频率源的相位噪声特性分析

在现代化通信和雷达的设备中,微波频率源作为核心部件,其性能好坏,直接影响设备特性,尤其是影响接收机的灵敏度和选择性等方面的技术指标。微波频率源的关键性能是其频谱特性,相位噪声是用来描述频率源的频谱特性重要指标,本文分析了相位噪声产生原因,给出几种典型微波频率源的相位噪声控制措施。     

光纤传输对接收机(雷达)相位噪声的影响及其在MTI性能测试中的应用

测得光纤传输对雷达本振激励源相位噪声的影响,并应用该传输设备对雷达接收系统的MTI性能进行测试,研究了光纤传输对雷达相位噪声及MTI性能测试的影响,说明提高光纤传输设备及雷达接收系统性能应进行的工作.     

直接式频率合成器相位噪声限制因素

频率合成器被称为雷达电子系统的"心脏",其相位噪声对设备和系统的性能影响很大,随着现代雷达技术的不断发展,对频率合成器的低相位噪声提出了较高的要求。文中简单介绍了频率合成器相位噪声的基本概念,基于频率合成器的基本实现方法,阐述了直接式频率合成器相位噪声的限制因素。并通过实践论证了这些限制因素对相位噪声的影响程度,以及介绍了未来频率合成器的发展方向,对低相位噪声频率合成器的工程设计和生产调试具有一定的指导意义。     

随机相位编码抑制步进频率探地雷达RFI的研究

步进频率探地雷达应用中,射频干扰严重影响合成孔径成像效果和目标检测性能。该文使用随机相位编码技术在不影响目标回波的情况下,可将所有射频干扰变为零均值随机信号,进而用经典的均值滤波方法进行干扰抑制。分析表明使用随机相位编码技术使步进频率探地雷达具有噪声雷达的射频干扰抑制能力,同时保留了步进频率良好的主副瓣比性能和利用FFT进行快速信号处理的优点。蒙特卡洛仿真结果验证了本文分析的正确性和随机相位编码对步进频率探地雷达射频干扰抑制的有效性。     

相位编码雷达干扰技术研究

由于相位编码雷达采用了相关处理技术,使得传统的干扰样式很难达到理想的干扰效果。为了有效干扰此种雷达,首先分析相位编码雷达信号的特点,然后通过理论分析和仿真验证的方式研究射频噪声干扰、部分复制干扰、移频干扰和基于DDS的相位编码干扰。仿真分析结果表明,射频噪声干扰对相位编码雷达的干扰效果较差,另外三种干扰样式则可在低干信比条件下达到很好的干扰效果。     

雷达接收机信道对脉冲信号相位谱干扰模型的分析与处理

雷达的接收机信道作为带通滤波器,其内部混有噪声,因此,当用其传输放大脉冲信号时,对脉冲相位谱会产生影响,使脉冲前后沿发生变化。本文分析了雷达信道对脉冲相位谱的干扰模型及影响程度,为消除其影响提供了准确、可靠的理论依据,并提供了处理这类信号的数学模型。     

基于光电振荡器的低相噪光生微波技术及其应用北大核心CSCD

光电振荡器通过自振荡产生超低相位噪声微波信号,具有光、电两种输出,有望从源头突破现有雷达、电子战等射频系统性能瓶颈。文章介绍了光电振荡器的基本结构和理论模型,回顾了光电振荡器相位噪声、边模抑制比、工作频率、稳定度和小型化等关键性能提升的研究进展,并讨论了光电振荡器的功能拓展及光电振荡器在雷达等领域的应用。     

频率合成器的相位噪声分析

频率合成器被喻为雷达电子系统的"心脏",其相位噪声对设备和系统的性能影响很大.文中简单介绍了频率合成器相位噪声的基本概念.基于频率合成器的基本实现方法,分析了频率合成器中的相位噪声,通过实例说明了不同合成方式频率合成器的相位噪声.时频率合成器的低相噪声设计的工程实现有一定的指导意义.     

基于相位噪声的控制信道设备预测设计

随着社会经济快速增长,信息化时代已经降临,高数据信息传输融进社会的建设中,人们对通信网络技术的需求也越来越高,各种信息传输技术设备都需要具有较高的可靠性,才能满足社会对通信技术的需求。文章通过基于相位噪声的技术,对控制信道设备整机的寿命进行预测,提前检测出控制信道设备整机的状态,及时处理或维修保养寿命将至的相关控制信道设备,保障整个信息传输系统的正常运行,减少设备突然停机所带来的极大经济损失。利用相位噪声技术进行对控制信道设备工作阶段模式、待机阶段模式以及测试阶段模式的性能参数指标的测试检测,分析这些性能参数的变量规律,判断其作为控制信道设备整机寿命预测的可行性,为相位噪声在对控制信道设备整机检测寿命可行性提供理论依据。     

频率合成器的相位噪声分析

频率合成器广泛应用于现代各种电子设备中,甚至被人们喻为众多电子系统的"心脏"。其性能好坏直接影响通信设备的性能,尤其是影响接收机的灵敏度和选择性。对频率合成器相位噪声的概念进行了简单的阐述。从锁相环的分析模型出发,介绍相位噪声的特性,分析了影响相位噪声的各种主要因素,并提出了提高频率合成器相位噪声性能的一些基本方法。通过实例介绍了环路滤波器参数的选择与计算。     

Joint compensation of IQ imbalance and phase noise in OFDM wireless systems

Physical impairments like IQ imbalance and phase noise can cause significant degradation in the performance of wireless communication systems. In this paper, the joint effects of IQ imbalance and phase noise on OFDM systems are analyzed, and a compensation scheme is proposed to improve the system performance in the presence of IQ imbalance and phase noise. The scheme consists of a joint estimation of channel and impairment parameters and a joint data symbol estimation algorithm. It is shown both by theory and computer simulations that the proposed scheme can effectively improve the signal-to-noise ratio at the receiver. As a result, the sensitivity of OFDM receivers to the physical impairments can be significantly lowered, simplifying the RF and analog circuitry design in terms of implementation cost, power consumption, and silicon fabrication yield.     

Multi-channel energy detection under phase noise: analysis and mitigation

For the development of highly integrated, flexible and low-cost cognitive radio (CR) devices, simple transceiver architectures, like direct-conversion receiver, are expected to be deployed and provide viable radio frequency (RF) spectrum sensing solutions for practical implementation. Yet, this can be very challenging task especially if spectrum sensing and down-conversion are conducted over multiple RF channels simultaneously for improved efficiency in channel scans. Then, the so-called dirty RF problem that degrades link performance of traditional transmission systems starts to be influential from spectrum sensing perspective as well. The unavoidable RF impairments, e.g., oscillator phase noise in direct-conversion receiver, could generate crosstalk between multiple channels that are down-converted simultaneously, and thus considerably limit the spectrum sensing capabilities. Most of the existing spectrum sensing studies in literature assume an ideal RF receiver and have not considered such practical RF hardware problem. In this article, we study the impact of oscillator phase noise on energy detection (ED) based spectrum sensing in multi-channel direct-conversion receiver scenario. With complex Gaussian primary user (PU) signal models, we first derive the detection and false alarm probabilities in closed-form expression. The analytical results, verified through extensive simulations, show that the wideband multi-channel sensing receiver is very sensitive to the neighboring channel crosstalk induced by oscillator phase noise. More specifically, it is shown that the false alarm probability of multi-channel energy detection increases significantly, compared to the ideal RF receiver case. The exact performance degradation depends on the power of neighboring channels as well as statistical characteristics of the phase noise in the deployed receiver. In order to prevent such performance degradation in spectrum identification, an enhanced energy detection technique is proposed. The proposed technique calculates the leakage power from neighboring channels for each channel and improves the sample energy statistics by subtracting this leakage power from the raw values. An analytical expression is derived for the leakage power which is shown to be a function of power spectral levels of neighboring channels and 3-dB bandwidth of phase noise process. Practical schemes for estimating these two quantities are discussed. Extensive computer simulations show that the proposed enhanced detection yields false alarm rates that are very close to those of an ideal RF receiver and hence clearly outperforms classical energy detection.     

New Phase Adjustment and Channel Estimation Methods for RF Combining Applicable in Mobile Terminals

Antenna diversity is able toalleviate multipath fading in a wireless communications system.Traditionally, multiple down-conversion chains have to be used inorder to implement antenna receive diversity, making it difficultfor implementation in mobile terminals, where the physical size,power consumption and implementation cost are three major limitingfactors. RF combining, which combines the received signals at RFlevel, is well applicable for mobile terminals as it requires onlyone down-conversion chain. This paper investigates RF combiningtechniques for improving downlink performance by applying atwo-element array at the mobile terminal. A new phase adjustmentalgorithm is suggested in order to combine the RF signals whileminimizing noise effect. Also, a new channel estimation methodbased on the suggested phase adjustment algorithm is proposed, andfurther applied to systems with transmit diversity. Computersimulations have shown that with the new channel estimation methodtogether with the new phase adjustment algorithm, the RF combiningtechniques can improve the BER performance considerably,especially for fast fading environment.     

一种P波段大功率T/R组件的设计

T／R组件是相控阵雷达有源分布阵列天线的核心部件,其性能直接影响雷达整机的指标。介绍了一种P波段大功率T／R组件的工作原理、设计方法和检测技术,并根据设计方法加工了实物样件,该T／R组件采用相控阵体制结构来实现：发射通道主要由移相器、衰减器和高功率放大器组成;接收通道主要由低噪声放大器、移相器和衰减器组成。在2dBm输入功率的情况下实现了200W输出功率,效率高达35％,在采取幅相一致设计措施后,该功放组件在100dB的动态范围内实现了相位误差在±3°以内。     

毫米波雷达前端芯片关键技术探讨

毫米波雷达的距离分辨率和最大可工作距离通常受雷达射频信号带宽和发射功率的限制,具有宽工作带宽、高输出功率、高灵敏度、高精度相位控制的毫米波雷达芯片是实现高性能毫米波雷达系统的关键.毫米波雷达芯片的设计难点主要集中在阻抗匹配、噪声降低、功率提升、相位控制等方面.因此,该文针对毫米波雷达前端芯片设计难点的关键解决技术进行探...     

雷达信号分选性能评价指标分析

提出了基于PRI的雷达信号分选性能评价指标定义,并根据基于PRI分选原理建立了性能指标模型,仿真了射频目标特征变化对基于PRI的雷达信号分选性能的影响。通过仿真分析,可以看出在理想的分选条件下,当随机噪声方差一定时,随着不同类信号的PRI差值增大,正确分选率随之增大,误分选率随之降低。漏分选率与随机噪声的方差有关,且随机噪声方差越大,漏分选率越小。     

Analysis and optimization of the impact of channel resistance on CMOS LNA noise performance

The intrinsic channel resistance, which is caused by the finite charging time of the carriers in the inversion layer, has remarkable impact on RF CMOS circuits, especially low noise amplifier (LNA), the first block of receiver. The impact of channel resistance on the noise performance of LNA is thoroughly studied and analyzed in this paper, and then new formulae are proposed systematically. Moreover, revised noise figure optimization technique is presented. All of this work will be very instructive for the design of high performance LNA.     

基于电源调制及有源滤波匹配的双向放大器芯片设计

射频双向放大器作为雷达接收通道的前端模块芯片,其性能的优劣直接影响通道的性能。传统的双向放大器芯片往往是基于射频开关的拓扑结构设计的,在噪声性能和反向隔离度方面都有所不足。文中设计基于电源调制的双向放大器芯片,具有全新的电路拓扑结构,射频信号不通过射频开关而直接进入低噪声放大器,可以优化芯片的噪声性能;同时,截止的器件可以提高芯片的反向隔离度。设计中如何提高低噪声放大器的增益和噪声性能,以及如何利用有源滤波匹配技术实现射频输入输出端口的合并和匹配是两大难点和创新点。文中基于L 波段的双向放大器设计及流片的测试结果显示,芯片有良好的性能,充分验证了理论分析的正确性。     

Impact of intrinsic channel resistance on noise performance of CMOSLNA

Channel resistance cannot be neglected for CMOS circuits that operate at radio frequency (RF), especially for a low noise amplifier (LNA), which is a very important block in CMOS RF transceivers. The impact of channel resistance on the noise performance of an LNA is thoroughly studied and analyzed and new formulas are proposed systematically in this work. Furthermore, a revised noise figure optimization technique is discussed. Simulation results are also proposed. All of this work will be very instructive for the design of high-performance LNA