This work focuses on the subject of image rejection in wireless receiver design, which is important as a high level of integration is demanded in mobile terminals. In this book, the image rejection problems in various receiver architectures which are suitable for high level of integration, including image-reject, direct conversion and low IF architectures, are studied. The fundamental source of the limitation of the image rejection in these receivers is the imbalance between their in-phase (I) and quadrature (Q) channels, which becomes more problematic when the receivers are of wideband. Besides traditional methods, this book provides alternative solutions to the problem, which falls into two broad types. The first type refers to new circuits that produce less I/Q imbalance. This includes high performance switched-capacitor Hilbert transformers and precise quadrature sampling circuits. The second type is to compensate the I/Q imbalance, which is possibly frequency-dependent, in digital domain by calibration or signal processing techniques. Design examples have been included.