Digital Modulation in Communication Systems

Innovation in modern communication systems such as mobile/cellular communication or high speed broadband network is always about advances in the digital modulation techniques. The challenge to the engineers or designers is about spectral efficiency that is measured in the unit of bits/sec/Hz. Different digital modulation techniques such as ASK, FSK, PSK or QAM are used to “squeeze” (i.e. modulate) more bits/sec of data into each Hz of radio spectral bandwidth with lower power, lower cost and yet higher resilience of the system to noise and interference. However, the fundamental concepts to digital modulation design never change much. It is about I- (in-phase) and Q (out-of-phase) signals, IQ modulation, digital filtering and multiplexing technique in the domain of frequency, time, code and geography. Equally important in the innovation is the ability to precisely measure the communication system performance in terms of frequency, power, timing and Error Vector Magnitude (EVM). This Agilent application notes revisits these important fundamental concepts of digital modulation.

To read more about the topic, please visit http://cp.literature.agilent.com/litweb/pdf/5965-7160E.pdf

Alvin Yee

DreamCatcher Principal Consultant

Mar 2010