ABSTRACT
Wavelengths in air at microwave and millimeter-wave frequencies range from 1m at 300MHz to 1mm at
300GHz and are comparable to the physical dimensions of fabricated electrical components. For this reason
circuit components commonly used at lower frequencies, such as resistors, capacitors, and inductors, are not
readily available above 10GHz. The available microwave frequency lumped elements have dimensions of
around 1mm. The relationship between the wavelength and physical dimensions enables new classes of
distributed components to be constructed that have no analogy at lower frequencies. Components are realized
by disturbing the field structure on a transmission line, resulting in energy storage and thus reactive effects.
Electric (E) field disturbances have a capacitive effect and the magnetic (H) field disturbances appear
inductive. Microwave components are fabricated in waveguide, coaxial lines, and strip lines. The majority of
circuits are constructed using strip lines as the cost is relatively low and they are highly reproducible due to
the photolithographic techniques used. Fabrication of waveguide components requires precision machining
but they can tolerate higher power levels and are more easily realized at millimeter-wave frequencies
(30 to 300GHz) than either coaxial or microstrip components.
