Antenna design strategy and demonstration for software-defined radio (SDR)
Antennas are a key enabling technology for software-defined radio (SDR). Although software is extremely flexible, SDR's potential is limited by antenna size and performance. In this paper, we review typical antenna miniaturization techniques and fundamental theories that limit antenna size and performance including operational bandwidth, gain (or range), and radiation pattern. Possible antenna design strategies are discussed to meet the desired specifications in SDR based on observations from the limit theories. The application of strategies to enable multiband (resonant), continuous multiband (frequency independent), and instantaneous, ultra-wideband antennas are discussed qualitatively. Advantages, disadvantages, and design trade-off strategies for different types of antennas are compared from a system-level perspective. A design example for a compact ultra-wideband (UWB) antenna is presented for a software-defined platform. The example involves a direct-conversion radio developed in Wireless@ VT that uses a Motorola RFIC having a 100 MHz-6 GHz operational frequency range with a 9 kHz-20 MHz channel bandwidth. The example antenna covers frequencies from 450 MHz to 6 GHz instantaneously with approximately 5-dBi realized gain over a finite-size ground plane, including return loss and omni-directional coverage.
software-defined radio (sdr) antenna miniaturization ultra-wideband antenna fundamental limits on antennas antenna gain antenna bandwidth