This paper provides a qualitative comparison of three frequency synthesizer schemes implemented in 130 nm CMOS technology, with the aim to select the best architecture to use given the application specs. The presented architectures can generate carrier frequency bands from a maximum frequency down to any lower frequency. All systems are designed based on 130 nm CMOS technology and can reach frequencies up to 25 GHz. We show that the single switched capacitors voltage controlled oscillator (S-VCO) architecture is the best choice for frequencies below 6 GHz, and multiple core VCOs (Multi-VCO) synthesizers show the best performances for frequencies above 16 GHz. On the other hand, the synthesizer equipped with a single side band mixer (SSB-m) is the choice for applications requiring frequencies between 6 GHz and 16 GHz.