I assume that you are simulating a receiver rather than a transmitter.
If your circuit has a divider, you may want to look at the following solution on Cadence Online Support:
11571722 (COS) Guidelines for simulating frequency dividers in spectreRF
The shooting engine is designed for strongly nonlinear circuits such as ring oscillators and circuits that have frequency dividers. For information on whether to use the Shooting Newton vs the Harmonic Balance engine, see support.cadence.com Solution 11310266: When to use shooting Newton vs. harmonic balance . http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11310266
You will also need to set your tolerances appropriately in order to get accurate results also make sure you set enough harmonics. For circuits with a divider, you should set tstab to 5X the period (after the divider) and set saveinit=yes (so you can verify that your circuit has settled). The number of harmonics chosen for the nonlinear signal should be at least 5X the divide ratio.
If you are using harmonic balance, I recommend looking at
11603066 (COS) How to simulate a combination of a frequency tripler and divider with SpectreRF HB analysis
If you are a newer user to SpectreRF, I strongly encourage reading the following blog posts:
There are also a number of workshops/tutorials (again, if you are a newer user). SpectreRF AppNotes and Tutorials....Still One of our Best Kept Secrets!
Staff Support AE, Global Customer Support
Cadence Design Systems, Inc.