## 1 Introduction  
Radiating pattern reconfigurable antennas for the design of high-capacity systems have obtained increasing popularity, owing to their attractive advantages, such as compact structure and high efficiency. Pattern reconfigurable antenna could change the maximum radiating direction while maintaining unchanged operating frequencies and other performances. To date, many reconfigurable antennas have been proposed by using PIN diodes [1], copper strip [2], and other means. However, compared with other reconfigurable technologies, RF micro-electromechanical systems (RF MEMS) technology has many superiorities over others, such as small size, high quality factors, and high linearity [3]. RF MEMS switches have been used broadly in reconfigurable antennas in recent years [4; 5; 6; 7; 8; 9], but most of those antennas work in low frequencies and have no process consistence (i.e., RF MEMS switches were mounted in circuits after the antenna was manufactured). When the operating frequency rises, the dielectric loss increases, and the transmission coefficient is more sensitive to the variations of the dielectric thickness and dielectric constant. Moreover, the size of RF MEMS switches and operating wavelengths have the same order of magnitude, and the RF MEMS switches will introduce some parasitic capacitances. The challenges of designing high frequency RF MEMS antennas as compared to low frequency antennas are the radiation efficiency, the transmission characteristics, and the robustness of overall antenna. There are many advantages of Ka-band over lower frequency, such as wide bandwidth, less interference, compact device structure, etc. Compared with lower frequency antennas (such as C-band or X-band antennas), Ka-band antennas have powerful data throughput capacity and the advantage of compact structure. These antennas can be applied to the 5 th-generation (5G) mobile communication and satellite communication system.  
We have done some research in reconfigurable antennas [10; 11] and have fabricated several kinds of reconfigurable antennas in the same batch. Those antennas all have different structure configuration and size, and two of them can be found in references [10; 11]. However, [10] only presents the structure configuration and measurement results, and [11] is only a simulation. Little work has been done on the principles of the proposed reconfigurable antenna and the design details of the proposed RF MEMS switch, such as the actuating voltage, pull in time, and fabrication process. This paper gives details on the design, analysis, and verification of a Ka-band pattern reconfigurable patch antenna. In addition, the principles of the proposed reconfigurable antenna, the research of relationship between resonant frequency and RF MEMS switch structure configuration, the actuating voltage, the pull in time, and the fabrication process of the proposed RF MEMS switch are included.  
In this paper, a pattern reconfigurable antenna operating at 35 GHz is presented. By changing the mode of the RF MEMS switches, the antenna is capable of switching among four operating modes and obtaining three operating states (because two of them are at the same angle, i.e., 0\({}^{\circ}\)). By changing the connections between the main and assistant patch radiator, the beams can be steered in three different directions in the _yoz_ plane (\(\phi=90^{\circ}\)).  
The article is organized as follows. Section 2 illustrates the designs of the antenna and RF MEMS switches; Section 3 describes the theory analysis and operation mechanism of the pattern property of the proposed antenna; Section 4 provides the results and discussion; Section 5 summarizes and concludes this study.