What kind of input signal is used to test the amplitude linearity of a single-sideband phone transmitter?

To test the amplitude linearity of a single-sideband (SSB) phone transmitter, a two-tone audio-frequency sine wave is used. This choice is appropriate because the two-tone signal consists of two different frequencies that are evenly spaced apart. This configuration allows for a thorough examination of the transmitter's response across a range of audio frequencies.

When a two-tone signal is applied, it generates intermodulation products that can highlight any non-linear behavior in the transmitter. If the transmitter were to exhibit any distortion or amplitude nonlinearities, the output would show unexpected frequencies or variations in amplitude not present in the input, which is critical for assessing performance in communication systems.

Using a single-tone audio-frequency sine wave would not adequately test for linearity since it provides no information about how the transmitter handles more complex signals or interactions between frequencies. Similarly, square and triangular wave signals could introduce harmonics that complicate the analysis and do not provide a clear assessment of amplitude linearity as effectively as the two-tone method does. Thus, the use of a two-tone audio-frequency sine wave is the most suitable approach for testing amplitude linearity in an SSB transmitter.