Frequency decomposition multiplexing spread spectrum method based on digital beam forming

Abstract

The invention discloses a frequency decomposition multiplexing spread spectrum method based on digital beam forming, which comprises the following steps of: performing multiplexing on multiple paths of digital signals and address codes corresponding to each path of digital signals in a digital domain to obtain multiple paths of digital signals after spread spectrum; adding the multiple paths of digital signals after spectrum spreading to obtain a single-path composite digital signal; converting the single-path composite digital signal to an analog domain to obtain a single-path composite analog signal; extracting an expected signal from the single-path composite analog signal through a preset demultiplexing module; the desired signal is transmitted through an antenna. According to the invention, a large number of transmit-receive links and hardware in the transmit-receive links required by a scaled digital beam forming system from a digital domain to an analog domain are effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of radio transceiver systems, and more specifically, to a frequency division multiplexing and spread spectrum method based on digital beam forming. Background Art

[0002] In radar sensing and wireless communication systems, the use of digital beamforming technology can achieve superior system performance, including flexible beam control, precise and adjustable directional pattern characteristics, etc. In order to achieve these excellent characteristics, unit-level digital beamforming needs to be implemented, and each antenna array element needs to be equipped with a corresponding RF transceiver link and corresponding devices. The resulting large amount of computing resources and hardware requirements limit the widespread application of this technology. The use of multi-channel multiplexing technology can reduce the number of transmission links, reduce the complexity of the radio transceiver system of the digital beamforming system, and improve its versatility.

[0003] Existing multiplexing technologies include time division multiplexing, frequency division multiplexing, code division multiplexing and mode division multiplexing. Time division multiplexing and frequency division multiplexing technologies multiplex time and frequency resources respectively, and there are different degrees of frequency and time resource vacancies depending on the number of links; mode division multiplexing technology is not yet mature; traditional code division multiplexing technology requires multiplexing in the digital domain and multi-channel correlation operations in the analog domain for demultiplexing. Since the correlation operation requires multiplying the signal first and then integrating it in the time domain, as the operating frequency bands of radar and communication systems extend to millimeter waves and higher frequency bands, correlation operations are difficult to implement in the analog domain with general low-cost devices. This largely restricts the application of code division multiplexing technology in high-frequency digital beamforming systems. Summary of the invention

[0004] The present invention provides a frequency division multiplexing and spread spectrum method based on digital beam forming, which solves the technical problem that the traditional code division multiplexing technology in the prior art cannot be realized by universal low-cost devices.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] The present invention provides a frequency division multiplexing and spread spectrum method based on digital beam forming, comprising the following steps:

[0007] Multiplexing the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spread;

[0008] Adding the multi-channel digital signals after spectrum spreading to obtain a single-channel composite digital signal;

[0009] Converting the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal;

[0010] Extracting a desired signal from the single-channel composite analog signal through a preset demultiplexing module;

[0011] The desired signal is transmitted through the antenna.

[0012] Furthermore, the address code is a Walsh sequence.

[0013] Furthermore, the multiple digital signals and the address code corresponding to each digital signal are multiplexed in the digital domain to obtain the multiple digital signals after spectrum spread, including:

[0014] The multi-channel digital signals are multiplied by the Walsh sequence corresponding to each channel of digital signals in the digital domain to obtain the multi-channel digital signals after spectrum spread.

[0015] Furthermore, for the radio frequency demultiplexing architecture, before extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the method further includes the following steps:

[0016] The single-channel composite analog signal is subjected to up-conversion processing.

[0017] Furthermore, for the intermediate frequency demultiplexing architecture, after extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the following steps are also included:

[0018] The desired signal is subjected to up-conversion processing.

[0019] Furthermore, the preset demultiplexing module includes a power distribution network, a plurality of single-bit modulators and a plurality of bandpass filters, wherein:

[0020] The input end of the power distribution network receives the single-channel composite analog signal, and the multiple output ends of the power distribution network are respectively connected to a single-bit modulator;

[0021] Each of the single-bit modulators receives the signal allocated by the power distribution network and the corresponding address code, and inputs the output obtained by multiplying the signal allocated by the power distribution network and the corresponding address code into a bandpass filter;

[0022] The bandpass filter extracts the desired signal.

[0023] Furthermore, the center frequency of the bandpass filter is fc, and the bandwidth is B, wherein fc represents a preset antenna transmission frequency, and B represents the bandwidth of each digital signal itself.

[0024] Furthermore, the bandwidth B of each digital signal itself needs to be less than or equal to the symbol rate, and the symbol rate is equal to the address code rate divided by the address code length.

[0025] A second aspect of the present invention provides a frequency division multiplexing spread spectrum system based on digital beamforming, characterized in that it includes:

[0026] A multiplexing module, wherein the multiplexing module multiplexes the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spreading, and adds the multiple digital signals after spectrum spreading to obtain a single composite digital signal;

[0027] A digital-to-analog conversion module, wherein the digital-to-analog conversion module converts the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal;

[0028] A demultiplexing module, wherein the demultiplexing module extracts a desired signal from the single-channel composite analog signal through a preset demultiplexing module;

[0029] An antenna module transmits a desired signal through an antenna.

[0030] Furthermore, it also includes an up-conversion module:

[0031] For the RF demultiplexing architecture, the single-channel composite analog signal is also up-converted by an up-conversion module before the demultiplexing module;

[0032] For the intermediate frequency demultiplexing architecture, after the demultiplexing module, the desired signal is also subjected to up-conversion processing.

[0033] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0034] By utilizing the scheme of the present invention, the digital beamforming transmitting and receiving system can multiplex and demultiplex the transmitted and received data respectively through the multiplexing and demultiplexing steps in the digital domain and the analog domain, and can replace the traditional digital beamforming system at a low cost under reasonable scenarios and parameter configurations, thereby realizing a digital beamforming system with a small number of transmission links or even a single channel, effectively reducing the large number of transceiver links and the hardware therein required for the scaled digital beamforming system from the digital domain to the analog domain, and bringing changes at the system architecture level to the size, weight, power consumption, and cost characteristics of the digital beamforming system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic flow chart of a frequency division multiplexing spread spectrum method based on digital beamforming provided in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of a framework of a frequency division multiplexing spread spectrum method based on digital beamforming provided by an embodiment of the present invention;

[0037] Figure 3A schematic diagram of the structure of a demultiplexing module provided in an embodiment of the present invention;

[0038] Figure 4 A schematic diagram of the time domain waveform and amplitude spectrum of four-channel single-frequency sine waves after spectrum expansion provided by an embodiment of the present invention;

[0039] Figure 5 A schematic diagram of the time domain waveforms of four-channel single-frequency sine waves restored to baseband provided by an embodiment of the present invention;

[0040] Figure 6 A schematic diagram comparing beamforming directions of four-channel single-frequency sine waves provided in an embodiment of the present invention using frequency division multiplexing spread spectrum digital beamforming and a traditional digital beamforming system;

[0041] Figure 7 A schematic diagram of the time domain waveform and amplitude spectrum (channels 1-4) of the 32-channel linear frequency modulated continuous wave signal provided by an embodiment of the present invention after multiplication and spectrum spreading by the corresponding Walsh sequence;

[0042] Figure 8 A schematic diagram of a time domain waveform and amplitude spectrum (channels 1-4) of a linear frequency modulated continuous wave signal restored to baseband after frequency division multiplexing provided in an embodiment of the present invention;

[0043] Fig. 9 A schematic diagram of the amplitude spectrum of a signal synthesized by adding 32 spread spectrum signals provided in an embodiment of the present invention;

[0044] Fig.10 A schematic diagram of beamforming directions of 32 linear frequency modulated continuous wave signals provided in an embodiment of the present invention using frequency division multiplexing spread spectrum digital beamforming and a traditional digital beamforming system respectively. DETAILED DESCRIPTION

[0045] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0046] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0047] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0048] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0049] Example 1

[0050] This embodiment provides a frequency division multiplexing spread spectrum method based on digital beam forming, such as Figure 1 As shown, the following steps are included:

[0051] Multiplexing the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spread;

[0052] Adding the multi-channel digital signals after spectrum spreading to obtain a single-channel composite digital signal;

[0053] Converting the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal;

[0054] Extracting a desired signal from the single-channel composite analog signal through a preset demultiplexing module;

[0055] The desired signal is transmitted through the antenna.

[0056] In a further embodiment, the address code is a Walsh sequence.

[0057] In this embodiment, the spectrum distribution characteristics of the Walsh sequence are utilized, and a simple demultiplexing module is used to demultiplex the composite analog signal, thereby extracting multiple high-frequency modulated signals. The effect of the Walsh sequence on the undesired signal is to expand it to the corresponding spectrum, that is, the spectrum of the multiple access interference signal is expanded. According to the spectrum characteristics of the Walsh sequence, the main spectrum components are concentrated near the center frequency fc, and the center frequency interval between the spread spectrum component and the desired component is greater than the bandwidth of the signal, which means that the spread spectrum sequence corresponding to the channel moves the multiple access interference signal as a whole to the high frequency band and expands its power spectrum to a wider frequency band, while the desired signal can be regarded as not being affected by the spread spectrum sequence, maintaining the original time-frequency domain characteristics. Then a bandpass filter with a center frequency of fc and a bandwidth of B can be used to extract the desired signal from the composite signal. It should be noted that the bandwidth of the modulated baseband waveform signal needs to be less than or equal to the symbol rate.

[0058] In a further embodiment, multiple digital signals and address codes corresponding to each digital signal are multiplexed in the digital domain to obtain multiple digital signals after spectrum spread, including:

[0059] The multi-channel digital signals are multiplied by the Walsh sequence corresponding to each channel of digital signals in the digital domain to obtain the multi-channel digital signals after spectrum spread.

[0060] In a further embodiment, for the radio frequency demultiplexing architecture, before extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the method further includes the following steps:

[0061] The single-channel composite analog signal is subjected to up-conversion processing.

[0062] In a further embodiment, for the intermediate frequency demultiplexing architecture, after extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the following steps are further included:

[0063] The desired signal is subjected to up-conversion processing.

[0064] In a specific embodiment, according to the order of demultiplexing and frequency conversion, the system is divided into intermediate frequency demultiplexing (corresponding to Figure 2 IF demultiplexing structure) and RF demultiplexing (corresponding Figure 2 There are two types of architectures: IF demultiplexing architecture and RF demultiplexing architecture. IF demultiplexing extracts the signal after the digital-to-analog conversion, and each channel in the frequency conversion process still needs to be equipped with corresponding devices such as mixers and filters; RF demultiplexing first converts the frequency and then demultiplexes, and then radiates directly through the antenna, which enables multiplexing in the frequency conversion process.

[0065] The unit-level DBF needs to equip each array element with a separate RF link and its corresponding devices. The present invention uses code division multiplexing technology to merge these links to reduce the corresponding devices in the processing link. The RF link can be divided into superheterodyne and direct frequency conversion architectures according to the frequency conversion method, and can be divided into intermediate frequency sampling and RF sampling structures according to the digitized frequency band. From the perspective of code division multiplexing, the multiplexing of the transmitted DBF needs to be placed before the DAC, that is, in the digital domain. The multi-channel amplitude-phase weighted signals are marked by a pseudo-random sequence and then added to obtain a composite signal; after digital-to-analog conversion, up-conversion, filtering and demultiplexing in the broadband link, the multi-channel signals are restored to their original state and transmitted through the array antenna to obtain the desired signal spatial domain characteristics. In this process, it is obvious that the closer the demultiplexing link is to the antenna, the more multiplexed links and corresponding devices there are in the signal link. From the perspective of the development of software radio systems, it seems that it is more effective to directly adopt the RF sampling structure, because there are basically no analog devices in the link, but each link still requires a high-speed DAC, which may not be economical, and due to the diversity of radio system working requirements, it is necessary to consider sampling architectures in different frequency bands at the same time. The impact of the frequency conversion method on the transmission DBF multiplexing system can be ignored, because the multi-level frequency conversion can be divided into analog and digital domain frequency conversion, so the overall architecture is not affected.

[0066] In a further embodiment, the preset demultiplexing module is as follows Figure 3 As shown, it includes a power distribution network, multiple single-bit modulators and multiple bandpass filters, wherein:

[0067] The input end of the power distribution network receives the single-channel composite analog signal, and the multiple output ends of the power distribution network are respectively connected to a single-bit modulator;

[0068] Each of the single-bit modulators receives the signal allocated by the power distribution network and the corresponding address code, and inputs the output obtained by multiplying the signal allocated by the power distribution network and the corresponding address code into a bandpass filter;

[0069] The bandpass filter extracts the desired signal.

[0070] In a further embodiment, the center frequency of the bandpass filter is fc, and the bandwidth is B, wherein fc represents a preset antenna transmission frequency, and B represents the bandwidth of each digital signal itself.

[0071] In a further embodiment, the bandwidth B of each digital signal itself needs to be less than or equal to the symbol rate, and the symbol rate is equal to the address code rate divided by the address code length.

[0072] Example 2

[0073] This embodiment uses the method of embodiment 1, and adopts an eight-bit Walsh sequence to perform spread spectrum multiplexing on four single-frequency sinusoidal signals, so that the synthetic beam points to 30°. The waveform and spectrum after spread spectrum are as follows: Figure 4 As shown, the time domain waveform restored to baseband is as follows Figure 5 shown.

[0074] The normalized beamforming patterns of the two systems are shown in Figure 6 shown.

[0075] Therefore, in this embodiment, a single composite channel is used to multiplex the sinusoidal wave signals of the four channels, thereby obtaining a beamforming effect that is substantially consistent with that of a conventional digital beamforming system.

[0076] Example 3

[0077] This embodiment uses the method of embodiment 1, adopts a 32-bit Walsh sequence to perform spread spectrum multiplexing on 32 linear frequency modulated continuous wave modulation signals, and points the synthesized beam to -30°. The key steps of the system processing signals are shown in the figure below.

[0078] Figure 7 as well as Fig. 9 The time-frequency domain characteristics of the linear frequency modulation continuous wave signals of the four channels (numbered 1-4) in the frequency division multiplexing spread spectrum digital beamforming system are intuitively displayed, and the time-frequency domain characteristics of the 32-channel modulated signals multiplexed into a single broadband signal are intuitively displayed. The modulation spectrum of the spread spectrum signal by different Walsh sequences is also displayed. In order to intuitively display the amplitude and phase transmission characteristics of the frequency division multiplexing spread spectrum digital beamforming system, Figure 8 The results of recovering the signal after down-converting the linear frequency modulated continuous wave high frequency modulation signal in the frequency division multiplexing spread spectrum digital beamforming system and then low-pass filtering it to baseband are given.

[0079] The normalized beamforming patterns of the two systems are shown in Fig.10 shown.

[0080] Therefore, in this embodiment, a single composite channel is used to multiplex the sine wave signals of 32 channels, thereby obtaining a beamforming effect that is substantially consistent with that of a traditional digital beamforming system.

[0081] Example 4

[0082] This embodiment provides a frequency division multiplexing spread spectrum system based on digital beamforming, including:

[0083] A multiplexing module, wherein the multiplexing module multiplexes the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spreading, and adds the multiple digital signals after spectrum spreading to obtain a single composite digital signal;

[0084] A digital-to-analog conversion module, wherein the digital-to-analog conversion module converts the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal;

[0085] A demultiplexing module, wherein the demultiplexing module extracts a desired signal from the single-channel composite analog signal through a preset demultiplexing module;

[0086] An antenna module transmits a desired signal through an antenna.

[0087] In a further embodiment, an up-conversion module is also included:

[0088] For the RF demultiplexing architecture, the single-channel composite analog signal is also up-converted by an up-conversion module before the demultiplexing module;

[0089] For the intermediate frequency demultiplexing architecture, after the demultiplexing module, the desired signal is also subjected to up-conversion processing.

[0090] The same or similar reference numerals correspond to the same or similar components;

[0091] The terms used in the drawings to describe positional relationships are only used for illustrative purposes and should not be construed as limiting this patent;

[0092] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A frequency division multiplexing spread spectrum method based on digital beamforming, characterized in that: The following steps are involved: Multiplexing the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spread; Adding the multi-channel digital signals after spectrum spreading to obtain a single-channel composite digital signal; Converting the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal; Extracting a desired signal from the single-channel composite analog signal through a preset demultiplexing module; The desired signal is transmitted through the antenna.

2. The frequency division multiplexing and spread spectrum method based on digital beamforming according to claim 1, characterized in that: The address code is a Walsh sequence.

3. The frequency division multiplexing and spread spectrum method based on digital beamforming according to claim 2, characterized in that: Multiplexing multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain multiple digital signals after spectrum spread, including: The multi-channel digital signals are multiplied by the Walsh sequence corresponding to each channel of digital signals in the digital domain to obtain the multi-channel digital signals after spectrum spread.

4. The frequency division multiplexing and spread spectrum method based on digital beamforming according to claim 3, characterized in that: For the radio frequency demultiplexing architecture, before extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the method further includes the following steps: The single-channel composite analog signal is subjected to up-conversion processing.

5. The frequency division multiplexing spread spectrum method based on digital beamforming according to claim 3, characterized in that: For the intermediate frequency demultiplexing architecture, after extracting the desired signal from the single-channel composite analog signal through a preset demultiplexing module, the method further includes the following steps: The desired signal is subjected to up-conversion processing.

6. The frequency division multiplexing and spread spectrum method based on digital beamforming according to claim 4 or 5, characterized in that: The preset demultiplexing module includes a power distribution network, a plurality of single-bit modulators and a plurality of bandpass filters, wherein: The input end of the power distribution network receives the single-channel composite analog signal, and the multiple output ends of the power distribution network are respectively connected to a single-bit modulator; Each of the single-bit modulators receives the signal allocated by the power distribution network and the corresponding address code, and inputs the output obtained by multiplying the signal allocated by the power distribution network and the corresponding address code into a bandpass filter; The bandpass filter extracts the desired signal.

7. The frequency division multiplexing and spread spectrum method based on digital beamforming according to claim 6, characterized in that: The center frequency of the bandpass filter is fc, and the bandwidth is B, wherein fc represents the preset antenna transmission frequency, and B represents the bandwidth of each digital signal itself.

8. The frequency division multiplexing spread spectrum method based on digital beamforming according to claim 7, characterized in that: The bandwidth B of each digital signal needs to be less than or equal to the symbol rate, and the symbol rate is equal to the address code rate divided by the address code length.

9. A frequency division multiplexing spread spectrum system based on digital beamforming, characterized in that: include: A multiplexing module, wherein the multiplexing module multiplexes the multiple digital signals and the address code corresponding to each digital signal in the digital domain to obtain the multiple digital signals after spectrum spreading, and adds the multiple digital signals after spectrum spreading to obtain a single composite digital signal; A digital-to-analog conversion module, wherein the digital-to-analog conversion module converts the single-channel composite digital signal into an analog domain to obtain a single-channel composite analog signal; A demultiplexing module, wherein the demultiplexing module extracts a desired signal from the single-channel composite analog signal through a preset demultiplexing module; An antenna module transmits a desired signal through an antenna.

10. The frequency division multiplexing spread spectrum system based on digital beamforming according to claim 9, characterized in that: Also includes up-conversion module: For the RF demultiplexing architecture, the single-channel composite analog signal is also up-converted by an up-conversion module before the demultiplexing module; For the intermediate frequency demultiplexing architecture, after the demultiplexing module, the desired signal is also subjected to up-conversion processing.

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