Undefined part of CSR8645 chip
It's a bandpass filter. The crossed out waves tell you that frequencies above and below the passband are rejected. The legend says the passband is centred on 2.45GHz. 

It's not part of the chip, but an external component.

The schematic tells you nothing more about it, such as bandwidth, insertion loss, stopband attenuation, etc. Hopefully the text has more information; I don't.