CMOS Quadrature Modulator and Up-Conversion Mixer for 802.11a Wireless LAN Systems

A quadrature modulator and an up-conversion mixer for an 802. lla wireless LAN system are designed and fabricated in 0.18μm gate length standard CMOS technology. A current feedback loop with a transconductor is used to improve the linearity of the quadrature modulator;An LC resonant tank is used as the load of the upconversion mixer to improve its gain and increase the voltage swing. The measurement results show that the input P1dB achieves -3.6dBm, the transducer power gain of the circuit is -3.6dB,and the current consumes about 45.8mA with a 1.8V power supply.

Broadband tunable optical amplification based on modulation instability characteristic of high-birefringence photonic crystal fibers

A novel high-birefringence photonic crystal fiber （HB-PCF） with two zero-dispersion wavelengths （ZDWs） is designed, and an extraordinarily high modal birefringence of 1.56×10-2 is obtained at pump wavelength λp=1850nm. With the designed HB-PCF, the effect of the pump parameters on the modulation instability （MI） in the anomalous dispersion region close to the second ZDWs of the HB-PCF is comprehensively studied in this work. A broadband and tunable optical amplification is achieved by controlling the pump power and the pump wavelength based on the combined operation of Raman effect and cross phase modulation. By optimizing the pump parameters, the amplification bandwidth along the fiber slow axis reaches 152 nm for the pump power Pp=280W and the pump wavelength λp=1675nm, while the gain bandwidth along the fiber fast axis is 165 nm for the pump power Pp=600W and the pump wavelength λp=1818nm.

High-gain and low-distortion Brillouin amplification based on pump multi-frequency intensity modulation

Using a pump with a multi-line spectrum to broaden the Brillouin gain bandwidth is an effective way to achieve lowdistortion amplification with high gain. Here, we theoretically and experimentally investigate the generation of a broadband Brillouin gain spectrum based on multi-frequency intensity modulation in an optical fiber. The arbitrary bandwidth of the Brillouin gain spectrum of stimulated Brillouin scattering(SBS) can be obtained as expected. In our experiment, a broadband Brillouin gain spectrum with a bandwidth of about 200 MHz is demonstrated. We also achieve a low-distortion amplification of a weak signal, whose maximum magnification is 65 d B for a-68-dBm input power signal.

Transmission Performance of the Optical Millimeter-wave Up-conversion Link Using a Phase Modulator

Numerically analyzed is the transmission performance of the optical millimeter （mm）-wave generated by frequency up-conversion via a phase modulator along the dispersive fiber. 60 GHz ram-wave subcarrier（SC） signals can be obtained after fiber transmission, simultaneously, the phase-modulated signals can be converted to the intensity-modulated ones. The numerical results show that the optical ram-wave at fading loops has better performance, and the eye diagram still keeps open when optical mm-wave signal is transmitted over 98 km.

Modulational instability of the coupled waves between fast magnetosonic wave and slow Alfvén wave in the laser–plasma interaction

By performing modulational instability analysis of the the nonlinear coupled dimensionless equations between a fast magnetosonic wave(FMSW)propagating obliquely with the magneticfield and a low-frequency slow Alfvén wave(SAW),we obtain the dispersion relation of the perturbation wave.The growth rate of the perturbation wave is obtained.It is found that the growth rate increases as background magnetic field increases,which is in agreement with that reported by Tiwary et al(2016 Phys.Plasmas 23122307).A critical perturbation wave number is found.When the perturbation wave number is greater than or equal to the critical value,the growth rate is positive and it increases as the perturbation wave number increases,while the wave is stable.The maximum growth rate is reached when the frequency of the FMSW is half of the ion cyclotron frequency.The minimum growth rate is reached when the propagation direction of the perturbation wave is the same as that of the FMSW.

Two-frequency amplification in a semiconductor tapered amplifier for cold atom experiments

Simultaneous two-frequency amplification is highly desirable in cold atom experiments. The nonlinear response would appear in the two-frequency amplification with a semiconductor tapered amplifier（TA） and has a direct influence on the experimental result. We investigated in detail the effects of frequency difference, total power, and power ratio of two seeding lasers on the output components based on a simplified theoretical model. The simulation results showed that the multiple sideband generation in the amplifier due to self-phase and amplitude modulation could be suppressed and the TA tended to linearly amplify the power ratio between two-frequency components, when the two seeding lasers had a large frequency difference. This was verified experimentally in the output power ratio measurement via a calibrated Fabry-Perot interferometer method with a good linearity and an uncertainty of 1%. We also discussed the consequences of power ratio responses in the amplification in light of cold atom experiments, especially in the ac Stark shift related phase error of Raman-type atom interferometers（AIs）. It was shown that the fluctuation of intensity ratio of Raman beams may induce significant systematic errors for an AI gyroscope.

Optimization control of modulation-instability gain in photonic crystal fibres with two zero-dispersion wavelengths

We design three kinds of photonic crystal fibres （PCF） with two zero-dispersion wavelengths （ZDWs） using the improved full vector index method （FVIM） and finite-difference frequency domain （FDFD} techniques. Based on these designed fibres, the effect of fibre structure, pump power and wavelength on the modulation instability （MI） gain in the anomalous dispersion region close to the second ZDW of the PCFs is comprehensively analysed in this paper. The analytical results show that an optimal MI gain can be obtained when the optimal pump wavelength （1530 nm） is slightly shorter than the second ZDW （1538 nm） and the optimal pump power is 250 W. Importantly, the total MI gain bandwidth has been increased to 260 nm for the first time, so far as we know, for an optimally-designed fibre with ∧ = 1.4 nm and d/∧ = 0.676, and the gain profile became much smoother. The optimal pump wavelength relies on the second ZDW of the PCF whereas the optimal pump power depends on the corporate operation of the optimal fibre structure and optimal pump wavelength, which is important in designing the most appropriate PCF to attain higher broadband and gain amplification.

强信号全覆盖下反射式强度型传感器信号调制设计

反射式强度型传感器在强信号全覆盖环境下常常受到干扰和影响,导致传感器信号的质量下降甚至失真,给后续的信号处理和数据分析带来了困难。对此,提出强信号全覆盖下反射式强度型传感器信号调制方法。首先,判断强信号全覆盖环境下传感器信号的稀疏性,并根据环境的干扰因素建立信号的观测矩阵,通过优化算法计算出稀疏向量的估计值,使用稀疏向量的估计值对观测信号进行补偿,得到补偿后的信号;然后,应用正交锁相放大技术,将补偿后的信号与严格正交的两路参考信号相乘,提高信噪比,获得增强后的信号;最后,利用连续相位多支路调制方法,对增强后的传感器信号展开比特信息分离、二维信号映射与载波相位调制操作,完成信号调制。实验结果表明,所提方法可扩展性强、稳定性高且抗干扰能力强。

基于相位调制的非互易反射光放大动力学调控

基于光学非互易性的新型光子器件是信息处理的关键,由于信息在传递的过程中很容易减弱,因此如何放大光信号是该领域的研究热点之一。本文提出一种简单的方案实现了非互易光放大。该方案首先利用一个强耦合场和一个微波场控制一个弱探测场构成三能级V模型相干增益原子系统,使探测光信号在透明窗口处能够被放大;再通过控制耦合场强度随位置变化破坏极化率空间对称性,使得探测光从介质两侧入射的反射率不再互易,进而得到放大的非互易反射;最后,通过调制激光场之间相对相位来探究其非互易反射带放大的范围。数值结果显示,相对相位Φ=0,π和3π/2时,只有一个非互易频率域的反射带被放大;而当Φ=π/2时,出现两个频率域内放大的非互易反射带,放大范围为1.25~2.75倍。可见,该系统能够实现非互易反射光放大的动力学调控。

中波广播发射机的原理及应用

中波广播发射机作为广播传输的一种技术手段,对于广播行业的发展起着重要作用。深入研究中波广播发射机的原理和应用,并探讨其在广播行业中的重要性。首先,介绍中波广播发射机的基本原理,包括音频信号的调制与解调、射频信号的产生与放大、天线辐射等关键技术。其次,探讨中波广播发射机在广播行业的应用,包括广播覆盖范围的选择、信号质量的优化及干扰抑制等方面。最后,列举中波广播发射机在电台广播、天气广播、教育广播以及文化传播等特定场景的应用案例。

L波段全国产化2.5 kW级脉冲模块设计

随着国防和民用技术的迅速发展,高性能的L波段脉冲模块成为雷达和通信领域的关键组件。文章介绍了一个全国产化的2.5 kW级L波段脉冲模块的设计流程。该模块采用先进的射频放大技术和脉冲形成网络设计,结合本土材料和工艺技术的优势,实现模块的高性能和低成本生产。仿真和实验验证表明,设计的模块满足了所有预期的技术参数,包括功率水平、脉冲宽度和效率,通过了严格的质量控制和可靠性评估。

Intense,wideband optical waveform generation by self-balanced amplification of fiber electro-optical sideband modulation

We demonstrate a simple method to obtain accurate optical waveforms with a gigahertz-level programmable modulation bandwidth and a watt-level output power for wideband optical control of free atoms and molecules.Arbitrary amplitude and phase modulations are transferred from microwave to light with a low-power fiber electro-optical modulator.The sub-milliwatt optical sideband is co-amplified with the optical carrier in a power-balanced fashion through a tapered semiconductor amplifier(TSA).By automatically keeping TSA near saturation in a quasi-continuous manner,typical noise channels associated with pulsed high-gain amplifications are efficiently suppressed.As an example application,we demonstrate interleaved cooling and trapping of two rubidium isotopes with coherent nanosecond pulses.

钛宝石超短脉冲放大过程中的增益窄化效应

本文研究超短脉冲的放大过程中产生的一个很重要的非线性效应──脉冲频谱的增益窄化效应（Ｇａｉｎ Ｎａｒｒｏｗｉｎｇ）．分析了它的产生机理，同时指出了增益窄化效应在制约由于自相位调制效应引起的脉冲频谱展宽现象时所起的脉冲整形作用，得出了决定这种整形效果的种子脉冲参数和对放大器性能的要求．

啁啾光脉冲的自相位调制效应对压缩光脉冲的影响

在超强激光系统中,对比度和本底宽度是压缩光脉冲极为重要的指标。在啁啾脉冲放大系统的压缩阶段,在啁啾脉冲宽度为141 ps,啁啾系数为1 000,B积分值分别为0,1 和2 的情况下,模拟了自相位调制效应(SPM)对压缩脉冲的峰值光强、脉冲宽度和本底宽度的影响。结果表明:在B积分值为2 的条件下,若不补偿非线性色散,压缩脉冲的峰值强度降为无自相位调制效应时的65%左右,脉冲宽度约为种子脉冲宽度的2倍,本底宽度则增加到原来的3倍左右;在B积分值大于0.5 的情况下,本底宽度和B积分值近似成线性关系。

单通道信号处理的前端信号调理模块的设计

在机械故障的诊断中,振动信号是不可缺少的重要判断依据。由于振动信号极其微弱,并且由于所处环境等原因,极容易造成频率混叠而导致不能直接进行A/D转换,这就需要在A/D转换之前对信号进行放大和滤波等调理方法,使其满足A/D转换的要求。介绍了一种单通道振动信号处理的前端信号调理模块的设计方法,其中传感器恒流源供电采用LM348四运放集成芯片构成,信号放大电路选用了可编程增益放大器PGA204/205,滤波电路由单片集成滤波器芯片MAX274构成。通过实践检验本模块在工程中有很大的应用价值。

啁啾脉冲堆积及其放大特性

根据啁啾脉冲堆积的原理以及模型介绍了两路脉冲堆积时脉冲的时间与频谱特性,分析了堆积脉冲产生时间与频谱调制,以及交叠区产生非线性频率啁啾的原因。通过非线性薛定谔方程,分析了堆积脉冲的放大特性,介绍了啁啾参量对放大结果的影响以及放大后堆积脉冲的频率啁啾的变化。研究表明,在堆积脉冲的放大过程中自相位调制效应非常明显,严重影响了脉冲的频谱与频率啁啾。

基于DDS的多调制功能正弦信号发生器

为了研究一种基于直接数字频率合成技术(DDS)的正弦信号发生器,以89S52和现场可编程门阵列(FPGA)为控制核心,DDS专用芯片AD9851为正弦信号模块,并设计实现AM、FM及二进制键控(PSK、ASK)等多调制信号功能。结果表明:实现了频率范围1 Hz～30 MHz正弦信号的无失真输出;通过以AD811和推挽电路为基础的后级功放,正弦信号的输出幅度在50Ω负载上达到Vopp=20 V;多调制信号输出稳定。

小宽带堆积啁啾脉冲传输放大特性

采用啁啾脉冲堆积的方法可获得ns量级宽带整形激光脉冲,对堆积啁啾脉冲时间波形的影响因素及传输放大后脉冲波形与光谱形状的特性进行了研究。结果表明:在传输过程中脉冲的演化规律与窄带脉冲的演化规律基本一致,而且传输放大过程也不会改变脉冲的调制结构,但光谱形状在传输放大过程中发生了变化,初步认为是由非线性效应造成的;小宽带堆积啁啾脉冲具有与窄带脉冲基本一致的的增益水平。

光纤中基于交叉相位调制与喇曼放大的超短光脉冲串的产生

本文提出一种在单模光纤负群速色散区由连续波产生超短光脉冲串的新方法．即让波长位于光纤负色散区的连续波和波长位于光纤正色散区的泵浦脉冲串在光纤中共同传输，在光纤的零色散波位于连续波波长与泵浦脉冲波长中间附近的情况下，交叉相位调制与喇曼放大能使连续波演化成比泵浦脉冲窄得多的、无调啾、无脉座的超短光脉冲串，数值计算表明，泵浦脉冲愈强，由连续波产生的超短光脉冲宽度愈窄、峰值功率愈高、而且所需的光纤愈短．

脉冲调制器稳定性监控中的信号调理电路研制

上海软X自由电子激光实验装置(SX-FEL)对直线加速器微波功率调制器的脉冲幅度提出了0.01%的稳定度要求。本文介绍基于脉冲信号采样分析来反馈控制调制器的充电电压的控制策略,并着重介绍这种方案中的信号调理电路的研制。脉冲信号调理电路主要完成衰减、切割放大、滤波等功能。调理之后的信号可以送给高速ADC进行采集,也可以直接连接到示波器上观察脉冲信号平顶特征。实验结果表明该调理电路稳定性高,达到了预期目的。