Hi,
Input matching can be achived by using an inductively degenerated common-source LNA or by usign a common-gate input stage. In the former, matching is performed by means of an inductor connected to the source of the LNA transistor. This inductor, multipied by the transitor ft gives the 50Ohm matching. An inductor in series with the gate of the input transistor is neede to cancell the imaginary part of the input impedance. Tunning is made by adjusting the transistor ft (current) and finally adjusting the gate inductor (normally external) to make the input matching net resonate. Matching in this case is narrowband, though by using a low Q source inductor, the pass band can be broaden a little.
In the case of a common-gate input stage, 50Ohm matching is achieved by the value 1/Gm, being Gm the transconductance of the input transistor. In this case, tunning is performed by varying the transistor current. Matching in this case is broadband.
In CMOS, you try to use architectures with a minimum number of external componets to try not to have the necessity to have 50Ohm output impedance (high current consumption). Instead, you try to work with architectures suitable for a high level of integration, so matching can be done at higher impedance values, once you have passed the input LNA (the ellement that influences the most the receiver noise).
In some cases where you have no choise than going out your chip, you may addapt the the impedance seen by the driving ellement by means of capacitors and/or inductors (impedance transformers).
I hope to have given to you a quick idea of what you do in CMOS RF.
Regards
Humungus