Modulation Calculator

Signal Modulation

Modulation encodes information onto a high-frequency carrier wave by varying amplitude (AM), frequency (FM), or phase. The modulation index quantifies how strongly the message signal affects the carrier.

Formulas

Amplitude modulation index:

$$\mu_a = \frac{A_m}{A_c}$$

AM bandwidth for a single tone:

$$\text{BW} = 2 f_m$$

Frequency modulation index and Carson's rule bandwidth:

$$\mu_f = \frac{\Delta f}{f_m}, \quad \text{BW} = 2(\Delta f + f_m)$$

See also the Baud Rate Calculator for digital transmission rates.

Frequently Asked Questions

What is a good AM modulation index?

For AM broadcast, μₐ between 0 and 1 avoids over-modulation distortion. 100% modulation means μₐ = 1.

Why is FM modulation index often above 1?

FM index β = Δf/fₘ can be any positive value. Higher β improves noise immunity but needs more bandwidth.

What is Carson's rule?

Carson's rule estimates FM bandwidth as BW ≈ 2(Δf + fₘ), covering most significant sidebands for moderate β.

AM vs FM sound quality?

FM generally has better sound quality and noise rejection but requires more bandwidth than AM.

What are Aₘ and A꜀?

Aₘ is the peak amplitude of the message (modulating) signal and A꜀ is the peak amplitude of the unmodulated carrier.

Report

Signal Modulation

Formulas

Frequently Asked Questions

Related Tools

Recent Visits