[EST] Frenzel Q&A - Chapter 5: Frequency Modulation Circuits

Varactor diode

Another name for a VVC is __________.

Dielectric

The depletion region in a junction diode forms what part of a capacitor?

decrease

Increasing the reverse bias on a varactor diode will cause its capacitance to __________.

pF

The capacitance of a varactor diode is in what general range?

R1, R2

In Fig. 5-3, the varactor diode is biased by which components?

Decreases

In Fig. 5-3, if the reverse bias on D1 is reduced, the resonant frequency of C1 __________.

Small

The frequency change of a crystal oscillator produced by a varactor diode is __________.

Carrier

A phase modulator varies, the phase shift of the __________.

LC resonant circuit

The widest phase variation is obtained with a(n) __________.

Deviation control

In Fig. 5-7, R4 is the __________.

Frequency multiplier

The small frequency change produced by a phase modulator can be increased by using a(n)

VXO

A crystal oscillator whose frequency can be changed by an input voltage is called a(n) __________.

Crystal

Which oscillators are preferred for carrier generators because of their good frequency stability?

Foster-Seeley discriminator

Which of the following frequency demodulators require an input limiter?

Quadrature detector

Which discriminator averages pulses in a low-pass filter?

PLL

Which frequency demodulator is considered the best overall?

Positive

In Fig. 5-8, the voltage at point A when the input frequency is below the FM center frequency is __________.

De-emphasis

In Fig. 5-8, R3 and C6 form which kind of circuit?

directly proportional to frequency deviation

In Fig. 5-10, the voltage across C6 is __________.

Zero crossing detector

In a pulse averaging discriminator, the pulses are produced by a(n) __________.

206 MHz

Problem Solving: A reactance modulator looks like a capacitance of 35 pF in parallel with the oscillator-tuned circuit whose inductance is 50 μH and capacitance is 40 pF. What is the center frequency of the oscillator prior to FM?

It is a VCO.

Which of the following is true about the NE566 IC?

Differential peak detector

An FM demodulator that uses a differential amplifier and tuned circuits to convert frequency variations into voltage variations is the __________.

Pulse width

The output amplitude of the phase detector in a quadrature detector is proportional to __________.

2 MHz

The input to a PLL is 2 MHz. In order for the PLL to be locked, the VCO output must be __________.

Jump to the free-running frequency

Decreasing the input frequency to a locked PLL will cause the VCO output to __________.

Lock range

The range of frequencies over which a PLL will track input signal variations is known as the __________.

Capture range

The band of frequencies over which a PLL will acquire or recognize an input signal is called the __________.

Bandpass filter

Over a narrow range of frequencies, the PLL acts like a __________.

Low-pass filter

The output of a PLL frequency demodulator is taken from __________.