This paper presents a model of direct delta-sigma receiver (DDSR)and methodology for theoretical transfer function. The theoretical analysis is carried out by modeling the key elements of the DDSR, including the N-path filter, down-conversion mixer, baseband delta sigma modulator and FIRDACs in order to optimize the loop filter coefficients. The contribution of different noise sources and the impact of the nonlinearities are also analyzed. The obtained simulation results show the accuracy of the proposed models and method. This top-down approach allows the designer to determine the key parameters for DDSR in terms of noise contributions,nonlinearity impacts, filtering effects as well as gain distribution and thus enables the optimization of the whole receiver. Although this methodology was applied to the conventional DDSR, but it can be used for any receiver architecture based on DDSR.