Study of an active RC line in the microwave region

Abstract

This thesis is a report on an experimental study done on a new type of microwave device. This device is a monolithic, integrated circuit which uses “lumped” elements to approximate a distributed-parameter active RC line. The active region of this device are IMPATT diodes which are capable of generating negative conductance effects (through transit-time delays of majority carriers) at microwave frequencies. The combined effect of negative conductance and positive real resistance within the device makes it capable of being a microwave amplifier or oscillator. The advantage of this type of device is that it does not have to present a negative impedance to an external signal source (as is the case with parametric amplifiers) to accomplish gain. Due to the nature of its design, it is inherently more “broadbanded” than the parametric amplifier. Also, no external “pump” is needed since the device obtains gain by an entirely different principle. In the following pages a brief description of the basic operating theory of the device will be given. This description will show how the negative conductance effect is generated and how this is incorporated into the design of the final active network. Following this is a detailed discussion of experimental procedure, device characteristics sought, and the results obtained. The results of testing show that this device is capable of functioning as a microwave amplifier. They also show that more work will have to be done in improving the "packaging” of the device. Aside from these "packaging” problems, it appears that this device is the key to a new area of microwave semiconductor devices.