The second course in this seven-course series focuses on the fundamentals of communication theory. OF particular importance is the concept of modulation and demodulation. We will learn that the information that is being transmitted and received by a communication device often occupies frequencies from DC to a few megahertz (gigahertz in the case of data). Effective communication over a long distance often requires frequency-upconversion of the information, which is called baseband signal, to high frequency using another signal called carrier. The information can be featuring different attributes of the carrier such as its amplitude, phase, or frequency. Placing the information on the amplitude of the carrier leads to the notion of amplitude modulation (AM). Likewise, in the case that the phase or frequency of the carrier varies by the baseband signal, we will achieve phase modulation (PM) and frequency modulation (FM). Modern communication systems all employ digital modulation. Digital modulation allows the use of digital signal processing techniques to vastly improve spectral efficiency during signal transmission. To more efficiently use the spectrum to transmit data, thus increasing the information rate, the information bits can be formed into "symbols." Each symbol is comprised of several bits. The symbol transmission allows for sending more information bit at specific instances of time. The symbol formation together with frequency upconversion constitutes the digital modulation. In this course, we will learn about different digital modulation techniques including amplitude, phase, and frequency shift keying, and quadrature amplitude modulation (QAM). Widely used advanced techniques such as orthogonal frequency division multiplexing (OFDM) will also be discussed in this course.
1. Basics of modulation
2- Benefits of employing modulation in a communication system
Modulated signals are bandpass, and thus, the RF radio handling them exhibits bandpass frequency response. In this lecture, we will learn how to represent a bandpass RF signal, and why to fully characterize an RF signal, we must know both its in-phase and quadrature components.
An overview of
1. amplitude modulation (AM),
2. phase modulation (PM), and
3. frequency modulation (FM)
This lecture provides examples of
1. an AM modulator circuit;
2. a non-coherent AM demodulator circuit;
3. an FM modulator circuit; and
4. an FM demodulator circuit
This lecture describes the fundamentals of
- baseband digital transmission;
- pulse amplitude modulation (PAM); and
- return-to-zero (RZ) vs. non-return-to-zero (NRZ)
This lecture goes over the following crucial concepts:
- Intersymbol interference (ISI)
- Eye diagram
- Nyquist condition for zero-ISI and ideal Nyquist channel
The following important topics will be covered in this lecture:
- Nyquist condition for zero ISI
- Practical problems with ideal Nyquist channel
- Pulse shaping
- Raised cosine pulses
In this lecture, we learn the basics of quadrature representation of bandpass digital modulation signals and will get ourselves familiar with digital modulation techniques
This lecture will go over some of the widely used digital modulation techniques:
- Binary phase-shift keying (BPSK) modulation and constellation
- Spectral efficiency
- Quadrature PSK (QPSK) modulation and constellation
- M-ary PSK modulation and constellation
- Quadrature amplitude modulation (QAM)
In this lecture, we will learn important topics in wireless communication, such as
- Multi-path propagation
- Orthogonal frequency division multiplexing (OFDM)
- FDM vs. OFDM
- Advantages and disadvantages of OFDM
The following concepts will be introduced:
- BER definition
- BER comparison of different modulation schemes
- EVM definition
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