System for highly linear phase modulation

摘要

System for highly linear phase modulation. Apparatus is provided for linear phase modulation utilizing a phase-locked loop (PLL). The apparatus includes a PLL utilizing fractional N synthesis to realize a non-integer divide value. A two-port voltage-controlled oscillator includes a first port controlled by the phase-locked loop and a second port accessed for direct modulation. A second input to the fractional-N phase-locked loop is provided to remove the modulation introduced at the second port. Lastly, a calibration loop is provided wherein a frequency offset applied at the second port is adjusted until it cancels the effects of a known frequency offset introduced to the fractional-N phase-locked loop.