A digital receiver signal demodulation method, system, device and storage medium

Abstract

The application discloses a digital receiver signal demodulation method, system, device and storage medium, and relates to the technical field of communication software radio. The method comprises the following steps: acquiring a complex signal, and judging the quadrant of the complex signal in a coordinate system; rotating the complex signal to the first quadrant of the coordinate system according to the absolute values of the real part and the imaginary part of the complex signal; determining the rotation angle and the iteration number of the complex signal; rotating the complex signal according to a specific rotation angle for multiple times until the last iteration result approaches the real axis, and outputting the complex signal and the phase after iteration; performing error compensation on the real part of the output complex signal to obtain the amplitude of the output complex signal, and restoring the phase after iteration according to the quadrant of the initial complex signal to obtain the phase of the output complex signal; and the method adopts a pipeline structure according to the iteration characteristics, increases the data throughput, and improves the data operation efficiency. Part of the operation is replaced by a lookup table, and resource consumption is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication software radio, in particular to a digital receiver signal demodulation method, system, device and storage medium. BACKGROUND

[0002] In a digital receiver, it is often necessary to calculate the amplitude and phase of the received digital signal to complete the demodulation and analysis of the digital signal.

[0003] The existing amplitude operation is to transfer the original signal from FPGA hardware to the software system by software and hardware cooperation technology, and to realize it by using the existing square, square root and trigonometric operation functions in high-level programming language, or to realize the square and square root operation in FPGA by directly using DSP operation. Both of these two solutions have considerable defects. The former will occupy a large amount of communication resources between hardware and software in the system, and when the signal sampling rate is very high, too frequent amplitude calculation will also bring a huge workload to the processor in the software system. The latter occupies a large amount of hardware resources, and the flexibility is also poor. Once the bit width of the input signal changes, the amplitude calculation function needs to be reprogrammed, which wastes a lot of development time. The algorithm designed in the present application can adapt to new signal bit width by directly changing the parameter configuration in the top layer of the module. At the same time, the use of a large amount of DSP resources will also cause the power consumption of the system to increase dramatically, which is not conducive to the realization of low-power design of the system.

[0004] However, the amplitude calculation methods currently used will occupy a large amount of communication resources between hardware and software, and it is difficult to provide stable input for subsequent digital signal demodulation, resulting in low accuracy of signal demodulation. SUMMARY

[0005] In view of the problems of the prior art that more important resources such as DSP and BRAM are consumed in the process of digital signal processing, and the calculation result is less accurate, the present application provides a digital receiver signal demodulation method, system, device and storage medium, which iteratively approximates the input complex signal by rotating it by a specific angle multiple times to obtain the phase and amplitude, thereby solving the problems existing in the prior art.

[0006] A digital receiver signal demodulation method, comprising the following steps:

[0007] Collecting the digital signal received by the digital receiver and converting the digital signal into a complex signal;

[0008] Calculating the amplitude and phase of the complex signal;

[0009] The amplification factor of the front-end amplifier of the digital receiver is controlled by the amplitude and phase of the complex signal, and the amplified complex signal is input into the signal processing unit of the digital receiver and demodulated to obtain a baseband digital signal;

[0010] The step of calculating the amplitude and phase of the complex signal specifically includes the following steps:

[0011] Determine the quadrant to which the complex signal belongs in the xy coordinate system;

[0012] Rotate the complex signal to the first quadrant of the xy coordinate system according to the absolute values ​​of the real and imaginary parts of the complex signal, and exchange the largest of the real and imaginary parts with the real part;

[0013] Determine the rotation angle and number of iterations of the complex signal according to the CORDIC iterative rotation angle table; iteratively rotate the complex signal according to the specific rotation angle multiple times until the final iteration result approaches the real axis, and then output the complex signal and its iterative phase;

[0014] The real part of the output complex signal is error-compensated and used as the amplitude of the output complex signal. The iterative phase is restored according to the quadrant to which the initial complex signal belongs and used as the phase of the output complex signal.

[0015] Furthermore, the determining of the quadrant to which the input complex signal belongs on the xy coordinate system is performed by determining the quadrant to which the complex signal belongs based on the difference between the real part and the imaginary part of the complex signal.

[0016] Furthermore, the calculation formula for the real part and imaginary part of the output complex signal is:

[0017] x i+1 =x i -y i tanθ

[0018] y i+1 =y i +x i tanθ

[0019] Among them, x i Represents the value of the real part at the i-th iteration, y i Represents the value of the imaginary part at the i-th iteration, x i+1 Represents the value of the real part at the i+1th iteration, y i+1 Represents the value of the real part at the i+1th iteration; θ represents the rotation angle, and the positive or negative value of θ indicates the direction of rotation.

[0020] Further, the complex signal is rotated to the first quadrant of the xy coordinate system according to the absolute values of the real part and the imaginary part of the complex signal, specifically, the coordinates of the point at the end of the complex signal on the coordinate system are selected, and the absolute values of the horizontal coordinate and the vertical coordinate of the point are taken to convert the coordinates of the point to positive numbers, so that the complex signal is rotated to the first quadrant of the xy coordinate system.

[0021] Further, the real part of the output complex signal is approximately the approximate value of the signal amplitude, and the amplitude of the output complex signal is obtained by multiplying the approximate value of the signal amplitude by a compensation coefficient.

[0022] The application also includes a digital receiver signal demodulation system, comprising:

[0023] The acquisition module is configured to acquire a digital signal received by the digital receiver and convert the digital signal into a complex signal.

[0024] The calculation module is configured to calculate the amplitude and phase of the complex signal.

[0025] The demodulation module is configured to control the amplification factor of the front-end amplifier of the digital receiver by the amplitude and phase of the complex signal, input the amplified complex signal into the signal processing unit of the digital receiver, and obtain a baseband digital signal through demodulation.

[0026] The calculation module comprises:

[0027] The judgment unit is configured to determine the quadrant of the input complex signal on the xy coordinate system.

[0028] The rotation unit is configured to rotate the complex signal to the first quadrant of the xy coordinate system according to the absolute values of the real part and the imaginary part of the complex signal, and exchange the maximum of the real part and the imaginary part to the real part.

[0029] The iterative rotation unit is configured to determine the rotation angle and the iteration number of the complex signal according to the CORDIC iteration rotation angle table, rotate the complex signal according to the specific rotation angle for multiple iterations, until the last iteration result approaches the real axis, and then output the complex signal and the phase after iteration.

[0030] The amplitude and phase output unit is configured to output the real part of the complex signal after error compensation as the amplitude of the output complex signal, and output the phase after iteration after restoration according to the quadrant of the initial complex signal as the phase of the output complex signal.

[0031] The application also includes a digital receiver signal demodulation computer device, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to realize the steps of the digital receiver signal demodulation method.

[0032] The application further comprises a readable storage medium storing a computer program, the computer program comprising program instructions for executing the steps of the digital receiver signal demodulation method when executed by a processor.

[0033] The application provides a digital receiver signal demodulation method, system, device and storage medium, which has the following beneficial effects:

[0034] The application adopts the CORDIC algorithm to calculate the amplitude and phase of the input complex signal, replaces the originally complex square, square root and trigonometric function operation with simple addition and shift calculation, so that it can be implemented in FPGA. Meanwhile, the pipeline structure is adopted according to the iteration characteristics, the data throughput is increased, and the data operation efficiency is improved. Part of the operation is replaced in the form of a lookup table, resource overhead is saved; the phase and amplitude are obtained by rotating the input complex signal by a specific angle multiple times for iterative approximation. Compared with directly calling the IP core, the calculation method consumes less important resources such as DSP and BRAM, and has higher calculation result accuracy; the amplitude of the signal is closed-loop controlled according to the amplitude and phase of the input complex signal to control the front-end amplifier of the digital receiver, the amplitude of the signal is stabilized to provide stable input for subsequent demodulation algorithms, the signal demodulation accuracy is improved, and the hardware resource consumption of the digital receiver can be reduced under the condition of ensuring the same demodulation performance. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 CORDIC algorithm vector rotation schematic diagram in the present application;

[0036] Figure 2 Case structure block diagram in the embodiment of the present application;

[0037] Figure 3 Quadrant division diagram of the preprocessing module in the embodiment of the present application;

[0038] Figure 4 USB signal demodulation output schematic diagram in the embodiment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0040] The coordinate rotation digital computer (CORDIC) algorithm was first proposed by J.D.Volder in 1959 and was initially used in navigation systems. The algorithm rotates a complex number by a specific angle multiple times, such asFigure 1 CORDIC algorithm is also very suitable for appearing in the form of pipeline because of its iterative calculation nature, which greatly improves the data throughput rate, therefore, CORDIC algorithm is very suitable for hardware implementation on FPGA.

[0041] The application provides a signal demodulation method for a digital receiver, which adopts CORDIC algorithm to calculate the amplitude and phase of an input complex signal, replaces the originally complex square root and trigonometric function operation with simple addition and shift calculation, and can be implemented in FPGA, and comprises the following steps.

[0042] Step 1: pre-process the input signal IQ of the digital receiver, rotate the input complex signal to the first quadrant by taking absolute value (select the coordinates of the point at the end of the complex signal on the coordinate system, take absolute value of the horizontal coordinate and the vertical coordinate of the point to convert the coordinates of the point to positive numbers, so as to rotate the complex signal to the first quadrant of the xy coordinate system), and exchange the larger number to the real part to ensure that the complex signal is located in the lower half of the first quadrant, so as to facilitate subsequent calculation.

[0043] Step 2: during the absolute value calculation and the real part and imaginary part exchange operation, the quadrant position of the original signal is deduced according to the process, and the quadrant position is recorded together with the data and sent to the subsequent processing module, and the quadrant information can be used for subsequent phase recovery.

[0044] Step 3: in the iterative calculation module, the direction of this rotation is determined according to the positive and negative of the imaginary part of the input signal, that is, the positive and negative of θ, and then the real part and the imaginary part of the complex signal after rotation are calculated according to the formula x i+1 = x i -y i tanθ and y i+1 = y i +x i tanθ, because the rotation angle takes a special value, this step can replace the multiplication and trigonometric function operation with shift operation.

[0045] Step 4: while calculating the real part and the imaginary part of the complex signal after rotation, the phase change caused by this rotation is recorded by looking up table 1 according to the direction of rotation and the number of iterations, and is transmitted to the next stage together with the complex signal.

[0046] Table 1: iteration rotation angle table

[0047]

[0048] Step 5: repeat steps 3 and 4 according to the preset angle table until the accuracy of the iteration result meets the design requirement.

[0049] Step 6: the real part of the last stage output signal is compensated for error and taken as the amplitude output, and the phase of the last stage output is recovered according to the rotation information recorded in the preprocessing and taken as the phase output (in the preprocessing process, all input vectors are rotated to the lower half of the first quadrant by taking the absolute value and exchanging the larger one to the real part, so the finally calculated phase is not the true value, and the original phase information recorded before rotation by the preprocessing module needs to be used to recover the phase).

[0050] First, the iteration number of the CORDIC algorithm is determined according to the system requirement and the iteration rotation angle table (Table 1) of the CORDIC, and the iteration number selected in this case is 15 times. The overall structure block diagram of this case is shown in Fig. 1, and the input complex signal is sent into the CORDIC module, and the quadrant to which the input signal belongs is determined according to the size difference between the real part and the imaginary part, as shown in Fig. 2. After recording this information, the absolute values of the real part and the imaginary part are taken, and the larger one is exchanged to the real part, so that the input complex signal is rotated to the region 0 in Fig. 3. The processed data and the recorded phase information are sent into the iteration module of the later stage at the same time. Figure 2 Figure 3 Figure 3

[0051] In the iteration module, each stage is rotated by the corresponding angle given in Table 1 in turn, and the input vector is rotated clockwise when it is in the region 0, and it is rotated counterclockwise when it is in the region 7, and the final iteration target is to make the output complex signal as close to the real axis as possible. After determining the rotation direction, the phase change caused by this stage iteration is recorded by using the table lookup method.

[0052] After repeating the iteration module for 15 times, the last iteration result is very close to the real axis, so it can be approximately considered that the real part of the complex signal output is the amplitude of the signal, and at the same time, the phase before iteration can be inversely deduced by using the phase change recorded in the iteration.

[0053] Since the amplitude of the complex signal is approximately processed during the rotation process, a compensation coefficient needs to be multiplied to obtain the true input signal amplitude. At the same time, the phase also needs to be recovered according to the region information recorded in the preprocessing module and then output.

[0054] The simulation effect of the present application is shown in Fig. 4, the input is a single tone signal, the output phase presents a slanting triangular wave, the period is the same as the input signal, the output amplitude only fluctuates in a small range, and basically remains stable, and the output result meets the expectation. Figure 4

[0055] Based on the same inventive concept, the present application also proposes a digital receiver signal demodulation system, which comprises: ​​​​

[0056] The acquisition module is configured to acquire a digital signal received by the digital receiver and convert the digital signal into a complex signal.

[0057] The calculation module is configured to calculate the amplitude and phase of the complex signal.

[0058] The demodulation module is configured to control the amplification factor of the front-end amplifier of the digital receiver by the amplitude and phase of the complex signal, input the amplified complex signal into the signal processing unit of the digital receiver, and obtain a baseband digital signal through demodulation.

[0059] The calculation module includes:

[0060] The judgment unit is configured to determine the quadrant of the input complex signal in the xy coordinate system.

[0061] The rotation unit is configured to rotate the complex signal to the first quadrant of the xy coordinate system according to the absolute values of the real part and the imaginary part of the complex signal, and exchange the larger one of the real part and the imaginary part to the real part.

[0062] The iterative rotation unit is configured to determine the rotation angle and the iteration number of the complex signal according to the CORDIC iteration rotation angle table, rotate the complex signal according to the specific rotation angle for multiple iterations until the last iteration result approaches the real axis, and then output the complex signal and the phase after iteration.

[0063] The amplitude and phase output unit is configured to output the real part of the output complex signal as the amplitude of the output complex signal after error compensation, and output the phase after iteration as the phase of the output complex signal after restoration according to the quadrant of the initial complex signal.

[0064] Based on the same inventive concept, the present application further provides a digital receiver signal demodulation computer device, which comprises a memory, a processor and a computer program stored in the memory, and the processor implements the steps of the digital receiver signal demodulation method when executing the computer program.

[0065] Based on the same inventive concept, the present application further provides a readable storage medium, which stores a computer program, and the computer program comprises program instructions, and the program instructions are executed by a processor to perform the steps of the digital receiver signal demodulation method.

[0066] The above is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent substitutions or changes to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A digital receiver signal demodulation method, characterized in that: The following steps are involved: Acquiring a digital signal received by a digital receiver and converting the digital signal into a complex signal; Calculate the amplitude and phase of complex signals; The amplification factor of the front-end amplifier of the digital receiver is controlled by the amplitude and phase of the complex signal, and the amplified complex signal is input into the signal processing unit of the digital receiver and demodulated to obtain a baseband digital signal; The step of calculating the amplitude and phase of the complex signal specifically includes the following steps: Determine the quadrant to which the complex signal belongs in the xy coordinate system; Rotate the complex signal to the first quadrant of the xy coordinate system according to the absolute values ​​of the real and imaginary parts of the complex signal, and exchange the largest of the real and imaginary parts with the real part; Determine the rotation angle and number of iterations of the complex signal according to the CORDIC iterative rotation angle table; iteratively rotate the complex signal according to the specific rotation angle multiple times until the final iteration result approaches the real axis, and then output the complex signal and its iterative phase; The real part of the output complex signal is error-compensated and used as the amplitude of the output complex signal. The iterative phase is restored according to the quadrant to which the initial complex signal belongs and used as the phase of the output complex signal.

2. A digital receiver signal demodulation method according to claim 1, characterized in that: The determining of the quadrant to which the complex signal belongs on the xy coordinate system is performed by determining the quadrant to which the complex signal belongs according to the difference between the real part and the imaginary part of the complex signal.

3. A digital receiver signal demodulation method according to claim 1, characterized in that: The calculation formula for the real part and imaginary part of the output complex signal is: x i+1 =x i -y i tanθ and i+1 =and i +x i tanθ Among them, x i Represents the value of the real part at the i-th iteration, y i Represents the value of the imaginary part at the i-th iteration, x i+1 Represents the value of the real part at the i+1th iteration, y i+1 Represents the value of the real part at the i+1th iteration; θ represents the rotation angle, and the positive or negative value of θ indicates the direction of rotation.

4. A digital receiver signal demodulation method according to claim 1, characterized in that: The method of rotating the complex signal to the first quadrant of the xy coordinate system according to the absolute values ​​of the real and imaginary parts of the complex signal is specifically to select the coordinates of the point at the end of the complex signal in the coordinate system, and to take the absolute values ​​of the horizontal and vertical coordinates of the point at the same time to convert the coordinates of the point into positive numbers, thereby rotating the complex signal to the first quadrant of the xy coordinate system.

5. A digital receiver signal demodulation method according to claim 1, characterized in that: The real part of the output complex signal is approximately equal to the approximate value of the signal amplitude, and the amplitude of the output complex signal is obtained by multiplying the approximate value of the signal amplitude by a compensation coefficient.

6. A digital receiver signal demodulation system, characterized in that: include: An acquisition module, configured to acquire a digital signal received by a digital receiver and convert the digital signal into a complex signal; A calculation module, used to calculate the amplitude and phase of the complex signal; The demodulation module is used to control the amplification factor of the front-end amplifier of the digital receiver through the amplitude and phase of the complex signal, input the amplified complex signal into the signal processing unit of the digital receiver, and demodulate it to obtain a baseband digital signal; Wherein, the calculation module includes: a judgment unit, configured to judge the quadrant to which the input complex signal belongs in the xy coordinate system; a rotation unit, configured to rotate the complex signal to the first quadrant of the xy coordinate system according to the absolute values ​​of the real part and the imaginary part of the complex signal, and to exchange the largest one of the real part and the imaginary part with the real part; An iterative rotation unit is used to determine the rotation angle and number of iterations of the complex signal according to the CORDIC iterative rotation angle table; iteratively rotate the complex signal according to the specific rotation angle multiple times until the last iteration result approaches the real axis, and then output the complex signal and its iterative phase; The amplitude and phase output unit is used to perform error compensation on the real part of the output complex signal and use it as the amplitude of the output complex signal, and to restore the iterated phase according to the quadrant to which the initial complex signal belongs and use it as the phase of the output complex signal.

7. A digital receiver signal demodulation computer device, characterized in that: include: A memory, a processor, and a computer program stored in the memory, wherein when the processor executes the computer program, the steps of the digital receiver signal demodulation method according to any one of claims 1 to 5 are implemented.

8. A readable storage medium, characterized in that: The readable storage medium stores a computer program, and the computer program includes program instructions. When the program instructions are executed by a processor, they are used to execute the steps of the digital receiver signal demodulation method according to any one of claims 1 to 5.

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