CN113904901A - Carrier recovery method for multiple bandwidths and modulation modes - Google Patents
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- 238000005070 sampling Methods 0.000 claims abstract description 17
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- 238000001914 filtration Methods 0.000 claims abstract description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
- H04L7/0274—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit with 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
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0063—Elements of loops
- H04L2027/0065—Frequency error detectors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0063—Elements of loops
- H04L2027/0067—Phase error detectors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0044—Control loops for carrier regulation
- H04L2027/0063—Elements of loops
- H04L2027/0069—Loop filters
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Abstract
The invention provides a carrier recovery method facing to various bandwidths and modulation modes, which adopts the same framework to be compatible with various bandwidths and modulation modes on the premise of ensuring the carrier recovery performance, improves the compatibility and the universality of a receiver, combines a multi-rate DDC (direct digital control) and costas loop filtering, and adopts different extraction multiples and phase detectors to realize the carrier recovery of signals with different bandwidths and modulation modes by one framework under the condition of ensuring that the framework is not changed. The invention adopts a unified framework, can uniformly change the sampling into 12 times or 16 times for carrier recovery aiming at different bandwidth signals, has high compatibility and flexibility, can complete the carrier recovery of different modulation signals only by changing the phase discrimination mode of the phase discriminator aiming at different modulation modes, improves the general type of a carrier recovery module, can realize real-time demodulation aiming at the reconnaissance analysis of unknown signals, and solves the problem of carrier recovery of unknown signal demodulation.
Description
Technical Field
The invention relates to the field of digital signal processing, in particular to a carrier recovery method, which can realize carrier recovery of signals with different bandwidths and different modulation modes by adopting a structure.
Background
The communication receiver must recover the modulated signal (analog modulation) or the transmission sequence (digital modulation) generated by the transmitting end as distortion-free as possible in order to achieve communication. Demodulation is generally classified into coherent demodulation and noncoherent demodulation. Coherent demodulation performs better than non-coherent demodulation. However, when the coherent method is used for demodulation, a coherent carrier with the same frequency and phase as the carrier at the transmitting end needs to be constructed, that is, a carrier signal needs to be recovered from a received signal, so that the frequency and the phase of the carriers at the transmitting side and the receiving side are consistent, and the process is called carrier recovery or carrier synchronization. The prior communication system mostly adopts the method of adding the training sequence known by a receiving party in a sending signal for carrier recovery of a receiving end, the method has better performance for the receiver of the known transmitting signal carrier frequency and the training sequence, but for the non-cooperative receiver which can not obtain the transmitting signal carrier frequency and the training sequence, the method of recovering the carrier through the training sequence can not be adopted, so that the application scene is limited. The scheme provides carrier recovery by a loop tracking mode. Currently, other carrier recovery schemes based on loop tracking are mostly designed according to specific signals, and only for signals with a certain specified bandwidth or a specified modulation mode, the schemes are deficient in flexibility and universality. The scheme adopts one structure to realize carrier recovery of different bandwidths and different modulation modes, and improves flexibility and universality.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a carrier recovery method oriented to various bandwidths and modulation modes, which adopts the same framework to be compatible with various bandwidths and modulation modes on the premise of ensuring the carrier recovery performance, thereby improving the compatibility and the universality of a receiver. In order to solve the problems that different carrier recovery architectures are needed for different modulation modes, one carrier recovery architecture corresponds to a single bandwidth, and the like, the multi-rate DDC and costas loop filtering are combined, and under the condition that the architectures are not changed, different decimation multiples and phase detectors are adopted, so that carrier recovery of signals with different bandwidths and modulation modes by one architecture is realized.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
(1) sampling processing is carried out on a received signal by adopting a high-speed ADC with a sampling rate of less than or equal to 310MSPS, wherein the sampling rate is set as fsRealizing that the bandwidth is less than or equal to fsAcquiring a signal, and carrying out quadrature down-conversion to a baseband according to a signal carrier to obtain a baseband signal after down-conversion;
(2) extracting and filtering the baseband signals after the down-conversion according to the actual signal bandwidth, wherein the bandwidths and the extraction multiples are different, and after the final extraction, the sampling rate is N times of the signal bandwidth;
(3) performing costas loop filtering on the extracted in-phase component I and quadrature component Q signals, and recovering the carrier:
3.1) carrying out complex multiplication on the extracted and filtered signal and a carrier signal generated by a local DDS in a phase delta;
3.2) judging the signal modulation type, if the signal modulation type is a QPSK signal and a QAM signal, sending the IQ signal after complex multiplication into a phase discriminator for phase discrimination processing to obtain a carrier phase error theta;
θ＝sign(I)*Q-sign(Q)*I
sign (I) represents a symbol for taking I;
if the signal is an 8PSK signal, executing the step (7);
3.3) multiplying the carrier phase error theta by a loop filter coefficient K2, and adding the product to the previous frequency difference value Dfreq to obtain a new frequency difference value Dfreq':
Dfreq'＝Dfreq+K2*θ
ko is the gain of the voltage controlled oscillator, Kd is the linear gain of the phase discriminator, xi is the damping coefficient, T is 1/Fs, Fs is the sampling rate after extraction, omega is 8 xi B/(1+4 xi)2) Is the undamped oscillation frequency, and B is the loop filter bandwidth, which is related to the symbol rate;
(4) the carrier phase error θ is multiplied by the loop filter coefficient K1, and the product is added to Dfreq, the DDS phase Δ, and the initial phase β, and the resulting value is given as Δ', that is:
Δ'＝β+K1*θ+Δ+Dfreq；
(5) the carrier signal of the local DDS is generated by adopting the updated phase delta', and the carrier signal and the extracted IQ two-path signal are continuously subjected to complex multiplication to complete carrier recovery;
(6) taking the increment of the updated phase delta' as a mark, when the increment fluctuates in a threshold range, considering that the carrier is completely recovered, otherwise, defining the carrier as lost lock and being incapable of being recovered;
(7) aiming at 8PSK signals, changing a phase discrimination algorithm of a phase discriminator to obtain a new carrier phase error theta':
then step 3.3) is entered.
The calculation formula of K2 is as follows:
the calculation formula of K1 is as follows:
the threshold value range is 200 kHz.
The invention has the beneficial effects that:
firstly, a unified architecture is adopted, and carrier recovery can be performed by uniformly changing sampling into 12 times or 16 times aiming at different bandwidth signals, so that compatibility and flexibility are improved.
Secondly, for different modulation modes, the carrier recovery of different modulation signals can be completed only by changing the phase discrimination mode of the phase discriminator, and the general type of the carrier recovery module is improved.
Thirdly, the reconnaissance analysis aiming at the unknown signals can realize real-time demodulation, and the problem of carrier recovery of the unknown signal demodulation is solved.
Drawings
Fig. 1 is an implementation architecture diagram of the present invention.
Fig. 2 is a schematic diagram of carrier recovery.
Fig. 3 is a diagram of a costas loop filter architecture.
FIG. 4 (a) is a drawing of the present invention with Ko 2X 10-12Where Kd is 1, xi is 0.707, Fs is 24MSPS, B is 0.1 times symbol rate, the constellation points before carrier recovery of QPSK signal are compared, and the graph (B) in fig. 4 is 2 × 10 Ko of the present invention-12When Kd is 1, xi is 0.707, Fs is 24MSPS, and B is 0.1 times the symbol rate, the constellation point contrast diagram after carrier recovery of the QPSK signal.
FIG. 5 (a) shows a graph of the present invention with Ko 2X 10-12Where Kd is 1, xi is 0.707, Fs is 24MSPS, B is 0.1 times symbol rate, 8PSK signal constellation point contrast diagram before carrier recovery, fig. 5 (B) is the invention Ko is 2 × 10-12When Kd is 1, xi is 0.707, Fs is 24MSPS, and B is 0.1 times symbol rate, the constellation point contrast diagram after carrier recovery of 8PSK signal.
Fig. 6 is a diagram of carrier recovery effect of the present invention when the local carrier is 9.5MHz and the received signal is 10 MHz.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
The method comprises the following implementation steps:
step 1, adopting a high-speed ADC with a high-speed sampling rate to sample QPSK signals with 10MHz carrier frequency and 2MHz bandwidth, wherein the sampling rate is 240MSPS and the sampling multiple is 120 times, and carrying out orthogonal down-conversion to a baseband;
step 3, performing costas loop filtering on the extracted IQ two-path data, and recovering the carrier
3.1) extracting and filtering the signal, and carrying out complex multiplication on the signal and a carrier signal generated by a local DDS with an initial phase delta being 0;
3.2) sending the IQ data after complex multiplication into a phase discriminator for phase discrimination processing to obtain a carrier phase error theta;
θ＝sign(I)*Q-sign(Q)*I，
sign (I) represents a symbol for taking I;
3.3) multiplying the carrier phase error theta by the loop filter coefficient 2, and adding the carrier phase error theta to the original frequency difference value Dfreq to obtain a new frequency difference value Dfreq':
Dfreq'＝Dfreq+K2*θ
k2 is the loop filter coefficient 2, and the calculation formula is:
Ko＝2×10-12kd ═ 1, ξ ═ 0.707, T ═ 1/Fs, Fs ═ 24MSPS, for the post-decimation sampling rate,
ω＝8ξ*B/(1+4ξ2)，B＝0.1*2MHz＝0.2MHz；；
step 4, multiplying the carrier phase error theta by the loop filter coefficient 1, adding the carrier phase error theta to Dfreq, the DDS phase delta and the initial phase beta, and assigning the obtained value to delta', namely
Δ'＝β+K1*θ+Δ+Dfreq
Wherein K1 is loop filter coefficient 1, and its calculation formula is
Step 5, the local DDS continuously performs complex multiplication on a new carrier signal generated by the updated phase delta and the extracted IQ two-path data to complete carrier recovery;
and 6, marking the increment of the phase delta as a mark, and considering that the carrier wave is completely recovered when the increment fluctuates within the range of 200kHz, wherein the increment is related to the carrier wave and the frequency offset value.
Claims (4)
1. A carrier recovery method facing multiple bandwidths and modulation modes is characterized by comprising the following steps:
(1) by using a system having a sampling rate of 310MS or lessHigh-speed ADC of PS for sampling the received signal at a sampling rate of fsRealizing that the bandwidth is less than or equal to fsAcquiring a signal, and carrying out quadrature down-conversion to a baseband according to a signal carrier to obtain a baseband signal after down-conversion;
(2) extracting and filtering the baseband signals after the down-conversion according to the actual signal bandwidth, wherein the bandwidths and the extraction multiples are different, and after the final extraction, the sampling rate is N times of the signal bandwidth;
(3) performing costas loop filtering on the extracted in-phase component I and quadrature component Q signals, and recovering the carrier:
3.1) carrying out complex multiplication on the extracted and filtered signal and a carrier signal generated by a local DDS in a phase delta;
3.2) judging the signal modulation type, if the signal modulation type is a QPSK signal and a QAM signal, sending the IQ signal after complex multiplication into a phase discriminator for phase discrimination processing to obtain a carrier phase error theta;
θ＝sign(I)*Q-sign(Q)*I
sign (I) represents a symbol for taking I;
if the signal is an 8PSK signal, executing the step (7);
3.3) multiplying the carrier phase error theta by a loop filter coefficient K2, and adding the product to the previous frequency difference value Dfreq to obtain a new frequency difference value Dfreq':
Dfreq'＝Dfreq+K2*θ
ko is the gain of the voltage controlled oscillator, Kd is the linear gain of the phase discriminator, xi is the damping coefficient, T is 1/Fs, Fs is the sampling rate after extraction, omega is 8 xi B/(1+4 xi)2) Is the undamped oscillation frequency, and B is the loop filter bandwidth, which is related to the symbol rate;
(4) the carrier phase error θ is multiplied by the loop filter coefficient K1, and the product is added to Dfreq, the DDS phase Δ, and the initial phase β, and the resulting value is given as Δ', that is:
Δ'＝β+K1*θ+Δ+Dfreq；
(5) the carrier signal of the local DDS is generated by adopting the updated phase delta', and the carrier signal and the extracted IQ two-path signal are continuously subjected to complex multiplication to complete carrier recovery;
(6) taking the increment of the updated phase delta' as a mark, when the increment fluctuates in a threshold range, considering that the carrier is completely recovered, otherwise, defining the carrier as lost lock and being incapable of being recovered;
(7) aiming at 8PSK signals, changing a phase discrimination algorithm of a phase discriminator to obtain a new carrier phase error theta':
then step 3.3) is entered.
2. The carrier recovery method for multiple bandwidths and modulation schemes according to claim 1, wherein: the calculation formula of K2 is as follows:
3. the carrier recovery method for multiple bandwidths and modulation schemes according to claim 1, wherein: the calculation formula of K1 is as follows:
4. the carrier recovery method for multiple bandwidths and modulation schemes according to claim 1, wherein: the threshold value range is 200 kHz.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101674272A (en) * | 2009-10-26 | 2010-03-17 | 西安空间无线电技术研究所 | System and method for recovering high-speed 8PSK carriers parallelly |
| CN107040486A (en) * | 2017-03-28 | 2017-08-11 | 西安电子科技大学 | A kind of any bit rate adaptive QPSK demodulating systems and method |
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- 2021-09-16 CN CN202111096531.1A patent/CN113904901A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101674272A (en) * | 2009-10-26 | 2010-03-17 | 西安空间无线电技术研究所 | System and method for recovering high-speed 8PSK carriers parallelly |
| CN107040486A (en) * | 2017-03-28 | 2017-08-11 | 西安电子科技大学 | A kind of any bit rate adaptive QPSK demodulating systems and method |
Non-Patent Citations (1)
| Title |
|---|
| 姜奇渊;秦开宇;: "基于Cordic算法的MPSK信号载波恢复设计", 中国高新技术企业, no. 05 * |
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