Noise reduction for mobile phones
06 January 2009
STMicroelectronics’ miniature filters cut noise on music-enabled phones.
Apparently, more than 75% of mobile handsets will ship with MP3 capability in 2010, making audio performance a focus area for designers. New handset designs will demand improvements in noise reduction that can be enabled by the new EMIF02-SPK02F2 filter from STMicroelectronics.
The EMIF02-SPK02F2 occupies 0.89mm x 1.26mm of handset pc-board space, and provides filtering for the handset’s built-in speaker or a stereo headset output. A single EMIF02-SPK02F2 can also be connected to the microphone input to isolate the handset from external sources of noise, such as other mobile phones.
As a member of ST’s audio IPAD family, which delivers miniaturised filters for handheld and mobile-audio applications, the EMIF02-SPK02F2 also delivers performance benefits in notebook and desktop PCs, car audio systems and personal MP3 players.
According to the manufacturer, filters built using discrete components are difficult to design for tri-band handsets and typically occupy around 72% more board space than the EMIF02-SPK02F2. Alternatively, single-chip passive filters can be as much as 11% larger, and also permit several times more noise at the frequencies used in standards such as GSM. These include signals at 900MHz and 1800MHz, which can be picked up by the handset’s audio circuitry, creating audible interference; ‘TDMA’ noise.
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