Modulation and Detection

Abstract

In this chapter, we present a number of topics surrounding modulation and demodulation. We begin by introducing system-level block diagrams of AM and FM/PM modulators and demodulators, and explaining their respective principles of operation. In particular, under the topic of AM Modulator/Demodulator, we introduce the full carrier modulator, the single sideband suppressed carrier modulator, the double sideband suppressed carrier modulator, the envelope detector, and the synchronous detector. Under the topic of FM and PM Modulator/Demodulator, we introduce the VCO as FM modulator, the indirect FM modulator, the PM modulator, the balanced discriminator FM demodulator, the quadrature FM detector, the PLL-based FM detector, the zero-crossing FM detector, and the PM demodulator. Then, under the topic of digital modulation, we introduce the concepts of Nyquist Limit, data rate, Shannon Limit, information capacity, and bandwidth efficiency, as well as specific modulation schemes, such as, binary modulation, amplitude-shift keying (BASK), frequency-shift keying (BFSK), and phase-shift keying (BPSK), differential binary phase-shift keying (DBPSK), quadrature phase-shift keying (QPSK), π/4 shifted QPSK, minimum shift keying (MSK), M-ary quadrature amplitude modulation (QAM), orthogonal frequency division multiplexing (OFDM), direct sequence spread spectrum (DS/SS), and frequency hopping spread spectrum (FH/SS). We also introduce the geometric representation of digital modulation schemes and the complex envelope form of a modulation signal.