Impedance matching: L-network or micro strips?
I think you are misinterpreting the example schematic.  The circuit formed by L1 and R4 is not a matching circuit - it is instead a bias tee/filter used to get the DC voltage from VCC_RF onto the RF line (this voltage is used to power an active GPS antenna).

You can sanity check this by looking at the inductor value.  Notice that jwL = j*2*pi*1.6e9*27e-6 gives ~270j kOhm impedance at GPS frequencies - matching components will typically have much lower impedances, and would be more likely to have values in the nH.  This inductor is intended to completely block RF, not to match it.

There is no mention in the datasheet of what the impedance of the RF_IN pin is.  Typically, if an IC requires an external matching circuit, it will list an input impedance (which may take the form of "R+jX ohms", or "R ohms || ?pf").  Since no input impedance is listed, if you tried to match the chip, what would you match to?

The correct answer is that the chip itself has a 50 ohm RF_IN pin, and should be connected to a 50 ohm microstrip trace, and then to a 50 ohm SMA connector.  No other matching circuit is required.  If using an active antenna, you DO need R4 and L1, but not for matching.



When using a passive antenna only, R4 and L1 are NOT required, as seen in the following figure from the Hardware Integration Guide