Van Dokas

On the power handling capability of high temperature superconductive filters

This paper presents high power test results for high temperature superconductor (HTS) filters having six different configurations. The results demonstrate the possibility of realizing narrow band HTS filters that are capable of handling 30-50 W at 77 K. The paper also introduces a procedure for comparing the power handling capability of HTS filters with different RF characteristics. Issues related to thermal design of high power HTS filters are discussed in detail.

Design considerations of superconductive input multiplexers for satellite applications

This paper describes the evolution and development of low power superconductive filters and multiplexers for satellite applications under the HTSSE-II program. Experimental results and tradeoffs are presented for thin film and dielectric loaded HTS multiplexer configurations, leading to the development and implementation of a fully integrated four-channel C-band HTS input multiplexer. Measured data shows performance comparable to conventional technology and promise of large reduction in mass and volume of such equipment. The multiplexer is scheduled to fly as part of the HTSSE-II package on the ARGOS satellite in 1996.

Quasi dual-mode resonators

The paper discusses the concept of using two single-mode resonators to construct a quasi dual-mode resonator that has all the features of traditional dual-mode resonators. Two novel filter structures are presented in this paper that employs this concept; one employs planar type resonators and the other employs dielectric resonators. A new configuration for a single mode dielectric resonator is also proposed in this paper. The use of such type of resonators makes it possible to construct dielectric resonator filters that are much smaller in size than conventional TE/sub 01/ single mode resonators. Measured and theoretical results are presented to verify the concepts proposed in this paper.

Predistortion technique for cross-coupled filters and its application to satellite communication systems

This paper presents a novel adaptive predistortion technique for general cross-coupled microwave/RF filters with improved insertion loss and group-delay equalization. The method enables many potential applications of an almost abandoned technique, and permits a lower Q implementation technology to emulate the performance of a higher Q filter. 10-4-4 filters were built and tested at C- and Ku-band to verify the validity of the new method. The impact to satellite communication channels was also analyzed. Another novel concept of over-predistortion was proposed and evaluated and should lead to significant improvement for applications such as satellite transponder input multiplexers, where insertion loss can be traded off for in-band flatness, mass, volume, and even overall system performance.

Feasibility and commercial viability issues for high-power output multiplexers for space applications

The objective of this paper is to address the issues related to the commercial viability of employing high-power high-temperature superconductor (HTS) filters and multiplexers for communication satellites. Experimental results are presented for fully integrated contiguous HTS manifold-coupled output multiplexers. Both hybrid dielectric-resonator HTS filters as well as planar HTS filters are used to construct these multiplexers. The paper provides a detailed analysis of the cooling load of HTS high-power multiplexers, and describes how it varies with the achievable filter Q and the type of I/O RF cables. It also demonstrates the role that the I/O RF cables play in determining the cooling load of HTS subsystems.

A C-band superconductive input multiplexer for communication satellites

The paper demonstrates the feasibility of building a fully integrated C-band 4-channel superconductive multiplexer employing 8-pole hybrid dielectric/HTS thin film filters. Experimental results are presented for 4-pole and 8-pole externally-equalized superconductive filters having 1% bandwidth. The measured data for the integrated multiplexer clearly indicates that C-band superconductive multiplexers are approaching the performance requirements of typical satellite systems and have the potential of large reduction in mass and volume over conventional technologies. The critical design considerations of such type of superconductive multiplexers are discussed. >

Design of hybrid-coupled multiplexers and diplexers using asymmetrical superconducting filters

The feasibility of building high-temperature superconducting (HTS) hybrid-coupled multiplexers and diplexers employing filters with asymmetrical frequency characteristics is demonstrated. The design of pseudo-interdigital filters with improved skirt performance is discussed. Experimental and theoretical results are presented for superconducting filters, hybrids, and a fully integrated C-band diplexer. It is noted that the extra coupling which exists between nonadjacent resonators in pseudo-interdigital filters may be used to improve the rejection performance on the high-frequency skirt. Filters with such rejection performance are suitable for use in the design of HTS hybrid-coupled multiplexers and diplexers. The experimental results reported here for superconducting filters, hybrids and the fully integrated C-band diplexer demonstrate the possibility of building such components with no tuning elements.<<ETX>>

Modified conductor loaded cavity resonator with improved spurious performance

The paper introduces a new resonator configuration to realize conductor-loaded cavity filters with improved spurious performance. Theoretical results are presented for the field distribution and resonant frequencies of the proposed structure. The results show that shaping the metal resonator inside the cavity can considerably improve its spurious performance. Experimental results are presented to verify the concept presented in this paper.

Quasi-dual-mode resonators

This paper discusses the concept of using two single-mode resonators to construct a quasi-dual-mode resonator that has all the features of traditional dual-mode resonators. Two novel filter structures are presented in this paper that employ this concept; one employs planar-type resonators and the other employs dielectric resonators. A new configuration for a single-mode dielectric resonator is also proposed in this paper, The use of such a type of resonator makes it possible to construct dielectric-resonator filters that are much smaller in size than conventional TE/sub 01/ single-mode resonators. Measured results are presented for four filters along with theoretical results to verify the novel concepts proposed in this paper.

Symmetrical realization for predistorted microwave filters

This paper presents a symmetric realization for a predistorted bandpass filter using a general cross-coupled resonator structure. The new method enables much simpler conversion from an existing filter design without predistortion. Hence both design and tuning efforts are reduced. A 10-4-4 dielectric resonator filter was built to verify the validity of the new method. The filter, coupled with an input circulator and output isolator was tested over temperature to validate the suitability for practical applications such as satellite transponder input multiplexers. Index Terms — Predistortion, bandpass filters, filter synthesis, microwave filter.