Contents
- 1 How is NBFM converted to WBFM?
- 2 How is narrowband generated?
- 3 What is the bandwidth of WBFM?
- 4 What is the frequency of audio modulation?
- 5 Which method is best for frequency demodulation?
- 6 What is the bandwidth of the PM?
- 7 What are the types of frequency modulation?
- 8 How can frequency modulation reduce noise?
- 9 Which is the block diagram of WBFM wave?
- 10 How is the modulation index of a NBFM wave calculated?
How is NBFM converted to WBFM?
To convert a NBFM to WBFM we have to increase the frequency deviation and carrier frequency of the NBFM. The multiplication factor is found by dividing the final frequency deviation i.e. 75000 by initial frequency deviation i.e. 25 Hz and we get the number 3000.
How is narrowband generated?
Usually, narrowband FM signals are used in low-cost two-way radio communication systems like a walkie-talkie. To generate the narrowband FM signal, we will be using the standard equation of the FM signal and pass the value of the frequency modulation index (b) less than unity.
What is difference between NBFM & WBFM?
When spectrum efficiency is important, Narrowband FM (NBFM) is used but when better signal quality is required, Wideband FM (WBFM) is used at the expense of greater spectrum usage. The term WBFM is used in applications where the modulation index is equal to or larger than 1.
What is the bandwidth of WBFM?
Commercial WBFM broadcasts occur in the VHF range, between 88 and 108 MHz. The carrier frequencies start at 88.1 MHz and are separated by 200 KHz intervals. The maximum audio bandwidth allowed is 15 KHz and the deviation is limited to +/- 75 KHz.
What is the frequency of audio modulation?
Difference between Amplitude Modulation and Frequency Modulation
| Amplitude Modulation | Frequency Modulation |
|---|---|
| The AM frequency ranges from 535 kHz – 1705 kHz | The FM frequency ranges from 88 MHz – 108 MHz in the higher spectrum |
| The modulation index of AM ranges from 0 to 1 | The modulation index of FM is higher than 1 |
Why is FM more immune to effects of noise?
FM signal is having fixed amplitude and phase and frequency is variable. Noise is generally uniformly spread across the spectrum and varies randomly in amplitude. The change in amplitude can modulate the signal and can be picked up in an AM system. So FM is more immune to noise.
Which method is best for frequency demodulation?
A simple and effective FM demodulation technique involves a high-pass filter (for FM-to-AM conversion) followed by an AM demodulator. A high-pass-filter-based FM demodulator is preceded by a limiter to prevent amplitude variations from contributing error to the demodulated signal.
What is the bandwidth of the PM?
For small amplitude signals, PM is similar to amplitude modulation (AM) and exhibits its unfortunate doubling of baseband bandwidth and poor efficiency. For a single large sinusoidal signal, PM is similar to FM, and its bandwidth is approximately.
Why FM has infinite bandwidth?
Like AM, FM also produces sidebands. But unlike AM, which produces a single pair of sidebands for each frequency in the modulating signal, the FM process produces an infinite number of pairs of sidebands for each frequency in the information signal. As a result, the bandwidth occupied by an FM signal is enormous.
What are the types of frequency modulation?
There are two different types of frequency modulation used in telecommunications: analog frequency modulation and digital frequency modulation. In analog modulation, a continuously varying sine carrier wave modulates the data signal.
How can frequency modulation reduce noise?
In FM the amplitude of the frequency modulation can be increased without increasing the power at all. In addition, since the amplitude of the FM signal remains constant, amplitude limiters can be set close to the FM signal amplitude and thus very effectively reduce impulse noise.
How to generate a WBFM signal from NBFM?
In a recent related QA ( How to generate WBFM from NBFM ), it is shown how × 2 frequency multiplication doubles both the carrier frequency ω c as well as frequency deviation Δ f. So for a × 64 is implemented as six stages of × 2 multiplier. Similarly × 128 is implemented as 7 stages of × 2 multiplier.
Which is the block diagram of WBFM wave?
The block diagram of generation of WBFM wave is shown in the following figure. This block diagram contains mainly two stages. In the first stage, the NBFM wave will be generated using NBFM modulator. We have seen the block diagram of NBFM modulator at the beginning of this chapter. We know that the modulation index of NBFM wave is less than one.
How is the modulation index of a NBFM wave calculated?
Where, ‘n’ is the multiplication factor. If NBFM wave whose modulation index β is less than 1 is applied as the input of frequency multiplier, then the frequency multiplier produces an output signal, whose modulation index is ‘n’ times β and the frequency also ‘n’ times the frequency of WBFM wave.
When to use a frequency multiplier for NBFM?
If NBFM wave whose modulation index $\\beta$ is less than 1 is applied as the input of frequency multiplier, then the frequency multiplier produces an output signal, whose modulation index is ‘n’ times $\\beta$ and the frequency also ‘n’ times the frequency of WBFM wave.