The wavelengths for microwave frequencies, which is than infrared energy.

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The name given to microwave signals, because of their inherently high frequencies, have short wavelengths. “Microwave” waves

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Each frequency is divided in half with the lower half identified as the low band and the upper half as narrow band.

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Communications system used to carry information for relatively short distances such as between cities with the same state.

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Microwave systems that is used to carry information for relatively long distances, such as interstate and backbone route applications.

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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.

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Advantages of Microwave Radio:

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Disadvantages of Microwave Radio:

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Propagates signals outside the Earth’s atmosphere and are capable of carrying signals much farther while utilizing fewer transmitters and receivers.

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It is used in microwave radio systems rather than amplitude modulation because AM signals are more sensitive to amplitude nonlinearities inherent in wideband microwave amplifiers.

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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.

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The composite signal that modulates the FM carrier and may comprise one or more of the following: 1Frequency-division multiplexed voiceband channels

2Time-division-multiplexed voice-band channels

3 Broadcast-quality composite video or picture phone Wideband data

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It provides an artificial boost in amplitude to the higher baseband frequencies.

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Frequency modulation index used in the FM deviator. Typically, modulation indices are kept between 0.5 and 1.

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FM signal that is produces at the output of the deviator with a low-index frequency modulation.

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A receiver and a transmitter placed back to back or in tandem with the system.

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It receives a signal, amplifies and reshapes it, and then retransmit the signal to the next repeater or terminal station down line from it. Types of Microwave repeaters:  IF  Baseband  RF

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The received RF carrier is down-converted to an IF frequency, amplified, reshaped, up-converted to an RF frequency, and then retransmitted.

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Generally less than 9 MHz.

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The range id 60 MHz to 80MHz.

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Another name for a Local oscillator, is considerably lower in frequency than either the received or the transmitted radio frequencies.

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Transmission used by microwave systems wherein a direct signal path must exist between the transmit receive antennas.

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A temporary reduction in signal strength which last in milliseconds for several hours or even days.

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It suggests that there is more than one transmission path or method of transmission available a transmitter and a receiver.

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It is simply modulating two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination.

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The output of a transmitter is fed to two or more antennas that are physically separated by an appreciable number of wavelengths.

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A single RF carrier is propagated with two different electromagnetic polarizations. It is generally used in conjunction with space diversity.

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Another form of Hybrid diversity and undoubtly provides the most reliable transmission but most expensive. It combines frequency, space, polarization and receiver diversity into one system.

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A specialized form of diversity that consist of a standard frequency diversity path where the two transmitter/ receiver pairs at one end of the path are separated from each other and connected to different antennas that are vertically separated as in space diversity.

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Alternate facilities temporarily made to avoid a service interruption during periods of deep fades or equipment failures.

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types of protection switching arrangements:

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Each working radio channel has a dedicated backup or spare channel.

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A single backup channel is made available to as many as 11 working channels.

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In hotstandby protection, it splits the signal power and directs it to the working and the spare (standby) microwave channels simultaneously.

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It has two working channels, one spare channel, and an auxiliary channel.

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A low-capacity low-power microwave radio that is designed to be used for a maintenance channel only.

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It is where the number of repeater stations between protection switches depends.

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Points in the system where baseband signals either originate or terminate. four major sections:  baseband  wireline entrance link (WLEL)  FM-IF  RF sections

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Points in a system where baseband signals may be reconfigured or where RF carriers are simply “repeated” or amplified.

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It must be capable of amplifying very high frequencies and passing very wide bandwidth signals for microwave radios. devices used in microwaveamplifiers:  Klystron Tubes  Traveling-wave tubes (TWTs)  IMPATT (Impact avalanche and transit time)

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It provides the RF carrier input to the up-converter. It is called as microwave generator rather than an oscillator because it is difficult to construct a stable circuit that will oscillate in the gigahertz range.

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It operates in the range 5 MHz to 25 MHz, used to provide a base frequency that is multiplied up to the desired RF carrier frequency.

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A unidirectional device often made from ferrite material. It used in conjunction with a channel combining network to prevent the output of one transmitter from interfering with the output of another transmitter.

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It occurs only when three stations are placed in a geographical straight line in the system.

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It prevents the power that “leaks” out the back and sides of a transmit antenna from interfering with the signal entering the input of a nearby receive antenna.

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The signal entering the input of a nearby receive antenna.

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The line-of-sight directly between the transmit and receive antenna. Also called as the Direct Wave.

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It consists of the electric and magnetic fields associated with the currents induced in earth’s surface.

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The portion of the transmit signal that is returned back to Earth’s surface by the ionized layers of earth’s atmosphere.

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The loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects.

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The reduction in signal strength at the input to a receiver.

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The difference between the nominal output power of a transmitter and the minimum input power to a receiver necessary to achieve satisfactory performance.

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ometimes called as Link Margin, is essentially a “fudge Factor” included in system gain equations that considers the non ideal and less predictable characteristics of radio wave propagation and terrain sensitivity.

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He described ways of calculating outage time due to fading on a non diversity path as a function of terrain, climate, path length, and fade margin, in April 1969.

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The ratio of the wideband “carrier” to the wideband noise power.

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A ratio of input signal-to-noise ratio to output signal to noise ratio.

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The noise factor stated in dB and is a parameter commonly used to indicate the quality of a receiver.

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the same signal is received by the same microwave radio coming from different modes or paths. affects the carrier in a more destructive rather than constructive way

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