This project is a simple FM radio receiver built using analog components and an RF tuner stage.
It demonstrates the principles of frequency modulation (FM) reception, the electromagnetic theory,
and the electronics needed to detect and play broadcast FM audio.

FM (Frequency Modulation) encodes audio into a radio wave by varying its frequency
while keeping the amplitude constant.

• FM signals are electromagnetic waves traveling at the speed of light (c = 3×10⁸ m/s).
• A broadcast station transmits a carrier frequency in the VHF band (88–108 MHz).
• The antenna captures a small portion of this wave and converts it into a weak AC signal.
• The circuit processes this to recover the original audio waveform.

If the carrier wave is:

c(t) = A_c · cos( 2π f_c t )

In FM, the instantaneous frequency varies with the audio signal m(t):

s(t) = A_c · cos[ 2π f_c t + β · sin( 2π f_m t ) ]

Where:

• f_m = maximum frequency of the audio signal
• β = modulation index = Δf / f_m
• Δf = frequency deviation (max shift from f_c)

Typical broadcast values:

• Δf ≈ 75 kHz
• f_m ≤ 15 kHz

1. Antenna & LC Tuner
Captures the FM signal and selects the desired frequency using:

f_res = 1 / ( 2π √(LC) )

2. RF Amplifier
Boosts the weak signal without adding too much noise.

3. Mixer & Local Oscillator
Shifts the RF signal to an Intermediate Frequency (IF) (10.7 MHz).

4. IF Amplifier & Limiter
Amplifies and removes amplitude variations (FM carries info in frequency only).

5. FM Demodulator
Converts frequency changes into voltage variations (audio signal).

6. Audio Amplifier
Boosts the audio to drive a speaker.

graph LR
    A[Antenna] --> B[LC Tuned Circuit]
    B --> C[RF Amplifier]
    C --> D[Mixer]
    E[Local Oscillator] --> D
    D --> F[IF Filter]
    F --> G[IF Amplifier]
    G --> H[Limiter]
    H --> I[FM Discriminator]
    I --> J[Audio Amplifier]
    J --> K[Speaker]