Single-IF DECT receiver architecture using a quadrature sub-sampling band-pass Sigma-Delta modulator

The superheterodyne receiver architecture where there are multiple IF stages is still very common. This is because the multiple stages allows for increasing narrow-band filtering at each stage with the final goal of being able to select the desired RF channel (removing sufficiently adjacent channel, alternate channel and any other spurious interference). The mixing process at each stage also provides rejection as it mixes spurious inteferers that do not fall in the RF and IF frequency and image frequency bands away from the following stages. The cost to the receiver however is an increase in comnplexity. Thus there has been considerable research into the design of homodyne (zero-IF) and single-IF stage receivers as better filters become available.;A single-IF receiver architecture complaint to the DECT standard is described here. It takes advantage of the low-power transmission of this cordless system coupled with the TDMA scheme that is used as both these characteristics reduce the linearity requirements of the receiver and also reduce the maximum signal strength to be received by the receiver. This makes the filtering requirements of spurious interferers and the intermodulation products produced less stringent making it more suitable for a single-IF architecture with existing filter technology. The architecture also makes use of the high sampling rate of Sigma-Delta analog-digital converter to down convert the signal from the IF stage to base-band by applying quadrature sub-sampling techniques. The description includes an analysis of the overall system requirements, the system design of the receiver, the design and simulation of the band-pass Sigma-Delta analog-to-digital converter and the design of front-end radio frequency circuits.