High-performance IQ imbalance estimation method

Abstract

The invention relates to the technical field of wireless signal processing, and particularly discloses a high-performance IQ imbalance estimation method, which comprises the following steps of: receiving an actual pilot signal sent by a sending end, and locally generating a pilot signal as an ideal pilot signal in equipment; comparing the actual pilot signal with the ideal pilot signal, and calculating an IQ imbalance parameter; compensating an actual sending signal of the sending end based on the IQ imbalance parameter to obtain a final receiving signal; and performing compensation evaluation on the final received signal based on the image frequency suppression ratio. According to the method for obtaining IQ imbalance parameters g and theta by using the pilot signals, the influence of the statistical sample number and the original characteristics of the signals is very small, and the lower the noise is, the better the performance is. As the noise is reduced to a certain degree, the method provided by the invention can accurately estimate the IQ imbalance parameter.

Description

Technical Field

[0001] The invention relates to the technical field of wireless signal processing, and in particular to a high-performance IQ imbalance estimation method. Background Art

[0002] Zero-IF receivers are widely used in various digital communication systems due to their easy integration, low power consumption and low cost. Zero-IF receivers use orthogonal mixing in the analog domain to directly convert RF signals to baseband. However, in receivers using orthogonal mixing (whether zero-IF or superheterodyne), there is usually an unavoidable problem of I / Q branch amplitude and phase imbalance, which causes the performance of the receiving system to deteriorate. In addition, in order to achieve high-speed transmission within a limited bandwidth, high-order level-modulated orthogonal frequency division multiplexing (MQAM-OFDM) transmission technology is widely used. For such systems, even slight I / Q branch amplitude and phase imbalance can seriously deteriorate the demodulation performance of the MQAM-OFDM system and affect the synchronization and channel estimation quality of the receiver. Therefore, how to effectively compensate for the receiver I / Q branch imbalance is of great significance to improving the system performance of digital receivers. Summary of the invention

[0003] The object of the present invention is to provide a high-performance IQ imbalance estimation method to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A high-performance IQ imbalance estimation method, the method comprising:

[0006] Receive the actual pilot signal sent by the transmitter, and generate a pilot signal locally on the device as an ideal pilot signal;

[0007] Compare the actual pilot signal with the ideal pilot signal and calculate the IQ imbalance parameter;

[0008] The actual transmitted signal of the transmitting end is compensated based on the IQ imbalance parameter to obtain the final received signal;

[0009] The final received signal is compensated and evaluated based on the image frequency rejection ratio.

[0010] As a further solution of the present invention: the step of comparing the actual pilot signal with the ideal pilot signal and calculating the IQ imbalance parameter includes:

[0011] comparing the actual pilot signal with the ideal pilot signal;

[0012] Calculate signal energy;

[0013] Calculate phase imbalance parameters;

[0014] Calculate amplitude imbalance parameters;

[0015] The actual pilot signal is set to y(n)=y I (n)+jy Q (n); the ideal pilot signal is x(n) = x I (n)+jx Q (n).

[0016] As a further solution of the present invention: the process of calculating the signal energy includes:

[0017] The sum of the energy of the signal sent by I channel: E_Xi=∑x I 2 (n);

[0018] The sum of the energy of the Q-path transmitted signals: E_Xq=∑x Q 2 (n);

[0019] The sum of the energy of the I-path transmission signal and the Q-path transmission signal: E_XiXq = ∑(x I (n)×x Q (n));

[0020] The sum of the energy of the I-channel transmitted signal and the Q-channel received signal: E_XiYq = ∑(x I (n)×y Q (n));

[0021] The sum of the energy of the I-channel transmitted signal and the I-channel received signal: E_XiYi=∑(x I (n)×y I (n));

[0022] The sum of the energy of the Q-path transmission signal and the I-path reception signal: E_XqYi=∑(x Q (n)×y I (n));

[0023] The sum of the energy of the Q-path transmitted signal and the Q-path received signal: E_XqYq=∑(x Q (n)×y Q (n)).

[0024] As a further solution of the present invention: the calculation process of the phase imbalance parameter is:

[0025] In the formula, is the phase imbalance parameter.

[0026] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0027] In the formula, is the amplitude imbalance parameter.

[0028] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0029] In the formula, is the amplitude imbalance parameter.

[0030] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0031] In the formula, is the amplitude imbalance parameter.

[0032] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0033] In the formula, is the amplitude imbalance parameter.

[0034] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0035] In the formula, is the amplitude imbalance parameter.

[0036] As a further solution of the present invention: the calculation process of the amplitude imbalance parameter includes:

[0037] In the formula, is the amplitude imbalance parameter.

[0038] Compared with the prior art, the present invention has the following beneficial effects: the method proposed by the present invention for obtaining IQ imbalance parameters g and θ by using pilot signals is little affected by the number of statistical samples and the original characteristics of the signal, and the lower the noise, the better the performance. As the noise is reduced to a certain extent, the method proposed here can estimate the IQ imbalance parameters very accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0040] Figure 1 A flowchart of a high performance IQ imbalance estimation method.

[0041] Figure 2 Schematic diagram of estimating the amplitude imbalance factor in the high-performance IQ imbalance estimation method. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Figure 1 : is a flowchart of a high-performance IQ imbalance estimation method. In an embodiment of the present invention, a high-performance IQ imbalance estimation method is provided, the method comprising:

[0044] Step S100: receiving an actual pilot signal sent by a transmitting end, and generating a pilot signal locally in a device as an ideal pilot signal;

[0045] Step S200: comparing the actual pilot signal with the ideal pilot signal, and calculating an IQ imbalance parameter;

[0046] Step S300: compensating the actual transmitted signal of the transmitting end based on the IQ imbalance parameter to obtain a final received signal;

[0047] Step S400: performing compensation evaluation on the final received signal based on the image frequency suppression ratio.

[0048] In the technical solution of the present invention, a pilot signal is generated at the transmitting end and sent to the subject executing the method, that is, the receiving end. During this process, some distortion will occur in the signal itself. However, since the pilot signal is a prefabricated signal, a pilot signal can also be generated locally on the device. At this time, there are two signals, one is the actual pilot signal sent by the transmitting end, and the other is the pilot signal of the local device. If no distortion occurs, the actual pilot signal and the locally generated pilot signal should be the same, but in fact distortion will definitely occur. By comparing the actual pilot signal with the locally generated pilot signal, some compensation parameters can be determined to compensate for all signals actually received; the compensation parameters are IQ imbalance parameters.

[0049] It should be noted that I and Q are not input and output, but refer to the two components of an orthogonal signal. In IQ modulation (quadrature modulation), the signal is usually expressed in complex form; ideally, the I signal and the Q signal should have the same amplitude and a phase difference of 90 degrees; but in actual applications, the amplitudes are not the same, and the phase difference is more than 90 degrees. This is amplitude imbalance and phase imbalance.

[0050] As a preferred embodiment of the technical solution of the present invention, the step of comparing the actual pilot signal with the ideal pilot signal and calculating the IQ imbalance parameter includes:

[0051] comparing the actual pilot signal with the ideal pilot signal;

[0052] Calculate signal energy;

[0053] Calculate phase imbalance parameters;

[0054] Calculate amplitude imbalance parameters;

[0055] The actual pilot signal is set to y(n)=y I (n)+jy Q (n); the ideal pilot signal is x(n) = x I (n)+jx Q (n).

[0056] As a preferred embodiment of the technical solution of the present invention, the process of calculating the signal energy includes:

[0057] The sum of the energy of the signal sent by I channel: E_Xi=∑x I 2 (n);

[0058] The sum of the energy of the Q-path transmitted signals: E_Xq=∑x Q 2 (n);

[0059] The sum of the energy of the I-path transmission signal and the Q-path transmission signal: E_XiXq = ∑(x I (n)×x Q (n));

[0060] The sum of the energy of the I-channel transmitted signal and the Q-channel received signal: E_XiYq = ∑(x I (n)×y Q (n));

[0061] The sum of the energy of the I-channel transmitted signal and the I-channel received signal: E_XiYi=∑(x I (n)×y I (n));

[0062] The sum of the energy of the Q-path transmission signal and the I-path reception signal: E_XqYi=∑(x Q (n)×y I (n));

[0063] The sum of the energy of the Q-path transmitted signal and the Q-path received signal: E_XqYq=∑(x Q (n)×y Q (n)).

[0064] As a preferred embodiment of the technical solution of the present invention, the calculation process of the phase imbalance parameter is:

[0065] In the formula, is the phase imbalance parameter.

[0066] As a preferred embodiment of the technical solution of the present invention, the calculation process of the amplitude imbalance parameter includes several methods, as follows:

[0067]

[0068] In the formula, and They represent the amplitude imbalance parameters calculated by six methods respectively.

[0069] The calculation principle of the above content is explained as follows:

[0070] Assume that the received signal is y(n)=y I (n)+jy Q (n), the transmitted signal is x(n)=x I (n)+jx Q (n), white noise is n(n)=n I (n)+jn Q (n), the amplitude imbalance factor in IQ imbalance is g, is the estimated value of g, the phase imbalance factor θ, is the estimated value of θ, and the channel amplitude gain is a. For simplicity, it is assumed that the received signal is only affected by the channel gain, white noise, and IQ imbalance. Then:

[0071] y(n)=y I (n)+jy Q (n) = a × x I (n)+n I (n)+j(a×g×cosθ×x Q (n)―a×g×sinθ×x I (n)+n Q (n)), Formula 1;

[0072] 1) Multiply the real and imaginary parts of the transmitted signal by the real and imaginary parts of the received signal, respectively, and we have:

[0073] E{y I (n)×x I (n)}=a×E{x I 2 (n)}+E{n I (n)×x I(n)}, Formula 2a;

[0074] E{y I (n)×x Q (n)}=a×E{x I (n)×x Q (n)}+E{n I (n)×x Q (n)}, Formula 3a;

[0075] E{y Q (n)×x I (n)}=E{(a×g×cosθ×x Q (n)―a×g×sinθ×x I (n)+n Q (n))×x I (n)}=a×g×cosθ×E{x Q (n)×x I (n)}―a×g×sinθ×E{x I 2 (n)}+E{n Q (n)×x I (n)}, formula 4a;

[0076] E{y Q (n)×x Q (n)}=E{(a×g×cosθ×x Q (n)―a×g×sinθ×x I (n)+n Q (n))×x Q (n)}=a×g×cosθ×E{x Q 2 (n)}―a×g×sinθ×E{x I (n)×x Q (n)}+E{n Q (n)×x Q (n)}, Formula 5a;

[0077] 2) Since the noise is unrelated to the transmitted signal, it can be considered that:

[0078] E{n I (n)×x I (n)}→0; E{n I (n)×x Q (n)}→0; E{n Q (n)×x I (n)}→0; E{n Q (n)×x Q(n)}→0; thus, formulas 2a~5a become:

[0079] E{y I (n)×x I (n)}=a×E{x I 2 (n)}, Formula 2b;

[0080] E{y I (n)×x Q (n)}=a×E{x I (n)×x Q (n)}, Formula 3b;

[0081] E{y Q (n)×x I (n)}=a×g×cosθ×E{x Q (n)×x I (n)}―a×g×sinθ×E{x I 2 (n)}, formula 4b;

[0082] E{y Q (n)×x Q (n)}=a×g×cosθ×E{x Q 2 (n)}―a×g×sinθ×E{x I (n)×x Q (n)}, Formula 5b.

[0083] 3) Find θ:

[0084] From Formula 4b and Formula 5b, we can get:

[0085]

[0086] Thus, the phase imbalance factor in IQ imbalance can be estimated

[0087] atan(c) represents the process of phase calculation.

[0088] 4) Calculate the amplitude imbalance factor g:

[0089] 4.1) Combining formula 2b and 4b, we can get:

[0090]

[0091] That is,

[0092]

[0093] 4.2) Similarly, combining Formula 2 and Formula 5, we can get:

[0094]

[0095] 4.3) Similarly, combining Formula 3 and Formula 4, we can get:

[0096]

[0097] 4.4) Similarly, combining formula 3 and 5, we can get:

[0098]

[0099] 4.5) Using formula 4, if the received signal is processed by energy normalization, it can be considered that a = 1, then g can be obtained directly using formula 4 or 5.

[0100] 4.6) Using formula 5,

[0101] From formula 8-1 to formula 8-6, it can be seen that the method proposed in this paper takes into account the power of the I and Q signals and the related power when estimating the IQ imbalance factor, instead of simply assuming that the original signal I and Q signals have zero mean, equal power and are orthogonal to each other as in the prior art, thus eliminating the error caused by this assumption. Although the amount of calculation is slightly higher than the prior art, for equipment such as comprehensive testers that require very high estimation accuracy, this cost is negligible.

[0102] For further information on IQ imbalance estimation and compensation, please refer to Figure 2 .

[0103] Regarding step S300, its application process is the specific application process of the amplitude imbalance factor and the phase imbalance factor, which is actually similar to the above process and will not be repeated here.

[0104] Regarding step S400, the specific process is as follows:

[0105] The image rejection ratio R is usually used to measure the performance of I / Q branch imbalance compensation. The compensated baseband signal can be obtained from formulas c and e:

[0106]

[0107] Assuming the frequency signal is x*(n), the image rejection ratio is: The larger the R value, the better the image frequency suppression effect.

[0108] The functions that can be implemented by the high-performance IQ imbalance estimation method are all completed by a computer device, and the computer device includes one or more processors and one or more memories, and at least one program code is stored in the one or more memories. The program code is loaded and executed by the one or more processors to implement the functions of the high-performance IQ imbalance estimation method.

[0109] The processor takes out instructions from the memory one by one, analyzes the instructions, and then completes the corresponding operations according to the instruction requirements, generating a series of control commands, so that the various parts of the computer can automatically, continuously and coordinately move to become an organic whole, realize the input of programs, the input of data, and the calculation and output of results. The arithmetic operations or logical operations generated in this process are all completed by the operator; the memory includes a read-only memory (ROM), which is used to store computer programs, and a protection device is provided outside the memory.

[0110] Exemplarily, the computer program may be divided into one or more modules, one or more modules are stored in a memory and executed by a processor to implement the present invention. One or more modules may be a series of computer program instruction segments capable of implementing specific functions, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0111] Those skilled in the art will understand that the description of the above service equipment is merely an example and does not constitute a limitation on the terminal equipment. It may include more or fewer components than described above, or a combination of certain components, or different components, for example, it may include input and output devices, network access equipment, buses, etc.

[0112] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the terminal device, and uses various interfaces and lines to connect various parts of the entire user terminal.

[0113] The memory can be used to store computer programs and / or modules. The processor can realize various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as an information collection template display function, a product information release function, etc.); the data storage area can store data created according to the use of the berth status display system (such as product information collection templates corresponding to different product types, product information that different product providers need to release, etc.). In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0114] If the module / unit integrated in the terminal device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the modules / units in the above-mentioned embodiment system, and can also be completed by instructing the relevant hardware through a computer program. The above-mentioned computer program can be stored in a computer-readable storage medium, and the computer program can realize the functions of the above-mentioned various system embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable media may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0115] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0116] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high performance IQ imbalance estimation method, characterized in that: The method comprises: Receive the actual pilot signal sent by the transmitter, and generate a pilot signal locally on the device as an ideal pilot signal; Compare the actual pilot signal with the ideal pilot signal and calculate the IQ imbalance parameter; The actual transmitted signal of the transmitting end is compensated based on the IQ imbalance parameter to obtain the final received signal; The final received signal is compensated and evaluated based on the image frequency rejection ratio.

2. The high performance IQ imbalance estimation method according to claim 1, characterized in that: The step of comparing the actual pilot signal with the ideal pilot signal and calculating the IQ imbalance parameter comprises: comparing the actual pilot signal with the ideal pilot signal; Calculate signal energy; Calculate phase imbalance parameters; Calculate amplitude imbalance parameters; The actual pilot signal is set to y(n)=y I (n)+jy Q (n); the ideal pilot signal is x(n) = x I (n)+jx Q (n).

3. The high performance IQ imbalance estimation method according to claim 2, characterized in that: The process of calculating signal energy includes: The sum of the energy of the signal sent by I channel: E_Xi=∑x I 2 (n); The sum of the energy of the Q-path transmitted signals: E_Xq=∑x Q 2 (n); The sum of the energy of the I-path transmission signal and the Q-path transmission signal: E_XiXq = ∑(x I (n)×x Q (n)); The sum of the energy of the I-channel transmitted signal and the Q-channel received signal: E_XiXq = ∑(x I (n)×y Q (n)); The sum of the energy of the I-channel transmitted signal and the I-channel received signal: E_XiYi=∑(x I (n)×y I (n)); The sum of the energy of the Q-path transmission signal and the I-path reception signal: E_XqYi=∑(x Q (n)×y I (n)); The sum of the energy of the Q-path transmitted signal and the Q-path received signal: E_XqYq=∑(x Q (n)×y Q (n)).

4. The high performance IQ imbalance estimation method according to claim 3, characterized in that: The calculation process of phase imbalance parameter is: In the formula, is the phase imbalance parameter.

5. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

6. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

7. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

8. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

9. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

10. The high performance IQ imbalance estimation method according to claim 4, characterized in that: The calculation process of the amplitude imbalance parameter includes: In the formula, is the amplitude imbalance parameter.

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