Angle Modulation II

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問題一覧

Which of the following is false?

Balanced Slope Detector is two single-ended slope detectors connected in parallel and fed 90 out of phase.

The typical voltage versus frequency response curve for a Foster-Seeley discriminator.

S Curve

What occurs to a discriminator with a straight S-Curve?

less AF distortion.

Ratio Detector is relatively immune to _____ variations in its input signal.

amplitude

Ratio Detector has _______

series diode

______ is advantage of Ratio Detector.

AGC

Gated Beam Detector in TV is tuned to what frequency?

4.5 MHz

Gated Beam Detector is similar to super regenerative detector due to ______

Pulse Width Modulation

what kind of AF output does Foster-Seely Discriminator has?

varying AC

what kind of AF output does Stagger Tuned Discriminator has?

varying ac

what kind of AF output does Ratio Detector has?

varying dc

what kind of AF output does Gated Beam Discriminator has?

varying dc

It requires no tuned circuits and automatically compensates for changes in the carrier due to oscillator instability.

PLL Demodulators

Gated Beam Detector in Broadcast is tuned to what frequency?

10.7 MHz

Which of the following is false?

PLL acts like highpass filter.

It extracts the original information signal from the composite IF waveform by multiplying two quadrature signals or same frequency signals with different phases.

Quadrature Detector

Which of the following is false?

Output Amplitude of Quadrature Detector is proportional to amplitude.

It reduce the total harmonic distortion by compressing the IF frequency swing or deviation.

FLL

The ability to provide same information.

Monophonic

The ability to provide low noise and high fidelity FM music background or broadcast.

Stereophonic

The transmission in which information signal is spatially divided into two 50 Hertz to 15 kiloHertz audio channels.

Stereophonic Transmission

Process of placing two or more independent channels next to each other in the frequency domain or stacking the channels, and then modulating a single high-frequency carrier with the combined signal.

Frequency Division Multiplexing

It is used to broadcast uninterrupted music to private subscribers.

Subsidiary Communications Authority

Half-duplex, one-to-many radio communications with no dial tone.

Two Way Mobile Radio

Full-duplex, on-to-one radio telephone communications.

Mobile Telephone Service

What devices that are feed into FM station audio control?

Any of these

The maximum frequency deviation for two-way FM transmitters is typically _____ and the maximum modulating frequency is ______.

5 kHz, 3 kHz

In a FM Stereo Multiplex Transmission, _____

the difference signal modulates 38 kHz subcarrier

L plus R signals that fed to stereo FM reactance modulator and Stereo Multiplex.

Audio Frequency

L minus R signals that fed to stereo FM reactance modulator.

Double Sideband

What fed to transmitter modulator with SCA?

L minus R stereo channel occupies ______

23 kHz to 53 kHz

L plus R stereo channel occupies

50 Hz to 15 kHz

Measuring FM transmitter power uses a dummy antenna is _______

direct method

Accuracy of meter in the output stage of an FM Transmitter is ____

Frequency tolerance of FM broadcast is

2 kHz

When frequency deviates when FM is applied, it indicates _____ in transmitter.

distortion of emission

It is used with public safety service equipment.

Vertical polarization

It is used with FM broadcast station.

Horizontal polarization

It is used to prevent overloading of the IF amplifier in the receiver.

Variable sensitivity

It varies the phase of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal.

Direct Phase Modulation

The relative angular displacement or shift of the carrier phase in radians in respect to the reference phase.

Phase Deviation

Maximum phase deviation occurs at

zero crossing points

Carrier phase deviation in PM is same as carrier frequency deviation in FM. Is the statement true?

False, because phase deviation is directly proportional to modulating amplitude.

The instantaneous change in the phase of the carrier at a given instant of time and indicates how much the phase of the carrier is changing with respect to its reference phase.

Instantaneous Phase Deviation

Circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal.

Phase Deviator

Two common methods for producing direct PM are ___ and ____.

Any of these

Method where low-frequency modulated carrier can either be up or down converted to a different location in the frequency spectrum.

Heterodyne Method

Method where the modulation properties of a carrier can be increased at the same time that the carrier frequency is up-converted.

Multiplication Method

PM Receiver has voltage at the output of the _____' is directly proportional to the phase deviation at its input.

audio detector

The widest phase variation is obtained with circuit.

LC resonant

It determines the bandwidth in high index signal.

Quasi Stationary

What is the disadvantage of PM?

not reaching high modulation index due to stable oscillator.

A side frequency is not considered significant unless it has an amplitude ______ 1 percent of the unmodulated carrier amplitude.

equal to or greater than

Bessel Function of the first kind for several values of modulation index provides the number of ___ and their corresponding ____.

side frequency pairs, magnitude

A 100 MHz carrier signal is modulated by 13 kHz signal tone. If the signal differs by 45 degrees, what is the frequency deviation?

21 kHz

A carrier signal is modulated by 15 kHz tone. What is the carrier swing of the modulation index is 4?

120 KHz

What is the bandwidth if the frequency deviation is 60 kHz and modulating frequency is 25 kHz?

190 kHz

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