UC Santa Cruz

THz integrated circuits are now possible with improved processes that have increased fτ and fmax. The increased fτ and fmax enable the use of metamaterials as a design element due to their decreased size at higher frequency. Novel on-chip resonators that are crucial for imaging, communications, and other applications are possible. Here we investigate issues relevant to the design of THz oscillators in general and the use of metamaterials as resonators in these circuits.

A number of design challenges are investigated. Above approximately 200 GHz higher-order propagating modes are possible for transmission lines. This introduces extra power loss which can prevent the circuits from working as simulated because current circuit simulators do not include the modal effects.

This dissertation discusses why the modal effects occur, how they can be analyzed, and what design steps can be used to avoid it. A new technique, Modal Aggregation, is presented to allow circuit simulation when modes exist. The mathematics of the technique and examples of how to use it are developed. This technique can be implemented using almost any circuit simulator along with a computer aided mathematics tool.

Metamaterials from a circuits’ perspective are RLC resonant circuits and as such single cells are suitable for use as resonators. For the first time they are analyzed and synthesized as RLC circuits easing compatibility with circuit simulation tools. Single-negative metamaterials are modeled with a single RLC series or parallel circuit in series or parallel with the ports. A double-negative metamaterial is modeled as three RLC series or parallel circuits in either a π or T arrangement.

Various candidate THz resonators are analyzed, simulated and compared to provide design insight and guidance for the selection of resonator type. The results are given at 300 GHz and 1 THz. The resonators include those based on microstrip, stripline, grounded coplanar waveguide transmission lines, rectangular and circular waveguides, spiral inductors, and metamaterials.

Two THz oscillator designs are presented that use a metamaterial as the resonant element. The design methodology, process, and simulation techniques are discussed. Finally, the simulated results are shown.