Radio Frequency Direct-Digital QPSK Modulators in CMOS Technology

ii In this thesis, novel direct-digital Quadrature Phase Shift Keying (QPSK) modulators are proposed in low-cost Complimentary Metal Oxide Semiconductor (CMOS) technology for radio frequency (RF) wireless applications. Direct-digital architectures have attracted much attention recently as they potentially offer significant cost savings and performance benefits. A new direct-digital QPSK modulator concept is introduced where the carrier is modulated directly by digital data using Pass-Transistor Logic (PTL) circuits for a small size and low power consumption. The concept is demonstrated through the design of an L-band modulator followed by an enhanced tunable S-band version. The proposed L-band modulator first generates all four quadrature phases of the carrier by using a 90 ° resistor-capacitor, capacitor-resistor (RC-CR) phase shifter followed by two 180 ° active baluns. One signal from the in-phase components an