Frequency Modulation and Phase Modulation Quiz

A 4 kHz message signal causes an FM carrier signal to have a frequency deviation of +-20 kHz. What is the MI ? MI = fcd/fm

• a. 80

• b. 5

• c. 0.2

• d. 24

For an FM signal, what does the term frequency deviation mean ?

• a. the center frequency plus the modulation percentage .

• b. the change in frequency from the center frequency

• c. the modulation index times the center frequency

• d. the message signal frequency plus or minus the center frequency

Frequency modulation (FM) and phase modulation (PM) are subcategories of what type of modulation ?

• a. amplitude modulation

• b. SSB modulation

• c. angle modulation

• d. double sideband (DSB) modulation

What does the term quadrature mean?

• a. a frequency difference of 45 kHz

• b. a phase difference of 90°

• c. shifting the phase of a signal

• d. limiting the phase difference to 45°

In PM, the carrier frequency deviates with changes in what parameter(s) of the message signal ?

• a. Modulation Index

• b. Frequency only

• c. Amplitude only

• d. Frequency and Amplitude

How do you adjust the amplitude of the VCO-LO oscillator signal ?

• a. by turning the NEGATIVE SUPPLY knob on the base unit

• b. by turning the potentiometer knob on the MODULATOR

• c. by turning the POSITIVE SUPPLY knob on the base unit

• d. by turning the potentiometer knob on the VCO-LO circuit block

How is the carrier signal suppressed in the output of a balanced modulator ?

• a. It is suppressed by the NEGATIVE SUPPLY voltage.

• b. It is suppressed by the POSITIVE SUPPLY voltage

• c. It is suppressed by the null potentiometer in the message signal input

• d. It is suppressed by adjusting the VCO-LO potentiometer

What is the function of a discriminator?

• a. It restores high-frequency message signals to their proper relationship with the lower frequencies.

• b. It recovers the message signal from frequency deviations of the FM carrier signal.

• c. it provides the necessary amplification and volume control

• d. It tunes the FM receiver to the desired frequency.

What are the output signals of the quadrature detector's phase detector ?

• a. signals equal to half and three times the FM center frequency

• b. the sum frequency of the inputs and the FM center frequency

• c. FM signals that are 900 out of phase

• d. the sum frequency of the inputs and a dc voltage that varies with the message signal

In FM, the carrier frequency deviates with changes in what parameter(s) of the message signal ?

• a. Phase angle and amplitude

• b. Frequency only

• c. Amplitude only

• d. Frequency and Amplitude