Direct Write Techniques for Fabricating Unique Antennas
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Technetronics, Inc., 5202-2 North Richmond Hill Road, Stillwater, OK, U.S.A. 74075. Raytheon Systems Corp., P.O. Box 12248, St. Petersburg, FL, U.S.A. 33733-2248.
ABSTRACT The current fabrication methods used to produce many antennas are limited by variances in the precision and skill levels of individual laborers. These variances slow production and often create inconsistent results. As radio-frequency transmitter and receiver design moves towards higher operating frequencies, the physical dimensions of the supporting antennas decrease. Smaller sizes add new complexities to the fabrication of these antennas. Several designs that may be considered high-performance antennas are difficult to reproduce; many times, they cannot be fabricated at all due to the sophisticated patterning and precision necessary for successful function. Direct-write technologies provide the tools necessary to fabricate unique patterns in two and three dimensions. A demonstration of a directly written antenna, constructed from a silver-based thick-film paste pen-deposited onto cylindrical alumina substrates, is presented for review. INTRODUCTION Market trends in wireless communications and Global Positioning System (GPS) devices are requiring increasingly smaller, more affordable, and higher-performance antennas. To design small antennas to operate at lower frequencies requires mostly an empirical approach. Established theoretical analysis and simulation tools can provide the basis for a new antenna design. However, for these tools to be effective, several simplifying assumptions must be made about the design. The antenna must still be fabricated and tested to demonstrate its true performance. For the design process to be efficient, rapid-prototyping methods are required. The ability to efficiently write an antenna directly onto a device substrate can significantly reduce design time during the iterative process described above. The direct-write method described herein advances the field of rapid prototyping, specifically, as applied to such antenna designs as the half-wavelength cylindrical coupled slotline (CCS) antenna of Culver, King, and Weller [1], or the fed-slot and folded-slot CCS antennas of Scardelletti [2]. EXPERIMENT The antennas presented herein were written using the OhmCraft MicroPenTM dispensing system. They are constructed from a silver-based thick-film paste, deposited onto cylindrical alumina substrates (1.27 cm diameter), then oven-fired after deposition. The thickness of the silver conductor film was held at 37 Am. RESULTS The direct-write deposition of half-wavelength slot antennas was demonstrated on cylindrical alumina substrates as shown in Figure 1 (next page). The radiation pattern is similar to that of a simple dipole, with the exception of a partial null that exists along one side of the 195
Mat. Res. Soc. Symp. Proc. Vol. 624 © 2000 Materials Research Society
Figure 1: Cylindrical Slot Antenna
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Figure 3: Measured E-plane Gain Pattern for the Cyl
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