Lili Guo

Research on the Radiation Characteristics of Leaky Coaxial Cable and Spiral Antenna in the Blind Zone

As an instrument to realize mobile communication in the blind zone, leaky coaxial cable (LCX) is recently widely used in communication systems of tunnels, mines, subways and so on. In this paper, beginning with the radiation theory of LCX and antenna, by the use of ray-tracing method, we take a tunnel for example to analyze its radiated field produced by both LCX and spiral antenna. By comparison, LCX shows advantages in the coverage of the radiated field in such special areas-the distribution of the radiated field is more uniform. The theories and results in this paper can be extended in other blind zones and have referenced values in further research on solving the problems of communication in the blind zone

Performance Studies of UWB Communication System Based on Parallel Combinatory Spread Spectrum

A new ultra wideband (UWB) communication system based on parallel combinatory spread spectrum (PCSS) is proposed in this paper. The proposed system have the advantages both of PCSS system and UWB system, such as the high efficiency of information transmission and excellent secret property. Thus, the proposed system can meet the needs of efficiency and security as the same time in the modern communication system. The simulation model is provided and the performance is analyzed. The simulation results indicate that the UWB system based on PCSS has a better bit error rate (BER) performance.

Blind Estimation of Multicarrier CDMA Sub-Carrier Frequencies Based on the High-Order Cyclic Cumulants

This paper proposed a method to estimate sub-carriers frequencies of multi-carrier CDMA signals utilizing higher-order cyclic cumulants, based on the cyclic stationary characteristic of multi-carrier CDMA signals. Because higher-order cyclic cumulants can effectively suppress stationary noise and non-stationary Gaussian noise, through theoretical analysis, we can prove that the higher-order cyclic cumulant of the multi-carrier CDMA signal using BPSK/QPSK modulation only exist in the cycle frequency of sub-carrier frequency under the above noise background, so it can estimate the sub-carrier frequencies of multi-carrier CDMA signals by detecting the peaks of cyclic frequencies. Theoretical analysis and simulation results have verified the correctness and effectiveness of the algorithm.

Study and application of FLMS recursive algorithm based on Space-time Adaptive Processing

Space-time Adaptive Processing (STAP) is usually applied to adaptive anti-jam system of Global Positioning System (GPS). It is the most effective way to reject the broadband interference. But STAP often dose matrix compute, which has a huge computational complexity. Paper investigates a recursive algorithm-Frost Least-Mean-Square (FLMS) algorithm. FLMS can reduce the workload of array signal processing and achieve real-time processing. By simulation, FLMS algorithm can not only well suppress the broadband jammer, but also suppress the number of interference more than that of the sensor elements of array antenna. FLMS algorithm makes it possibility that hardware achieves STAP.

Iterative Channel Estimation Algorithm for OFDM Systems with Bit-Interleaving

A new iterative channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems was proposed based on Maximum-Likelihood (ML) by using a specially designed training symbol. The proposed channel estimation utilizes the hard-decision information provided by the decoder of bit-interleaved coded modulation (BICM) to exchange the information between the channel estimator and the decoder. In BICM-OFDM systems, the simulation results show that the proposed algorithm not only reduces the number of the training symbols but also improves the accuracy of comunication system comparing with conventional algorithms.

Research on the radiated field's distribution of leaky coaxial cable in the blind zone

The path of electric waves of leaky coaxial cable (LCX) in the blind zone is analyzed in the ray-tracing method on the assumption that the bind zone is rectangular, and the distribution of the radiated field in the blind zone is calculated. Further, the effect of the period of the slots of LCX on the magnitude fluctuation is also discussed: a proper period can decrease the magnitude fluctuation of the radiated field. The method used in this paper can be generalized in other zones with different shapes. The theoretical basis is provided for the application of LCX in the blind zone

Study and simulating of adaptive array processing with effect of channel uniformity

Adaptive anti-jam processing used by Global Positioning System (GPS) usually works in an environment where interferences exist. The Power-Inversion (PI) algorithm is often applied to suppress interferences in the system. But variance of amplitude and phase which exists among antenna channel takes bad effect on adaptive anti-jam processing and PI algorithm, so we do our best to research the relation between channel uniformity and adaptive processing. When variance of amplitude and phase is limited under the definite condition, paper proves PI algorithm can not only reject interferences, but also conquer channel uniformity on a certain degree by academic researching and simulating. The conclusion has the advantage to engineering applications.

Study of GPS Nulling Antenna Based on Space-Time Processing Algorithm

Global Positioning System (GPS) receiver is confronted with the serious problem what is the bad electromagnetism environment, especially, the wideband interference. Currently, nulling antenna technology is the most effective way to reject the broadband interference. The FLMS algorithm of space-time adaptive processor (STAP) is developed for the robust array antenna, and is used to estimate the beamformer weighting vector adaptively with a low computational complexity. The result of simulation demonstrates the FLMS algorithm can well suppress the broadband jammer and improve the performance of GPS receiver.