Help with frequency multiplying
You want a lot of energy at 90MHz, or 11 nanoSeconds period, or 5.5nS half-period.

Get an EXOR, and place 5.5 nanosecond delay in one path. You will have  5.5 nS output pulses. Put a Q of 10 LC on the output.







simulate this circuit &ndash; Schematic created using CircuitLab