Radio frequency radiations

Electromagnetic interference (EMI) refers to the interaction between electric and magnetic helds and sensitive electronic circuits and devices. EMI is predominantly a high-frequency phenomenon. The mechanism of coupling EMI to sensitive devices is different from that for power frequency disturbances and electrical transients. The mitigation of the effects of EMI requires special techniques, as will be seen later. Radio frequency interference (RFT) is the interaction between conducted or radiated radio frequency helds and sensitive data and communication equipment. It is convenient to include RFI in the category of EMI, but the two phenomena are distinct. 

On a practical level, while designing the PCB (printed circuit board), we have to be cautious in not putting too much copper at the switching node. Otherwise it becomes an effective electric-field antenna, spewing radiated radio frequency interference all around. 

The American Conference of Governmental Industrial Hygienists pubhshes workplace exposure limits based on power density, electric field strength squared, and magnetic field strength squared for particular frequency bandwidths. This standard includes radio and microwave frequencies. Table 21-2 lists the ACGIH Threshold Limit Values (TLVs), which provide guides for evaluation and control of exposure to radio frequency and microwave radiation. Radio frequency radiation exposures should be as low as reasonably possible. 

Groundwave That portion of radiated radio frequency energy that is not influenced by the ionosphere. 

Unintentional (incidental) radiating devices - Devices that radiate radio frequencies but is not considered their primary function. 

If energy of the proper frequency is supplied, a transition between these quantum states occurs with the absorption of an amount of energy equal to the separation of the states. The frequency of the absorbed radiation lies in the radio-frequency range and depends on the local magnetic field at the atom in question. 

A unique process for chemical stabili2ation of a ceUular elastomer upon extmsion has been shown for ethylene—propylene mbber the expanded mbber obtained by extmsion is exposed to high energy radiation to cross-link or vulcani2e the mbber and give dimensional stabUity (9). EPDM is also made continuously through extmsion and a combination of hot air and microwaves or radio frequency waves which both activate the blow and accelerate the cure. 

Consider the following statements about electromagnetic radiation and decide whether they are true or false. If they are false, correct them, (a) The total intensity of radiation emitted from a black body at absolute temperature T is directly proportional to the temperature, (b) As the temperature of a black body increases, the wavelength at which the maximum intensity is found decreases, (c) Photons of radio-frequency radiation are higher in energy than photons of ultraviolet radiation. 

True, (c) False. Photons of radio frequency radiation are lower in energy than photons of ultraviolet radiation. 

Radiation with long wavelengths falls in the infrared, microwave, or radio frequency regions. Heat lamps make use of infrared radiation, microwave ovens cook with microwave radiation, and radio and television signals are transmitted by radio waves. 

C07-0055. Refer to Figure 1 A to answer the following questions (a) What is the wavelength range for radio waves (b) What color is light whose wavelength is 5.8 X 10 m (c) In what region does radiation with frequency of 4.5 X 10 Hz lie ... 

The various forms of spectroscopy find widespread application in kinetic studies. They are usually well suited for application to in situ studies of the characteristics of the reaction mixture. The absorption by a reacting system of electromagnetic radiation (light, microwaves, radio-frequency waves, etc.) is a highly specific property... 

Features common to all CVD reactors include source evaporators with an associated gas handling system to control input gases and gas-phase precursor concentrations, a reactor cell with a susceptor heated by either radio frequency or infrared radiation, and an exhaust system to remove waste products (which may include a vacuum pump for low-pressure operations). Substrate temperatures can vary from less than 200 °C to temperatures in excess of 1000 °C, depending on the nature of the material layer and precursor used. Schematic diagrams of some simple CVD reactors are shown in Figure 4. 

---