CN109714286B - Carrier frequency offset estimation method for Pi/8D8PSK demodulation - Google Patents
Carrier frequency offset estimation method for Pi/8D8PSK demodulation Download PDFInfo
- Publication number
- CN109714286B CN109714286B CN201910028823.8A CN201910028823A CN109714286B CN 109714286 B CN109714286 B CN 109714286B CN 201910028823 A CN201910028823 A CN 201910028823A CN 109714286 B CN109714286 B CN 109714286B
- Authority
- CN
- China
- Prior art keywords
- frequency offset
- frequency
- 8d8psk
- offset estimation
- fft
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The invention provides a carrier frequency offset estimation method for Pi/8D8PSK demodulation, which comprises the steps of carrying out digital orthogonal down-conversion and low-pass filtering on Pi/8D8PSK intermediate-frequency signals to obtain Pi/8D8PSK modulated baseband signals, carrying out bit synchronization operation on the baseband signals by adopting a square timing recovery algorithm, and adding a window function to data after bit synchronization to reduce energy leakage; in order to avoid the frequency resolution ratio not meeting the requirement when the frequency offset is small and the frequency offset estimation precision is deteriorated, performing FFT operation on the windowed data after 16-party operation, performing modulo operation on the FFT operation result, calculating a frequency point corresponding to the maximum value, multiplying the frequency point by the resolution ratio bandwidth, and dividing the frequency point by 16 to obtain a frequency offset estimation value; the number of sampled code elements is properly increased for improving the frequency resolution bandwidth; in order to improve the operation efficiency, the FFTW is called to realize FFT operation, and the improvement of a frequency offset estimation algorithm of DFT is realized. Along with the popularization of the complex algorithm software implementation method, the engineering implementation complexity of the method is greatly reduced. Compared with the existing DFT frequency offset estimation algorithm, the method has the advantages of improving the precision and the efficiency, improving the energy leakage suppression and facilitating the engineering realization.
Description
Technical Field
The invention belongs to the field of wireless communication test, and particularly relates to a carrier frequency offset estimation method for pi/8D8PSK demodulation.
Background
In a wireless communication system, with the rapid development of software radio technology and digital signal processing technology, the all-digital modulation and demodulation technology is widely applied. The Pi/8D8PSK modulation mode has the characteristics of high spectrum utilization rate and small envelope fluctuation, so that the performance of the Pi/8D8PSK modulation mode is superior to that of the 8PSK modulation mode, and the Pi/8D8PSK modulation mode has better spectrum efficiency in a nonlinear channel. The frequency offset of the carrier wave at the receiving end has a very bad influence on a communication system, which not only causes the rotation of constellation points, but also increases the error rate sharply, so that the carrier frequency offset estimation is one of the key links of Pi/8D8PSK demodulation. The current common methods are M-Power frequency offset estimation and frequency offset estimation based on DFT, and the basic idea of the M-Power frequency offset estimation algorithm is to remove modulation information in a received signal by taking the Power M (M is a modulation order of 16), and then remove the influence of a constant phase error through conjugate differential delay, thereby estimating the frequency offset. The implementation block diagram is shown in fig. 1.
C(i)＝S1(i)·S1*(i-1)
Where T is the symbol rate, n is the total data amount, i.e., the number of symbols, imag () is the real part, real () is the imaginary part. The algorithm has high precision, but has limited application range.
The DFT-based frequency offset estimation algorithm estimates the carrier frequency offset point using the DFT spectrum, and the block diagram is shown in fig. 2. The baseband pi/8D8PSK signal after quadrature down-conversion is represented as:
in the formula gT(T-nT) is a symbol pulse signal, T is a symbol period, and the symbol rate is RsAnd f is the carrier frequency offset, namely 1/T.
DFT operation is carried out on the data after bit synchronization, and the actual sampling rate of the data is the code element rate RsThe spectrum will have a peak spectral line at Δ f, and we can estimate the frequency offset Δ f — PointOffset multiplied by the frequency resolution bandwidth RBW by searching the position PointOffset of the maximum spectral line. When Δ f is a positive value (actual frequency f 0)>Carrier frequency fc), the spectral line with the maximum amplitude is positioned between 0 and N/2; when Δ f is negative (actual frequency f 0)<Carrier frequency fc), the spectral line with the maximum amplitude is positioned between N/2 and N-1.
The estimable range of the DFT algorithm is: r is less than or equal to | delta f |s. The algorithm is wide in application range, but the accuracy is not high due to the barrier effect and energy leakage of the algorithm. The estimation precision is related to the number N of FFT points, and the higher N is, the higher precision is and the larger computation amount is.
Disclosure of Invention
The invention provides a carrier frequency offset estimation method for Pi/8D8PSK demodulation, which comprises the steps of carrying out digital orthogonal down-conversion and low-pass filtering on Pi/8D8PSK intermediate-frequency signals to obtain Pi/8D8PSK modulated baseband signals, carrying out bit synchronization operation on the baseband signals by adopting a square timing recovery algorithm, and adding a window function to data after bit synchronization to reduce energy leakage; in order to avoid the frequency resolution ratio not meeting the requirement when the frequency offset is small and the frequency offset estimation precision is deteriorated, performing FFT operation on the windowed data after 16-party operation, performing modulo operation on the FFT operation result, calculating a frequency point corresponding to the maximum value, multiplying the frequency point by the resolution ratio bandwidth, and dividing the frequency point by 16 to obtain a frequency offset estimation value; the number of sampled code elements is properly increased for improving the frequency resolution bandwidth; in order to improve the operation efficiency, the FFTW is called to realize FFT operation, and the improvement of a frequency offset estimation algorithm of DFT is realized.
The invention is realized according to the following technical scheme:
a carrier frequency offset estimation method of Pi/8D8PSK demodulation is characterized by comprising the following steps:
step S1: carrying out digital quadrature down-conversion and low-pass filtering on the Pi/8D8PSK intermediate frequency signal to obtain a Pi/8D8PSK modulated baseband signal X (n):
X(n)＝XI(n)+j*XQ(n)
j represents the imaginary component of the complex signal;
step S2: performing bit synchronization operation on the baseband signal by adopting a square timing recovery algorithm, and firstly calculating the offset position Ph of the maximum sampling point, wherein the range is larger than-1/2 and smaller than 1/2:
x (N) is a baseband signal of Pi/8D8PSK modulation before bit synchronization, in complex form, L is the number of symbols of one frame data, N is the number of sampling points of one symbol, and Ph is Ph +1.0 if Ph is calculated to be less than 0 since Ph range is greater than-1/2 and less than 1/2;
the maximum sampling point of a frame of data is:
InterMax(i)＝(Ph+i)*N+1；i＝0，1，…，L-1
the orthogonal signals after bit synchronization are as follows:
I(i)＝XI(InterMax(i))；i＝0，1，…，L-1
Q(i)＝XQ(InterMax(i))；i＝0，1，…，L-1；
step S3: performing windowing operation on the I (n), Q (n) after bit synchronization to obtain ic (n), Qc (n), a window function is win (n), is generated by Matlab, is of a type of a panning window and has a length of L,
Ic(i)＝I(i)*Win(i)；i＝0，1，…，L-1
Qc(i)＝Q(i)*Win(i)；i＝0，1，…，L-1
the bit-synchronized I (n), Q (n) are written in complex form as follows:
BitSyncSym(n)＝Ic(n)+j*Qc(n)；
j represents the imaginary component of the complex signal;
step S4: operation of the power 16 BitSyncSym (n) on the windowed data16Then, FFT operation is carried out to obtain FFTSym (n), the value of the FFT point number FFT _ Len is L, FFTW is called to realize the FFT operation, and the frequency resolution bandwidth is the code element rate SymSample divided by the FFT _ Len;
step S5: and (3) calculating a module of the FFT operation result FFTSym (n), calculating a frequency point PointOffset corresponding to the maximum value MaxMag of the module, multiplying the PointOffset by the frequency resolution bandwidth, and dividing by 16 to obtain a frequency offset estimation value delta f.
Step S6: performing frequency offset compensation on the bit-synchronized signal by using the frequency offset estimation value Δ f, wherein the bit-synchronized signal bitsym (n) ═ i (n) + j × q (n), so that the frequency offset-compensated signal:
compared with the prior art, the invention has the following beneficial effects:
compared with the existing DFT frequency offset estimation algorithm, the method improves the precision and the efficiency, greatly reduces the complexity, improves the energy leakage inhibition, and is convenient for engineering realization, and the estimation range of the method is as follows: r is less than or equal to | delta f |sAnd/16, the method is very suitable for small frequency deviation.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a block diagram of an implementation of an M-Power frequency offset estimation algorithm;
FIG. 2 is a block diagram of a DFT-based frequency offset estimation algorithm implementation;
fig. 3 is a block diagram of an implementation of carrier frequency offset estimation according to the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
Fig. 3 is a block diagram of a carrier frequency offset estimation implementation of the present invention, and as shown in fig. 3, a Pi/8D8PSK demodulation carrier frequency offset estimation method of the present invention includes the following steps:
step S1: carrying out digital quadrature down-conversion and low-pass filtering on the Pi/8D8PSK intermediate frequency signal to obtain a Pi/8D8PSK modulated baseband signal X (n), and realizing that a system block diagram is shown in FIG. 3;
X(n)＝XI(n)+j*XQ(n)
j represents the imaginary component of the complex signal;
step S2: performing bit synchronization operation on the baseband signal by adopting a square timing recovery algorithm, and firstly calculating the offset position Ph of the maximum sampling point, wherein the range is larger than-1/2 and smaller than 1/2:
x (N) is a baseband signal of Pi/8D8PSK modulation before bit synchronization, in complex form, L is the number of symbols of one frame data, N is the number of sampling points of one symbol, and Ph is Ph +1.0 if Ph is calculated to be less than 0 since Ph range is greater than-1/2 and less than 1/2;
the maximum sampling point of a frame of data is:
InterMax(i)＝(Ph+i)*N+1；i＝0，1，…，L-1
the orthogonal signals after bit synchronization are as follows:
I(i)＝XI(InterMax(i))；i＝0，1，…，L-1
Q(i)＝XQ(InterMax(i))；i＝0，1，…，L-1
step S3: performing windowing operation on the I (n), Q (n) after bit synchronization to obtain ic (n), Qc (n), a window function is win (n), is generated by Matlab, is of a type of a panning window and has a length of L,
Ic(i)＝I(i)*Win(i)；i＝0，1，…，L-1
Qc(i)＝Q(i)*Win(i)；i＝0，1，…，L-1
the bit-synchronized I (n), Q (n) are written in complex form as follows:
BitSyncSym(n)＝Ic(n)+j*Qc(n)；
j represents the imaginary component of the complex signal;
step S4: operation of the power 16 BitSyncSym (n) on the windowed data16Then, FFT operation is carried out to obtain FFTSym (n), the value of the FFT point number FFT _ Len is L, FFTW is called to realize the FFT operation, and the frequency resolution bandwidth is the code element rate SymSample divided by the FFT _ Len;
step S5: and (3) calculating a module of the FFT operation result FFTSym (n), calculating a frequency point PointOffset corresponding to the maximum value MaxMag of the module, multiplying the PointOffset by the frequency resolution bandwidth, and dividing by 16 to obtain a frequency offset estimation value delta f.
Step S6: performing frequency offset compensation on the bit-synchronized signal by using the frequency offset estimation value Δ f, wherein the bit-synchronized signal bitsym (n) ═ i (n) + j × q (n), so that the frequency offset-compensated signal:
the DFT of the complex signal is a single-side spectrum, and when the carrier frequency offset is a positive value, a spectral line with the maximum amplitude is located between 0 and N/2; when the carrier frequency offset is a negative value, the spectral line with the maximum amplitude is positioned between N/2 and N-1, so that the frequency offset value can be effectively estimated by adopting the frequency offset estimation algorithm of FFT, and the positive value and the negative value of the frequency offset can also be estimated.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (1)
1. A carrier frequency offset estimation method of Pi/8D8PSK demodulation is characterized by comprising the following steps:
step S1: carrying out digital quadrature down-conversion and low-pass filtering on the Pi/8D8PSK intermediate frequency signal to obtain a Pi/8D8PSK modulated baseband signal X (n):
X(n)＝XI(n)+j*XQ(n)
j represents the imaginary component of the complex signal;
step S2: performing bit synchronization operation on the baseband signal by adopting a square timing recovery algorithm, and firstly calculating the offset position Ph of the maximum sampling point, wherein the range is larger than-1/2 and smaller than 1/2:
x (N) is a baseband signal of Pi/8D8PSK modulation before bit synchronization, in complex form, L is the number of symbols of one frame data, N is the number of sampling points of one symbol, and Ph is Ph +1.0 if Ph is calculated to be less than 0 since Ph range is greater than-1/2 and less than 1/2;
the maximum sampling point of a frame of data is:
InterMax(i)＝(Ph+i)*N+1；i＝0，1，…，L-1
the orthogonal signals after bit synchronization are as follows:
I(i)＝XI(InterMax(i))；i＝0，1，…，L-1
Q(i)＝XQ(InterMax(i))；i＝0，1，…，L-1；
step S3: performing windowing operation on the I (n), Q (n) after bit synchronization to obtain ic (n), Qc (n), a window function is win (n), is generated by Matlab, is of a type of a panning window and has a length of L,
Ic(i)＝I(i)*Win(i)；i＝0，1，…，L-1
Qc(i)＝Q(i)*Win(i)；i＝0，1，…，L-1
the bit-synchronized I (n), Q (n) are written in complex form as follows:
BitSyncSym(n)＝Ic(n)+j*Qc(n)；
j represents the imaginary component of the complex signal;
step S4: operation of the power 16 BitSyncSym (n) on the windowed data16Then, FFT operation is carried out to obtain FFTSym (n), the value of the FFT point number FFT _ Len is L, FFTW is called to realize the FFT operation, and the frequency resolution bandwidth is the code element rate SymSample divided by the FFT _ Len;
step S5: performing modulo calculation on the FFT operation result FFTSym (n), calculating a frequency point PointOffset corresponding to the maximum value MaxMag of the modulo, multiplying the PointOffset by the frequency resolution bandwidth, and dividing by 16 to obtain a frequency offset estimation value delta f;
step S6: performing frequency offset compensation on the bit-synchronized signal by using the frequency offset estimation value Δ f, wherein the bit-synchronized signal bitsym (n) ═ i (n) + j × q (n), so that the frequency offset-compensated signal:
FreqOffsetBitSym(n)＝BitSym(n)*e-j*2*π*Δf*n。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910028823.8A CN109714286B (en) | 2019-01-11 | 2019-01-11 | Carrier frequency offset estimation method for Pi/8D8PSK demodulation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910028823.8A CN109714286B (en) | 2019-01-11 | 2019-01-11 | Carrier frequency offset estimation method for Pi/8D8PSK demodulation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109714286A CN109714286A (en) | 2019-05-03 |
| CN109714286B true CN109714286B (en) | 2021-06-22 |
Family
ID=66260005
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910028823.8A Active CN109714286B (en) | 2019-01-11 | 2019-01-11 | Carrier frequency offset estimation method for Pi/8D8PSK demodulation |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109714286B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112162153B (en) * | 2020-08-31 | 2023-04-28 | 南京亿杰明信息技术有限公司 | Sine wave signal frequency estimation method based on phase straight line fitting |
| CN113406386B (en) * | 2021-06-23 | 2023-04-25 | 中国电子科技集团公司第二十九研究所 | Signal frequency accurate estimation method based on digital down-conversion |
| CN113542173A (en) * | 2021-07-28 | 2021-10-22 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Carrier frequency offset suppression method, system, medium and device based on automatic frequency control |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101795250A (en) * | 2010-04-16 | 2010-08-04 | 成都天奥信息科技有限公司 | Demodulation method and device of D8PSK (differential 8-ary phase shift keying) modulation signals of VDL (VHF (very high frequency) digital link) communication system |
| CN102790659A (en) * | 2012-07-18 | 2012-11-21 | 福建先创通信有限公司 | Method for transmitting data packet in mobile communication system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8306145B2 (en) * | 2008-03-31 | 2012-11-06 | Sirius Xm Radio Inc. | Overlay modulation of COFDM using phase and amplitude offset carriers |
-
2019
- 2019-01-11 CN CN201910028823.8A patent/CN109714286B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101795250A (en) * | 2010-04-16 | 2010-08-04 | 成都天奥信息科技有限公司 | Demodulation method and device of D8PSK (differential 8-ary phase shift keying) modulation signals of VDL (VHF (very high frequency) digital link) communication system |
| CN102790659A (en) * | 2012-07-18 | 2012-11-21 | 福建先创通信有限公司 | Method for transmitting data packet in mobile communication system |
Non-Patent Citations (2)
| Title |
|---|
| Analytical BER performance in differential n-PSK coherent transmission system influenced by equalization enhanced phase noise;Tianhua Xu et al;《Optics Communications》;20150615;全文 * |
| QPSK信号的矢量分析研究与实现;钱者凤;《信息技术》;20170225;全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109714286A (en) | 2019-05-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109714286B (en) | Carrier frequency offset estimation method for Pi/8D8PSK demodulation | |
| CN102624419B (en) | Carrier synchronization method of burst direct sequence spread spectrum system | |
| CN102546500B (en) | SOQPSK (shaping offset quadrature phase shift keying) carrier synchronization method based on pilot frequency and soft information combined assistance | |
| EP1913747B1 (en) | Fast carrier frequency error estimation algorithm using sychronization sequence | |
| CN109617844B (en) | Carrier synchronization method and system | |
| US7639750B2 (en) | Phase tracking method and device thereof | |
| CN110300079B (en) | MSK signal coherent demodulation method and system | |
| CN111683034B (en) | OFDM-based large Doppler wireless communication time-frequency synchronization method | |
| CN103281280B (en) | Based on the carrier synchronization method of rotation average period map and demodulation Soft Inform ation | |
| CN101490660A (en) | Improved precision CORDIC processor | |
| US9071327B2 (en) | Efficient frequency estimation | |
| JP2008530951A (en) | Demodulator and receiver for pre-encoded partial response signals | |
| CN107579942B (en) | Demodulation method of APSK (amplitude phase Shift keying) modulation signal | |
| CN113037671A (en) | Low-complexity efficient SOQPSK symbol timing and phase joint synchronization algorithm | |
| CN102833204A (en) | Frequency offset estimation implementation method | |
| US8472569B2 (en) | Fine symbol timing estimation | |
| CN102137053A (en) | Method for estimating signal to noise ratio of BPSK (Binary Phase Shift Keying) signal | |
| CN113824666A (en) | Channel estimation method and device for satellite mobile OFDM communication system | |
| CN117544457A (en) | Combined time domain equalization method under CPM modulation | |
| US20070030924A1 (en) | An Iterative Frequency Offset Estimator for PSK Modulation | |
| CN112671684B (en) | Self-adaptive demodulation method of short-time burst BPSK signal | |
| JP4970283B2 (en) | High memory efficiency sliding window addition | |
| US6873666B2 (en) | Circuit and method for symbol timing recovery in phase modulation systems | |
| US7116727B2 (en) | Frequency offset estimation apparatus for intersymbol interference channels | |
| JP3793198B2 (en) | OFDM signal communication system and OFDM signal transmitter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |