Monolithically integrated SD frequency synthesiser with distributed reference spurs

Monolithically integrated fractional-N frequency synthesiser controlled by the dual edge triggered (DET) MASH SigmaDelta modulator is presented. A DET modulator offers two advantages over the single edge triggered implementation: (1) it reduces the modulator´s area by 15-20% and (2) it distributes switching noise power in such a manner that it does not degrade the first reference spur of a synthesiser but shifts the glitch energy to higher multiples of the reference frequency. A benefit of such a reference spur power distribution is demonstrated. A fabricated 11 GHz fully integrated sigma delta phase-locked loop (PLL) with the DET modulator exhibits the first reference spur below 66 dBc over the whole locking range.