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.
Optimization of an Air Filled Compact Re-Entrant Coaxial Resonator for a C-Band Bandpass Filter
This paper proposes an enhanced model for a re-entrant coaxial resonator and analyzes the capacitance behavior between its different sections and the <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor, for which mathematical expressions are derived. This model makes it possible to carry out a geometric optimization to minimize the volume of a compact coaxial resonator. Theoretical conclusions are compared with electromagnetic simulations and an optimized symmetrical six-pole re-entrant coaxial resonator bandpass filter prototype is designed and fabricated to illustrate the optimization.
Synthesis of dual-band filters with parallel-connected networks
We discuss in this work a novel approach to the synthesis of dual-band filters having a parallel-connected topology. The only existing synthesis technique for this class of filters offers a very limited control over the topology of the two constituting filters. The approach we propose allows to control the number of transmission zeros of each filter connected in parallel, making the realization of the overall dual-band filter more convenient from a practical point of view. The solution of the problem is based on the introduction of additional transmission zeros which are obtained by means of an iterative procedure. Two examples illustrate the effectiveness of the proposed approach in case of symmetrical and asymmetrical response of the dual-band filter.