LU502869B1

LU502869B1 - Ultrashort wave spread spectrum communication system

Info

Publication number: LU502869B1
Application number: LU502869A
Authority: LU
Inventors: Yu Wang; Ao Li; Shuo Xu
Original assignee: Fishery Engineering Res Institute Chinese Academy Of Fishery Sciences
Priority date: 2022-10-04
Filing date: 2022-10-04
Publication date: 2023-04-04

Abstract

The present invention provides an ultrashort wave spread spectrum communication system, including: an analog radio frequency signal receiving unit, an analog radio frequency signal transmitting unit, an analog signal conditioning unit, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a field programmable logic gate array, and a high-speed real-time signal processing unit. The analog radio frequency signal receiving unit receives an analog radio frequency signal; the analog signal conditioning unit performs signal conditioning; the analog-to-digital conversion unit converts an analog signal into a digital signal; the field programmable logic gate array performs underlying signal processing; the high-speed real-time signal processing unit performs upper-layer communication protocol and signal processing; the digital-to-analog conversion unit converts the digital signal into the analog signal; and the analog radio frequency signal transmitting unit sends the signal. By means of the present invention, the stability and anti-noise performance of the system are improved.

Description

ULTRASHORT WAVE SPREAD SPECTRUM COMMUNICATION SYSTEM

Technical Field

The present invention relates to the field of wireless communication, and in particular to a highly reliable anti-interference fishery ultrashort wave spread spectrum communication system

Background

Ultrashort wave frequency bands used in fishery is 27.5-39.5 MHz with a width of 12 MHz.

Due to relatively high frequency, emitted sky waves will generally penetrate through ionosphere and shoot into the space, but cannot be reflected back to the ground by the ionosphere, such that the sky waves mainly rely on direct space waves for propagation, and only have limited diffraction capability. Therefore, when fishing boats are operating offshore, ultrashort wave radio communication becomes a relatively reasonable and effective communication mode.

In the current stage of application, the fishery ultrashort wave communication radio is mainly old-fashioned analog radio. A fishery ultrashort wave communication device at this stage mainly utilizes an analog communication manner, mainly includes a receiver high frequency amplifier, a frequency synthesizer, a frequency mixer, an intermediate frequency amplifier, a frequency discriminator, a squelch control circuit, a low-frequency amplifier and a voltage regulator circuit, and mainly utilizes an analog modulation method as a modulation manner.

Although the current device can basically meet the communication requirements of offshore fishing boats, that is, one fishing boat performs offshore communication with another fishing boat by using an ultrashort wave radio stations, so as to transmit voice signals and data signals.

However, due to the inherent defects of poor system anti-noise performance and low stability of analog communication, the quality of communication is seriously affected.

Summary

The purpose of the present invention is to provide an ultrashort wave spread spectrum communication system, so as to solve the above-mentioned technical problems.

In order to achieve the above purpose, an ultrashort wave spread spectrum communication system is provided, including: an analog radio frequency signal receiving unit, an analog radio frequency signal transmitting unit, an analog signal conditioning unit, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a field programmable logic gate array, and a a ; ; ; LU502869 high-speed real-time signal processing unit, wherein, the analog radio frequency signal receiving unit receives an analog radio frequency signal, and transmits the received signal to the analog signal conditioning unit for conditioning; the analog signal conditioning unit transmits the conditioned signal to the analog-to-digital conversion unit, so as to convert the same into a digital signal; the analog-to-digital conversion unit transmits the digital signal to the field programmable logic gate array for digital down-conversion, matched filtering, synchronous capture, PN despreading, Walsh despreading and RS decoding; the field programmable logic gate array transmits the signal, which has been subjected to

RS decoding, to the high-speed real-time signal processing unit for upper-layer communication protocol and signal processing; the high-speed real-time signal processing unit transmits the signal, which has been subjected to the upper-layer communication protocol and signal processing, to the field programmable logic gate array for source encoding, RS encoding, Walsh spread spectrum, PN pseudo-random sequence spread spectrum, shaping filtering and digital up-conversion; the programmable logic gate array transmits the processed signal to the digital-to-analog conversion unit, so as to convert the same into an analog signal; the digital-to-analog conversion unit transmits the analog signal to the analog signal conditioning unit for conditioning; and the analog signal conditioning unit transmits the conditioned signal to the analog radio frequency signal transmitting unit, so as to send the signal.

Further, the upper-layer communication protocol and signal processing includes processing for an upper-layer complex protocol of a baseband signal, and processing for a voice signal and a data signal.

Further, the analog signal conditioning unit includes a wide band amplifier and a wide band filter, and the wide band amplifier and the wide band filter are used for limiting the signal bandwidth and increasing the signal amplitude.

Further, the analog radio frequency signal receiving unit and the analog radio frequency signal transmitting unit are antennas.

. . . . . . . . . LU502869

Further, the high-speed real-time signal processing unit is a high-speed real-time signal processor.

Further, the digital-to-analog conversion unit is a digital-to-analog converter (DAC); and the analog-to-digital conversion unit is an analog-to-digital converter (ADC).

Compared with the prior art, the present invention has beneficial effects as follows: (1) A software radio design mode is utilized for signal transmitting and receiving, main communication protocol works in the system are operated in the field programmable logic gate array, and main signal processing works are realized in the high-speed real-time signal processing unit, thereby reducing the number of analog circuits in the system, ensuring smaller noise introduced by a front end and smaller signal distortion, and improving the stability of the system. (2) A spread spectrum communication method is utilized in signal modulation and demodulation, a direct sequence spread spectrum part is added to a sending end, a corresponding despreading code is used on a receiving end for despreading, so as to recover original data. In the aspect of spread spectrum encoding, Walsh encoding is compounded with a PN pseudo-random sequence, and an RS error correction encoding method is utilized, such that the present system has good performance in terms of orthogonality and error correction, and the anti-noise performance of the system is improved.

Brief Description of the Drawings

Fig. 1 is an overall structural block diagram of an ultrashort wave spread spectrum communication system in the present invention;

Fig. 2 is a working flow diagram of the ultrashort wave spread spectrum communication system in the present invention;

Fig. 3 is a sending flow diagram of the ultrashort wave spread spectrum communication system in the present invention; and

Fig. 4 is a receiving flow diagram of the ultrashort wave spread spectrum communication system in the present invention.

Detailed Description of the Embodiments

The present invention will be described in detail below with reference to various embodiments shown in the drawings, but it should be noted that these embodiments do not limit oo _ LU502869 the present invention. Equivalent transformations or substitutions, made by those of ordinary skill in the art to the functions, methods or structures according to these embodiments, all fall within the protection scope of the present invention.

Referring to Fig. 1 to Fig. 4, Fig. 1 is an overall structural block diagram of an ultrashort wave spread spectrum communication system in the present invention; Fig. 2 is a working flow diagram of the ultrashort wave spread spectrum communication system in the present invention;

Fig. 3 is a sending flow diagram of the ultrashort wave spread spectrum communication system in the present invention; and Fig. 4 is a receiving flow diagram of the ultrashort wave spread spectrum communication system in the present invention.

In the present embodiment, an ultrashort wave spread spectrum communication system includes: an analog radio frequency signal receiving unit 10, an analog radio frequency signal transmitting unit 20, an analog signal conditioning unit 30, an analog-to-digital conversion unit 40, a digital-to-analog conversion unit 50, a field programmable logic gate array 60, and a high-speed real-time signal processing unit 70; the analog radio frequency signal receiving unit 10 receives an analog radio frequency signal, and transmits the received signal to the analog signal conditioning unit 30 for conditioning; the analog signal conditioning unit 30 transmits the conditioned signal to the analog-to-digital conversion unit 40, so as to convert the same into a digital signal; the analog-to-digital conversion unit 40 transmits the digital signal to the field programmable logic gate array 60 for underlying signal processing, including digital down-conversion, matched filtering, synchronous capture, PN despreading, Walsh despreading and RS decoding; the field programmable logic gate array 60 transmits the signal, which has been subjected to

RS decoding, to the high-speed real-time signal processing unit 70 for upper-layer communication protocol and signal processing, wherein the upper-layer communication protocol and signal processing includes processing for an upper-layer complex protocol of a baseband signal, and processing for a voice signal and a data signal, the high-speed real-time signal processing unit 70 transmits the signal, which has been subjected to the upper-layer communication protocol and signal processing, to the field a a ; — LU502869 programmable logic gate array 60 underlying signal processing, including source encoding, RS encoding, Walsh spread spectrum, PN pseudo-random sequence spread spectrum, shaping filtering and digital up-conversion; the field programmable logic gate array 60 transmits the processed signal to the digital-to-analog conversion unit 50, so as to convert the same into an analog signal; the digital-to-analog conversion unit 50 transmits the analog signal to the analog signal conditioning unit 30 for conditioning; and the analog signal conditioning unit 30 transmits the conditioned signal to the analog radio frequency signal transmitting unit 20, so as to send the signal.

In the present embodiment, the analog signal conditioning unit 30 includes a wide band amplifier and a wide band filter; and the wide band amplifier and the wide band filter are used for limiting the signal bandwidth and increasing the signal amplitude.

In the present embodiment, the analog radio frequency signal receiving unit 10 and the analog radio frequency signal transmitting unit 20 are antennas.

In the present embodiment, the high-speed real-time signal processing unit 70 is a high-speed real-time signal processor.

In the present embodiment, the digital-to-analog conversion unit 50 is a digital-to-analog converter (DAC); and the analog-to-digital conversion unit 40 is an analog-to-digital converter (ADC).

The workflow of the present embodiment mainly includes the following steps: (1) performing, in the field programmable logic gate array (FPGA), Walsh spread spectrum,

PN spread spectrum, shaping filtering and digital up-conversion on a baseband code element of a sending end, which is processed by the high-speed real-time signal processor; (2) converting, by means of the digital-to-analog converter (DAC), the signal processed by the field programmable logic gate array (FPGA) into an analog signal, and sending the analog signal by means of an antenna after modulating the same; (3) converting, by means of the analog-to-digital converter (ADC), the signal received by the antenna into a digital signal after passıng through the wide band filter and the wide band amplifier, and sending the signal to the field programmable logic gate array (FPGA) for despreading; and

(4) sending the signal despread by the field programmable gate array (FPGA) into the high-speed real-time signal processor for subsequent code element processing and signal processing.

The sending part of the present embodiment includes the following process: after source information is subjected to source encoding, in order to improve the error correction capability of the system, error correction encoding needs to be performed on the source information. In multi-system spread spectrum communication, if there is an error in a related despreading result, the error will occur together in a plurality of bit units, so that RS encoding is used as an error correction code in the present embodiment. The data bit length of the signal can be increased by Walsh conversion, such that the anti-noise performance of the signal is improved, and due to the correlation of Walsh, the converted signal has certain fault-tolerant capability. Therefore, in the present embodiment, Walsh spread spectrum is carried out after RS encoding, and the anti-noise performance of the system can be effectively improved after Walsh spread spectrum is carried out. In fishery ultrashort wave communication, signal transmission is asynchronous transmission, in this case, an auto-correlation function and a cross-correlation function of a Walsh code are not ideal, moreover, power spectrum distributions of code sequences of the Walsh code are not uniform, and thus cannot independently undertake a spread spectrum task. Accordingly, in the present embodiment, a pseudo-random code PN sequence with better correlation is constructed to perform pseudo-randomization on the data, and after the pseudo-randomization of the PN sequence, the characteristics of the correlation functions are improved, sidelobes are reduced, and good asynchronous correlation is achieved.

Before modulation, it is necessary to perform one-time shaping filtering on the signal, so as to limit the frequency bandwidth occupied by the signal, digital up-conversion carrier modulation is performed on the signal, the modulated signal is output to the DAC, so as to complete the conversion from the digital signal to the analog signal, and the signal is sent to a space infinite channel by means of an analog radio frequency transmitter.

The receiving part of the present embodiment includes the following processes:

Digital down-conversion processing is firstly performed on the digital signal, which has been subjected to ADC conversion, so as to carry the signal to a baseband for processing, and meanwhile, the signal rate is reduced. A baseband signal after down-conversion firstly needs to pass through a matched filter, and the matched filter and a shaping filter of the sending end together achieve the effect of improving the signal-to-noise ratio of the system. After passing through the matched filter, synchronous capture is performed in the present embodiment, so as to determine received useful information. Synchronous capture is a key point of the system, if correct capture fails, subsequent despreading and decoding processing is meaningless processing.

The highest peak of a correlation value is solved by using a sliding correlation method in the present embodiment, and an effective starting point is obtained by synchronous capture. After synchronous capture, it is necessary to perform PN despreading and pseudo-randomization, and then to perform Walsh correlation and judgment, so as to obtain an RS symbol to be decoded.

By means of providing the ultrashort wave spread spectrum communication system, the present invention has beneficial effects as follows: (1) A software radio design mode is utilized for signal transmitting and receiving, main communication protocol works in the system are operated in the field programmable logic gate array, and main signal processing works are realized in the high-speed real-time signal processing unit, thereby reducing the number of analog circuits in the system, ensuring smaller noise introduced by a front end and smaller signal distortion, and improving the stability of the system. Meanwhile, the communication protocol and signal processing method in the system can be changed modifying software, thereby facilitating the upgrade of the system. (2) A spread spectrum communication method is utilized in signal modulation and demodulation, a direct sequence spread spectrum part is added to the sending end, a corresponding despreading code is used on the receiving end for despreading, so as to recover original data. In the aspect of spread spectrum encoding, Walsh encoding is compounded with a

PN pseudo-random sequence, and an RS error correction encoding method is utilized, such that the present system has good performance in terms of orthogonality and error correction, and the anti-noise performance of the system is improved.

The series of detailed descriptions listed above are only specific descriptions for feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes, made without departing from the technical spirit of the present invention, should all be included within the protection scope of the present invention.

It will be apparent to those skilled in the art that, the present invention is not limited to the details of the above exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, the scope of the present invention is defined by the appended claims rather than by the foregoing descriptions.

Accordingly, all changes, within the meanings and scope of the equivalents of the claims, are compassed in the present invention, and any reference signs in the claims should not be construed as limiting the involved claims.

Claims

1. An ultrashort wave spread spectrum communication system, comprising: an analog radio frequency signal receiving unit, an analog radio frequency signal transmitting unit, an analog signal conditioning unit, an analog-to-digital conversion unit, a digital-to-analog conversion unit, a field programmable logic gate array, and a high-speed real-time signal processing unit, wherein, the analog radio frequency signal receiving unit receives an analog radio frequency signal, and transmits the received signal to the analog signal conditioning unit for conditioning; the analog signal conditioning unit transmits the conditioned signal to the analog-to-digital conversion unit, so as to convert the same into a digital signal; the analog-to-digital conversion unit transmits the digital signal to the field programmable logic gate array for digital down-conversion, matched filtering, synchronous capture, PN despreading, Walsh despreading and RS decoding; the field programmable logic gate array transmits the signal, which has been subjected to RS decoding, to the high-speed real-time signal processing unit for upper-layer communication protocol and signal processing; the high-speed real-time signal processing unit transmits the signal, which has been subjected to the upper-layer communication protocol and signal processing, to the field programmable logic gate array for source encoding, RS encoding, Walsh spread spectrum, PN pseudo-random sequence spread spectrum, shaping filtering and digital up-conversion; the programmable logic gate array transmits the processed signal to the digital-to-analog conversion unit, so as to convert the same into an analog signal; the digital-to-analog conversion unit transmits the analog signal to the analog signal conditioning unit for conditioning; and the analog signal conditioning unit transmits the conditioned signal to the analog radio frequency signal transmitting unit, so as to send the signal.

2. The ultrashort wave spread spectrum communication system according to claim 1, wherein the upper-layer communication protocol and signal processing comprises processing for an upper-layer complex protocol of a baseband signal, and processing for a voice signal and a data signal.

3. The ultrashort wave spread spectrum communication system according to claim 2, wherein the analog signal conditioning unit comprises a wide band amplifier and a wide band filter, and the wide band amplifier and the wide band filter are used for limiting the signal bandwidth and increasing the signal amplitude.

4. The ultrashort wave spread spectrum communication system according to claim 3, wherein the analog radio frequency signal receiving unit and the analog radio frequency signal transmitting unit are antennas.

5. The ultrashort wave spread spectrum communication system according to claim 4, wherein the high-speed real-time signal processing unit is a high-speed real-time signal processor.

6. The ultrashort wave spread spectrum communication system according to claim 1, wherein the digital-to-analog conversion unit is a digital-to-analog converter (DAC); and the analog-to-digital conversion unit is an analog-to-digital converter (ADC).