Ceramic Loop antenna front end-Match tuning-Filtering

[electronx]

I came across such a schematic. I can understand the match tuning CL structure just before the antenna. However, the previous pi structure confused me. What does this pi filter do, why a cascaded system?

[ftg]

The C5-L1-C6 Pi-pad could be for matching the RF output pin to 50ohms, so that the filter sees proper 50ohms and preforms as it is supposed to.

[SeanB]

Filters are there because the SAW filter will have responses at harmonics of the input, so the input side filter is there to reduce them to a level where the output, again after filtering, will not exceed allowed spurious emission levels. that 2.85GHz output from the IC is going to not be a perfect sine wave, it will probably have a lot of harmonics not filtered on the chip, so you need the filter to attenuate them, and also to reduce any RF reflections back to the output stage of the IC as well, to allow for highest power output, along with limiting the out of band energy when it is switched to receive the signal from other endpoints. filter each side to reduce harmonic energy that say comes from a 5GHz AP or device close by, that would otherwise saturate the receiver signal wise.

[ftg]

The LFL182G45TC1A108 seems to be an LTCC low pass filter with 50ohm port impedances.
No idea what the RF IC is, so cannot really comment on it's RF port's output impedance, but it often ain't 50ohms in most cheap stuff.
Annoyingly muRata does not seem to have any data for the expected attenuation.
Outside of these two lines:
27.0 dB min. at 4800.00~5000.00 MHz
25.0 dB min. at 7200.00~7500.00 MHz
Which naturally only apply if both ports are 50ohms.
https://www.murata.com/en-us/products/productdetail?partno=LFL182G45TC1A108