This project is divided into two main parts. The first part is to design and implement the basic PSK modulation scheme and obtain the phase shifted output. The second part is to model and assess the performance of QPSK modulation scheme using ADS tools and apply to CDMA technology. Code Division Multiple Access (CDMA) is a wireless communication system that uses the QPSK modulation scheme for digital transmission. The QPSK modulator is analyzed to meet the data rate, bandwidth, bit error rate and other requirements for CDMA. CDMA is very useful for applications that require high capacity and flexibility for multi rate systems such as those in mobile communications networks and wireless systems. It is different than those traditional methods, which only allocate either frequency or time but allows multiple users to occupy the given band at the same time and frequency. Besides, it uses a "spread spectrum" technology that enable every channel to use the full available spectrum. CDMA is also used in applications like optical CDMA and multiple antennas CDMA.