Patent ID: 6931243
Filing Date: 2005-08-16
Classification: H03L

Abstract:
1. A multi-loop frequency synthesizer, comprising: an input terminal for receiving an input reference signal having a frequency f a fine tune phase locked loop coupled to the input terminal and driven by the input reference signal to output a fine tune signal having a frequency f a coarse tune phase locked loop coupled to the input terminal and driven by the input reference signal to output a coarse tune signal having a frequency f a translation phase locked loop having a unity multiplication factor driven by the fine tune signal; comprising a Gilbert cell double balanced mixer coupled between the coarse tune and the translation phase locked loops, the Gilbert cell mixer combining the coarse tune signal and a divided down output signal of the fine tune phase locked loop and coupling the mixed signal into the translation phase locked loop to generate an output signal with a frequency which is proportional to the linear sum of the coarse tune signal and the fine tune signal, the low multiplication factor and high bandwidth of the coarse tune loop and the unity multiplication factor of the translation loop reducing the phase noise of the frequency synthesizer.