# Electronics/Signal Modulation

## Modulation and Mixing

Put simply, modulation is the change of an electric signal based on the change in another signal. Another way to look at it practically, is the use of electric signals to carry information.

mixing is the addition and subtraction of signals.

Magic equation:
${\displaystyle cos(x)cos(y)={\frac {cos(x-y)+cos(x+y)}{2}}}$
Has strange effects on bandwidth and creates sidebands.

• morse code

## AM (Amplitude Modulation)

simpler than FM. An AM receiver detects the power of the radio wave, and amplifies changes in the power measurement to drive a speaker or earphones.

AM radio. known as medium wave. started in the 1920s. has a long enough wavelength that it diffracts and follows the curvature of the earth traveling a great distance. lower audio fidelity. used for broadcasts. Affected by light and solar flares, and works better during the night. Clear channel stations are allowed to broadcast all the time, but other stations are only allowed to broadcast during the day.

• Crystal Radio: primitive radio consists of an antenna and a diode and a speaker in parallel.

### SSB (Single SideBand)

AM with only one side band. carrier.The other one sideband block or can be use for other information tranmission. qadeerhussain99@yahoo.com

## FM (Frequency Modulation)

• VCO (Voltage Controlled Oscillator): Oscillator that is controlled by voltage.

In FM modulation, frequence of carrier signal vairy according to the audio frequency signal(Which is our actual signal).

## PM (Phase Modulation)

Change phase by modifying capacitor and inductor values. Since capacitors and inductors are 180 degrees out of phase.