Antennas are a critical component in communications, radar and direction finding systems, interfacing between the RF circuitry and the environment. RF circuitry is often manufactured using printed circuit board (PCB) technology, and numerous engineering and commercial advantages are realized by integrating the RF antennas directly on the same printed circuit boards as the circuitry. Doing so improves product quality, reliability, and form-factor compactness, while at the same time lowering manufacturing costs by eliminating fabrication steps, connectors, and mechanical supports.
There is a variety of PCB antennas, including microstrip patch antennas that radiate perpendicularly to the PCB, and printed Vivaldi and Yagi antennas that radiate parallel to the surface of the PCB. These antennas have dimensions on the order of the half-wavelength of the operating frequency, and at lower frequencies consume considerable PCB area.
A popular PCB edge-mountable antenna is the ‘inverted-F’ antenna. The antenna forms a quarter-wave resonator, with the transmission line parallel to the card edge, and having the shorting stem as the primary radiating element. The inverted-F antenna is smaller and more compact than a simple monopole antenna, and can be easily impedance-matched without additional components simply by proper positioning of the feed stem relative to that of the shorting stem.
Because of close proximity to the ground plane, however, PCB RF antennas typically have a narrow-band resonance, which is disadvantageous when wideband performance is needed, such as for ultra-wideband (UWB) operation in the 3.1-10.6 GHz band.
Thus, it would be desirable to have a compact profile PCB-edge antenna with improved wide-band matching characteristics. This goal is met by embodiments of the present invention.