Industrial, scientific, and medical

Frequency Allocations. Under ideal conditions, an optimum frequency or frequency band should be selected for each appHcation of microwave power. Historically, however, development of the radio spectmm has been predominantly for communications and information processing purposes, eg, radar or radio location. Thus within each country and to some degree through international agreements, a complex Hst of frequency allocations and regulations on permitted radiated or conducted signals has been generated. Frequency allocations developed later on a much smaller scale for industrial, scientific, and medical (ISM) appHcations. 

J. Thunry, Microwaves Industrial, Scientific and Medical Applications, Artech House, Boston, Mass., 1992. 

Industrial, Scientific and Medical Equipment," Rules and Regulations, Eederal Communications Commission, Vol. II, Part 18, subpart H,... 

Table 2.1 ISM microwave frequencies (for industrial, scientific, and medical use) (data from [6]).

Industrial scales, 26 243-245 Industrial, scientific, and medical (ISM) frequency allocations, 16 510-512 Industrial screens, types of, 16 616 Industrial separations, 16 633 Industrial sheeting, LLDPE, 20 207 Industrial solvents, 23 85-124 behavior of, 23 96-109 characteristics of, 23 89-96 classification of, 23 85-87 electronic and electrical effects of, 23 96-97... 

As it was mentioned earlier, mierowaves are electromagnetie waves having a frequeney ranging from 300 MHz and 0.3 THz. Most of the existing apparatuses, however, operate between 400 MHz and 60 GHz, using well defined frequeneies, allocated for industrial. Scientific and Medical (ISM) applications. Among them, the 2.45 GHz is widely used for... 

J. Thuery and E. H. Grant (eds). Microwaves Industrial, Scientific, and Medical Applications. The Artech House microwave library. 1992, Artech House Boston, xviii, 670. 

The key limiting factor is the penetration depth of microwave irradiation, which is only a few centimeters in most solvents at 2.45 GHz. An issue therefore arises in getting sufficient microwave power into the reaction mixture to achieve the desired heating effect. The core of a large reactor vessel will not receive any microwave radiation as it will all have been absorbed by the outer layers. As a result, the center is effectively conductively or convectively heated, and the potential benefits of microwave heating will be lost. Penetration depth does, however, vary with frequency. Only a limited number of Industrial, Scientific, and Medical (ISM) frequencies are allowed so as not to interfere with military and civil aviation frequencies and telecommunications. Alternative frequencies are used for other large-scale applications and thus may provide an alternative solution to the scale-up of micro-wave chemistry. ... 

Source CENELEC European Standard, CISPR 11, modified. Limits and Methods of Measurement of Radio Disturbance Characteristics of Industrial, Scientific, and Medical (ISM) Radio-Frequency Equipment, 1991. With permission. 

The frequencies for RF heating are between 1 and 100 MHz while those for microwave heating are between 300 MHz and 300 GHz. However, Industrial, Scientific, and Medical (ISM) bands for industrial heating have been established by international agreement. These are 13.56, 27.12, and 40.68 MHz for RF heating and 896, 915, and 2450 MHz for microwave heating [14]. 

Limits and Measurement of RFI for Industrial, Scientific, and Medical Equipment... 

For EMC, Product Family Standards examples are EN 55011 (Emissions for Industrial, Scientific, and Medical Products), EN 55022 (Emissions for Information Technology Equipment), EN 55014 (Emissions for Household Appliances), and EN 55104 (Immunity for Household Appliances). 

Secondly, it operates in a highly crowded frequency range because most of the ISM (industrial, scientific, and medical) applications operate in the same range. 

Microwaves are electromagnetic waves between infrared and ladiofiequency waves. The wavelengths are in the range of 1 cm to 1 m (30 GHz to 300 MHz). To bypass interaction problems with telecommunication, the application of microwaves must be used in defined frequency bands (industrial, scientific and medical frequencies, ISM) see Table 15.2. 

Bluetooth exchanging data over short distances (using short-wavelength UHF radio waves in the industrial, scientific, and medical [ISM] band from 2.4 to 2.485 GHz) from fixed and mobile devices and building PANs... 

Resonance frequency(ies) the application for which the antenna is intended will specify the frequency or multiple frequencies of resonance of the antenna. For example, industrial, scientific, and medical (ISM) band antennas are required to resonate at one (or more) of the ISM frequencies (868 MHz, 2.45 GHz, 5.8 GHz). An antenna operation requires that the antenna s input impedance is optimally matched to the source impedance, thus the injected power is maximally converted to the form of radiated field. The concept of resonance is strictly related to the reflection coefficient, which is described next. 

Industrial, scientific, and medical bands are reserved portions of the radio spectrum, defined by the ITU Radio Regulations [23], that are employed in body-centric wireless communication applications and, more in general, for other industrial, medical, and scientific applications. The majority of textile antennas developed to date are intended for operation in some of those ISM bands, especially in the 2.45 GHz, by far the most popular for wearable antennas, and 5.8 GHz bands. The first band represents a good trade-off between antenna dimensions (inversely proportional to fiequency) and path loss (increasing with frequency), whereas the second is more convenient when... 

For systems such as wireless LANs to operate without a FCC site license, the industrial, scientific, and medical (ISM) frequency bands were created. There are two such bands, 902-928 MHz and 2.400-2.484 GHz. The FCC requires that transmission on these bands must use either frequency hopping or direct sequence spread spectrum transmission. The more restrictive IEEE 802.11 standard, however, limits FHSS to the 2.400-2.484 GHz band, so that the lower frequency band is reserved for DSSS systems. FCC requirements also dictate certain parameters that influence the hopping pattern for FHSS systems. For example, the FCC dictates that in the 2.4-GHz frequency band, a FHSS transmitter must not spend more than 0.4 s in any one frequency slot every 30 s and that the transmitter must hop through at least 75 frequency slots in the frequency hopping pattern (Rigney, 1995). 

At the frequencies allocated for industrial, scientific and medical purposes between 13.56 and 40 680 MHz, those used for heating applications at 13.56, 27.12, 896 and 2450 MHz are in general use for domestic, commercial and industrial purposes. They may employ substantial field strengths that could cause severe burn injuries, so precautions are necessary to contain the radiation and prevent access into wave guides and resonant chambers and between applicators when the apparatus is energised. This is effected by bolted-on covers which require tools for their removal, or access doors interlocked with the supply so that the supply is off when the door is open. 

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