Design of a Bandpass Filter with an Absorptive Stopband for Multifeed Antenna Systems

Abstract

This paper presents a filtering solution for enhanced multiband and multisource antenna systems used for space applications. Covering a large surface of the Earth necessitates numerous apertures closely spaced over a reflector antenna. Since these multi-feed systems generally employ multiple bands and multiple polarizations, these architectures induce significant coupling and consequently influence the effectiveness of the solution. The approach of signal retransmission with a controlled phase is proven to be efficient despite a delay concern. On the other hand, as shown in this paper, dissipating the reflected signal can also provide an adequate solution. For this second approach, we have synthesized a two-band filter, one passing the signal, the other absorbing it. This behaviour fits the desired antenna performance and improves the isolation between the two channels. We have designed such a filter and a comparison was made between the two approaches to investigate and derive the efficiency and benefit of each solution. A resized version of the microwave filter with dual behaviour has been manufactured and characterized for experimental verification.