Superconducting RF front-end filters for cell phone base stations

Abstract

Cellular bands A and B are in the 100s of :MHz frequency range. They are . discontinuous bands requiring sharp skirts - the specialty of superconducting filters. Superconducting filters are therefore ideal in the function of front-end filters on cell phone base stations, serving to reject any unnecessary signals, eliminating intermodulation distortion (IMD). Broader geographical coverage and higher calling capacity per tower are other effects of the superconducting filters compared to their dielectric counterparts. Were a business to sell these filters, the intended customer would be the cell phone company, rather than the base station manufacturer. The filters would have to be cryocooled. However this requirement is no longer a disadvantage, through an increase of cryocooler mean time between failure(MTBF) to more than 500,000 hours, and through a recently overturned patent on fail-safe operation in case of cooler failure. Comparable businesses have typical quarterly losses on the order of 10s of millions of dollars, but do sell products, so a new business should not expect to tum a profit immediately. However, the ability to learn from the experiences of predecessors would serve a new company well. In addition, the possibility of combining two devices onto one chip (filter and Josephson junction) could serve as a new area of growth for an emerging company.