1. Title and aim
Double-Sideband Full-Carrier Amplitude Modulation Index and Precision Diode Envelope Demodulation. Determine the modulation index (m) of a double-sideband full-carrier (DSB-FC) AM wave and evaluate the demodulated audio output voltage linearity across modulation depths from 10% to 100%.
2. Abstract
Laboratory evaluation of Double-Sideband Full-Carrier Amplitude Modulation Index and Precision Diode Envelope Demodulation was conducted across six calibrated telecommunication setpoints. Measured telemetry was linearized, yielding a correlation coefficient R² = 1.000000. The experimental parameter Carrier Peak Voltage Sensitivity V_c was estimated as 10.0000 V, comparing against the reference benchmark of 10.0000 V with a relative percentage deviation of 0.0000%.
3. Apparatus and fixed settings
- AM & Envelope Demodulation Telecommunication Workstation: Provides regulated RF/baseband excitation, precision impedance-matched test fixtures, and low-noise interconnection for sideband power distribution, trapezoidal pattern analysis & diagonal clipping distortion.
- 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 am & envelope demodulation.
- Synthesized Vector RF Signal Generator (9 kHz – 3 GHz): Delivers calibrated, low-phase-noise continuous-wave and modulated carrier signals to establish modulation index 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.
- Environmental Conditions: 23.5 °C ambient, 45% relative humidity, 101.3 kPa atmospheric pressure.
- Excitation Calibration: Locked to OCXO reference oscillator with frequency stability < 1 × 10⁻⁸.
4. Theory and graph choice
Determine the modulation index (m) of a double-sideband full-carrier (DSB-FC) AM wave and evaluate the demodulated audio output voltage linearity across modulation depths from 10% to 100%.
Plotting Modulation index m on the horizontal axis and Demodulated audio voltage V_demod (V) on the vertical axis yields a linear characteristic whose slope verifies the AM & Envelope Demodulation analytical model.
5. Method
- 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.
- Configure the synthesized RF signal generator and baseband source to the specified baseline parameters. Calibrate the modulation index using the precision digital multimeter and oscilloscope.
- Increment the modulation index systematically across the experimental range (0.1 to 1.0 ratio), logging the resulting demodulated audio output voltage v_demod after signal settling.
- 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.
- Execute both ascending and descending parameter sweeps across the device under test (DUT) to detect any thermal drift, detector non-linearity, or oscillator pulling.
- 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.
6. Observations and calculation table
All communication observations use strictly controlled 64-bit IEEE 754 precision buffers. Residuals are computed relative to the ordinary least-squares regression line.
| No. | Modulation Index m (ratio) | Demodulated Audio Output Voltage V_demod (V) | Modulation index m | Demodulated audio voltage V_demod (V) | Fitted y | Residual |
|---|---|---|---|---|---|---|
| 1 | 0.1 | 1.0 | 0.1000 | 1.0000 | 1.0000 | 0.0000 |
| 2 | 0.3 | 3.0 | 0.3000 | 3.0000 | 3.0000 | 0.0000 |
| 3 | 0.5 | 5.0 | 0.5000 | 5.0000 | 5.0000 | 0.0000 |
| 4 | 0.7 | 7.0 | 0.7000 | 7.0000 | 7.0000 | 0.0000 |
| 5 | 0.9 | 9.0 | 0.9000 | 9.0000 | 9.0000 | -0.0000 |
| 6 | 1.0 | 10.0 | 1.0000 | 10.0000 | 10.0000 | -0.0000 |
Download the sample observations (CSV) ↓
7. Worked calculation for one observation
8. Graph, gradient and final calculation
Circular markers represent empirical communication observations. The solid line represents the ordinary least-squares linear fit.
Σ(x − x̄)² = 0.6083
Σ(x − x̄)(y − ȳ) = 6.0833
m = Σ(x − x̄)(y − ȳ) / Σ(x − x̄)² = 10.00000000
b = ȳ − mx̄ = -2.368e-15
Carrier Peak Voltage Sensitivity V_c = 10.00000 V
9. Uncertainty and comparison
Percentage difference = |estimate − theoretical value| / |theoretical value| × 100 = 0.0000%.
For n = 6 observations, Σresidual² = 1.323e-29; s² = Σresidual²/(n − 2). Gradient standard error = √[s²/Σ(x − x̄)²] = 2.331e-15. Intercept standard error = √[s²(1/n + x̄²/Σ(x − x̄)²)] = 1.549e-15.
Propagating the fit parameters yields a fit standard error of 2.331e-15 V, with an ideal coefficient of determination R² = 1.000000.
Instrumental and regression uncertainty for AM & Envelope Demodulation is constrained within 0.02% of full-scale calibration standards.
10. Result and discussion
Theoretical reference value: 10.0000 V
Experimental observations across all test trials demonstrate strict agreement with theoretical communication channel models. OLS regression slope evaluated to 10.000000 with intercept -0.000000, validating the governing equation V_demod = 10.0000 · m with R² = 1.000000.
11. Precautions and limitations
- Never exceed the maximum rated RF input power (+20 dBm / 100 mW) of the spectrum analyzer or vector network analyzer input mixer.
- Ensure all coaxial cable shields and equipment chassis are securely bonded to a common low-impedance earth ground to prevent 50/60 Hz hum pickup.
- When handling optical fiber facets and high-frequency microwave components, avoid direct eye exposure to laser apertures and protect microstrip lines from electrostatic discharge (ESD).
- Verify that 50-ohm through-terminations are securely fastened to unused oscilloscope and analyzer ports to eliminate high-frequency signal reflections.
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.
12. Conclusion
The experimental determination of Double-Sideband Full-Carrier Amplitude Modulation Index and Precision Diode Envelope Demodulation confirmed the theoretical model within an experimental uncertainty of 0.0000%. The standard calibration protocol ensures reproducible laboratory characterization.
In-Depth Technical Supplement & Signal Processing Derivation
1. Title and Objective
Double-Sideband Full-Carrier Amplitude Modulation Index and Precision Diode Envelope Demodulation. Determine the modulation index (m) of a double-sideband full-carrier (DSB-FC) AM wave and evaluate the demodulated audio output voltage linearity across modulation depths from 10% to 100%. This formal laboratory report documents experimental data acquisition, mathematical model calibration, regression analysis, error propagation, and physical parameter extraction for am & envelope demodulation.
2. Abstract
An experimental investigation of am & envelope demodulation was conducted using high-precision telecommunication instrumentation across six systematic setpoints of modulation index ranging from 0.1 to 1.0 ratio. Measured demodulated audio output voltage v_demod data were logged using 6.5-digit digital multimeters, digital storage oscilloscopes, and RF spectrum analyzers. Ordinary least-squares regression yielded an empirical calibration line of V_demod = 10.0000 · m with a coefficient of determination R² = 1.000000. The derived experimental parameter Carrier Peak Voltage Sensitivity V_c was evaluated as 10.0 V, demonstrating complete agreement with theoretical benchmark expectations within 0.02% experimental error.
3. Experimental Apparatus & Standard Settings
- AM & Envelope Demodulation Telecommunication Workstation: Provides regulated RF/baseband excitation, precision impedance-matched test fixtures, and low-noise interconnection for sideband power distribution, trapezoidal pattern analysis & diagonal clipping distortion.
- 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 am & envelope demodulation.
- Synthesized Vector RF Signal Generator (9 kHz – 3 GHz): Delivers calibrated, low-phase-noise continuous-wave and modulated carrier signals to establish modulation index 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.
- Environmental Ambient Conditions: Ambient laboratory temperature 23.5 ± 0.5 °C; relative humidity 45 ± 5%; atmospheric pressure 101.3 kPa.
- Excitation Calibration Settings: Synthesized RF carrier oscillator locked to an internal oven-controlled crystal reference (OCXO) with frequency stability < 1 × 10⁻⁸.
4. Theory & Graphical Coordinate Selection
According to the governing principles of am & envelope demodulation, the communication response follows the linear transformation:
To evaluate the intrinsic physical parameter (Carrier Peak Voltage Sensitivity V_c), the experimental data are plotted with Modulation index m on the horizontal abscissa and Demodulated audio voltage V_demod (V) on the vertical ordinate. The gradient of the resulting least-squares linear line directly yields the parameter magnitude.
5. Step-by-Step Experimental Method
- 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.
- Carrier & Modulating Signal Synthesis: Configure the synthesized RF signal generator and baseband source to the specified baseline parameters. Calibrate the modulation index using the precision digital multimeter and oscilloscope.
- Systematic Telemetry Acquisition & Setpoint Stepping: Increment the modulation index systematically across the experimental range (0.1 to 1.0 ratio), logging the resulting demodulated audio output voltage v_demod after signal settling.
- 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.
- 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.
- 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.
6. Raw Experimental Observations & Data Tabulation
All experimental observations were recorded under steady-state thermal and electromagnetic equilibrium. The table below summarizes the recorded telemetry across the experimental domain.
| Trial # | Modulation Index m (ratio) | Demodulated Audio Output Voltage V_demod (V) | Transformed x | Transformed y | Residual |
|---|---|---|---|---|---|
| 1 | 0.1 | 1.0 | 0.100 | 1.000 | 0.000 |
| 2 | 0.3 | 3.0 | 0.300 | 3.000 | 0.000 |
| 3 | 0.5 | 5.0 | 0.500 | 5.000 | 0.000 |
| 4 | 0.7 | 7.0 | 0.700 | 7.000 | 0.000 |
| 5 | 0.9 | 9.0 | 0.900 | 9.000 | 0.000 |
| 6 | 1.0 | 10.0 | 1.000 | 10.000 | 0.000 |
7. Worked Calculation for Representative Observation
For Trial 3 (Modulation Index = 0.5 ratio):
y_3 = m \cdot x_3 + b = V_de0.5od = 10.0000 · 0.5
Derived Parameter Value = 10.0 V
8. Regression Analysis, Gradient & Parameter Extraction
Ordinary least-squares (OLS) linear regression was performed across the six observation pairs. The regression statistics are summarized below:
Intercept b = Calculated baseline offset
Correlation Coefficient R² = 1.000000
Standard Error of Slope SE_m = ±0.00005 V
9. Uncertainty Propagation & Comparison with Reference
Measurement uncertainty was calculated following the ISO Guide to the Expression of Uncertainty in Measurement (GUM). Type A uncertainty evaluated from observation residuals yielded u_A = 0.00015. Type B instrumental calibration uncertainty from the 6.5-digit multimeter was u_B = 0.00035. The combined expanded uncertainty at a 95% confidence interval (coverage factor k = 2) is:
\[ U = k \cdot \sqrt{u_A^2 + u_B^2} = 2 \cdot \sqrt{(0.00015)^2 + (0.00035)^2} = \pm 0.00076\text{ V} \]The experimental estimate of 10.0 V agrees with the theoretical reference value (10.0 V) within an absolute deviation of 0.012%, well within the expanded uncertainty band.
10. Engineering Discussion & Phenomenological Interpretations
The experimental results confirm the theoretical behavior of am & envelope demodulation. The strict linearity observed across all six test points validates the assumption of linear, low-distortion communication channel characteristics. Harmonic distortion and phase noise were effectively suppressed through proper impedance matching and high-Q resonant filtering. The minor residual fluctuations observed are attributable to thermal Johnson–Nyquist noise and quantization resolution in the digital storage oscilloscope.
11. Industrial Applications & Telecommunication Practice
The communication engineering principles demonstrated in this laboratory form the core foundation of numerous modern telecommunication and RF systems, including:
- Cellular & Wireless Communications (5G/6G & Wi-Fi 7): Multi-carrier OFDM modulation, massive MIMO beamforming, quadrature amplitude modulation (1024-QAM), and low-density parity-check (LDPC) coding.
- Satellite & Aerospace Telemetry: Deep-space communication links, Doppler shift tracking, phased array radar systems, and direct sequence spread spectrum (DSSS) GPS/Galileo navigation.
- High-Speed Fiber-Optic Backbones: Coherent optical transceivers, wavelength division multiplexing (DWDM), semiconductor laser modulation, and low-latency transoceanic links.
- Broadcast & Digital Media Infrastructure: Digital audio/video broadcasting (DAB/DVB-T2), emergency communications, and software-defined radio (SDR) platforms.
12. Conclusion & Recommendations
The experimental investigation of Double-Sideband Full-Carrier Amplitude Modulation Index and Precision Diode Envelope Demodulation was completed with complete success. The linear regression model verified the governing transfer equation with R² = 1.000000. All RF safety protocols, 50-ohm termination standards, and precision measurement guidelines were strictly observed. For future investigations, automated GPIB/VISA telemetry acquisition and anechoic chamber testing are recommended to characterize ultra-wideband frequency responses.
This report presents simulated benchmark observations generated for demonstration and academic instruction purposes. When submitting coursework, replace all numerical values with your actual laboratory workbench observations.