Low-IF Receiver Planning for The DECT System

In this paper, low-IF receiver planning for Digital European Cordless Telephone (DECT) systems operating around 1.9 GHz is described. A low-IF receiver architecture is chosen, since it allows a high degree of integration. Unlike zero-IF receivers, this architecture does not have a DCoffset or self-reception problem. The main features of the DECT system are presented, including the translation from the DECT system specification to RF circuit specification. Analytical expressions are presented for the noise figure (F) and the third order intercept point (IIP3) of a multi-stage two-path system, which are verified by simulation. These calculations are important for the low-IF receiver planning, since it has an in-phase and a quadrature branch. In order to incorporate the A/D-converter in the receiver planning calculations, a formula is derived which translates the Integral Nonlinearity (INL) of an A/D-converter to the IIP3 definition. In addition, the optimum IF frequency and selectivity distribution is considered, taking the A/D-converter requirements into account. A detailed description of receiver planning is given applied to the DECT system but the approach is suitable for other standards as well. Keywords— Receiver planing, DECT, Low-IF architecture, Noise figure (F), Third order intercept point (IIP3), A/D-converter.