• Analog voice data must be translated into a series of binary digits before they can be transmitted in digital transmission system. One means of doing this is called pulse amplitude modulation (PAM). • The process of converting analog signal to digital is also known as A_to_D conversion or A/D conversion. The circuit does the conversion known as A/D converter. In analog modulation (continuous wave modulation), some parameter of a sinusoidal carrier wave is varied continuously in accordance with the message signal. . | CSN200 Introduction to Telecommunications, Winter 2000 Lecture-22 Digital Transmission Digital Transmission of Analog Data (Baseband Transmission): • Analog voice data must be translated into a series of binary digits before they can be transmitted in digital transmission system. One means of doing this is called pulse amplitude modulation (PAM). • The process of converting analog signal to digital is also known as A_to_D conversion or A/D conversion. The circuit does the conversion known as A/D converter. In analog modulation (continuous wave modulation), some parameter of a sinusoidal carrier wave is varied continuously in accordance with the message signal. In digital modulation (pulse modulation), some parameter of a pulse train is varied in accordance with the message signal. Pulse modulation: Pulse modulation can be subdivided into two groups: 1. Analog pulse modulation • A periodic pulse train is used as the carrier wave, and some parameter (amplitude, duration, or position) of each pulse is varied in a continuous manner in accordance with the corresponding sample value of the message signal. • Information is transmitted basically in analog form (multiple amplitude), but the transmission takes place at discrete times. 2. Digital Pulse modulation • The message signal is represented in a form that is discrete in both time and amplitude. • Information is transmitted in digital form as a sequence of coded pulses. The transmission takes place at both discrete amplitude and discrete times. Digital Pulse modulation or the use of coded pulses for the transmission of analog information represents a basic application of digital communications. Sampling: • It is an operation that is basic to digital signal processing and digital communication. • Through the use of sampling, an analog signal is converted to its digital form. • To obtain either form of pulse modulation we start with sampling. Sampling is the process of taking samples (amplitude) of an analog signal that
