摘要：To overcome the shortcoming that the traditional frequency measurement method does not meet the requirement of equal precision, a design method of equal precision frequency meter based on FPGA is proposed. The system modules are all realized in Altera’s FPGA chip EP2C35F672C8. Experimental results show that the system can measure frequencies with equal precision in the whole frequency range, and the measurement error is small. It achieves the requirement of equal precision measurements.

摘要：frequency selective surfaces (FSSs) have been successfully used in constructing microwave absorbers which demonstrate the ability of modifying and improving its absorbing performances. In this paper, microwave absorber based on ferromagnetic nano-films has been proposed and investigated with a structure similar to that of the Salisbury screen except that the resistive sheet is replaced by FSS of square patch array of the nano-film. We have explored the FSS absorber from three aspects: equivalent circuit model, electromagnetic full-wave simulation and the actual sample measurement. By carefully tuning the patch size, the thickness of the dielectric spacer and the specification of the ferromagnetic nano-film, we obtain the optimized performance of broadband microwave absorbing. Due to the light weight of the nano-films, the proposed absorbers can achieve an ultra-low surface density less than 0.25 kg/m2.

摘要：In this paper a new active RFID system at 2.45 GHz based on the low-power system-on-chip CC2530 RF transceiver is designed and implemented. Only by using of an integrated multi-channel fast chip, both the MCU and RF operations are done which makes the RFID more reliable and reduces the complexity of the hardware and cost, vividly. This RFID system utilizes the Zig-Bee IEEE 802.15.4 standard in the ISM band. A lot amount of energy is restored by setting Tags in the sleep mode in the most of times. The maximum transmission range of 80 m at the output power of 4.5 dBm is obtained. The main application of this system is for the container identification with precise operation and high accuracy. An active Tag with unique ID is mounted on each vehicle. By enabling the AUTOCRC error detection possibility, minor errors are detected in the received frames. Receiver sensitivity of –97 dBm and current consumption of 1 μA in the sleep mode and 29.6 mA in the active mode are reported.

摘要：This paper presents the effect of the high voltage direct current (HVDC) transmission system based on voltage source converter (VSC) on the sub synchronous resonance (SSR) and low frequency oscillations (LFO) in power system. Also, a novel adaptive neural controller based on neural identifier is proposed for the HVDC which is capable of damping out LFO and sub synchronous oscillations (SSO). For comparison purposes, results of system based damping neural controller are compared with a lead-lag controller based on quantum particle swarm optimization (QPSO). It is shown that implementing adaptive damping controller not only improves the stability of power system but also can overcome drawbacks of conventional compensators with fixed parameters. In order to determine the most effective input of HVDC system to apply supplementary controller signal, analysis based on singular value decomposition is performed. To evaluate the performance of the proposed controller, transient simulations of detailed nonlinear system are considered.

摘要：A detailed design methodology of a micro-scale 2-DOF energy harvesting device that can harvest human motion energy of low frequency and wide bandwidth is developed. Based on the concept of the 2-DOF vibration absorber, device parameters are selected to harvest energy at low frequency of 1-10 Hz and wide bandwidth with ±20% of the mean frequency, which matches the human motion. The device dimensions are limited to 40 × 30 × 10 mm3 to fit with the human wrist size. Then, a finite element model is developed to investigate the system performance with the selected parameters. When subjected to harmonic excitation of 1 g, the proposed 2-DOF device is able to provide a power of at least 10 μW in between the two close resonant peaks of 4 Hz and 6 Hz, which is the target frequency range. The device shows very high power per square frequency compared with the reported harvesters.

摘要：In this paper, we present a novel and efficient method for the design of a sharp, two dimensional (2D) wideband, circularly symmetric, FIR filter. First of all, a sharp one dimensional (1D) infinite precision FIR filter is designed using the frequency Response Masking (FRM) technique. This filter is converted into a multiplier-less filter by representing it in the Canonic Signed Digit (CSD) space. The design of the FRM filter in the CSD space calls for the use of a discrete optimization technique. To this end, a new optimization approach is proposed using a modified Harmony Search Algorithm (HSA). HSA is modified in such a way that, in every exploitation and exploration phase, the candidate solutions turns out to be integers. The 1D FRM multiplier-less filter, is in turn transformed to the 2D equivalent using the recently proposed multiplier-less transformations namely, T1 and T2. These transformations are successful in generating circular contours even for wideband filters. Since multipliers are the most power consuming elements in a 2D filter, the multiplier-less realization calls for reduced power consumption as well as computation time. Significant reduction in the computational complexity and computation time are the highlights of our proposed design technique. Besides, the proposed discrete optimization using modified HSA can be used to solve optimization problems in other engineering disciplines, where the search space consists of integers.

摘要：With a lot of millimeter-wave(mm-Wave)applications being issued,wideband circuits and systems have attracted much attention because of their strong applicability and *** this paper,four transformer-based ultra-wideband mm-Wave circuits demonstrated in CMOS technologies are reviewed from theoretical analysis,implementation,to ***,we introduce a mm-Wave low-noise amplifier with transformer-based Gm-boosting and pole-tuning *** achieves wide operating bandwidth,low noise figure,and good gain ***,we review an injection-current-boosting technique which can significantly increase the locking range of mm-Wave injection-locked frequency *** on the injectionlocked principle,we also discuss an ultra-wideband mm-Wave divider with the transformer-based high-order ***,an E-band up-conversion mixer is presented;using the two-path transconductance stage and transformer-based load,it obtains good linearity and a large operating band.

摘要：Excel中的frequency()是数据统计分析人员常用的函数,但由于该函数在数据分布频度的统计方面存在设计上的不足,数据统计分析人员有时会舍其求它。本文分析了该函数的利弊,对该函数的用法进行研究,提出了修正其不足的使用方法。

摘要：利用主星和邻近星转发信号的互模糊函数(CrossAmbiguityFunction-CAF)进行定位参数的估计是通信卫星干扰源定位的一种重要方法。由于这种参数估计是二维平面上的迭代搜索运算,达到估计精度需要处理很长的数据,计算量巨大,处理速度一直是该方法应用的瓶颈。分析了参数估计精度对时间/带宽的要求,设计了具有不同分辨率的时域双模式搜索流程直接减少信号处理的数据点数,并提出了用卫星星历辅助产生搜索初值的方法,降低了CAF参数估计的运算量。新方法与传统试探方法的运算量比较和对实际信号的处理实验验证了处理方法的有效性。

摘要：The discrimination of synonyms has always been one of the great challenges for English *** assessment and evaluation as examples,this study analyses the similarities and differences of the two words,as well as their usage from the perspectives of frequency,stylistics,collocation and semantic prosody with the help of British National Corpus,and demonstrates the importance of corpus retrieval tools in synonyms ***,this paper will give some suggestions for English learners and teachers in English vocabulary teaching.