Is it possible to operate HMC1061 at frequencies beyond 18 GHz. Is it fundamentally not possible or will the device operate with degraded performance.
In the datasheet, I can read :
As the data shows, the -3 dB bandwidth of the composite sampling process is 18 GHz as established by the front-end T/H sampler. Inspection of the 2nd and 3rd order product levels show that the linearity performance of the composite T/H-ADC assembly is actually better than the performance measured for the T/H alone with direct spectrum analyzer measurement of the T/H waveform.
This 18 GHz number is a typical, so you could also get up to 19 GHz at -3 dB, as shown by the first figure in the datasheet page 4. Beyond that, I expect degraded performance.