ed circuit in 1958 used in combina- tion with these devices provided the basis for the power-efficient and spectrally efficient radio transceivers that have powered the wireless industry for the past 50 years and the cellular indus- try for the past thirty years. However, 50 years on these RF functions are still typically realised as discrete components, existing alongside rather than inside present integrated circuits. 4.5.2 Present-Day Issues of RF Device Integration Present-day issues of RF device integration are as much mechanical as electrical. Radio reception starts with an antenna. Antennas in hand-held devices are either electrical dipoles, small loops, helical, meander antennas or patch antennas. Patch antennas, also known as planar internal antennas are in- creasingly popular as embedded antennas. Typically, these are used with grounding that shifts the antenna resonance to a lower frequency with a slot added to increase the electrical length, a design known as planar inverted F antennas (PIFA). Antenna size can also be reduced by using dielectrics with a high dielectric constant. Another option is to use fractal-based antenna patterns to use whatever space is available reasonably effectively. However, any antenna, when constrained within a space that is significantly less than a quarter wavelength of its centre frequency will be inherently inefficient and sensitive to de tuning, for example by hand capacitance effects. The following are significant contributors to this loss of efficiency. The imperfect impedance match of the antenna - especially at the band edges - gives rise to significant reflection loss particularly at lower frequencies (850/900/800/700 MHz). Ohmic and dielectric losses convert useful RF energy into heat in the antenna and any associated matching circuits. RF currents may be coupled into other components within the handset, dissipating RF energy inside the phone. Candy bar, clam shell and slider phones all have similar but different challenges in terms of antenna efficiency. Some an