Modulation techniques for microwave digital radio

Radio systems that use high-level digital modulation techniques are discussed. The special features of microwave digital radio are reviewed, and techniques of modulation and demodulation, pulse spectrum shaping, and carrier and timing recovery are discussed. The factors of spectral efficiency, power efficiency, and tolerance to impairments that influence the choice of modulation are examined, and the reasons that multilevel quadrature amplitude modulation (QAM) has become the most popular type of modulation are considered. The important associated technologies for realizing such high-level modulations are discussed.