Content area
Full Text
A two layer dual-band switched beam system operating at two separate frequency bands is proposed. This system consists of a dual-band 4 × 4 Butler matrix at the bottom layer and a dual-band microstrip antenna array at the top layer. The antenna array is fed by a Butler matrix to produce four beams that can be tilted in different four directions. A modified Butler matrix consists of branch line couplers and -45° phase shifters without any crossovers. The system provides a tilted beam of ±14° and ±47° at 3.95 GHz and ±10° and ±28° at 7.3 GHz.
Introduction: The recent advancement in the area of wireless communication systems has increased the demand for multiband systems. There are two ways to take advantage of a multibeam antenna system: an adaptive antenna array and a switched beam system [1]. An adaptive array forms an infinite number of patterns that are adjusted in real time using a variety of new signal-processing algorithms. Switched beam systems can form multiple fixed beams with heightened sensitivity in particular directions and switch their beams in different directions throughout space by changing the phase difference of the signals used to feed the radiating elements [1].
A Butler matrix is an n × n beam-forming network and has been used in switched beam systems to make multibeams. The conventional Butler matrix consists of branch-line couplers, phase shifters and crossovers. In this Letter, a modified Butler matrix is used for a beam switching system. This matrix is composed of branch-line couplers and a phase shifter without any crossovers [2]. Therefore, this matrix expects a simple design of planar Butler matrix with reduced phase error due to crossovers.
Recently, a dual-band beam switching array has been presented. In [3], the dual-band antenna array is fed by a broadband Butler matrix. This system uses four diplexers and two antenna arrays for dual-band beam switching operation. A diplexer is used to connect the broadband Butler...