RF-MEMS Opened-Bridge Analysis

1. Example description

In this example RF-MEMS (Micro Electro-Mechanical Switch), realized on a coplanar waveguide is simulated. It is produced on very thin substrate layer.

The working mode of the RF-MEMS may be described by two states: closed (the bridge is down) and opened (the bridge is up), see Fig. 1. In this example the opened bridge mode is considered.

Since the structure is symmetric, a magnetic wall is introduced in order to reduce the computational effort. The closed state of the switch is simulating introducing a dielectric material with high permittivity placed under the bridge. This can be done, because the bridge does not go down completely, i.e. the switch is capacitive in closed working mode.

To calculate the S-parameters, the required number of timesteps is above 100 000. The provided version of the model file defines only 10 000 timesteps (which migth be changed in the I3D model file - block NI). This number of timesteps is satisfactory for good visualization of the fields.

Fig. 1: The RF-MEMS model.

2. TLM model

The RF-MEMS structure, excitation-type and simulation setup are given in the TLM model files I3D.Open.

The structure is excited with a Gaussian signal. The excitation is modeled by Templete (see documentation) which excites the field distribution of the fundamental mode. Absorbing boundary conditions are used at the boundaries of the simulation domain.

Fig. 2: The model of the simulated structure.

3. Simulation Results

Fig. 3: Voltage signals computed at four different ports.

Fig. 4: The |S21| [dB] and |S11| [dB].

Fig. 5: A snapshot of the field distribution over the RF-MEMS.