Selective filters techn. centered at 868.3GHz(ETSI), with -10dB band about 400KHz.

[svia]

Hello everybody

I need to filter a RF signal to comply with the ETSI 300-220, for the band 868-868.6MHz.

At this limits of the band I need an attenuation about 20dB, and a band pass of -3dB 400KHz.

Therfore, I need a very selective filter.

I looked for SAW filters, but I'm not finding anything with so small band.
Any ideas about which filter technology could be the first, or any manufacturer?

I'd appreciate any help.

 

[FvM]

Keeping the spectral mask around the carrier frequency isn't a matter of filtering, normally. It's about using appropriate modulation and avoiding spurious frequencies, e.g. know how to design a transmitter PLL. The RF chips from major vendors are able to keep the ETSI regulations, if used correctly (not considering silicon bugs, that reveal from time to time).

Exceeding the spectral mask by a bad modulation method and bending it into shape with a filter is definitely the wrong way. Filters are mostly required for harmonic filtering, but standard LC filters are perfect for this purpose. They also offer impedance matching for free.

 

[svia]

Thank you for you answer. We use a commercial transceiver, that fullfills the mask, but for our application, more power was needed, so it was needed to use a power amplifier at the output, to have the desired range. Using the PA, we don't match the ETSI limits, which stand that for 868 and 868.6MHz it should be measured -30dB less, with RWB=1KHz.
We measure: -10dBm, we have think to filter in order to achieve the ETSI limits.

 

[FvM]

O.K., that sounds reasonable, because transceiver or chip designers possibly don't provide much margin below the ETSI mask. Did you blew up 10 mW to 500? That may be difficult. You'll also loose possibly half of the precious power to the filter. Presently I'm not aware of suitable filters. I would rather try to understand the nature of the mask violation and defeat it. If the effort isn't reasonable, use a different transceiver.