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Design >> Analog Design >> Active Filter Design
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Message started by aaron_do on Feb 11^th, 2007, 11:57pm

Title: Active Filter Design
Post by aaron_do on Feb 11^th, 2007, 11:57pm

Hi all,

i'm trying to design an active filter operating at 2 MHz, and I found that for about 300 uA, my gain IRN and IIP3 are 8 dB, 127 nV/sqrtHz and 0.5 V (about +4 dBm). This is a 3rd Order BPF.

I've looked at some publications, like: "A Fully integrated 2.4-GHz IEEE 802.15.4 Compliant Transceiver for ZigBeeTM Applications". Its in JSSC Vol. 41, no.12, dec 2006.

I noticed that some works have amazing IIP3 and NF. The one mentioned has NF of 5.7 dB (diff LNA uses only 2.4 mA and I suspect that using that topology, the LNA NF must be >4 dB) and IIP3 of -16 dBm (given that the LNA had a gain of 33 dB, the CSF must have IIP3 better than 14 dBm). while using 5.6 mA for the whole front end including the analog baseband. I just can't figure out how they got it given the channel select filter's requirements. Anyone have any ideas? I think it has something to do with the fact that they used a limiter instead of VGA.

thanks,
Aaron