5.5 Pulse sequence modulation (pulse modulation)

Along with the modulation of harmonic carriers in various radio engineering devices, they find the modulation of pulse sequences (the so-called pulse modulation). The exact name of the type of pulse modulation is determined by the parameter of the pulse sequence, which is subjected to modulation. The form of the carrier pulse range *** and the modulation products of a sequence of pulses during modulation with a harmonic signal are shown in Figure 5.6.

When modulating the amplitude of a sequence of pulses according to the law of a transmitted message with their constant duration, amplitude-pulse modulation takes place (AIM - Figure 5.6, c). When changing the duration of a sequence of pulses at their constant amplitude, it is said that pulse-width modulation takes place (PWM - Figure 5.6, d). With a change in the temporal position of the pulses, they speak of a time-pulse modulation (VIM - figure 5.6, d).

In communication systems, they often deal with pulse-code modulation (PCM - Figure 5.6, f). In this case, the value of the analog baseband signal at each clocked time is converted into a digital code. The modulation product is a sequence of pulses corresponding to this code in a given time interval. PCM signal is one form of digital signal representation.

Fig. 5.6 Modulation of the pulse sequence:
a) carrier sequence of pulses;
b) modulating signal;
c) pulse-amplitude modulation;
d) pulse-width modulation;
e) time pulse modulation;
e) pulse code modulation

In radio communication, pulse modulation is often an intermediate stage in the preparation of signals for transmission in the combined types of modulation.
In a radio communication technique, pulse-modulated collisions are generated at intermediate stages of the formation of transmitted signals with combined modulation types.