Improved radiation pattern for 28 GHz omni-directional quasi-optical oscillator array

For emerging distribution type systems, such as personal communication systems (PCS), wireless video, or wireless local area networks (WLAN), transmitters are needed which can broadcast with large beamwidths. It is for these applications that the array described was built. This twelve-element quasi-optical array was created to provide 360 degree coverage and require only a single low-voltage DC power supply, through which the data, is modulated onto the 28 GHz carrier. It radiates 140 mW into the desired polarization and has a tuning bandwidth of 500 MHz, across which the oscillators remain phase-locked. Because of its planar nature, using coplanar-waveguide (CPW) and integrated antennas, it could easily be fabricated monolithically. Unfortunately, these planar, endfire antennas do not have sufficient gain in the h-plane, which results in the vertical beamwidth being larger than desired for most applications. This paper shows that the difficulty can be overcome by adding a pair of metal disks, one above and one below the array.