Low Phase Noise Synthesizer for Millimetre Wave Digital Radios

The aim of this paper is to present a suitable architecture of a microwave synthesizer with an opportune operating frequency range in order to obtain radio link systems from 6 to 60 GHz with modulation schemes more and more complex satisfying the continuous market requirement of spectrum occupancy reduction. A good microwave source synthesizer should provide an extremely low phase noise at low frequency offset from the carrier and high stability versus temperature variations. A wider operating frequency bandwidth is also needed and particularly, for low bit rate applications, fine frequency steps is the only one solution able to guarantee the several canalizations requested. Furthermore the phase locked loop bandwidth, which determines the microwave source response speed, must be as wide as possible in order to make negligible the frequency jumps effect due to mechanical shocks within the oscillator housing. In this way, the whole radio system shows very good BER performance due to the negligible short-term instabilities. All the aforesaid features must be the peculiarity of this microwave source, with, in addition, very low cost, using standard FR4 substrate and SMT technology, low circuitry complexity, high hardware minimization and high reliability.