good carrier tracking capability and good noise resistance.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of an embodiment of a coherent demodulation method suitable for π/4-DQPSK according to the present invention;
FIG. 2 is a modulation block diagram of a transmitting end in another embodiment of the coherent demodulation method applicable to π/4-DQPSK according to the present invention;
FIG. 3 is a receiving end receiving demodulation block diagram in another embodiment of the coherent demodulation method applicable to π/4-DQPSK according to the present invention;
FIG. 4 is a carrier tracking simulation diagram of another embodiment of the coherent demodulation method applicable to π/4-DQPSK according to the present invention;
fig. 5 is a schematic structural diagram of a coherent demodulation apparatus suitable for pi/4-DQPSK in a hardware operating environment according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terms "comprising" and "having," and any variations thereof, as appearing in the specification, claims and drawings of this application, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or modules is not limited to the listed steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and "third," etc. are used to distinguish between different objects and are not used to describe a particular order.
For a better understanding of the above technical solutions, exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As shown in fig. 1, fig. 1 is a flowchart of an embodiment of a coherent demodulation method applicable to pi/4-DQPSK in the present invention, in this embodiment, the coherent demodulation method applicable to pi/4-DQPSK includes the following steps:
step S1, receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal;
step S2, two paths of demodulation judgment, namely, I path demodulation processing and Q path demodulation processing are respectively carried out on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, in-phase pi/4 phase integral multiple multiplication, phase difference calculation, in-phase-pi/4 phase rotation and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, quadrature pi/4 phase integral multiple multiplication, phase difference calculation, quadrature-pi/4 phase rotation and judgment;
and step S3, carrier loop tracking, wherein the result obtained by multiplying the in-phase pi/4 phase integer multiple in the I-path demodulation processing and the result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection, and the local carrier is tracked and regulated after loop filtering.
Communication technology has developed to present day, and a plurality of communication systems are available, and different communication systems can be selected according to different environments and specific situations. Since the spectrum characteristic of the baseband signal is not suitable for channel transmission, frequency conversion modulation is required to obtain a signal suitable for channel transmission. The maximum phase jump of the traditional QPSK modulation signal is pi, and the amplitude of the spectral envelope fluctuation is large. pi/4-DQPSK (pi/4-ShiftDifferenceniallyEncodedQuadrature PhaseShiftKeying) is an improved modulation mode based on QPSK, and the embodiment of the coherent demodulation method suitable for pi/4-DQPSK can realize that the maximum phase jump of a pi/4-DQPSK modulated radio-frequency signal at a transmitting end is only 3 pi/4, so that the spectrum distortion generated by the envelope fluctuation and nonlinear amplification of the modulated signal is obviously reduced, and the spectrum characteristic is better.
Preferably, since pi/4-DQPSK adopts differential coding, the invention uses coherent demodulation and needs to perform carrier recovery during the receiving process. And, in the received carrier synchronization, if there is a frequency difference between the frequency of the local oscillator and the carrier frequency of the signal
Then within one symbol, there will be
The bit error rate of the system is increased when the phase drift of the phase is reduced
I.e. a frequency deviation of 2.5% of the symbol rate, there will be a phase difference of 9 deg. within one symbol period, at a bit error rate of 10-5This phase difference causes performance deterioration of about 1dB, and the performance deterioration is more affected as the frequency difference increases. Therefore, when the system is implemented, measures are taken to reduce the frequency difference between the frequency of the local oscillator and the signal carrier frequency, and the coherent demodulation method suitable for pi/4-DQPSK is adopted by the invention to eliminate the performance deterioration caused by the frequency difference and improve the anti-noise performance of the system.
Preferably, with respect to step S1 in fig. 1, a signal processing procedure of the transmitting end is shown in conjunction with fig. 2. At a transmitting end, data of the transmitting end is processed in a pi/4-DQPSK phase modulation manner, please refer to fig. 2, and fig. 2 is a modulation block diagram of the transmitting end in an embodiment of a coherent demodulation method applicable to pi/4-DQPSK in the present invention. Specifically, the method for generating the pi/4-DQPSK modulation radio frequency signal of the transmitting end comprises the following steps:
step S11, the transmitted data is converted from serial to parallel, and one serial data sequence is converted into two parallel data sequences corresponding to the same-phase channel data sequence ikAnd orthogonal channel data sequence qkK represents the serial number of data;
step S12, differential phase encoding, using the in-phase channel data sequence ikAnd orthogonal channel data sequence qkCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t)；
Step S13, signal modulation, the in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vkAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.
Preferably, referring to step S11 and referring to fig. 2, data is input at the transmitting end, the input data is serial-to-parallel converted at serial/parallel converting unit 101, and serial/parallel converting unit 101 performs serial-to-parallel conversion on the input one-way serial data sequence (b)1b2…bk…) into two parallel data sequences, which are respectively in-phase channel data sequences ikAnd orthogonal channel data sequence qkAnd k represents the sequence number of data.
Preferably, with respect to step S12 and in conjunction with fig. 2, the two-way parallel data sequence output by the serial/parallel conversion unit 101 is: in-phase channel data sequence ikAnd orthogonal channel data sequence qkInput to the signal conversion unit 102 for differential phase conversion to obtain a phase difference between front and rear code elements, and then the phase difference between the front and rear code elements is used to calculate an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t) and output.
Preferably, the in-phase channel data sequence ikAnd orthogonal channel data sequence qkAn implementation method for obtaining the phase difference between the front and rear code elements by performing differential phase transformation is shown in table 1, and the table 1 is a pi/4-DQPSK differential phase transformation method.
TABLE 1 Pi/4-DQPSK differential phase transformation method
Preferably, Table 1 is only one preferred embodiment, with the preceding and following symbol phase differences
With in-phase channel data sequence ikAnd orthogonal channel data sequence qkThe value combination of (1) can also have other corresponding relations, which are all included in the protection scope of the application, as shown in table 2, table 2 is another conversion method of pi/4-DQPSK differential phase.
TABLE 2 π/4-DQPSK differential phase alternative transformation method
In practical application, only one of the transformation methods needs to be determined for use, and correspondingly, the transformation method specifically adopted by the transmitting end needs to be determined at the receiving end. It can be seen that after the data at the transmitting end is modulated by pi/4-DQPSK, the phase jump is only
The maximum phase jump of the modulation signal is 3 pi/4, so that the spectral distortion generated by the envelope fluctuation and the nonlinear amplification of the modulation signal can be obviously reduced, and the modulation signal has better spectral characteristics.
Preferably, a front-to-back symbol phase difference is obtained
After that, also canTo further utilize the front-to-back symbol phase difference
Respectively calculating to obtain in-phase channel modulation sequences uk(t) and an orthogonal channel modulation sequence vk(t)：
Preferably, regarding step S13, in conjunction with fig. 2, the in-phase channel modulation sequence u output by the signal conversion unit 102 isk(t) and an orthogonal channel modulation sequence vk(t) are inputted to first baseband shaping filter 1031 and second baseband shaping filter 1032, respectively, and shaped and filtered, and in-phase channel modulation sequence u is obtainedk(t) and an orthogonal channel modulation sequence vk(t) after shaping and filtering, multiplying the carrier waves with orthogonal transmitting end carriers respectively and then adding the multiplied carrier waves, wherein the transmitting end carriers are divided into two orthogonal paths of outputs which correspond to the two paths of outputs respectively
And
one path originating carrier
The first multiplier 1041 multiplies the waveform signal output by the first baseband shaping filter 1031, and the other path of the originating carrier wave
The waveform signal output from the second baseband shaping filter 1032 is multiplied by a second multiplier 1042. Then, the results output by the first multiplier 1041 and the second multiplier 1042 are added by the adder 105 to obtain a pi/4-DQPSK modulated radio frequency signal finally generated by modulation.
The above description is about the specific implementation process of step S1 in fig. 1 at the originating end, and the following description is about the specific demodulation and reception process at the receiving end.
Preferably, with respect to steps S2 and S3 in fig. 1, the signal processing procedure at the receiving end is shown in connection with fig. 3. Preferably, referring to fig. 3, as shown in fig. 3, the I-path demodulation process includes an in-phase multiplier 2011, an in-phase baseband shaping filter 2021, an in-phase pi/4 phase multiplier 2031, an in-phase difference calculator 2041, an in-phase-pi/4 phase rotator 2051 and an in-phase decider 2061, and the I-path demodulation process in fig. 1 performs in-phase local carrier multiplication, baseband shaping filtering, in-phase pi/4 phase integral multiple multiplication, phase difference calculation, in-phase-pi/4 phase rotation and decision respectively; the Q-path demodulation process includes an orthogonal multiplier 2012, an orthogonal baseband shaping filter 2022, an orthogonal pi/4 phase multiplier 2032, an orthogonal phase difference calculator 2042, an orthogonal-pi/4 phase rotator 2052, and an orthogonal decision device 2062, and the Q-path demodulation process in fig. 1 is respectively performed with orthogonal carrier multiplication, baseband shaping filtering, orthogonal pi/4 phase integer multiple multiplication, phase difference calculation, orthogonal-pi/4 phase rotation, and decision.
Specifically, the processing method of multiplying the in-phase pi/4 phase integer multiple by the orthogonal pi/4 phase integer multiple includes:
step S21, the processing method of multiplication by pi/4 phase integer multiples in phase includes: obtaining a baseband pi/4-DQPSK in-phase component through baseband forming and filtering, taking an information symbol in the baseband as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the baseband pi/4-DQPSK in-phase component to obtain a result that the baseband DQPSK in-phase component is
；
Step S22, the processing method of orthogonal pi/4 phase integer multiplication includes: obtaining a base band pi/4-DQPSK orthogonal component through base band forming filtering, taking an information symbol in the base band as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the base band pi/4-DQPSK orthogonal component to obtain a result that the base band DQPSK orthogonal component is
(ii) a Wherein n is7 or n = 0.. 7.
Preferably, the purpose of the above processing procedure is to convert a pi/4-DQPSK signal into a DQPSK signal, so that the received signal needs to be subjected to phase rotation according to n pi/4 (n = 1.. 7 or n = 0.. 7) by using an information symbol as a unit, and after the pi/4-DQPSK signal is converted into a DQPSK signal, a QPSK carrier tracking loop is adopted to realize carrier tracking of the received signal.
The mapping relationship of phase coding of pi/4-DQPSK is shown in Table 1, the mapping relationship of phase coding of DQPSK is shown in Table 3, and Table 3 shows the logical relationship of phase coding of DQPSK.
TABLE 3DQPSK phase encoding logic relationship
From the modulation relationships in tables 1 and 3, pi/4-DQPSK increases pi/4 phase rotation over DQPSK for each mapping, so that a pi/4-DQPSK carrier tracking loop can be implemented in such a way:
sequentially offsetting n pi/4 (n =1, 7 or n =0, 7) phases in the received signals according to the information symbol as a unit, namely eliminating n pi/4 rotation of a pi/4-DQPSK system, changing pi/4-DQPSK modulation signals into DQPSK signals, and then realizing carrier tracking of the pi/4-DQPSK by using a carrier tracking loop.
Preferably, referring to fig. 3 for step S3, as shown in fig. 3, the I-path demodulation process includes an in-phase pi/4 phase multiplier 2031 and an orthogonal pi/4 phase multiplier 2032, the results processed by the in-phase pi/4 phase multiplier 2031 and the orthogonal pi/4 phase multiplier 2032 are input to the phase error detector 207 for phase error detection, then loop filtering is performed by the loop filter 208, and two paths of orthogonal local carriers are generated and output by the numerically controlled oscillator 209 (NCO), wherein one path of local carrier is a local carrier
The signal is input to an in-phase multiplier 2011 to be processed by down-conversion of an in-phase carrier, and the other local carrier
The input signal is input to an in-phase multiplier 2012 to be subjected to down-conversion processing of the quadrature carrier. Specifically, the phase error detection step includes:
step 31, the baseband DQPSK in-phase component
And baseband DQPSK quadrature component
And performing combined calculation to obtain an expression of phase error detection as follows:
step 32, comparing the error with the reference value
And the signal is input into a loop filter for filtering and then input into a numerical control oscillator to track and regulate a local carrier.
Preferably, referring to fig. 3, as can be seen from fig. 3, the phase error detection process is implemented by the phase error detector 207 to obtain the error
：
Then, the error signal is subjected to loop filtering by a loop filter 208, and two paths of orthogonal local carriers are generated by a numerically controlled oscillator 209, and are respectively used for carrier synchronization tracking of the in-phase branch and the quadrature branch.
Preferably, after the local carrier synchronization at the receiving end, the synchronized value is:
to this end, we have obtained a DQPSK signal without frequency difference, the information being also contained in the phase difference. Specifically, the step of calculating the phase difference includes:
step S23, the calculated phase difference in the I-path demodulation processing is:
in step S24, the calculated phase difference in the Q-path demodulation processing is:
preferably, referring to fig. 3, as shown in fig. 3, the in-phase difference calculator 2041 de-differentiates the demodulated signal in the I-path demodulation process, so as to obtain the signal
，
Substituting into a difference formula, and then carrying out differential solution to obtain:
preferably, referring to fig. 3, as shown in fig. 3, the demodulated signal in the Q-path demodulation process is de-differentiated by the quadrature phase difference calculator 2042, so as to obtain the difference
，
After substituting into the difference formulaAnd (5) solving difference to obtain:
preferably, will again
And
a phase shift is performed.
Step S25, the in-phase-pi/4-phase rotation in the I-path demodulation processing is:
step S26, converting the Q path
Performing an orthogonal-pi/4 phase rotation to obtain:
preferably, referring to fig. 3, as shown in fig. 3, the in-phase-pi/4 phase rotator 2051 performs-pi/4 phase rotation on the result obtained after the difference is removed in the I-path demodulation processing, so as to obtain:
preferably, referring to fig. 3, as shown in fig. 3, the quadrature-pi/4 phase rotator 2052 performs-pi/4 phase rotation on the result obtained after the de-difference in the Q-path demodulation processing, so as to obtain:
therefore, the mapping relation of the DQPSK is realized, and the corresponding common QPSK mapping relation is obtained.
Preferably, the first and second electrodes are formed of a metal,
and
the polarity decision rule of (1) is shown in table 4, and table 4 is a DQPSK signal demodulation decision rule.
TABLE 4DQPSK signal demodulation decision rule
Preferably, according to table 4, the following decision methods are used to respectively decide the result after the in-phase difference calculator in the I-path demodulation process and the result after the quadrature phase difference calculator in the Q-path demodulation process, and the results are:
to this end, for
And
the original information can be recovered by the judgment.
Therefore, the invention realizes the DQPSK modulation based on pi/4 phase at the transmitting end based on the corresponding relation in the table 1, the maximum phase jump is 3 pi/4, and the invention has smaller envelope fluctuation. In the receiving end processing process, due to the adoption of the processing method of in-phase pi/4 phase integral multiple multiplication and the processing method of orthogonal pi/4 phase integral multiple multiplication, the processing process can convert pi/4-DQPSK signals into DQPSK signals, and then realizes the conversion from demodulated DQPSK signals to demodulated DQPSK signals through pi/4 phase rotation processing in I-path demodulation processing and-pi/4 phase rotation processing in Q-path demodulation processingAdjust the QPSK conversion, thereby directly comparing the data to the data when making a decision
And
and the original information can be recovered by judging.
In order to verify the technical effect of the invention, simulation verification is carried out, and the simulation parameter is that the sampling rate is fs=80MHz, carrier frequency fcThe rate of information symbols is 4Kbit/s, the frequency difference is 200Hz, the tracked frequency difference is shown in fig. 4, and it can be seen from fig. 4 that the loop can normally lock to the frequency difference of the carrier, and the correctness of the scheme is verified.
In addition, the invention also provides a coherent demodulation device of pi/4-DQPSK, which comprises a memory, a processor and a coherent demodulation program of pi/4-DQPSK stored in the memory and capable of running on the processor, wherein the coherent demodulation program of pi/4-DQPSK is executed by the processor to realize the steps of the coherent demodulation method suitable for pi/4-DQPSK.
Preferably, the present invention further provides a readable storage medium, on which a coherent demodulation program for pi/4-DQPSK is stored, and the coherent demodulation program for pi/4-DQPSK is executed by a processor to implement the steps of the coherent demodulation method applicable to pi/4-DQPSK as described above. As shown in fig. 5, fig. 5 is a schematic structural diagram of a coherent demodulation apparatus suitable for pi/4-DQPSK in a hardware operating environment according to an embodiment of the present invention.
The coherent demodulation equipment structure suitable for the pi/4-DQPSK of the embodiment of the invention can be a PC, and can also be various satellite communication equipment or mobile communication equipment.
As shown in fig. 5, the coherent demodulation apparatus suitable for pi/4-DQPSK may include: a processor 1001, such as a CPU, a network interface 1004, a user interface 1003, a memory 1005, a communication bus 1002. Wherein a communication bus 1002 is used to enable connective communication between these components. The user interface 1003 may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wireless interface (e.g., a WI-FI interface). The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001.
Those skilled in the art will appreciate that the architecture of the coherent demodulation apparatus adapted for pi/4-DQPSK shown in fig. 5 does not constitute a limitation of the coherent demodulation apparatus adapted for pi/4-DQPSK, and may include more or fewer components than shown, or some components in combination, or a different arrangement of components. The coherent demodulation apparatus suitable for pi/4-DQPSK according to the present embodiment is described below with reference to fig. 5.
As shown in fig. 5, a memory 1005, which is a computer-readable storage medium, may include therein an operating system, a network communication module, a user interface module, and a coherent demodulation program applicable to pi/4-DQPSK.
In the device shown in fig. 5, the network interface 1004 is mainly used for connecting to a backend server and performing data communication with the backend server; the user interface 1003 is mainly used for connecting a client (user side) and performing data communication with the client; the processor 1001 is the control center of the terminal device, connects the various parts of the overall coherent demodulation device suitable for pi/4-DQPSK using various interfaces and lines, by running or executing software programs and/or modules stored in the memory 1005, and calling the coherent demodulation program suitable for pi/4-DQPSK stored in the memory 1005, and performs the following operations:
the method comprises the following steps: receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal; two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, in-phase pi/4 phase integral multiple multiplication, phase difference calculation, in-phase-pi/4 phase rotation and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, quadrature pi/4 phase integral multiple multiplication, phase difference calculation, quadrature-pi/4 phase rotation and judgment; and carrier loop tracking, wherein a result obtained by multiplying the in-phase pi/4 phase integer multiple in the I-path demodulation processing and a result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection, and the local carrier is tracked and regulated after loop filtering.
Preferably, the step of generating the pi/4-DQPSK-modulated radio frequency signal from the transmitting end includes: the transmitted data is converted from serial to parallel, and converted from one serial data sequence to two parallel data sequences corresponding to in-phase channel data sequence ikAnd orthogonal channel data sequence qkK represents the serial number of data; differential phase encoding using said in-phase channel data sequence ikAnd orthogonal channel data sequence qkCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t); signal modulation, said in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vkAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.
Preferably, the in-phase channel modulation sequence u is obtained by calculating according to the phase difference between the front and rear code elementsk(t) and an orthogonal channel modulation sequence vk(t) are respectively:
wherein the content of the first and second substances,
representing the front-to-back symbol phase difference.
Preferably, the processing method of multiplying the in-phase pi/4 phase integer multiples includes: obtaining a baseband pi/4-DQPSK in-phase component through baseband forming and filtering, taking an information symbol in the baseband as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the baseband pi/4-DQPSK in-phase component to obtain a result that the baseband DQPSK in-phase component is
(ii) a The processing method for multiplying the integral multiple of the orthogonal pi/4 phase comprises the following steps: obtaining a base band pi/4-DQPSK orthogonal component through base band forming filtering, taking an information symbol in the base band as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the base band pi/4-DQPSK orthogonal component to obtain a result that the base band DQPSK orthogonal component is
(ii) a Wherein the content of the first and second substances,
。
preferably, the phase error detection comprises: the baseband DQPSK in-phase component
And baseband DQPSK quadrature component
And performing combination calculation to obtain an error as follows:
will the error
And the signal is input into a loop filter for filtering and then input into a numerical control oscillator to track and regulate a local carrier.
Preferably, the calculated phase difference in the I-path demodulation processing is:
the calculated phase difference in the Q-path demodulation processing is:
the in-phase pi/4 phase rotation in the I-path demodulation processing is:
the quadrature pi/4 phase rotation in the Q-path demodulation process is:
preferably, the decision in the I-path demodulation processing and the decision in the Q-path demodulation processing correspond to:
the specific implementation of the coherent demodulation device applicable to pi/4-DQPSK of the present invention is substantially the same as the embodiments of the coherent demodulation method applicable to pi/4-DQPSK, and is not described herein again.
It should be understood that reference to "a plurality" herein means two or more. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the device embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, refer to the partial description of the method embodiment.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present application and is not to be construed as limiting the scope of the present application, so that the present application is not limited thereto, and all equivalent variations and modifications can be made to the present application.
Claims (10)
1. A coherent demodulation method suitable for pi/4-DQPSK is characterized by comprising the following steps:
receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal;
two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, in-phase pi/4 phase integral multiple multiplication, phase difference calculation, in-phase-pi/4 phase rotation and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, quadrature pi/4 phase integral multiple multiplication, phase difference calculation, quadrature-pi/4 phase rotation and judgment;
and carrier loop tracking, wherein a result obtained by multiplying the in-phase pi/4 phase integer multiple in the I-path demodulation processing and a result obtained by multiplying the orthogonal pi/4 phase integer multiple in the Q-path demodulation processing are combined for phase error detection, and the local carrier is tracked and regulated after loop filtering.
2. The coherent demodulation method for pi/4-DQPSK according to claim 1, wherein said step of generating pi/4-DQPSK modulated radio frequency signal from the transmitting end comprises:
the transmitted data is converted from serial to parallel, and converted from one serial data sequence to two parallel data sequences corresponding to in-phase channel data sequence ikAnd orthogonal channel data sequence qkK represents the serial number of data;
differential phase encoding using said in-phase channel data sequence ikAnd orthogonal channel data sequence qkCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t)；
Signal modulation, said in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vkAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.
3. The coherent demodulation method for pi/4-DQPSK according to claim 2,
calculating according to the phase difference of the front and the rear code elements to obtain an in-phase channel modulation sequence uk(t) and an orthogonal channel modulation sequence vk(t) are respectively:
wherein the front-to-back symbol phase difference is represented.
4. The coherent demodulation method for pi/4-DQPSK according to claim 3,
the processing method for multiplying the integral multiple of the in-phase pi/4 phase comprises the following steps: obtaining a baseband pi/4-DQPSK in-phase component through baseband forming and filtering, taking an information symbol in the baseband as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the baseband pi/4-DQPSK in-phase component to obtain a result that the baseband DQPSK in-phase component is
；
The processing method for multiplying the integral multiple of the orthogonal pi/4 phase comprises the following steps: obtaining a base band pi/4-DQPSK orthogonal component through base band forming filtering, taking an information symbol in the base band as a unit, circularly taking a value through n pi/4 phase, and multiplying the value by the base band pi/4-DQPSK orthogonal component to obtain a result that the base band DQPSK orthogonal component is
；
Wherein n = 1.. 7 or n = 0.. 7.
5. The coherent demodulation method for pi/4-DQPSK according to claim 4, characterized in that said phase error detection comprises:
the baseband DQPSK in-phase component
And baseband DQPSK quadrature component
And performing combination calculation to obtain an error as follows:
and inputting the error into a loop filter for filtering, and then inputting the error into a numerical control oscillator to track and regulate a local carrier.
6. The coherent demodulation method for π/4-DQPSK as in claim 4,
the calculated phase difference in the I-path demodulation processing is:
the calculated phase difference in the Q-path demodulation processing is:
7. the coherent demodulation method for π/4-DQPSK as in claim 6,
the in-phase-pi/4 phase rotation in the I-path demodulation processing is:
the quadrature-pi/4 phase rotation in the Q-way demodulation process is:
8. the coherent demodulation method for pi/4-DQPSK according to claim 7,
the decision in the I-path demodulation processing and the decision in the Q-path demodulation processing correspond to:
9. a coherent demodulation apparatus adapted for pi/4-DQPSK, characterized in that the coherent demodulation apparatus adapted for pi/4-DQPSK comprises a memory, a processor and a coherent demodulation program adapted for pi/4-DQPSK stored on the memory and executable on the processor, the coherent demodulation program of pi/4-DQPSK being executed by the processor to implement the steps of the coherent demodulation method adapted for pi/4-DQPSK as claimed in any of claims 1 to 8.
10. A readable storage medium, on which a coherent demodulation program adapted to pi/4-DQPSK is stored, wherein the coherent demodulation program adapted to pi/4-DQPSK is executed by a processor to implement the steps of the coherent demodulation method adapted to pi/4-DQPSK according to any of claims 1-8.
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