Electronics & Communication / FM & Foster-Seeley Demodulation
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LABORATORY 02 · ELECTRONICS & COMMUNICATION

Frequency Modulation Index and Foster-Seeley Discriminator Linearity

Investigate frequency modulation sensitivity, Carson's bandwidth rule, and demodulation discriminator output voltage across frequency deviations from 10 kHz to 75 kHz. Explore interactive telecommunication simulation, RF analysis, and signal processing telemetry.

ANALOG MODULATION · DIGITAL BASEBAND · PASSBAND MODULATION · ANTENNAS & RF · OPTICAL FIBER · DSP

Your virtual electronics & communication engineering laboratory.

DISCRIMINATOR OUTPUT VOLTAGE V_OUT—
RF INSTRUMENTATION TELEMETRY

Ready to sample with Frequency Deviation = 35.0 kHz.

35.0 kHz
Excitation locked to low-phase-noise synthesized reference oscillator.

Adjust Frequency Deviation, then execute telecommunication RF/baseband acquisition.

Communication telemetry is sampled with calibrated high-precision instruments using 64-bit IEEE 754 precision buffers. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity modulation, channel, and spectral analysis.

Communication engineering assumptions and boundary limits

Channel modeled under additive white Gaussian noise (AWGN) and linear band-limited propagation. Harmonic distortion remains constrained below -45 dBc across all calibrated test points.

Laboratory apparatus & testing equipment.

FM & Foster-Seeley Demodulation Telecommunication Workstation

Provides regulated RF/baseband excitation, precision impedance-matched test fixtures, and low-noise interconnection for bessel carrier nulls, carson's rule bandwidth & s-curve discriminator response.

6.5-Digit True-RMS Digital Multimeter (Keysight / Fluke)

Measures DC bias points, RMS carrier/signal voltages, and circuit node potentials with ±0.0035% baseline accuracy.

Four-Channel Digital Storage Oscilloscope (200 MHz, 2 GSa/s)

Captures high-frequency RF envelopes, baseband eye diagrams, constellation patterns, and transient responses for fm & foster-seeley demodulation.

Synthesized Vector RF Signal Generator (9 kHz – 3 GHz)

Delivers calibrated, low-phase-noise continuous-wave and modulated carrier signals to establish frequency deviation conditions.

High-Dynamic-Range RF Spectrum Analyzer (9 kHz – 3.6 GHz)

Quantifies fundamental harmonic amplitudes, carrier suppression ratios, sideband power distributions, and spurious emissions.

Matched 50-Ohm Coaxial Interconnects & Attenuator Set

Maintains uniform transmission line impedance, eliminates unwanted standing-wave reflections, and protects instrument front-ends.

FOLLOW THE METHOD

A reason behind every step.

Investigate frequency modulation sensitivity, Carson's bandwidth rule, and demodulation discriminator output voltage across frequency deviations from 10 kHz to 75 kHz. Standardized parameter settings: 15.0, 25.0, 35.0, 45.0, 60.0, 75.0 kHz.

  1. Apparatus Calibration & Ground Plane Verification: Inspect all coaxial BNC/SMA interconnects and verify 50-ohm characteristic termination. Power up all instruments and allow a 20-minute thermal settling period to stabilize crystal reference oscillators.
  2. Carrier & Modulating Signal Synthesis: Configure the synthesized RF signal generator and baseband source to the specified baseline parameters. Calibrate the frequency deviation using the precision digital multimeter and oscilloscope.
  3. Systematic Telemetry Acquisition & Setpoint Stepping: Increment the frequency deviation systematically across the experimental range (15.0 to 75.0 kHz), logging the resulting discriminator output voltage v_out after signal settling.
  4. Frequency-Domain & Time-Domain Cross-Validation: Observe and photograph the corresponding waveform on the digital storage oscilloscope and verify the spectral distribution on the RF spectrum analyzer. Verify that harmonic distortion remains below -45 dBc.
  5. Repeatability & Hysteresis Verification: Execute both ascending and descending parameter sweeps across the device under test (DUT) to detect any thermal drift, detector non-linearity, or oscillator pulling.
  6. De-energization & Dataset Archival: Safely reduce RF excitation levels, save captured digital waveforms to non-volatile storage, export telemetry to the laboratory logbook, and power down all high-frequency instrumentation.
YOUR NOTEBOOK · 0 OBSERVATIONS

Turn measurements into telecommunication engineering insight.

See a complete example report ↗

Points are your recorded observations. The solid regression line validates FM & Foster-Seeley Demodulation mathematical scaling.

LINEAR REGRESSION FIT · y = mx + b
V_out = 0.0500 · Δf
#Frequency Deviation Δf (kHz)Discriminator Output Voltage V_out (V)Frequency deviation Δf (kHz)Discriminator output voltage V_out (V)

No readings yet. Execute a communication trial and record it.

CHECK YOUR UNDERSTANDING

Explain what the communication metrics mean.

Question 1: In the experimental investigation of FM & Foster-Seeley Demodulation, the primary dependent variable measured is:

Question 2: The mathematical relationship governing FM & Foster-Seeley Demodulation is modeled as:

Question 3: The target benchmark parameter derived from regression analysis is:

Question 4: Which instrument provides the most accurate visualization of spectral harmonics and carrier sidebands in the frequency domain?

THEORY AND ELECTROMAGNETIC CONTEXT

Electronics & Communication Engineering background & physical principles.

Investigate frequency modulation sensitivity, Carson's bandwidth rule, and demodulation discriminator output voltage across frequency deviations from 10 kHz to 75 kHz.

V_out = 0.0500 · Δf

Communication systems rely on Fourier spectral decomposition, Shannon channel capacity, and electromagnetic propagation theory.