光子型远程分布式微波信号接收码元速率估计

基于光子学技术,设计了一种针对远程分布式微波信号接收的码元速率估计方案。首先,远程终端将接收的微波信号经电光调制器对连续激光源进行载波抑制双边带调制,生成携带微波信号的两个光边带信号;此光信号经光纤链路传输至中心站在光域滤除其中一个边带;其次,进行光电探测,通过分析电频谱的谐波实现微波信号码元速率估计。针对此方案,搭建仿真及实验系统装置：仿真成功地从60 GHz微波信号中提取出0.8 GBaud和6 GBaud的二进制伪随机码(PRBS)信号码元速率、从25 GHz微波信号中提取出3 GBaud的PRBS码元速率;实验成功地从25 GHz的微波信号中提取出3 GBaud和5 GBaud的PRBS码元速率。     

双边带载波抑制调制载波信号馈送系统的研究

研究了基于双边带载波抑制调制的高频载波信号馈送系统的传输性能.分析了双边带载波抑制调制的原理,系统输出倍频信号的功率以及载波信号经过馈送系统后相位噪音发生劣化的原因.通过实验测量输入载波信号和输出倍频信号的功率和相位噪音验证了理论分析的正确性.结果表明,系统输出倍频信号的功率为-5.7dBm,载波信号经过馈送系统后近端相位噪音劣化了6dB,远端相位噪音劣化了21dB.     

双边带载波抑制调制载波信号馈送系统的研究

研究了基于双边带载波抑制调制的高频载波信号馈送系统的传输性能.分析了双边带载波抑制调制的原理,系统输出倍频信号的功率以及载波信号经过馈送系统后相位噪音发生劣化的原因.通过实验测量输入载波信号和输出倍频信号的功率和相位噪音验证了理论分析的正确性.结果表明,系统输出倍频信号的功率为-5.7 dBm,载波信号经过馈送系统后近端相位噪音劣化了6 dB,远端相位噪音劣化了21 dB.     

无光滤波六倍频微波信号产生的系统设计

基于两个级联偏振调制器,提出了一种高频谱纯度、稳定的六倍频微波信号产生方法。该方法通过适当调整偏振片的偏振方向、射频驱动信号电压和相位,实现无光滤波器条件下、任何波段六倍频微波信号的产生。利用Optisystem平台搭建的仿真系统,以S波段4 GHz信号为例,验证了该设计系统产生的六倍频信号质量,并分析了非理想射频驱动电压和相位对六倍频信号质量的影响,结果表明：该设计系统能产生最大光边带抑制比、射频无杂散抑制比分别为21.3,15.2 dB的六倍频微波信号;且非理想驱动电压和相位差的偏离应控制在理想值5%的范围之内。     

多速率STFT超宽带信号瞬时频率估计研究

提出多速率短时傅里叶变换(Multi Rate Short Time Fourier Transform,MR-STFT)瞬时频率估计算法,提高了超宽带信号瞬时频率估计精度。该方法将多速率信号处理算法与短时傅里叶变换(STFT)技术相结合,兼顾采样频率和被测频率,将宽频范围进行分段采样,对分段处理结果进行拟合,构成多速率STFT算法,实现超宽带信号瞬时频率的高精度测量。论文通过对仿真信号和实测信号进行处理,研究了方法的可行性和频率估计精度,结果表明MR-STFT算法较大提高了超宽带信号瞬时频率估计精度,尤其对低信噪比的超宽带信号效果显著。     

光子辅助矢量微波/毫米波产生的关键技术研究

光载无线技术(RoF)因其大带宽、高移动性和低传输损耗等特点,成为未来接入网极具前景的解决方案之一。同时,该技术与矢量调制格式结合可以有效提高系统容量。但是如何低成本地产生光矢量微波/毫米波一直是亟待解决的问题。从预编码和光子倍频技术出发,提出多种光子辅助微波/毫米波产生方案,这些方案从成本、器件可用性、系统复杂度、系统容量等角度对传统方案进行了改进,为将来的研究工作提供参考。     

基于级联MZ M倍频系数可调高频微波信号光 产生方法

理论分析了在不改变光滤波器的条件下,通过设置级联马赫曾德尔调制器的直流偏置点和调制指数,实现最小光边带抑制比和最小杂散抑制比分别为45.48dB和39.46dB,倍频系数为2k(k=1,2,…,6)的高频微波信号产生.在此基础上,分析了马赫曾德尔调制器直流偏置点、射频调制信号幅度和初始相位差等因素变化对边带选取性能的影响,并进行了相应的仿真实验,实验结果验证了该方法的可行性和有效性.     

Blind parameter estimation of pseudo-random binary code-linear frequency modulation signal based on Duffing oscillator at low SNR

Conventional parameter estimation methods for pseudo-random binary code-linear frequency modulation(PRBCLFM) signals require prior knowledge, are computationally complex, and exhibit poor performance at low signal-to-noise ratios(SNRs). To overcome these problems, a blind parameter estimation method based on a Duffing oscillator array is proposed. A new relationship formula among the state of the Duffing oscillator, the pseudo-random sequence of the PRBC-LFM signal, and the frequency difference between the PRBC-LFM signal and the periodic driving force signal of the Duffing oscillator is derived, providing the theoretical basis for blind parameter estimation. Methods based on amplitude method, short-time Fourier transform method, and power spectrum entropy method are used to binarize the output of the Duffing oscillator array, and their performance is compared. The pseudo-random sequence is estimated using Duffing oscillator array synchronization, and the carrier frequency parameters are obtained by the relational expressions and characteristics of the difference frequency. Simulation results show that this blind estimation method overcomes limitations in prior knowledge and maintains good parameter estimation performance up to an SNR of-35 d B.     

High-repetitive frequency millimeter-wave signal generation using multi-cascaded external modulators based on carrier suppression technique

We have numerically and experimentally investigated how to generate high-repetitive frequency millimeter (mm)-wave using multi-cascaded intensity modulators based on optical carrier suppression (OCS) scheme. We have found the rule how to generate the high-repetitive frequency mm-wave by adjusting the repetitive frequency of the radio-frequency (RF) signals and the phase relation between the RF signals on the intensity modulators. Based on this rule, we have experimentally demonstrated to generate over 80 GHz optical mm-wave.     

Generation of optical carrier suppression millimeter-wave signal using one dual-parallel MZM to overcome chromatic dispersion

In this paper, we have proposed a novel approach to generate optical carrier suppression (OCS) mm-wave with signal only carried by one first-order sideband using a dual-parallel MZM in radio-over-fiber (RoF) system, and the transmission performance was also investigated. As the optical mm-wave signal is transmitted along the fiber, there is no time shift of the data symbols resulting from the group velocity dispersion in the fiber because the signal is only modulated on one sideband. The simulation results showed that the eye diagram keeps open and clear even when the optical mm-wave signals are transmitted over 96-km and the power penalty is about 1-dB after fiber transmission distance of 60-km, which is quite consistent with our theoretical analysis. Furthermore, the proposed OCS optical mm-wave generation approach is also used in a full-duplex RoF link based on wavelength reuse at the base station for the uplink due to another pure sideband without carrying data. The bidirectional 2.5-Gbit/s data is successfully transmitted over 40-km standard single mode fiber with less than 0.5-dB power penalty in the simulation. Both the unidirectional RoF downlink and the full-duplex RoF system have good performance.     

An embedded pilot power based channel estimation and low-complexity feedback equalization scheme for OTFS system

Orthogonal Time Frequency Space modulation (OTFS) has evolved as an astounding modulation technique for high-speed communication in a doubly dispersive channel. In any wireless communication system, channel estimation and equalization are essential at the receiver to recover the transmitted data. To accomplish this for the emerging OTFS based systems, a modified embedded pilot-based channel estimation technique and low complexity feedback equalization algorithm for integer Doppler shifts in the delay-Doppler domain are proposed in this paper. Our channel estimation scheme exploits embedded-pilot arrangement, and the symbol equalization relies on the Interference calculation and its mitigation iteratively. To achieve this we contemplate a prudent arrangement of symbols in the OTFS frame in such a way that the Guard symbols prevent the interference between data symbols and the pilot symbol at the receiver. Two distinct lumps of received data of the same OTFS frame will be engaged in channel estimation and data detection. An analytical expression of the theoretical Cramer Rao Lower Bound (CRLB) is derived and plotted for the proposed channel estimation scheme. The attained simulation results for Bit-Error-Rate (BER) under the proposed scheme show a significant error rate improvement over the Minimum Mean Squared Error (MMSE) equalization algorithm. Further, a lower computational complexity is also achieved in comparison with modified MMSE detection and MP detection algorithms.     

Novel low‐loss waveguide delay lines using Vernier ring resonators for on‐chip multi‐λ microwave photonic signal processors

In this paper, novel photonic delay lines (DLs) using Vernier/non‐identical ring resonators (VRRs) are proposed and demonstrated, which are capable of simultaneous generation of multiple different delays at different wavelengths (frequencies). The simple device architectures and full reconfigurability allow the DLs to be integrated with other functional building blocks in photonic integrated circuits to realize on‐chip, complex multi‐λ microwave photonic signal processors with reduced system complexity. To prove the concept, DLs using VRRs in cascaded and coupled configurations have been fabricated in TriPleX^TM waveguide technology, which enables a very low delay‐induced loss of approximately 0.18 dB/100 ps. The fabricated DLs demonstrated simultaneous generation of four incremental delays, where a maximum incremental step of 550 ps and a corresponding top delay of 1650 ps were measured for a bandwidth up to 1 GHz. To our knowledge, this is the first report on VRRs for delay generation functionalities.