pulsed) into microwaves. This technology is known as pulsed power. In this way, the transmitted pulse of RF radiation is kept to a defined and usually very short duration. Hybrid mixers, fed by a waveform generator and an exciter for a complex but coherent waveform. This waveform can be generated by low power/low-voltage input signals. In this case the radar transmitter must be a power-amplifier, e.g., a klystron or a solid state transmitter. In this way, the transmitted pulse is intrapulse-modulated and the radar receiver must use pulse compression techniques. Coolant Coherent microwave amplifiers operating above 1,000 watts microwave output, like travelling wave tubes and klystrons, require liquid coolant. The electron beam must contain 5 to 10 times more power than the microwave output, which can produce enough heat to generate plasma. This plasma flows from the collector toward the cathode. The same magnetic focusing that guides the electron beam forces the plasma into the path of the electron beam but flowing in the opposite direction. This introduces FM modulation which degrades Doppler performance. To prevent this, liquid coolant with minimum pressure and flow rate is required, and deionized water is normally used in most high power surface radar systems that use Doppler processing. Coolanol (silicate ester) was used in several military radars in the 1970s. However, it is hygroscopic, leading to hydrolysis and formation of highly flammable alcohol. The loss of a U.S. Navy aircraft in 1978 was attributed to a silicate ester fire. Coolanol is also expensive and toxic. The U.S. Navy has instituted a program named Pollution Prevention (P2) to eliminate or reduce the volume and toxicity of waste, air emissions, and effluent discharges. Because of this, Coolanol is used less often today. Regulations Radar (also: RADAR) is defined by article 1.100 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR) as: Configurations Radar come in a variety of configurations in the emitter, the receiver, the antenna, wavelength, scan strategies, etc. Bistatic radar Continuous-wave radar Doppler radar Fm-cw radar Monopulse radar Passive radar Planar array radar Pulse-doppler Synthetic-aperture radar Synthetically thinned aperture radar Over-the-horizon radar with Chirp transmitter See also Terrain-following radar Radar imaging Radar navigation Inverse-square law Wave radar Radar signal characteristics Pulse doppler radar Acronyms and abbreviations in avionics Definitions Amplitude-comparison monopulse Constant false alarm rate Sensitivity time control Application Proximity fuze Hardware Cavity magnetron Crossed-field amplifier Gallium arsenide Klystron Omniview technology Radar engineering