# A 12-20 GHz Wideband High-Power SP2T Switch Based on Gap Waveguide Technology
## 3 Switch Design and Simulation Results  
The proposed microwave switch is an SP2T based on GGW structure. The geometry of the proposed switch is shown in Figure 4. The input and output ports are located in the top layer. The middle layer, which is the switch sliding part, consists of all gap waveguide pins and matching posts. The switch state can be changed by sliding this layer to the left or right. In addition, two holder parts are introduced to the structure to provide mechanical stability to the sliding part, and they have no effect on the EM functionality of the switch. The switch mechanism works as follows: when the switch is in State A, the pole-port (Port 1) is coupled to the first throw-port (Port 2) using two transitions in a back-to-back arrangement. The EM waves are coupled from Port 1 to the GGW using the first transition, and then they are coupled to Port 2 using the second transition. In this state, Port 3 is shorted using a short-ended cavity in which the side walls are the periodic pins. Figure 4: Geometry configuration of the proposed switch. (**a**) Exploded view and top view of (**b**) State A and (**c**) State B.  
Figure 3: Simulated S-parameters of the transition by sweeping the design parameters: (**a**) step height, (**b**) pin height, and (**c**) window width. An inverted copy of the pins and posts is placed beside the first one to form State B as shown in Figure 4c. Due to the gap waveguide concept, the sliding part does not require any connection to the top layer. Consequently, it can slide freely while the wave leakage is totally suppressed by the gap waveguide structure. When the switch is in State B, the pole-port (Port 1) is connected to Port 3, whereas Port 2 is shorted. The simulated S-parameters' results of the switch in states A and B are shown in Figure 5a,b, respectively. The reflection coefficient (S\({}_{11}\)) of the pole-port (Port 1) is less than \(-15\) dB within the operating frequency bandwidth (12-20 GHz), which proves the excellent impedance matching of the switch. The insertion loss (S\({}_{21}\)) of the switch is less than 0.1 dB, and the isolation between ports 1 and 3 (S\({}_{31}\)) is better than 130 dB within the operating frequency bandwidth. The simulated results indicate that wave leakage is extremely low, and that the switch performance is excellent. The reflection coefficient (S\({}_{33}\)) of the shorted port is above \(-0.03\) dB within the frequency bandwidth, which shows that the wave is totally reflected back, and the pins have no wave leakage. These specifications are due to the large bandwidth performance of the groove gap waveguides and the transitions from GGW to WR62. Due to the perfect symmetry of the structure for both States, A and B, the simulation results are the same in both states. The electric field distributions of the switch (by excitation of the pole-port) are also simulated for both states at the center frequency (16 GHz), illustrated in Figure 6. According to the figure, the EM waves are confined in the GGW and the proper coupling from the pole-port to Port 2 or Port 3 is apparent. To evaluate the power handling capacity of the proposed switch, the pole-port is excited by a 1-Watt EM wave power, and the maximum electric field in the structure is observed using a time-domain solver simulation in the CST. Figure 6 shows the electric field distribution in the structure for different states. Since the power is proportional to the square of the electric field intensity [31], the maximum power handling of the switch can be calculated as follows. \[P_{max}=\left(\frac{E_{d}\sqrt{P_{ext}}}{E_{max}}\right)^{2} \tag{1}\]  
where, \(E_{d}\) is the air breakdown, \(E_{max}\) is the maximum electric field intensity inside the switch, and \(P_{ext}\) is the power of the excitation wave. As shown in Figure 6, \(E_{max}\) is equal to 12,489 V/m. Since the air breakdown is \(E_{d}=3\) MV/m and \(P_{ext}=1\) W, the power handling capacity of the switch can reach up to \(P_{max}=57.7\) KW.