Broadband microstrip hybrid network

Abstract

The aim of my final year project is to design and fabricate a microwave network by using mircostrip lines mainly. Having a broadband operation frequency range of that network is the project’s primary requirement. Narrow band of 90o hybrid and 45o phase shifter are common elements in microwave circuit. Design and fabrication above 2 elements with broadband properties is one of the achievements. A Butler Matrix, one of the important and useful devices in wireless communication, can be built by combination of these 2 broadband elements with special configuration. A 4x4 Butler Matrix, consisting of 4 broadband 90o 3-section hybrids and 2 broadband 45o novel phase shifters, has been designed, fabricated and measured respectively. The entire 4x4 Butler Matrix is made of microstrip lines on a substance with dielectric constant as 2.65. The overall dimensions are 11.5cm (L) x 15cm (W) x 1.5mm (H). Furthermore, the butler matrix has phase errors within 8.9o, has coupling ratios larger than -8.3dB, and all ports’ return loss are better than 10dB over the frequency range from 3.16 GHz to 4.78GHz, centred at 3.97GHz. For that frequency range, the percentage bandwidth is 40.8%.