The use of silicon-germanium transistors in microstrip voltage-controlled oscillator design

Current X-band (8–12GHz) oscillators are designed around bipolar discrete silicon transistors. These transistors have currently become obsolete. Suppliers have ceased making the high frequency transistor in favor of a lower frequency transistor in order to obtain the more lucrative cell phone market. New suppliers or new designs are needed to continue production of X-band oscillators. Alternatively, GaAs FET devices are suitable for microwave and millimeter oscillator designs but have inferior phase noise performance compared to silicon bipolars and are not considered a substitute. It is thought that a new transistor, the silicon germanium (SiGe) transistor, which was just made available in recent years, can be used. Conventional silicon-only transistors can handle frequencies from 10–20GHz, while the SiGe transistor can handle up to 50GHz.; During the course of this thesis, a X-band VCO (Voltage Controlled Oscillators) will be designed around this new SiGe Transistor. Existing results for conventional plain silicon VCOs will be compared to test results obtained with the new SiGe transistor. The results of this thesis will determine if the new SiGe transistors can be used in future high frequency oscillator designs.