This dissertation reports, for the first time, on the design and implementation of tunable micromachined bandpass filters in the ultra high frequency (UHF) range that are fully integrated on CMOS-grade (resistivity=10-20 ohm.cm) silicon. Filters, which are designed in the Elliptic and coupled-resonator configuration, are electrostatically tuned using tunable microelectromechanical (MEM) capacitors with laterally movable interdigitated fingers. Tunable filters and high-quality factor (Q) integrated passives are made in silver (Ag), which has the highest conductivity of all materials in nature, to reduce the ohmic loss. The loss of the silicon substrate is eliminated by using micromachining techniques. The combination of the highest-conductivity metal and a low-loss substrate significantly improves the performance of lumped components at radio frequencies (RF), resulting in an insertion loss of 6 dB for a tunable lumped bandpass filter at 1075 MHz with a 3 dB-bandwidth of 63 MHz and tuning range of 123 MHz. The bandpass filters are encapsulated at the wafer level using a low-temperature, thermally released, polymer packaging process. This thesis details the design, fabrication, and measurement results of the filters and provides strategies to improve their performance. The performance of filter components, including the tunable capacitors and inductors, is characterized and compared to the state-of-the-art micromachined passive components. The silver inductors reported in this thesis exhibit the record high Q, and the silver bandpass filters show the minimum insertion loss that has been achieved on a CMOS-grade silicon substrate, to the best of our knowledge. Alternatively, tunable capacitors can be made in the bulk of silicon using a modified version of the high-aspect-ratio polysilicon and single crystal silicon (HARPSS) fabrication technique to obtain a larger capacitance density at the expense of a higher conductive loss. Using this process, a 15 pF two-port tunable capacitor is fabricated and tuned by 240% with the application of 3.5 V to the isolated actuator. Silver inductors can be post integrated with HARPSS tunable capacitors to obtain tunable filters in the very high frequency (VHF) range. The reported bandpass filters can be monolithically integrated with CMOS and have the potential to replace several transmit and receive acoustic filters currently used in cellular phones.

For the new generation wireless communication systems, there is an increasing demand for devices that covers more than one frequency band. This results in a need for wide-band tunable front-ends. The main objective of this study is to use dual band filters in the design of a multi-band front-end. A wide-band low noise amplifier is also required. To accomplish this project, a fixed frequency bandstop filter, a tunable dual-band filter and a wide-band LNA are designed and implemented successfully. The predefined specifications of this front-end include gain, gain flatness, spurious signal rejection, frequency tuning range, noise figure and linearity. Total power dissipation and number of elements are also taken into consideration. Test results of the manufactured front-end are compared with the results of existing single band front-ends. In order to design a good tunable wide-band filter, just tuning its center frequency will not be enough. The noise figure of this dual-band filter will be proportional to its insertion loss if it will be used as a pre-selection filter in front of a LNA. Hence its insertion loss will affect the overall noise figure of the system. If it will be used after the LNA, its linearity will be more important. When a bandpass filter is tuned over wide range of frequencies, its bandwidth varies significantly which leads to a degradation in rejection of the spurious signals. Therefore, there must be a simultaneous control of center frequency, bandwidth and insertion loss while providing enough linearity. In order to accomplish this mission, a filter that has two passbands is designed and implemented. The first passband is tunable between 136MHz and 174MHz while the second one is tunable between 380MHz and 470MHz. Also, the low noise amplifier works properly between 136MHz and 470MHz. As a result, a front-end that covers two bands is obtained.