Abstract:
RF bandpass filters being commonly used in wireless communication systems are increasingly being implemented utilizing actively simulated inductors. Implementation of bandpass filters based on active inductors holds a number of alluring characteristics including a high passband center frequency, a large center frequency tuning range, a large and tunable quality factor subsequently a low insertion loss, and a low silicon consumption. The use of active inductors in RF bandpass filters, however, is faced to several tough challenges including poor noise performance, a limited dynamic range, and a high level of power consumption. For the telecommunication applications in the UHF band (300 MHz - 3 GHz), frequency tuning range of the active inductor based bandpass filter implementations in the literature is generally between 1-3 GHz without the usage of external capacitances. LC tank circuits are commonly formed with off-chip capacitances while circuit operation requires below 1 GHz. The desired capacitance value may not be available for achieving an operation in specific frequency and on-chip varactors are used for fine tuning of the inductance value. A large area is required for implementing an onchip varactor which needs to succeed a wide range capacitance tuning. If so, a control voltage is a must for determination of the capacitance value which is a potential burden for the bias requirements of the overall circuitry. The work done in this M.S. thesis is the design of a new wide tunable bandpass filter based on an introduced CMOS active inductor topology which consists of a back-to-back connected transistor pair together with one single transistor utilized for inductance tuning. This gyrator-C network achieves a wide tuning range with introducing an idea for the removal of the use of off-chip and on-chip capacitances by realizing inductance boosting and decaying technique for the selection of the desired frequency. Implemented in TSMC 0.18μm process, the wide tunable active inductor based bandpass filter offers a tuning range between 327 MHz and 2 GHz with a quality factor above 40.
