Analyze carrier-message relationships with practical AM calculator outputs. Track envelope limits, efficiency, and sideband frequencies. Download results, review examples, and visualize waveform behavior instantly.
This amplitude modulation calculator helps you evaluate how a carrier signal changes when a message signal varies its amplitude. It is useful for radio theory, communication systems, electronics practice, and signal analysis work. By entering carrier amplitude, message amplitude, carrier frequency, message frequency, load resistance, and plot settings, you can quickly inspect both waveform behavior and numerical performance.
The calculator determines the modulation index, percentage modulation, sideband frequencies, transmission bandwidth, carrier power, sideband power, total transmitted power, envelope limits, efficiency, and angular frequencies. These values are central to understanding whether an AM signal is operating normally or entering over modulation. When the modulation index stays at or below one, the envelope remains valid for simple demodulation. When it exceeds one, the envelope can cross zero and introduce distortion in envelope detector systems.
The plotted waveform gives a clear view of the AM signal and its upper and lower envelope boundaries. This visual check makes it easier to see how modulation depth changes the transmitted pattern. The page also includes export options, so you can save numerical results to CSV or generate a PDF summary for reports, class notes, or design documentation.
1. Modulation Index: m = Am / Ac
2. Modulation Percentage: Modulation % = m × 100
3. Upper Sideband Frequency: USB = fc + fm
4. Lower Sideband Frequency: LSB = fc - fm
5. Bandwidth: BW = 2fm
6. Carrier Power: Pc = Ac² / (2R)
7. Each Sideband Power: Psb = Pc × m² / 4
8. Total Power: Pt = Pc × (1 + m² / 2)
9. Efficiency: η = [m² / (m² + 2)] × 100
10. AM Signal: s(t) = Ac[1 + m cos(2πfmt)] cos(2πfct)
Here, Ac is carrier amplitude, Am is message amplitude, fc is carrier frequency, fm is message frequency, and R is load resistance.
| Carrier Amplitude | Message Amplitude | Carrier Frequency (Hz) | Message Frequency (Hz) | Load Resistance (Ω) | m | Bandwidth (Hz) | Total Power (W) |
|---|---|---|---|---|---|---|---|
| 10 | 5 | 1000 | 100 | 50 | 0.5 | 200 | 1.125 |
| 8 | 8 | 2000 | 150 | 75 | 1 | 300 | 0.64 |
| 12 | 15 | 1500 | 120 | 60 | 1.25 | 240 | 2.1375 |
The modulation index shows how strongly the message signal changes the carrier amplitude. A value below or equal to one is usually preferred for standard envelope detection.
Standard single-tone amplitude modulation creates one upper sideband and one lower sideband. Each sideband sits one message frequency away from the carrier, so total bandwidth becomes 2fm.
Over modulation happens when the message amplitude becomes larger than the carrier amplitude. The envelope can cross zero, creating distortion and inaccurate recovery in simple demodulators.
The modulation process combines carrier and message frequencies. This creates sum and difference frequency components, called the upper sideband and lower sideband.
Total transmitted power includes carrier power plus both sidebands. The sidebands carry the information, while the carrier mainly supports easier detection and tuning.
Yes, as long as you stay consistent. The same amplitude basis should be used for both carrier and message values, because the modulation index depends on their ratio.
Load resistance is required for power calculations. Without it, the calculator can still describe frequency behavior, but it cannot estimate carrier and transmitted power correctly.
The graph shows the AM waveform and its envelope boundaries. It helps you visually confirm modulation depth, compare waveform shape, and spot possible over modulation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.