Principles of electronic communication systems / Louis E. Frenzel Jr. —Fourth edition. pages cm. Includes index. ISBN (alk. paper) — ISBN . Principles-of-Electronic-Communication-Systems-4th-Edition-Frenzel-Test-Bank. pdf Apply Chapter: 02 Electronic Fundamentals for Communications Difficulty: . Principles of Electronic Communication Systems 4th Edition Frenzel Solutions louis frenzel solution manual pdf principles of electronic communication.
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Principles of Electronic Communication Systems 4th Ed __ Louis E Frenzel. pdf - Free download as PDF File .pdf), Text File .txt) or read online for free. Principles of Electronic Communication Systems by Louis E. Frenzel, , available at Book Depository with free delivery. 1. Principles of Electronic. Communication Systems. Third Edition. Louis E. Frenzel, Jr. Basic Principles of Amplitude Modulation. ▫ Amplitude.
Resonance in a series tuned circuit is the point at which XL equals XC. The bandwidth of a resonant circuit defines its selectivity. The bandwidth of a circuit is directly proportional to Q.
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A frequency-selective circuit designed to pass some frequencies and reject others is a n A. The signal attenuation in the passband of a filter is called A. Which of the following is also known as a notch filter? The rate of change of amplitude with frequency in a filter is the A.
Butterworth B. Chebyshev C. Cauer D. Bessel Blooms: 2. Which of the following is not an advantage of an active filter? Which of the following filter is used to supply signals on exact frequencies with good stability?
RC low-pass B. Bessel C. LC notch Blooms: 2. Which of the following filter is very small and inexpensive and widely used in communication transmitters and receivers? Bessel B. Butterworth C. The primary advantage of SCFs is that they provide a way to make tuned or selective circuits in an IC without the use of discrete inductors, capacitors, or resistors.
Blooms: 2. One characteristic of the commutating filter is that it is sensitive to the harmonics of the center frequency for which it is designed. Blooms: 1. A non-sine wave approach used to determine the characteristics and performance of any communication circuit or system is Fourier analysis.
Bit rate Separate binary data sources may modulate subcarriers on different frequencies. The subcarriers are summed, and the resulting composite transmitted as an FDM signal.
Chapter 11 Answers to Questions 1. The telegraph. Morse code. You cannot distinguish between uppercase and lowercase letters with Morse code. Baudot code. To ring a bell, transmit the BEL code Serial and parallel. Start and stop bits. Baud rate. A symbol is any change in the transmitted signal during a bit interval such as amplitude, frequency, or phase.
Each symbol can represent two or more bit combinations. Synchronous transmission is faster because start and stop bits are not used on each transmitted byte; the total number of bits to be transmitted in a given time is thus less. The message words are sent serially in a fixed format of a specific number of words in a block.
A preamble precedes the block, and a postamble error code ends the transmission.
Space 0 and mark 1. Two or more successive binary 0 or 1s. Bipolar RZ and Manchester. No average DC buildup on the transmission line. Manchester, biphase. High speeds are obtained by using a small modulation index and prefiltering the binary signal. Number of coding levels and the transmission speed baud. Higher bps data rate. UART, scrambler, modulator, equalizer, line interface, adaptive receive equalizer, demodulator, descrambler, microcontroller. Modems are needed to convert digital signals to analog signals and vice versa to make them compatible with the standard voice-grade telephone system.
Modems are used with any computer that must communicate with another computer over long distances using the telephone system. A scrambler ensures that long strings of binary 0s or 1s are broken up into replacement codes with few successive 0 or 1 bits. A carrier recovery circuit, usually a phase-locked loop. Differential BPSK. XNOR gate and a 1-bit delay flip-flop. AM and PSK. Trellis code modulation is a form of QAM, used at data rates of bps or above, that incorporates a coding scheme that makes error detection and correction faster and easier.
It is used because at faster data rates over the telephone system the bit error rate is much higher than at rates less than bps. The process of modifying an intelligence signal in such a way that its spectrum is spread over a wide frequency range rather than being confined to a narrow singlechannel bandwidth. Frequency-hopping and direct-sequence SS. A frequency synthesizer. A pseudorandom sequence generator.
Random background noise. The identifying characteristic of a spread spectrum signal is the unique pseudorandom code being used. Dwell time. A shift register with XOR feedback or a specially programmed microcomputer. The PSN signal is a unique binary code sequence used for each station operating over a shared spectrum. It allows one station to be distinguished from another. Synchronizing the receiver to the desired signal.
Data security and resistance to jamming or interference from other signals. Cellular telephone, satellite, and radar. Voice signals are converted to serial digital data before they are sent to the SS equipment. Code division multiple access CDMA. Redundancy, special codes, encoding methods, parity, block-check character, cyclical redundancy check. Repeat the transmission until it is correctly received.
Reed Solomon. Bit error rate BER. Parity bit. Block-check code, or BCC. The corresponding bits in each word are added without carry to form the blockcheck character. Vertical redundancy check. XOR gate. Longitudinal redundancy check. A block of data is treated as if it were one very large binary number. It is divided by a smaller binary number called the generating function.
The resulting quotient is abandoned, and the remainder is retained. The remainder is the CRC. A shift register with feedback through XOR gates. A CRC is generated at the receiver using the received data block. It is then compared to the received CRC. If the two match, the data is correct. The sum is zero , indicating no errors in a bit position. Trellis, Viterbi, turbo recursive codes. The last field in a protocol frame is usually a block check sequence or CRC for error detection.
A CRC word. Interoperability refers to the ability of one type of equipment to operate compatibly and communicate with the equipment of another manufacturer. Use protocols based on the OSI layers. Applications, presentation, session, transport, network, data link, physical. Physical, data link, network, and applications. A temperature sensor such as a thermistor or resistive temperature device RTD monitors the temperature. This signal is serialized and packaged into a protocol packet by a microprocessor.
It is then sent to modulate a low-power radio transmitter with antenna. The receiving antenna picks up the signal and recovers the original digital signal, which is then put back into parallel form and sent to an interface on the computer. A program in the computer reads the data from the interface and stores it in memory. The program takes the data word and processes it so that it is displayed as the correct temperature on the video screen of the computer.
Cellular telephone. Many phones could share a common band simultaneously. The conversations would be secure and private. Remote controls for TV sets, garage doors, and car doors, radio-controlled airplanes or cars—all via AC power lines.
Spread spectrum and OFDM are spectrally efficient because the disperse the very high data rate signals over a broad spectrum that is typically less spectrum than other methods use for the same data rate. Chapter 12 Answers to Questions 1. To permit individual PCs to communicate, share peripherals, and exchange software.
The MAN is smaller. A cable TV network or a large company. About users per LAN. Star, ring, bus. Ring and bus. The telephone system is a WAN.
The fiber optic backbones of the Internet are WANs. Fiber optic cable. A SAN is a storage area network, a system made up of a redundant array of independent disks RAID or just a bunch of disks JBOD forming a storage facility for company or organization that can be accessed by servers and users via a high speed network. Wireless is the normal medium used in a PAN.
The main advantage of a mesh network is its reliability because of one node in the network is disabled or out of range an alternate path can be formed or taken to ensure communications. Coaxial cable is self-shielding and thus less subject to noise pickup. AWG 22, 24, Network interface card. A transceiver or repeater. This reduces the load on the bus and collisions, thereby greatly improving transmission speed. A hub is a centralized connection point for attaching individual PCs to the network bus.
PoE means power over Ethernet. This is a variation of the Ethernet standard that permits DC power to be distributed over the twisted pair cable that carries the high speed data. Star in the newer systems. It is used because clock recovery is easy. Twisted pair and fiber optic cable. Ethernet nodes complete contend for the bus. If one node transmits, no others can transmit until the first transmission is complete. If two stations try to transmit at the same time, a collision occurs and both stations stop sending.
They wait a random time and start. The one waiting the shorter time captures the bus first. Layers 1 and 2. Maximum range fiber optic cable 1 Gbps: Backbones connecting large LANs or small metro area networks.
Makes clock recovery easier and permits implementation of error detection and correction. Passive optical networks PON. Unshielded twisted pair UTP. A back plane is a printed circuit board that interconnects connectors into which other boards are plugged. A router is an example. Four parallel lanes of 10 Gbps paths are combined to produce 40 Gbps.
Ten 10 Gbps lanes are combined to produce a Gbps path. The line rate of a high speed path is different from the actual raw data rate because of the extra overhead bits of forward error correction codes added for reliability. Carrier Ethernet software. A data center is a facility with multiple servers, switches, and routers that form networks and facilitate network communications.
Factory automation, in which multiple computers controlling robots, machine tools, computer vision systems, and other equipment are usually networked. Number of nodes on the network, the amount of traffic or activity on the LAN, and the access method used.
It takes longer to transmit the two extra bits and that slows the over transmission. Yes, a single fiber can support 40 Gbps or Gbps over shorter distances using NRZ or over longer distances using multiplexing or modulation methods.
Chapter 13 Answers to Questions 1. Coaxial cable and open wire line. Coaxial cable is more widely used. Twin lead. PL, SO N-type connector. F connector. LC low-pass filter. Surge impedance. Velocity factor is the ratio of the speed of a signal in a transmission line to the speed of light radio waves in free space. Since the speed of a signal in a transmission line is less than that in free space, the electrical wavelength of a transmission line is less than a wavelength or fraction thereof in free space.
The cutoff frequency decreases with length. Constant value of voltage and current.
All the power transmitted down the line from the generator is not absorbed by the load; therefore, some of the unabsorbed power is reflected back up the line toward the generator. The transmitted power at the antenna is less than that applied to the transmission line by the transmitter because of cable attenuation as well as the loss of power due to reflection of power. Open and shorted at the end.
Resonant line. Length does not affect SWR. Use an open quarter-wave or shorted half-wave line. They act as an inductive or capacitive reactance. One wavelength. A single point at the center of the chart. An open quarter wave or shorted half-wavelength line acts like a series tuned or resonant LC circuit. A short quarter-wave or open half-wave line acts like a parallel resonant LC circuit. Upper UHF and microwave.
Microstrip is a copper line on the insulating surface of a dielectric backed up by a ground plane on the other side of the insulating surface. Stripline is a copper conductor inside an insulating dielectric sandwiched between two.
Stripline is preferred because it does not radiate, but it is harder to make. Refer to text Fig. Therefore, a MHz square wave, which is made up of a MHz fundamental sine wave and all odd harmonics, will be attenuated and distorted. The third, fifth, seventh, and higher harmonics will be greatly attenuated. The output of the coaxial. Some of the harmonic energy will still be present but in lower levels, so that the output wave will bear some resemblance to a square wave but will be highly filtered until it is almost a sine wave.
A shorted half wavelength of transmission line acts like a series resonant circuit. Connecting this transmission line across the receiver front end will cause it to short out the interfering frequency of One half wave at Chapter 14 Answers to Questions 1. A radio wave is the combination of electric and magnetic fields varying at the signal frequency.
These equations state that an electric field varying over time sets up a magnetic field which, in turn, sets up an electric field, both of which are propagated in space without energy loss.
The electric and magnetic fields set up by the antenna are at right angles to one another, and both are at a right angle to the direction of propagation. The orientation of the electric field determines the polarization—vertical, horizontal, or circular. Antenna reciprocity means that an antenna will receive as well as transmit at the operating frequency. Hertz or dipole. One-half wavelength. A transmission line connects the antenna to the receiver or transmitter. The most common transmission line is coaxial cable.
Height of the antenna above ground and length. Antenna bandwidth is a function of antenna conductor size; the larger the conductor the lower the Q and the wider the bandwidth. Signal strength in relative power or decibels over a given azimuth. Antenna gain is the apparent signal strength increase over an isotropic antenna or dipole caused by the directivity of the antenna that comes from concentrating or focusing the signal into narrow beams.
An isotropic radiator is an imaginary point source of electromagnetic energy that radiates equally in all directions. Antenna gain is expressed as a power ratio or in decibels referenced to an isotropic source or a dipole.
Effective radiated power. This is the apparent power radiated by a directional antenna which is a product of the power applied to the antenna and the antenna gain. A folded dipole is a continuous-loop conductor formed into a half-wavelength center-fed dipole.
Marconi and ground plane. A circle. A counterpoise array of conductors. An antenna that transmits essentially in one direction or over a narrow range of azimuth. A directional antenna amplifies because it focuses the radiated energy into a narrow beam or beams. A directional antenna with gain usually consists of at least two separate conductors that together help direct or focus the radiation.
Antennas longer than one-half wavelength also exhibit gain and directivity. Driven and parasitic. Driven element, reflector, and director. Reflector and director. Theoretically there is no upper limit, but the number is usually limited by the size of the antenna at the operating frequency and any resulting physical restrictions. The desired beamwidth, gain, and front-to-back ratio are also factors. Number or directors and their spacing.
Broadside, collinear, end fire. Log periodic. Very wide bandwidth.
To achieve low SWR and maximum power transfer to the antenna. Toroid balun. Q section. An antenna tuner consists of one or more variable capacitors and inductors that may be connected in a variety of configurations to match transmitter to the load, reduce SWR, and increase transmitted power. Tune for low SWR and maximum output power.
Radio signals are reflected by any conductive surface. The better the conductor, the greater the amount of reflection and the lesser the amount of signal absorbed by the reflecting surface. Theoretically no, but in the real world vertically polarized waves will induce a small signal into a horizontal antenna.
Circular polarization is the orientation of a radio wave so that its electric and magnetic fields continuously rotate in a circle. Yes, but reception will not be optimum. Refraction is the bending of radio waves caused by the waves passing from the atmosphere into differently charged layers of the ionosphere.
Diffraction is the bending of light or radio waves around the edges of objects blocking the waves. Diffraction is beneficial in that it permits communications when obstacles might prevent propagation. Ground, sky, and space waves. Ground wave or surface wave. The waves must be vertically polarized. Sky wave. The ionosphere is an area 30 to mi above the earth which has been highly ionized by the sun, making it a form of conducting medium that affects radio waves.
The F layers. It reflects or bends them in such a way that it looks as if the waves have been reflected. Multiple-skip transmission; the wave refracted back to earth is reflected by the earth back to the ionosphere and again refracted back to earth for another reflection, and so on. The angle of entry into the ionosphere and the frequency of the wave. A space or direct wave. Use a repeater or a chain of retransmitting repeaters. A repeater is usually located at a high point to permit maximum receiving and transmitting distances.
It consists of a receiver that picks up signals on one frequency, demodulates them, and remodulates a high-power transmitter on another frequency for retransmission. Multipath signal reflections. Rayleigh fading. It requires multiple sets of transceivers and multiple frequencies.
Spatial diversity uses two or more antennas spaced as far apart as practical so that each receives a slightly different version of the signal. The best signal is selected or the signals are combined.
Experiments Manual for Principles of Electronic Communication Systems
Wideband signals. The antenna made with tubing has a wider bandwidth. The center conductor attaches at the base of the vertical antenna element; the shield braid is connected to a good earth ground, radials, or a counterpoise array of conductors. The quarter-wave vertical and dipole perform in exactly the same way.
Polarization is different, but gain is the same. The impedance is Add an inductive loading coil at the base or in the center of the vertical radiator. Add a capacitor in series with the antenna, or add a capacitive top hat.
Since the transmitter cannot be accessed or changed in any way, some improvements can be made at the receiver: Chapter 15 Answers to Questions 1. The domain is an Internet service provider. The symbol designates an email address. Dial up modem via the phone line, a DSL modem via the phone line or a cable modem via a cable TV system. Internet service provider ISP. A browser. Optical transport network OTN. ATM switches.
Ring topology. OC, 40 Gbps Maximum OTN payload is 15, octets. IP destination address. The router stores information about connected routers and networks in routing tables. Line cards. Switch matrix. The net data rate is lower than the line rate because of the added FEC overhead. Internet backbone. In packet switching systems, each packet is handled by a router and can be transmitted over one of usually several paths depending upon the traffic being handled.
Packets are transmitted from router to router until the destination is reached. Transmission control protocol TCP. Internet protocol IP. TCP is not use during packet transmission that is handled by the Internet protocol. Dotted decimal. Workstations PCs , routers, and switches. Class C, network ID is A mask is a sequence of bits used by a router to determine if a packet is destined to that router.
Logical AND. A subnet is a smaller segment of a larger network defined to more efficiently route packets in very large networks. Direct attached storage DAS. Small computer systems interface SCSI , skuzzy. SAN is a complete separate network that connects to servers and PCs via interface cards.
Fibre Channel FC. Fiber optical cable. Host bus adapter HBA. Switch fabric. Ethernet and twisted pair cable. Viruses, spam, spyware, and denial-of-service DoS attacks. Worms replicate themselves. Spyware monitors a users application of the Internet then sends relevant ads and other information.
Special security software is available to minimize viruses, spam, spyware, and DoS attacks. Input is plaintext and output is ciphertext. A key is a long unique binary bit pattern used in encryption and decryption. With SKE, sharing or distributing the key is difficult and prone to detection.
PKE uses two keys one public and the other private. The public key is readily shared and distributed and is usually sent by the receiving party to the transmitting party.
The private key is kept secret. Both are used in encryption and decryption. Diffie-Hellman and elliptic curve cryptosystem ECC. Use of very long keys. Hash functions detect if a message has been changed in any way during transmission. A digital signature is a form of authentication that proves who you say you are.
Secure socket layer SSL. A firewall is a piece of software used on a network to screen all incoming data to ensure it conforms to what the network is allowed to admit. A virtual private network VPN is a software technique that is used to create a private secure connection between computers or networks over an unsecured link such as the Internet.
IPsec and SSL. Zero in all cases. Local area networks, metro networks, and even WANs. Highly directive antennas, limited RF power to restrict range, rules to restrict the transmission of highly sensitive information. Chapter 16 Answers to Questions 1.
Greater spectrum space for more services, signals, or stations, and wider bandwidth for video, data, or other information signals requiring a larger spectrum. Main disadvantages are shorter ranges and more complex and costly components. Standard components do not work well, if at all; standard semiconductors do not work; it is difficult to implement resonant circuits and filters with standard parts; conventional analysis and design practices do not apply; different and more difficult and expensive measurement techniques and equipment are needed; line-of-sight transmission distances limit transmission range; and signals are more easily ref lected and absorbed by objects and atmospheric phenomena.
The L band, 1—2 GHz. Millimeter-wave bands. Multiplexing, single-sideband operation, improved receiver selectivity, use of special modulation techniques with digital data such as PSK and QAM, and digital data compression techniques. The primary architecture is in-phase I and quadrature Q modulation and demodulation. Generate a base carrier with a crystal oscillator or a frequency synthesizer and then use a chain of frequency multipliers to boost it into the desired microwave range.
Generate a base carrier at a lower frequency and use mixing to translate the frequency to the desired higher frequency.
RF amplifier, mixer, local oscillator; transmitter: RF power amplifier and frequency multipliers. Microstrip and stripline. Microstrip is more widely used because it is easier to work with and the materials are cheaper. Inductors, capacitors, tuned or resonant circuits. Hybrid ring. Internal geometries are designed to lower interelement capacitances, and large flat leads are used to minimize lead inductances. Microstrip lines are used in amplifiers for impedance matching as well as for needed inductance, capacitance, and tuned circuits.
Linear amplifiers used in microwave work are usually biased with a constant-current source that is not only variable to optimize bias but also more stable with temperature and minimizes damage to the devise due to thermal problems. Very high attenuation per foot. Higher for short lengths. This line cannot be easily bent or routed.
A small quarter-wave probe or antenna or a loop near the closed end of the waveguide. Electric E and magnetic H. Choke joint. Shunt T and series T. Used as power divider and power combiner. A hybrid T is a waveguide assembly with four ports. The arrangement of the ports causes the signals, either inputs or outputs, to go to some outputs but not to others because of electric and magnetic wave propagation. The hybrid T is frequently used to permit a single antenna to be used as both transmitter and receiver so that a signal from the transmitter is passed to the antenna but is prevented from entering the receiver front end and damaging it.
Typical terminations are metallic pyramids, powdered graphite, or a resistive wedge or pyramid. Waveguides not open or shorted and some multiple of a quarter-wave must be terminated to avoid reflections and high SWR.
To provide a way to tap off a small fraction of power to enable the power output to be measured by a low-power wattmeter. Cavity resonator. Parallel resonant circuit. Bandpass filters.
Principles of Electronic Communication Systems
Resonant frequency. A circulator is a three-port device that transfers energy applied to one port to the second port but not the third port. Circulators are used primarily as diplexers that allow a transmitter and receiver to share an antenna simultaneously, with transmitter power getting back into the receiver front end. An isolator is a two-port device that is unidirectional; that is, power is passed in one direction but not the other. Silicon diodes have high PN capacitance.
Silicon has lower electron mobility than other materials. Hot carrier diode or Schottky barrier diode. Mixing or frequency translation. Varactor; used as a frequency multiplier. Varactor and step-recovery diode.
These diodes do not amplify. Switch and variable resistance. Velocity modulation. Input, buncher cavity; output, catcher cavity. The U-shaped magnet. Microwave ovens and radar transmitters. Microwave power amplification for transmitters. With a helical coaxial cable or wire wound the length of the tube through which the electrons pass. Wide bandwidth. Horn or horn with parabolic reflector. Gain increases and beamwidth decreases with horn length.
The antenna must be at the focal point of the paraboloid. Cassegrain feed. Its purpose is to permit the horn to be at the center of the dish, which is usually a more convenient physical mounting arrangement.
Simplicity and low cost. Circular polarization. Right-hand circular polarization; left-hand circular polarization. In high-speed aircraft where protruding antennas add drag. By a waveguide. To focus the waves into a narrower beam. Patch antennas. Circular and rectangular. Coaxial or edge using a quarter-wave Q section.
Phased array. It is used in military radar. Loop, inverted-F, meander line. MIMO is multiple input multiple output and is a technique using multiple transmitters, receivers and antennas to create multiple signals with multiple paths from transmitter to receiver. This multiplies the data rate and because of the signal combining techniques with signals from multiple antennas, the effects of multipath fading and cancellation are mitigated making transmission more reliable.
MIMO, adaptive beam forming, and diversity. Higher gain and directivity to isolate signals to minimize interference. Spatial division multiplexing uses smart antennas to allow the use of a single channel to carry multiple calls by using the directive nature of the antennas to keep the signals separate and from interfering with one another.
Radar, satellites, cell phones, wireless LANs. Distance or range.
Directional characteristic. The size of the target is the most important characteristic, but the material of the target also affects the amount of reflection. K and X bands. Pulse and Doppler. Doppler shift. The magnetron power oscillator. Transmit-receive and anti-transmit-receive tubes, which are spark gaps that conduct when the high-power transmitter signal is turned on to prevent damage to the receiver. Cathode-ray tube CRT. Military, search, tracking, navigation; civilian, aviation, marine navigation, weather, speed limit enforcement.
Assuming a dish of one wavelength at the lowest frequency, 4.
The size of the target should be at least one-quarter wavelength or greater for a good reflection. The larger the size in wavelength, the greater the reflection. Use multiple W power amplifiers driven by the same source and combine their outputs in a power combiner to a common load, thus producing a 1-kW signal. As the spacecraft gets farther away, its signal strength will decrease. One way to maintain or possibly increase signal strength is to build a larger antenna. Typical antennas used in space probe monitoring are very large diameters of 64 m or about ft.
Such antennas thus. Keep in mind that as the size and gain of the antenna increase, the beamwidth gets smaller and smaller, making it ever more difficult to aim the antenna at the location of the spacecraft.
Further, any improvement in signal-to-noise ratio will also help. Using a lower-noise front-end amplifier or cooling the. The physics of shorter wavelengths results in short transmission ranges. Consider the Friis formula where wavelength is a key factor in computing distance. CMOS integrated circuits. Posigrade orbit. An ascending orbit is the movement of a satellite from south to north across the equator. A descending orbit is the movement of a satellite in orbit from north to south across the equator.
At microwave frequencies this causes reflection and refraction, which degrade the signal. Geosynchronous or geostationary. Subsatellite point. Azimuth and elevation. A satellite is a radio relay station that receives a signal and retransmits it. Space-based relay stations like satellites are used because greater communications distances can be achieved at lower cost than by the use of multiple earth-based stations. The earth or ground station.
The transponder consists of a low-noise amplifier that picks up the weak signal from the ground station and sends it to a mixer, where it is mixed with a local oscillator signal. All modulation is translated as well. The mixer output is then amplified by a power amplifier and retransmitted back to earth. A common antenna is used for receiving and transmitting.
C band. X band. Telephone calls, computer data, and TV signals. RF power transistors are used in lower-power satellites, and TWT amplifiers are used in higher-power satellites. Solar battery panels. Onboard batteries. Amplifies it in a low-noise amplifier. The signal may also be filtered for selectivity and sent to a power divider.
Phase-locked loop frequency synthesizer. Transistor, klystron, and TWT. A VSAT is a very small aperture terminal, a small low cost satellite earth station used for communicating with satellites. Digital compression techniques like MPEG2 allows satellites to transmit high speed video. The LNB is used because the Ku band signals from the antenna would be attenuated too much by any coax transmission line. Horizontal and vertical polarization keeps signals separate. Zero degrees. Latitude and longitude.
The L1 signal on L band. Differential GPS uses a precisely placed earth station that receives the L 1 GPS signals and computes the error between them and its own precisely known location. The error is transmitted to special DGPS receivers that can decipher the error data and correct the output. Accuracies to within 3 to 6 ft are possible. To achieve a higher data rate in the same bandwidth.
The P code is also a pseudorandom code and has a rate of The Y code is an encrypted version of the P code that prevents unauthorized use of certain precision features of GPS.
Almost any standard antenna may be used for satellite uplink or downlink, including dipoles, ground planes, and Yagis. Since the satellite will be moving continuously with respect to the position of the ground stations, the antennas must be positioned so that their pattern is within range of the satellite. The downside to this is that omnidirectional antennas have no gain. If satellite power is sufficient and receiver gain and signal-to-noise ratio are satisfactory, this approach will work fine.
If gain antennas are to be used, the beamwidth should be broad so that the satellite is within. If high gain is required, the beamwidth will be very narrow, and some type of automatic tracking and pointing mechanism must be used on the antenna to keep it pointing at the satellite. Highly directional antennas with gain are preferred, to ensure reliable communications, but they cost more and are more complex because of the automatic tracking equipment.
The communications link will be broken one per orbit, when the satellite goes on the opposite side of the earth, at which time a blackout will exist for approximately one satellite period. Use a map marked with latitude and longitude. Use spread spectrum. LEO satellites are closer to earth so less power is needed in the handsets but more satellites are needed for full continuous coverage, making initial costs high.
In MEO systems, fewer satellites are needed but for higher power more expensive handsets are needed. GEO satellite cell phones are impractical as the distance is too great, making handsets too large and expensive. The pseudo random code PRC transmitted by each satellite is unique and is used by the receiver to identify each satellite.
Chapter 18 Answers to Questions 1. The telephone is powered by DC voltage approximately 48 V with respect to ground supplied over the local loop by the telephone company. The ringing signal is a sine wave at approximately 20 Hz with a value of about 90 V rms. A hybrid is a transformer-like device that allows two signals to share a common pair of wires so that they may send and receive at the same time. A hybrid may also be an electronic circuit that accomplishes the same result.
Standard telephones use a carbon microphone which consists of carbon granules inside a chamber covered by a diaphragm. When voice waves strike the diaphragm, it vibrates and thus compresses and decompresses the carbon granules, causing their overall resistance to vary. The resistance variations are converted to voltage by connecting a voltage source to the carbon element. Tip and ring are the two connections to and from the twisted-pair line. Tip is green, and ring is red.
If a second line is used, the tip may be yellow and the ring black. Dual-tone multifrequency DTMF. Central office or local exchange. The bridge rectifier is used to prevent damage to telephone circuits due to polarity reversal of the DC voltage supplied by the telephone company.
Piezoelectric sounder. Modular connector or RJ There are 20 channels. Cordless phones, especially the newer ones, use the MHz, 2. A key telephone system allows the connection of many telephones to one of several telephone lines. They can usually accommodate up to about 50 telephones and three or four separate lines to the local exchange. Both reference the original wired telephone system still in wide use. The telephone system; radio. Group 2.
Charged coupled device CCD. Group 3 or G3. The modem. Analog shades of gray. The phone number of a calling party is displayed on the phone when the ring tones are received. Limited number of channels, limited distance, susceptible to noise. Analog, digital, spread spectrum. Spread spectrum direct sequence. Because spread spectrum is used. Signaling refers to the process of setting up and tearing down a telephone circuit connection.
They use an IP Internet connection. ITU H. Compression is needed to limit data speed and bandwidth so more calls can be handled. Compression is accomplished with DSP. Analog terminal adapter, VozIP gateway. The latency of the communications link adds delay that is annoying. Compression is needed to reduce the data rate of the digital voice signal so that it can pass through narrow bandwidth channels.
Compression and decompression is accomplished by algorithms implemented in DSP. The delay time or latency that causes the voice to appear at the receiver later than simultaneous real time. It is caused by the delay as voice packet pass through routers, servers and other devices on the Internet.
Links between exchanges are four-line rather than two-line; that is, the send and receive signals are.The L1 signal on The local oscillator frequency is equal to the received signal frequency. If one node transmits, no others can transmit until the first transmission is complete.
Bessel C. A circulator is a three-port device that transfers energy applied to one port to the second port but not the third port. Crystal, ceramic, and SAW filters. Dotted decimal. Good frequency stability. As the voltage becomes more positive, the capacitance of the varactor D1 decreases. You cannot see light travel because its speed is so fast that it appears instantaneous.