# A 12-20 GHz Wideband High-Power SP2T Switch Based on Gap Waveguide Technology
## 1 Introduction  
In recent years, the fast growth of technologies to enhance performance and reduce manufacturing cost has become a challenge in microwave engineering. Microwave switches, which are considered to be key components in many microwave and millimeter-wave circuits and systems, are widely utilized in radar systems, satellite transponders, communication links, microwave measurement equipment, and other systems. The main purposes of microwave switches are to provide redundancy in high-power radar systems and select filter banks, system calibration, and routing signals to different sub-systems [1; 2; 3; 4; 5]. There are many critical parameters that should be considered in designing microwave switches, such as obtaining low input return loss, low insertion loss, and high isolation levels. These also include achieving an acceptable switching time, excellent repeatability, high power handling, and long operating life. There are many articles on microwave switches that have been published recently and indicate that the microwave switch can either be a reflective, absorptive, or transfer switch [1]. In reflective switches, the electromagnetic (EM) wave is supposedly reflected to the input port when the switch is in the off state, whereas, in the absorptive switches, the EM wave must be dissipated. However, in transfer switches, the EM wave is routed to different outputs according to the switch states. Several microwave switches based on various technologies are also reported in the literature, including semiconductor devices such as PIN diodes and FETs [6]. These switches have advantages such as high switching speed, compact size, and low fabrication cost. However, they suffer from high insertion loss, low isolation between switch ports, and low power handling. RF micro-electromechanical systems (RF-MEMS) are also consideredto be good candidates to design microwave switches [7; 8; 9; 10]. The RF-MEMS structures have several advantages and features in both mechanical and solid-state technologies. However, their frequency bandwidth and maximum power handling are limited. Mechanical waveguide switches are attractive and efficient in microwave frequency bands. They provide low insertion loss, good shielding with high isolation levels, and high-power handling capabilities [9; 10; 11]. Despite their excellent microwave performance, their complicated and expensive fabrication process is their main weakness since accurate and high precision technologies are required for manufacturing, especially at high-frequency bands. Gap wave technology has been proposed recently as an alternative solution to waveguide structure fabrication challenges [12; 13; 14]. According to EM theory, a PEC/PMC parallel plate structure has a bandgap when the spacing between two plates is smaller than a quarter wavelength, and this bandgap prevents EM wave propagation. Gap waveguide technology utilizes the bandgap as waveguide sidewalls to confine the EM wave to a particular path. Consequently, different metal layers of the structure do not need good electrical connections, and they can be placed on each other without any contact while EM wave leakage and unwanted radiation are suppressed. As a result, an isolated waveguide structure is obtained. Gap waveguide structures can be fabricated using various low-cost manufacturing technologies such as die sink electrical discharge, multilayer die pressing, electron beam melting, 3D printing, molding, and CNC milling. Therefore, the fabrication of these structures is affordable and cost-effective, particularly at high-frequency ranges. Accordingly, many millimeter-wave devices and applications are presented based on gap waveguide technology, such as planar array antennas [15; 16; 17; 18], filters [19; 20; 21], amplifiers [22], couplers [23; 24; 25], phase shifters [26], and rotary joints [27]. In addition, gap waveguide technology is a great candidate for designing microwave switches, due to its contactless feature. In particular, a gap waveguide microwave switch is reported for Ku-band applications [28].