UC Santa Barbara

This dissertation provides an overview of challenges of modern wireless communications including frequency spectral efficiency, multiple-path fading, hardware complexity and un-utilized white spaces in the spectrum. By using Direct-Sequence Spread-Spectrum (DSSS) codes it is possible to overcome some of those challenges. Full-Duplex (FD) systems are improved with DSSS techniques by increasing the rejection of the Self- Interference (SI) form co-located transmitter (TX) as well as rejecting the TX replicas before and post the antenna. Out of band jammres are rejected as well relaxing the linearity requirements of the receive (RX) chain. Carrier Aggregation (CA) is possible with DSSS at a much lower power consumption and hardware complexity as well as much faster settling time. Spectrum Sensing (SS) to detect unused frequency bands is achieved with DSSS at lower power consumption. A frequency diversity technique is introduced to overcome the fading of wireless channel. To support theoretical analysis, experimental verification with CMOS SOI is discussed in detail and several designs are included.