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# What will be the effect of doubling the modulating frequency on modulation index of phase and frequency modulation?

## What will be the effect of doubling the modulating frequency on modulation index of phase and frequency modulation?

When the modulation frequency is doubled, the modulation index is halved and the modulation voltage remains constant, the modulation system is frequency modulation .

What happens when you increase the modulating frequency?

In frequency modulation, the carrier amplitude remains constant, but its frequency is changed in accordance with the modulating signal. Specifically, the higher the amplitude of the information signal, the greater the frequency change. As a result, the bandwidth occupied by an FM signal is enormous.

### When the modulating frequency is doubled the modulation index is?

halved
When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant.

What will be change in the bandwidth if modulation frequency is doubled?

When modulating signal amplitude is doubled, the frequency deviation becomes 2 x 75 = 150 kHz. Thus, the bandwidth is almost doubled.

#### What is the highest modulating frequency?

Therefore, we need to use the relation among bandwidth, highest modulating frequency and number of amplitude modulated broadcast stations to find the correct answer. In the question, it is given that bandwidth is \$300kHz\$ and for the highest modulating frequency is \$15kHz\$.

How is modulation frequency calculated?

Commercial FM signals use a peak frequency deviation of ∆f = 75 kHz and a maximum baseband message frequency of fm = 15 kHz. Carson’s rule estimates the FM signal bandwidth as BT = 2(75 + 15) = 180 kHz which is six times the 30 kHz bandwidth that would be required for AM modulation.

## What happens to the modulation index when the frequency deviation is doubled?

In FM, when frequency deviation is doubled, then (a) modulation us halved.

What is the frequency of modulating signal?

Amplitude Modulation vs Frequency Modulation Amplitude Modulation index ranges from 0 to 1, requires low bandwidth in the range of 10 kHz, operates in medium and high frequency ranges of 535 to 1705 Kilohertz, has a simple circuit with only two side bands, and receives low quality signals with poor sound quality.

### How do you calculate modulating frequency?

The frequency modulation is known as a constant bandwidth system and an example of this system is given below.

1. Δf = 75 KHz fm = 500 Hz BWFM = 2 [75 + (500/1000)] KHz = 151.0 KHz.
2. Δf = 75 KHz fm = 5000 Hz BWFM = 2 [75 + (5000/1000)] KHz = 160.0 KHz.
3. Δf = 75 KHz fm = 10000 Hz BWFM = 2 [75 + (10000/1000)] KHz = 170.0 KHz.

How to calculate the modulation index of FM?

Write the expression for instantaneous voltage of frequency modulated wave. V AM = V c sin (w c t +m f sin w m t). Question 30. Define modulation index of FM. Modulation index is the ratio of maximum frequency deviation to the modulation signal frequency.

#### What is the bandwidth of a frequency modulation?

Given a frequency modulation index of μFM = 3 and a modulating frequency fm = 4000 Hz, using Carson’s rule estimate the bandwidth of the advanced mobile phone system (AMPS) signal modulated on a carrier fc = 869 MHz. In this case, neither the upper or lower bound condition on the bandwidth as stated in (2.17) is satisfied.

How is the required bandwidth of FM calculated?

According to Carson’s rule, bandwidth of FM is given by 2 (Δf+ fm) where Δf is the deviation in frequency and fm is the frequency of sinusoidal signal. The required bandwidth is therefore calculated as Q.21. The audio signal having frequency 500Hz and voltage 2.6V, shows a deviation of 5.2KHz in a Frequency Modulation system.

## How is the modulation index of an AM wave defined?

Modulation index of an AM wave is the ratio of amplitude of modulating signal (V m) to the amplitude of the carrier signal (V c ). Question 8. Define percent modulation for an AM wave. Percent modulation for an AM wave is its modulation index multiplied by 100. Question 9. How many side bands are present in AM? Two. Question 10.