A digital equalization method for improving the frequency flatness of an ultra-wideband millimeter wave channel simulation

Abstract

The application discloses a digital equalization method for improving frequency flatness of an ultra-wideband millimeter wave channel simulation, and comprises the following steps: point sampling a transmission function and the transmission function to obtain and respectively, and shifting the and to a baseband to obtain and respectively; introducing a compensation signal into the baseband, and transmitting the compensation signal of the baseband to a storage space of a chip through a transmission bus to replace channel coefficients to perform channel simulation and flatness compensation based on a tapped delay line (TDL). The application only needs to occupy resources of channel simulation, can save a large amount of cost, has a low bit error rate and a fast response speed.

Description

Technical Field

[0001] The present invention relates to the technical field of channel simulators, and in particular to a digital equalization method for improving the frequency flatness of ultra-wideband millimeter wave channel simulation. Background Art

[0002] An ultra-wideband millimeter-wave channel simulator is a device used to simulate and generate millimeter-wave wireless communication channel environments. Its primary function is to simulate various characteristics of millimeter-wave wireless communication channels, such as multipath effects, shadow fading, and Doppler shift, to facilitate testing and verification of wireless communication systems in a laboratory or simulation environment. Using the channel simulator, researchers and engineers can study the performance of wireless communication systems in a controlled environment and evaluate the performance of different signal processing algorithms and communication protocols. This helps accelerate the development and improvement of wireless communication technology and enhance the performance and reliability of wireless communication systems.

[0003] In ultra-wideband millimeter-wave channel analog systems, as frequencies increase, in-band frequency flatness, a measure of linear distortion in the transmit chain, becomes crucial. Whether it's the frequency selectivity of the amplifier circuits and various analog filter stages, or impedance mismatches between components in the transmit chain, these factors directly impact the in-band flatness of the output signal. During the design and manufacture of related equipment, due to factors such as material quality, design process, and component price, the in-band frequency flatness of the system's components sometimes fails to directly meet system requirements. Consequently, digital design, relying on platforms such as programmable logic FPGAs, is necessary to compensate for the in-band distortion of analog components like frequency converters.

[0004] The digital domain flatness compensation of ultra-wideband millimeter wave channel analog systems mainly adopts the method of designing FIR filters (Finite Impulse Response, finite length unit impulse response filters) to perform flatness compensation. For example, the frequency domain sampling method requires sampling within the signal's spectral band and determining the flatness compensation coefficients through the amplitude response. These coefficients are used to correct the amplitude of the signal by performing FIR filtering on the amplitude response so that it has a flat amplitude response on all frequency components. For example, the adaptive filtering method, after sampling within the signal's spectral band to obtain the spectrum to be compensated, does not directly design the FIR filter, but it iterates through the error function to obtain filter coefficients with lower orders. For ultra-wideband devices, the order of the filter designed by the frequency domain sampling method is too high, usually reaching more than 200 orders, while the filter designed by the adaptive filtering algorithm can only be reduced to about 100 orders, which increases the workload of the entire calibration process and consumes a lot of underlying resources. Summary of the Invention

[0005] For ultra-wide bandwidth filtering, a large amount of resources need to be allocated separately at the bottom layer to design high-order FIR filters, which require resources for filtering and channel simulation. The large resource consumption brings about the technical problem of increased costs. The purpose of the present invention is to provide a digital equalization method that improves the frequency flatness of ultra-wideband millimeter-wave channel simulation. Based on the TDL model (Tapped Delay Line, tapped delay line model), digital equalization and channel simulation are simultaneously realized, which only requires resources for channel simulation, can save a lot of costs, have a low bit error rate, and a fast response speed.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel, the digital equalization method comprising the following steps:

[0008] S1: Use a millimeter-wave signal source to transmit a millimeter-wave signal. Pass the signal through a channel simulation system in direct-through mode, and a millimeter-wave spectrum analyzer receives the intermediate frequency signal to obtain the down-conversion transfer function D(ω). Use a millimeter-wave signal source to transmit an intermediate frequency signal. Pass the signal through a channel simulation system in direct-through mode, and a millimeter-wave spectrum analyzer receives the signal to obtain the up-conversion transfer function U(ω).

[0009] S2, the transfer function D(ω) and the transfer function U(ω) are sampled at N points to obtain D(k) and U(k) respectively, and then moved to the baseband to obtain D B (k) and U B (k), B (Baseband) represents baseband, where k = 0, 1, 2, ..., N-1;

[0010] S3, introduce compensation signal h in baseband C (n, p), Where h(n, p) is the channel coefficient of TDL channel simulation; m(p) is the time domain fit of 1 / M(k), and M(k) = D B (k)U B (k). The baseband compensation signal h C (n, p) is transmitted to the memory space of the chip through the transmission bus and replaces the channel coefficient to perform channel simulation and flatness compensation based on the tapped delay line TDL, where n = 0, 1, 2, ..., N-1, p = 0, 1, 2, ..., N p -1, N p The maximum number of supported multipaths.

[0011] Step S1 further comprises:

[0012] A millimeter-wave signal source transmits a millimeter-wave signal x(τ), with FFT[x(τ)] = X(ω). The signal received by the millimeter-wave spectrum analyzer is y(τ), and FFT[y(τ)] = Y(ω). The spectrum of the channel simulation coefficient h(t, τ) is H(t, ω). The uncompensated channel simulation output is:

[0013] Y(ω)=X(ω)D(ω-ω1)H(t,ω-ω0-ω1)U(ω)

[0014] Among them, ω0 and ω1 are the medium frequency point and millimeter wave RF frequency point respectively.

[0015] Step S2 further comprises:

[0016] Calculate the spectrum relationship of each part and move D(k) and U(k) to baseband to obtain D B (k) and U B (k), B (Baseband) represents baseband;

[0017] By D B (k) and U B (k) and then multiply to obtain M'(k);

[0018] Obtain an N-point approximation M(k) of M'(k) using the Parks-McClellan algorithm;

[0019] Perform a discrete inverse Fourier transform on 1 / M(k) to obtain m(n);

[0020] Repeat N for m(n) p Point uniform sampling to obtain m(p);

[0021] Calculate the baseband compensation signal

[0022] Furthermore, in step S3, the baseband compensation signal h is introduced C (n, p), directly replace the channel coefficients to perform channel simulation and flatness compensation based on the tapped delay line TDL:

[0023]

[0024] Furthermore, the ultra-wideband millimeter wave channel simulation system is divided into four subsystems: a down-conversion unit, a baseband processing unit, an intermediate frequency transceiver unit, and an up-conversion unit.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] First, the digital equalization method of the present invention for improving the frequency flatness of ultra-wideband millimeter-wave channel simulation does not need to allocate a large amount of resources at the bottom layer to design high-order FIR filters in the face of ultra-wide bandwidth filtering requirements. It only needs to transmit data through the interface, calculate the compensation coefficient on the host computer, and then send it to the original TDL model in the channel simulation function, thereby effectively saving resources.

[0027] Second, the digital equalization method of the present invention for improving the analog frequency flatness of ultra-wideband millimeter-wave channels theoretically derives the feasibility of combining the digital equalization method with the channel simulation function, transfers the traditional frequency-domain multiplication filtering to the time-domain multiplication filtering, and combines it with the small-scale channel model simulation theory.

[0028] Third, the digital equalization method of the present invention for improving the analog frequency flatness of ultra-wideband millimeter wave channels targets digital signal processing (DSP) resources and is based on reasonable optimization and application of algorithms, thereby saving a lot of costs.

[0029] Fourth, the digital equalization method of the present invention for improving the analog frequency flatness of ultra-wideband millimeter wave channels uses the channel coefficients that originally need to be transmitted between the upper and lower computers, and transmits the filter coefficients to the lower computer through the upper computer. It can achieve the effect of flatness compensation for different frequency bands without changing the underlying code, and is more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the layout of the flatness compensation device of the channel simulation system;

[0031] Figure 2 This is a schematic diagram for measuring the transfer function of a down-converter device;

[0032] Figure 3 This is a schematic diagram for measuring the transfer function of an up-converter device;

[0033] Figure 4 This figure shows the architecture for channel simulation and flatness compensation based on the TDL model. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0035] An embodiment of the present invention discloses a digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel. The digital equalization method includes the following steps:

[0036] S1: Use a millimeter-wave signal source to transmit a millimeter-wave signal. Pass the signal through a channel simulation system in direct-through mode, and a millimeter-wave spectrum analyzer receives the intermediate frequency signal to obtain the down-conversion transfer function D(ω). Use a millimeter-wave signal source to transmit an intermediate frequency signal. Pass the signal through a channel simulation system in direct-through mode, and a millimeter-wave spectrum analyzer receives the signal to obtain the up-conversion transfer function U(ω).

[0037] S2, sampling the transfer function D(ω) and the transfer function U(ω) at N points to obtain D(k) and U(k) respectively, where k = 0, 1, 2, ..., N-1, and N is the channel coefficient sampling point in the channel simulation;

[0038] S3, introduce baseband compensation signal h C (n, p), The baseband compensation signal h C (n, p) is transmitted to the memory space of the chip through the transmission bus and replaces the channel coefficient to perform channel simulation and flatness compensation based on the tapped delay line TDL, where n = 0, 1, 2, ..., N-1, p = 0, 1, 2, ..., N p -1, N p The maximum number of supported multipaths.

[0039] The frequency flatness of the present invention refers to the difference between the maximum frequency amplitude and the minimum frequency amplitude within the frequency band; channel simulation refers to the simulation of wireless communication environment characteristics by software or hardware.

[0040] The ultra-wideband millimeter wave channel simulation system of the present invention is divided into four subsystems: down-conversion unit, baseband processing unit, intermediate frequency transceiver unit, and up-conversion unit. The system layout is as follows: Figure 1 shown.

[0041] Based on the principle that the frequency domain transfer function is the division of the received signal spectrum and the transmitted signal spectrum, to compensate for the flatness of the analog device, the millimeter wave frequency is fixed, and a millimeter wave signal source is used to transmit the millimeter wave signal. After passing through the channel simulation system in direct mode, the millimeter wave spectrum analyzer receives the intermediate frequency signal, and then obtains the down-conversion transfer function D(ω), and IFFT[D(ω)]=d(τ), as shown in the following example. Figure 2 Similarly, a millimeter-wave signal source is used to transmit an intermediate frequency signal, which passes through a channel simulation system in direct mode, and a millimeter-wave spectrum analyzer receives the millimeter-wave signal, thereby obtaining the up-conversion transfer function U(ω) of the frequency converter, and IFFT[U(ω)]=u(τ), as shown in FIG. Figure 3 And the transfer function is sampled at N points to make it equal to the channel coefficient sampling points in the channel simulation.

[0042] Combined with the measured up and down conversion transfer functions, for Figure 1Assume that the millimeter-wave signal source transmits a signal x(τ), with FFT[x(τ)] = X(ω); the millimeter-wave spectrum analyzer receives a signal y(τ), with FFT[y(τ)] = Y(ω). The spectrum of the channel simulation coefficients h(t, τ) is H(t, ω). The uncompensated channel simulation output is given by equation (1), where ω0 and ω1 are the intermediate frequency and millimeter-wave RF frequency.

[0043] Y(ω)=X(ω)D(ω-ω1)H(t,ω-ω0-ω1)U(ω) (1)

[0044] Reflected in the baseband, the relationship between the spectrum of each part is as shown in formula (2).

[0045] Y B (ω)=X B (ω)D B (ω)H(t,ω)U B (ω) (2)

[0046] Introducing baseband compensation signal H C (t, ω), which directly replaces the channel coefficient, so that the output signal can complete the channel simulation function and the flatness compensation function, as shown in formula (3).

[0047] X B (ω)H(t,ω)=X B (ω)D B (ω)H C (t,ω)U B (ω) (3)

[0048] Therefore, the baseband compensation signal can be obtained as:

[0049] H C (t,ω)=H(t,ω) / M(ω) (4)

[0050] Where M(ω)=D B (ω)U B (ω).

[0051] Therefore, the baseband compensation signal can replace the channel coefficient and complete the dual functions of channel simulation and flatness compensation.

[0052] On this basis, the digital equalization method for improving the analog frequency flatness of the ultra-wideband millimeter wave channel of the present invention specifically includes the following steps:

[0053] ① At a fixed millimeter wave frequency, a millimeter wave signal source is used to transmit a millimeter wave signal. This signal passes through a channel simulation system in direct mode, and then a millimeter wave spectrum analyzer receives the intermediate frequency signal. This results in the down-conversion transfer function D(ω). Similarly, a millimeter wave signal source is used to transmit an intermediate frequency signal. This signal passes through a channel simulation system in direct mode, and then a millimeter wave spectrum analyzer receives the millimeter wave signal. This results in the up-conversion transfer function U(ω). This signal is sampled at N points to obtain D(k) and U(k), respectively, where k = 0, 1, 2, ..., N-1. N is typically 1024 or 2048.

[0054] ② From D(k) and U(k), we can get D B (k) and U B (k).

[0055] ③ By D B (k) and U B (k) and then multiply them to get M'(k).

[0056] ④ Obtain the N-point approximation of M'(k), namely M(k), through the Parks-McClellan algorithm.

[0057] ⑤ Perform discrete inverse Fourier transform on 1 / M(k) to obtain m(n), where n = 0, 1, 2, ..., N-1.

[0058] ⑥ Repeat N for m(n) p Point uniform sampling is performed to obtain m(p), where p = 0, 1, 2, ..., N p -1, N p The maximum number of supported multipaths.

[0059] ⑦According to formula (4),

[0060] ⑧ will h C (n, p) is transmitted to the chip's storage space such as RAM through a transmission bus such as the PCIe protocol.

[0061] ⑨ Carry out channel simulation and flatness compensation based on tapped delay line TDL. Figure 4 As shown, T s is the system clock cycle. It can be seen that the more simulated multipaths are supported, the higher the filtering frequency resolution is, and the maximum multipath delay N is. p T s The bigger.

[0062] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

[0063] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0064] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0065] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions for executing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0066] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0067] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel, characterized in that: The digital equalization method comprises the following steps: S1: Use a millimeter-wave signal source to transmit a millimeter-wave signal. Pass the signal through an ultra-wideband millimeter-wave channel simulation system in direct-through mode. A millimeter-wave spectrum analyzer receives the intermediate frequency signal, and the down-conversion transfer function D(ω) of the frequency converter is obtained. Use a millimeter-wave signal source to transmit an intermediate frequency signal. Pass the signal through an ultra-wideband millimeter-wave channel simulation system in direct-through mode. A millimeter-wave spectrum analyzer receives the signal, and the up-conversion transfer function U(ω) of the frequency converter is obtained. S2, the transfer function D(ω) and the transfer function U(ω) are sampled at N points to obtain D(k) and U(k) respectively, and then moved to the baseband to obtain D B (k) and U B (k), where k=0, 1, 2, ..., N-1; S3, introduces compensation signal h in baseband c (n, p), Where h(n, p) is the channel coefficient of TDL channel simulation; m(p) is the time domain fit of 1 / M(k), and M(k) = D B (k)U B (k); the compensation signal h c (n, p) is transmitted to the memory space of the chip through the transmission bus and replaces the channel coefficient to perform channel simulation and flatness compensation based on the tapped delay line TDL, where n = 0, 1, 2, ..., N-1, p = 0, 1, 2, ..., N p -1, N p The maximum number of supported multipaths.

2. The digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel according to claim 1, characterized in that: Step S1 further comprises: A millimeter-wave signal source transmits a millimeter-wave signal x(τ), with FFT[x(τ)] = X(ω). The signal received by the millimeter-wave spectrum analyzer is y(τ), and FFT[y(τ)] = Y(ω). The spectrum of the channel coefficient h(t, τ) is H(t, ω). The uncompensated channel simulation output is: Y(ω)=X(ω)D(ω-ω1)H(t,ω-ω0-ω1)U(ω) Among them, ω0 and ω1 are the medium frequency point and millimeter wave RF frequency point respectively.

3. The digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel according to claim 1, characterized in that: Step S2 further comprises: Calculate the spectrum relationship of each part and move D(k) and U(k) to baseband to obtain D B (k) and U B (k), B represents baseband; By D B (k) and U B (k) and then multiply to obtain M(k); Perform a discrete inverse Fourier transform on 1 / M(k) to obtain m(n); The Parks-McClellan algorithm is used to perform N on m(n) again. p Point uniform sampling to obtain m(p); Calculate the baseband compensation signal 4. The digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel according to claim 1, characterized in that: In step S3, the compensation signal h is introduced C (n, p), directly replace the channel coefficients to perform channel simulation and flatness compensation based on the tapped delay line TDL:

5. The digital equalization method for improving the analog frequency flatness of an ultra-wideband millimeter wave channel according to claim 1, characterized in that: The ultra-wideband millimeter wave channel simulation system is divided into four subsystems: a down-conversion unit, a baseband processing unit, an intermediate frequency transceiver unit, and an up-conversion unit.

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