arrays of tapered-slot or finline transitions have proved useful in
the design of compact spatial power combiners. The tapered
transitions rest over a notched opening in the metal cararier to which
the MMIC are attached, and couple energy to and from a rectangular
waveguide aperture to the MMIC amplifiers.
A design procedure is established for tapered finline arrays,
providing a broadband impedance match to a target load over the
waveguide band. The procedure is based on an extension of the
Klopfenstein optimal taper design to a non-TEM waveguiding structures,
and employs the Spectral Domain Method to the computation of
propagation constants in the array structure. The waveguide structure
is modeled as shown in bottom figure, with boundary conditions applied
to reduce the complexity.
The method has been experimentally verified for a small X-band
array. Data is also presented which shows that insertion loss in
the finline arrays is independent of the number of array elements,
assuming the designs are optimized for the desired return loss
characteristics in each case.