I want to know the basic/fundamental difference between AM and FM radio. Why nowadays FM radio has replaced AM and has become more popular?
Electronic – the basic difference between AM and FM radio
Modulationradio
Related Solutions
A signal that is phase-shift modulated with some continuous signal f will have the same waveform as one which is frequency-shift modulated with the derivative of f. Likewise, a signal that is frequency-modulated by some signal f will have the same waveform as one which is phase-modulated by the integral of f. Note that in some cases, it may not be practical to take the integral or derivative of f, so some signals can only be meaningfully represent phase modulation and others may only meaningfully represent frequency modulation.
Even though the waveforms of a frequency-modulated signal and phase-shift-modulated signal may look similar, however, there's often another important distinction. Phase-shift modulated signals are often modulated relative to some other reference signal. In some cases, the reference may be a signal sent on another wire. In other cases, the reference may be a signal which was sent at an earlier time on the same wire. In NTSC video, for example, every scan line starts with a few cycles of a 3.579545Mhz reference sine wave. Colors later in the line will be encoded by waves that have a certain phase relationship to that reference wave. Yellow, for example, will be represented by a wave whose phase matches the reference; blue will be represented by a wave 180 degrees out of phase. Red and green are represented by waves +/- 90 degrees out of phase. Note that all solid colors are be represented by the same frequency; the only difference between them is the phase relative to the reference wave.
Very nice study.
Slides:
An Analysis of Power Consumption in a Smartphone
Conclusions:
Major consumers:
display & cell radio
WiFi power low in most situations
CPU can be significant
Future power driver
Where power is not going:
- RAM
- Audio
- Bluetooth
- Storage
Korean study.
27 slides - results differ somewhat from above.
Energy tradeoffs in smartphone apps
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Best Answer
Short answer: FM is far less susceptible to disturbance of the signal.
This is an AM modulated signal. The contours are the baseband signal which we recover by demodulation. Notice that there's a spike in the signal, which may be caused by a thunderstorm for instance.
This is the demodulated signal. The demodulator doesn't "know" that the spike isn't actual part of the signal, so it can't remove it, and the listener will hear a tick in the symphony she's listening to.
FM has a constant amplitude, and the demodulator won't be fooled by spikes in amplitude since it will detect variations in frequency.
This is an FM signal. The baseband signal determines the change in frequency of the carrier. Notice that the spike doesn't change the frequency, so it won't be audible after demodulation.