基于声呐浮标的水声信号采集系统设计

声呐浮标水声信号采集系统是采集和传输水声数据的常用设备。该文针对水声信号动态范围大、频率范围宽、海洋噪声信号的频率特征差异大等特点,基于浮标平台设计了一款多通道、高一致性和宽动态范围的水声信号采集系统。该系统以STM32为主控核心,通过对水声信号进行预处理,实现了四通道固定增益80 dB、动态增益40 dB、频带范围为100 Hz～20 kHz的水声信号同步高速采集。该系统还设计了上位机,将所有通道水声数据通过显示屏进行显示,并根据实际情况对系统状态进行控制。实验测试结果表明,该水声信号采集系统满足设计要求,在声呐浮标信号采集领域具有极大的应用价值。     

一种单一增益下实现红外探测器大动态范围读出方法研究

目前红外探测器采用传统读出方法很难通过一次积分实现其本身的动态范围。为实现红外探测器的大动态范围不换档读出,引入脉冲频率调制（Pulse Frequency Modulation,PFM）结构,同时为保证弱信号时的注入效率,结合CTIA输入级,对红外探测器不换档大动态范围读出方法进行研究。提出一种CTIA输入级脉冲频率调制（PFM）读出方法,在系统级层面搭建实验系统并结合短波红外InGaAs单元探测器进行数字量化实验。详细分析了强信号时由系统结构延迟时间引起的转换线性度问题,并建立非理想条件下的数字量化转换模型。实验结果显示,提出的CTIA输入级PFM红外探测器读出方法动态范围达到97 dB, 为红外探测器不换档大动态范围读出提供了一种可行方案,并为数字化读出电路设计奠定理论基础。     

敌我识别S模式询问信号实时检测技术

为了在非合作条件下实时截获敌我识别S模式询问信号,分析了S模式询问信号特征,并提出敌我识别S模式询问信号实时检测技术。通过脉冲信号检测、时域参数测量和脉冲分选技术,实时检测S模式询问信号,获取采用差分相移键控(DPSK)编码的数据,并在现场可编程门阵列(FPGA)中进行了实现和验证,试验结果表明,该检测技术能够有效地检测并截获敌我识别S模式询问信号。     

大口径磁光隔离器隔离度单次测量技术

搭建了全光纤化的大口径磁光隔离器隔离度单次测量系统,体积小且调节灵活方便,在大口径隔离器的在线测量方面具有独特优势。利用光纤器件在光束传输和耦合方面的优势以及磁光隔离器的工作特点,采用透过率相对测量法和静动态对比法实现了隔离度的单次测量。实验可测量动态范围达到33dB以上,且通过调整光纤耦合器分光比可使测量动态范围进一步提高到50dB以上。该方法有效消除了输入信号脉冲功率及偏振态抖动等因素对测量精度的影响,在输入信号脉冲能量和偏振态随机抖动的情况下,仍然可实现抖动波峰波谷(PV)值为2.2%的测量精度。     

超短激光脉冲对比度的三阶相关测量

在超强超短激光脉冲与物质相互作用过程中,良好的激光脉冲对比度是一个非常重要的参数指标.为了扩大对超短激光脉冲对比度的测量范围,准确地测量超短激光脉冲的对比度,利用非线性晶体对激光脉冲强度变化十分敏感的特性,研究了超短激光脉冲三阶相关信号的产生过程,并在此基础上,研制了一台三阶相关仪,对一台飞秒激光振荡器进行了脉冲对比度的测量研究.测量结果表明,通过在测量光路中加入聚焦透镜进行聚焦准直,可以有效提高激光脉冲的倍频效率,从而大幅提高该三阶相关仪的可测动态范围.该测量系统目前可实现的可测动态范围达到约108.     

基于AT89S52的脉冲参数测试仪

设计的脉冲参数测试仪可对脉冲的脉冲宽度、周期、频率、占空比及峰值进行测量与显示,读数方便。利用AT89S52对经过LM393整形后的输入信号直接进行脉冲宽度、周期、频率以及占空比的测量,并由软件实现;通过LM398实现了峰值保持,并用LF331将该峰值转换成相应频率,以便于AT89S52完成最终测量并显示。该仪器性能良好、电路实现简单、测试结果准确。     

短脉冲激光的二阶自相关

为了实现短脉冲激光的高动态范围信噪比(SNR)测量,满足快点火对激光驱动器的要求,开展了信噪比测量的前期研究.结合非线性晶体分析了超短脉冲的二阶自相关信号的产生过程,结果表明自相关曲线的信噪比等于原始脉冲的信噪比.同时讨论了非共线二阶自相关中,两束输入信号光的夹角变化对输出信号光强的影响.在此基础上,建立了一台二阶自相关仪以验证超短脉冲信噪比测量系统的工作性能,其信噪比测量的动态范围达到了约108.     

小型无线电引信侦察信号处理机

小型无线电引信侦察信号处理机作为无线电引信侦察的信号分选、识别、参数测量设备，具有体积小、重量轻、耗电省、能在恶劣自然条件下工作的特点，该机使用了每秒一千万次运算速度的ＴＭＳ３２０Ｃ２５高速信号处理计算机和自适应的数字式自动增益控制技术，能对５０ｄＢ动态范围内的信号进行实时自动侦收，既对连续波信号进行参数测量，信号识别，又对脉冲信号进行信号分选和识别。实现了对连续波引信、调频引信和脉冲引信信号的实     

用相位噪声和谐波分析法测量激光脉冲的时基抖动

对测量光脉冲时基抖动的相位噪声测量技术和谐波频谱分析方法进行了实验比较。实验表明，谐波频谱技术由于受频谱仪内部噪声和测量带宽的限制不适合测量低抖动高重复频率的光脉冲。相位噪声测量技术不需要带宽频谱仪，测量动态范围大，可从真实信号中区分出虚假信号，其测量精度高于10fs。同时指出，用相位噪声技术测量时基抖动时，以低频噪声区间来替代整个重复频率的积分区间是不严谨的。     

时间积分型高灵敏度声光接收技术

声光接收机通过布拉格衍射实现并行的窄带信道,能够实现对输入的微波信号测量功能。利用可变时域积分的方法对信号变换的功率谱进行累积,能够解决对信号高灵敏度截获的困难。论述了时间积分型声光信道化接收技术的工作原理,分析了测频精度、灵敏度等主要性能,并通过搭建的原理试验验对功率为-100d Bm的脉冲信号进行参数测量,证明了该方法的有效性。     

一种低噪声微弱信号调理电路设计

水下主动声纳探测系统是通过发射换能器发射主动声信号,水听器检测回波信号完成目标探测和方位估计等任务。由于水听器输出信号微弱,易被复杂的海洋环境噪声干扰不能直接用于后续采集电路,要求信号调理电路具有高增益并且自噪声远低于水听器输出信号。而且主动声呐工作在近距离时,水听器接收到的混响信号远高于目标的回波信号,水听器接收到的信号动态范围大。本文提出的一种低噪声微弱信号调理电路,是一种低噪声、高增益、大动态范围、高一致性的信号调理电路。     

激光偏振技术压缩激光雷达信号动态范围

为了解决激光雷达信号的大动态范围引起远距离弱信号的失真问题,采用通过压缩信号的动态范围的方法,设计了一个利用电压调制系统透过率进而压缩激光雷达信号动态范围的方案。计算表明,系统最小透过率为4.05×10-5,可以压缩信号的动态范围达到4个数量级。利用激光雷达后向散射信号的两个方向偏振光,避免了时控光衰减器只透过一个方向偏振光的弊端。研究结果为压缩激光雷达信号动态范围提供了有价值的新方法。     

Pulse compression by means of linear-period modulation

In applications where large time-bandwidth products and high target speeds combine, linear FM pulse-compression systems used in radar or sonar suffer considerable losses in performance. This paper deals with the problem of wide-band signal optimizintion for the purpose of minimizing signal degradation resulting from Doppler distortion effects. The equation for the instantaneous frequency of a Doppler-transformed signal is derived. The optimum frequency-modulation law is then shown to be the linear period modulation (it can be with equal rights called hyperbolic frequency modulation or logarithmic phase modulation). It is interesting to note that some kinds of bats use this type of signal in their "sonar." Exact and approximate expressions for the spectrum of a linear-period-modulated rectangular pulse are given, and the shape of the compressed output pulse is considered. Signal degradation due to Doppler distortion is shown to be negligible in the case of linear-period-modulation pulses. The influence of pulse envelope on the compressed signal waveform is discussed, and envelope-optimization examples are presented. A possibility for active generation of the optimum signal is mentioned. Significant properties of linear FM and linear-period-modulation pulse compression systems are compared.     

Walk error minimisation by resonance-based laser pulse timing detection

A method for timing point detection in a laser pulse is presented. A pulse shaping circuit is placed at the input of the receiver to achieve a large dynamic range without gain control and timing errors caused by signal clipping. A parallel resonant circuit is proposed as the shaping circuit.     

A Discrete‐Amplitude Pulse Width Modulation for a High‐Efficiency Linear Power Amplifier

A new discrete‐amplitude pulse width modulation (DAPWM) scheme for a high‐efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low‐frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching‐mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.     

一种水下有源噪声抵消系统的设计

潜艇的自噪声是影响潜艇被动声纳系统性能的重要因素。对接收信号中的潜艇自噪声进行有源抵消,从而可提高被动声纳的作用距离。该文设计了一个针对舰艇艏端被动声纳平台的本艇自噪声有源抵消系统,并设计了其试验系统方案。采用直接-并联型结构的多通道有源陷波器和滤波最小均方误差算法(FXLMS)自适应滤波算法,有效地抑制了潜艇自噪声中的线谱分量,提高了接收端的输入信噪比,提高了被动声纳作用距离。     

雷达的杂波特性及杂波抑制技术

针对脉冲多普勒体制雷达,从杂波特性入手,就雷达的动目标检测和杂波抑制技术进行了讨论,并举例说明有关指标的计算。经过工程实践验证,采用大动态范围的线性接收机和FFT数字信号处理技术相结合的方案,能获得更高的改善因子和杂波抑制能力。     

短脉冲在色散平坦光纤中传输前后波形、相位和啁啾测量的实验研究

二次谐波频率分辨光学门(SHG-FROG)是能够准确测量短脉冲多项特性参量的新技术。利用二次谐波频率分辨光学门脉冲分析仪对在色散平坦光纤中传输前后的短脉冲进行了测量,得到了待测光脉冲的频率分辨光学门(FROG)图、自相关曲线、自相关频谱曲线、波形和相位曲线以及脉宽、谱宽、啁啾等反映短脉冲特性的信息,对实验结果进行了分析,并与高斯脉冲在单模光纤中的线性传输理论进行了比较。结果表明,激光器输出的短脉冲是具有负线性啁啾的近变换极限高斯脉冲,经过12.7 km色散平坦光纤传输后仍然为具有负线性啁啾的高斯脉冲,其谱宽在传输过程中基本保持不变,脉宽展宽了3.1倍,啁啾增大了4倍。实验测量结果和理论预期一致。     

Tracking-based baseline restoration circuit for acquisition of bio signals

Most bio signal waveforms have a baseline that may drift over a large range compared to the excursion of the signal component. A circuit is developed, based on the amplitude tracking technique, for fast estimation and removal of the baseline drift, for effective use of the input dynamic range of the signal acquisition setup     

Generation of an ultra-wideband triplet signal based on semiconductor optical amplifier

We propose a novel ultra-wideband (UWB) triplet signal source based on the cross-gain modulation (XGM) in semiconductor optical amplifier (SOA). In the proposed scheme, only an optical source and two SOAs are needed, so the all-optical structure is compact. A triplet optical pulse with center frequency of 6.25 GHz and fractional bandwidth of 83% is obtained by the scheme. The extinction ratio can be improved by the counter-propagating scheme. The triplet pulse signal with only one wavelength can be easily controlled, and can aviod the dispersion effect. The output triplet pulse signal is insensitive to the light wavelength shifts, its available wavelength range is wide, the dynamic range of the input power is more than 6 dBm, and the bias current of the SOAs is exhibited.