Description : ECE Board Exam March 1996 The modulation system used for telegraphy is A. frequency-shift keying B. two-tone modulation C. pulse-code modulation D. single-tone modulation
Last Answer : A. frequency-shift keying
Description : What term is used to describe a spread spectrum communications system in which a very fast binary bit stream is used to shift the phase of an RF carrier? A. Frequency hopping B. Direct sequence C. Binary phase-shift keying D. Phase compandored spread spectrum
Last Answer : B. Direct sequence
Description : Phase-shift keying is similar to what other two types of modulation?
Last Answer : Cw and frequency-shift keying.
Description : A multiple access technique used in GSM cellular system A. TACS B. FDMA C. TDMA D. CDMA
Last Answer : C. TDMA
Description : Modulation in which no signal is present between pulses A. Pulse modulation B. QAM C. PSK D. FSK
Last Answer : A. Pulse modulation
Description : Describe amplitude shift keying (ASK) modulation with suitable circuit diagram.
Last Answer : Explanation:- ASK MODULATOR: The process where a binary information signal directly modulates the amplitude of an analog carrier. The digital signal is used to switch the carrier between amplitude levels is ... Block diagram of ASK Transmitter / ASK modulator:- Waveforms:-
Description : What is a simplified difference between Phase Shift Keying and Frequency Shift Keying?
Last Answer : answer:FSK adjusts the frequency, PSK adjusts the phase. We use nonstandard PSK in our work because we can design a pre-amp and amp around the one frequency and design a filter with broad Q in the range of ... said ;-) Here is a good reference with pictures. If you need more then look at fsk vs psk
Description : Inan HFC network, the upstream data are modulated using the _______ modulation technique. A) QAM B) QPSK C) PCM D) ASK
Last Answer : QPSK
Description : Inan HFC network, the downstream data are modulated using the _______ modulation technique. A) PSK B) QAM C) PCM D) ASK
Last Answer : QAM
Description : DMT is a modulation technique that combineselements of _______ and _______. A) FDM; TDM B) QDM; QAM C) FDM; QAM D) PSK; FSK
Last Answer : FDM; QAM
Description : IS-95 uses which modulation technique? a) GMSK b) BPSK c) QAM d) AFSK
Last Answer : b) BPSK
Description : Which of the following systems is not used in radio detection and ranging? A. Frequency shift B. Frequency modulation C. Pulse radar D. Amplitude modulation
Last Answer : D. Amplitude modulation
Description : Which of the following is the world’s first cellular system to specify digital modulation and network level architecture? a) GSM b) AMPS c) CDMA d) IS-54
Last Answer : a) GSM
Description : In GSM cellular system, the speech coding rate is ____. A. 13 kbps B. 8 kbps C. 15 kbps D. 20 kbps
Last Answer : A. 13 kbps
Description : Refers to the first generation of local loop system in telecommunication technology. A. GSM B. DECT C. Analogue cellular D. TACS
Last Answer : C. Analogue cellular
Description : In modulation technique, which of the following is referred to audible pitch? A. Width B. Frequency C. Harmonic D. Amplitude
Last Answer : B. Frequency
Description : What is the transmission rate of a GSM cellular system? A. 64 kbps B. 240 kbps C. 128 kbps D. 270 kbps
Last Answer : D. 270 kbps
Description : Noise from random acoustic or electric noise that has equal energy per cycle over a specified total frequency band. A. Gaussian noise B. Whiter noise C. Thermal noise D. All of the above
Last Answer : D. All of the above
Description : Noise from random acoustic or electric noise that has equal per cycle over a specified total frequency band. A. Thermal noise B. White noise C. Gaussian noise D. All of these
Last Answer : D. All of these
Description : Which modulation technique is used by GSM? a) GMSK b) BPSK c) QPSK d) GFSK
Last Answer : a) GMSK
Description : Frequency shift keying is used mostly in: (1) Telegraphy (2) Telephony (3) Satellite communication (4) Radio transmission
Last Answer : Frequency shift keying is used mostly in: Telegraphy
Description : Both frequency and phase modulation utilize ________ modulation A. Phase B. AM and FM C. Digital D. Angle
Last Answer : D. Angle
Description : What is the difference between phase and frequency modulation? A. Is purely theoretical because they are the same in practice B. Lies in poorer audio response of phase modulation C. Lies in the different definitions of the modulation index D. Is too great to make two systems compatible
Last Answer : C. Lies in the different definitions of the modulation index
Description : What type of transmission is radiated from an aircraft’s radio altimeter antenna? A. An amplitude modulated continuous wave B. A pulse position modulated UHF signal C. A differential phase shift keyed UHF signal D. A frequency modulated continuous wave
Last Answer : D. A frequency modulated continuous wave
Description : Assume a frequency of 4 MHz, determine the phase shift offered by the line in the above problem. A. 108.5˚ B. 106.5˚ C. 115.5˚ D. 166.5˚
Last Answer : D. 166.5˚
Description : Which of the following is standardized as part of GSM phase 2+ that can offer theoretical data speeds of upto 115 kbit/s? A. EDGE B. GPRS C. WAP D. Bluetooth
Last Answer : B. GPRS
Description : If digitaldata rateof 9600 bps is encoded using 8-level phaseshift keying (PSK) method, the modulation rate is A. 1200 bands B. 3200 bands C. 4800 bands D. 9600 bands E. None of the above
Last Answer : 3200 bands
Description : In amplitude modulation technique the unmodulated carrier is referred to as having ______. A. 100% modulation B. 0% modulation C. 50% modulated D. Over modulated
Last Answer : B. 0% modulation
Description : Digital modulation technique used in modems. A. ASK B. PSK C. FSK D. All of these
Last Answer : B. PSK
Description : Quadrature amplitude modulation(QAM) isa combination of ___________. A) ASK and FSK B) ASK and PSK C) PSK and FSK D) none of the above
Last Answer : ASK and PSK
Description : Another SEG function that allows a person to be superimposed on another scene. A. Visual effect B. Wiper C. Chroma keying D. Special effect generation
Last Answer : C. Chroma keying
Description : Background noise is the same as the C. Thermal noise D. Gaussian noise 24. ECE Board Ex
Last Answer : A. Impulse noise
Description : In________, the phase of thecarrier is varied to represent two or more different signal elements. Both peak amplitude and frequency remain constant. A) ASK B) PSK C) FSK D) QAM
Last Answer : PSK
Description : In________, the amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remainconstant. A) ASK B) PSK C) FSK D) QAM
Last Answer : ASK
Description : The sinusoidal carrier is pulsed so that one of the binary states is represented by a carrier while the other is represented by its absence. A. FSK B. ASK C. PSK D. QAM
Last Answer : B. ASK
Description : What is the term used to describe a spread spectrum communications system where the center frequency if a conventional carrier is altered many time per second in accordance with a pseudo ... hopping B. Direct sequence C. Time-domain frequency modulation D. Frequency compandored spread spectrum
Last Answer : A. Frequency hopping
Description : A good example of a pilot tone system used in commercial frequency modulation stations. A. FDM B. Time division C. Stereo multiplexing D. Frequency modulation
Last Answer : C. Stereo multiplexing
Description : What is the main purpose of a communications system? A. None of these B. To have a frequency assignment C. For modulation D. To provide an acceptable replica of the information at the destination
Last Answer : D. To provide an acceptable replica of the information at the destination
Description : Which of the following antennas is used for testing and adjusting a transmitter for proper modulation, amplifier operation and frequency accuracy? A. Elementary B. Real C. Isotropic D. Dummy
Last Answer : D. Dummy
Description : Why are frequency modulation transmitters more efficient? A. Because their power is increased by class C amplifiers B. Because their power is increased by class A amplifiers C. Because their power is increased by class B amplifiers D. Because their power is increased by class AB amplifiers
Last Answer : A. Because their power is increased by class C amplifiers
Description : What is the deviation ratio for an FM-phone signal having a maximum frequency swing of plus or minus 5 kHz and accepting a maximum modulation rate of 3kHz? A. 60 B. 0.16 C. 0.6 D. 1.66
Last Answer : D. 1.66
Description : What is meant by the term modulation index? A. The processor index. B. The ratio between the deviation of a frequency modulated signal and the modulating frequency. C. The FM signal-to-noise ratio. D. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.
Last Answer : B. The ratio between the deviation of a frequency modulated signal and the modulating frequency.
Description : What is meant by the term deviation ratio? A. The ratio of the carrier center frequency to the audio modulating frequency B. The ratio of the highest audio modulating frequency to the ... audio modulation frequency D. The ratio of the audio modulating frequency to the center carrier frequency
Last Answer : C. The ratio of the maximum carrier frequency deviation to the highest audio modulation frequency
Description : This is referred to a product of simultaneous frequency and amplitude modulation or a carrier frequency variation which produces unwanted distortion. A. Absorption modulation B. Simultaneous modulation C. Dynamic instability D. Series modulation
Last Answer : C. Dynamic instability
Description : It is an average power of a radio transmitter supplied to the antenna transmission line taken during a long sufficient interval of time and compared with the lowest frequency encountered in the modulation ... operating conditions. A. Carrier power B. Rated power C. Mean power D. Peak envelop power
Last Answer : C. Mean power
Description : One of the following is not among the advantages of series modulation A. No transformer B. Suppressed white noise C. Simple D. Modulates any frequency
Last Answer : B. Suppressed white noise
Description : Referred to as an average power from the radio transmitter supplied to the antenna transmission line taken during one radio frequency cycle under no modulation. A. Carrier power B. Rated power C. Peak envelop power D. Mean power
Last Answer : A. Carrier power
Description : Used for time division multiplexing. A. Frequency modulation B. Pulsed modulation C. SSB D. Amplitude modulation
Last Answer : B. Pulsed modulation
Description : Average power of a radio transmitter supplied to the antenna transmission line by a transmitter during one radio frequency cycle taken under the condition of no modulation. A. Peak envelop power B. Rated power C. Carrier power D. Mean power
Last Answer : C. Carrier power
Description : Emission on a frequency or frequencies immediately outside the necessary bandwidth which result from the modulation process except spurious emission. A. Radiation B. Noise C. Out of the band D. Interference
Last Answer : C. Out of the band