Fractal wideband antennas for software defined radio, UWB, and multiple platform applications

We present examples of extremely wideband antennas with applications to SDR, UWB, and multi-service needs in wireless telecommunications. These wideband antennas are devised from fractal antenna technology. The self-similar structure has two key electrical attributes. First, it acts as loading components, which can be used to shrink the antenna size and produce a very broadband LC equivalent circuit, with relatively unchanging SWR for the overall structure. Second, the self-similarity yields individual structures of resonance over a variety of scales, which can be exploited in a prescriptive way to produce the same radiation characteristics over a very broad band. The two physical phenomena can be used to make practical wideband antennas which fall into two general classes: (1) impedance invariant wideband antennas (IIWA); and (2) frequency invariant wideband antennas (FIWA). The practical advantage of such classes of antennae is the new and enabling ability they convey to new telecom (and related) approaches. Trends towards software defined radio (SDR) now place the onus on the antenna designer to come up with a single ´one size fits all´, in which the IIWA is a compelling solution. In the case of UWB and other regimes, a single antenna with frequency invariant characteristics is the key, and possible with the FIWA. Such FIWA may also include actual notching of undesired frequencies.