WO2020073454A1 - 一种信号调制、解调方法及跳相调制、解调单元 - Google Patents

一种信号调制、解调方法及跳相调制、解调单元 Download PDF

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WO2020073454A1
WO2020073454A1 PCT/CN2018/118081 CN2018118081W WO2020073454A1 WO 2020073454 A1 WO2020073454 A1 WO 2020073454A1 CN 2018118081 W CN2018118081 W CN 2018118081W WO 2020073454 A1 WO2020073454 A1 WO 2020073454A1
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phase
signal
hopping sequence
hopping
control
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French (fr)
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唐祖平
魏蛟龙
杨明
叶斌
夏景圆
刘昊
李瑞博
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华中科技大学
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/7136—Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/715—Interference-related aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/001—Modulated-carrier systems using chaotic signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/715—Interference-related aspects
    • H04B2001/7152—Interference-related aspects with means for suppressing interference

Definitions

  • the invention belongs to the technical field of signal modulation, and more specifically, relates to a signal modulation and demodulation method and a phase-hopping modulation and demodulation unit.
  • the key data such as aerospace telemetry, measurement and control, external measurement, and range experiment, as well as the security, reliability, and anti-stealing of satellite navigation military signals are critical to national security. Enemy information detection will seriously threaten the launch and flight safety of various spacecraft. Therefore, the reliability requirements of wireless communication signals in special tasks and the importance of communication security make new wireless communication systems have to have good security capabilities.
  • Modern wireless communication systems usually use frequency hopping and spread spectrum to resist interception and interference. With the improvement of interception capability and signal recognition processing algorithm capabilities, the basic hopping spread spectrum anti-interception and anti-interference capabilities become increasingly weak.
  • the current ability to improve interception resistance is mainly based on spread spectrum and frequency hopping. On the one hand, it increases the bandwidth of the hopping speed and frequency set.
  • the present invention provides a signal modulation method and a phase-hopping modulation and demodulation unit, and its purpose is to improve the security performance of the wireless communication system without increasing the system bandwidth.
  • the present invention provides a signal modulation method, including the following steps:
  • phase-hopping sequence generator Under the control of the clock reference, a phase-hopping sequence generator generates a phase-hopping sequence
  • the waveform of each chip in the modulated signal is phase-shifted accordingly to obtain a modulated signal.
  • phase-hopping sequence c (n) is N-ary, and c (n) ⁇ ⁇ 0,1,2 ... N-1 ⁇ ; shift The minimum interval between two phase shifts is
  • the modulation signal among them Is the phase shift factor; the initial phase of the signal in each chip is in the range of 0 to 360 degrees The resolution of degrees varies randomly.
  • the invention also provides a signal demodulation method, including the following steps:
  • phase-hopping sequence generator Under the control of the clock reference, a phase-hopping sequence generator generates a phase-hopping sequence
  • the waveform of each chip in the demodulated signal is phase-shifted accordingly to obtain a demodulated signal.
  • phase-hopping sequence c (n) is N-ary, and c (n) ⁇ ⁇ 0,1,2 ... N-1 ⁇ , the phase deviation corresponding to the phase-hopping sequence c (n) shift
  • the minimum interval between two phase shifts is
  • the demodulated signal among them Is the phase compensation factor.
  • the invention also provides a phase-hopping modulation unit, which includes: a phase shifter and a phase-hopping sequence generator.
  • the input end of the phase-hopping sequence generator is used to connect a clock reference and is used to generate a jump under the control of the clock reference Phase sequence;
  • the input end of the phase shifter is used to receive the signal to be modulated,
  • the control end of the phase shifter is connected to the output end of the phase-hopping sequence generator, the phase shifter is in the phase-hopping sequence Under the control of, the waveform of each chip in the signal to be modulated is correspondingly phase-shifted, and the modulated signal is output from the output terminal.
  • the phase-hopping sequence generator may be a chaotic sequence generator or an R-S sequence generator.
  • the invention provides a phase-hopping demodulation unit, comprising: a phase compensator and a phase-hopping sequence generator; the input end of the phase-hopping sequence generator is used to connect to a synchronization system, and is used to generate a jump under the control of a clock reference Phase sequence; the input end of the phase compensator is used to receive the signal to be demodulated, the control end of the phase compensator is connected to the output end of the phase-hopping sequence generator, the phase compensator is in the phase-hopping Under the control of the sequence, the waveform of each chip in the signal to be demodulated is phase-shifted accordingly, and the demodulated signal is output from the output terminal.
  • the present invention has the following technical advantages:
  • This phase-hopping modulation technique is equivalent to performing secondary PSK modulation on the signal, so that the modulated signal is close to the noise characteristics, which can improve the anti-detection performance of the signal.
  • DSSS direct sequence spread spectrum signal
  • DS / PH direct sequence spread spectrum + phase hopping signal
  • the modulation signal is close to the noise characteristic, which is more difficult to be found and identified.
  • the carrier phase of the phase-hopping signal is within the range of 0 to 360 degrees
  • the resolution of the degree (the phase skip sequence is N-ary) changes randomly. This random phase jump makes it difficult for the receiver to obtain the original information at the physical level, which significantly enhances the signal's ability to resist interception.
  • FIG. 1 is a schematic structural diagram of a phase-hopping modulation unit provided by an embodiment of the present invention.
  • FIG. 2 is a schematic structural diagram of a phase-hopping demodulation unit provided by an embodiment of the present invention.
  • phase-hopping sequence generator provided by an embodiment of the present invention
  • phase shifter 4 is a functional block diagram of a phase shifter provided by an embodiment of the present invention.
  • FIG. 5 is the power spectral density of a direct-spreading / phase-hopping signal provided by an embodiment of the present invention
  • FIG. 6 is a schematic diagram of time-domain waveforms of the I branch and the Q branch of the DS / PH signal provided by an embodiment of the present invention
  • FIG. 7 is a schematic diagram of an oversampled modulation constellation provided by an embodiment of the present invention.
  • FIG. 8 is a schematic diagram of a modulation constellation of code rate sampling provided by an embodiment of the present invention.
  • FIG. 9 is a vector diagram of a phase-hopping signal provided by an embodiment of the present invention.
  • FIG. 10 shows the antenna gain improvement required for demodulating the phase-hopping sequence provided by the embodiment of the present invention.
  • the invention can be applied to wireless communication or navigation signal modulation with higher security requirements.
  • the invention can improve the security performance of the wireless communication system without increasing the system bandwidth.
  • the invention discloses a signal modulation technique: a modulation technique of carrier phase hopping.
  • the modulation can be directed to a variety of signals, such as baseband signals, radio frequency signals, and carrier waves, etc., and can be used as input signals for the modulation unit or the demodulation unit.
  • This modulation can also be regarded as secondary modulation after basic modulation (PSK, QAM modulation, etc.).
  • the phase-hopping sequence generator generates a pseudo-random sequence, which is used as a phase-hopping sequence.
  • the phase-hopping sequence controls the phase shifter, so that the initial phase of the input signal in each chip changes with the phase-hopping sequence jump, and the output signal is obtained.
  • the output signal can be processed according to different requirements and then transmitted through the antenna.
  • the same phase sequence generator as the transmitting end generates the phase-hopping sequence, and controls the phase compensator (essentially a phase shifter, so that the initial phase of the demodulator input signal within each chip It changes in accordance with the phase-hopping sequence.
  • This phase-hopping and the phase-hopping of the modulator at the transmitting end are just complementary.) Compensate the signal to achieve the purpose of phase-hopping.
  • DSSS direct sequence spread spectrum
  • the receiver in order to steal valid information, the receiver must decipher the spread spectrum sequence, that is, correctly demodulate the spread sequence symbol.
  • the gain of the detection antenna is sufficient to demodulate the direct sequence spread spectrum signal. If the signal is phase-hopped, the receiver must decipher the phase-hopping sequence in order to steal valid information. Therefore, phase-hopping modulation improves the anti-detection performance of the signal.
  • the phase hopping sequence is N-ary. Therefore, in order to demodulate the phase-hopping sequence, the ratio of the minimum Es / N0 (symbol signal-to-noise ratio) required to the minimum Es / N0 required to demodulate the spreading sequence is For a direct-spread signal modulated by phase-hopping, the minimum Es / N0 required to demodulate the phase-hopping sequence is higher than the traditional DSSS signal by G PH . Therefore, the anti-detection ability of the signal is improved.
  • the phase-hopping modulation unit includes: a phase shifter and a phase-hopping sequence generator.
  • the input terminal of the phase-hopping sequence generator is used to connect a clock reference, and is used to generate a phase-hopping sequence c under the control of the clock reference. (n); the input terminal of the phase shifter is used to receive the signal to be modulated, the control terminal of the phase shifter is connected to the output terminal of the phase-hopping sequence generator, and the phase shifter is to be modulated under the control of the phase-hopping sequence c (n)
  • the waveform of each chip in the signal undergoes a corresponding phase shift and the modulation signal T out (t) is output from the output terminal.
  • the input signal T in (t) can be a variety of signals: baseband signals, radio frequency signals, or carrier waves.
  • the phase-hopping sequence generator Under the control of the clock reference, the phase-hopping sequence generator generates an N-ary phase-hopping sequence c (n), and the corresponding phase offset is: Where c (n) ⁇ ⁇ 0,1,2 ... N-1 ⁇ , the minimum interval between two phase shifts is
  • the phase shifter shifts the waveform of each chip of T in (t) to different degrees to obtain T out (t): among them Is the phase shift factor.
  • the phase-hopping sequence generator may be a chaotic sequence generator or an R-S sequence generator.
  • the phase-hopping demodulation unit includes: a phase compensator and a phase-hopping sequence generator; the input terminal of the phase-hopping sequence generator is used to connect to a synchronization system, and is used to generate a phase-hopping sequence under the control of a clock reference c (n); the input end of the phase compensator is used to receive the signal to be demodulated, the control end of the phase compensator is connected to the output end of the phase-hopping sequence generator, and the phase compensator is connected to the phase-hopping sequence c (n). Under control, the waveform of each chip in the demodulated signal is phase-shifted accordingly, and the demodulated signal R out (t) is output from the output terminal.
  • the input signal R in (t) can also be a variety of signals: baseband signals, radio frequency signals, or carrier waves.
  • the phase-hopping sequence generator Under the control of the clock reference, the phase-hopping sequence generator generates an N-ary phase-hopping sequence c (n), and the corresponding phase offset is: Where c (n) ⁇ ⁇ 0,1,2 ... N-1 ⁇ , the minimum interval between two phase shifts is
  • the phase compensator can shift the phase of each chip of R in (t) to different degrees to obtain R out (t): among them Is the phase compensation factor.
  • the phase-hopping sequence should be designed to be random enough and complex enough.
  • the generation of the phase skip sequence is divided into two steps:
  • Step one mapping.
  • the state of the original sequence x (n) generated by the mapping at time x n + 1 can be expressed as a combination of the past k time states.
  • chaotic maps are widely used, which have the characteristics of high initial value sensitivity, inherent randomness, infinite self-similarity, local instability and overall stability.
  • Step 2 Quantization coding.
  • Quantization coding maps the original sequence x (n) to the phase-hopping sequence c (n).
  • the quantization coding can be uniform or non-uniform, and the corresponding choice can be made according to the actual situation.
  • the simplest form is linear uniform quantization coding, the mathematical expression is:
  • phase shifter of the modulation unit and the phase compensator of the demodulation unit are essentially phase shifters.
  • a phase shifter is a device that can adjust the phase of a waveform.
  • phase shift factor Through Euler's equation it is expanded to:
  • the output of the phase shifter is:
  • the corresponding block diagram of the phase shifter is shown in Figure 4. Where I out is the I branch component of the output signal, and Q out is the Q branch component of the output signal:
  • the signal modulation method includes a modulation step and a demodulation step; wherein, the modulation step includes:
  • the input signal T in (t) can be a variety of signals: baseband signal, radio frequency signal or carrier wave.
  • the phase-hopping sequence generator Under the control of the clock reference, the phase-hopping sequence generator generates an N-ary phase-hopping sequence c (n), the corresponding phase offset is among them The minimum interval between two phase shifts is The greater N, The smaller it is, the more difficult it is to demodulate the phase-hopping sequence.
  • T out (t) is the signal after phase-hop modulation
  • the initial phase of this signal in each chip is in the range of 0 to 360 degrees.
  • the resolution of the degree (the phase skip sequence is N-ary) changes randomly.
  • the carrier phase of the phase-hopping signal is in the range of 0 to 360 degrees
  • the resolution of the degree (the phase skip sequence is N-ary) changes randomly. This random phase jump makes it difficult for the receiver to obtain information at the physical level, which significantly enhances the signal's ability to resist interception.
  • the demodulation steps include:
  • the input signal R in (t) can also be a variety of signals: baseband signals, radio frequency signals, or carrier waves.
  • the input signal R in (t) should correspond to the output signal of the modulation unit.
  • phase-hopping sequence generator Under the control of the clock reference, the same phase-hopping sequence generator as the modulation unit generates an N-ary phase-hopping sequence c (n), and the corresponding phase offset is Where c (n) ⁇ ⁇ 0,1,2 ... N-1 ⁇ , the minimum interval between two phase shifts is
  • phase compensator (essentially a phase shifter) performs a different degree of phase shift on the waveform of each chip of R in (t) to obtain R out (t): among them Is the phase compensation factor. This completes the process of understanding phase skipping.
  • the phase-hopping modulation technique provided by the present invention is equivalent to performing a second PSK modulation on the signal, so that the modulated signal is close to the noise characteristic, which can improve the anti-detection performance of the signal.
  • DSSS direct sequence spread spectrum signal
  • DS / PH direct sequence spread spectrum + phase hopping signal
  • the modulated signal is close to the noise characteristic, which is more difficult to find and identify.
  • the detection party since the detection party must obtain useful information, it must first demodulate and decipher the phase-hopping sequence.

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Abstract

本发明公开了一种信号调制、解调方法及跳相调制、解调单元，其中信号调制方法包括：(1)在时钟基准的控制下通过跳相序列发生器产生跳相序列；(2)在跳相序列的控制下对待调制信号中每个码片的波形进行相应的移相后获得调制信号；跳相调制单元包括：移相器和跳相序列发生器，跳相序列发生器的输入端用于连接时钟基准，用于在时钟基准的控制下产生跳相序列；移相器的输入端用于接收待调制信号，移相器的控制端连接至跳相序列发生器的输出端，移相器在跳相序列的控制下对待调制信号中每个码片的波形进行相应的移相后由输出端输出调制信号。本发明相当于对信号进行了二次PSK调制，使得调制信号接近噪声特性，能够提高信号的抗检测性能。

Description

一种信号调制、解调方法及跳相调制、解调单元 【技术领域】
本发明属于信号的调制技术领域，更具体地，涉及一种信号调制、解调方法及跳相调制、解调单元。
【背景技术】
航天遥测、测控、外测、靶场实验等关键数据以及卫星导航军用信号的保密性、可靠性以及反窃取对于国家安全至关重要。敌方信息侦测将严重威胁各类航天器发射与飞行安全。因此，无线通信信号在特殊任务中可靠性需求及通信安全的重要性，使得无线通信新系统不得不具备良好的保密能力。现代无线通信系统通常采用跳频和扩频方式来抗截获及抗干扰，随着截获能力和信号识别处理算法能力的提高，基本的跳扩频抗截获及抗干扰能力显得日益薄弱。当前提高抗截获的能力主要是以扩频和跳频为基础，一方面提高跳速和频率集的带宽，一方面采用差分跳频和自适应跳频等新的跳频方式。这些方法存在硬件开销较大、组网规划比较困难、实时性很差等问题。尽管常规跳频技术、差分跳频技术和自适应跳频技术都已经可以对抗大部分的截获和干扰方式，但是在对抗日益发展的截获技术和干扰技术时，其性能仍不能满足某些特殊场景下无线通信的需求。
随着日益增长的电子战威胁，无线通信的风险和易受到截获及干扰的程度也随之增加，为了确保无线通信系统的安全和可靠性，迫切需要提出新的简单实用的抗截获方法。
【发明内容】
针对现有技术的缺陷，本发明提供了一种信号调制方法及跳相调制解调单元，其目的在于在不增加系统带宽的情况下，提高无线通信系统的保密性能。
本发明提供了一种信号调制方法，包括下述步骤：
(1)在时钟基准的控制下通过跳相序列发生器产生跳相序列；
(2)在跳相序列的控制下对待调制信号中每个码片的波形进行相应的移相后获得调制信号。
其中，跳相序列c(n)为N进制，且c(n)∈{0,1,2......N-1}；所述跳相序列c(k)对应的相位偏移
Figure PCTCN2018118081-appb-000001
两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000002
其中，调制信号
Figure PCTCN2018118081-appb-000003
其中
Figure PCTCN2018118081-appb-000004
为移相因子；信号在每个码片内的初始相位在0～360度范围内以
Figure PCTCN2018118081-appb-000005
度的分辨率随机变化。
本发明还提供了一种信号解调方法，包括下述步骤：
(1)在时钟基准的控制下通过跳相序列发生器产生跳相序列；
(2)在跳相序列的控制下对待解调信号中每个码片的波形进行相应的移相后获得解调信号。
其中，跳相序列c(n)为N进制，且c(n)∈{0,1,2......N-1}，所述跳相序列c(n)对应的相位偏移
Figure PCTCN2018118081-appb-000006
两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000007
其中，解调信号
Figure PCTCN2018118081-appb-000008
其中
Figure PCTCN2018118081-appb-000009
为相位补偿因子。
本发明还提供了一种跳相调制单元，包括：移相器和跳相序列发生器，所述跳相序列发生器的输入端用于连接时钟基准，用于在时钟基准的控制下产生跳相序列；所述移相器的输入端用于接收待调制信号，所述移相器的控制端连接至所述跳相序列发生器的输出端，所述移相器在所述跳相序列的控制下对所述待调制信号中每个码片的波形进行相应的移相后由输出端输出调制信号。
其中，跳相序列发生器可以为混沌序列发生器或R-S序列发生器等。
本发明提供了一种跳相解调单元，包括：相位补偿器和跳相序列发生 器；所述跳相序列发生器的输入端用于连接同步系统，用于在时钟基准的控制下产生跳相序列；所述相位补偿器的输入端用于接收待解调信号，所述相位补偿器的控制端连接至所述跳相序列发生器的输出端，所述相位补偿器在所述跳相序列的控制下对所述待解调信号中每个码片的波形进行相应的移相后由输出端输出解调信号。
通过本发明所构思的以上技术方案，与现有技术相比，本发明具有如下技术优点：
(1)抗检测性能：这种跳相的调制技术相当于对信号进行了二次PSK调制，使得调制信号接近噪声特性，这样能够提高信号的抗检测性能。例如，对直接序列扩频信号(DSSS)和直接序列扩频+跳相信号(DS/PH)进行分析，如果跳相频率和伪码频率相同，那么DS/PH信号的频谱和DSSS信号具有相同的特征。根据对波形的观测，综合可见调制信号接近噪声特性，更难被发现和识别。
(2)抗截获性能：跳相信号的载波相位在0～360度范围内以
Figure PCTCN2018118081-appb-000010
度(跳相序列为N进制)的分辨率随机变化。这种随机的相位跳变，使得接收方在物理层面上无法轻易的获取原始信息，显著增强信号的抗截获能力。
(3)抗侦收性能：由于侦收方要获取原始信息，必须要先解调并破译出跳相序列，跳相序列的进制N越大，跳相序列的解调难度越大，因此这种调制技术具有显著的抗侦收能力。
【附图说明】
图1本发明实施例提供的跳相调制单元的结构示意图；
图2本发明实施例提供的跳相解调单元的结构示意图；
图3本发明实施例提供的跳相序列发生器原理框图；
图4本发明实施例提供的移相器原理框图；
图5本发明实施例提供的直扩/跳相信号的功率谱密度；
图6本发明实施例提供的直扩/跳相信号I支路和Q支路的时域波形示意图；
图7本发明实施例提供的过采样的调制星座示意图；
图8本发明实施例提供的码率采样的调制星座示意图；
图9本发明实施例提供的跳相信号的矢量图；
图10本发明实施例提供的解调跳相序列所需的天线增益提升。
【具体实施方式】
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明可以应用于具有较高保密需求的无线通信或导航信号调制。本发明可以在不增加系统带宽的情况下提高无线通信系统保密性能。
本发明公开了一种信号调制技术：载波相位跳变的调制技术。该调制可以针对多种信号，例如基带信号、射频信号以及载波等，都可以作为调制单元或解调单元的输入信号。该调制也可以看作是基本调制(PSK、QAM调制等)之后的二次调制。跳相序列发生器产生伪随机序列，作为跳相序列使用。对于发送端的调制单元，跳相序列控制移相器，使得输入信号在每个码片内的初始相位随着跳相序列的跳变而改变，得到输出信号。随后输出信号可以根据需求进行不同的处理之后再通过天线发射出去。对于接收端的解调单元，与发送端相同的相位序列发生器产生跳相序列，控制相位补偿器(本质上也是移相器，使得解调器的输入信号在每个码片内的初始相位随着跳相序列而改变，这种相位跳变与发送端调制器的相位跳变刚好是互补关系)对信号进行相位补偿，达到解跳相的目的。
为了更进一步的说明本发明实施例提供的信号调制、解调方法及调制、解调单元，下面通过直接序列扩频信号进行简要的对比分析和论述。
对于应用广泛的直接序列扩频(DSSS)信号，侦收方为了窃取有效的 信息，必须要破译扩频序列，即正确地解调出扩频序列符号。以目前的侦收技术来说，侦收天线的增益已经足够解调直接序列扩频信号。如果对信号进行跳相调制，侦收方为了窃取有效的信息，必须要破译跳相序列。因此，跳相调制提高了信号的抗侦收性能。
在本发明实施例中，直接序列扩频信号(如附图9所示)的相邻点欧几里得距离为：d 1＝2A M……(1)；其中A M为其最大振幅。此距离直接代表着噪声容限的大小。
如果对信号进行跳相调制，由图9可见信号的包络特性并未改变，跳相信号的相邻点欧几里得距离近似为(当N大于10时)：
Figure PCTCN2018118081-appb-000011
Figure PCTCN2018118081-appb-000012
其中跳相序列为N进制的。因此为了解调跳相序列，所需的最小Es/N0(符号信噪比)与解调扩频序列所需的最小Es/N0的比值为：
Figure PCTCN2018118081-appb-000013
对于跳相调制的直扩信号，解调跳相序列所需的最小Es/N0比传统DSSS信号高了G PH。因此提高了信号的抗侦收能力。
G PH与跳相序列进制N的关系如附图10所示。当N为1024(2 10)时，解调跳相序列所需的最小Es/N0比传统DSSS信号高了约50dB，显著提高了抗侦收能力。
如附图1所示，跳相调制单元包括：移相器和跳相序列发生器，跳相序列发生器的输入端用于连接时钟基准，用于在时钟基准的控制下产生跳相序列c(n)；移相器的输入端用于接收待调制信号，移相器的控制端连接至跳相序列发生器的输出端，移相器在跳相序列c(n)的控制下对待调制信号中每个码片的波形进行相应的移相后由输出端输出调制信号T out(t)。
在发送端，输入信号T in(t)可以是多种信号：基带信号、射频信号或者载波等。在时钟基准的控制下，跳相序列发生器产生N进制的跳相序列c(n)， 对应的相位偏移为：
Figure PCTCN2018118081-appb-000014
其中c(n)∈{0,1,2......N-1}，两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000015
在跳相序列c(n)的控制下，移相器对T in(t)的每个码片的波形进行不同程度的移相，得到T out(t)：
Figure PCTCN2018118081-appb-000016
其中
Figure PCTCN2018118081-appb-000017
为移相因子。
作为本发明的一个实施例，跳相序列发生器可以为混沌序列发生器或R-S序列发生器等。
如附图2所示，跳相解调单元包括：相位补偿器和跳相序列发生器；跳相序列发生器的输入端用于连接同步系统，用于在时钟基准的控制下产生跳相序列c(n)；相位补偿器的输入端用于接收待解调信号，相位补偿器的控制端连接至跳相序列发生器的输出端，相位补偿器在所述跳相序列c(n)的控制下对待解调信号中每个码片的波形进行相应的移相后由输出端输出解调信号R out(t)。
在接收端，输入信号R in(t)也可以是多种信号：基带信号、射频信号或者载波等。在时钟基准的控制下，跳相序列发生器产生N进制的跳相序列c(n)，对应的相位偏移为：
Figure PCTCN2018118081-appb-000018
其中c(n)∈{0,1,2......N-1}，两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000019
在跳相序列c(n)的控制下，相位补偿器可以对R in(t)的每个码片的波形进行不同程度的移相，得到R out(t)：
Figure PCTCN2018118081-appb-000020
其中
Figure PCTCN2018118081-appb-000021
为相位补偿因子。
跳相序列应该被设计得足够随机和足够复杂。
如附图3所示，在本发明实施例中，跳相序列的产生分为两步：
步骤一：映射。映射产生的原始序列x(n)在x n+1时刻的状态可以表示成过去k个时刻状态的组合，数学表达式为：x n+1＝f(x n,x n-1......,x n-k+1)……(8)； 其中x(n)∈[l min,l max]。
目前采用较多的是混沌映射，它具有高初值敏感性、内在随机性、无限自似性、局部不稳而整体稳定等性质。比较经典的混沌映射有Logistic映射、Tent映射、Chebyshev映射。以Tent映射为例，Tent映射产生的原始序列在x n+1时刻的状态表示成过去1个状态的组合，即k＝1，Tent映射的数学表达式为：
Figure PCTCN2018118081-appb-000022
步骤二：量化编码。量化编码将原始序列x(n)映射为跳相序列c(n)，数学表达式为：c(n)＝g(x(n))……(10)。
量化编码可以是均匀的，也可以是非均匀的，根据实际情况可以做出相应的选择。其中最简单的形式是线性均匀量化编码，数学表达式为：
Figure PCTCN2018118081-appb-000023
调制单元的移相器和解调单元的相位补偿器本质上都是移相器。移相器是能够对波形的相位进行调整的一种装置。
本发明中，移相器的原理如下：输入信号S in(t)基带形式表示为：S in(t)＝I in(t)+jQ in(t)……(12)；其中I in(t)表示I支路分量，Q in(t)表示Q支路分量。
将相位偏移因子
Figure PCTCN2018118081-appb-000024
通过欧拉方程展开为：
Figure PCTCN2018118081-appb-000025
则移相器的输出为：
Figure PCTCN2018118081-appb-000026
Figure PCTCN2018118081-appb-000027
移相器对应的原理框图如附图4所示。其中I out为输出信号的I支路分量，Q out为输出信号的Q支路分量：
Figure PCTCN2018118081-appb-000028
Figure PCTCN2018118081-appb-000029
本发明实施例中，信号调制方法包括调制步骤和解调步骤；其中，调制步骤包括：
(1)输入待调制信号，输入信号T in(t)可以是多种信号：基带信号、射频信号或者载波等。
(2)在时钟基准的控制下，跳相序列发生器产生N进制的跳相序列c(n)，对应的相位偏移为：
Figure PCTCN2018118081-appb-000030
其中
Figure PCTCN2018118081-appb-000031
两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000032
N越大，
Figure PCTCN2018118081-appb-000033
越小，解调跳相序列越困难。
(3)在跳相序列c(n)的控制下，移相器对T in(t)的每个码片的波形进行不同程度的移相，得到Tout(t)：
Figure PCTCN2018118081-appb-000034
其中
Figure PCTCN2018118081-appb-000035
为移相因子。此时的T out(t)即经过跳相调制之后的信号，此信号在每个码片内的初始相位在0～360度范围内以
Figure PCTCN2018118081-appb-000036
度(跳相序列为N进制)的分辨率随机变化。
本发明中，跳相信号的载波相位在0～360度范围内以
Figure PCTCN2018118081-appb-000037
度(跳相序列为N进制)的分辨率随机变化。这种随机的相位跳变，使得接收方在物理层面上无法轻易的获取信息，显著增强信号的抗截获能力。
解调步骤包括：
(1)输入待解调信号。输入信号R in(t)也可以是多种信号：基带信号、射频信号或者载波等。输入信号R in(t)应与调制单元的输出信号相对应。
(2)在时钟基准的控制下，与调制单元中相同的跳相序列发生器产生N进制的跳相序列c(n)，对应的相位偏移为：
Figure PCTCN2018118081-appb-000038
其中c(n)∈{0,1,2......N-1}，两个相位偏移之间的最小间隔为
Figure PCTCN2018118081-appb-000039
(3)在跳相序列c(n)的控制下，相位补偿器(本质上是一个移相器)对R in(t)的每个码片的波形进行不同程度的移相，得到R out(t)：
Figure PCTCN2018118081-appb-000040
其中
Figure PCTCN2018118081-appb-000041
为相位补偿因子。此即完成了解跳相的过程。
本发明提供的这种跳相的调制技术相当于对信号进行了二次PSK调制，使得调制信号接近噪声特性，这样能够提高信号的抗检测性能。例如，对直接序列扩频信号(DSSS)和直接序列扩频+跳相信号(DS/PH)进行分析，如果跳相频率和伪码频率相同，那么DS/PH信号的频谱和DSSS信号具有相同的特征(如附图5)。根据对波形的观测(附图6-8)，综合可见调制信号接近噪声特性，更难被发现和识别。同时，由于侦收方要获取有用信息，必须要先解调并破译出跳相序列，跳相序列的进制N越大，跳相序列的解调难度越大，因此这种调制技术具有显著的抗侦收能力。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (8)

  1. 一种信号调制方法，其特征在于，包括下述步骤：
    (1)在时钟基准的控制下通过跳相序列发生器产生跳相序列；
    (2)在所述跳相序列的控制下对待调制信号中每个码片的波形进行相应的移相后获得调制信号。
  2. 如权利要求1所述的信号调制方法，其特征在于，所述跳相序列c(n)为N进制，且c(n)∈{0,1,2......N-1}；所述跳相序列c(n)对应的相位偏移
    Figure PCTCN2018118081-appb-100001
    两个相位偏移之间的最小间隔为
    Figure PCTCN2018118081-appb-100002
  3. 如权利要求1或2所述的信号调制方法，其特征在于，所述调制信号
    Figure PCTCN2018118081-appb-100003
    其中
    Figure PCTCN2018118081-appb-100004
    为移相因子；信号在每个码片内的初始相位在0～360度范围内以
    Figure PCTCN2018118081-appb-100005
    度的分辨率随机变化。
  4. 一种信号解调方法，其特征在于，包括下述步骤：
    (1)在时钟基准的控制下通过跳相序列发生器产生跳相序列；
    (2)在跳相序列的控制下对待解调信号中每个码片的波形进行相应的移相后获得解调信号。
  5. 如权利要求4所述的信号解调方法，其特征在于，所述跳相序列c(n)为N进制，且c(n)∈{0,1,2......N-1}，所述跳相序列c(n)对应的相位偏移
    Figure PCTCN2018118081-appb-100006
    两个相位偏移之间的最小间隔为
    Figure PCTCN2018118081-appb-100007
  6. 如权利要求4或5所述的信号解调方法，其特征在于，所述解调信号
    Figure PCTCN2018118081-appb-100008
    其中
    Figure PCTCN2018118081-appb-100009
    为相位补偿因子。
  7. 一种跳相调制单元，其特征在于，包括：移相器和跳相序列发生器，
    所述跳相序列发生器的输入端用于连接时钟基准，用于在时钟基准的控制下产生跳相序列；
    所述移相器的输入端用于接收待调制信号，所述移相器的控制端连接至所述跳相序列发生器的输出端，所述移相器在所述跳相序列的控制下对所述待调制信号中每个码片的波形进行相应的移相后由输出端输出调制信号。
  8. 一种跳相解调单元，其特征在于，包括：相位补偿器和跳相序列发生器；
    所述跳相序列发生器的输入端用于连接同步系统，用于在时钟基准的控制下产生跳相序列；
    所述相位补偿器的输入端用于接收待解调信号，所述相位补偿器的控制端连接至所述跳相序列发生器的输出端，所述相位补偿器在所述跳相序列的控制下对所述待解调信号中每个码片的波形进行相应的移相后由输出端输出解调信号。
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