Homework answers / question archive / Mapa Institute of Technology - ECE 121 ECE121 / E01 (2Q1819) COMPILED QUIZZES QUIZ 1: 1)What is the loss of the circuit in dB if the power ratio of output to input is 0

Mapa Institute of Technology - ECE 121 ECE121 / E01 (2Q1819) COMPILED QUIZZES QUIZ 1: 1)What is the loss of the circuit in dB if the power ratio of output to input is 0

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Mapa Institute of Technology - ECE 121

ECE121 / E01 (2Q1819)

COMPILED QUIZZES QUIZ 1:

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

 

2.         An amplifier has a 53-dB gain and a 10-W output. What input signal power does it have?

 

3.         A parallel tuned circuit has a Q-factor of 200 when tuned to a resonance 10MHz. the value of tuning capacitance is 10pF. Calculate the dynamic impedance of the circuit.

 

4.         Match the amplifiers.

 

5.         The capacitor in an RC circuit has R equal to 50Ω and XC value of 500 Ω at its resonant

frequency. How much is the net reactance?

 

6.         What will be the total power of a system having P1 = 4dBm, P2 = 6dBm, P3 = 5dBm and P4 = 10dBm respectively?

 

7.         A bridged-T attenuator is required to reduce the level of an 8Ω audio signal line by 4dB.

Calculate the values of the resistors required.

 

8.         Calculate the attenuation in decibels for a T-pad for which R3=31Ω and R8=25Ω. The pad

connects a 50Ω generator to a 50Ω load.

 

 

 

9.         Match the statements with the corresponding letter

 

10.       What is the resonant frequency of an LC circuit with values L=100uH and C=63.3pF?

 

11.       Determine the input impedance of a T-pad with a series arm of 100Ω and shunt arm of 1750Ω

and a terminating impedance of 450Ω.

 

12.       A signal transmission line which has a source impedance of 75Ω is to be connected to a signal strength meter of impedance 50Ω 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.

 

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

 

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

 

15.       The input power to a filter is 100mW and the output power is 50mW. Calculate the attenuation in decibels offered by the filter.

 

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

 

 

17.       Above resonance, a parallel LC circuit appears

 

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

 

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

 

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

 

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

 

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

 

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

 

24.       Mapua’s vision statement

 

25.       In a series resonant circuit, do the values of XL and XC affect the value of 1 at fR?

 

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

 

27.       Below resonance, a series LC circuit appears

 

28.       The cut-off frequency, fc, of a filter is the frequency at which the gain

 

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

 

30.       One of the Mapua’s mission statement is

 

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

 

32.       To increase the cutoff frequency of an RL high-pass filter, you can

 

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

 

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

 

35.       The capacitor in an RC coupling circuit

 

36.       The doubling or halving of frequencies is called a(n)

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

 

38.       Which network is considered symmetric and unbalanced?  

QUIZ 2:

1.         The signal level at the input of the amplifier is 127 uV, and the noise level is 13 uV. Calculate the noise figure of the amplifier if the signal-to noise ratio at the output is 13 dB

 

2.         Match the statements to the appropriate letter answer. Answer:

 

 

3.         The signal level at the input of the amplifier is 100 uV, and the noise level is 5 uV. Calculate the noise figure of the amplifier if the signal-to noise ratio at the output is 14 dB.

 

4.         Match the letter to the appropriate description.

 

 

 

5.         The integrated circuit was invented in 1960

 

6.         Three resistors, 123 kΩ and 72 kΩ, are at room temperature. For a bandwidth of 77 kHz,

calculate the thermal noise voltage when they are connected in parallel.

 

7.         What is the noise voltage when the equivalent noise resistance is 42 kΩ, the bandwidth is 6 kHz, and the temperature is 74 oC?

 

8.         What is the equivalent noise resistance when the measured noise voltage is 547 uV, the temperature is 344 K, and the bandwidth is 32 kHz?

 

9.         Compute the noise figure of a receiving system with a noise temperature of 250 oC.

 

10.       Three resistors, 116 kΩ, 30 kΩ and 72 kΩ, are at room temperature. For a bandwidth of 78 kHz, calculate the thermal noise voltage when they are connected in parallel.

 

11.       A mixer stage has a noise figure of 25 dB, and this is preceded by an amplifier that has a noise figure of 10 dB and an available power gain of 20 dB. Determine the overall noise figure referred to the input.

 

12.       Determine the overall figure for three cascaded amplifiers with the following parameters: G1 = G2 = G3 = 10dB, and F1 = F2 = F3 = 3dB.

 

13.       The signal level at the input of the amplifier is 135 uV, and the noise level is 6 uV. Calculate the noise figure of the amplifier if the signal-to noise ratio at the output is 14 dB.

 

 

14.       What is the equivalent noise resistance when the measured noise voltage is 469 uV, the temperature is 338 K, and the bandwidth is 18 kHz?

 

15.       Determine the noise current for a diode with a bias current of 37 mA, observed over a 29-kHz bandwidth.

 

16.       What is the equivalent noise resistance when the measured noise voltage is 381 uV, the temperature is 291 K, and the bandwidth is 36 kHz?

 

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

 

QUIZ 3:

1.         A type of SSB receiver where the RF oscillator and the BFO signals are not synchronized to each other and to the oscillator in the transmitter.

 

2.         Calculate the percentage power saving when the carrier and one of the sidebands is suppressed in an AM signal if the modulation index is 25%.

 

3.         To provide two or more voice circuits with the same carrier, it is necessary to use the

 

 

5.         If a transmitter power of 100W is sufficient for reliable communication over a certain path using the SSB, approximately what power level would be required using DSBFC?

 

6.         A superheterodyne receiver is tuned to a frequency of 5MHz when the oscillator frequency is 6.65MHz. What is the IF?

 

7.         For an AM receiver tuned to a station at 590kHz, with IF=455kHz. Calculate the image frequency rejection in dB. Assume that the input filter consists of one tuned circuit with a Q of 40.

 

8.         An AM transmitter must transmit 39.9-kW PEP, it maintains an average current of 1.5A and a 80% plate efficiency. Determine the unmodulated carrier power.

 

9.         What parameter enables a receiver to detect the weakest possible signal level?

 

10.       One of the functions of the RF amplifier in a superheterodyne receiver is to

 

11.       The intermediate frequency for an AM broadcasting system per FCC rules is

 

12.       The letter in the first symbol for an ISB signal in the bandwidth emission designation is J.

 

13.       Uses frequency missing to convert a received signal to a fixed intermediate frequency (IF), which can be more conveniently processed than the original radio carrier frequency.

 

14.       Which is true about over modulation?

 

15.       Anticipating single sideband AM, what percentage of the total power is saved by suppressing the carrier and one sideband while transmitting the other sideband only for m=0.75?

 

16.       If a transmitter power of 100W is sufficient for reliable communication over a certain path using the SSB, approximately what power level would be required using the DSBFC?

 

17.       A bandwidth of 12 MHz becomes available for assignment. If assigned for TV broadcast service, only two channels could be accommodated. Determine the number of AM stations that could broadcast simultaneously if the maximum modulating frequency is limited to 5 kHz.

 

18.       Is a technique used in electronic communication, works by varying the strength of the transmitted signal in relation to the information being sent.

 

19.       An antenna transmits an AM signal having a total power content of 15 kW. Determine the power being transmitted at each of the sidebands when the percent modulation is 85%.

 

20.       One of the following cannot be used to remove the unwanted sideband in SSB. This is the

 

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

 

22.       The process of recovering the intelligence signal from a modulated carrier signal.

 

23.       An AM transmitter is modulated by two sine waves at 1 kHz and 2.5 kHz, with modulations of 25% and 50%, respectively. What is the effective modulation index?

 

24.       An AM transmitter has a carrier voltage of 50 VRMS at a carrier frequency of 10 MHz. It is modulated at 75% by a 1-kHz sine wave. What is the total RMS voltage transmitted?

 

25.       Are circuits used to produce double sidebands by effectively cancelling the carrier at the output

 

26.       What is the local oscillator frequency needed in a superheterodyne receiver tuned to a signal at 1200kHz to produce an IF of 450KHz?

 

27.       A 2000 Hz audio signal amplitude modulates a 100 kHz carrier, what frequencies would show up in a spectrum analysis of the AM wave?

 

28.       Match the emission designation codes to the type of signal.

 

29.       An AM wave has a total transmitted power of 4kW when modulated 85%. What is the total transmitted power if J3E was used instead?

 

30.       What is the major advantage of the superheterodyne receiver over the tuned radio frequency receiver?

 

31.       A form of AM in which the carrier is totally suppressed and one of the sidebands is removed

 

32.       A 2000 Hz audio signal having amplitude of 15V amplitude modulates a 100 kHz carrier, which has a peak value of 25 V when not modulated. Calculate the modulation factor of the modulated wave.

 

33.       A certain transmitter radiates 9 kW when the carrier is unmodulated and 10.75 kW when modulated. If another sine wave, corresponding to 30% modulation, is transmitted simultaneously, what is the percent change of the total power?

 

34.       Produces a frequency input to beat (mix) with the IF signal and results in a difference and sum frequencies with the result being the original audio.

 

35.       A measure of the ability of a communications system to produce, at the output of the receiver, an exact replica of the original source information.

 

36.       Which section of a superheterodyne receiver converts the IF signal to the original source information?

 

37.       A measure of the extent to which a receiver is capable of differentiating between the desired information signals and the disturbances or information signal at other frequencies.

 

38.       The superheterodyne receiver replaces the TRF receiver when the latter suffer from instability and gain variation over the frequency range covered.

 

39.       A frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception.

 

40.       A receiver for a signal at 150MHz uses a 10.7MHz IF and low tracking. Calculate the image frequency.

 

41.       A form of amplitude modulation in which a single carrier frequency is independently modulated by two different modulating signals.

 

42.       The trace of the peak of an AM wave which has the same shape as the modulating signal.

43.       The percentage of modulation for a maximum amplitude of information transmission is

 

44.       If the carrier of a 100% modulated AM wave is suppressed, the percentage power saving will be

 

45.       A signal other than the desired RF which when mixed with the oscillator frequency will produce the same IF.

 

46.       A superheterodyne receiver with an IF of 450kHz is tuned to a signal at 1200kHz. The image frequency is

 

 

 

 

QUIZ 4:

1. 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?

 

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

 

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

 

4.         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

 

5.         Which statement is correct?

 

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

7.         It is the basic building block of the FDM hierarchy

 

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

 

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

 

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

 

11.       A pre-emphasis circuit is a

 

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

 

13.       The receiver circuit that rids FM noise is the

 

14.       If the amplitude of the modulating signal decreases, the carrier deviation

 

15.       Which of the following is not a major benefit of FM over AM?

 

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

 

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

 

18.       A 100MHz is deviated 96 kHz by a 5 kHz signal. Calculate the modulation factor of this system.

 

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

 

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

 

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

 

 

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

 

25.       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

 

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

 

27.       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?

 

28.       Pre emphasis circuits boost what modulating frequencies before modulation?

 

29.       The primary disadvantage of FM is its

 

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

 

31.       Maximum frequency deviation of a PM signal occurs at

 

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

 

 

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

 

35.       It usually accomplishes frequency modulation in frequency division multiplexing systems.

 

36.       CDMA stands for:

 

37.       Find the deviation ratio of a 12,178 Hz FM carrier modulated by a 1,465 Hz signal

 

38.       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.

 

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

 

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

 

41.       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.

 

42.       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

 

43.       The FM produced by PM is called

 

 

44.       On an FM signal, maximum deviation occurs at what point on the modulating signal?

 

 

45.       What is the approximate frequency of the modulating signal having a bandwidth 54,167 Hz and a frequency deviation of 5,351 Hz?

 

46.       In PM, carrier frequency deviation is not proportional to: