CN113132280B - IQ imbalance estimation method - Google Patents

IQ imbalance estimation method Download PDF

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CN113132280B
CN113132280B CN202110406052.9A CN202110406052A CN113132280B CN 113132280 B CN113132280 B CN 113132280B CN 202110406052 A CN202110406052 A CN 202110406052A CN 113132280 B CN113132280 B CN 113132280B
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imbalance
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subsequences
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CN113132280A (en
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孙胤杰
吴义文
黄梅莹
楼红伟
郭昌松
庞浩
李正卫
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Shenzhen Smart Microelectronics Technology Co ltd
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Spl Electronic Technology Co ltd
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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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • 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

Abstract

The invention belongs to the technical field of power line carrier communication, and particularly relates to an IQ imbalance estimation method. Firstly, processing a received radio frequency signal to obtain a differential leader sequence; then, a carrier offset frequency estimated value is obtained according to the differential leader sequence; splitting the differential preamble sequence into at least three differential preamble subsequences, performing simultaneous connection on the differential preamble subsequences, substituting the simultaneous sequences into a carrier offset frequency estimation value, and obtaining a relation between IQ imbalance factors; and finally, obtaining an IQ phase imbalance estimation value and/or an IQ amplitude imbalance estimation value according to the relation between the IQ imbalance factors. After the differential preamble sequence is obtained, the differential preamble sequence is firstly utilized to estimate the carrier offset frequency, and then IQ imbalance is estimated on the basis, so that real-time and accurate estimation of IQ imbalance is realized, accurate compensation and calibration are convenient to carry out, and the cost of a receiver can be effectively saved.

Description

IQ imbalance estimation method
Technical Field
The invention belongs to the technical field of power line carrier communication, and particularly relates to an IQ imbalance estimation method.
Background
The current wireless communication system usually adopts a receiver with a zero intermediate frequency structure for signal reception. The zero intermediate frequency receiver directly down-converts the radio frequency signal to be near zero frequency, has simple structure, high integration level and lower power consumption, and is a receiver structure adopted by a dual-mode communication wireless part of the current power consumer electricity consumption information acquisition system.
Due to the performance limitation of the radio frequency analog device, the zero intermediate frequency receiver has some inherent defects, such as Direct Current (DC) bias caused by local oscillator leakage, IQ imbalance generated by local oscillator signal self-mixing, and the like, which seriously affect the performance of the receiver. IQ imbalance can be interpreted as a phase and amplitude mismatch between the in-phase (I) and quadrature (Q) branches, as evidenced by the lack of a quadrature relationship (90 ° phase difference) between the I and Q signals generated by the local oscillator for mixing, and by the difference in the amplitude gains of the I and Q branches. IQ imbalance may produce image interference signals, causing a reduction in the dynamic range of the receiver, which may affect the demodulation of the baseband signal in severe cases.
Methods for suppressing IQ imbalance mainly include two types: on one hand, from the hardware perspective, a radio frequency analog device with better performance is adopted to overcome IQ imbalance of the receiver, and although the method can fundamentally eliminate IQ imbalance, the volume, the power consumption and the cost of the receiver are increased; on the other hand, digital estimation and compensation technology can be adopted in a baseband to overcome radio frequency defects, the method is low in cost and wide in application range, and is the main research direction of the current IQ imbalance compensation technology, for example, IQ imbalance and channel influence are combined together, but the estimation is carried out again as long as the channel changes, the overhead of the system is increased, and the problem of inaccurate estimation is caused.
Disclosure of Invention
The invention provides an IQ imbalance estimation method, which is used for solving the problems of higher cost caused by compensation from the hardware perspective or inaccurate estimation caused by adopting a digital estimation and compensation technology.
In order to solve the technical problems, the technical scheme and the corresponding beneficial effects of the technical scheme are as follows:
the invention provides an IQ imbalance estimation method, which comprises the following steps:
1) processing a received radio frequency signal to obtain a leader sequence, wherein the leader sequence comprises a carrier frequency offset and an IQ imbalance factor;
2) carrying out differential calculation on the obtained leader sequence to obtain a differential leader sequence;
3) calculating to obtain a carrier offset frequency estimated value according to the differential leader sequence;
4) splitting the differential preamble sequence into at least three differential preamble subsequences, carrying out simultaneous operation on the differential preamble subsequences, and substituting the simultaneous operation result into the carrier offset frequency estimated value obtained in the step 3) to obtain the relation between IQ imbalance factors;
5) and obtaining an IQ phase imbalance estimation value and/or an IQ amplitude imbalance estimation value according to the relation between the IQ imbalance factors.
The beneficial effects of the above technical scheme are: based on the fact that a certain relation exists between carrier offset frequency and IQ imbalance generated in the actual communication process, namely the influence of the carrier offset frequency on the system performance is aggravated by IQ imbalance of a receiver, the method comprehensively considers the influence of the carrier offset frequency and the IQ imbalance, estimates the carrier offset frequency by using a differential preamble sequence after obtaining the differential preamble sequence, and then estimates the IQ imbalance on the basis, thereby realizing real-time and accurate estimation, facilitating accurate compensation and calibration and improving the system performance; moreover, the method is improved from software, and the cost of the receiver can be effectively saved.
Further, in order to accurately implement joint estimation of carrier frequency offset and IQ balance, in step 1), an expression of a preamble sequence including carrier frequency offset Δ f and IQ imbalance factor is as follows:
Figure GDA0003510662450000021
wherein the content of the first and second substances,
Figure GDA0003510662450000022
is a leader sequence; k is 0,1,2, …, NS-1，NSIs the length of the leader sequence; n is the number of FFT points; f. ofsIs the sampling frequency; m isS(k) Is an ideal leader sequence;
Figure GDA0003510662450000023
is mS(k) Complex conjugation of (a); Δ f is a carrier frequency offset; φ and ψ are IQ imbalance factors, and the expression for IQ imbalance factors φ and ψ is:
Figure GDA0003510662450000024
Figure GDA0003510662450000025
wherein, θ is IQ phase imbalance and β is IQ amplitude imbalance.
Further, in step 2), the differential preamble sequence is:
Figure GDA0003510662450000026
wherein d isS(k) Is a differential preamble sequence
Figure GDA0003510662450000027
Ideal differential preamble sequence of, and dS(k)＝mS(k)-mS(k-1)，
Figure GDA0003510662450000028
Is dS(k) Complex conjugation of (a).
Further, in order to accurately calculate the carrier offset frequency estimated value, in step 3), the following method is adopted to calculate the carrier offset frequency estimated value according to the differential preamble sequence:
performing time delay autocorrelation and summation average operation with the length of D on the differential leader sequence, and obtaining the carrier offset frequency estimated value after taking the argument of the operation result, wherein the carrier offset frequency estimated value is as follows:
Figure GDA0003510662450000031
wherein, the first and the second end of the pipe are connected with each other,
Figure GDA0003510662450000032
is a carrier offset frequency estimated value; n is the number of FFT points; f. ofsIs the sampling frequency; k is 0,1,2, …, NS-D-1, D being the length of the correlation period; arg is a complex argument principal value;
Figure GDA0003510662450000033
is a differential preamble sequence
Figure GDA0003510662450000034
Complex conjugation of (a); w is the number of relevant periods, W is NS/D。
Further, in step 4), the number of the split differential leading subsequences is three, and the split differential leading subsequences are three differential leading subsequences which have the same length and are sampled continuously.
Further, in step 4), the relationship between the IQ imbalance factors obtained is:
Figure GDA0003510662450000035
wherein phi and psi are IQ imbalance factors; phi is a*Is the complex conjugate of phi; f. ofsIs the sampling frequency; k is 0,1,2, …, NS-D-1, D being the correlation period; Δ f is a carrier frequency offset; n is the number of FFT points;
Figure GDA0003510662450000036
three differential leader subsequences obtained for splitting, and the expressions are respectively:
Figure GDA0003510662450000037
Figure GDA0003510662450000038
Figure GDA0003510662450000039
wherein the content of the first and second substances,
Figure GDA00035106624500000310
is a differential leader sequence;
Figure GDA00035106624500000311
is a differential preamble sequence
Figure GDA00035106624500000312
Complex conjugation of (a); dS(k) Is an ideal differential preamble sequence.
Further, in order to eliminate the error generated by the approximation processing to the maximum extent and make the estimation result more accurate, in step 5), the method further includes a step of summing, weighting and averaging the obtained relationship between the IQ imbalance factors to obtain an IQ imbalance factor estimation value, where the expression of the IQ imbalance factor estimation value is:
Figure GDA00035106624500000313
wherein the content of the first and second substances,
Figure GDA00035106624500000314
an IQ imbalance factor estimation value; λ is the relationship between the obtained IQ imbalance factors; w (k) is a weight factor, and when three differential leader subsequences are obtained by splitting, the expression is as follows:
Figure GDA0003510662450000041
wherein the content of the first and second substances,
Figure GDA0003510662450000042
the three differential leader subsequences are obtained by splitting.
Further, the IQ phase imbalance estimation value is:
Figure GDA0003510662450000043
wherein the content of the first and second substances,
Figure GDA0003510662450000044
estimation of IQ phase imbalanceA value;
Figure GDA0003510662450000045
and
Figure GDA0003510662450000046
are IQ imbalance factor estimated values, respectively
Figure GDA0003510662450000047
Real and imaginary parts of (c).
Further, the IQ amplitude imbalance estimate is:
Figure GDA0003510662450000048
wherein the content of the first and second substances,
Figure GDA0003510662450000049
IQ amplitude imbalance estimation values;
Figure GDA00035106624500000410
and
Figure GDA00035106624500000411
are IQ imbalance factor estimated values respectively
Figure GDA00035106624500000412
Real and imaginary parts of (c);
Figure GDA00035106624500000413
is an IQ phase imbalance estimate.
Drawings
Fig. 1 is a schematic diagram of a zero intermediate frequency receiver of a wireless communication system according to the present invention;
FIG. 2 is a flowchart illustrating an IQ imbalance estimation method according to the present invention.
Detailed Description
The invention discovers that the OFDM system is sensitive to carrier offset frequency, a certain relation exists between the carrier offset frequency and IQ imbalance generated in the actual communication process, namely the IQ imbalance of a receiver can aggravate the influence of the carrier offset frequency on the system performance, so that the carrier offset frequency is estimated by utilizing the extracted differential preamble sequence, and the IQ imbalance is estimated on the basis, thereby comprehensively considering the influence of the carrier offset frequency and the IQ imbalance, realizing accurate estimation of the IQ imbalance and realizing accurate estimation of the carrier offset frequency in the process. The IQ imbalance estimation method according to the present invention will be described in detail with reference to the accompanying drawings and embodiments.
The method comprises the following steps:
fig. 2 shows an overall flow of an IQ mismatch estimation method according to the present invention. Specifically, the method comprises the following steps:
firstly, a system receiving end inputs a radio frequency signal received by an antenna into a mixer for IQ demodulation to obtain a time domain analog baseband signal r (t). Local oscillator generates I-path and Q-path analog signals L for frequency mixingI(t) and LQ(t) can be expressed as:
LI(t)＝(1+β)·cos(2πfct-θ/2)
LQ(t)＝-(1-β)·sin(2πfct+θ/2)
wherein, theta is IQ phase imbalance, beta is IQ amplitude imbalance, and fcIs the carrier frequency.
Low-pass filtered and sampled at a frequency fsAfter r (t) is sampled, a digital baseband signal is obtained
Figure GDA0003510662450000051
From digital baseband signals
Figure GDA0003510662450000052
Extracting leader sequence from the sequence
Figure GDA0003510662450000053
If carrier frequency deviation and IQ imbalance exist and the influence of noise is ignored, the extracted leader sequence
Figure GDA0003510662450000054
Can be expressed as:
Figure GDA0003510662450000055
wherein k is 0,1,2, …, NS-1，NSIs the length of the leader sequence; n is the number of FFT points; m is a unit ofS(k) Is an ideal leader sequence;
Figure GDA0003510662450000056
is mS(k) Complex conjugation of (a); f. ofsIs the sampling frequency; Δ f is a carrier frequency offset; φ and ψ are IQ imbalance factors, and φ and ψ are specifically expressed as:
Figure GDA0003510662450000057
Figure GDA0003510662450000058
thereby obtaining a preamble sequence containing carrier offset frequency and IQ imbalance.
Step two, the leader sequence is aligned
Figure GDA0003510662450000059
Carrying out differential calculation to obtain a differential leader sequence
Figure GDA00035106624500000510
Using differential preamble sequences
Figure GDA00035106624500000511
And carrying out carrier frequency offset estimation. The method specifically comprises the following steps:
1) calculating a received preamble sequence by
Figure GDA00035106624500000512
Differential sequence of
Figure GDA00035106624500000513
To eliminate residual dc offset:
Figure GDA00035106624500000514
wherein d isS(k) Is a differential preamble sequence
Figure GDA00035106624500000515
Ideal leader sequence of dS(k)＝mS(k)-mS(k-1)；
Figure GDA00035106624500000516
Is dS(k) Complex conjugation of (a).
2) Due to the leader sequence
Figure GDA00035106624500000517
With periodicity, the preamble sequence is differentiated
Figure GDA00035106624500000518
Is also a periodic sequence and both have the same minimum positive period T, i.e.:
Figure GDA00035106624500000519
3) for differential leader sequence
Figure GDA00035106624500000520
And (3) carrying out time delay autocorrelation and summation averaging with the length of D, and calculating to obtain a carrier frequency offset estimation value after the argument of the time delay autocorrelation and the summation average is taken:
Figure GDA00035106624500000521
wherein the content of the first and second substances,
Figure GDA00035106624500000522
is a carrier offset frequency estimated value; k is 0,1,2, …, NSD-1, D being the length of the correlation period and D being the smallest positive of the n preamble sequencesPeriod T, and not exceeding total length N of preamble sequenceSOne fourth of (1), that is, satisfying the condition D-nT ≦ NSN is a positive integer; arg is a complex argument principal value; w is the number of relevant periods, W is NS/D。
It should be noted that the result of the summation operation of the autocorrelation in step 3) is a complex number, for example, C ═ a + bi and the cumulative number is N, and then C is averaged to obtain the result
Figure GDA0003510662450000061
Then calculate the amplitude angle
Figure GDA0003510662450000062
Thus, the process of dividing the average by the accumulated number N (the division is equivalent to scaling down both the real part a and the imaginary part b of the complex number). The reliability of estimation can be enhanced by performing accumulated average on the multiple segments of correlation results.
Step three, utilizing the estimated value of carrier offset frequency
Figure GDA0003510662450000063
IQ imbalance estimation is performed. Specifically, the method comprises the following steps:
1) differential preamble sequence
Figure GDA0003510662450000064
Splitting into three continuous sampling differential leading subsequence
Figure GDA0003510662450000065
And
Figure GDA0003510662450000066
respectively as follows:
Figure GDA0003510662450000067
Figure GDA0003510662450000068
Figure GDA0003510662450000069
2) the three equations are combined, and three sampling continuous differential leading subsequences
Figure GDA00035106624500000610
And
Figure GDA00035106624500000611
the relation lambda between IQ imbalance factors is obtained as follows:
Figure GDA00035106624500000612
3) carrier offset frequency estimation
Figure GDA00035106624500000613
Substituting the equation and carrying out summation weighted average to obtain an IQ imbalance factor estimated value:
Figure GDA00035106624500000614
wherein w (k) is a weighting factor, which can be expressed as
Figure GDA00035106624500000615
Representing a leader subsequence
Figure GDA00035106624500000616
And
Figure GDA00035106624500000617
the sum of the energies of (a) and (b).
4) The IQ phase imbalance estimation value can be obtained by approximate calculation
Figure GDA00035106624500000618
And IQ amplitude imbalance estimation
Figure GDA00035106624500000619
Respectively as follows:
Figure GDA0003510662450000071
Figure GDA0003510662450000072
wherein the content of the first and second substances,
Figure GDA0003510662450000073
and
Figure GDA0003510662450000074
are respectively as
Figure GDA0003510662450000075
Real and imaginary parts of (c).
Therefore, IQ imbalance estimation is performed in a digital domain, and carrier offset frequency estimation is completed, namely, the joint estimation of IQ imbalance and carrier offset frequency is realized. For a zero intermediate frequency receiver, the influence of IQ imbalance can be fundamentally inhibited by adopting a higher-performance analog device. However, the high performance analog device has high cost and large power consumption, and is not suitable for the current mainstream wireless communication system. Therefore, IQ imbalance and carrier frequency offset joint estimation is realized in a digital domain by combining a digital signal processing mode and carrier frequency offset estimation, so that not only can real-time and accurate estimation and compensation be realized, but also the cost of a receiver can be effectively saved.
The zero intermediate frequency receiver can generate direct current offset due to local oscillator leakage, and the receiving and demodulating performance is influenced. Although the dc offset is filtered out before the joint estimation of the carrier frequency offset and the IQ imbalance, there is still a residual dc offset. Therefore, in order to eliminate the residual DC offset, the present invention performs the IQ mixing preamble sequence in step two before the carrier frequency offset and IQ imbalance joint estimation
Figure GDA0003510662450000076
Carrying out differential calculation to obtain a differential leader sequence
Figure GDA0003510662450000077
In the estimation process, the IQ imbalance factors phi and psi are approximated, and the weighted average calculation is performed through the weighting factor w (k) in step three 3), so that the error generated by the approximation can be eliminated to the maximum extent, and the estimation result is more accurate. As another embodiment, after the relationship λ between the IQ imbalance factors is obtained by the calculation in step three, the IQ phase imbalance estimation value and the IQ amplitude imbalance estimation value are directly calculated by using the relationship λ, and compared with the IQ imbalance estimation obtained by weighting, the accuracy of this processing method is reduced, but the calculation rate is improved to some extent.
In the third step of this embodiment, the differential preamble sequence is split into three differential preamble subsequences with consecutive samples, and the relationship λ between IQ imbalance factors is obtained by using the three differential preamble subsequences. As another embodiment, the IQ imbalance factor can also be obtained by splitting the differential preamble subsequence into more than three (e.g., four) differential preamble subsequences, or splitting the differential preamble subsequence into at least three discontinuous differential preamble subsequences, where the expression of the split differential preamble subsequence is different from the expression shown in step 1) of step three), and then combining the differential preamble subsequences.
The method is applied in the following specific examples to illustrate the effectiveness of the method of the invention. The method is applied to a dual-mode communication protocol wireless physical layer of a power user electricity consumption information acquisition system, and the used system architecture refers to a part 4-1 of dual-mode communication interconnection technical specification published by a national power grid: physical layer communication protocol in the wireless physical layer part, the communication bandwidth of the used OFDM communication mode is 854.5kHz, the number of FFT points is 128, and the number of available subcarriers is 128. A simplified architecture of the zero intermediate frequency receiver used is shown in figure 1. The method mainly comprises the following steps: generating a periodic time domain preamble sequence, receiving the preamble sequence, performing time domain differential processing, and performing IQ imbalance and carrier frequency offset joint estimation, specifically comprising the following steps:
1. a periodic time domain preamble sequence is generated.
A periodic time domain preamble sequence is generated by a specific frequency domain data sequence. The frequency domain data sequence inserts a fixed value on an OFDM subcarrier at a specific position, and the positive and negative are determined by the position of the subcarrier. The subcarriers numbered from 0 are inserted with normalization factors on the subcarriers numbered 8, 24, 48, 96, 104, 112, 120
Figure GDA0003510662450000081
Inserting on sub-carriers numbered 16, 32, 40, 80, 88
Figure GDA0003510662450000082
And the subcarriers at other positions do not carry information (set to 0), and the time domain original preamble sequence is obtained after 128-point FFT. And taking the sampling point data with the length of 1/4 at the tail of the original preamble sequence as a cyclic prefix, and adding the cyclic prefix to the original preamble sequence to obtain the original preamble sequence containing the cyclic prefix. And sequentially connecting the four groups of original leader sequences containing the cyclic prefix end to obtain the periodic time domain leader sequence. From this, the length N of the leader sequenceSThe minimum positive period T is 16, 640. And D/A conversion is carried out on the leader sequence, and the leader sequence is modulated to a carrier frequency signal to be sent.
2. And receiving a preamble sequence and performing time domain differential processing.
And receiving the preamble analog signal by adopting a zero intermediate frequency receiver. IQ frequency mixing is carried out on the received leading analog signal through a local oscillator signal, analog-to-digital conversion is carried out after low-pass filtering, and a received baseband leading sequence is obtained through sampling. And carrying out differential processing on the leader sequence, and eliminating residual direct current offset by calculating the difference of the amplitude between the front sampling point and the rear sampling point of the sequence to obtain a differential leader sequence.
3. IQ imbalance and carrier offset frequency joint estimation.
Let correlation period D be 8T be 128, and perform delay autocorrelation calculation with length D on the differential preamble sequence by using the periodicity of the differential preamble sequence. And summing and averaging the results of the multi-period time delay autocorrelation calculation, taking the argument, and calculating to obtain a carrier frequency offset estimation value. And splitting the differential preamble sequence into three groups of differential preamble subsequences with continuous sampling and equal length, and combining the three groups of differential preamble subsequences to obtain the relation between IQ imbalance factors. Substituting the carrier frequency deviation estimated value, and calculating an IQ imbalance estimated value after approximate processing. And finally, IQ imbalance and carrier frequency offset joint estimation is realized.

Claims (9)

1. An IQ imbalance estimation method, comprising:
1) processing a received radio frequency signal to obtain a leader sequence, wherein the leader sequence comprises a carrier frequency offset and an IQ imbalance factor;
2) carrying out differential calculation on the obtained leader sequence to obtain a differential leader sequence;
3) calculating to obtain a carrier offset frequency estimated value according to the differential leader sequence;
4) splitting the differential preamble sequence into at least three differential preamble subsequences, carrying out simultaneous operation on the differential preamble subsequences, and substituting the simultaneous operation result into the carrier offset frequency estimated value obtained in the step 3) to obtain the relation between IQ imbalance factors;
5) and obtaining an IQ phase imbalance estimation value and/or an IQ amplitude imbalance estimation value according to the relation between the IQ imbalance factors.
2. The IQ imbalance estimation method according to claim 1, wherein in step 1), the expression of the preamble sequence including the carrier frequency offset Δ f and the IQ imbalance factor is:
Figure FDA0003510662440000011
wherein the content of the first and second substances,
Figure FDA0003510662440000012
is a leader sequence; k is 0,1,2, …, NS-1，NSIs the length of the leader sequence; n is the number of FFT points; f. ofsIs the sampling frequency; m isS(k) Is an ideal leader sequence;
Figure FDA0003510662440000013
is mS(k) Complex conjugation of (a); Δ f is a carrier frequency offset; φ and ψ are IQ imbalance factors, and the expression for IQ imbalance factors φ and ψ is:
Figure FDA0003510662440000014
Figure FDA0003510662440000015
wherein θ is the IQ phase imbalance and β is the IQ amplitude imbalance.
3. The IQ imbalance estimation method according to claim 2, wherein in step 2), the differential preamble sequence is:
Figure FDA0003510662440000016
wherein d isS(k) Is a differential preamble sequence
Figure FDA0003510662440000017
Ideal differential preamble sequence of, and dS(k)＝mS(k)-mS(k-1)，
Figure FDA0003510662440000018
Is dS(k) Complex conjugation of (a).
4. The IQ imbalance estimation method according to claim 1, characterized in that in step 3), the following method is used to calculate the carrier offset frequency estimation value based on the differential preamble sequence:
performing time delay autocorrelation and summation average operation with the length of D on the differential leader sequence, and obtaining the carrier offset frequency estimated value after taking the argument of the operation result, wherein the carrier offset frequency estimated value is as follows:
Figure FDA0003510662440000021
wherein the content of the first and second substances,
Figure FDA0003510662440000022
is a carrier offset frequency estimated value; n is the number of FFT points; f. ofsIs the sampling frequency; k is 0,1,2, …, NS-D-1, D being the length of the correlation period; arg is a complex argument principal value;
Figure FDA0003510662440000023
is a differential preamble sequence
Figure FDA0003510662440000024
Complex conjugation of (a); w is the number of relevant periods, W is NS/D。
5. The IQ imbalance estimation method according to claim 1, wherein in step 4), the number of the split differential preamble subsequences is three, and the split differential preamble subsequences are three continuous-sampling differential preamble subsequences with equal length.
6. The IQ imbalance estimation method according to claim 4, wherein the relationship between IQ imbalance factors determined in step 4) is:
Figure FDA0003510662440000025
wherein phi and psi are IQ imbalance factors; phi is a*Is the complex conjugate of phi; f. ofsIs the sampling frequency; k is 0,1,2, …, NS-D-1, D being the correlation period; Δ f is a carrier frequency offset; n is the number of FFT points;
Figure FDA0003510662440000026
three differential leader subsequences obtained for splitting, and the expressions are respectively:
Figure FDA0003510662440000027
Figure FDA0003510662440000028
Figure FDA0003510662440000029
wherein the content of the first and second substances,
Figure FDA00035106624400000210
is a differential leader sequence;
Figure FDA00035106624400000211
is a differential preamble sequence
Figure FDA00035106624400000212
Complex conjugation of (a); dS(k) Is an ideal differential preamble sequence.
7. The IQ imbalance estimation method according to claim 1, wherein the step 5) further comprises summing weighted averages of the obtained relationships between IQ imbalance factors to obtain IQ imbalance factor estimated values, and the expression of the IQ imbalance factor estimated values is as follows:
Figure FDA00035106624400000213
wherein the content of the first and second substances,
Figure FDA0003510662440000031
an IQ imbalance factor estimation value is obtained; λ is the relationship between the obtained IQ imbalance factors; w (k) is a weight factor, and when three differential leader subsequences are obtained by splitting, the expression is as follows:
Figure FDA0003510662440000032
wherein the content of the first and second substances,
Figure FDA0003510662440000033
the three differential leader subsequences are obtained by splitting.
8. The IQ imbalance estimation method according to claim 7, wherein the IQ phase imbalance estimate is:
Figure FDA0003510662440000034
wherein the content of the first and second substances,
Figure FDA0003510662440000035
an IQ phase imbalance estimation value;
Figure FDA0003510662440000036
and
Figure FDA0003510662440000037
are IQ imbalance factor estimated values, respectively
Figure FDA0003510662440000038
Real and imaginary parts of (c).
9. The IQ imbalance estimation method according to claim 7, wherein the IQ amplitude imbalance estimate is:
Figure FDA0003510662440000039
wherein the content of the first and second substances,
Figure FDA00035106624400000310
IQ amplitude imbalance estimation values;
Figure FDA00035106624400000311
and
Figure FDA00035106624400000312
are IQ imbalance factor estimated values, respectively
Figure FDA00035106624400000313
The real and imaginary parts of (c);
Figure FDA00035106624400000314
is an IQ phase imbalance estimate.
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