Crossed-Slot Patch for Solar-Array Integration

A crossed-slot patch [2] is a microstrip antenna element that consists of four 1/4-wavelength-long sub-patches, as shown in Fig. 11. Each sub-patch has a square or slightly rectangular shape with one edge electrically shorted to the common ground plane. This electrical shorting can be accomplished by connecting the sub-patch and the ground plane either by a small, continuous, thin metallic sheet or by many metallic shorting pins (8 to 10 per edge). The four sub-patches are shorted at four sequentially located edges. The four sub-patches also are excited at four sequentially located 50-ohm input impedance points by four coaxial probes. These four feed probes then are combined behind the ground plane by a hybrid circuit that provides the needed 0°, 90°, 180°, and 270° electrical phases. The four sub-patches are separated from and supported above the ground plane by a one-inch-thick non conducting honeycomb panel. Since a sub-patch radiates only from its three open edges, foreign low-profile objects (metallic or nonmetallic) can be placed on top of each sub-patch without significantly disturbing the radiation characteristics of the antenna. Consequently, solar cells can be placed on top of the four sub-patches of the crossed-slot patch antenna, as shown in Fig. 10. Although all open edges of the four sub-patches radiate, the major portions of the radiated fields originate at the central crossed slots. Since each slot radiates with a cosinusoidal amplitude distribution with the maximum field located at the slot center, the crossed-slot patch has a very small effective radiating aperture, which leads to a relatively broad far-field beam.

The antenna, measured at a representative frequency of 410 MHz, has a peak gain of 4.5 dB. From these patterns, it is clear that the low-profile crossed-slot patch antenna does radiate a relatively broad beam and is capable of integrating with the solar array [Full PDF].