Code-division multiple access (CDMA) techniques are expanding rapidly in the 3G mobile communications, such as wideband code-division multiple access (W-CDMA) because they can increase channel capacity and data rate substantially, and meanwhile reduce the multi-path fading effects and power consumption effectively. A quadrature modulator and an upconverter are the essential components used in a W-CDMA transmitter. This book is devoted to HBT (Heterojunction Bipolar Transistor) MMIC (Monolithic Microwave Integrated Circuit) designs for W-CDMA applications, and at the same time evaluates and discusses the package and PCB (Printed Circuit Board) effects on the designed HBT MMICs.