$Sigma Delta$-modulation is a proven method to realize high- and very high-resolution A/D converters. A particularly efficient way to implement such a modulator uses double-sampling where the circuit operates during both clock phases of the master-clock. Hence the sampling frequency is twice the master-clock frequency. Unfortunately, path mismatch between both sampling branches causes a part of the quantisation noise to fold from the Nyquist frequency back in the signal band. Therefore the performance is severely degraded. In this paper we show that the problem is reduced but not eliminated by employing multi-bit quantisation. Next we present an in depth solution for the problem. The approach consists of modifying the quantisation noise transfer function of the overall modulator to have one or several zeros at the Nyquist frequency. This way the effect of noise folding can nearly be eliminated. It is shown that this can be implemented by a simple modification of one of the integrators of the overall modulator circuit. Finally, several design examples of single-bit and multi-bit modulators are discussed.