Development of a Band-Selectable Smart Antenna, 10-9543

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Principal Investigators
Mike Pilcher
Travis R. Thompson
Stephen A. Cerwin

Inclusive Dates:  04/01/05 - 04/01/06

Background - Software-Defined Radio (SDR) represents an evolving technology that has generated great interest in the wireless communications industry and should provide many opportunities for contracts in the future. Traditionally, radio system designs have incorporated mostly specialized hardware components. This specialization has forced the development of a variety of different and incompatible wireless devices. SDR systems use software to implement functions previously performed by hardware components. Consequently, SDR systems can offer many benefits over previous hardware-intensive designs such as multimode operation, the use of fewer discrete components, less expensive product upgrades, over-the-air reconfiguration, increased interoperability, rapid time-to-market, improved spectrum efficiency, increased flexibility, and widespread connectivity.

One aspect commonly overlooked in the SDR community is the necessity of specialized antennas. If SDR systems are to communicate in any number of frequency bands, it is not simply a matter of reprogramming a frequency synthesizer. Radio Frequency (RF) components from frequency translation, to amplification, to transduction (in this case from electrical current to an electromagnetic wave) must also be able to operate in any band selected. Broadband antennas exist (as do mixers, amplifiers, and other RF components), but they are generally very large, thus not mobile. The goal of this research is to develop an antenna that can operate in a range of frequency bands [targeted for the military Joint Tactical Radio System (JTRS)], which is also electrically small.

Approach - This research is leveraging a previous internal research and development project by starting with the electrically small cylindrical meander antenna. This antenna topology is already patented by the Institute. The research team will experiment with changing the number of turns and adding variable amounts of loading to the turns of the antenna to change the fundamental resonance. The team will also experiment with structures that are simultaneously lumped elements at lower frequencies and transmission line elements at higher frequencies.

Accomplishments - The team has begun simulation with loaded dipoles (a traditional and well-understood band-selectable, electrically small smart antenna) and the SwRI cylindrical meander. The team has demonstrated in simulation the ability to change the resonance of the cylindrical meander by changing the number of turns and the ability to change the resonance of a loaded dipole by changing the loading. The next step is to experiment with changing the loading on the turns of the cylindrical meander.

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