This thesis is composed of three parts, which deal with some of contemporary issues in monolithic microwave integrated circuit. Firstly, the main body of this thesis is on two tunable active inductors with emphasis on low power consumption. Experimental measurement results of our active inductor (based on GaAs MESFET) show that the power consumption of the proposed scheme is about 1/3 of the conventional ones with wider range of tunability and higher Q. The simulation results of our active inductor (based of Si BJT) show that the power consumption is about 1/10 of the conventional ones. Further more, the external bias pins are also reduced. This new tunable active inductor is applied to wideband monolithic tunable oscillator and wide tunable bandpass filter.
In appendix I, we suggest low power, new monolithic, tunable, recursive filters having variable and uniform gain. We change the location of amplifier to achieve high gain in 1st-order recursive filter. We use the cascode amplifier as variable gain amplifier to get the variable and uniform gain. To achieve higher Q and low power consumption, we make also the 2nd-order filter using only one amplifier. In case of 1st-order recursive filter, the measured results are similar to our estimation and show variable, uniform, and high gain. The measured results of 2nd-order filter show that it has higher Q at the same gain. Our recursive filters can be applied to monolithic tunable narrow bandpass filters for low power operation in modern telecommunications.
In appendix II, we present a simple semi-empirical high frequency equivalent circuit model to characterize the coplanar waveguide structure, which consists of relatively thick metal line on very thick polyimide over lossy substrate such as Si BiCMOS wafer. Considering the skin effect, the geometric dependence, and the substrate loss, we derive modified models for the equivalent circuit elements. We verify the validity of our model by comparing it with the experimental measurement. Our model is simple enough not only to be suitable for efficient circuit simulation but also to be useful for process characterization and design.
