The modulation technique in which frequency of the carrier wave is changed with respect to the modulating wave is called:
Frequency modulation
Frequency Modulation Explained
Modulation is a crucial process in electronic communication that involves varying one or more properties of a periodic waveform, called the carrier wave, with respect to a signal containing information, known as the modulating wave (or message signal). This process allows the information to be transmitted efficiently over long distances. The question specifically asks about a modulation technique where the frequency of the carrier wave is changed with respect to the modulating wave.
Understanding Different Modulation Techniques
Let's delve into the various modulation techniques mentioned in the options to clearly identify the correct one based on the question's definition.
| Modulation Type | Characteristic Varied on Carrier Wave | Description |
|---|---|---|
| Amplitude Modulation (AM) | Amplitude | In Amplitude Modulation, the amplitude (strength) of the high-frequency carrier wave is varied in direct proportion to the instantaneous amplitude of the modulating wave (message signal). The frequency and phase of the carrier wave remain constant. |
| Frequency Modulation (FM) | Frequency | In Frequency Modulation, the instantaneous frequency of the high-frequency carrier wave is varied in direct proportion to the instantaneous amplitude of the modulating wave. The amplitude of the carrier wave remains constant. This precisely matches the description provided in the question. |
| Phase Modulation (PM) | Phase | In Phase Modulation, the phase of the high-frequency carrier wave is varied in direct proportion to the instantaneous amplitude of the modulating wave. While similar to FM, PM directly modifies the phase, which indirectly results in frequency changes. The amplitude remains constant. |
| Pulse Code Modulation (PCM) | Digital representation (bits) | Pulse Code Modulation is a digital method used to represent an analog signal. It involves three main steps: sampling the analog signal, quantizing the samples into discrete levels, and then encoding these quantized levels into a binary (digital) code. Unlike AM, FM, and PM, which are analog modulation techniques, PCM is a digital modulation scheme. |
The core of the question lies in identifying the modulation technique where the frequency of the carrier wave is changed with respect to the modulating wave. Based on the characteristics discussed:
- Frequency Modulation (FM) directly involves varying the frequency of the carrier signal in response to the amplitude of the modulating signal. This makes it the perfect match for the given description.
- Amplitude Modulation (AM) varies the amplitude, not the frequency.
- Phase Modulation (PM) varies the phase, although it is closely related to FM.
- Pulse Code Modulation (PCM) is a digital encoding process, fundamentally different from analog frequency, amplitude, or phase variations of a carrier wave.
Benefits of Frequency Modulation
Frequency Modulation (FM) is widely used in radio broadcasting due to its superior noise immunity compared to Amplitude Modulation (AM). Since the information is encoded in frequency variations rather than amplitude variations, FM signals are less susceptible to noise and interference, which often manifest as amplitude disturbances. This leads to higher fidelity audio reception, especially for music and speech.
Therefore, the modulation technique in which the frequency of the carrier wave is changed with respect to the modulating wave is called Frequency Modulation.
Important Questions from Frequency Modulation
The range of frequency generated by VHF oscillator is -
If f mis modulating frequency and m fis modulation index, then by the Carson's rule, the bandwidth of an FM signal at the input of a conventional discriminator will be:
The appropriate value of modulation index β for transition between narrow band and wide band FM is considered as:
Which of the following is NOT the advantage of frequency modulation ?
What is the modulation index in a frequency modulated signal with a modulating frequency of 500 Hz and frequency deviation of 10 kHz?
