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.

Blue whale songs provide a measure for characterising worldwide blue whale population structure. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. The nine song types can be divided into those containing only simple tonal components (high latitude North Pacific, North Atlantic and Southern Ocean song types), those comprised of complex pulsed units in addition to the tonal components (Pacific Ocean margin song types from California, Chile and New Zealand), and those which have the greatest complexity of all and the longest cycling times (Indian Ocean song types from Sri Lanka, Fremantle and Diego Garcia). We suggest that temporally stable differences in song provide another characteristic for comparison with genetic and morphological data when defining blue whale populations. Furthermore, as Mellinger and Barlow (2003) recommend, when there is a lack of other data or lack of clarity in other data sets, evidence of distinct differences in songs between areas should be used as a provisional hypothesis about population structure when making management decisions. Worldwide study is needed to better understand the various populations and subspecies within species like the blue whale that have large geographic distributions and have both migrating and resident populations.

Calling blue and fin whales have been tracked using relative travel times and amplitudes from both direct and multipath arrivals to a seafloor array of seismometers. Calls of three fin whales swimming in the same general direction, but several kilometers apart, are believed to represent communication between the whales because of signature differences in call character, an alternating call pattern, and coordination of call and respiration times. Whale call tracks, call patterns, call character, and swimming speeds were examined during periods with and without the presence of noise. Noise sources included airguns, when the whales were subject to sound levels of up to 143 dB P-P (peak-to-peak) re: 1 µPa over the 10 to 60-Hz band, and transits of merchant ships, when the whales received continuous levels up to 106 dB rms re: 1 µPa over the 10 to 60-Hz band (115 dB P-P). Whale responses associated with these noises remain arguable.

Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Island reveal little increase in noise levels in the absence of local ships. Navy reports document ambient noise levels at this site in 1958–1959 and 1963–1964 and a seafloor recorder documents noise during 2005–2006. When noise from local ships was excluded from the 2005–2006 recordings, median sound levels were essentially the same as were observed in 1958 and 1963. Local ship noise, however, was present in 31% of the recordings in 1963 but was present in 89% of the recordings in 2005–2006. Median levels including local ships are 6–9 dB higher than median levels chosen from times when local ship noise was absent. Biological sounds and the sound of wind driven waves controlled ambient noise levels in the absence of local ships. The median noise levels at this site are low for an open water site due to the poor acoustic propagation and low average wind speeds. The quiet nature of this site in the absence of local ships allows correlation of wind speed to wave noise across the 10–220 Hz spectral band of this study.