# Davis Advanced RF Technologies Lab

### Welcome to the Davis Advanced RF Technologies (DART) lab

We are a group of researchers with a keen interest in many exciting areas of high frequency electronics. Our research interests include:

• Reconfigurable high frequency devices and components;
• High frequency integrated circuits;
• High frequency communication and radar systems and their application in biomedical, societal, and environmental applications.

Critical to our scientific research efforts is a pursuit of fundamental understanding of the engineering principles of high frequency electronics. A major mission of our work is to formulate and disseminate such understanding through university education as well as community outreach.

### Blog

#### [10 Jun 2018] » High-Efficiency mmW/THz Oscillator Design - 2: Some Historic Perspectives

In 1968, Vehovec documented in his book a method for optimizing the output power of a transistor oscillator circuit. He formulated the problem in terms of the complex voltage gain across the transistor. Shown in the following figure, a transistor oscillator is considered as a combination of an active device and a passive feedback network. The ratio between the voltage at the output and the input port of the active device is defined as the voltage gain. In the steady state, we use phasors to represent the voltages and therefore the voltage gain is complex.

$$A=A_R+jA_I=\frac{V_2}{V_1},$$ where $A_R$ and $A_I$ are the real and imaginary parts of $A$, respectively.