matching affects on resonant frequency

Does changing the matching affects the resonant frequency. Suppose if i am using a circuit which is resonating at 3 Ghz. Now i want to use this @2.45 Ghz. So now if i design a matching network to match this to a 50 ohm line @2.45 ghz. We will see more power @2.45 GHz. but will this change the resonant frequency too.

A resonator has an unloaded resonant frequency and Q factor. Whenever you attach anything to the resonator, even to measure it, you load the resonator, resulting in a shift in the resonant frequency and Q factor. To get the most effecient system, you should try to design around the natural unloaded f0 to get the highest Q, but it is possible to design otherwise. Prof. Darko Kajfez has some good resources under the name "Q Factor Measurement" that are very helpful for understanding this.