查询词典 radio frequency

The receiver's high-current capability enables it to effortlessly drive even difficult loudspeaker loads, while ultrawide bandwidth provides far superior phase linearity, lower distortion, greater high-frequency headroom, and more accurate frequency response in the audible frequency range.

接收器的高电流能力，使它能够毫不费力地驱动扬声器甚至难以负荷，同时提供超带宽远远优于阶段线性度，低失真，更多的高频率余量，以及更准确的频率响应的发声频率范围。

The transmit part adopts the phase-locked loop pattern of frequency synthesizing technology and uses the MC145152 and MC12022 chips to compose the phase-locked loop.It locks the frequency of the carrier-wave at 35MHz.The stabilization of the carrier-wave can be 4×10-5,the accuracy can be 3×10-5.The frequency modulation and the confection of the carrier-wave are realized by the capacity-changing diode V149 and the integration voltage-control oscillator MC1648 chip.The end power amplifier uses the audion 2SC1970 to make it work in the third magnifying state,it improves the efficiency of the magnifier and the power of the output reaches the design demand.

发射部分采用锁相环式频率合成器技术， MC145152和MC12022芯片组成锁相环，将载波频率精确锁定在35MHz，输出载波的稳定度达到4×10-5，准确度达到3×10-5，由变容二极管V149和集成压控振荡器芯片MC1648实现对载波的调频调制；末级功放选用三极管2SC1970，使其工作在丙类放大状态，提高了放大器的效率，输出功率达到设计要求。

Fast Fourier transformation and autoregressive model estimation, are the most common methods used in the frequency domain analysis. The fluctuation in the highfrequency bands are mediated by parasympathetic control, whereas the fluctuation in the low frequency bands are mediated by both sympathetic and parasympathetic nervous systems. The origin of the fluctuation in the very low and ultra low frequency ranges are less obvious.

频域分析法一般是利用快速傅位叶转换或自动回规模型估计法，高频处的变异是由副交感神经系统调控，低频处的变异则是由副交感神经系统共同调控，至於极低频处与超低频处的变异，其原因尚待厘清。

This frequency stabilization system is a self-adaptive thermal compensated frequency stabilization system, which is based on 80C196 single-chip-processor and uses the beat frequency lock as the criterion.

通过该系统的稳频，激光器的拍频稳定度达到1.05%，由于进一步的测试设备正在采购中，光频的稳定度和复现性尚未测量。

The performance of EFT is investigated, which indicates that time-frequency distributions using single-sided window could not accurately trace the variation of the instantaneous frequency, since their performance depend only on the history of the signal, so they are biased frequency estimator.

提出了基于对称阵元互Wigner分布平均的瞬时频率估计算法，这种方法利用多通道数据对时频分布的瞬时频率估计方法的性能进行了有效的改善，并且能够在低信噪比的条件下获得良好的估计效果， 6。

Aiming at the project request, the paper firstly introduces the theory of Frequency Hopping Communication, the theory of sampling and the principle of spectrum analysis using discrete Fourier transform, then combined with the characteristic and superiority of FPGA designs a channelizing detection method for the carrier frequency in Ultrashort Frequency Hopping signal based on FPGA.

然后结合现代可编程器件FPGA的特点与优势，设计了一种基于FPGA技术的信道化电子侦察方案。

This article first antenna, microstrip theory, the circular polarization technology, the theoretical discussion, in this based on the microstrip antenna of circular polarization method - corner square microstrip antenna, and has done a design simulation , and then do the design and further research to improve and eventually get a resonant frequency (S11 reflection coefficient corresponding to the minimum frequency) for the 1.5GHz and 1.43GHz, the frequency of circular polarization for the 1.46GHz, S11 is less than -10dB relative bandwidth, the VSWR is less than 2 is about 8.8% relative bandwidth, axial ratio less than 3dB relative bandwidth of about 2.2% of the right circular polarization microstrip antenna design case, which proved very good the circular polarization microstrip antenna theory, also fully confirmed by a square corner design is a practical program, and select the appropriate regulation of sticks is indeed able to improve the performance of the antenna.

本文先对天线、微带理论、圆极化技术等进行了理论论述，在此基础上，提出圆极化微带天线的实现方法——切角方形微带天线，并对此做了设计仿真，后又对这一设计方案做了改进及进一步研究，最终得到一个谐振频率（反射系数S11 的最小值所对应的频率）为1.5GHz和1.43GHz，圆极化频率为1.46GHz，S11 小于-10dB 的相对带宽、驻波比小于2 的相对带宽约为8.8%，轴比小于3dB 的相对带宽约为2.2%的右旋圆极化微带天线的设计案例，从而很好的印证了圆极化微带天线理论，也充分证实了切角方形是一种切实可行的设计方案，而选取合适的调节枝则确能提高天线的性能。

Researched influence of frequency on characteristic of electromagnetic wave transmission in tunnels, and analyzed characteristic of electromagnetic wave transmission in circular, arches and curved tunnels by method of metal wave guide, and gives approximate formulas of attenuation rate. Main conclusions we obtain are as follows: in circular,rches tunnels, if frequency is higher, attenuation rate is smaller, it is beneficial for EM waves to transmit, in curved tunnel, higher frequency, more attenuation rate ...

研究了频率对井下电磁波传输特性的影响，采用金属波导法分析了圆形、拱形及弯曲隧道中电磁波的传输特性并给出衰减率近似公式，得出主要结论：在圆形和拱形隧道中，频率越高，衰减率越小，越有利于电磁波的传播；在弯曲隧道中，频率越高，衰减率越大，不利于电磁波的传播；通过特性曲线与井下实验数据相比较得出在900MHz左右为井下无线通信系统传输信号最佳频段。

Under the control of microprocessor, this product with an oscillating implement embedded in can produce mulriple-scanning pulse electromagnetic wave with variable frequency and mulriple frequency conversion ultrasonic. Electromagnetic wave can get rid of the pests around electrical wire and ultrasonic can dispel the pests in other areas of the room. The product sends out frequency conversion signal of ultrasonic to circumambience. Once touches objects, it reflects and permeates the room. The combining of the two waves has mulriple effects on the central nervous and hearing system of the pests such as rats, cockroachs, spiders and ants. As a result, the pests would be on the rack and agonizing or even have the symptom of swivet and twitch.

它由完全内置的震荡器，在微电脑的控制下可产生多重扫描变频脉冲电磁波和复合变频超声波，电磁波主要解决电源线周围害虫的问题，而超声波是要消除室内其余区域的害虫，它向周围发射的变频超声波信号，当它碰到物体会反射，从而能充满整个房间，这两种波迭加在一起所产生的双重功效，对老鼠、蟑螂、蜘蛛、蚂蚁等害虫的中枢神经及听觉系统进行多重干扰，令其感到极度不适，恐慌不安，甚至表现出狂乱、抽搐等症状，并能使其丧失繁殖能力，迫使其逃离原地，从而达到驱赶害虫的目的。

By adopting modern optics information processing technology and changing frequency spectrum of optical signal, zero frequency spectrum was enabled to interfere with the first class frequency spectrum.

采用现代光学信息处理技术改变光信号的频谱，使零级频谱与一级频谱干涉，从而实现由位相到强度的调制，最终检测到透明材料的位相缺陷。

Listen,point and check your answers.

听，指出并且检查你的答案。

Warming needle is one of effective treatment methods for knee arthralgia aggravated by cold,and it is simple,safety,so it should be developed in clinical acupuncture and moxibustion extensively.

但以本院科针灸门诊在2005年1月—2006年6月期间共收治膝痛患者100余例，经过临床的诊断后，其中施以温针治疗的48例，疗效显著，报道如下。1临床资料本组病例48