EMI认证测量中FFT接收机测量时间的注意事项

引言 2010年6月,CISPR 16-1-1第3版第1修正案[1]规定,基于FFT的测量接收机(下简称FFT接收机)可用于电磁干扰认证测量,希望将扫描时间降低几个数量级,且不会降低测量准确度.FFT接收机在测量期间,通过在多个频率上并行计算,测量比分辨率带宽大得多的多个频谱段,如图1所示.与此相反,传统EMI接收机用给定的测量时间,在分辨率带宽内测量信号,因此对于整个频率范围需要较长的扫描时间.     

一种外场VHF频段宽带RCS测量接收机设计

基于外场VHF频段目标特性测量需求,设计一种外场VHF频段宽带RCS测量接收机。该接收机采用预选滤波法提高了接收前端选择性,抑制射频干扰信号,同时设计频率关系,实现宽带信号接收,在后续信号处理中采用相参积累法进一步抑制射频干扰及接收机噪声,提高接收机灵敏度,实现大动态范围信号接收。通过外场试验验证,实测结果与理论仿真结果吻合较好,验证了该设计方案的可行性。     

K波段辐射计的超宽带多通道接收机设计与实现

K波段微波高光谱辐射计应用于大气探测方向, 能够在高湿度条件下改善大气温湿度廓线精度。为解决传统辐射计接收机未考虑在微波高光谱条件下频谱测量时间和系统复杂度增加的问题, 设计与实现了一种用于K波段微波高光谱辐射计的超宽带多通道线性接收机。通过结合传统微波辐射计接收机的数项优点, 改进的接收机结构拥有良好的宽带谱特性、高线性度和短频谱测量时间。在18~26 GHz频率范围内, 接收机的实测频率增益为77~80 dB、噪声系数为2.1~3.2 dB、线性度为0.999~0.9999和频谱测量时间平均为5.8 ms。实测结果表明, 设计的高频谱分辨率接收机适合K波段微波高光谱辐射计在大气遥感和快速天气变化观测中应用。     

TD-LTE基站接收机中镜像抑制滤波器的研究和设计

在TD-LTE基站中,接收机对射频信号中镜像频率的抑制十分重要,在很大程度上是衡量基站接收机性能优越性的重要指标。为了消除TD-LTE基站接收机中的镜像频率,需要在混频器前设计一个抗镜像滤波器。该文提出一种超高频(3GHz~30GHz)LC型镜像抑制滤波器,通过其独特的结构设计来满足TD-LTE基站接收机镜像频率的抑制要求,具有良好的一致性。可以推广到多种通信制式的测试设备、基站等产品中,具有广泛的应用前景。     

扫频接收机中宽带频响自动补偿技术

在电子测量领域,扫频接收机的频率覆盖范围越来越宽,为了保证整机宽频率范围内测量信号幅度的准确性,需要对频率响应进行补偿。该文介绍了一种扫频接收机宽带频率响应的自动补偿技术,基于分段拟合的思想在FPGA内实现了扫描过程中补偿数据的自动调用、累加和补偿数据输出。实际应用表明,该文给出的设计方法合理有效,具有很高的实用价值。     

微波取样锁相频率合成器的设计

阐述了微波接收机中的相位噪声概念及本振源频率不稳定度的实际测量参数,并简要介绍了频率合成技术和锁相环路工作原理.针对卫星电视接收机中微波高稳定本振源的要求,重点研究了取样锁相频率合成器电路的优化设计及性能.     

多通道频率检测技术的FPGA实现

多通道频率检测是当前数字接收机的一种常用的频率测量方案,该方法可以较好地解决频率截获概率与频率分辨力的矛盾,并在复杂的电磁环境中具有处理多个同时到达信号的能力。文中给出了基于FPGA来实现多信道频率测量的具体方案。该方案能够充分发挥FP-GA硬件资源丰富的特点,并且易于实现并行处理,可大幅度提高系统的处理速度。     

微波宽带衰减自动检定和校准系统

衰减量是微波宽带电子系统或其零部件（同轴及波导）性能的一项重要参数。该文介绍一种基于HP8902A测量接收机、毫米波混频器及计算机的衰减自动测量和校准系统，该系统可以实现频率达到40GHz衰减量快速、准确的测量。文中对硬件配置与软件设计作了详细介绍，对误差的分析作了较详细的说明。     

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。     

群时延相位线性回归测量方法及应用

为解决传统群时延测量方法在工程实现中存在的频率分辨率与测量精度不可得兼的矛盾,提出了一种基于相位线性回归分析的群时延测量方法。在GPS授时接收机电缆传输特性测试中的实验结果表明,新测量方法与GPS授时接收机测得的信号传输时延之间具有好的对应关系。     

基于Simulink的单比特数字接收机设计

瞬时测频接收机拥有大工作带宽以及高截获概率,是电子战系统的一个重要组成部分,然而它无法对同时到达的多个信号进行测频。单比特接收机是解决这个问题的一种方法,由于它采用了很低的ADC采样位数,以及直接射频采样能力和独特的测频算法,使它具有大带宽、实时测量双音信号频率信息的优异性能。相比于典型的数字接收机,自身结构也得到了极大的简化。提出了一种单比特接收机硬件设计架构,并基于Simulink工具搭建了模型,分析了这种设计的性能。该模型具有高度的灵活性,对于单比特接收机的设计与系统实现具有一定的指导意义。     

频标偏移对GNSS接收机捕获性能的影响分析

任何GNSS接收机对频标的性能都有一定的要求,即允许频标只能在某一范围内偏移,超出这个范围,接收机就不能正常工作。本文从频标的特性分析入手,描述了频标产生偏移的原因,同时结合接收机的捕获原理,阐述了频标偏移对接收机捕获性能的影响,对接收机设计具有一定的参考价值。     

一种适用于突发相干光通信的均衡和频偏估计的联合方法

为了适应光突发接收机的快速信道均衡和频偏估计的要求,提出一种时域均衡联合频偏估计的方法。频偏估计的叠加结果作为反馈用于电信道均衡器误差信号的计算,同时用于均衡器估计值的频偏补偿。通过仿真验证了时域均衡联合频偏估计可以提高系统性能,并对影响光突发接收机的参数设置进行了研究;仿真研究了自适应均衡联合频偏估计时光突发接收机适用的稳态频偏和光纤传输距离范围,当系统中存在1GHz的频偏时系统仍然能够传输180km以上。研究结果表明,本文提出的时域均衡联合频偏估计的算法,在当光突发接收机中存在频偏暂态效应时仍然能够有效完成信道均衡和频偏估计与补偿。     

A channelized digital ultrawideband receiver

A channelized digital ultrawideband (UWB) receiver that efficiently samples the UWB signal at a fraction of the chip frequency is proposed. The received signal is channelized in the frequency domain by employing a bank of mixers and low-pass filters. After sampling at a much reduced frequency, digital synthesis filters optimally estimate the transmitted signals. The signal-to-noise ratio (SNR) of the proposed receiver has been solved and compared against an ideal conventional receiver, which is defined as a receiver that samples at the signal Nyquist rate. When finite resolution analog-to-digital converters (ADC) are employed in the presence of a large narrowband interferer, the proposed receiver significantly outperforms the ideal conventional receiver. For example, the SNR of the proposed receiver is as much as 20 dB higher than the ideal conventional receiver when a 4-bit ADC is used in the presence of a 50 dB (relative to the noise floor) brickwall narrowband interferer with a bandwidth of 15% of the chip frequency.     

Performance Study of an FFH/BFSK Self-Normalizing Receiver with Multitone Jamming's Frequency Offsets

This study investigates how frequency offsets of multitone jamming affect the fast frequency-hopped binary frequency shift keying (FFH/BFSK)self-normalizing (SNZ) receiver under additive white Gaussian noise (AWGN). The average bit-error-rate (BER) expressions of the FFH/BFSK SNZ receiver and the average BER expressions of an FFH/BFSK spread-spectrum (SS) communication system with frequency offsets of multitone jamming for the sake of understanding the simulation results better. Simulation results show that BER performance of the FFH/BFSK SNZ receiver with diversity under the worst casemultitone jamming (MTJ) and AWGN suffers from multitone jamming's frequency offsets when the jamming power is moderate, which is validated by several simulations with different frequency offsets configured in multitone jamming. Therefore, an FFH/BFSK SNZ receiver under multitone jamming can be combated with the help of frequency offsets of multitone jamming.     

Receiver window designs for radio frequency interference suppression in DMT systems

Windowing is often applied at the DMT (discrete multitone) receiver to suppress radio frequency interference (RFI). The spectral roll-off of the window determines how neighbouring tones are affected by RFI. However, the roll-off of the window is not of equal importance in all frequency range. In particular, the rolloff in high frequency will be inconsequential when the side lobes are so small that RFI is not the dominating noise. The window is designed here to minimise total interference. The frequency response of the proposed window achieves a good trade-off in spectral roll-off between high and low frequencies. As a result, fewer tones will be dominated by RFI than in the cases of commonly used Hanning and Blackman windows, in which the stopband in high frequency are often over designed. We have considered the case for informed receiver (RFI information available to the receiver) and uninformed receiver (RFI information unavailable to the receiver). In either case, the proposed window is channel-independent and can be obtained in a closed form.     

基于数字信道化的正弦信号快速测频方法

数字信道化接收机已经在电子战等领域得到了广泛的应用,正弦信号的快速准确测频在通信侦察中有重要意义。首先分析了基于DFT多相滤波器的信道化接收机高效结构,然后讨论了一种简化的快速测频方法,提出了将信道化处理的思想引入到快速测频问题中的解决方案。理论分析和仿真结果表明,该方案集合了信道化接收机和原始快速测频算法的优点,能够简化计算,提高原始测频算法的测频精度,适用于对测频速度要求较高但对精度要求不高的场合。     

Broadband multicarrier communication receiver based on analog to digital conversion in the frequency domain

This paper introduces a multicarrier communication receiver for broadband applications based on analog to digital conversion (ADC) of the received signal in the frequency domain. The samples of the spectrum of the received signal are used in the digital receiver to estimate the transmitted symbols through a matched filter operation in the discrete frequency domain. The proposed receiver is aimed at the reception of high information rates in a multicarrier signal with very large bandwidth. Thus, the receiver architecture provides a solution to some of the challenging problems found in the implementation of conventional wideband multicarrier receivers based on time-domain ADC, since It efficiently parallelizes the A/D conversion reducing the sampling speed requirements. We show that the sampling rate requirements are relaxed as the number of frequency samples is increased, which introduces a trade-off between complexity and sampling rate. The new receiver possesses additional advantages, including scalability with increasing frequency samples, the possibility of optimally allocating the available number of bits for the ATD conversion across the frequency domain samples which potentially reduces the distortion introduced by the high-speed ADC, narrowband interference suppression that can be directly carried out in the frequency domain, and inherent robustness to frequency offset which makes it an attractive solution when compared with traditional multicarrier receivers. We also investigate how the proposed receiver responds to common multicarrier communication receiver problems such as phase noise and channel frequency selectivity.     

一种超宽带高速跳频信号实时非合作接收机

提出一种基于模数混合信道化宽带处理和实时流水处理技术的超宽带高速跳频信号实时非合作接收机结构,采用基于无盲区数字信道化、多通道数据融合的频率跳变时刻估计算法和针对差分相移键控(SDPSK)信号的实时解调方法,解决了超宽带高速跳频信号的实时解跳和解调难题。为进一步验证所提出结构和算法的有效性,设计并实现了一种针对2 GHz,20 000 Hop/s跳频信号的超宽带高速跳频实时非合作接收机。测试结果表明:该接收机能实现对超宽带高速跳频信号的实时解跳和解调。