What is Spectre and how does it differ from MWO and ADS?

It is a simulator by Cadence.

the spetre is cadence prodcut . the ADS is aglient tools , now it is call RF-DE .
The tools engine is different . the spectre is time domain base , the RF-DE(ADS) is frequency tools .

Hello mitgrace;
You wrote:
Can you explain more? Do you say that the new name of ADS2004 is RF-DE?
Is Spectre an RF time domain simulator? Can you introduce any link/book/paper/article about these subjects?

Hello :

THe ADS2004 is call RF-DE (linux or Unix version) . it can embeded in cadence tools , Analog artist . You can use composer to daw you schemtic and use spectre-RF or RF-DE to simulate you circuit . It is very powerful . In LNA /Mixer (is using inductor load) The simulation time of RD-FE is faster than spectre-RF . We use using two tools to double check the RF-fronted circuit . This is our experiment for RF-IC design .

spectre is more like tr. level tool while ads is more like a behavior tool

Specre/SpectreRF are cadence based simulation tools, it is a good transistor level tools, and well supported by most pdk. ADS is also a good RF tools, the gui of ADS is perfect, and more flexiable than Spectre however the pdk support is not well.