Compact Coaxial Filters for BTS Applications
A new class of coaxial cavity filters with low-profile suitable for base transceiver station applications is proposed. The benefits of the technology are volume reduction, high performance, and superior spurious-free response. An equivalent lumped element circuit allows for a fast and efficient initial design of the resonators. Full-wave optimization is required to produce the final configuration of the filters. Experimental results demonstrate the high performance of the proposed filters. The electrical length of the experimental resonators is as low as  $\lambda _{0}/16$ . The measured insertion loss of the five-pole filter is 0.92 dB at 722 MHz. Experimental results show a spurious-free response of the order of 7.6 times.
Microwave Bandpass Filters Using Re-Entrant Resonators
Design techniques for microwave bandpass filters using re-entrant resonators are presented. The key feature is that each re-entrant resonator in the filter generates a passband resonance and a finite frequency transmission zero above the passband. Thus, an N th degree filter can have N finite frequency transmission zeros with a simple physical realization. A physically symmetrical five-pole re-entrant bandpass filter prototype with five transmission zeros above the passband was designed and fabricated. Measured results showed good correspondence with theories.
Graphs of polyhedra; polyhedra as graphs
Relations between graph theory and polyhedra are presented in two contexts. In the first, the symbiotic dependence between 3-connected planar graphs and convex polyhedra is described in detail. In the second, a theory of nonconvex polyhedra is based on a graph-theoretic foundation. This approach eliminates the vagueness and inconsistency that pervade much of the literature dealing with polyhedra more general than the convex ones.