Modern and future mobile devices must support increasingly more wireless standards and bands. Currently, multi-band coexistence is enabled by a network of discrete, off-chip components that are bulky, expensive, and narrowband. As transceivers are required to accommodate an increasing number of wireless bands, the required number of discrete components increases accordingly, resulting in greater bill of materials (BoM) cost and front-end module (FEM) area. This work focuses on design techniques to enable front-end integration and reconfigurability in multi-band radios.

In the first part of this work, we present a wideband spectrum sensing receiver with high sensitivity, wide dynamic range, and low power overhead. Reconfigurability in multi-band radios requires environmental awareness, and spectrum sensing can be used for optimal channel selection and adaptive interference suppression. The 300MHz-700MHz spectrum sensing receiver uses subsampling downconversion and digital-analog hybrid correlation to achieve -104dBm sensitivity and 84dB dynamic range for a 6MHz channel while consuming only 28mW of power. In the second part of this work, we present a wideband time division duplex (TDD) front-end with an innovative transmit/receive (T/R) switching scheme. T/R switches conventionally are off-chip components, and existing integrated designs have been narrowband or high loss. We propose a wideband integrated T/R switching technique in which the PA is re-used as an LNA during receive mode, and we demonstrate this in a 20dBm polar transmitter that can be re-purposed into a 3.4GHz-5.4GHz LNA achieving -6.7dBm P1dB and 5.1dB NF. The two systems presented in this thesis contribute key innovations towards fundamental aspects of future reconfigurable radios - greater front-end integration, wideband transceiver design, and spectrum awareness.