中频

A CW carrier signal, generated by Agilent Signal Generator, is transmitted to the subject, which reflects the modulated waves to the receiver antenna. The Agilent Spectrum Analyzer, with an under-conversion module inside, demodulates the received signal to 70MHz IF signal, which is then sampled by a ADC module in Agilent Vector Signal Analyzer. Digital quadrature demodulation is used to convert IF signal to baseband. We could finally get the respiration and heartbeat signal by further analyzing the baseband signal.

该系统由信号发射器产生载波，通过天线发射到被测物体；频谱分析仪内置的下变频模块将由物体反射回来的信号下变频到70MHz中频；中频信号经矢量信号分析仪采样，然后经过数字正交解调变频到基带信号；对基带信号进行滤波、FFT等进一步的数字信号处理后即可获得探测的心跳和呼吸信号。

Most manufacturers use frequency induction hardening process, after the nitrogenation or chromeplating, nitrogenation of thickness of 0.5 to 2.7 0.6 ㎜, chrome-plated layer thickness ㎜ 0.10 ~ 0.15, mainstream technology for after the chromeplating frequency induction hardening.

目前多数厂家采用复合处理，中频淬火后进行氮化或镀铬，氮化层厚度为0.5～0.6㎜，镀铬层厚度为0.10～0.15㎜，主流工艺为中频淬火后镀铬。

In this paper, based on the analysis of the IF GPS signal theoretic model, a digitized GPS signal generator is implemented in Matlab, which can generate the received GPS signal at the digitized IF frequencies, and the noise and receiver clock error are also simulated.

本文在中频GPS信号理论模型分析的基础上，用Matlab实现了一种数字GPS信号生成模型，它能够在数字中频上产生GPS接收信号，其中包含仿真的噪声和接收机时钟误差。

Based on the theoretic modeling and analysis of the IF GPS signals,an accurate software simulator of IF GPS signals is implemented in Matlab/Simulink,the effects of noise, under-sampling and receiver clock error are also simulated.

在对中频GPS信号理论建模与分析的基础上，采用Matlab/Simulink构建了一种精确的数字中频GPS信号软件模拟器，考虑了噪声、欠采样以及接收机时钟误差等的影响。

The company has 8 tons / hour cupola, 750KG intermediate frequency electric furnace, heat treatment furnace, molding machine, shoot core machine, CNC lathe, milling machine, crankshaft grinder, such as the main production equipment, has formed a cupola, medium frequency melting furnace, manual modeling, machine modeling as a primary means, such as ductile iron, gray cast iron, cast aluminum, cast copper production lines, is a fairly large scale, Strict quality control, production means complete, the products of different specifications, quantity and user requirements and strong adaptability professional foundry company.

公司拥有 8吨/小时冲天炉、 750KG 中频电炉、热处理电炉、造型机、射芯机、数控车床、铣床、曲轴磨床等主要生产设备，形成了以冲天炉、中频炉熔炼，手工造型、机器造型等为主要手段的球墨铸铁、灰口铸铁、铸铝、铸铜的生产线，是一个具有相当规模、质量控制严格、生产手段齐全、对产品的品种规格、数量及用户要求的应变能力强的专业铸造公司。

Having studied the digital down-conversionprocess of IF signal before the base band process which follows A/D conversion in wireless communication,the paper puts forward a new idea of utilizing the FPGA to realize multi-channel digital signal DDC.Through analyzing the features and performances of CIC filters,HB filters and multiphase-filter,we combine them with decimators and decimate the A/D data,thus reducing the digital signal rate and the load of DSP when processing the base band signal.

软件无线电技术是在通用的开放式无线电智能平台上，通过安装不同的软件来完成各种通信功能，其结构的基本特征之一就是使A/D变换尽量靠近射频端，目前的方案是在中频对模拟信号进行数字化，对中频数字信号进行下变频处理，使数字信号量降低到高速DSP能够处理的程度[1]。

At first the Digital frequency shifting repeater transforms the original signal to the 70MHz IF signal in the donor, then the Frequency shift relay digital processing unit Digital Spread Spectrum the IF signal and through the 5.8GHZ signal to transmit to the remote end.

数字移频直放站首先在近端机内将将信源信号转换为数字70MHZ中频信号，通过&移频中继数字处理单元&将中频信号数字扩频后通过5.8GHZ的信号传送到远端。

As the key part,the Silicon Controlled Rectifier is equipped in Induction Heating Machine,its performance directly effect on efficiency and life.

可控硅作为中频加热设备的主要元件，其性能直接影响到中频设备的使用效率及寿命。

For example, communication power supply, solar cell, UPS, invertors, gasoline dynamotor, and diesel oil dynamotor etc. There are deferent voltage DC power supplies, deferent frequency AC power supplies.

例如，通信电源，太阳能蓄电池，UPS电源，航空中频静变电源，汽油、柴油发电机组等，包括不同电压等级直流电源，工频、中频的交流电源。

Rubber sheathed flexible cable with intermediate frequency, low-consumption and equilibria for aviation

航空用中频低耗平衡橡套软电缆适用于中频 400HZ ，交流额定电压 250V 及以下的航空机场供电及检测电器用的连接线

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。