Toshiba has developed one-channel and four-channel superconducting filters with the aim of application to 2 GHz-band mobile telephone base stations. In view of a tight frequency supply and demand situation in recent years, adjacent channel interference has become a problem. The newly developed filter realizes more precipitous cut-off characteristics than conventional filters, making possible a sharp reduction in adjacent channel interference. The four-channel filter has a bandwidth of about 20 MHz and reduces interference waves separated from the band edge by only 1.5 MHz by more than 80 dB. The on-channel filter, having bandwidth of about 5 MHz, reduces interference waves separated from the band edge by only 0.5 MHz by more than 60 dB. Toshiba plans to consider application to adjacent channel interference reduction for mobile telephones and other wireless devices.
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