Low voltage low stress MEMS variable capacitors for RF applications.

摘要

With the current trend of low voltage and/or low power electronic and RF circuits, problems and challenges that face engineers are always arising. MEMS has been used in designing filters, switches, varactors, inductors, and other RF devices. In many cases, MEMS devices are superior to their microelectronics counterparts, but their design and simulation tools are not flourishing as fast.; Researchers paid considerable attention to RF MEMS devices, but tunable matching networks did not receive the same consideration. This thesis treats tunable matching networks extensively and introduces a systematic design approach for their design. The approach is unique in two ways: (1) it incorporates some of the parasitic losses, and (2) provides results with accuracy and speed.; The tunable matching network that was analyzed required two variable capacitors and a variable inductor. High tuning range and low actuation voltage is required. Thus, a MEMS varactor design was introduced. For the first time, a capacitor structure that takes into account residual stress and stress effects was suggested. Additionally, a finite element model using ANSYS was also tackled. Two capacitors were designed which were different only in size (475mum x 475mum, and 205mum x 205mum). Simulation results show that the capacitors required 2.52V and 1.8V to achieve actuation, and provided a TR of 4.9:1 and 4.6:1 respectively. The suggested suspension was compared with other suspension configurations in terms of stress and it was proven that the suggested suspension design possesses the least stress upon deflection.; The model was created and fabricated in MUMPS through the Canadian Microelectronic Corporation. Measurement results show that the required voltages to achieve actuation are 9V and 4.5V, and the TR range measured was 3.4:1 and 3:1 respectively. All the measurements were done at 1 GHz. The resonant frequency was measured to be approximately 4GHz.