Hybrid Integrated RF-MEMS Phased Array Antenna at 10GHz

In this paper, a one-dimensional electrically steerable RF-MEMS phased array antenna for operation at 9.5 GHz is demonstrated. The antenna itself is a four by eight patch antenna array realised on low-loss Teflon substrate and the feed network made out of the same substrate is a one-to-four corporate feed network. The phase shifting necessary to steer the main beam of the antenna in the H-plane of the aperture is achieved by four 3 bit RF-MEMS phase shifters, which are integrated in a hybrid fashion between the antenna and the feed network. The paper describes the integration of the different elements in a standalone phased array antenna demonstrator. The design of the 3 bit RF-MEMS phase shifters is presented and validated by very good measurement results. Finally, the measured radiation characteristic of the complete phased array antenna is shown for different switching states of the phase shifters.

I. Introduction

Phased array antennas are pivotal components of millimetre-wave front-ends offering huge opportunities in the field of communication and sensors. Driven by the always increasing need of such devices for emerging millimetre-wave applications like automobile collision avoidance radar, the last decade has seen the development of new antenna concepts and technologies, making the realisation of electrically steerable antennas possible. Rotman lenses [1], active T/R modules [2], PIN diode or transistor based phase shifters have been implemented and some front-ends using these technologies are produced in large series and regularly commercialised. However, in many cases these realisations are handicapped by high fabrication costs or unacceptably high insertion loss. To improve on this situation, some alternative solutions based on ferro-materials or RF-MEMS phase shifters have been developed and demonstrated [3]. Because they implement very low-loss phase shifters and are cost effective to fabricate, RF-MEMS phased antennas are becoming more and more attractive. The different issues dealing with the practical implementation of RF-MEMS technology like reliability and packaging are on their way to be solved and some working RF-MEMS phase shifters have been demonstrated with excellent performance [4]; and even complete RF-MEMS phased array antennas have been demonstrated [5], [6]. Nevertheless, these realisations are often based on a monolithical integration of the phase shifters, and the trend is now to evolve toward the use of RF-MEMS phase shifters as stand-alone chips, packaged and diced, that could be used as hybrid integrated components in a larger system. In this paper, a four by eight one-dimensional electrically steerable phased array antenna at 9.5GHz is demonstrated. The antenna uses RF-MEMS phase shifters integrated in a hybrid fashion between the feed network and the antenna, both realised on soft Teflon substrate. In the following sections, the design of the different elements including the feed network, the antenna and the phase shifters as well as the way they are integrated in a stand-alone demonstrator is presented. Finally, the completely integrated phased array antenna is assessed by measurement.