A new acquisition technique for carrier recovery with QAM signals

Describes a frequency error detector (FED) for all modulation systems using quadratic modulation schemes, such as 16-QAM, 64-QAM, 256-QAM and so on. Its main advantage is the very high resistance to all kinds of signal faults such as distortions, level errors or noise. Simultaneously, it permits a high acquisition range to be achieved (more than Δf/fs=5% in noise-free environments). Typical applications of the new FED are data transmissions over fading channels without using preambles or other additional aids for carrier acquisition. For this reason, very economical XPIC structures become possible. The method described here can be regarded as an advanced development of the FEDs presented by Sari and Moridi (1988)