Lossy filters for multiradio front-ends. Application to future wireless home-networking communications – EXPRESSO

The research project EXPRESSO aims to design lossy microwave filters for future wireless home-networks.
With the increasing demand of new services, devices for mobile communications and home-networking integrate more and more standards, and therefore in order to maintain signal integrity of the various embedded systems, very narrow band filters using high quality factor (Q) resonators are highly required.
Generally, the design and implementation of such filters require a compromise between, on one hand, the electrical performances (in term of insertion loss, bandwidth, and selectivity), and on the other hand, the cost, weight and volume. Indeed, filter performances depend straightly on resonator Q factor, the higher Q the better performances. However, high Q means also high cost and high volume which are far to be compatible with what mass market devices require.
Consequently, other approaches should be found out for future radio communication systems which aim to exploit efficiently the spectrum resource (operating in more and more narrow bandwidths) and which will require low-cost and ultra-selective filters to this end.

The alternate solution proposed in this project consists in using low-cost technologies required for mass production devices, while compensating the resulting filter insertion losses within the system. This solution, called “lossy filters”, is considered as emerging and is not yet exploited in the context of home-networking.
The idea is to distribute the losses within the filter structure in order to keep the electrical performances (in terms of in-band flatness and rejection steepness) and, since a counterpart is necessary, to increase the absolute level of losses. This approach remains possible if the system is able to compensate for the losses by re-designing the RF front-end architecture in this respect.

The research project EXPRESSO contains 3 main lines:
• The identification of suitable RF architectures for home-networking communication systems that will compensate for the amount of losses inherent to “lossy filters”,
• The development of appropriate method (and tool) for the synthesis of lossy filters within the particular context of low-cost technologies used in wireless home-networks,
• The design and implementation of such filters including dissipative elements within the same drastic constraints.

The research project EXPRESSO is a fundamental research program and is relevant to the topic #4: “components for communication”. The research topics intend to bring out new solutions that will enable to exploit more effectively the frequency spectrum. In the future, such filters, considered as key-components in communication systems, will take a strategic role in the design of electronic equipments including multiple radios. Also, the efficient usage of spectral resources will contribute to the development of new services with better quality.