A variable bandwidth & IF, continuous time ΔΣ modulator for low power low-IF receivers

This paper presents a novel continuous time ΔΣ modulator for multi-mode operation. The design is targeted for low power, low IF multi-mode receivers and could operate on any bandwidth ranging from 0.5MHz to 1.5MHz while using the same architecture. A 3rd order, quadrature bandpass (QBP) modulator is preferred that operates on a single side of the frequency spectrum and hence improves the noise shaping characteristic. Weighted capacitive feedforward (WCFF) method is developed and analyzed to achieve the required bandwidths and IF for multi-mode operation. The achieved SNR values are 68.7/60.6/50.4dB for 0.5/1/1.5MHz bandwidths respectively, while consuming a total average current of 1.8mA from a 1.2V supply. The design is simulated with UMC 0.13μm technology.