Shrinking filters for analogue cellular

Epcos is now the world's first manufacturer of SAW components to make IF filters with a footprint of only 9 x 5mm for mobile phones to the IS-95 CDMA standard operating in the AMPS band.

Epcos is now the world's first manufacturer of surface acoustic wave (SAW) components to make IF filters with a footprint of only 9 x 5mm for mobile phones to the IS-95 CDMA standard operating in the AMPS band.

A year ago, sizes of 13 x 6.5mm were still common.

CDMA (code division multiple access) is a standard used in North America, Japan and Korea, which currently have the world's fastest growing mobile radio systems.

The miniaturised IF filters can be seen as a technological breakthrough for Epcos in the hotly contested CDMA market and highlight the company's leadership in this segment.

Intermediate frequency filters separate the various bearer channels (of 1.26MHz bandwidth) to provide a filtered signal for conversion to digital code.

They are key components of receivers in CDMA systems in particular.

In addition to the new filters for the AMPS band, Epcos has been producing IF filters measuring only 5 x 5mm for CDMA mobiles in the PCS band for several months.

These products are currently the world's smallest filters for CDMA telephones.

Miniaturised, high-performance IF filters from Epcos are based on innovative designs, with filter characteristics on a par with those of larger filters despite their considerably smaller chip size.

Thanks to the multiband capability of this filter class (currently covering the frequency range from 80 to 200MHz), multistandard terminals for CDMA systems can be implemented for the first time, while the reduced footprint supports the rapidly growing trend toward miniaturisation in the mobile radio market.

Although new analogue telephones are no longer being marketed, most phones support analogue as well as digital standards.

CDMA phones in particular permit wide-area reception, even though digitisation of the infrastructure is still far from complete.

Epcos is currently the only supplier of IF filters for the AMPS band that match the new chipsets.

Although analogue in technology, AMPS is still the only mobile radio system with nationwide network coverage, especially in North and South America.

Specially designed for AMPS chipsets, the Epcos B4864 filter in a 9 x 5mm package operates at a centre frequency of 183.6MHz for selection of AMPS channels of 30kHz bandwidth.

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