60 GHz Low Phase Error Rotman Lens Combined With Wideband Microstrip Antenna Array Using LTCC Technology

Abstract

This paper presents a new design technique and analysis for a microstrip Rotman lens which is feeding a wide bandwidth series-fed microstrip patch antenna array. In the proposed Rotman lens method, the length of the transmission lines does not affect the progressive phase delay. This reduces the complexity of the design and improves the performance parameters. An antenna array is utilized using open ended $\lambda /4$ stubs to support high gain, directivity, and a wide bandwidth. The Rotman lens and antenna arrays are fabricated on the top layer of a multilayer low temperature cofired ceramic substrate. The Rotman lens has been designed based on the presented technique, which has five beam ports, five array ports, four dummy ports, and a footprint as small as 11 mm $\times10.7$ mm at 60 GHz operation frequency. The implemented lens and antenna array exhibits good insertion loss, return loss, and wide bandwidth and shows phase error as small as 0.45° in the worst case scenario.