Help with analysis of a signal that generates high frequency
Those two parallel capacitors C2 and C3 aren't for frequency tuning, they're for antenna matching and possibly harmonic suppression.  Most likely the reason they didn't use a single 10pF cap is that at 700MHz the single cap would have been close to resonance; it seems odd that C1 at 15pF isn't a concern, but they may be different packages, which will affect the resonance profoundly.  It's also possible that it was split for redundancy, the capacitors are separated by a carefully calculated length of transmission line, or it's a commonly used value on the board and they wanted to avoid loading another reel on the pick&amp;place machine.