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Abstract :
[en] This thesis examines ways to improve the output power of LT GaAs terahertz
photomixer circuits, by focusing on the large impedance mismatch between photoconductor
and antenna which gives rise to loss of a large fraction of power,
which could potentially have been absorbed by the antenna. Impedance matching
is a known problem in the microwave domain, and in this work such approaches
were implemented in the terahertz domain and evaluated using a commercial
numerical simulation tool with measured material properties. ?e aim
was to provide cost effective design suggestions which are easily integrated into
existing single layer technologies. Evaluation of high impedance antennas with
integrated DC-blocking showed improvements ranging from 1.5 to 3 times the
output power compared to the 3.0 µW reference case at 0.85 THz. A quarterwave
transformer with an added shunt capacitance shows a 4 times improvement over
the reference case. Adding a multilayer DC-block structure yields a 5 times improvement.
Corrugated high impedance wire structures were evaluated for suitability
in terms of radiative and transmission properties, in search for improved
matching elements. Furthermore, a mechanically tunable resonant photomixer
has been proposed, which yields significant improvement in output power over
existing tunable broadband photomixers. Finally, a modulation scheme is proposed
for binary ASK-modulation in the gigabit per second range of a terahertz
photomixer, using an off the shelf 10 Gbps output driver.
