 including for example, switch and tuneable filter functions. Tuneable structures integrated with other active components can be used to implement wideband power amplifiers, broadband tuneable matching networks and adaptive antenna matching. Similarly, MEMS devices may be used to vary the load impedance of power amplifiers SO that they will work efficiently at varying power levels over a relatively wide range of frequencies. MEMS also potentially address the problem of duplexing, particularly in 3G phones. In GSM, duplexing, (the separation of transmit and receive channels within a specific frequency band) can be achieved with a front-end switch as the phones are not transmitting and receiving at the same time. In WCDMA, HSPA and LTE, transmission takes place at the same time as reception. Adding a band means another duplex filter needs to be added that has an associated direct cost and an associated indirect cost (takes up additional board space and needs matching components). There are presently proposals for MEMS-based active digitally tuneable duplexers, also known as digital duplexers, which may potentially resolve these band-specific 3G specific duplex cost overheads. These techniques together will enable a transition towards single-chip software-defined radios that will help eliminate many present spectrally specific device and design issues. Five years ago when this study was written these devices were claimed to be ready for market. However, five years later their application in terms of functional replacement of traditional RF components is limited for reasons that we explore in Chapter 5. This highlights a pervasive disconnect in our industry. Spectral allocation and auction policy and technology policy, or rather the absence of technology policy known as 'tech- nology neutrality' is generally based on an assumption that technology is actually capable of solving all problems within defined time scales. There are several problems with this problem. Some performance metrics are defined by the basic rules