ABSTRACT
In transceiver systems, misalignments in the quadrature modulator feeding a nonlinear high-power amplifier can produce distortion products that lead to spectrum leakage into adjacent channels. This chapter discusses the elimination of these distortion products. Quadrature modulation is a convenient and flexible way to produce nearly any type of waveform and has been in use for decades. Ideal quadrature modulators generate single continuous wave (CW) tone that can be used in radio frequency (RF) systems. Using vectors to represent signals is a useful way to visualize the effect of the RF impairments on quadrature modulator performance. The chapter illustrates the simplified block diagram of the proposed system accomplishing the image band rejection. It proposes the method for cancelling the local oscillator (LO) leakage in a quadrature modulator. DC offsets are added to the phase (I) and quadrature (Q) paths to cancel the offsets that exist to create the LO leakage.
