Mapa Institute of Technology

FINALS (ECE121 / E01)

COURSE OUTCOME 1

1. The cutoff frequency, fc, of a filter is the frequency at which

2. A type of filter that allows only low frequency signals

3. A type of filter that has a flat passband and stopband response but slow transition

4. A band reject filter is also known as

5. Which of the following statements is not true about bandpass filters?

6. Which of the following statements is true about reactance?

7. A signal transmission line which has a source impedance of 75ohms is to be connected to a signal strength meter of impedance 50ohms which has a maximum display of -12dB. Calculate the values of resistors required in an L-pad attenuator circuit to operate the meter at maximum power.

8. An H-pad has an insertion loss of 50dB, what is its current ratio if the input impedance is equal to its terminating impedance?

9. A parallel LC circuit has a resonant frequency of 3.75MHz and a Q of 125. What is the bandwidth?

10. A higher Q for a resonant circuit provides

11. A figure of merit that determines the sharpness of the frequency response curve in filters

12. The phase angle of an LC circuit at resonance is

13. On logarithmic graph paper, a 10 to 1 range of frequencies is called a (n)

14. The capacitor in an LC circuit has R equal to 50ohms and XC value of 500ohms at its resonant frequency. How much is the net reactance?

15. The decibel attenuation of a passive filter at the cut-off frequency is

16. What is the loss of the circuit in dB if the power ratio of output to input is 0.01?

17. Convert 5W to dBm

18. A filter in which the signal passes through an inductor, or in which a capacitor provides a path to ground, presents less attenuation to low-frequency signals than high-frequency signals.

19. What is the resonant frequency of an LC circuit with values L=100 microhenry and C=63.3 picofarad?

20. Determine the input impedance of a T-pad with a series arm of 100ohms and shunt arm of 1750ohms and a terminating impedance of 450ohms

21. Which of the following is true about parallel resonant circuit?

22. The input power to a filter is 100mW and the output power is 5mW. Calculate the attenuation in decibels offered by the filter

23. One of Mapua’s mission statement is

24. Which of the following is best used as AF amplifier?

25. Which of the following is true about series resonant circuit?

26. To increase the cutoff frequency of an RL high-pass filter,

27. What is the total power in dBm of three circuits having 6dBm, 3dBm and 8dBm respectively?

28. Above resonance, a parallel LC circuit appears

29. Which of the following will provide a more selective filtering?

30. Without resonant circuits there would be no radio communication. Resonant circuit is not an essential part of

31. A Pi-pad attenuator circuit is required to reduce the level of an audio signal by 10dB while matching the impedance a 75ohms network. Calculate the values of the three resistors required

32. Mapua’s vision statement

33. The capacitor in an RC coupling circuit

34. The doubling or having of frequencies is called a(n)

35. A type of power amplifier whose output conducts load current during less than one-half cycle of an input sine wave.

36. For an RC circuit,

37. In a series resonant circuit, do the values of XL and XC, affect the value of I at fr?

38. What is the effect of loading a resistor across a tuned circuit?

39. A parallel LC circuit has a resonant frequency of 3.75MHz and a Q of 125. What is the bandwidth?

40. A bridged-T attenuator is required to reduce the level of an 8ohms audio signal line by 4dB. Calculate the values of the resistors required

41. In an RC low-pass filter, the output is taken across the

42. A type of filter that has a faster transition but has variations on the passband

43. Below resonance, a series LC circuit appears

44. A filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels
45. This is the minimum range of frequencies required propagating the source information through the system
46. Which network is considered symmetric and unbalanced?

47. A type of power amplifier with the least amount of distortion

48. An H-type attenuator is required to provide a 6-dB insertion loss and to match 50 ohms input and output. What must be the value of the series resistance?

49. The cut-off frequency, fc, of a filter is the frequency at which the output is

50. What is the decibel (dB) attenuation of a filter with a 100-mV input and a 1-mV output at a given frequency?

COURSE OUTCOME 2

1.) Suppose the noise power at the input to a receiver in 5mW in the bandwidth of interest. What would be the required signal power for a signal-to-noise ratio at 30dB?

2.) In a given bandwidth, more channels are available for signals in the range of

3.) Microwaves start at

4.) The name of the first commercial communication satellite

5.) The bandwidth required for a modulated carrier depends on

6.) The baseband bandwidth for a voice-grade (telephone) signal is

8.) The wavelength of a radio signal depends is

9.) The noise produced by a resistor is to be amplified by a noiseless amplifier having a voltage gain of 100 and a bandwidth of 10-kHz. A sensitive meter at the output reads 250uVRMS

10.)The VHF band starts at

11.)The signal is measured to be 23dB while noise in the same channel is measured to

12.)Equipment that represents the signal in the frequency domain is the

13.)A shot noise is generated in the

14.)Noise in a communication system originates in

15.)The equivalent noise temperature of the amplifier is 25 K

16.)The power density of “flicker” noise is

17.)Provides the means of transporting signals between a transmitter

18.)Recovering the originally transmitted signal is called

19.)An amplifier has an output S/N that is half of its input S/N. What is the noise figure?

20.)Determine the noise figure for an amplifier with an input signal-to-noise ratio of

21.)A complete communication system should include

22.)What is the total noise power in dBm for a bandwidth of 1kHz?

23.)A naturally occurring disturbance that originates from the earths

24.)Light frequency below 400 microns is

25.)Defined as the basic process of exchanging information

26.)The year when the mouse was invented, and the ASCII code was developed.

27.)The standard AM broadcast belongs to what frequency band

28.)Determine the equivalent noise a voltage for a diode with

29.)A noise figure is a measure of

30.)A 100mV of signal and 10mV of noise is across a 100ohm load

31.)Determine the noise current of a device for a current of 5mA

32.)Short waves fall under

33.)What is the equivalent noise temperature for a noise figure of 3dB?

34.)Refers to the transmission, reception and processing of information.

35.)Two resistors 5kohm and 20kohm

36.)Determine the overall noise figure for three cascaded amplifiers with the following

37.)“Man-made” noise can come from the

38.)A simultaneous two-way communication is called

39.)The noise produced by a resistor is to be amplified by a noiseless amplifier

40.)The ideal noise figure is

41.)So called “1/f” noise is called

42.)Thermal noise is generated

43.)The year when the cellular telephone network was first introduced

44.)Most internal noise comes from the

45.)It is a kind of noise that is mutually related to the input and is produced

46.)If an amplifier has a bandwidth B= 20kHz

COURSE OUTCOME 3

1.) An AM transmitter has a carrier voltage of 50 VRMS at a carrier frequency of 10MHz. It is modulated

2.) An antenna transmits an AM signal having a total power content of 15kW. Determine the power being

3.) A form of AM in which the carrier is totally suppressed and one of the sidebands is…

4.) The intermediate frequency for an AM broadcasting system...

5.) Determine the net receiver gain for an AM receiver with a RF input power…

6.) A 2000 Hz audio signal having amplitude of 15V amplitude modulates a 100kHz carrier

7.) What is the local oscillator frequency needed in a superheterodyne receiver

8.) Is a technique used in electronic communication, works by varying the strength?

9.) A certain transmitter radiates 9kW when the carrier is unmodulated…

10.)One of the following cannot be used to remove the unwanted sideband in SSB

11.)Which of the following statements is not true about single

12.)Which section a superheterodyne receiver converts the IF

13.)The percentage of modulation for a maximum amplitude

14.)A superheterodyne receiver with an IF of 450kHz is tuned to a signal

15.)Which is true about over modulation?

16.)If the carrier of a 100% modulated AM wave is suppressed, the percentage power

17.)An AM transmitter is modulated by two sine waves at 1 kHz and 2.5 kHz, with

18.)A type of SSB receiver where the RF oscillator and the BFO signals are

19.)Anticipating single sideband AM, what percentage of the total power is

20.)A superheterodyne receiver is tuned to a frequency…

21.)Indicate the false statement. The superheterodyne receiver replaces

22.)CB radios were developed using the full-carrier DSB AM. It operates using 40 channels

23.)Produces a frequency input to beat (mix) with the IF signal and results

24.)A signal other than the desired RF which when mixed with the oscillator…

25.)For an AM receiver tuned to a station of 590kHz, with IF=455kHz. Calculate…

26.)What is the major advantage of the superheterodyne

27.)The type of AM signal that used in TV broadcasting is called

28.)What parameter enables a receiver to detect the weakest possible

29.)A frequency to which a carrier frequency is shifted as an intermediate.

30.)A receiver for a signal at 150MHz uses a 10.7MHz IF and low tracking

31.)The process of recovering the intelligence signal from a modulated

32.)A modulator circuit performs what mathematical operation

33.)A measure of the extent to which a receiver is capable of differentiating

34.)A form of amplitude modulation in which a single carrier frequency is independently

35.)One of the functions of the RF amplifier in a superheterodyne..

36.)A bandwidth of 12MHz becomes available for assignment. If assigned for TV broadcast

37.)Uses frequency mixing to convert a received signal to fixed intermediate

38.)A measure of the ability of a communications system to produce, at the output

39.)What is the required bandwidth to transmit the AM signal for a 2000 Hz

40.)In the designation of bandwidth and emission, what letter in the first symbol represents

41.)An AM transmitter must transmit 39.9-kW PEP, it maintains

42.)Are circuits used to produce double sidebands by effectively cancelling the

43.)To provide two or more voice circuits with the same carrier, it is necessary

44.)If a transmitter power of 100W is sufficient for reliable communication over… using DSBFC

45.)If a transmitter power of 100W is sufficient for reliable communication over… using DSBSC

46.)A 2000 Hz audio signal amplitude modulates a 100kHz

47.)An AM wave has a total transmitted power of 4kW when modulated 85%

48.)The trace of the peak of an AM wave which has the same shape

49.)Calculate the percentage power saving when the carrier and one of the sidebands…

COURSE OUTCOME 4

1. 1. Frequency modulation transmitter are more efficient because their power is increased by what type of amplifier?

1. 2. The primary disadvantage of FM is its
   3. The maximum deviation of an FM carrier is 2 kHz by a maximum modulating signal of 400 Hz. The deviation ratio is

1. 4. What is the approximate frequency of the modulating signal having a bandwidth of 15 kHz and a frequency deviation of 6 kHz?

1. 5. Both FM and PM are types of what kind of modulation?

1. 6. An FM transmitter has a maximum deviation of 12 KHz and a maximum modulating frequency of 12 KHz. The bandwidth by Carson's rule is

1. 7. An analog multiplexing technique where the optical fiber data rate is higher than the data rate of the metallic transmission cable. It is also used to combine optical signals.

1. 8. The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal?

1. 9. CDMA stands for:

1. 10. Pre emphasis is compensated for at the receiver by a

1. 11. The AM signals generated at a low level may only be amplified by what type of amplifier?

1. 12. It refers to the portion of a link that carries a transmission between a given pair of lines.

1. 13. If the amplitude of the modulating signal decreases, the carrier deviation
   14. In PM, carrier frequency deviation is not proportional to:
   15. Which of the following is not a major benefit of FM over AM?

1. 16. What is the relative amplitude of the third pair of sidebands of an FM signal with m=6?

1. 17. It is the basic building block of the FDM hierarchy

1. 18. A pre-emphasis circuit is a

1. 19. It is the most significant circuit in a de-multiplexer

1. 20. A 70 kHz carrier has a frequency deviation of 4kHz with a 1000Hz signal. How many significant sideband pairs are produced?

1. 21. The cutoff frequency of pre-emphasis and de-emphasis circuits is

1. 22. Maximum frequency deviation of a PM signal occurs at

1. 23. What is the BW required for an FM signal in which the modulating frequency is 2 kHz and the maximum deviation is 10 kHz? 8 pairs of sidebands are included.

1. 24. A 200KHz carrier is modulated by a 2.5KHz signal. The fourth pair of sidebands are spaced from the carrier by

1. 25. The FM produced by PM is called

1. 26. How many voice channels are there in a master group?

1. 27. An FM broadcast station operates with a peak-to-peak deviation of 120 kHz. Calculate the percentage modulation

1. 28. On an FM signal, maximum deviation occurs at what point on the modulating signal?
   29. An analog modulation process in which the timing of each resulting pulse varies with the amplitude of the original signal. The sampled pulses have the same amplitude and duration

1. 30. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?

1. 31. Which of the following is not a common FDM application?

1. 32. The maximum allowed deviation of the FM sound signal in TV is 25KHz. If the actual deviation is 18KHz, the percent modulation is

1. 33. In PM, a frequency shift occurs while what characteristic of the modulating signal is changing?

1. 34. An analog pulse modulation technique in which the duration of each resulting pulse is varied in step with the amplitude of the modulating signal at the time it is sampled and that the sampled pulses have the same amplitude.

1. 35. What is the amount of carrier swing necessary to produce an 80% modulation for FM broadcasting?

1. 36. The phenomenon of a strong FM signal dominating a weaker signal on a common frequency is referred to as the

1. 37. The audio section of a TV transmission employs frequency modulation with a maximum allowable deviation of 25 kHz. Find the deviation ratio if the highest intelligence frequency it can handle is 15 kHz.

1. 38. In an FM system, when the audio frequency is 500 Hz and the AF voltage is 2.4 V, the deviation is 4.8 kHz. If the AF voltage is now increased to 7.2 V, what is the new deviation?

1. 39. A form of digital modulation where the amplitude of the modulating signal is converted into binary coded pulses.

1. 40. A 100MHz carrier is deviated 50kHz by a 4kHz signal. The modulation index is

1. 41. The circuit that boost the high audio frequencies in modulation at the transmitter, used to improve the signal-to-noise ratio.

1. 42. The circuit that attenuates the high audio frequencies by the same amount that they are boosted to compensate for the effect of the pre-emphasis

1. 43. To compensate for increases in carrier frequency deviation with an increase in modulating signal frequency, what circuit is used between the modulating signal and the phase modulator?

1. 44. Pre emphasis circuits boost what modulating frequencies before modulation?

1. 45. The process of receiving a single signal that produces multiple channels simultaneously.

1. 46. If the amplitude of the modulating signal applied to a phase modulator is constant, the output signal will be

1. 47. An analog pulse modulation scheme in which the amplitude of each resulting pulse is made proportional to the amplitude of the modulating signal at the instant at which it is sampled
   48. The receiver circuit that rids FM noise is the