For RF simulation Mentor has EldoRF.
This tool enables to handle multitone carrier
and modulated signals thanks to Harmonic Balance
and Envelope techniques, especially dedicated to RF simulation.
The EDA vedors Mentor & Cadence tools are not good for RF circuit design/simulations...
They provide wide range of products for Digital design (ASIC & FPGA) and also the PCB solutions....
Mostly all are Spice variation simulators and not good for high frequency circuit design/simulation as it involves frequency domain elements such as Transmission lines (ustripline, stripline etc) and multitone analysis ...it is good to use Harmonic Balance simulators (HB)...
for RF design very famous EDA tools are from
1. Applied Wave Research Inc., www.appwave.com
Microwave Office or Analog Office
2. Agilent Technologies
ADS or RFDE
3. Ansoft Corporation
Ansoft Designer
By the way what is your exact application & what implimentation your looking for this RF circuit design?
for you information Mentor provides EldoRF since 1999
and this tool is based on Harmonic Balance technique ...
so multitone analysis can be adressed (and frequency dependent elements too).
may be you did confusion between Eldo (pure transient based
simulator) and EldoRF its RF extension ...
I am aware of Mentor EldoRF and Cadence Spectre RF tools for RF applications...
Still these two tools lacks lot of RF measurements and analysis capabilities...
But AWR Microwave Office & Agilent ADS has rich set of capabilities to address all RF applications...
Any way it again depends what kind of circuit analysis/application the designer (eng_mhussein2005) looking...
Alo I have appended below couple of very nice documents on all RF Simulation methods /techniques (somewhat old) available today for your reference....