Using Pulse W3006 Dualband Wifi Antenna with a CPW-G Trace and Single RF_Out on MC
There is no reason why the chip and the antenna can't operate at both frequencies, it's just that the matching network becomes more complex as now you have two frequencies where you want a low insertion loss as opposed to just one. The advantage here is that the two frequencies are multiples of each other so the network may be a bit simpler. An antenna can be designed to work at more than one frequency (Log Periodic Antennas can cover an order of magnitude or more). Transmission lines aren't that picky about what frequency you send down them, a higher frequency will have more of a phase shift but that's it. The only time the length is a issue is when either you have several signals and they all need to arrive at the same time or when your matching network is made out of sections of different transmission lines. If using a discrete matching network, you're probably going to need more parts than you would have needed for a single operation frequency.