455khz IF Filter cross

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455khz IF Filter cross

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anthonyruiz
Contributor I

We are currently using the SA606 for our narrow band FM demodulation scheme. The Murata filters recommended in the reference design are end of life. Does NXP know of a suitable replacement for these IF filters?

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LPP
NXP Employee
NXP Employee

You can use filters from other manufacturers with the similar parameters: target i/o impedance 1.5 kOhm, 6dB bandwidth +-15kHz (or different).

Note:
"To achieve optimum linearity of the log signal strength indicator, there must be a 12 dBV insertion loss between the first and second IF stages. If the IF filter or interstage network does not cause 12 dBV insertion loss, a fixed or variable resistor or an L pad for simultaneous loss and impedance matching can be added between the first IF output (IF_AMP_OUT) and the interstage network."

SA58640DK R17||R18 resistors are provided to achieve required attenuation along with the insertion loss of the filter. The values of these resistors should be tuned to reflect insertion loss of a specific filter.

For example:
https://www.transko.com/img/product/filterCeramic_pdf/11%20LTC455.pdf
http://www.luguang.cn/web_en/pro_in.html?parm=1128
http://www.oscilent.com/spec_pages/Filters/ceramic_filters-745.html
http://www.oscilent.com/spec_pages/Filters/ceramic_filters-748.html


Have a great day,
Pavel
NXP TIC

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