时分导频位CDMA系统上行链路阵列接收及部分多址干扰抑制技术

针对时分导频位ＣＤＭＡ系统上行链路，本文提出了导频位输助ＬＭＳ－ＤＲＭＴＡ算法加上部分多址干扰对消的空时联合干扰抑制接收方案。由于阵列的干扰抑制作用，其输出信号中只剩下少量强的多址干扰信号。部分干扰对消法只对阵列输出中的强多址干扰信号进行干扰估计并抑制，这样一方面大大降低了系统处理的运算量及缓存空间，另一方面又消除了因弱多址干扰估计的不准确而造成的系统性能下降，并且相对于自适应全多址干扰对消有更好的系统稳定性。仿真实验表明该方案比全干扰用户对消法具有更好的干扰抑制效果。

基站阵列接收方案的一种盲自适应算法

本文主要叙述了一种基站阵列接收方案中的盲自适应算法。在此算法中,我们使用一般的信息位作为训练信号来实现智能天线权值的更新。本方法的贡献在于,和导频位辅助LMS—DRMTA算法一样比传统的LS—DRMTA算法大大降低了运算量,同时该算法比导频位辅助LMS—DRMTA算法获得了更好的误码率、系统容量以及更好的波束图。

WCDMA系统上行链路空时干扰抑制技术

该文提出一种将自适应并行干扰对消技术简化为利用软判决变量在一个比特周期内的平均作为再生信号幅度估计的并行干扰对消方法,这种简化大大降低了原方法的运算量,而且具有很好的稳定性。仿真实验表明在单阵元接收情况下,简化方法的对消效果较原方法有些下降,但在阵列接收然后进行并行干扰对消的情况下,二者的性能基本没有差别。因而该文针对WCDMA系统上行链路的帧结构特征,进一步提出了导频位辅助LMS-DRMTA算法加上软判决变量平均幅度估计法的空时联合WCDMA系统的干扰对消方案。

Defects detection in typical positions of bend pipes using low-frequency ultrasonic guided wave

In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE(finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.

Joint Estimation of Carrier Frequency and Phase Offset Based on Pilot Symbols in Quasi-Constant Envelope OFDM Satellite Systems

Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.

Synchronization for the Environment of OFDM Cooperative Communications Based on Preamble Design and Phase Rotation

Timing and carrier frequency offset estimation are critical issue for OFDM cooperative communications. In view of the complexity and high accuracy requirement, 1/2 and 1/4 pilot symbol cycle CAZAC sequence structures are defined as the pilot frequency sequence. Estimation within one symbol cycle is carried out through averaging samples of two neighboring symbol cycles, after which the operation is expanded to all the symbol cycles in one band group. Taking multipath effect into account, the concept of phase rotation is proposed for a further step. Adjust the phase difference of estimated symbols by phase rotation, and cross estimation could be done. Meanwhile, timing scheme works within one cycle training sequence. Theoretical and simulation analysis indicate that CRLB does not only relate to estimation symbol length, but also be influenced by phase difference of estimation symbols seriously. In the condition that the length of estimation is fixed, the bigger the phase rotation angle is, the smaller the CRLB is. The complexity of proposed algorithm is less than full cycle average estimation method for almost 50%. Meanwhile, the estimation accuracy is approximate with the full cycle average estimation method as well. Timing scheme with the defined preamble structure is also proposed. Simulation proves its efficiency.

AN ADVANCED DUAL-FREQUENCY POSITIONING ALGORITHM FOR SATELLITE NAVIGATION RECEIVERS

With the development of the Ground Positioning System (GPS) modernization and the expectable implementation of Galileo, people pay more and more attention to civil applications on multi-frequency signals. This paper proposes a new and advanced positioning algorithm for the dual-frequency satellite navigation receivers, concerning the various influences of all the ranging error sources and taking advantage of the Klobuchar single-frequency ionospheric model. The paper also presents positioning precision provided by the new algorithm. Theoretical analysis and experimental results show that, the new dual-frequency positioning algorithm can achieve higher positioning accu- racy than the single-frequency positioning algorithm and the traditional dual-frequency positioning algorithm.

Therapeutic observation on superficial needling with different frequencies for intractable facial paralysis

Objective:To obverse the therapeutic effect of superficial needling with different frequencies for intractable facial paralysis.Methods:A total of 120 patients with intractable peripheral facial paralysis were allocated into a superficial needling with high frequency group(150 times/min),a moderate frequency group(100 times/min)and a low frequency group(50 times/min)according to the random number table method.The Toronto facial grading system(TFGS)was used to evaluate facial nerve functions before treatment and after 2 weeks and 4 weeks of treatment respectively.The electromyography(EMG)test of the mandibular branch of facial nerve was used to compare the motor nerve conduction velocity(MCV),sen sory nerve con ducti on velocity(SCV)and mono phasic acti on pote ntial(MAP)among differe nt groups,and was done before treatment and after 4 weeks of treatment.The clinical efficacy was also compared.Results:After 2 weeks and 4 weeks of treatment,the changes of TFGS scores in the three groups all showed statistical significanee(all P<0.05)z and the TFGS score in the low frequency group was substantially higher than that in the other two groups.After treatment,the changes of the MCV and SCV in the three groups all showed statistical significanee(all P<0.05),and the results in the low frequency group were higher than those in the other two groups;the change of MAP in the three groups showed no statistical significance(P>0.05).The total effective rate was 65.0%,80.0%and 95.0%in the high frequency group,moderate frequency group and low frequency group respectively,and the betweervgroup differences showed statistical significanee(P<0.05).Conclusion:Compared with the superficial needling with high and moderate frequencies,superficial needling with low frequency can produce more significant clinical efficacy for intractable facial paralysis.

Ag4Hg（SeO3）2（SeO4）: a novel SHG material created in mixed valent selenium oxides by in situ synthesis

Explorations of new second harmonic generation materials in Ag^+-Hg^2+/Bi^3+-selenites systems afforded three new silver selenium oxides, namely, Ag4 Hg(SeO3)2(SeO4)(1), Ag2Bi2(SeO3)3(SeO4)(2) and Ag5 Bi(SeO3)4(3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3 D open framework with 4-, 6-and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4(KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 e V respectively. Theoretical calculations disclose that compounds2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.