ings can be detected with a microwave radiometer if the tumor is close enough to the surface. At RF a tumor can be detected from a depth of a few centimeters; at microwave frequencies a tumor can be detected only if it is on the skin or just below it. The antenna of the radiometer may be a large focusing antenna or a contact antenna pressed on the skin.

12.11.2 Diathermy

In diathermy, the temperature of a tissue or body is elevated by radiofrequency energy. Frequencies for diathermy are 27 MHz and 2.45 GHz. The temperature of the tissue is raised to between 39°C and 45°C. Higher temperatures, which kill cells, must be avoided. The power density may be 100 to 1,000 mW/cm2. The power is focused to a restricted area and sensitive parts of body, such as eyes, are protected. Raising the temperature has many positive effects: Blood vessels become distended and circulation quickens, muscles relax, the threshold of pain gets higher, the stretching ability of a connective tissue increases, the penetration ability of cell membranes increases, and metabolism and enzyme reactions speed up. Diathermy is used for relieving muscle tension and as a pretreatment for physical therapy.

12.11.3 Hyperthermia

Microwave hyperthermia is used to treat cancer. A tissue containing a tumor is heated without destroying the healthy cells surrounding the tumor. This is possible because at 41°C to 45°C the cancer cells are destroyed more readily than the healthy cells [22]. Because the power density is high (1 W/cm2 ) and the skin absorbs well, a burn may arise in the skin on top of the tumor. To be able to focus the energy into the tumor, microwave frequencies have to be used.

12.12 Electronic Warfare

Radar and wireless communication have many important military applications. There are also many other ways to utilize radio engineering techniques or knowledge for military purposes: jamming enemy communication and radar, stealth technology, signal intelligence, and so on. These applications go under the name electronic warfare (EW). Electronic warfare can be defined as military action involving the use of electromagnetic energy to determine, exploit, reduce, or prevent the use of the electromagnetic spectrum by the

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enemy, and as action that retains effective use of this spectrum, but sometimes also as military action where an electromagnetic weapon is used against personnel. EW is divided into three categories:

•Electronic support (ES), formerly EW support measures (ESM);

•Electronic attack (EA), formerly electronic countermeasures (ECM);

•Electronic protection (EP), formerly electronic counter-countermeasures

(ECCM).

12.12.1 ES

ES is defined as actions taken to search for, intercept, locate, record, and analyze radiated electromagnetic energy for the purpose of exploiting it in support of military operations, especially for the purpose of immediate threat recognition. ES involves signal intelligence (SIGINT), which is divided into electronics intelligence (ELINT) and communications intelligence (COMINT). Detection, identification, evaluation, and location of foreign electromagnetic radiation from radar, communication radios, and so on are called electronic reconnaissance.

In ELINT wideband monitoring receivers covering, typically, frequency ranges from 20 to 500 MHz and from 0.5 to 40 GHz, as well as omnidirectional or rotating antennas are used to detect the presence of a radar signal. A high-gain steerable antenna is used to find the rough direction of the signal source. The signal is then analyzed and characterized using a sophisticated channelized receiver and analyzer, and compared to known radar signals in a signal library. Direction-finding antenna systems consisting of an array of antenna elements and utilizing, for example, interferometric or time difference of arrival (TDOA) techniques, are used at several receiving sites in order to locate the transmitting radar. Similarly, in COMINT communication signals in the HF, VHF, and UHF ranges are characterized and their sources located.

12.12.2 EA

EA is a division of EW involving actions taken to prevent or reduce an enemy’s effective use of the electromagnetic spectrum by either passive or active means. EA involves, for example, radar or communication link jamming, high-power electromagnetic pulse (EMP), stealth technology, and the use of chaff to make fake radar targets.

Active EA involves jamming, high-power microwave weapons, and EMP. Jamming is deliberate radiation of wideband RF noise for the purpose

of preventing or reducing an enemy’s effective use of radar or communication link. The high-power microwave weapon or electromagnetic weapon is a class of directed energy weapons (DEW), and it is any device that can produce a directed microwave field of such intensity that targeted items of electronic equipment experience damage. EMP is often related to the electromagnetic radiation from a nuclear explosion, but it may also be caused by non-nuclear means, such as radio equipment; the resulting strong electric and magnetic fields may damage electronic systems.

Passive EA includes the use of chaff or decoys and stealth technology. Chaff is highly microwave-reflective material, such as sections of thin metallic stripes or wires with a resonant length, dispensed over a large volume to present a false radar target in order to protect a battleship or aircraft. A decoy is a passive dummy target or a radio repeater that appears as a false radar target. Stealth technology is used to reduce the radar cross section of an aircraft, ship, or ground facility by shaping the object and covering its surfaces with layers of absorbing composite materials.

12.12.3 EP

This division of EW involves actions taken to ensure effective use of the electromagnetic spectrum despite the enemy’s use of electronic warfare by protecting equipment and facilities. EP involves technologies, such as shielding, that make electronic equipment robust against jamming, electromagnetic weapons, and EMP.

References

[1]Sehm, T., A. Lehto, and A. Ra¨isa¨nen, ‘‘A High-Gain 58-GHz Box-Horn Array Antenna with Suppressed Grating Lobes,’’ IEEE Trans. on Antennas and Propagation, Vol. 47, No. 7, 1999, pp. 1125–1130.

[2]Prasad, R., CDMA for Wireless Personal Communications, Norwood, MA: Artech House, 1996.

[3]Gibson, J. D., (ed.), The Mobile Communications Handbook, New York: IEEE Press, 1996.

[4]Lee, W. C. Y., Mobile Communications Engineering: Theory and Applications, 2nd ed., New York: McGraw-Hill, 1998.

[5]Rappaport, T. S., Wireless Communications, Principles, and Practice, Upper Saddle River, NJ: Prentice Hall, 1996.

[6]Holma, H., and A. Toskala, (eds.), WCDMA for UMTS, Radio Access for Third Generation Mobile Communications, Chichester, England: John Wiley & Sons, 2000.

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[7]Kayton, M., (ed.), Navigation: Land, Sea, Air, & Space, New York: IEEE Press, 1990.

[8]Skolnik, M. I., Introduction to Radar Systems, 2nd ed., New York: McGraw-Hill, 1981.

[9]Ulaby, F. T., R. K. Moore, and A. K. Fung, Microwave Remote Sensing, Vol. I, Microwave Remote Sensing Fundamentals and Radiometry, Reading, MA: AddisonWesley, 1981.

[10]Ulaby, F. T., R. K. Moore, and A. K. Fung, Microwave Remote Sensing, Vol. II, Radar Remote Sensing and Surface Scattering and Emission Theory, Reading, MA: AddisonWesley, 1982.

[11]Ulaby, F. T., R. K. Moore, and A. K. Fung, Microwave Remote Sensing, Vol. III, From Theory to Applications, Dedham, MA: Artech House, 1986.

[12]Kraus, J. D., Radio Astronomy, 2nd ed., Powell, OH: Cygnus-Quasar Books, 1986.

[13]Kraus, J. D., and R. J. Marhefka, Antennas for All Applications, 3rd ed., New York: McGraw-Hill, 2002.

[14]Payne, J. M., ‘‘Millimeter and Submillimeter Wavelength Radio Astronomy,’’ Proc. of the IEEE, Vol. 77, No. 7, 1989, pp. 993–1017.

[15]Phillips, T. G., and J. Keene, ‘‘Submillimeter Astronomy,’’ Proc. of the IEEE, Vol. 80, No. 11, 1992, pp. 1662–1678.

[16]Nyfors, E., and P. Vainikainen, Industrial Microwave Sensors, Norwood, MA: Artech House, 1989.

[17]Fischer, M., P. Vainikainen, and E. Nyfors, ‘‘Dual-Mode Stripline Resonator Array for Fast Error Compensated Moisture Mapping of Paper Web,’’ 1990 IEEE MTT-S International Microwave Symposium Digest, 1990, pp. 1133–1136.

[18]Fischer, M., P. Vainikainen, and E. Nyfors, ‘‘Design Aspects of Stripline Resonator Sensors for Industrial Applications,’’ Journal of Microwave Power and Electromagnetic Energy, Vol. 30, No. 4, 1995, pp. 246–257.

[19]Toropainen, A. P., ‘‘New Method for Measuring Properties of Nonhomogeneous Materials by a Two-Polarization Forward-Scattering Measurement,’’ IEEE Trans. on Microwave Theory and Techniques, Vol. 41, No. 12, 1993, pp. 2081–2086.

[20]Edrich, J., ‘‘Centimeterand Millimeter-Wave Thermography—A Survey on Tumor Detection,’’ The Journal of Microwave Power, Vol. 14, No. 2, 1979, pp. 95–103.

[21]Myers, P. C., N. L. Sadowsky, and A. H. Barrett, ‘‘Microwave Thermography: Principles, Methods and Clinical Applications,’’ The Journal of Microwave Power, Vol. 14, No. 2, 1979, pp. 105–113.

[22]Storm, F., ‘‘Hyperthermia,’’ Proc. of the IEEE MTT-S International Microwave Symposium, 1981, pp. 474–475.

microwave oven may expose its user to a high RF radiation dose. However, we do not know any incidence where a person has been permanently harmed by leakage radiation from a microwave oven. When an oven is mechanically damaged, however, its leakage radiation should be checked before the oven is used.

We consider harmless all the appliances that have maximum power below 100 mW. Table 13.1 lists typical sources of RF radiation.

Most countries use both national and international safety standards. The standards set limits on RF radiation power density or field strengths to which people in the general public and specific personnel dealing with strong RF radiation sources may be exposed.

In 1998 the International Commission on Non-Ionizing Radiation Protection (ICNIRP) developed new guidelines for limiting exposure to timevarying electric, magnetic, and electromagnetic fields [6], based on which

Table 13.1

Sources of RF Radiation in Finland

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the Commission of the European Union in 1999 issued a directive concerning limiting acceptable exposure to electromagnetic fields to between 0 Hz and 300 GHz. Table 13.2 provides these limits. It is worth noticing that, because of the human body’s resonance, the frequency range from 10 to 400 MHz is considered more harmful than other frequency ranges. In Finland, the Radiation and Nuclear Safety Authority supervises the safety of RF equipment.

Table 13.2

Limits of Exposure to RF Radiation as Electric and Magnetic Field Strengths and as Equivalent Power Densities (Frequency f Must Be Introduced in Megahertz)

Source: [6].

References

[1]Johnson, C., and A. Guy, ‘‘Nonionizing Electromagnetic Wave Effects in Biological Materials and Systems,’’ Proc. of the IEEE, Vol. 60, No. 6, 1972, pp. 692–718.

[2]Durney, C., ‘‘Electromagnetic Dosimetry for Models of Humans and Animals: A Review of Theoretical and Numerical Techniques,’’ Proc. of the IEEE, Vol. 68, No. 1, 1980, pp. 33–39.

[3]Gandhi, O., ‘‘State of the Knowledge for Electromagnetic Absorbed Dose in Man and Animals,’’ Proc. of the IEEE, Vol. 68, No. 1, 1980, pp. 24–32.

[4]Hagmann, M. J., O. P. Gandhi, and C. H. Durney, ‘‘Numerical Calculation of Electromagnetic Energy Deposition for a Realistic Model of Man,’’ IEEE Trans. on Microwave Theory and Techniques, Vol. MTT-27, No. 9, 1979, pp. 804–809.

[5]Jokela, K., et al., ‘‘Radiation Safety of Handheld Mobile Phones and Base Stations,’’ Radiation and Nuclear Safety Authority of Finland, STUK-A161, 1999.

[6]International Commission on Non-Ionizing Radiation Protection (ICNIRP), ‘‘Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (Up to 300 GHz),’’ Health Physics, Vol. 74, No. 4, 1998, pp. 494–522.

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=2A = ux=2A x + uy= 2A y + uz= 2A z

In cylindrical coordinate system

= × A = ur Sr1 ∂∂Afz − ∂∂Azf D+ uf S∂∂Azr − ∂∂Arz D+ uz r1 F∂( r∂Ar f ) − ∂∂Afr G

+ urf F∂∂r (rA u ) − ∂∂Aur G

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Conductivity of Some Materials at 208C

Dielectric Constant (Relative Permittivity) of Some Materials (at 10 GHz If Not Otherwise Stated)