查询词典 difference frequency

Taking frequency conversion of semiconductor transistor as an example, the basic principles and some problems related are introduced in the article, integrating emitter-injected frequency conversion circuit of transistor, which is often used in superheterodyne to discuss about it.

分析了变频的基本原理和设计变频器的有关注意问题；从三极管输入回路和输出回路的信号入手，讨论了超外差式收音机常用的变频电路的工作原理。

Since the superheterodyne receiver was invented, mixer has long been the research focus in communication and radio frequency circuit fields, which is the key component to realize the frequency translation.

自从超外差接收机的结构被提出以后，混频器作为其中实现频率搬移的关键部件一直都是通信和射频电路研究的热点。

The frequency spectrum of noise is very wide, and will superpose with useful signal that has the notable influence to digital measurement and frequency spectrum analysis. Base on it, the method of solving zero floating problem of Waveform digital reconstruction process is proposed.

噪声的频谱噪声频谱很宽，将与有用信号的频谱重叠，对数字测量、信号处理和谱分析有显著的影响，并提出了解决波形数字重构中数字示波器零漂影响的方法。

Measure character: Frequency limits: CH1:dResolution of C ～ 225MHz frequency: 10 / second time-interval resolution : N/A measures speed: Can amount to 200 times measure / the second mixes in limits of the voltage on GPIB sensitivity : DC ～ 100MHz: 200MHz of ～ of 5Vac+dc 100MHz of 20mVrms ～±: 225MHz of ～ of 5Vac+dc 200MHz of 30mVrms ～±: Input of 5Vac+dc of 40mVrms ～± adjusts:(CH1 chooses) impedance, coupling: 1M Ω or 50 Ω, ac or Dc are low connect filter: 100kHz, but switch attenuation:× 1 or reference of × 10 exterior time base inputs: 1, 5, 10MHz sparks: CH1, to rising / drop the edge sparks, the percentage that uses signal n or absolutely voltage install n, setting sensitivity mixes to low, medium or tall gate start: Automatic, the hand is moved (setting gate time or resolution digit); Exterior, defer interface: Standard GP-IB(IEEE 488.1 and 488.2), take; of SCPI compatible language to say RS-232 power source only: 10 ％ of 100-120VAC ±, 50, 60 or 10 ％ of 400Hz ± 10 ％ of 220-240VAC ±, 50 or 10 ％ of 60Hz ± are suttle: 3kg dimension: 348.3mm of × of 212.6 × 88.5H

测量特征：频率规模：CH1：dc～225MHz 频率分辨率：10位/秒时候距离分辨率：N/A 测量速度：可达200次测量/秒在GPIB上电压规模和灵敏度： DC～100MHz： 20mVrms～±5Vac+dc 100MHz～200MHz：30mVrms～±5Vac+dc 200MHz～225MHz：40mVrms～±5Vac+dc 输入调节：(CH1选择)阻抗，耦合： 1MΩ或50Ω，ac或dc 低通滤波器： 100kHz，可切换衰减：×1或×10 外部时基参考输入： 1，5，10MHz 触发： CH1，对回升/回升沿触发，用信号电平的百分数或相对电压设置电平，设置灵敏度至低、中或高闸门和启动：主动，手动(设置闸门时候或分辨率位数)；外部，延迟接口：尺度GP-IB(IEEE 488.1和488.2)，带SCPI兼容说话；只讲RS-232 电源：100-120VAC±10％，50，60或400Hz±10％ 220-240VAC±10％，50或60Hz±10％净重：3kg 尺寸：212.6×88.5×348.3mm

The design of the sweep signal generator based on DDS is carried through mainly in the paper. And the generator has two ways in the frequency output: sweep and dotted. It also possesses other functions, like frequency measurement and sweep speed control.

本文重点进行了基于DDS的扫频信号发生器的设计，该发生器具有扫频和点频两种频率输出方式，还具有测频、扫速控制等功能。

Using the simulation calculation program and adopting the single factor analytic approach, simulation results are gotten and conclusions can be drawn from the simulation results. The parameters have a little influence on vibration of the driver's seat when the frequency of the vibratory force is larger than 20Hz, and the zone that the parameters have great influence on vibration of the driver's seat is nearby the sympathetic vibration frequency of the system which is about lOHz.

利用编制的模拟计算程序，采用单因素分析法，分析了各参数对驾驶员座椅处振动位移的影响：在激振力频率大于20Hz后，各参数对驾驶员座椅处振动影响较小；各参数对座椅振动影响较大的区域在激振力频率为10Hz附近的共振区。

Secondly, the cutter of the machine was studied from reducing vibration, emphasis on knives array, homeostasis. To apply "ANSYS"method, At the same time, it was known that inherent frequency of the main axis was so far higher than vibratory frequency, and the machine main axis'rotational speed won't cause sympathetic vibration.

其次，本文从减少振动入手对9LRZ-80型秸秆揉切机的关键部件切碎器进行分析，着重对动刀片的排列、动平衡等进行分析研究，并通过有限元分析，得到切碎器主轴固有频率远远大于机器振动频率，机具的转速不会造成共振的危害。

In the part of the vibration experiments and analysis, firstly, used the simple-beam theory to estimate the natural frequency of the beam of the 20-headed computerized embroidery machine.secondly, measured the beam of its low rank natural frequency, the beams horizontal vibrating acceleration amplitude, speed amplitude and the displacement amplitude in different rev and different turn parts. Found that it is sympathetic vibration, which bring on the thread-broken rate rise rapidly. On this base, established the finite element analysis modle of the vibrating beam, and took on hamonic analysis and modal analysis with the mold. The rusult of test and analysis offer the basis for farther improvement of the computerized embroidery machine.

振动分析部分，首先由简单梁理论出发，对横梁的固有频率进行估算；接着通过测振仪器对20头电脑刺绣机横梁进行了试验模态分析和不同工况振动测试；获得了横梁前四阶固有频率和模态振型，以及在不同工作转速、不同回转部件下横梁振动的加速度幅值、速度幅值和位移幅值；找到了横梁振动加剧的原因——共振；在此基础上建立了符合实际情况的横梁有限元模型，对模型进行了模态和谐响应计算，证实了模型的可靠性，为下一步的改进设计提供了依据。

By Using CPB to analyze the sound insulation character, it show that when the cavity depth is 30mm, the sympathetic vibration exist around the centre frequency of 200Hz of the system, the frequency character contours of sound insulation represent a lowest value. While the cavity depth is 40mm

使用CPB分析材料组合系统的隔声特性，当空腔深度为30mm，系统在中心频率200Hz附近产生共振，隔声频率特性曲线在该位置形成一个低谷；当空腔深度为40mm，隔声频率特性曲线在中心频率为160Hz位置形成一个低谷。

The invention is used for realizing the frequency-division multiplexing synchronical transmission of the broadcasting TV signals, which can decrease the same-frequency interference of the crossing area of the broadcasting TV carrier signals and reduce system cost, thereby causing the system debug to be simpler.

本发明用于实现广播电视信号的频分复用同步发射，降低广播电视高频载波信号的相交区域的同频干扰，降低系统成本，使得系统调试更加简单。

For the head-teacher of the class said that I had seriously broken the school rules,which led me to a three-day suspend class.

为什么呢？因为我的班主任说我严重的违反了校规，于是让我停课三天。

Many of them believe that the conversion of thousands of working-class folk in England spared that nation from the mass carnage and the tyranny that came with the revolution in France.

他们之中有许多人相信，在英国数以千计的劳工阶级之悔改信主使英国免於遭受如法国大革命所造成的大屠杀和专制暴政。