MICROWAVE RADIO COMMUNICATIONS AND SYSTEM GAIN (c22 Tomasi) CHAPTER 24
MICROWAVE RADIO COMMUNICATIONS AND SYSTEM GAIN
1)Electromagnetic waves with frequencies that range from approximately 500 MHz to 300 GHz or more. Microwaves
2)The wavelengths for microwave frequencies, which is than infrared energy. 1 cm and 60 cm slightly longer
3)The name given to microwave signals, because of their inherently high frequencies, have short wavelengths. “Microwave” waves
4)Each frequency is divided in half with the lower half identified as the low band and the upper half as narrow band. Full-Duplex (Two-way)
5)Communications system used to carry information for relatively short distances such as between cities with the same state. Short Haul
6)Microwave systems that is used to carry information for relatively long distances, such as interstate and backbone route applications. Long Haul
7)It propagate signals through Earth’s atmosphere between transmitters and receivers often located on top of tower spaced about 15 miles to 30 miles apart. Microwave Radios
Advantages of Microwave Radio:
Radio systems do not require a right-of way acquisition between stations. Each station requires the purchase or lease ofonly a small area of land. Because of their high operating frequencies, microwave radio systems can carry large quantities of information. High frequencies mean short wavelengths, which require relatively small antennas. Radio signals are more easily propagated around physical obstacles such as water and high mountains Fewer repeaters are necessary for amplification.
Distances between switching centers are less.
Underground facilities are minimized.
Minimum delays are introduced.
Minimal crosstalk exists between voice channels.
Increased reliability and less maintenance are important factors. Disadvantages of Microwave Radio:
It is more difficult to analyze and design circuits at microwave frequencies. Measuring techniques are more difficult to perfect and implement at microwave frequencies. It is difficult to implement conventional circuit components at microwave frequencies. Transient time is more critical at microwave frequencies. It is often necessary to use specialized components for microwave frequencies. Microwave frequencies propagate in a straight line, which limits their use to line-of-sight applications. 8)Propagates signals outside the Earth’s atmosphere and are capable of carrying signals much farther while utilizing fewer transmitters and receivers. Satellite Systems
9)It is used in microwave radio systems rather than amplitude modulation because AM signals are more sensitive to amplitude nonlinearities inherent in wide-band microwave amplifiers. Frequency Modulation
10)Major factor when designing FM Radio systems. It is caused by repeater amplitude nonlinearity in AM, while in FM, it is caused by transmission gain and delay distortion. Intermodulation Noise
11)The composite signal that modulates the FM carrier and may comprise one or more of the following: Frequency-division multiplexed voice-band channels
Time-division-multiplexed voice-band channels
Broadcast-quality composite video or picture phone
12)It provides an artificial boost in amplitude to the higher baseband frequencies. Preemphasis Network
13)Frequency modulation index used in the FM deviator. Typically, modulation indices are kept between 0.5 and 1. Low-Index
14)FM signal that is produces at the output of the deviator with a low-index frequency modulation. Narrowband FM
15)A receiver and a transmitter placed back to back or in tandem with the system. Microwave Repeaters
16)It receives a signal, amplifies and reshapes it, and then retransmit the signal to the next repeater or terminal station down line from it. Repeater Station
Types of Microwave repeaters:
17)The received RF carrier is down-converted to an IF frequency, amplified,...
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