Analog Communication
61 articles • Complete guide
Revive AM, FM, SSB, noise analysis, receivers, and pulse modulation – still essential for radio & legacy systems.
See waveforms change in real time and finally understand why FM sounds so good. Interactive AM/FM modulators, noise simulator, virtual labs, quizzes coming soon.
Curriculum
Select an article below to start learning
Amplitude Modulation
AM, DSB-SC, SSB, VSB, modulators and demodulators
Amplitude Modulation Basics
Definition, modulation index, time domain equation.
AM Frequency Spectrum
Carrier, upper and lower sidebands, bandwidth.
AM Power Relations
Carrier power, sideband power, modulation efficiency.
AM DSB-FC
Double sideband full carrier, classic AM generation.
AM DSB-SC
Suppressed carrier, balanced modulator, power saving.
AM SSB
Single sideband, filter method, phase shift method.
VSB Modulation
Vestigial Sideband, TV transmission application.
AM Modulators
Square law modulator, switching modulator circuits.
AM Demodulators
Envelope detector, synchronous detector.
Costas Loop
Carrier recovery for DSB-SC.
Frequency Modulation
FM, PM, Carson rule, generation, detection
FM Basics
Frequency deviation, modulation index, narrowband vs wideband.
Bessel Functions in FM
Spectrum analysis, sideband amplitudes, carrier null.
Carson's Rule
Bandwidth estimation, B = 2(df + fm).
PM Basics
Phase modulation equation, modulation index.
Narrowband FM
Approximation to AM, phasor representation.
Indirect FM Generation
Armstrong method, frequency multipliers.
Direct FM Generation
Varactor diode modulator, VCO.
FM Demodulation Basics
Slope detector, balanced slope detector.
Foster-Seeley Discriminator
Phase shift discriminator operation.
Ratio Detector
Amplitude limiting property.
PLL Demodulator
Phase Locked Loop as FM detector.
Pre-emphasis and De-emphasis
SNR improvement, time constants.
Stereo FM
Multiplexing L+R and L-R signals.
Noise Analysis
Thermal, shot, flicker noise, SNR calculations
Noise Taxonomy
External vs Internal, Shot, Thermal, Flicker, Burst noise.
Thermal Noise
Johnson-Nyquist noise voltage, bandwidth dependence.
White Noise
Power spectral density, autocorrelation.
Signal to Noise Ratio
Input SNR, Output SNR, SNR in dB.
Noise Figure
Definition F, relation to noise temperature Te.
Friis Formula
Cascaded noise figure calculation.
Equivalent Noise Temperature
System temperature, antenna temperature.
Noise in AM Systems
Figure of merit, coherent detection SNR.
Noise in FM Systems
Figure of merit, capture effect, threshold effect.
FM Threshold Extension
FMFB, PLL extension methods.
Receiver Architectures
TRF, superheterodyne, direct conversion
Receiver Parameters
Sensitivity, Selectivity, Fidelity.
TRF Receiver
Tuned Radio Frequency receiver, selectivity issues.
Superheterodyne Receiver
Mixer, IF amplifier, image frequency.
Image Frequency Rejection
Selection of IF, RF filter role.
Double Conversion
Two IF stages for selectivity and image rejection.
Direct Conversion Receiver
Zero-IF, homodyne, advantages and DC offset issues.
Automatic Gain Control
AGC principle, simple AGC circuit.
Tracking and Alignment
Local oscillator padding, trimming.
Pulse Modulation
PAM, PWM, PPM, PCM, delta modulation
Sampling Theorem
Nyquist rate, aliasing, reconstruction.
Natural vs Flat Top Sampling
Aperture effect.
PAM
Pulse Amplitude Modulation.
PWM
Pulse Width Modulation, generation and detection.
PPM
Pulse Position Modulation.
PCM Basics
Pulse Code Modulation, quantization levels.
Quantization Noise
Uniform vs Non-uniform quantization.
Companding
A-law, Mu-law compression.
Delta Modulation
1-bit quantization, slope overload, granular noise.
Adaptive Delta Modulation
Variable step size ADM.
DPCM
Differential Pulse Code Modulation.
Analog vs Digital
Comparison, hybrid systems, applications
Other Topics
Broadcasting, radio systems, legacy systems
Communication Channels
Wireline, optical fiber, wireless, satellite.
Link Budget
Friis transmission equation, path loss, fade margin.
FDM
Frequency Division Multiplexing hierarchy.
TDM
Time Division Multiplexing, T1/E1 frames.
Television Basics
Scanning, composite video signal.