In case of PAM the amplitude of sampled signal varies in accordance with info. signal so it is a type of analog pulse modulation.
But in case of PWM and PPM, since the PWM or the PPM sampled signal varies in width or the position, but still is a digital signal which is transmitted. Then why PWM and PPM are still called a type of ANALOG pulse moudulation????

 

The information signal is represented by timing variations, in a proportional manner. The timing variations are thus analogs of the original signal. There is no conversion of the information into a numerical form.

The PWM or PPM signals have constant amplitude and could be transmitted by a logic gate, but this does not alter the situation.