A low phase noise C-band frequency synthesizer using a new fractional-N PLL with programmable fractionality

This paper presents a new fractional-N PLL that has an arbitrary denominator of the fractional division ratio as well as an arbitrary numerator and an integer part. This enables a reduction in the phase noise of frequency synthesizers for many applications with various channel-space frequencies. The circuit elements of this fractional-N PLL are fabricated in LSI's that operate up to 6.5 GHz. They have been successfully installed in a C-band frequency synthesizer with a low phase noise MMIC VCO.