Stratix II: Coil circuit

Pin capacitances are listed in the device handbook, simply assume 5-6 pF for most pins.

You can easily see, that it's impossible to achieve a several 100 MHz resonance above a certain coil inductance. But there's no need to have more than one turn with your coil, thus you may be still able to design a coupler with sufficient output level.

You should consider however, that you're effectively operating a RF transmitter with considerable output power (mW range) and that your instrument won't pass EMC tests unless the coupler is completely shielded by a metallic enclosure. Even if you would use a free ISM (industry, science and medical) frequency, the clock signal has to be thoroughly filtered from harmonics.